Search Results (65)

This study investigates the impact of teacher decisions and other contextual factors on indoor air quality (IAQ) in mechanically ventilated elementary school classrooms using low-cost air quality sensors. Four classrooms at a K–8 school in San Jose, California, were monitored for airborne particulate matter (PM), carbon dioxide (CO₂), temperature, and humidity over seven weeks. Each classroom was equipped with an HVAC system and a portable air cleaner (PAC), with teachers having full autonomy over PAC usage and ventilation practices. Results revealed that teacher behaviors, such as the frequency of door/window opening and PAC operation, significantly influenced both PM and CO₂ levels. Classrooms with more active ventilation had lower CO₂ but occasionally higher PM_2.5 due to outdoor air exchange, while classrooms with minimal ventilation showed the opposite pattern. An analysis of PAC filter material and PM morphology indicated distinct differences between indoor and outdoor particle sources, with indoor air showing higher fiber content from clothing and carpets. This study highlights the critical role of teacher behavior in shaping IAQ, even in mechanically ventilated environments, and underscores the potential of low-cost sensors to support informed decision-making for healthier classroom environments. Full article

Evaluating ventilation behavior inside classrooms in hot climates is fundamental to ensure good indoor air quality and proper thermal comfort, thus guaranteeing a healthy environment for the users. This study analyzes the impact of mixed ventilation strategies, which combine mechanical extractors and organic air cleaners (OACs), on CO₂ concentration and temperature distribution in an air-conditioned classroom with closed doors and windows. We used computational fluid dynamics simulations to analyze the effect of different extractor and OACs configurations on airflow distribution and average temperature, as well as the temporal evolution of average CO₂ concentrations inside the classroom. The configuration with one extractor and two OACs reduces CO₂ concentrations to 613 ppm, representing an effective solution with lower energy consumption. These findings demonstrate that hybrid ventilation systems can significantly improve IAQ and maintain thermal comfort, offering viable and energy-efficient alternatives for enclosed classrooms in hot climate regions. Full article

Bioaerosol particles contribute to the reduced indoor air quality and cause various health issues, thus their concentration must be managed. Air cleaning is one of the most viable technological options for reducing quantities of indoor air contaminants. This study assesses the effectiveness of a prototype multi-stage air cleaner in reducing bioaerosol particle viability and concentrations. The single-pass type unit consisted of non-thermal plasma (NTP), ultraviolet-C (UV-C) irradiation, bipolar ionization (BI), and electrostatic precipitation (ESP) stages. The device was tested under controlled laboratory conditions using Escherichia coli (Gram-negative) and Lactobacillus casei (Gram-positive) bacteria aerosol at varying airflow rates (50–600 m³/h). The device achieved over 99% inactivation efficiency for both bacterial strains at the lowest airflow rate (50 m³/h). Efficiency declined with increasing airflow rates but remained above 94% at the highest flow rate (600 m³/h). Among the individual stages, NTP demonstrated the highest standalone inactivation efficiency, followed by UV-C and BI. The ESP stage effectively captured inactivated bioaerosol particles, preventing re-emission, while an integrated ozone decomposition unit maintained ozone concentrations below safety thresholds. These findings show the potential of multi-stage air cleaning technology for reducing bioaerosol contamination in indoor environments, with applications in healthcare, public spaces, and residential settings. Full article

