Special Issue "Indoor Air Quality—What Is Known and What Needs to Be Done"

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Air Quality".

Deadline for manuscript submissions: closed (30 January 2021).

Special Issue Editors

Prof. Dr. Elisabete Carolino
E-Mail Website
Guest Editor
H&TRC—Health & Technology Research Center, ESTeSL—Escola Superior de Tecnologia da Saúde, Instituto Politécnico de Lisboa, 1990-096 Lisbon, Portugal
Interests: indoor air quality; occupational exposure; bioburden; fungi; Aspergillus spp., statistical analysis
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Carla Viegas
E-Mail Website
Guest Editor
1. H&TRC—Health & Technology Research Center, ESTeSL—Escola Superior de Tecnologia da Saúde, Instituto Politécnico de Lisboa, 1990-096 Lisbon, Portugal
2. Centro de Investigação em Saúde Pública, Escola Nacional de Saúde Pública, Universidade NOVA de Lisboa, 1600-560 Lisbon, Portugal
Interests: fungal occupational exposure; indoor air quality; aspergillus epidemiology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues

In the scope of indoor air quality (IAQ), some specific concerns have emerged and increased in importance such as indoor chemistry, airborne infection, and the impact on performance. The reported data on the impact of IAQ parameters, such as indoor temperature, ventilation rates, indoor concentration of carbon dioxide (CO2), carbon monoxide (CO), particulate matters (PM), volatile organic compounds (VOCs), nitrogen dioxide (NO2), and airborne microbes and their metabolites on occupants’ respiratory health, emphasize the increasing importance and awareness of this topic, allowing the development of new strategies for intervention and exposure prevention. Additionally, innovations in air distribution and cleaning and new measuring techniques for microbial contamination, such as next-generation sequencing, have opened up a whole new area of research, and much is still to be learnt about the interface between humans and their surrounding microorganisms.

This Special Issue will focus on the assessment of the IAQ parameters and their sources, measurements, sampling and analysis methods, as well as the potential health outcomes for indoor occupants.

Prof. Dr. Elisabete Carolino
Prof. Dr. Carla Viegas
Guest Editor

Manuscript Submission Information

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Keywords

  • indoor air quality
  • chemical parameters
  • fungi
  • bacteria
  • sampling and analyses methods
  • occupants’ health

Published Papers (10 papers)

