Research on Thermal Comfort in Low-Pressure and Hypoxic Environments at High Altitudes: A Bibliometric Analysis Based on CiteSpace

Abstract

High-altitude environments characterized by low air pressure, hypoxia, and strong solar radiation have a significant impact on human thermal comfort; however, existing thermal comfort theories and evaluation models are primarily developed under low-altitude climatic conditions, and their applicability in plateau regions remains limited. With the acceleration of urbanization and the increase in residential, tourism, and occupational activities in high-altitude areas, systematically reviewing the research progress on thermal comfort in such environments is of great practical significance. This study combines systematic literature retrieval and bibliometric analysis, based on the Web of Science Core Collection and China National Knowledge Infrastructure (CNKI) databases, to analyze relevant studies published since 2001. Using CiteSpace, research hotspots, collaboration networks, and evolutionary trends are visualized. The results indicate that current research hotspots mainly focus on physiological responses and thermal adaptation mechanisms under low-pressure and hypoxic conditions, thermal comfort regulation strategies for high-altitude buildings and environments, and the applicability and modification of conventional thermal comfort models. Emerging trends include multi-environmental factor coupling analysis, adaptive model development, region-specific building design approaches, and health-oriented comprehensive evaluation frameworks. The findings provide valuable references for building thermal environment design, regional revision of thermal comfort evaluation standards, and policy-making in high-altitude regions.

1. Introduction

The Qinghai Chronic Mountain Sickness Diagnostic Criteria (CMS) defines areas above 2500 m as plateau environments [1]. With the development of economic construction and the increase in plateau tourism, construction assistance, learning and other activities, the number of people working and living in high-altitude areas continues to increase, and the physical and mental health challenges brought by the plateau environment have become increasingly prominent [2]. Related studies [3,4,5] indicate that the comfortable temperature range in high-altitude areas is lower than that in plains, and the comfortable temperature varies due to thermal adaptation, as well as architectural style and season. In addition, low pressure and low oxygen have a significant impact on the physiological and subjective responses to human thermal comfort [6]. The impact of the plateau environment on the human body can be understood from two different but related levels: one is the thermal perception and thermal comfort issues related to environmental perception, and the other is the direct physiological and health risks caused by extreme climatic conditions. The plateau environment has a greater impact on human health, mainly due to low temperature and hypoxia. Since the plateau environment differs significantly from that of inland plains, sojourners entering high-altitude areas will experience greater thermal stress and changes in oxygen partial pressure compared with local residents who are accustomed to the plateau environment. It is difficult to adapt to the low temperature and hypoxic environment immediately, which will seriously affect the lives and work of sojourners. In low-temperature and hypoxic environments, the immunity of travelers in high-altitude areas will be reduced [7]. If the ambient temperature changes drastically and heat regulation is disordered, the human body is prone to colds and fever, which may in turn induce severe diseases such as high-altitude pulmonary edema [8,9]. In the hypoxic and cold environment of the plateau, the risk of digestive system diseases and cardiovascular diseases increases [10,11]. The special plateau climate and complex man-made adaptations have seriously affected the physical and mental health of the sojourners. Hypobaric and hypoxic environments can cause abnormal mental activity and inattention, leading to reduced work ability [12,13].

The ANSI/ASHRAE Standard 55-2023 [14] defines thermal comfort as a subjective parameter that is influenced not only by quantitative variables, but also by a person’s mentality, culture, and social conditions. Thermal comfort has various applications in fields such as ecology, environment, human health, commerce, and tourism and leisure [15,16,17,18]. Currently, a variety of indicators have been used to assess the thermal comfort level of populations or individuals. Among them, the Standard Effective Temperature (SET) comprehensively reflects the overall thermal sensation of the human body in the form of equivalent temperature. Thermal Sensation Voting (TSV) is used to describe the degree of subjective perception of an individual’s thermal comfort state. The Predicted Percentage of Dissatisfied (PPD) is used to estimate the proportion of people who feel uncomfortable under specific thermal environmental conditions [19,20]. However, in terms of building design, HVAC system control, and thermal energy optimization, one of the most relevant indicators is the Predicted Average Voting Rate (PMV). PMV is a comprehensive index used to predict the average voting results of a user group on a seven-level thermal sensation scale. When the heat generated inside the human body is balanced with the heat lost to the environment, the human body is considered to be in a state of thermal equilibrium [21]. The calculation of PMV is based on four environmental parameters and two individual parameters: air temperature, air velocity, mean radiant temperature and relative humidity, as well as clothing thermal resistance (lcl) and metabolic rate (M). According to ISO Standard 7730 [22], the PMV model is formulated based on the human heat balance and requires the combined consideration of environmental and personal parameters. The standard further specifies that air velocity should be interpreted as the relative air velocity experienced by the subject, accounting for both ambient airflow and body movement, while clothing insulation should be adjusted to reflect realistic wearing conditions. These clarifications, refined during the latest revision process, aim to improve the consistency and reliability of PMV-based thermal comfort assessment across different application scenarios [23].

Due to its unique natural environment characteristics, research on thermal comfort conditions and human body adaptability in high-altitude areas has attracted the attention of many scholars. However, there are still relatively few studies on thermal comfort in high-altitude areas. Some scholars [24] have studied the impact of the special environment in plateau areas on the thermal comfort of residents, some scholars [25,26,27,28] have studied the physiological adaptation and thermal adaptation behavior of local residents, and some scholars [29,30,31,32,33,34] have focused on building technology or design to improve thermal comfort. For example, in order to study the impact of plateau low-pressure and hypoxic environments on human thermal comfort, Guan-nan Duan et al. [24] conducted experimental verification in Tibet, China. The results showed that the subjects’ thermal sensation, thermal comfort, and average temperature decreased as the partial pressure of blood oxygen decreased. In order to establish a thermal comfort evaluation system suitable for plateau low-pressure and hypoxic environments, Yu et al. [5] conducted a field study combining environmental parameter measurements and subjective questionnaire surveys in Tibet. The results show that the actual thermoneutral temperature of local residents is much lower than the predicted value of the traditional PMV model. Yu et al. obtained a unique fitness coefficient (λ = −0.34) through data analysis, and then constructed a modified aPMV model. In order to explore the impact of solar radiation on winter thermal comfort under the special climate of the plateau, Huang and Kang et al. [35] conducted field measurements and simulation studies on office buildings in Lhasa, Tibet. The results found that despite being in a cold climate zone, strong solar radiation causes indoor overheating in winter to be much more serious than in summer, and the thermal environment in the area near the window exceeds the upper limit of the comfort range during most daytime hours. The study further reveals residents’ adaptive behavior, mainly by drawing curtains, and points out that this behavior will significantly weaken the energy-saving effect of passive solar design. Based on this, researchers proposed a thermal mass shading (TMS) design that can reduce overheating time in winter by an average of 62.2%, effectively improving the indoor thermal environment. In order to explore the unique dressing behavior of plateau residents to adapt to the climate with large temperature differences between day and night, Song et al. [36] conducted an experimental study on the traditional symmetrical and asymmetrical dressing styles of Tibet. The results show that although asymmetrical clothing (taking off the right sleeve) increases the total heat loss of the human body by 7.2–25.7%, it optimizes local heat dissipation distribution, reduces the difference in heat loss in various parts of the body, and increases the thermal neutral temperature of residents by 2 °C. In order to study the impact of tree morphological indicators on outdoor microclimate and human thermal comfort in high-altitude cold areas, Yingzi Zhang et al. [37] conducted field measurements and numerical simulation studies in Lhasa, Tibet, China. The results showed that leaf area index (LAI) is a key factor affecting the thermal environment and thermal comfort of space under trees, followed by tree height and crown width, while the improvement potential of height under branches is relatively limited.

At present, research on thermal comfort has produced many research topics and results, mainly focusing on indoor building thermal comfort, human body thermal adaptation, comfort models and other aspects. However, there are relatively few studies on thermal comfort in high-altitude areas. Due to the high sensitivity of high-altitude areas to climate change, the booming tourism industry, and the rapid growth of population, it is necessary to systematically review the relevant literature on thermal comfort research in high-altitude areas, clarify the mainstream research framework and identify research topics, frontiers and trends in this field. This paper aims to fill gaps in existing research, focusing on the challenges and coping strategies of thermal comfort in high-altitude areas, analyzing the limitations of existing studies, and proposing suggestions for future research directions. Based on the bibliometric analysis of CiteSpace, a systematic review of the literature related to thermal comfort in high-altitude areas was conducted in order to help relevant researchers understand the research progress in journals, countries, research fields, keyword co-occurrences and citations, etc., and to promote the improvement and relief of thermal comfort in high-altitude areas.

2. Materials and Methods

2.1. Research Method

This article uses bibliometric analysis and literature analysis methods to initially understand the development trend of plateau thermal comfort research. Knowledge graph is a cutting-edge analysis method in bibliometrics and scientometrics which can intuitively express the results of quantitative analysis of subject knowledge in a visual form. Current knowledge graph analysis tools include HistCite, SCI2, VOSviewer and CiteSpace [38]. CiteSpace software is a widely used bibliometric analysis visualization software based on the Java platform designed and developed by Professor Chaomei Chen of Drexel University in the United States. It is an interactive analysis tool that combines bibliometrics, information visualization principles and data mining algorithms [39]. The visual knowledge network created by CiteSpace is composed of nodes and lines. The nodes in the network represent items such as co-authors, institutions, countries, keywords, cited documents, cited authors, and cited journals, and the lines between nodes represent collaboration, co-occurrence, or co-citation relationships. CiteSpace is an important tool for visual bibliometric analysis.

2.2. Data Sources

Bibliometric analysis relies on bibliographic databases. The data sources for this study include Web of Science (WoS) and China National Knowledge Infrastructure (CNKI). In terms of academic databases, WoS is a comprehensive academic literature database and is considered to be one of the largest and most used databases in bibliometric analysis. Its core dataset includes tens of thousands of high-impact academic journals and conference documents from around the world, and it has high academic authority. Considering that it has the highest suitability for CiteSpace software, it was selected as the preferred search database for this study [40]. CNKI is China’s largest academic resource library and digital publishing platform with a monopoly position. It plays a decisive role in China’s academic, educational and scientific research fields. It covers more than 99% of China’s academic journals and practical journals, ensuring the representativeness and authority of literature sources [41]. This study also chose CNKI as the search database. The query for searching is shown in Figure 1.