As cement production causes large amounts of CO₂ emissions and is not sustainable, there is a growing worldwide interest in developing cleaner construction materials by reducing carbon emissions and reusing existing industrial waste. Also, antimicrobially active construction materials are gaining attention due to enhancing structural longevity. By preventing microbial growth, these materials help to improve indoor air quality and occupant health. Geopolymer mortars/concretes (GPM/GPC) with high mechanical, physical and durability properties are considered as an eco-friendly alternative to ordinary Portland cement (OPC) mortars/concretes. In this study, the composition, microstructural, mechanical and antimicrobial properties of geopolymers produced at different curing temperatures (60, 80, 100 and 120 °C) were investigated. Low-lime fly ash was used as binder and sodium silicate and sodium hydroxide were used as the alkaline solution in geopolymer production. Although X-ray fluorescence (XRF) results showed an increase in geopolymerization products with increasing temperature, SEM analysis showed that the crack formation that occurs in the microstructure of geopolymers cured above 100 °C leads to decreased mechanical properties. The strength and antimicrobial performance test results for geopolymer mortars showed that the optimum temperature was 100 °C, and the highest compressive strength (48.41 MPa) was reached at this temperature. A decrease in strength was observed due to cracks occurring in the microstructure at higher temperatures. The agar diffusion method was used to determine the antimicrobial activity of GPMs against four bacteria and one fungus species. The antimicrobial activity test results showed that the samples subjected to thermal curing at 100 °C formed the highest inhibition zones (38.94–49.24 mm). Furthermore, the alkalinity of the components/mixtures has a direct relationship with antimicrobial activity. As a result, GPMs with superior antimicrobial and mechanical properties can be considered as promising building materials, especially for construction applications where hygiene is a priority and for structures that are likely to be exposed to microbial corrosion. Full article

The mitigating effects of straw burning bans on air pollution are widely known; however, their effects on indoor air pollution are generally ignored. Cooking fuel use is an important factor that affects indoor air quality. However, the debate over the pros and cons of a province-wide ban on straw burning has been a major issue in environmental economics. By utilizing household survey data, this study investigates the role of straw burning bans on cooking fuel use in households. To infer causal relationships, difference-in-difference models that compare households in provinces with and without a complete ban on open straw burning (COSB) are employed. The results show that COSBs promote the use of clean cooking fuels and discourage the use of firewood for cooking by households. These results hold true after a series of robustness tests, such as parallel trends and placebo tests. However, the results show that the effect of COSBs on the household use of coal as a cooking fuel is not significant. Further analysis shows heterogeneity in the effects of COSBs on the use of household cooking fuels. Thus, COSBs promote the conversion to cleaner cooking fuels in rural households, but the implementation of these policies needs to be contextualized. Full article

Chemical pollution is an increasing worldwide concern, with children being especially vulnerable to the harmful effects of air pollution. This study aimed to characterize the mixture of volatile organic compounds (VOCs) present in indoor air across residential, educational, and recreational settings. It analyzed data on VOC concentrations from previous sampling campaigns conducted in households with children, primary schools, and indoor swimming pools (70 buildings, 151 indoor spaces) in northern Portugal. The findings reveal the co-occurrence of 16 VOCs (1,2,4-trimethylbenzene, benzene, ethylbenzene, m/o/p-xylenes, styrene, toluene, tetrachloroethylene, 2-ethylhexanol, butanol, acetophenone, ethyl acetate, benzaldehyde, decanal, nonanal, 1-methoxy-2-propanol and limonene) across all three settings, primarily associated to emissions from building materials and detergents. However, distinct patterns were also observed in the VOCs detected across the three indoor environments: in homes, the predominant VOCs were primarily released from cleaning and fragranced products; in schools, from ammonia-based cleaners and occupant activities; and in swimming pools, the predominant airborne chemicals were disinfection by-products resulting from the chemical dynamics associated with water disinfection. Overall, the findings highlight the need for additional research to deepen our understanding of the risks posed by combined exposure to multiple indoor air chemicals for children. These results also underscore the importance of developing and enforcing regulations to monitor VOC levels in environments frequented by children and implementing preventive measures to minimize their exposure to harmful chemicals. Full article