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Research

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Article
Microbiological Contamination Assessment in Higher Education Institutes
Atmosphere 2021, 12(8), 1079; https://doi.org/10.3390/atmos12081079 - 23 Aug 2021
Viewed by 844
Abstract
The higher education sector represents a unique environment and it acts as a work environment, a learning environment for students, and frequently, also a home environment. The aim of this study was to determine the microbial contamination (SARS-CoV-2, fungi, and bacteria) [...] Read more.
The higher education sector represents a unique environment and it acts as a work environment, a learning environment for students, and frequently, also a home environment. The aim of this study was to determine the microbial contamination (SARS-CoV-2, fungi, and bacteria) in Higher Education Facilities (HEI) by using active and passive sampling methods and combining culture-based methods with molecular tools targeting Aspergillus section Fumigati. In addition, the resistance to azole profile was also assessed. Surface samples showed a range of total bacterial contamination between 1 × 103 to 3.1 × 106 CFU·m−2, while Gram-negative bacteria ranged from 0 to 1.9 × 104 CFU·m−2. Fungal contamination ranged from 2 × 103 to 1.8 × 105 CFU·m−2 on MEA, and from 5 × 103 to 1.7 × 105 CFU·m−2 on DG18. The most prevalent species found on both media was Cladosporium sp. (47.36% MEA; 32.33% DG18). Aspergillus genera was observed on MEA (3.21%) and DG18 (14.66%), but not in the supplemented media used for the azole screening. Aspergillus section Fumigati was detected in 2 air samples (2.22%, 2 out of 90 samples) by qPCR. When testing for SARS-CoV-2 all results were negative. The present study showed that although cleaning and disinfection procedures are done regularly due to the COVID-19 pandemic, being effective in eliminating SARS-CoV-2, surfaces were often contaminated with microorganisms other than SARS-CoV-2. This can be a result of increasing resistance to biocides, and to the wide range of environmental factors that can contribute to the dissemination of microbial contamination indoors. Full article
(This article belongs to the Special Issue Indoor Air Quality—What Is Known and What Needs to Be Done)
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Article
Bacterial Contamination in Health Care Centers: Differences between Urban and Rural Settings
Atmosphere 2021, 12(4), 450; https://doi.org/10.3390/atmos12040450 - 31 Mar 2021
Cited by 1 | Viewed by 720
Abstract
This study aims to assess the airborne bioburden of rural and urban Portuguese Primary Health Care Centers (PHCC) using active and passive sampling methods and identify the potential differences in airborne microbiota between both environments. The highest total aerobic mesophilic bacterial load in [...] Read more.
This study aims to assess the airborne bioburden of rural and urban Portuguese Primary Health Care Centers (PHCC) using active and passive sampling methods and identify the potential differences in airborne microbiota between both environments. The highest total aerobic mesophilic bacterial load in indoor air were found in the Vaccination Room (448 CFU.m−3) in the Rural PHCC and in the Waiting Room (420 CFU.m−3) for Urban PHCC. The total coliforms contamination level in indoor air was detected only in the Cleaning Supplies Room (4 CFU.m−3) in the Urban PHCC. The most frequent bacteria genera identified was Micrococcus (21% Rural PHCC; 31% Urban PHCC). The surface samples showed a highest total aerobic mesophilic bacterial contamination in the Treatment Room (86 × 103 CFU.m−2) from the Rural PHCC and in the Front Office (200 × 103 CFU.m−2) from the Urban PHCC. The electrostatic dust cloth (EDC) samples showed a highest bacterial load in the Urban PHCC. Total aerobic mesophilic bacterial load in settled dust and in the Heating, Ventilating and Air Conditioning (HVAC) filter samples in the Urban PHCC (8 CFU.g−1 and 6 × 103 CFU.m−2) presented higher values compared with the Rural PHCC (1 CFU.g−1 and 2.5 × 103 CFU.m−2). Urban PHCC presented higher bacterial airborne contamination compared with the Rural PHCC for the majority of sampling sites, and when compared with the indoor air quality (IAQ) Portuguese legislation it was the Rural PHCC in two sampling places who did not comply with the established criteria. Full article
(This article belongs to the Special Issue Indoor Air Quality—What Is Known and What Needs to Be Done)
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Article
Measuring Hydrogen in Indoor Air with a Selective Metal Oxide Semiconductor Sensor
Atmosphere 2021, 12(3), 366; https://doi.org/10.3390/atmos12030366 - 11 Mar 2021
Cited by 3 | Viewed by 701
Abstract
Hydrogen is a ubiquitous but often neglected gas. In analytical measurements hydrogen—as a harmless gas—often is not considered so no studies on hydrogen in indoor air can be found. For metal oxide semiconductor (MOS) gas sensors that are increasingly pushed into the application [...] Read more.