WoS was extracted on 12 November 2025, and relevant publications were downloaded. We selected “Topic” as the search type, which can search titles, abstracts, author keywords, and expanded subject headings from the database. The search topic is TS = (“thermal comfort” OR “thermal sensation” OR “thermal adaptation”) AND TS = (“high altitude” OR “high-altitude” OR “plateau” OR “Tibetan Plateau” OR “hypobaric hypoxia” OR “low atmospheric pressure”). There is no limit to the search time span (2001 to present). The “Article or Review Article” and “English Language” options in the results were selected, and a total of 675 documents were obtained. Bibliographic records are saved from WoS in plain text format, set to include all records and cited references. In order to optimize the efficiency of the bibliometric analysis results, documents with little relevance to the topic and without profound reference significance were eliminated after manual screening. Then, export to CiteSpace (v6.3.R1) for deduplication and other preprocessing operations. Finally, 90 valid documents were obtained.

The CNKI data was extracted on 12 November 2025, and downloaded on the same day. The search topic is TS = (“thermal comfort” OR “thermal sensation” OR “thermal adaptation”) AND TS = (“high altitude” OR “high-altitude” OR “plateau” OR “Tibetan Plateau” OR “hypobaric hypoxia” OR “low atmospheric pressure”). The search time span is not limited (from 2001 to the present), and then the search is manually screened to eliminate documents that are not relevant to the topic and have no profound reference significance. Then, export to CiteSpace (v6.3.R1) for deduplication and other preprocessing operations. Finally, 47 valid documents were obtained.

3. Results

3.1. Analysis of Developments in the Research Field

3.1.1. Literature Development Trends

The number of publications is an important indicator of the development trend of plateau thermal comfort research [42]. Analyzing the annual changing number of publications within a selected research field allows one to assess the current state of research in the field and predict future trends [43].

The annual distribution and cumulative number of documents from WoS are shown in Figure 2. It can be seen that the number of articles published in the field of plateau thermal comfort research has increased exponentially, which means that the field is in a stage of rapid development and new theories and technologies are emerging [44]. There were very few articles published on plateau thermal comfort before 2017, indicating that this research field had not attracted the attention of the academic community. From 2017 to 2019, the number of articles published in this field gradually increased. Then, there was a decline in 2019–2020. From 2020 to 2021, the number of published articles increased moderately. But starting in 2021, the number of papers has grown rapidly. In 2024, the number of papers reached 15 for the first time. By November 2025, the number of publications in this field reached 12. The exponential line of publications in recent years has an r-squared value of 0.7508, indicating its reliability. The closer the r-squared value is to 1, the better the exponential line fits the number. In summary, the development of research fields related to plateau thermal comfort is accelerating.

The number of articles in CNKI is less than that of WoS, but the number of published articles is generally on the rise. As shown in Figure 3, research on plateau thermal comfort began in 2008, and before 2021, the annual output of articles was stable. Since 2021, there has been a rapid growth trend. In 2023, the number of papers reached eight for the first time. This also shows that the research on plateau thermal comfort is increasingly attracting the attention of Chinese scholars and has gradually become a research hotspot.

3.1.2. National Network Analysis

Based on WOS data, the node type is set to “country” to generate a knowledge graph of the national cooperation network (see Figure 4). There are 21 nodes and 11 connections. The size of the node reflects the number of articles published by the country. The larger the node, the more articles published in that country.

Table 1. Countries in the number of papers (WoS).

Rank	Countries	Count	Centrality
1	China	73	0.20
2	Australia	5	0.06
3	India	3	0.00
4	Greece	2	0.00
5	France	2	0.00
6	Germany	2	0.00
7	Japan	2	0.00
8	Switzerland	2	0.06
9	England	2	0.00
10	Peru	2	0.00
11	Sweden	1	0.01
12	Canada	1	0.00
13	Turkey	1	0.00
14	Slovenia	1	0.00
15	Belgium	1	0.00
16	Poland	1	0.00
17	Chile	1	0.00
18	Nepal	1	0.00
19	Colombia	1	0.00
20	Bahrain	1	0.00
21	Spain	1	0.00

lists the number of articles published by each country and its node centrality. Centrality represents a country’s contribution to a research field. The higher the centrality, the greater the country’s contribution to the research field. Pink circles mark nodes with centrality exceeding 0.1, constituting more critical nodes.

As can be seen from Figure 3 and Table 1, China is the country that publishes the most papers, with 73 papers, followed by Australia (five papers), India (three papers), Greece (two papers), and France (two papers). The size of these nodes is visualized, indicating that China occupies a dominant position in terms of the number of publications. In this study, China has the highest centrality at 0.2, followed by Australia (0.06), Switzerland (0.06), and Sweden (0.01). Connections between nodes indicate the existence of a cooperative relationship between the two countries, with warmer colors indicating recent cooperation and cooler colors indicating older connections. The chart shows that Australia and Nepal were the first to enter into a partnership. In recent years, China has cooperated with Australia, the United Kingdom, Germany, Japan and Switzerland.

3.1.3. Institutional Network Analysis

Based on WOS and CNKI data, the functional area is set as “institution”, the knowledge graph of the institutional cooperation network can be exported (see Figure 5 and Figure 6), and the top 20 institutions with the highest number of plateau thermal comfort research papers can be extracted from WOS and CNKI respectively, as shown in

Table 2. Top 20 institutions in the number of papers (WoS).

Rank	Institutions	Count	Centrality
1	Xi’an University of Architecture & Technology	22	0.10
2	Southwest Jiaotong University	9	0.00
3	Beihang University	6	0.00
4	Southwest Minzu University	5	0.00
5	North China Electric Power University	4	0.00
6	Tianjin University	4	0.00
7	University of New South Wales Sydney	3	0.00
8	Inner Mongolia University of Technology	3	0.06
9	China University of Mining & Technology	3	0.00
10	Qingdao University of Technology	3	0.02
11	Xizang University	3	0.01
12	Chongqing University	2	0.00
13	Jalpaiguri Government Engineering College	2	0.00
14	Universite Paris-Est-Creteil-Val-de-Marne (UPEC)	2	0.00
15	University Nacional de Ingenieria Lima	2	0.00
16	Donghua University	2	0.00
17	Agricultural University of Athens	2	0.00
18	Sichuan University	2	0.00
19	Chinese Academy of Sciences	2	0.00
20	China Meteorological Administration	2	0.02

and

Table 3. Top 20 institutions in the number of papers (CNKI).

Rank	Institutions	Count	Centrality
1	Xi’an University of Architecture & Technology	16	0.00
2	Southwest Jiaotong University	6	0.00
3	Qingdao University of Technology	5	0.00
4	School of Environmental and Municipal Engineering, Qingdao University of Technology	4	0.00
5	National Key Laboratory of Green Building	3	0.00
6	Chongqing University	3	0.00
7	Sichuan Agricultural University	2	0.00
8	School of Architecture, Xi’an University of Architecture and Technology	1	0.00
9	Donghua University Functional Protective Clothing Research Center	1	0.00
10	Donghua University School of Fashion and Art Design	1	0.02
11	Henan Engineering Laboratory of Ecological Architecture and Environmental Construction, Henan University of Science and Technology	1	0.00
12	Donghua University Key Laboratory of Modern Fashion Design and Technology, Ministry of Education	1	0.00
13	School of Architecture and Art Design, Henan University of Science and Technology	1	0.00
14	School of Architecture and Urban Planning, Chongqing University	1	0.00
15	Sichuan Grassland Science Research Institute	1	0.00
16	School of Management, Xi’an University of Architecture and Technology	1	0.00
17	Sichuan University	1	0.00
18	School of Resource Engineering, Xi’an University of Architecture and Technology	1	0.00
19	School of Architectural Engineering, Kunming University of Science and Technology	1	0.00
20	Southwest University of Science and Technology	1	0.00

. Nodes represent institutions, node size represents the number of papers from each institution, and the number of links between nodes represents the intensity of cooperation between institutions.

Figure 5 shows a total of 89 nodes, 97 connections, and the network density is 0.0248, showing strong cluster characteristics. The network structure is relatively loose, and the frequency of interactions between nodes is relatively high, indicating that cooperative relationships between different institutions are relatively frequent. As shown in Table 2, Xi’an University of Architecture and Technology is the institution that publishes the most papers, with 22 papers, followed by Southwest Jiaotong University (nine papers), Beijing University of Aeronautics and Astronautics (six papers), Southwest University for Nationalities (five papers) and North China Electric Power University (four papers). Tianjin University, University of New South Wales, Inner Mongolia University of Technology, China University of Mining and Technology, and Qingdao University of Science and Technology have also made some progress in the field of plateau thermal comfort. In terms of institutional attributes, these institutions all belong to universities, indicating that universities are still major research institutions. In terms of partnerships, Xi’an University of Architecture and Technology (22 publications, 15 cooperation connections) is at the core. Together with the China Meteorological Administration, the Chinese Academy of Sciences and other institutions, it forms the backbone of the network and actively promotes inter-agency coordination. Judging from the cooperation period, institutions such as Xi’an University of Architecture and Technology, Qingdao University of Technology, Deakin University, and Kathmandu University established cooperation earlier. In recent years, emerging institutions such as Xianyang Normal University, Kitakyushu University, Xuzhou Institute of Engineering, Hunan University, Northwestern Polytechnical University, Qingdao Agricultural University, Xuzhou Institute of Engineering, Hunan University, Northwestern Polytechnical University and Qingdao Agricultural University have joined the network as new nodes and established many new partnerships. From the perspective of centrality, the network presents an obvious “core–periphery” structure. Xi’an University of Architecture and Technology (centrality 0.10) is in the most central position and has the strongest connection control; China Meteorological Administration (centrality 0.02), City University of Hong Kong (centrality 0.01) and Qingdao University of Science and Technology (centrality 0.02) and other institutions are relatively more central, playing a key hub role in the network and promoting the flow of knowledge between different clusters.

