Indoor Air Research Articles

Effect of window openings on indoor air quality and CO₂ concentration in classrooms: A Case Study of Primary School, Dhaka

Abstract. This study investigates the impact of window openings on indoor air quality (IAQ) and CO₂ levels in school classrooms in Dhaka, focusing on natural ventilation strategies to improve the learning environment. The importance of effective window design in controlling CO₂ concentrations and enhancing ventilation is critical, particularly in tropical climates like Dhaka's, where indoor air quality is often compromised due to inadequate ventilation. The study aims to explore the effect of window size and ventilation on CO₂ levels, comparing classrooms with different window configurations to identify the best strategies for improving IAQ. Over a period of two measurement campaigns, the study monitored CO₂ levels, indoor temperature, and relative humidity in two elementary schools, revealing that limited window openings, particularly when windows were 75% closed, resulted in significantly higher CO₂ concentrations. The analysis showed a direct correlation between reduced ventilation and increased CO₂ levels, with concentrations peaking at 2560 ppm, well above the recommended threshold of 1000 ppm. Factors like room design, occupancy density, and window placement contributed to variations in CO₂ levels across classrooms. The study emphasizes the need for optimized window openings to promote natural ventilation and reduce CO₂ concentrations, suggesting that opening windows beyond 50% can significantly improve IAQ. Regular monitoring, maintenance, and the implementation of effective ventilation strategies are essential to maintaining healthy indoor air quality in schools, ensuring a conducive learning environment for students. This research highlights the critical role of building design and ventilation systems in enhancing IAQ in educational settings.

Assessing the impact of natural ventilation on indoor air quality and CO2 concentration in residential apartments

This study investigates the impact of natural ventilation on indoor air quality (IAQ) and CO₂ concentration in residential buildings in Dhaka, Bangladesh, focusing on kitchen environments. Poor IAQ, particularly elevated CO₂ levels, poses significant health risks, including respiratory issues and cognitive impairments. In Dhaka, inadequate ventilation exacerbates these issues, especially in kitchens where cooking activities generate pollutants like CO₂ and particulate matter. The study aims to assess how variations in window size and ventilation influence CO₂ levels in kitchens and compare CO₂ concentrations before and after cooking. Additionally, it explores natural ventilation strategies to enhance IAQ in residential apartments. Using an experimental approach, CO₂ levels were monitored in various kitchens and living rooms over a one-week period, employing HOBO CO₂ sensors and temperature-humidity loggers. Cooking activities like grilling, frying, and boiling were analyzed to determine the effect on CO₂ concentrations. Results showed that CO₂ levels significantly increased during cooking, with kitchens exhibiting the highest concentrations. Notably, open windows contributed to lower CO₂ levels, particularly in living rooms and dining areas, emphasizing the role of natural ventilation. However, kitchens still experienced substantial CO₂ buildup, indicating the need for additional ventilation solutions. The study concludes that while open windows improve IAQ, enhanced ventilation systems and strategic airflow management are essential to reduce CO₂ levels and ensure healthier living environments in residential buildings.

Comparative assessment of pollutant emissions between biofuel briquettes and charcoal: implications for domestic cooking fuel selection

Fuels influence indoor air quality and occupants' health. This study aims to evaluate and compare the emissions of carbon monoxide (CO), carbon dioxide (CO2), and aerodynamic size less than or equal to 2.5 µm (PM2.5) from biofuel briquettes to those from household charcoal. This approach allows for selecting a fuel based on its pollutant emissions. CO emissions ranged between 0.79 ± 0.014 and 7.430 ± 0.063 g/MJ delivered for biofuels and charcoal, respectively. The emitted CO2 ranged between 2 ± 0.212 and 129 ± 1.41 g/MJ delivered for biofuels and charcoal, respectively. The PM2.5 emissions from biofuels and charcoal were 507.5 ± 61.5 and 256.50 ± 13.44 mg/MJ delivered, respectively. The specific fuel consumption varied between 4.16 ± 0.056 and 1.35 ± 0.120 kg/L for biofuels and charcoal, respectively. The Bravais-Pearson statistical tests revealed a strong correlation between pollutant emissions and certain fuel properties. The analysis of variance (ANOVA) revealed a significance in the data, with a p-value of 0.05. The results obtained provide scientific evidence to support the promotion of biofuels for cleaner, affordable, and sustainable energy from sawdust, aiming to reduce deforestation.Graphical

The Impact of the Indoor Environment on Childhood Asthma.