Hydrogen is a ubiquitous but often neglected gas. In analytical measurements hydrogen—as a harmless gas—often is not considered so no studies on hydrogen in indoor air can be found. For metal oxide semiconductor (MOS) gas sensors that are increasingly pushed into the application as TVOC (total volatile organic compounds) sensors, hydrogen is a severe disturbance. On the other hand, hydrogen can be an intentional choice as indicator for human presence similar to carbon dioxide. We present a field-study on hydrogen in indoor air using selective MOS sensors accompanied by an analytical reference device for hydrogen with an accuracy of 10 ppb. Selectivity is achieved by siloxane treatment combined with temperature cycled operation and training with a complex lab calibration using randomized gas mixtures, yielding an uncertainty of 40–60 ppb. The feasibility is demonstrated by release tests with several gases inside a room and by comparison to the reference device. The results show that selective MOS sensors can function as cheap and available hydrogen detectors. Fluctuations in hydrogen concentration without human presence are measured over several days to gain insight in this highly relevant parameter for indoor air quality. The results indicate that the topic needs further attention and that the usage of hydrogen as indicator for human presence might be precluded by other sources and fluctuations. Full article
(This article belongs to the Special Issue Indoor Air Quality—What Is Known and What Needs to Be Done)
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Article
Investigations of Museum Indoor Microclimate and Air Quality. Case Study from Romania
Atmosphere 2021, 12(2), 286; https://doi.org/10.3390/atmos12020286 - 23 Feb 2021
Cited by 3 | Viewed by 785
Abstract
Poor air quality inside museums is one of the main causes influencing the state of conservation of exhibits. Even if they are mostly placed in a controlled environment because of their construction materials, the exhibits can be very vulnerable to the influence of [...] Read more.
Poor air quality inside museums is one of the main causes influencing the state of conservation of exhibits. Even if they are mostly placed in a controlled environment because of their construction materials, the exhibits can be very vulnerable to the influence of the internal microclimate. As a consequence, museum exhibits must be protected from potential negative effects. In order to prevent and stop the process of damage of the exhibits, monitoring the main parameters of the microclimate (especially temperature, humidity, and brightness) and keeping them in strict values is extremely important. The present study refers to the investigations and analysis of air quality inside a museum, located in a heritage building, from Romania. The paper focuses on monitoring and analysing temperature of air and walls, relative humidity (RH), CO2, brightness and particulate matters (PM), formaldehyde (HCHO), and total volatile organic compounds (TVOC). The monitoring was carried out in the Summer–Autumn 2020 Campaign, in two different exhibition areas (first floor and basement) and the main warehouse where the exhibits are kept and restored. The analyses aimed both at highlighting the hazard induced by the poor air quality inside the museum that the exhibits face. The results show that this environment is potentially harmful to both exposed items and people. Therefore, the number of days in which the ideal conditions in terms of temperature and RH are met are quite few, the concentration of suspended particles, formaldehyde, and total volatile organic compounds often exceed the limit allowed by the international standards in force. The results represent the basis for the development and implementation of strategies for long-term conservation of exhibits and to ensure a clean environment for employees, restorers, and visitors. Full article
(This article belongs to the Special Issue Indoor Air Quality—What Is Known and What Needs to Be Done)
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Article
Comparison of CFD and Multizone Modeling from Contaminant Migration from a Household Gas Furnace
Atmosphere 2021, 12(1), 79; https://doi.org/10.3390/atmos12010079 - 07 Jan 2021
Viewed by 685
Abstract
In Central and Eastern Europe, a growing popularity of gas heaters as the main source of heat and domestic hot water can be observed. This is the result of new laws and strategies for funding that have been put in place to encourage [...] Read more.
In Central and Eastern Europe, a growing popularity of gas heaters as the main source of heat and domestic hot water can be observed. This is the result of new laws and strategies for funding that have been put in place to encourage households to stop using coal and replace it with cleaner energy sources. However, there is a growing concern that gas furnaces are prone to malfunction and can be a threat to occupants through CO (carbon monoxide) generation. To see how a faulty gas furnace with a clogged exhaust may affect a household, a series of multizone and computational fluid dynamics (CFD) simulations were carried out using the CONTAM software and CFD0 editor created by the National Institute of Standards and Technology (NIST). The simulations presented different placements of the furnace and ventilation outlet in an attached garage. The results showed how the placement influenced contaminant migration and occupant exposure to CO. It changed the amount of CO that infiltrated to the attached house and influenced occupant exposure. The results may be used by future users to minimize the risk of CO poisoning by using the proper natural ventilation methods together with optimal placement of the header in the household. Full article
(This article belongs to the Special Issue Indoor Air Quality—What Is Known and What Needs to Be Done)
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Article
Culture Media and Sampling Collection Method for Aspergillus spp. Assessment: Tackling the Gap between Recommendations and the Scientific Evidence
Atmosphere 2021, 12(1), 23; https://doi.org/10.3390/atmos12010023 - 26 Dec 2020
Cited by 5 | Viewed by 889
Abstract