Figure 6 shows 25 nodes, 10 connections, the network density is 0.0333, and the institutional cooperation network structure is relatively loose. As shown in Table 3, Xi’an University of Architecture and Technology is the institution that publishes the most papers, with 16 papers, followed by Southwest Jiaotong University (six papers), Qingdao University of Technology (five papers), Qingdao University of Technology School of Environmental and Municipal Engineering (four papers), National Key Laboratory of Green Building (three papers), and Chongqing University (three papers). From the perspective of node degree distribution, Xi’an University of Architecture and Technology’s node has a degree of 16. It is the only highly connected node in the network and plays the role of a core hub. From the perspective of centrality, the centrality of all nodes is 0.00, which may mean that in this network, except for highly connected nodes, other institutions have not formed effective power or intermediary status. The network structure presents an extremely unbalanced “center-edge” situation, and the overall connectivity is poor.

In summary, both Figure 5 and Figure 6 show that Xi’an University of Architecture and Technology plays a core role in plateau thermal comfort research. Comparing the distribution of institutions, most institutions have significant research accumulation and academic influence in this field and can promote the development of the plateau thermal comfort field from the level of theoretical exploration or empirical research. However, due to the strong subject specificity or regional focus of research directions, it is difficult to form sustained and in-depth cooperation and collaboration between different institutions, resulting in a relatively loose overall cooperation network structure and a significant core–periphery differentiation.

3.1.4. Co-Author Network Analysis

Based on WOS and CNKI data, the functional areas are set as “co-authors”, and a knowledge graph of the institutional cooperation network can be generated (see Figure 7 and Figure 8), with nodes representing authors. The node size represents the number of authors’ papers, and the number of links between nodes represents the intensity of collaboration between authors. The larger the node, the denser the connections, indicating that the author plays an important role in the network.

Figure 7 shows 224 nodes, 425 connections, and a network density of 0.017. Overall, the density of these collaborative networks is relatively high, and many scholars have established a large number of collaborative networks. Liu, Yanfeng and Song, Cong are particularly prominent core authors in the network. Both have published 12 times, have a node degree of 15, and have non-zero centrality (0.01), showing that they are at the center of the structure in the collaboration. In addition, scholars with certain sustained influence or activity such as Zhang, Yin, Li, and Jia have formed a relatively close collaborative sub-network.

Figure 8 shows 72 nodes, 106 connections, and the network density is 0.0415. The overall network structure presents a loose alliance model of “phased core leadership”. In the early days (around 2008), the author group represented by Liu Guodan, Xin Yuezhi, Hu Songtao and others formed a relatively active cooperation subset; recently (2023–2024), Liu Yanfeng, Song Cong, Wang Dengjia and others formed a tight small-team network.

Comparing the distribution of authors, we found that authors have formed two normal cooperation models, dominated by a certain institution or core members. However, cooperative research between China and foreign countries is not yet close enough, and future research should strengthen extensive learning and exchanges between Chinese and foreign authors.

3.2. Research Hotspot Analysis

As a condensed expression of academic discourse, an eye-catching signpost of the research frontier, and a key node of the knowledge network, keywords provide a high degree of thematic refinement for the document and represent a classic and efficient bibliometric method. They can be used to investigate hot topics and important research questions in a given subject area based on high-frequency keywords. CiteSpace analyzes research hot spots through the following two types of visualization graphs. The first one is a keyword clustering diagram, which shows the hot spots that scholars pay more attention to. The second is the keyword timeline view, which shows the distribution and changes in the most popular hot spots in different periods.

3.2.1. Keyword Co-Occurrence Network Analysis

Based on WOS and CNKI data, we set the network node type to “keyword” in CiteSpace and generated a visual keyword co-occurrence network knowledge graph (see Figure 9 and Figure 10). As shown in

Table 4. Top 20 high-frequency keywords (WoS).

Rank	Keywords	Count	Centrality
1	thermal comfort	31	0.20
2	comfort	23	0.36
3	high altitude	19	0.18
4	temperature	11	0.09
5	climate	8	0.23
6	heat	8	0.08
7	environment	8	0.17
8	buildings	7	0.09
9	hot	7	0.05
10	performance	7	0.03
11	model	6	0.06
12	residential buildings	6	0.04
13	skin temperature	6	0.04
14	consumption	5	0.18
15	air	5	0.13
16	adaptation	5	0.07
17	heat transfer	5	0.06
18	design	5	0.04
19	impact	5	0.06
20	field	4	0.03

and

Table 5. Top 20 high-frequency keywords (CNKI).

Rank	Keywords	Count	Centrality
1	thermal comfort	15	0.96
2	Tibet-bound travelers	4	0.18
3	hot feeling	4	0.11
4	low pressure	3	0.09
5	high altitude	3	0.02
6	physiological indicators	3	0.08
7	optimization strategy	3	0.00
8	orthogonal experiment	3	0.00
9	Tibet-bound personnel	2	0.05
10	heat acclimatization	2	0.17
11	thermal olxygen experience	2	0.19
12	thermal environment	2	0.06
13	wet comfort	2	0.01
14	adaptability	2	0.01
15	evaluation index	2	0.00
16	thermal comfort property	2	0.06
17	drying reaction	2	0.01
18	skin temperature	2	0.00
19	Tibetan style houses	2	0.00
20	radiation intensity	2	0.00

, the top 20 high-frequency keywords in the plateau thermal comfort research keyword co-occurrence network of WOS and CNKI were extracted respectively. Nodes represent keywords, and the larger the node in the network, the higher its frequency of occurrence. High-frequency keywords represent research hotspots in this field.

As shown in Figure 9 and Table 4, the five most frequently occurring keywords in the field of plateau thermal comfort are “thermal comfort”, “comfort”, “high altitude”, “temperature” and “climate”. The above keywords jointly indicate that this field has established a multidisciplinary research framework, the core of which lies in the interaction mechanism of “environment–human body–architecture”. Among them, “thermal comfort” is a key theme that not only connects environmental stress factors such as high altitude and climate with human physiological responses and behavioral adaptation processes but also relates to engineering practice dimensions such as building energy consumption, design strategies and simulation technology. Research shows that the field is shifting from static thermal environment assessment to dynamic climate adaptability and personalized comfort research; overall, the research shows a clear application orientation, focusing on health protection, energy-saving optimization and resilient design in special environments such as plateaus and extreme climates, reflecting the cross-integration and practical innovation of multiple disciplines such as environmental physiology, building science and energy engineering. However, not all high-frequency keywords have high centrality, nor can high-frequency keywords be relied upon to capture the full picture of research hotspots in this field. In CiteSpace, keywords with high centrality (centrality ≥ 0.1) can be regarded as the inflection point of the keyword frequency knowledge graph, and to a certain extent also represent research hotspots in this field. As can be seen from Table 4, keywords such as “comfort” (0.36), “climate” (0.23), “thermal comfort” (0.20), and “tibetan plateau” (0.19) have high centrality.

As shown in Figure 10 and Table 5, Chinese bibliometric analysis shows that the five most frequently occurring keywords in plateau thermal comfort research are “thermal comfort”, “people traveling to Tibet”, “thermal feeling”, “low pressure” and “high altitude”. The results of high-frequency word analysis show that the core area of research in this field is China’s high-altitude areas represented by the Qinghai–Tibet Plateau, and the research subjects are mainly Chinese scientific research institutions. This distribution characteristic reflects that Chinese academic circles have formed a systematic research accumulation in the field of human thermal comfort in special environments and built a case cluster featuring plateaus. Existing research can be summarized into three core dimensions: ① the environmental stress dimension, covering the action mechanisms of environmental factors such as low air pressure, high altitude, hypoxia, and extreme climate; ② the physiological-behavioral adaptation dimension, involving response mechanisms such as thermal sensation, thermal adaptation, thermal oxygen experience, and clothing adjustment of plateau people; ③ the architectural environment control dimension, including engineering practice directions such as thermal performance of Tibetan residences, heating strategy optimization, building energy-saving technology, air flow organization design, etc. Overall, research in this field shows an evolutionary trajectory from universal thermal comfort theory to extreme environment specificity, from static environmental evaluation to the exploration and expansion of dynamic physiological and behavioral adaptation mechanisms, reflecting the cross-integration of environmental ergonomics, physiology and architectural technology science in dealing with the challenges of the plateau human settlement environment. The centrality analysis results (Table 5) show that “thermal comfort” (0.96) has an absolutely dominant position as the core node; “high altitude” (0.20), “people traveling to Tibet” (0.18), “thermal adaptation” (0.17), “thermal feeling” (0.11), “thermal oxygen experience” (0.19) and other keywords have significant centrality.

Comparative analysis of keyword co-occurrence data in the WoS and CNKI literature shows that domestic research shows significant regional focus and practical orientation. The core topic revolves around “plateau thermal comfort”, focusing on the thermal adaptation mechanism of people entering Tibet, the thermal oxygen exposure process, and the local adaptation strategies of Tibetan architecture and clothing. The research methods are mainly empirical methods such as orthogonal experiments, questionnaire surveys, and warm-body dummy tests. International studies demonstrate a broader interdisciplinary perspective spanning climate, building, and physiology, focusing on the analysis of the relationships between thermal comfort and core concepts such as climate, energy consumption, and simulation, and emphasizing system-level analysis and theoretical development based on modeling and simulation technologies, including CFD and neural networks. The two approaches exhibit clear complementarity in research methods, scales, and focal dimensions. Domestic studies provide concrete regional case studies and population adaptation data for the field of thermal comfort in special environments, while international research offers theoretical frameworks and methodological systems for cross-climatic comparisons, integrated energy analysis, and multi-scale modeling. Future research should further integrate empirical data from China’s high-altitude regions with international climate-adaptive models to promote cross-regional theoretical integration and methodological innovation in thermal comfort studies, addressing environmental specificity, sustainability, and health performance.