This manuscript reviews the impact of important indoor environmental exposures on pediatric asthma, with a focus on recent literature in the field. Studies continue to support an association between numerous indoor aeroallergens and air pollutants found in homes and schools and increased asthma morbidity overall. Several recent home and school intervention studies have shown promise, though results have been overall mixed. Indoor environmental exposures contribute to the development of asthma and impact asthma morbidity. Further research is needed to improve our understanding of how to optimize mitigation of these indoor exposures to significantly affect asthma outcomes.

Indoor air quality suffers after a wildfire

Indoor air quality suffers after a wildfire

Improvement of crop production in controlled environment agriculture through breeding

Controlled environment agriculture (CEA) represents one of the fastest-growing sectors of horticulture. Production in controlled environments ranges from highly controlled indoor environments with 100% artificial lighting (vertical farms or plant factories) to high-tech greenhouses with or without supplemental lighting, to simpler greenhouses and high tunnels. Although food production occurs in the soil inside high tunnels, most CEA operations use various hydroponic systems to meet crop irrigation and fertility needs. The expansion of CEA offers promise as a tool for increasing food production in and near urban systems as these systems do not rely on arable agricultural land. In addition, CEA offers resilience to climate instability by growing inside protective structures. Products harvested from CEA systems tend to be of high quality, both internal and external, and are sought after by consumers. Currently, CEA producers rely on cultivars bred for production in open-field agriculture. Because of high energy and other production costs in CEA, only a limited number of food crops have proven themselves to be profitable to produce. One factor contributing to this situation may be a lack of optimized cultivars. Indoor growing operations offer opportunities for breeding cultivars that are ideal for these systems. To facilitate breeding these specialized cultivars, a wide range of tools are available for plant breeders to help speed this process and increase its efficiency. This review aims to cover breeding opportunities and needs for a wide range of horticultural crops either already being produced in CEA systems or with potential for CEA production. It also reviews many of the tools available to breeders including genomics-informed breeding, marker-assisted selection, precision breeding, high-throughput phenotyping, and potential sources of germplasm suitable for CEA breeding. The availability of published genomes and trait-linked molecular markers should enable rapid progress in the breeding of CEA-specific food crops that will help drive the growth of this industry.

A Systematic Review of Indoor Environmental Quality in Passenger Transport Vehicles of Tropical and Subtropical Regions

A Systematic Review of Indoor Environmental Quality in Passenger Transport Vehicles of Tropical and Subtropical Regions

Evaluating the Acoustic Absorption of Modular Vegetation Systems: Laboratory and Field Assessments Using an Impedance Gun

Introducing vegetation is an effective strategy for improving air quality and mitigating the heat island effect. Green modules, which consist of modules that support substrates and various plant species, integrate these elements. This study analyzes the acoustic absorption properties of a specific green wall module using an impedance gun and the Scan and Paint method for laboratory and on-site measurements. The impedance gun method is effective for in situ analysis, offering advantages over standardized techniques for inhomogeneous samples. The sound absorption coefficient of the substrate and the effects of different plant species were measured. Key findings reveal that the substrate primarily influences sound absorption, with its coefficient increasing with frequency, similar to porous materials. Vegetation enhances the acoustic absorption of the substrate, depending on coverage and thickness, with 80–90% of absorption attributed to the substrate and 4–20% to vegetation. However, not all dense plant species improve absorption; some configurations may decrease it. Improvement correlates with substrate coverage and vegetation layer thickness, while the impact of plant morphology remains unclear. These findings confirm vegetation’s potential as an acoustic absorption tool in urban settings. Additionally, green walls can enhance acoustic comfort in indoor environments such as offices and schools by reducing reverberation. They also improve air quality and provide aesthetic appeal, making them a multifunctional solution for modern architecture.