Quarantine policies during the coronavirus disease 2019 (COVID-19) pandemic prolonged time spent at home, leading to an unintended occurrence of sick building syndrome (SBS) symptoms. The aim of this study was to investigate the prevalence of SBS symptoms among residents in Suzhou, China, during the COVID-19 pandemic. A questionnaire survey was conducted online from February to May 2022. A total of 442 adults were included in this study. The prevalence of SBS symptoms was much higher during the COVID-19 pandemic, and the proportions of general, mucosal, and skin symptoms were 59.3%, 45.5% and 49.1%, respectively. The influences of building characteristics, occupant lifestyle, indoor environment and perception of indoor environment were analysed using a multivariate logistic regression model. Neighbourhood pollutant sources, older residences, non-ownership and humidity indicators were significant risk factors for SBS symptoms. Frequent use of air fresheners was significantly associated with general (adjusted odds ratio (AOR): 4.9, 95% confidence interval (CI: 2.4–10.0), mucosal (AOR: 5.3, 95% CI: 2.4–11.5), and skin symptoms (AOR: 4.6, 95% CI: 1.6–13.1), while the use of disinfectants was significantly correlated with skin symptoms (AOR: 4.0, 95% CI: 1.5–10.7). Residents’ perception of an uncomfortable indoor environment was a significant predictor of general (AOR: 2.2, 95% CI: 1.2–4.0) and mucosal symptoms (AOR: 3.1, 95% CI: 1.6–6.0). The use of air cleaners can reduce the prevalence of general symptoms. An important finding of this study is that the psychological impact of staying at home for a long time was associated with general symptoms (AOR: 1.3, 95% CI: 1.1–1.7), which means that attention should also be paid to the mental health of residents during the COVID-19 pandemic. Although the quarantine period has now ended, our results can still serve as a reference for the impact of the indoor environment on the health of people with SBS, especially for those who stay at home for a long time, such as the elderly. Full article

Indoor air pollution, particularly in rural communities, is a significant health determinant, primarily due to the prevalence of traditional cooking practices. The WHO estimates 4.3 million annual deaths related to household air pollution. This study quantifies indoor pollutants and assesses health impacts and perceptions regarding traditional cooking. Using Extech air quality monitoring equipment, the study measured particulate matter (PM), carbon monoxide (CO), and carbon dioxide (CO₂) in 48 rural homes. A survey of 39 women gathered insights on their use of wood for cooking and perceptions of air quality. This dual approach analyzed both environmental and social dimensions. Findings showed fine particulate matter (0.3, 0.5, 1.0, and 2.5 μm) exceeded safety limits by threefold, while coarser particulates (5.0 and 10 µm) were concerning but less immediate. CO levels were mostly acceptable, but high concentrations posed risks. CO₂ levels indicated good ventilation. Survey responses highlighted reliance on wood and poor air quality perceptions demonstrating little awareness of health risks. Common symptoms included eye discomfort, respiratory issues, and headaches. The study emphasizes the need for interventions to reduce exposure to indoor pollutants and increase awareness of health risks to encourage cleaner cooking practices in rural communities. Full article

Human health is significantly impacted by the quality of the air in living areas. Numerous factors, such as the kind of particle, clean air delivery rate, room geometry, surface features, and thermal plume produced by people or other equipment, all have an impact on indoor particle movement. This work uses computational fluid dynamics to quantitatively examine the performance of a portable air purifier that is routinely used to improve the indoor air quality of a room. The volumetric flow rate, particle diameter, and placement of the air cleaner device were considered in the assessment of the particle transport characteristics. The temperature, velocity, and age of the air distribution in the room were computed in three-dimensional simulations, and the effectiveness of the air cleaning device (ACD) in eliminating contaminants was then investigated. Clean air delivery rate (CADR), collection efficiency, and particle concentration rate values were also computed for every case that was taken into consideration. It is found that CADR and collection efficiency values for larger particles are about 2–7% better than those for smaller particles. The collection efficiency of ACD with different operating conditions is in the range of 71% to 87%. Better collection performance parameters are observed with higher flow rates. Full article

Educational buildings tend to fail in the contagion containment of airborne infectious diseases because of the high number of children, for several hours a day, inside enclosed environments that often have inadequate indoor air quality (IAQ) conditions. This study aimed to assess indoor environmental quality and test the effectiveness of portable air cleaners (PACs) in alleviating airborne particle levels in schools of Central–Southern Spain during the period of reopening after the lockdown due to the COVID-19 outbreak. To accomplish this, three sampling campaigns were organized from September to December 2020 to consistently monitor temperature and relative humidity, carbon dioxide, and particulate matter in nineteen classrooms (seven school buildings). Results showed that although the recommendation of maintaining the windows open throughout the day seemed to be effective in promoting, in general, proper ventilation conditions (based on CO₂ levels). For the colder campaigns, this practice caused notorious thermal comfort impairment. In addition, a great number of the surveyed classrooms presented levels of PM_2.5 and PM₁₀, attributable to outdoor and indoor sources, which exceeded the current WHO guideline values. Moreover, considering the practice of having the windows opened, the installation of 1 unit of PACs per classroom was insufficient to ensure a reduction in particle concentration to safe levels. Importantly, it was also found that children of different ages at different education levels can be exposed to significantly different environmental conditions in their classrooms; thus, the corrective measures to employ in each individual educational setting should reflect the features and needs of the target space/building. Full article