3.2.2. Keyword Cluster Analysis

Based on WOS and CNKI data, keyword clustering analysis was performed. Select the clustering function in CiteSpace, select keyword clustering, and then select the LLR algorithm to cluster the keywords. Keyword cluster diagrams for plateau thermal comfort research were obtained respectively (see Figure 11 and Figure 12). Keyword clustering studies network clusters composed of keywords with similar research topics. Keyword clustering provides an overview of current research topics in the field. The smaller the cluster number, the more keywords it contains.

According to keyword cluster analysis, research topics in the field of plateau thermal comfort can be summarized into the following five aspects, which respectively reflect multi-level research progress from physiological mechanisms to environmental design, from climate adaptation to technological optimization.

(1)

Human body thermal adaptation and physiological response

Human thermal adaptation and physiological response are fundamental to this field. The focus is on the impact mechanisms of complex environments such as low pressure, low oxygen and strong radiation on human thermal regulation, thermal sensation and individual differences. Variables such as gender differences, long-term adaptation and behavioral factors are gradually introduced to expand the systematic understanding of thermal adaptation characteristics of high-altitude populations

(2)

Thermal comfort of buildings and environment.

Research on building and environmental thermal comfort in the context of plateau regions emphasizes regional adaptability. The research objects have been expanded from single indoor environments to continuous indoor and outdoor spaces. Through strategies such as passive design, renewable energy utilization, and building envelope optimization, the research explores ways to improve the thermal environment in high-altitude areas.

(3)

Effect of low-pressure and low-oxygen environment

Research on the effects of low-pressure and low-oxygen environments has been continuously deepened, evolving from early descriptions of phenomena to quantitative analysis of metabolic levels, local thermal responses, and the coupling mechanisms of multiple environmental factors. This has laid a theoretical foundation for evaluating the thermal comfort of special environments such as high-altitude living spaces and manned cabins.

(4)

Climate and regional adaptability

Climate and regional adaptation studies place thermal comfort issues within a longer time and larger spatial scale, combining climate change, topographic features, and traditional built environment wisdom to reveal the evolution patterns of thermal comfort and local adaptation strategies in plateau regions.

(5)

Model correction and simulation technology

Model modification and simulation techniques, serving as methodological support, have continuously improved the accuracy and efficiency of high-altitude thermal comfort prediction and environmental optimization by modifying classic thermal comfort models for high altitudes and by introducing artificial intelligence and microclimate simulation technologies.

3.2.3. Evolution Analysis of Research Hotspots

Based on WOS and CNKI data, the keyword timeline views of plateau thermal comfort research are shown in Figure 13 and Figure 14, respectively.

In Figure 13, international high-altitude thermal comfort research presents three-stage evolution characteristics from “basic concept construction” to “multidisciplinary cross-cutting and deepening”. The first stage is the embryonic stage (2003–2010). The research keywords in this stage mainly include “thermal comfort”, “comfort”, “high altitude”, “cold”, and “acclimation”. The research focus during this period focused on the basic impact mechanism of the special plateau environment on human thermal comfort, mainly focusing on descriptive exploration of the relationship between climate parameters (such as temperature, air pressure) and the basic thermal response of the human body. Through on-site measurements, laboratory simulations, and questionnaire surveys, early research has initially revealed the complex challenges posed by multiple environmental factors such as low air pressure and low temperature in high-altitude areas to the human body’s thermal sensation and physiological regulation mechanisms. For example, Cena et al. [45] conducted tent field research in the Himalayas and Karakoram regions and showed that climbers can maintain a “neutral” to “slightly warm” thermal sensation by adjusting the insulation properties of clothing and sleeping bags. This reflects that behavioral regulation plays a key role in maintaining thermal comfort in an environment where low oxygen and low temperatures coexist. It also points out that thermal comfort in tents is significantly affected by outdoor climate conditions. In addition, Fuller et al. [46] conducted actual measurements and simulation analysis on high-altitude traditional houses in Nepal and proposed that in severe cold climates, reducing indoor and outdoor air infiltration is more effective in improving thermal comfort than enhancing roof insulation. They also confirmed that low-cost intervention measures such as setting up sunrooms can significantly increase indoor temperatures and reduce the proportion of thermal discomfort. The second stage is the development stage (2011–2018). The research keywords in this stage mainly include “buildings”, “energy consumption”, “model, skin temperature”, and “climate, residential buildings”. This phase of research is dedicated to developing localized thermal comfort prediction models (such as PMV correction models), conducting dynamic simulations of building energy consumption, and quantifying the thermal performance of clothing. Through the close combination of numerical simulation and empirical research, this stage aims to establish scientific building thermal design standards and indoor environment control strategies for high-altitude areas and initially realizes the cross-integration of environmental engineering, construction technology, physiology and other disciplines. For example, Li et al. [47] systematically measured the total thermal resistance and temperature level (TR) in various wearing styles such as Tibetan robes and Mongolian robes through dummy tests and real-person wearing experiments. The third stage is the deepening stage (2019–2025). The research keywords in this stage mainly include “asymmetrical dressing”, “physiological responses”, “human body”, “oxygen enrichment”, and “attached ventilation”. The research at this stage shows the characteristics of deep integration of multiple disciplines, integrating multiple fields such as human thermal physiology, architectural technology science, regional culture, and climate adaptability design. For example, Hu et al. [28] combined field tests and model simulations to reveal the coupling relationship between human body thermal response and altitude in the low-temperature and hypoxic environment of the plateau. At the same time, based on regional climate and living habits, Nie et al. [48] proposed a residential renovation strategy that takes into account cultural inheritance and thermal comfort improvement.

In Figure 14, domestic high-altitude thermal comfort research shows a three-stage development path from introduction and verification to localized system construction. The first stage is the initial stage (2008–2013). The research keywords in this stage mainly include “thermal comfort”, “low pressure”, “physiological indicators”, “orthogonal experiment”, and “air flow rate”. The research mainly draws on the international mainstream thermal comfort evaluation model (such as PMV-PPD), builds a plateau low-pressure simulation experimental chamber, and adopts an orthogonal experimental design to systematically analyze the impact mechanism of air pressure, temperature, wind speed and other parameters on human body thermal sensation and core physiological indicators (such as skin temperature, heart rate, metabolic rate) [49]. Research at this stage has confirmed that low air pressure will change the ratio of convection and evaporative heat dissipation of the human body, causing the thermal neutral temperature to shift downward compared with the normal pressure environment. The relationship between the human body’s thermal sensation and basic environmental parameters in a low-air-pressure environment has been initially established [50,51]. The research methods mainly focus on controlled variable experiments and theoretical models (such as dimensional analysis), which laid an important experimental and theoretical foundation for subsequent research. The second stage is the development stage (2014–2019). The research keywords in this stage mainly include “thermal adaptation”, “thermal oxygen experience”, “high altitude”, “plateau climate”, “design method”, and “Tibetan style dwellings”. Research has begun to distinguish the differences in thermal adaptation between people who have lived on the plateau for a long time and those who have come to Tibet for a short period of time, exploring their comprehensive adaptation characteristics at the physiological, psychological and behavioral levels [52,53]. At the same time, the research vision is closely integrated with regional architectural practice. Scholars have carried out a large number of on-site measurements and thermal environment evaluations on traditional architectural forms such as Tibetan houses and winter tents to explore their passive wisdom in dealing with severe cold and strong radiation climates [54,55]. This stage formed a research framework for the linkage of “climate environment–human body adaptation–architectural space”, promoting research from the laboratory to the field, and from universal models to regional applications. The third stage is the deepening stage (2020–2024). The research keywords in this stage mainly include “wet comfort”, “adaptability”, “local thermal resistance”, “oxygen comfort”, “evaluation method”, and “modification model”. The scope of research extends from indoor to outdoor microclimate. Driven by the policies of “healthy buildings” and sustainable development goals, this phase of research emphasizes the integration of multiple environmental factors such as heat, oxygen, and wind, and is committed to establishing a comprehensive evaluation system and precise control strategy suitable for the special climate of the plateau [56,57]. This marks that research in this field has entered a new stage that pursues both system performance optimization and health protection.

In short, high-altitude thermal comfort research has developed from analysis of the impact of a single environmental parameter to a comprehensive subject field that integrates human science, construction technology, environmental engineering and regional culture. International and domestic research have gradually formed innovative paths with different focuses while learning from each other.

3.3. Research Trend Analysis

Research trends are analyzed in CiteSpace using emergent keywords, which can identify emerging or upcoming research fronts [58]. By analyzing emergent keywords, we can clearly point out the periodic and dynamic changes in keyword appearance intensity, thereby reflecting the cutting-edge conditions and trends in the research field [59]. Based on this, we can predict which hot spots will continue to explode in the future. Based on WOS and CNKI data, the keywords with the strongest outbreaks in plateau thermal comfort research are shown in

Table 6. Top 25 keywords with the strongest citation bursts (WoS).

Keywords	Year	Strength	Begin	End	2003–2025
standards	2009	1.55	2009	2016	▂▂▂▂▂▂▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂
acclimation	2010	1.15	2010	2014	▂▂▂▂▂▂▂▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂
thermal sensation	2010	1.05	2010	2016	▂▂▂▂▂▂▂▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂
field	2016	1.74	2016	2020	▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃▃▂▂▂▂▂
indoor thermal environment	2017	1.16	2017	2018	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂▂▂▂▂▂
indoor thermal comfort	2018	2.26	2018	2019	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂▂▂▂▂
house	2018	1.69	2018	2019	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂▂▂▂▂
climate	2012	1.32	2018	2020	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▂▂▂▂▂
energy poverty	2018	1.12	2018	2019	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂▂▂▂▂
energy consumption	2018	0.99	2018	2019	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂▂▂▂▂
energy use	2013	0.84	2018	2020	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▂▂▂▂▂
hot	2016	0.8	2018	2020	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▂▂▂▂▂
consumption	2013	0.72	2018	2019	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂▂▂▂▂
architecture	2019	0.81	2019	2022	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃▂▂▂
model	2013	0.64	2019	2020	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂▂▂▂
clothing insulation	2020	1.18	2020	2021	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂▂▂
climate change	2020	0.74	2020	2022	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▂▂▂
high altitude	2003	1.2	2021	2025	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃▃
heart rate	2021	0.76	2021	2023	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▂▂
adaptation	2016	1.52	2022	2023	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂
temperature	2010	3.22	2023	2025	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃
thermal comfort	2003	1.75	2023	2025	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃
human body	2023	1.66	2023	2025	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃
heat transfer	2018	1.38	2023	2025	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃
asymmetrical dressing	2023	1.19	2023	2025	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃

and

Table 7. Top 10 Keywords with the Strongest Citation Bursts (CNKI).