A Double Extended Kalman Filter Algorithm for Weakening Non-Line-of-Sight Errors in Complex Indoor Environments Based on Ultra-Wideband Technology

A Double Extended Kalman Filter Algorithm for Weakening Non-Line-of-Sight Errors in Complex Indoor Environments Based on Ultra-Wideband Technology

Association Between Household Dust Exposure and Sleep Duration: Findings from NHANES 2005–2006

Objective: Indoor pollutants, such as household dust, are increasingly recognized as potential contributors to health problems, including sleep disturbances. This study investigates the association between household dust exposure and sleep quality among American adults, utilizing data from the National Health and Nutrition Examination Survey (NHANES) between 2005 and 2006. Methods: Data from NHANES were used in a cross-sectional design. Total dust weight (mg) was the primary exposure variable, and sleep outcomes included self-reported sleep duration, sleep latency, and physician-diagnosed sleep disorders. Data analysis was conducted using univariate and regression models in STATA (version 18.5), with adjustments for confounders. Results: 5,582 adults aged ≥18 years had available data on sleep duration, and 4,893 on sleep latency. In an adjusted model controlling for age and emotional support, dust weight was significantly associated with a slight decrease in sleep duration (adjusted β = -0.0001, p = 0.047). In multivariate logistic regression, dust weight showed a significant negative association with sleep duration (adjusted OR = 0.999, 95% CI: 0.999 to 0.999, p = 0.030), with age and emotional support demonstrating positive associations. Sleep latency showed no significant relationship with dust weight in linear regression analysis, even when controlled for emphysema and PHQ-9 score (adjusted β = -0.0002, 95% CI: -0.001 to 0.0009, p = 0.712). Multivariate logistic regression analysis also confirmed no significant association between dust weight and sleep latency. Conclusions: This study suggests that household dust exposure modestly impacts sleep duration, highlighting the value of improving indoor air quality to enhance sleep health.

Extreme heat risk and the potential implications for the scheduling of football matches at the 2026 FIFA World Cup.

Climate change is making extreme heat events more frequent and intense. This negatively impacts many aspects of society, including organised sport. As the world's most watched sporting event, the FIFA World Cup commands particular attention around the threat of extreme heat. The 2022 tournament in Qatar was moved from summer to winter in response to this threat, and now attention turns to the 2026 tournament in North America with extreme heat risk across many of the 16 host locations. We examine this risk by modelling wet bulb globe temperature (WBGT) - a widely used measure of heat stress - for the host locations using hourly meteorological data for the period 2003-2022. Our results show that 14 out of 16 host locations exceed WBGTs of 28°C, with four (nine) exceeding this threshold more than half the time during afternoons across the mean (hottest year) of the 20 year record. This threshold is important as the level beyond which some football governing bodies recommend match delay or postponement. A climatically sound argument is therefore presented to reschedule kick-off times outside the hottest afternoon hours for the host locations with highest heat risk at which no indoor air conditioned environment exists - primarily Miami and Monterrey, but also Philadelphia, Kansas City, Boston and New York. This study highlights the need to carefully assess heat risk ahead of major sporting events to help inform any potential interventions needed in the scheduling of matches and competitions in a warming climate.