Culturing is still the most widely used method for determining fungal growth. Thus, is important to identify the most suitable culture media to assess Aspergillus spp. The aim of this study was to analyze data obtained from previous studies, aiming at identifying the [...] Read more.
Culturing is still the most widely used method for determining fungal growth. Thus, is important to identify the most suitable culture media to assess Aspergillus spp. The aim of this study was to analyze data obtained from previous studies, aiming at identifying the most suitable culture media (malt extract agar (MEA) or dichloran-glycerol agar (DG18) to assess Aspergillus spp. isolation and growth. This study was conducted by using environmental samples (n = 1153). Most of the active sampling methods (air samples) were impacted directly onto both culture media. As for passive sampling methods, fungi were extracted from environmental matrices inoculated onto both media. Overall, total Aspergillus counts were higher in MEA (n = 617, 53.5%) than in DG18 (n = 536, 46.5%). Regarding Aspergillus sections, significant associations were detected with the media (χ2 (7) = 241.118, p < 0.001), the sampling approach (p < 0.001, 95% CI = (0.3 × 10−4), and the indoor environment (p < 0.001, 95% CI = (0.3 × 10−4)). As such, sampling approach and the culture media should be accurately selected when dealing with Aspergillus spp. exposure assessment. Full article
(This article belongs to the Special Issue Indoor Air Quality—What Is Known and What Needs to Be Done)
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Article
Development of a Wide-Range Non-Dispersive Infrared Analyzer for the Continuous Measurement of CO2 in Indoor Environments
Atmosphere 2020, 11(10), 1024; https://doi.org/10.3390/atmos11101024 - 23 Sep 2020
Cited by 1 | Viewed by 756
Abstract
Carbon dioxide (CO2) is an indicator of indoor air quality. Ventilation based on the use of a CO2 indicator helps to prevent people from acquiring many diseases, especially respiratory viral infections. Therefore, the monitoring of CO2 is a pivotal [...] Read more.
Carbon dioxide (CO2) is an indicator of indoor air quality. Ventilation based on the use of a CO2 indicator helps to prevent people from acquiring many diseases, especially respiratory viral infections. Therefore, the monitoring of CO2 is a pivotal issue in the control of indoor air quality. A nondispersive infrared (NDIR) analyzer with a wide range of measurements (i.e., ppmv to percentage levels) was developed for measuring carbon dioxide (CO2) in an indoor environment. The effects of optical pathlength and interfering gases were investigated. The pathlengths of the analyzer were varied at 4.8, 8, 10.4 and 16 m, and the interference gases were CO; NO2; SO2; H2O; BTEX (i.e., benzene, toluene, ethylbenzene and m-/p-xylene) and formaldehyde. The lower detection limit, selectivity and sensitivity were determined to evaluate the performance of the analyzer. It was found that different pathlengths should be used to produce linear calibration curves for CO2 from ppmv to percentage levels. As a result, a wide-range NDIR analyzer, coupled with flexible pathlengths from 4.8 to 10.4 m, was developed. In terms of interference, only H2O should be taken into account due to its high concentration in indoor air. CO should be considered in some special locations at the ppmv level. The measurement errors for ppmv and the percentage levels were 0.4 and 0.9%, respectively. Full article
(This article belongs to the Special Issue Indoor Air Quality—What Is Known and What Needs to Be Done)
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Article
Assessment of Children’s Potential Exposure to Bioburden in Indoor Environments
Atmosphere 2020, 11(9), 993; https://doi.org/10.3390/atmos11090993 - 17 Sep 2020
Cited by 5 | Viewed by 1180
Abstract
The exposure to particles and bioaerosols has been associated with the increase in health effects in children. The objective of this study was to assess the indoor exposure to bioburden in the indoor microenvironments more frequented by children. Air particulate matter (PM) and [...] Read more.
The exposure to particles and bioaerosols has been associated with the increase in health effects in children. The objective of this study was to assess the indoor exposure to bioburden in the indoor microenvironments more frequented by children. Air particulate matter (PM) and settled dust were sampled in 33 dwellings and four schools with a medium volume sampler and with a passive method using electrostatic dust collectors (EDC), respectively. Settled dust collected by EDC was analyzed by culture-based methods (including azole resistance profile) and using qPCR. Results showed that the PM2.5 and PM10 concentrations in classrooms (31.15 μg/m3 and 57.83 μg/m3, respectively) were higher than in homes (15.26 μg/m3 and 18.95 μg/m3, respectively) and highly exceeded the limit values established by the Portuguese legislation for indoor air quality. The fungal species most commonly found in bedrooms was Penicillium sp. (91.79%), whereas, in living rooms, it was Rhizopus sp. (37.95%). Aspergillus sections with toxigenic potential were found in bedrooms and living rooms and were able to grow on VOR. Although not correlated with PM, EDC provided information regarding the bioburden. Future studies, applying EDC coupled with PM assessment, should be implemented to allow for a long-term integrated sample of organic dust. Full article
(This article belongs to the Special Issue Indoor Air Quality—What Is Known and What Needs to Be Done)
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Review