Keywords	Year	Strength	Begin	End	2008–2024
physiological indicators	2008	1.8	2008	2009	▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂
orthogonal experiment	2008	1.8	2008	2009	▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂
questionnaire	2008	1.19	2008	2009	▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂
heart rate	2008	1.19	2008	2009	▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂
low pressure	2008	0.81	2008	2012	▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂
thermal comfort	2008	0.86	2015	2016	▂▂▂▂▂▂▂▃▃▂▂▂▂▂▂▂▂
thermal environment	2016	1.12	2016	2017	▂▂▂▂▂▂▂▂▃▂▂▂▂▂▂▂▂
thermal comfort property	2017	1.02	2017	2020	▂▂▂▂▂▂▂▂▂▃▃▃▃▂▂▂▂
Tibet-bound travelers	2021	1.37	2021	2024	▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃
optimization strategy	2019	0.5	2022	2024	▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃▃▃

respectively. The higher the value of the burst keyword, the higher the frequency change rate of the keyword during that period. The blue line represents the time interval, and the red line represents the time interval in which the word appears.

3.3.1. International Research Trends on Plateau Thermal Comfort

Table 6 shows the 25 strongest burst keywords from 2003 to 2025. The keyword with the highest occurrence intensity is “temperature”, with an intensity value of 3.22, which has attracted extensive research in the academic community. The keyword with the longest duration is “high altitude”, which continues to be active from 2021 to 2025, reflecting the long-term concern of research on the human body’s thermal response under special climate environments. The changing research frontiers in the field of plateau thermal comfort research can be divided into three stages based on emergent keywords.

From 2009 to 2016, the keywords representing the research frontiers during this period were “standards”, “acclimation”, and “thermal sensation”. The human body’s physiological and behavioral adaptation mechanisms to extreme environments such as low pressure and cold, as well as regional thermal comfort evaluation standards based on field surveys, have attracted widespread attention from researchers. The verification and construction of adaptive thermal comfort models, as well as empirical research on climate-adaptive architectural design and traditional clothing systems, have become hot topics. Scholars generally combine field measurements with subjective questionnaires and use indicators such as physiological equivalent temperature (PET) and thermal sensation voting (TSV) to systematically judge the applicability and limitations of existing international thermal comfort standards (such as the PMV-PPD model) in special geographical and climatic environments, thereby promoting the establishment of an evaluation system that is more in line with the actual needs and adaptability of local residents. Yang et al. [3] found in a field survey of high-altitude residential buildings in China that there was a large difference between the actual neutral temperature of residents and the predicted PMV value, highlighting the shortcomings of standard models for mechanical applications. This trend was finally clearly stated in the study by Thapa et al. [60], who directly demonstrated the role of adaptive opportunities and local climate adaptation in shaping thermoneutral temperatures by comparing the thermal comfort responses of campuses of the same institution at different altitudes, and called for the establishment of more flexible comfort standards. At this research stage, scholars focus on exploring the actual thermal neutral temperature and thermal comfort zone at high altitudes and special environments and are committed to building an adaptive thermal comfort evaluation model and framework based on field data. The study systematically compared and verified the subjective thermal sensation of residents measured in the field and the predicted values of standard models, such as PMV based on laboratory conditions, and conducted an in-depth analysis of the differences and correlations between the two. The research perspective mainly focuses on the simulation and evaluation of building envelope performance, passive energy-saving strategies (such as enhancing air tightness, adding sunrooms), and the direct mechanisms of maintaining thermal comfort at the individual level through clothing adjustments (such as Tibetan robes) and behavioral adaptation. However, existing research still requires comprehensive planning and in-depth research on the deep biological mechanisms behind long-term physiological adaptation, the role of social and cultural factors in shaping thermal expectations and tolerance, the collaborative optimization of integrated energy systems (especially renewable energy integration) and thermal comfort needs in high-altitude residential areas, and the long-term evolution trends of thermal comfort and tourism climate resources in high-altitude areas under the background of climate change.

From 2017 to 2020, the keywords representing the research frontiers during this period are “indoor thermal environment”, “indoor thermal comfort”, “house”, “climate”, “energy poverty”, “energy consumption”, etc. The concentrated emergence of these keywords marks the deepening of the research focus in this period from the early universal thermal comfort standards to the direction of regionalization, empiricalization and multi-factor intersection, with particular attention to the built environment and human body thermal adaptation issues under special climate conditions such as high altitude and severe cold. During this period, scholars conducted extensive field monitoring and questionnaire surveys to obtain more realistic thermal comfort data. The high intensity of the word “field” (Strength = 1.74) highlights the shift in research methods, that is, from laboratory simulation to on-site investigation and actual measurement in real environments. For example, Yu et al. [5] conducted field tests in residential buildings on the Qinghai–Tibet Plateau and proposed an adaptive thermal comfort model correction coefficient suitable for this area, which provided a basis for indoor environment design in severe cold plateau areas. At this research stage, scholars not only focus on the human body’s thermal response and adaptation mechanism under special climate conditions, but also actively explore how to improve indoor thermal comfort while addressing the challenges of energy poverty and high energy consumption through passive design, renewable energy integration, and system optimization. However, most research still focuses on case measurements and technical verification. Comparative studies across regions and multiple climate zones, as well as long-term tracking of the evolution of residents’ thermal adaptation behaviors, are still relatively lacking. In the future, further deepening is needed at the level of systemic, predictive and policy connection.

Since 2021, the keywords representing the research frontiers of this period are “clothing insulation”, “climate change”, “high altitude”, “heart rate”, “adaptation”, “temperature”, “thermal comfort”, “human body”, “heat transfer”, and “asymmetrical dressing”. Together, these keywords indicate that the research focus is shifting from the evaluation of single environmental parameters to the coupling analysis of multiple factors of the environment, physiology and psychology, and the integrated exploration of active adaptive strategies. In high-altitude and low-temperature areas, clothing insulation is the primary way to maintain the body’s thermal balance. Thapa et al. [61]’s research on high-altitude residences in the Himalayas showed that the thermal resistance of clothing is significantly related to residents’ thermal sensation and comfortable temperature, especially among women. This reveals the necessity of establishing thermal engineering standards for clothing in alpine areas that are in line with local living habits. At the same time, the regional effects of climate change have also received attention. The impact of the combined environment of hypoxia and low temperature on human physiological systems is the focus of recent experimental research. Zhou et al. [62] observed in a control experiment simulating a low-pressure (61.6 kPa) environment that heart rate, blood oxygen saturation and other indicators are sensitive to temperature changes, and that a hypoxic environment will amplify the cardiovascular and thermoregulatory loads caused by cold stress. In terms of thermal comfort evaluation and adaptive design, research not only focuses on the applicability correction of traditional thermal comfort indicators (such as PET, PMV) in high-altitude areas but also pays increasing attention to behavioral adaptation and spatial intervention strategies based on field surveys. For example, Yao et al. [63] conducted a field survey on the outdoor thermal comfort of the elderly in Lhasa and found that their thermal neutral PET values were different from those in plain areas and established a prediction model between thermal environment parameters and subjective thermal sensation, which provided a basis for outdoor space planning in alpine cities.

3.3.2. Research Trends on Thermal Comfort in China’s Plateau

Table 7 shows the 10 strongest burst keywords from 2008 to 2024. The keywords with the highest occurrence intensity are “physiological indicators” and “orthogonal experiments”, with an intensity value of 1.8, which has attracted extensive research in the academic community. The longest-standing one is “low pressure,” which was an active theme from 2008 to 2012. The changing research frontiers in the field of plateau thermal comfort research can be divided into three stages based on emergent keywords.

From 2008 to 2012, the keywords representing the research frontier during this period were “physiological indicators”, “orthogonal experiments”, “questionnaire surveys”, “heart rate”, and “low pressure”. Research during this period focused on the systematic observation of human physiological responses under plateau or special low-pressure environments, optimizing research plans through orthogonal experimental design, and collecting subjective feedback with the help of questionnaires, paying particular attention to the changing patterns of basic physiological parameters such as heart rate. Low pressure is a key theme throughout this stage, indicating that research is mostly focused on the impact of simulated or real low-pressure and hypoxic environments (such as plateaus, aviation, aerospace, etc.) on human physiological adaptation and health [50,64].

From 2015 to 2020, the keywords representing the research frontier during this period are “thermal comfort” and “thermal environment”, and “thermal comfort” continues to be active from 2017 to 2020. It shows that the research focus has shifted from general physiological indicators to the specific impact of thermal environment on human comfort. Research at this stage focuses on the thermal characteristics and the human body’s thermal response to indoor environments in buildings, vehicle cabins, outdoor places and other scenes. It integrates various methods such as environmental parameter monitoring, thermal sensation voting and physiological signal analysis to promote the development of thermal comfort research towards empirical and refined development.

From 2019 to 2024, the keywords representing the research frontier are “people entering Tibet” and “optimization strategy”. “People entering Tibet” has a high burst intensity (1.37), indicating that research has begun to focus on the environmental adaptation, health risks and behavioral patterns of people in specific regions (such as groups entering the plateau), reflecting the deepening of research from universality to specific application scenarios. At the same time, the emergence of “optimization strategies” shows that research does not stop at phenomenon description and mechanism analysis, but rather begins to focus on intervention measures, system optimization and policy recommendations, trying to improve environmental adaptability, enhance health security, or optimize environmental system performance through strategic design. Recent research has focused on the thermal adaptation levels, desiccation response characteristics and thermal environment transformation strategies of Tibetan residential buildings for people entering Tibet and has proposed corresponding environmental regulation and architectural design optimization suggestions [65,66,67].