A Novel Non-Line-of-Sight Error Mitigation Algorithm Using Double Extended Kalman Filter for Ultra-Wide Band Ranging Technology

In complex indoor environments, target tracking performance is impacted by non-line-of-sight (NLOS) noises and other measurement errors. In order to fix NLOS errors, a Double Extended Kalman filter (DEKF) algorithm is proposed, which refers to a kind of cascaded structure composed of two Kalman filters. In the proposed algorithm, the first filter is a classic Kalman filter (KF) and the second is an Extended Kalman filter (EKF). The time of arrival (TOA) measurements collected by multiple stationary ultra-wide band (UWB) sensors are used. Residual errors between the measured TOA and the prediction from the first KF are used to adjust the covariance of the first KF accordingly. Then, we use the estimated distance state of the first KF as a measurement vector of the second EKF in order to obtain a smoother observation. One of the advantages of the proposed algorithm is that it is able to perform target tracking with a good accuracy even without or with only one line-of-sight(LOS) TOA measurement for a period of time without prior information of the NLOS noise, which may be difficult to obtain in practical applications. Another advantage is that the accuracy does not significantly decrease when NLOS noises persist for a long period of time. Finally, the proposed DEKF can maintain high-precision positioning characteristics in both the constant velocity (CV) model and the constant acceleration (CA) model for LOS/NLOS environments. In the case of mixed LOS/NLOS environments, the RMSE of the proposed algorithm can be kept within 5 cm, while the RMSEs of other compared algorithms are easily beyond tens of centimeters. At the same time, when the confidence of RMSE is set to 95% for 1000 MC simulations, the confidence interval of the proposed algorithm is the smallest, and the mean value is 3–5 times closer to the true value compared to other algorithms. Simulation and experimental results show that the proposed algorithm performs much better than other state-of-the-art algorithms, particularly in severe mixed LOS/NLOS environments.

HEALTH RISK ASSESSMENT IN RURAL WOMEN ON EXPOSURE TO DOMESTIC INDOOR AIR POLLUTION BY COMBUSTION OF BIOMASS FUELS

Biomass fuels, derived from plants and animals, are intentionally burned by humans for various purposes, including cooking. However, the combustion of biomass fuels, such as wood, animal dung, and crop residues, often occurs in open fires, resulting in high indoor and outdoor air pollution. This poses significant health risks, particularly for women and young children. In this study conducted in villages around Meerut city in Western Uttar Pradesh, India, the focus was on rural integrated women's health, specifically those using biomass fuel for cooking. The research included three age groups of women exposed to biomass fuel and a control group using cleaner alternatives like LPG and biogas. Hematological parameters, including hemoglobin, red blood cell count, total leukocyte count, and platelet count, were analyzed to assess the impact of biomass fuel exposure on health. The study involved 180 women from 15 villages, and blood samples were collected to evaluate immunological, hematological, and biochemical parameters. Results indicated that women exposed to biomass fuel exhibited significant alterations in hematological parameters, including lower hemoglobin levels, reduced red blood cell counts, and changes in platelet counts. These findings suggest a potential association between biomass fuel exposure and health issues such as tuberculosis infection, decreased immunity, respiratory disorders, cataracts, liver dysfunction, kidney disorders, and anemia. The study emphasizes the detrimental effects of indoor air pollution from biomass fuel smoke on the health of rural women. The observed alterations in hematological parameters highlight the urgent need for interventions to reduce biomass fuel usage and mitigate health risks in these communities. This research contributes valuable insights into the complex relationship between indoor air pollution and its adverse health effects, particularly among women in rural settings.

Indoor air quality and human health risk assessment in selected high-altitude villages of Gilgit-Baltistan, Pakistan.