Reducing children’s exposure to air pollution is a priority among California communities heavily impacted by air pollution exposures. We conducted an observational air quality study at a school to investigate the effectiveness of improved Heating, Ventilation, and Cooling (HVAC) system filters and portable air cleaners (PACs) in reducing children’s exposure to fine particulate matter (PM_2.5) under real-world classroom conditions. This study included five classrooms, three of which had PACs. Halfway through the study period, high-efficiency HVAC filters were installed in all five classrooms. Continuous measurements of outdoor and in-classroom PM_2.5 concentrations were used to evaluate filtration effectiveness. The air filtration strategies, alone and in combination, demonstrated 14–56% reductions in indoor PM_2.5 concentrations compared to outdoor levels. There were significant improvements in filtration resulting from HVAC filter upgrades in the two classrooms without PACs (11% and 22% improvement, p < 0.001). Upgrading HVAC filters in classrooms with PACs did not significantly improve filtration effectiveness, suggesting that utilizing both strategies simultaneously may not meaningfully improve air quality under these circumstances. CO₂ data, as a proxy for ventilation, helped demonstrate that the observed filtration effectiveness was likely impacted by the variable HVAC system use and open doors. Full article

Monitoring of IAQ is one of the foundations of the preventative actions prompted by the worldwide recognition of COVID-19 transmission. The measurement of CO₂ has emerged as one of the most popular, dependable, and easy ways to indirectly evaluate the state of indoor air renewal. Reducing the risk of respiratory diseases transmitted by aerosols is attainable through implementing and validating prevention measures made possible by CO₂ control. Isolation centers are like health facilities in that they are linked to IAQ, and the presence of natural ventilation can significantly improve the circulation of fresh air, which speeds up the removal of contaminants. This is true even though healthcare facilities are among the environments with the highest rate of COVID-19 propagation. Our investigation revealed, however, that no substantial critical data on air quality in Tanzanian isolation centers is presently available. The process of metabolic CO₂ creation and accumulation within health isolation center cubicles was investigated in this study. Crucially, we suggest comparing settings under various conditions using the indicator ppm/patient. In this research, we experimentally assessed the value of changing a few HVAC system characteristics. We looked at the data to see how well the filtration system worked concerning the submicron particle concentration. Study recommendations for CO₂ detectors and ways to reduce infection risk in shared isolation center cubicles are provided. We also show the correlation between particle size and CO₂ concentration, the correlation between CO₂ concentration derivatives and air volume presented per patient in isolation cubicles, the correlation between patient occupancy and CO₂ concentration levels in isolation cubicles, and how to improve air quality by adjusting the patient’s bed position. The study also found that for exposure lengths of two to three hours, a typical hospital cubicle with fifty to one hundred people should have an average interior CO₂ value of less than 900 ppm. Carers’ length of stay in the hospital substantially impacted the permissible CO₂ concentration. By establishing a connection between indoor air monitoring and healthcare goals, this study will aid in determining the feasibility of establishing regulations for interior CO₂ content depending on occupancy settings, strengthening preventive efforts against COVID-19. In the post-pandemic era, it will be essential to find ways to make health facilities air cleaner so that infectious diseases cannot spread in the future. Full article