Judging from the overall trend, the research frontier in this field has experienced an evolution from basic physiological response monitoring to environment-specific comfort research, and then to population-specific research and strategy optimization. The early stage focused on experimental methods and data collection, the mid-term focus was on the comfort effects of specific physical factors such as thermal environment, and the recent focus is on the particularity of regional populations and the construction of practical application strategies. This evolution reflects the discipline’s gradual development path from theoretical exploration to application orientation, from universality to refinement, and from problem description to solution design.

4. Discussion

4.1. High-Altitude Thermal Comfort Research Topic

4.1.1. Human Body Thermal Adaptation and Physiological Response

The mechanisms of thermal adaptation and physiological responses of the human body in plateau environments constitute a core focus of plateau thermal comfort research. Under plateau conditions, compound environmental factors—including low atmospheric pressure, hypoxia, intense solar radiation, and large diurnal temperature fluctuations—act simultaneously on the human thermoregulatory system, inducing a series of physiological adjustments and perceptual changes. Existing studies not only examine shifts in the thermal neutral zone and the coupling relationship between thermal sensation and thermal comfort but also increasingly emphasize the interactive effects of hypoxia and thermal stress, inter-individual and population-level differences in physiological adaptability, and their underlying mechanisms.

In recent years, controlled laboratory experiments and field investigations have progressively revealed the multidimensional nature of thermal responses in plateau environments. Hohenauer et al. [68] conducted a randomized crossover study to compare the physiological and subjective responses of male and female participants to cold stress under normoxic and hypoxic conditions. Their results showed that female subjects exhibited a more pronounced decrease in local skin temperature following hypoxic exposure, accompanied by significantly lower subjective thermal sensation scores. These findings suggest that gender plays an important role in modulating cold stress responses under hypoxia and provide a physiological basis for gender-responsive environmental and building design in plateau regions.

Duan et al. [24] further explored the synergistic effects of oxygen partial pressure and ambient temperature through experiments conducted in Tibet. The results demonstrated that reductions in ambient oxygen partial pressure led to consistent decreases in thermal sensation, thermal comfort, and mean skin temperature. Notably, under moderately warm conditions (17 °C), hypoxia exerted the most pronounced aggravating effect on thermal discomfort. This indicates that oxygen partial pressure is not only a critical determinant of oxygen supply but also a key regulatory variable influencing overall thermal comfort.

Beyond environmental parameters, increasing attention has been paid to behavioral adaptation and group-specific physiological response characteristics. Song et al. [69] investigated the asymmetric dressing behaviors commonly observed among residents in Tibetan regions and proposed a mean skin temperature calculation model based on local thermal sensitivity weighting. Through a three-stage temperature step experiment (cold–neutral–hot), the study quantified sensitivity differences among body regions in dynamic thermal environments, providing a methodological tool for understanding thermal perception mechanisms in long-term plateau residents under complex clothing conditions.

Building on this work, Zhao et al. [27] compared the thermophysiological responses of Tibetan participants under symmetrical and asymmetrical clothing configurations. The results indicated that asymmetrical clothing was associated with higher blood perfusion indices and elevated core temperatures. In cold environments, sympathetic nervous system activity was found to dominate thermoregulatory responses, and skin temperature was validated as a key indicator for assessing thermal comfort under asymmetrical dressing conditions. These findings deepen the understanding of human thermoregulation under non-uniform clothing behaviors and offer valuable references for clothing thermal design and environmental evaluation standards in plateau regions.

Overall, research on human thermal adaptation and physiological responses in plateau environments has evolved from early investigations focusing on isolated environmental variables toward a more integrated framework incorporating environmental parameters, physiological indicators, behavioral adaptations, and population differences. This body of work provides a solid empirical foundation for developing thermoregulation theories tailored to plateau conditions and for formulating adaptive intervention strategies aimed at improving thermal comfort and health in high-altitude environments.

4.1.2. Thermal Comfort of Buildings and Environment

For indoor environments, thermal comfort assessment primarily serves the design and operation of spaces such as high-altitude residences, public buildings, and barracks. Its core issue is not short-term changes in perceived heat, but rather the acceptable temperature range under long-term physiological and behavioral adaptation. Multiple field studies have shown that the thermal neutral temperature of high-altitude residents is generally about 2–4 °C lower than the sea-level standard, and under these conditions, the thermal mean value (PMV) is not zero. This phenomenon indicates that directly using the standard PMV model systematically overestimates the risk of cold discomfort in high-altitude populations. Therefore, modified PMV or adaptive models based on field surveys are more suitable for describing indoor living comfort in high-altitude areas. Key indicators include operating temperature, thermal neutral temperature, and their shift with altitude.

In contrast, the outdoor thermal environment is directly related to an individual’s acute physiological stress and health risks, especially in the context of extreme cold, strong radiation, and low-oxygen conditions in high-altitude regions. Its assessment objective should shift from “heat dissatisfaction” to “medical risk signals.” Among existing indicators, the UTCI (Urban Temperature Index) shows high sensitivity in reflecting wind chill effects and cold stress risk, making it suitable for risk assessment under extreme weather events. PET (Potential Temperature Index) is better at describing the impact of combined climate exposure on subjective comfort, but it is insufficient in reflecting hypoxia-induced physiological stress. Modified PMV (Potential Temperature Value) has relatively limited ability to indicate health risks in outdoor environments. Existing studies have shown that, under the same PET conditions, individuals in high-altitude areas have significantly higher blood oxygen saturation decreases and cold discomfort scores than those in low-altitude areas, further illustrating that a single thermal comfort index cannot directly convey health risk information.

Research on thermal comfort in buildings and the built environment under the unique geographical and climatic conditions of plateau regions is undergoing a systematic transition from single-scenario evaluation toward multi-physics coupling and regionally adaptive design paradigms. The research scope has expanded beyond conventional thermal parameters such as air temperature and humidity to encompass complex interaction mechanisms involving oxygen concentration, solar radiation, wind speed, and other environmental factors. At the same time, increasing emphasis is placed on spatial and architectural design responses that integrate local climatic characteristics with long-standing cultural and behavioral practices.

Addressing the challenge of heating in the Qinghai–Tibet Plateau, Liu et al. [70] conducted a comprehensive investigation into the performance of a combined solar heating system using both field monitoring and numerical simulation. Their study not only verified the feasibility and effectiveness of this system under extreme plateau climatic conditions but also quantified the relationship between system operational parameters and indoor thermal stability. These findings provide a technical foundation for the application of renewable energy-based heating solutions in high-altitude regions.

Building on such technological explorations, Yu et al. [5] developed an adaptive thermal comfort model tailored to Tibetan residents through long-term field surveys and statistical analyses. The study identified the locally acceptable indoor temperature range and demonstrated the limitations of applying conventional temperate-climate thermal comfort standards in plateau contexts. By incorporating regional physiological adaptation and behavioral patterns, this work highlights the necessity of localized correction and customization in thermal comfort evaluation frameworks.

In parallel, research perspectives have expanded from indoor environments to outdoor spaces. Yao et al. [63] focused on outdoor activity areas for elderly residents in Lhasa and, through microclimatic measurements combined with structured questionnaires, examined the sensitivity of this population group to variations in temperature, solar radiation, and wind speed. The study established the thermoneutral physiological equivalent temperature (PET) ranges for elderly users during both winter and summer seasons, providing empirical support for age-friendly open-space design in plateau cities.

Similarly, Xu et al. [71] investigated the microclimatic performance of traditional residential courtyards in the western Sichuan Plateau through on-site measurements and correlation analyses. The results revealed that courtyard spatial layout, orientation, and enclosure form exert significant influences on internal microclimate stability. Solar radiation and wind speed were identified as dominant regulating factors for courtyard thermal comfort, thereby elucidating the climatic adaptability embedded in traditional residential spatial configurations.

At the practical level of technological application and implementation, research has progressively shifted from diagnostic assessment toward performance-oriented optimization. Sun et al. [72] conducted a case study of an office building in Lhasa and empirically verified the effectiveness of passive strategies—such as enhanced exterior wall insulation and optimized window-to-wall ratios—in improving winter indoor thermal comfort through before-and-after renovation comparisons. The study further emphasized that under plateau conditions characterized by low humidity and intense solar radiation, humidity regulation and thermal storage strategies must be coordinated to achieve a stable and balanced thermal environment. This body of work signals a broader transition in the field from isolated technological validation toward integrated, multi-objective environmental control and design optimization.

4.1.3. Effect of Low-Pressure and Low-Oxygen Environment

Research on the mechanisms by which low-pressure and hypoxic environments affect human thermal comfort represents one of the earliest and most continuously deepened directions in this field. With advances in experimental controllability and multi-parameter synchronous monitoring technologies, studies have progressively shifted from descriptive observations toward mechanistic interpretation, establishing quantitative relationships among environmental parameters, physiological responses, and subjective thermal perception.

Wang et al. [73] simulated different altitude conditions using a controlled decompression chamber and systematically investigated the effects of stepwise reductions in ambient pressure on human thermal responses. The results indicated that decreasing air pressure led to a significant reduction in mean thermal sensation and a concomitant increase in sensitivity to airflow, while mean skin temperature remained relatively unchanged. These findings suggest that under low-pressure conditions, the perceptual threshold for dynamic cold airflow may be reduced, and thermoregulatory strategies rely more heavily on physiological compensatory mechanisms—such as vasoconstriction—rather than on changes in skin temperature alone.

Extending this line of inquiry, Cui et al. [74] demonstrated that short-term exposure to low-pressure environments significantly elevates resting metabolic rate. This finding has important implications for heat load estimation and thermal comfort evaluation in confined or semi-confined spaces, such as manned cabins, aerospace habitats, and residential buildings in plateau regions.

Considering regional differences in local thermal responses under low-pressure conditions, Zhou et al. [62] conducted multi-condition experiments at an ambient pressure of 61.6 kPa (approximately equivalent to an altitude of 4000 m). Their results revealed that the feet and calves exhibit the highest sensitivity to environmental temperature variations. Based on these observations, the authors proposed corresponding mean skin temperature ranges and recommended ambient temperature intervals for maintaining thermal comfort under this pressure condition, providing valuable guidance for the design of localized heating and air-conditioning systems in low-pressure environments.