This research marks the inaugural endeavor in Gilgit-Baltistan (GB) to identify the primary sources of household energy and indoor air pollutants (IAPs) during the winter and additionally, to evaluate the health impacts associated with IAPs within specific high-altitude communities in Gilgit-Baltistan, Pakistan. Using the convenience sampling method, 20 households were continuously monitored to assess IAPs based on standards time-weighted average. The study found that 90% of the population relied primarily on animal dung as their main energy source, with wood, agricultural residues, electricity, and gas as other sources. The average levels of PM2.5 were five times greater, and CO levels were three times higher than the National Environmental Quality Standards (NEQS). Among the samples examined, 65% of homes were found to have inadequate ventilation and did not comply with ASHRAE standards for living rooms. Households using animal dung and wood as fuel showed elevated PM2.5 and CO levels. Health data indicated increased winter illness, with high rates of respiratory and cardiovascular issues such as morning cough (17%), eye irritation (15%), bronchitis (14%), wheezing (13%), chest tightness (12%), heart disease (11%), morning phlegm (10%), and shortness of breath (8%). The findings indicate that socioeconomic and geographic factors play a significant role in choosing solid fuels. Recommendations include raising awareness of stove maintenance and the harmful impacts of IAPs and proper ventilation, promoting cleaner fuels, and upgrading heating systems. The government should provide health screenings and subsidies for cleaner energy such as hydropower, LPG, and solar power, reducing reliance on dung and wood, and improving health in high-altitude communities.

School built environment and children's health: a scientometric analysis.

The school built environment is closely related to children's health, and research on this topic is increasing. However, bibliometric analyses seeking to provide a comprehensive understanding of the research landscape and key themes in the field are lacking. This study comprehensively explored the global trends and research hotspots on the associations between school built environment andchildren's health. We used a scientometric analysis to review the research progress. The temporal distribution ofpublications, scientific collaborations, research hotspots, research frontiers, and co-citations over the past 30 years were analyzed. The results show that the number of publications in this field rose significantly between 1987 and 2025,with research hotspots focusing on physical activity, performance, behavior, perception, thermal comfort, and indoor air quality. Environmental themes related to children's health fall into four main groups: the built environment related to children's activities, intelligent learning environments, indoor environments and interiors, and natural environments. Health outcomes and measures that reflect physiological, psychological, cognitive, behavioral, and physical factors are discussed. This study provides a broad understanding of research issues and trends related to the school built environment and children'shealth.

Healthier Indoor Environments for Vulnerable Occupants: Analysis of Light, Air Quality, and Airborne Disease Risk

This study evaluates indoor environmental quality (IEQ) in childcare facilities, focusing on air quality and lighting—key factors affecting children’s health and development. The analysis examines a nursery in Seville, Spain, where continuous monitoring revealed challenges in maintaining suitable indoor conditions. Carbon dioxide (CO2) levels often surpassed Spanish standards (770 ppm) and stricter thresholds (550 ppm) for sensitive groups, peaking at nearly 1900 ppm. These concentrations are linked to possible cognitive impairments and increased airborne pathogen risks, with Attack Rates (ARs) exceeding 70%. Passive ventilation strategies, such as window openings, proved insufficient, emphasizing the need for Controlled Mechanical Ventilation (CMV) systems to ensure consistent air renewal while maintaining thermal comfort. Lighting assessments identified insufficient circadian stimulus during key periods. Excessive lighting during nap times disrupted rest, while morning daylight levels failed to provide adequate circadian stimulation. These findings stress the importance of integrating solar protection and dynamic daylight and electric lighting systems to align with children’s biological rhythms. This research highlights the urgent need for comprehensive IEQ strategies in childcare settings, combining advanced ventilation, hygrothermal management, and circadian-friendly lighting to create safer and healthier environments for young children.

Atmospheric-level carbon dioxide gas sensing using low-loss mid-IR silicon waveguides.

Interest in carbon dioxide (CO2) sensors is growing rapidly due to the increasing awareness of the link between air quality and health. Indoor, high CO2 levels signal poor ventilation, and outdoor the burning of fossil fuels and its associated pollution. CO2 gas sensors based on integrated optical waveguides are a promising solution due to their excellent gas sensing selectivity, compact size, and potential for mass manufacturing large volumes at low cost. However, previous demonstrations have not shown adequate performance for atmospheric-level sensing on a scalable platform. Here, we report the clearly resolved detection of 500 ppm CO2 gas at 1 s integration time and an extrapolated 1σ detection limit of 73 ppm at 61 s integration time using an integrated suspended silicon waveguide at a wavelength of 4.2 µm. Our waveguide design enables suspended strip waveguides with bottom anchors while maintaining a constant waveguide core cross-sectional geometry. This unique design results in a low propagation loss of 2.20 dB/cm. The waveguides were implemented in a 150 mm silicon on insulator (SOI) platform using standard optical lithography, providing a clear path to low-cost mass manufacturing. The low CO2 detection limit of our proposed waveguide, combined with its compatibility for high-volume production, creates substantial opportunities for waveguide sensing technology in CO2 sensing applications such as fossil fuel combustion monitoring and indoor air quality monitoring for ventilation and air conditioning systems.