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Review
Review of IAQ in Premises Equipped with Façade–Ventilation Systems
Atmosphere 2021, 12(2), 220; https://doi.org/10.3390/atmos12020220 - 05 Feb 2021
Cited by 3 | Viewed by 912
Abstract
Poor indoor air quality affects the health of the occupants of a given structure or building. It reduces the effectiveness of learning and work efficiency. Among many pollutants, PM 2.5 and 10 dusts are extremely important. They can be eliminated using mechanical ventilation [...] Read more.
Poor indoor air quality affects the health of the occupants of a given structure or building. It reduces the effectiveness of learning and work efficiency. Among many pollutants, PM 2.5 and 10 dusts are extremely important. They can be eliminated using mechanical ventilation equipped with filters. Façade ventilation devices are used as a way to improve indoor air quality (IAQ) in existing buildings. For their analysis, researchers used carbon dioxide as a tracer gas. They have shown that façade ventilation devices are an effective way to improve IAQ, but require further analysis due to the sensitivity of façade ventilation devices to the effects of wind and outdoor temperature. In addition, legal regulations in some countries require verification in order to enable the use of this type of solution as a way to improve IAQ in an era characterised by the effort to transform buildings into passive houses (standard for energy efficiency in a building). Full article
(This article belongs to the Special Issue Indoor Air Quality—What Is Known and What Needs to Be Done)
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Review
How Is Indoor Air Quality during Sleep? A Review of Field Studies
Atmosphere 2021, 12(1), 110; https://doi.org/10.3390/atmos12010110 - 14 Jan 2021
Cited by 4 | Viewed by 1431
Abstract
This review aimed to provide an overview of the characterisation of indoor air quality (IAQ) during the sleeping period, based only on real life conditions’ studies where, at least, one air pollutant was considered. Despite the consensual complexity of indoor air, when focusing [...] Read more.
This review aimed to provide an overview of the characterisation of indoor air quality (IAQ) during the sleeping period, based only on real life conditions’ studies where, at least, one air pollutant was considered. Despite the consensual complexity of indoor air, when focusing on sleeping environments, the available scientific literature is still scarce and falls to provide a multipollutants’ characterisation of the air breathed during sleep. This review, following PRISMA’s approach, identified a total of 22 studies that provided insights of how IAQ is during the sleeping period in real life conditions. Most of studies focused on carbon dioxide (77%), followed by particles (PM2.5, PM10 and ultrafines) and only 18% of the studies focused on pollutants such as carbon monoxide, volatile organic compounds and formaldehyde. Despite the high heterogeneity between studies (regarding the geographical area, type of surrounding environments, season of the year, type of dwelling, bedrooms’ ventilation, number of occupants), several air pollutants showed exceedances of the limit values established by guidelines or legislation, indicating that an effort should be made in order to minimise human exposure to air pollutants. For instance, when considering the air quality guideline of World Health Organisation of 10 µg·m−3 for PM2.5, 86% of studies that focused this pollutant registered levels above this threshold. Considering that people spend one third of their day sleeping, exposure during this period may have a significant impact on the daily integrated human exposure, due to the higher amount of exposure time, even if this environment is characterised by lower pollutants’ levels. Improving the current knowledge of air pollutants levels during sleep in different settings, as well as in different countries, will allow to improve the accuracy of exposure assessments and will also allow to understand their main drivers and how to tackle them. Full article
(This article belongs to the Special Issue Indoor Air Quality—What Is Known and What Needs to Be Done)
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