Meanwhile, Hu et al. [75] explored thermal responses under combined extreme cold and altitude conditions and found that blood oxygen saturation is the most sensitive physiological indicator during short-term high-altitude exposure. Interestingly, the study also observed that within a certain range, increasing altitude may partially mitigate the reduction in thermal sensation induced by cold exposure. This phenomenon underscores the complexity of thermal comfort perception in cold–hypoxic environments, where multi-system physiological interactions jointly shape sensory outcomes.

From the perspective of integrated environmental comfort assessment, Guo et al. [76] compared the effects of single environmental factors and multi-factor coupling—such as thermal, luminous, and acoustic conditions—on overall comfort under both normobaric and hypobaric environments using effective function theory. The study clarified the relative contribution rankings of unit changes in different environmental parameters to overall comfort and developed a comfort zone nomogram specifically applicable to low-pressure environments. These results provide theoretical tools and design references for the coordinated optimization of multi-environmental factors in contexts such as aerospace vehicle cabins and plateau military facilities.

In addition to short-term exposure studies, research has increasingly addressed the long-term adaptive mechanisms of plateau populations. Song et al. [77] examined skin barrier structure and heat–moisture regulation functions and confirmed that prolonged exposure to low pressure, low humidity, and intense radiation leads to structural changes in the skin and weakened barrier function. These alterations subsequently affect local sweat rates and heat–moisture sensory responses, revealing distinctive adaptive characteristics of plateau populations at the tissue and physiological levels.

4.1.4. Climate and Regional Adaptability

In recent years, research on thermal comfort in plateau regions has exhibited a pronounced trend toward interdisciplinary integration and multi-scale expansion. The focus has gradually shifted from early experimental analyses centered on individual physiological responses to deeper integration with climate dynamics, regional climatic characteristics, and human–geographical adaptation strategies. This transition not only broadens the spatial and temporal dimensions of plateau thermal comfort research but also enhances its relevance to climate change adaptation and regional sustainable development.

At the climate–comfort evolution scale, Li et al. [78] systematically assessed long-term trends in thermal comfort across the Tibetan Plateau over the past five decades using the Physiological Equivalent Temperature (PET) index in conjunction with the Tourism Climate Information System (CTIS). The results indicate that, under the background of global climate warming, the frequency of cold stress days in the plateau region has decreased significantly, while the number of days suitable for tourism activities has increased accordingly. Moreover, these changes exhibit pronounced spatial heterogeneity, highlighting the combined influence of large-scale climate responses and local topographic conditions.

From the perspective of traditional architecture and indigenous adaptive wisdom, Nie et al. [48] investigated rural dwellings in the Kangba region through field surveys and analytical studies. The research systematically elucidated how traditional design strategies—such as spatial organization, envelope configuration, and material selection—achieve acceptable indoor thermal comfort under conditions of minimal fossil energy dependence. These practices reflect a profound understanding of plateau climatic constraints and offer valuable regional references for contemporary low-energy and climate-adaptive building design.

At the scale of urban and rural built environments and landscape regulation, Yilmaz et al. [79] conducted a comparative study in the alpine city of Erzurum, Turkey, examining the impacts of different landscape types and built-environment configurations on local microclimate and outdoor thermal comfort. The findings show that summer temperatures in forested areas can be up to 13 °C lower than those in densely built urban zones, while winter temperatures can be 10–15 °C lower. In addition to significantly enhancing outdoor thermal comfort, these landscape configurations also provide co-benefits in terms of air pollution mitigation and overall environmental quality improvement. The study thus offers empirical support for ecological planning and climate-adaptive urban design in cold and high-altitude regions.

4.1.5. Model Correction and Simulation Technology

Model correction and simulation technologies play a pivotal role in plateau thermal comfort research, and their development trajectory reveals a clear transition from traditional empirical adjustment toward intelligent and fine-grained simulation approaches. Early studies primarily enhanced the applicability of existing thermal comfort models in plateau environments through parameter calibration. In recent years, with the introduction of artificial intelligence techniques and computational fluid dynamics-based simulations, substantial progress has been achieved in terms of prediction accuracy, spatial resolution, and multi-environment coupling analysis.

Regarding the application of intelligent algorithms to thermal comfort prediction, Chronopoulos et al. [80] were among the first to apply artificial neural network (ANN) models to the estimation of thermal comfort indices in mountainous regions. By training meteorological datasets from two stations at different altitudes in Greece, they achieved high-precision predictions of physiological equivalent temperature (PET) and related indicators, providing a reliable assessment method for thermal environments in data-scarce high-altitude areas. Building on this approach, Maniatis et al. [81] developed a multi-site ANN-based PET estimation model for the Ainos National Park in Greece, effectively overcoming the limitation of insufficient long-term continuous meteorological monitoring in mountainous terrain. Their study further revealed clear spatiotemporal patterns in thermal comfort frequency, with higher comfort levels occurring predominantly between May and September, offering a climatic reference for tourism planning and service facility layout in high-altitude regions.

In terms of localized correction of classical thermal comfort models, Thapa et al. [60] systematically examined the influence of altitude-related differences on residents’ thermal adaptation behaviors using field survey data. Based on these findings, they modified the parameters of the Predicted Mean Vote (PMV) model to better suit plateau environments, significantly improving its predictive performance under conditions of low atmospheric pressure and strong solar radiation.

With respect to coupled simulation and environmental design optimization, Chen et al. [82] integrated orthogonal experimental design with ENVI-met (v4.4.3) microclimate simulations to quantitatively evaluate the effects of landscape elements—including vegetation configuration, water features, ground albedo, and leaf area index—on the thermal environment of a residential district in Lhasa. Based on the simulation results, an optimized landscape configuration scheme was proposed, providing both a scientific basis and quantitative tool for climate-adaptive design of high-altitude urban residential areas.

In addition, the growing application of thermoregulatory models represents an important methodological advancement in high-altitude thermal comfort research. Unlike conventional empirical indices that are primarily derived from steady-state assumptions and average population responses, thermoregulatory models explicitly simulate the dynamic processes of human heat balance and physiological regulation under complex environmental stressors, including low air pressure, hypoxia, strong solar radiation, and large diurnal temperature variations.

By integrating environmental parameters, behavioral factors, and individual physiological characteristics within a unified framework, thermoregulatory models offer enhanced robustness and adaptability in extreme and non-uniform thermal environments typical of plateau regions. Moreover, their outputs extend beyond subjective thermal sensation to include multidimensional indicators such as core and skin temperature, sweating rate, and heat strain, enabling integrated assessments of thermal comfort, safety, and health.

From a future-oriented perspective, thermoregulatory models provide a critical foundation for intelligent model correction, personalized thermal comfort prediction, and the coupling of thermal comfort evaluation with energy sustainability and health performance. Their development and localization are therefore expected to play a key role in advancing climate-resilient and health-oriented design strategies for plateau human settlements.

4.2. Limitations of Standard PMV-Based Thermal Comfort Assessment Under Low-Pressure High-Altitude Conditions

Existing studies on thermal comfort in high-altitude regions have consistently reported systematic differences in subjective thermal perception compared with sea-level environments, even under identical indoor environmental parameters and clothing insulation levels. To quantitatively describe these differences, the literature commonly adopts the thermal sensation vote offset (ΔTSV), defined as the difference between mean thermal sensation votes reported at high altitude and at sea level under comparable indoor conditions. A negative ΔTSV indicates a tendency toward cooler thermal sensation in high-altitude environments despite equivalent clothing ensembles.

Synthesis of existing field and experimental studies reveals a pronounced downward shift in thermal sensation votes toward the cooler end of the scale at high altitude. Reported ΔTSV values typically range from approximately −0.3 to −0.5, suggesting a non-negligible reduction in perceived thermal sensation associated with altitude effects. In parallel, regression analyses between thermal sensation votes and indoor air temperature consistently indicate that the neutral temperature corresponding to TSV = 0 is lower at high altitude than at sea level. Together, these findings confirm that altitude exerts an independent and quantifiable influence on thermal perception that cannot be fully compensated for by clothing insulation adjustments alone.

These systematic discrepancies also expose fundamental limitations of the Predicted Mean Vote (PMV) model as standardized in ISO 7730 when applied under low-pressure, high-altitude conditions. The PMV framework is derived from steady-state heat balance theory calibrated for sea-level atmospheric pressure, implicitly assuming constant air density, stable convective heat transfer coefficients, and simplified thermophysiological regulation. As emphasized by d’Ambrosio Alfano et al., the PMV formulation and its numerical implementation in ISO 7730 and ASHRAE 55 are mathematically consistent and reliable within the environmental and physiological conditions for which they were developed, namely moderate, steady-state environments at or near sea-level pressure [83]. Under reduced atmospheric pressure, however, changes in air density alter convective heat exchange between the human body and the surrounding environment, leading to deviations between predicted and actual thermal responses even when ambient thermal parameters remain unchanged.

PMV does not explicitly account for altitude-induced physiological adaptations. Exposure to low-pressure and hypoxic environments can trigger peripheral vasoconstriction, redistribution of skin blood flow, and changes in metabolic heat production, all of which directly influence skin temperature and subjective thermal sensation. Because these adaptive responses are not represented in standard PMV formulations, the model often fails to reproduce the observed thermal sensation shifts documented in high-altitude field studies. The steady-state assumption underlying PMV further limits its applicability in plateau environments, where thermal perception is frequently shaped by transient conditions and ongoing acclimatization processes.