This study assessed the cleaner and sustainable environment by measuring emission levels of benzene, toluene, ethylbenzene, and xylene (BTEX) from informal food traders using charcoal as the primary source of energy at a flea market in Fordsburg, Johannesburg. Volatile organic compounds (VOCs) were measured using a real-time monitor (MiniRae 3000 photoionization detector); an indoor air quality (IAQ) monitor was used to monitor environmental parameters and passive samplers in the form of Radiello badges, which were used to determine BTEX emissions from charcoal used during food preparation. Measurements were taken at 1.5 m above ground assuming the receptor’s breathing circumference using PID and Radiello. PID data were downloaded and analyzed using Microsoft Excel (Version 2019). Radiellos were sent to the laboratory to determine the BTEX levels from the total VOCs. The total volatile organic compound (TVOC) concentration over the combustion cycle was 306.7 ± 62.8 ppm. The flaming phase had the highest VOC concentration (547 ± 110.46 ppm), followed by the ignition phase (339.44 ± 40.6 ppm) and coking with the lowest concentration (24.64 ± 14.3). The average BTEX concentration was 15.7 ± 5.9 µg/m³ corresponding to the entire combustion cycle. BTEX concentrations were highest at the flaming phase (23.6 µg/m³) followed by the ignition (13.4 µg/m³) and coking phase (9.45 µg/m³). Ignition phase versus the flaming phase, there was a significant difference at 95% at a p-value of 0.09; ignition phase versus the coking phase, there was a significant difference at 95% at a p-value of 0.039; and coking phase versus the flaming phase, there was a significant difference at 95% at a p-value of 0.025. When compared to the occupational exposure limits (OELs), none of the exposure concentrations (BTEX) were above the 8 h exposure limit. The findings of this study suggest that charcoal, as a source of energy, can still be a useful and sustainable fuel for informal food traders. Shortening the ignition and flaming phase duration by using a fan to supply sufficient air can further reduce exposure to VOCs. Full article

With the development of civilisation, the awareness of the impact of versatile aerosol particles on human health and the environment is growing. New advanced materials and techniques are needed to purify the air to reduce this impact. This brings the necessity of fast and low-cost devices to evaluate the air quality from particulate and gaseous impurities, especially in a place where gas chromatography (GC) techniques are unavailable. Small portable and low-cost systems may work separately or be incorporated into devices responsible for air-cleaning processes, such as filters, smoke adsorbers, or plasma air cleaners. Given the above, this study proposes utilising a self-assembled low-cost system to evaluate air quality, which can be used in many outdoor and indoor applications. ESP32 boards with the wireless communication protocol ESP-NOW were used as the framework of the system. The concentration of aerosol particles was measured using Alphasense sensors. The concentrations of the following gases were measured: NO₂, SO₂, O₃, CO, CO₂, and H₂S. The system was used to evaluate the quality of air containing tobacco smoke after passing through an actual DBD plasma reactor where the purification occurred. A high amount of reduction in aerosol particles and a reduction in the SO₂ concentration were detected. An increase in the NO₂ concentration was seen as an undesirable effect. The aerosol particle measurements were compared with those using a professional device (GRIMM, Hamburg, Germany), which showed the same trends in aerosol particle behaviour. The obtained results are auspicious and are a step towards producing a low-cost, efficient system for evaluating air quality as well as indoor and outdoor conditions. Full article

Interest in improving ventilation and indoor air quality (IAQ) in California schools has grown since the COVID-19 pandemic. This paper presents a field protocol for simultaneous monitoring of usage patterns of in-room portable air cleaners (PACs), indoor and outdoor concentrations and composition of particulate matter (PM), and CO₂ as an indicator of outdoor air ventilation rates (VRs). This protocol was implemented for a 7-week pilot study in four occupied California classrooms in 2022. Monitoring results showed that VRs and indoor PM were generally well maintained in the classrooms studied. One classroom had much higher overall VRs, as well as higher average indoor PM2.5 concentrations compared to similar classrooms, suggesting a possible strong impact of window/door opening behavior on both VRs and indoor PM. The actual use patterns of PACs in these classrooms varied significantly. No clear correlations were observed between PAC use patterns and indoor PM2.5 concentrations in this pilot study, possibly due to low outdoor PM2.5 concentrations and already efficient central filtration (i.e., MERV 13 filters in central ventilation systems). Information gathered through such field monitoring can help schools to understand the actual classroom ventilation and IAQ conditions and best allocate resources to classrooms that need further IAQ improvements. Full article