Sources, levels, and determinants of indoor air pollutants in Europe: A systematic review.

Clean air is a requirement for life, and the quality of indoor air is a health determinant since people spend most of their daily time indoors. The aim of this study was to systematically review the available evidence regarding the sources, determinants and concentrations of indoor air pollutants in a set of scenarios under study in K-HEALTHinAIR project. To this end, a systematic review was performed to review the available studies published between the years 2013-2023, for several settings (schools, homes, hospitals, lecture halls, retirement homes, public transports and canteens), conducted in Europe, where sources and determinants of the indoor pollutants concentrations was assessed. After a two-stage screening in abstract and full-text, 148 papers were included for data extraction. For particulate matter, carbon dioxide and volatile organic compounds, several emission sources were identified (occupancy, human activities, resuspension, cleaning products, disinfectants, craft activities, cooking, smoking), with ventilation, number of occupants, building characteristics, being considered as important determinants. This review made also possible to discuss some of the actions that are already in place or should be implemented in the future to prevent and control the presence of pollutants indoors.

A Post-Occupancy Evaluation Framework for Enhancing Resident Satisfaction and Building Performance in Multi-Story Residential Developments in Saudi Arabia

This paper presents a systematic post-occupancy evaluation (POE) of a gated apartment building in Onaizah, Qassim, Saudi Arabia, focusing on resident satisfaction and building performance. Employing a mixed-methods approach, the research combines quantitative data from questionnaires and qualitative data from walkthrough observations and interviews to assess various performance aspects, including thermal comfort, visual comfort, acoustic performance, and safety. Results indicate that residents generally expressed satisfaction with thermal comfort, visual comfort, and indoor air quality. However, concerns were highlighted in areas such as safety and security, design adequacy, and construction support services. These findings reveal that while the building meets many occupant needs, there are critical areas requiring improvement. This study underscores the importance of incorporating POE as a valuable tool for assessing building performance and informing future design and management strategies in residential developments. Finally, this study’s methodology excelled in analyzing the quality and performance of residential building elements, which contributes to enriching the literature related to facilities management. It explains the research strategy followed to provide an organized and reliable framework that can be used to evaluate performance and quality in residential buildings.

Concentrations and Source Apportionment of Tetrachloroethylene (PCE) in Aircraft Cabins

The aircraft cabin provides a unique indoor environment compared to other building environments. Tetrachloroethylene (PCE) is widely found in cabins and has clear adverse health impacts. This study investigated the PCE pollution characteristics in 56 aircraft cabins using on-flight Tenax-TA tube sampling and GC-MS analysis. PCE was detected at a high rate of 79% in sampled flights, indicating widespread contamination within the cabins. The mean concentration of PCE was 10.12 μg/m3, exceeding the 2.06 μg/m3 observed in residences in a previous study. The positive matrix factorization (PMF) model was used to identify potential sources of PCE in cabins. Six categories of sources were determined, including in-cabin cleaning products, aircraft cleaning/maintenance, cabin interior material, aircraft and vehicle exhaust, non-fuel oil and ozone-associated chemical reactions. The biggest PCE source in cabins was attributed to in-cabin cleaning products (45.30%), followed by cabin interior materials (24.90%), and aircraft cleaning/maintenance (19.82%). The findings of this study are beneficial to improving aircraft cabin air quality, reducing harmful pollutant exposure for cabin crew and passengers.