In response to these limitations, recent studies increasingly emphasize the potential of modern multi-node human thermoregulation models to provide a more mechanistic representation of thermal perception in high-altitude environments. Modern multi-node thermoregulation models (e.g., JOS-3, THERMODE 2023, and the UCB Berkeley model) provide a more physiologically realistic framework by simulating vasomotor control and metabolic adaptation, which are the dominant drivers of thermal comfort and health in high-altitude environments. Among these approaches, the Joint System Thermoregulation Model (JOS-3) represents a significant advancement in modeling individual physiological responses under transient and spatially non-uniform thermal conditions [84]. The Berkeley Comfort Model was originally developed to predict human physiological and comfort responses in transient and asymmetric thermal environments [85]. Building upon the classical Stolwijk thermoregulation framework, this model explicitly resolves multiple body segments and tissue layers while incorporating inter-segment blood heat exchange and key thermophysiological control mechanisms such as vasodilation, vasoconstriction, sweating, and metabolic heat production. The THERMODE 2023 model further advances multi-node thermophysiological modeling by integrating updated representations of both active regulatory mechanisms and passive heat transfer processes, together with an explicit thermal sensation sub-model [86]. By explicitly modeling physiological responses such as vasoconstriction and metabolic adjustments, these approaches offer a more realistic basis for interpreting altitude-induced shifts in thermal sensation.

From both comfort and health perspectives, incorporating multi-node thermoregulation modeling represents a promising pathway toward improving thermal comfort assessment in high-altitude regions. Such models enable an integrated evaluation of environmental exposure and physiological strain, reflecting the growing recognition that thermal comfort and health in plateau environments are jointly driven by coupled physical and physiological mechanisms rather than by ambient thermal conditions alone.

4.3. Challenges and Perspectives in High-Altitude Thermal Comfort Research

Thermal comfort research in high-altitude regions is essential for addressing the combined effects of low ambient temperature, reduced atmospheric pressure, hypoxic conditions, and strong solar radiation. In recent years, interdisciplinary studies integrating building physics, energy systems, environmental physiology, and ergonomics have made notable progress. Existing research has investigated indoor thermal environment optimization in plateau residential buildings [3], evaluated the performance of passive and active solar heating systems [70,87], examined the thermal regulation characteristics of traditional clothing [47,88], and analyzed the effects of hypobaric environments on human thermal sensation and metabolic responses [73,74]. These studies provide important technical support for improving living conditions, reducing energy poverty, and promoting sustainable development in high-altitude areas.

Despite these advances, high-altitude thermal comfort research remains constrained by several methodological and practical limitations. Due to the complex coupling of environmental, physiological, and socio-cultural factors, current studies lack sufficient system integration, adaptability, and long-term perspectives. Based on a comprehensive review of the literature, the following key challenges and future research directions are identified.

(1)

Limitations of Existing Thermal Comfort Models under High-Altitude Conditions

Most widely used thermal comfort models, such as the PMV–PPD model, were developed based on laboratory experiments conducted in low-altitude and temperate climates, and their applicability in high-altitude environments remains limited [89]. Unique plateau conditions, including low air pressure, high solar radiation intensity, and large diurnal temperature variations, significantly affect convective and radiative heat exchange, skin blood perfusion, and metabolic rate. Although adaptive models (e.g., aPMV) and outdoor thermal indices such as UTCI and PET have been applied in some studies [5,78], these approaches typically rely on fixed parameters and do not adequately account for dynamic changes in atmospheric pressure, solar radiation, or individual acclimatization levels. Future research should focus on developing thermal comfort evaluation frameworks specifically tailored to high-altitude environments by integrating environmental parameters, physiological responses, and behavioral adaptation mechanisms.

(2)

Insufficient Integration of Vernacular Adaptation Strategies and Modern Energy-Efficient Technologies

Long-term habitation in high-altitude regions has led to the development of various indigenous adaptive strategies. Examples include the flexible thermal insulation properties of traditional Tibetan clothing [47] and the passive climate control features of vernacular dwellings, such as thick envelopes, optimized orientation, and sunspaces [48]. However, existing studies often assess traditional strategies and modern energy-saving technologies separately. The lack of systematic integration limits the potential for achieving both thermal comfort improvement and energy efficiency. Future studies should explore hybrid design approaches that combine vernacular knowledge with modern building technologies while preserving cultural identity and responding to local climatic conditions.

(3)

Limited Research on Thermal Safety in High-Altitude Occupational Environments

Current thermal comfort research predominantly focuses on residential and educational indoor environments, whereas extreme occupational settings—such as mining, tunnel construction, and high-altitude infrastructure projects—remain underexplored. These environments often involve high physical workloads combined with hypoxic conditions and, in some cases, elevated temperature and humidity, resulting in increased risks of heat stress. At present, thermal safety criteria, exposure time limits, and ventilation or cooling control strategies based on human thermal comfort are not well established for such scenarios. Field-based studies incorporating physiological monitoring and ergonomic assessment are needed to support the development of thermal safety evaluation and control methods suitable for high-altitude occupational environments.

(4)

Limited Consideration of Socio-Cultural Factors in Thermal Comfort Studies

Thermal comfort is influenced not only by physical and physiological factors but also by socio-economic conditions, energy accessibility, lifestyle habits, and cultural norms. In high-altitude regions, residents often exhibit higher tolerance to cold environments, partly due to long-term adaptation and established behavioral patterns. However, many existing studies adopt an engineering-oriented approach and give limited attention to the role of socio-cultural factors in shaping thermal perception and adaptive behavior. Future research should incorporate social and behavioral dimensions, using mixed qualitative and quantitative methods to better understand how household decision-making, fuel affordability, and cultural practices influence thermal comfort requirements.

(5)

Insufficient Assessment of Long-Term Climate Change Impacts on High-Altitude Thermal Environments

Climate change is expected to significantly alter temperature regimes, precipitation patterns, and the frequency of extreme weather events in high-altitude regions. These changes will influence building thermal performance, heating and cooling demand, and thermal comfort conditions. However, most existing studies are based on historical climate data or short-term field measurements, with limited consideration of future climate scenarios. Integrating regional climate models with building energy simulation tools would allow for systematic assessment of long-term thermal environment evolution, energy demand trends, and adaptation potential in high-altitude urban and rural areas.

(6)

Limited Application of Intelligent Monitoring and Control Technologies in High-Altitude Buildings

Advances in sensing technologies, the Internet of Things, and data-driven control methods provide new opportunities for improving thermal comfort and energy efficiency. However, high-altitude environments pose specific challenges, including sensor performance degradation under low temperatures, unstable communication networks, and limited energy supply for monitoring systems. Research on intelligent thermal environment monitoring and control systems specifically designed for high-altitude buildings remains scarce. Developing low-cost, robust, and energy-autonomous systems could enable personalized thermal comfort control and support the implementation of smart and energy-efficient buildings in plateau regions.

5. Conclusions

Facing the dual demands of high-altitude extreme environmental challenges and the construction of a healthy living environment, research on thermal comfort in high-altitude, low-pressure, hypoxic environments emerged and developed rapidly. This study uses the CiteSpace bibliometric analysis tool and uses the Web of Science core collection and CNKI as data sources to conduct visual analysis and sort out the research hot spots and research frontiers in the field of plateau thermal comfort. This study found that high-altitude thermal comfort research has formed a multidisciplinary interdisciplinary framework with “environment–human body–architecture” as the core, and the research content covers multiple clustering topics such as physiological adaptation, building technology, environmental effects, climate adaptation, model modification and comprehensive evaluation.

International research shows a three-stage evolution from “basic concept construction” to “multidisciplinary interdisciplinary deepening”. In the early stage, it focused on the basic impact and descriptive exploration of high-altitude environments on human thermal sensations. In the mid-term, it was committed to the development of localized thermal comfort models and building energy consumption simulations. In the recent period, it has delved into the integrated research of human physiological adaptation mechanisms, regional behavioral strategies and active environmental control technologies. In contrast, domestic research reflects the development path of “from introduction and verification to localized system construction”. In the early stage, it focused on low-pressure simulation experiments and orthogonal design. In the mid-term, it expanded to the thermal adaptation characteristics of plateau populations and regional architectural practices. Recently, it has deepened into cutting-edge directions such as non-uniform thermal environment, oxygen and heat collaborative regulation, and intelligent model correction.

According to bibliometric chart analysis, China occupies a dominant position in research in this field, and institutions such as Xi’an University of Architecture and Technology have become core research forces. However, the overall international cooperation network is relatively loose, showing a “core–periphery” structure. Keyword co-occurrence and burst detection further indicate that the current research frontier is gradually shifting from static thermal environment evaluation to multi-objective collaboration of dynamic climate adaptability, health performance and energy sustainability. Research hotspots focus on the physiological mechanism of thermal adaptation, hypoxia/low pressure composite effects, regionally adaptable building technology, intelligent model modification, and thermal comfort-energy-health comprehensive evaluation system.

Although significant progress has been made in this field, the following research gaps and challenges still exist:

(1)

Insufficient model localization: The applicability of existing thermal comfort models (such as PMV-PPD) in high-altitude multi-factor coupling environments is still limited, and a universal prediction framework that dynamically integrates hypoxia, radiation, and individual adaptation differences has not yet been formed.

(2)

Lack of systematic technology integration: There is insufficient research on the collaborative optimization of local adaptive wisdom (such as traditional clothing, residential design) and modern energy-saving technology, and there is a lack of systematic solutions for the deep integration of “low technology” and “high technology”.

(3)

Limited research coverage of special scenarios: Research on thermal safety and ergonomics in extreme plateau operating environments (such as tunnels and mines) is still blank, and there is a lack of corresponding environmental standards and control guidelines.

(4)

The social and cultural dimensions are not fully included: The economic, cultural, psychological and other factors and mechanisms in heat adaptation behavior have not been revealed in depth, and interdisciplinary (architecture, physiology, sociology) integration research needs to be strengthened urgently.

(5)

Long-term climate adaptability research is weak: There is a lack of prediction of future thermal environment evolution based on the coupling of climate models and building energy consumption, making it difficult to support climate resilience planning and design.

(6)

The application of intelligent technology lags behind: The research and development of low-cost, robust, multi-source data fusion intelligent monitoring and control systems suitable for plateau environments is still in its infancy.

Overall, the research framework in this field has been established, and future research will further deepen the study of certain research topics. In this study, we conducted a systematic review of this field and identified future research trends, aiming to inspire relevant researchers to further improve this field and build solutions for plateau human settlements that take into account thermal comfort improvement, energy sustainability, and cultural resilience.