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We introduce the holographic air‐quality monitor (HAM) system, uniquely tailored for monitoring large particulate matter (PM) over 10 μm in diameter—particles critical for disease transmission and public health but overlooked by most commercial PM sensors. The HAM system utilizes a lensless digital inline holography (DIH) sensor combined with a deep learning model, enabling real‐time detection of PMs with greater than 97% true positive rate at less than 0.6% false positive rate and analysis of PMs by size and morphology at a sampling rate of 26 L/min for a wide range of particle concentrations up to 4000 particles/L. Such throughput not only significantly outperforms traditional imaging‐based sensors but also rivals some lower‐fidelity, nonimaging sensors. Additionally, the HAM system is equipped with additional sensors for smaller PMs and various air quality conditions, ensuring a comprehensive assessment of indoor air quality. The performance of the DIH sensor within the HAM system was evaluated through comparison with brightfield microscopy, showing high concordance in size and morphology measurements. The efficacy of the DIH sensor was also demonstrated in two 2‐h experiments under different environments simulating practical conditions, with one involving distinct PM‐generating events. These tests highlighted the HAM system's advanced capability to differentiate PM events from background noise and its exceptional sensitivity to irregular, large‐sized PMs of low concentration. [ABSTRACT FROM AUTHOR]

Air exchange rate is a key determinant of indoor air quality which is highly variable within the rooms of a naturally ventilated terraced house (townhouse). Window opening can increase the air exchange rate, but internal door opening between rooms inside decreases the rate. Inert perfluorocarbon gas‐phase tracers demonstrated flow within the house, and the penetration of tracers released outside into the house showed a strong dependence on wind speed and wind direction. Between experiments, it was found that the tracer could be detected within certain parts of the house weeks after the initial release, with implications for pollutants and their impact on the indoor environment. A limited number of reactive tracer experiments suggested an upper limit for indoor [OH]~1 × 105 molecule cm-3 with up to 0.5 ppt of [NO3] estimated, leading to an estimated indoor lifetime for d5 isoprene of many hours. Ultrafine particulate matter generated in the kitchen travels throughout the house, and the persistence of elevated aerosol concentrations is seen even in well‐ventilated rooms, with implications for particle exposure in the evening and during the night. [ABSTRACT FROM AUTHOR]

Indoor air quality is becoming one of the most important factors for public health, as people tend to spend more time indoors, either at home or at work. This paper combines the use of calibrated low‐cost particulate matter (PM) sensors with source apportionment algorithms to understand the factors that affect the indoor air quality within a typical UK school. Low‐cost optical particle counter (OPC) sensors were placed in three different classrooms within the school, measuring PM concentrations during a typical school week and the subsequent holiday period, to understand the role of occupancy within schools for air quality. When students were in attendance during school hours (09:00–15:30), the classroom with the greatest average PM levels had PM2.5 and PM10 mass concentrations of 14.4 and 51.0 μg/m3, respectively. During school hours, when students were present, all classrooms had average PM2.5 concentrations greater than 8.1 μg m−3 and average PM10 concentrations greater than 13.1 μg m−3. Notably, the English studies classroom exceeded the 24‐h WHO ambient PM10 guideline (45 μg m−3). Employing the non‐negative matrix factorization (NMF) algorithm for source apportionment revealed that between 93% and 98% of PM1 observed within classrooms derived from outdoor sources. This contribution diminished as particle size increased, with outdoor sources accounting for 74%–89% of PM2.5, and 19%–40% of PM10, respectively. The differences in classroom PM concentration and source percentages are attributed to differences in lesson activities, lesson frequency, flooring (carpeted versus hard flooring), location within the school, and proximity to outdoor sources such as roads. The approach described within the paper is easily translated to other indoor locations and could also be straightforwardly scaled due to its relatively low cost. Thereby, it allows for air quality management in locations crucial for the public health and educational outcomes of children. [ABSTRACT FROM AUTHOR]

The air quality in classrooms significantly impacts school children's health and learning performance. It has been reported worldwide that classroom air quality does not meet the required standard and actions are pledged for improvement. However, it poses a challenge for decision-making in terms of prioritising taking-up measures. The aim of this study is to propose a method of identifying the action measures for improving classroom air quality and prioritising them. Case studies in the UK and China were conducted, and the key measures were identified through literature studies, open-ended questionnaire surveys, and workshop discussions, which are classified into three categories: B1, policy; B2, technology; and B3, information sharing. The analytical hierarchy process (AHP) is applied in the prioritisation of the action measures. A total of 138 teachers and parents from China and the UK participated in this case study. The genetic algorithm-optimised Hadamard product (GAOHP) method is applied to justify the consistency ratio (CR) within the required threshold value in order to ensure the consistency of the subjective perception and the accuracy of comparative weights. The results show that item B2, technology, is the most desired measure by both Chinese and British parents and teachers, despite the deviation from the optimal choice in China and the UK. Among the proposed action measures, the UK respondents strongly expected air purifiers with natural ventilation as opposed to their Chinese counterparts preferring to share the real-time status of classroom air quality. Our work will provide strong support for the subsequent selection of indoor air quality improvement strategies for schools. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) and the microorganisms of duck houses may have negative impacts on animal and human health. During 2021-2022, PM2.5 and PM10 inside and outside the duck house were sampled with a built-in air sampler in Tai'an City, Shandong Province, and the diversity and abundance of microorganisms within the PM were analyzed by macrogenomic and absolute sequence analysis. The results showed that PM2.5 and PM10 concentrations in the house and at downwind points exceeded the short-term (24 h) guideline of the global air quality guidelines (AQG). Macrogenome sequencing showed that the microbial composition of the PM2.5 samples was dominated by bacteria (exceed 85%); a total of 1316 bacterial genera and 110 fungal genera were identified in PM2.5 samples from duck house 1 in winter, which were much higher than the results of amplicon sequencing method reported before, and relatively high levels of the pathogenic bacteria (Coccidioides immitis, etc.) and the conditionally pathogenic bacterium (Rothia nasimurium) were identified at the species level. Absolute quantitative sequencing detected conditionally pathogenic bacteria and allergens at high levels in PM10 samples: Corynebacterium (5.6 × 10 7 copies/g), Aerococcus (9.9 × 10 6 copies/g), Alternaria (3.3 × 10 6 copies/g), and Aspergillus (8.3 × 10 5 copies/g). Moreover, Corynebacterium was the highest content of PM10 in summer and PM2.5 samples in winter, and its pathogenicity and potential threat should be noted. The diversity and relative abundance of microorganisms were similar in the duck house and at the downwind point. The results showed that the microorganisms in the house environment have a greater influence on the air environment around the downwind point and may pose a public health risk to the staff and the surrounding area. [ABSTRACT FROM AUTHOR]

Measuring the systemic impact of major public health emergencies on the light industry and preventing various uncertain future external risks have become the key challenges to ensuring the stability of the light industry. This paper takes the occurrence of major public health emergencies as the background and focuses on environmental issues such as air pollution and indoor air quality degradation during emergencies. And to explore the multiscale impact of major public health emergencies on the light industry, typical light industry subsectors, and light industry enterprises. The findings of our study reveal that major public health emergencies have a negative impact on the light industry, particularly in the form of a short-term decline in exports, which tends to converge in the long run. Further, it is also revealed that there is heterogeneity in the impact on environmentally sensitive industries, labor-intensive industries, and others. At the microfirm level, major public health emergencies have shown a negative effect, especially the recent pandemic, which has a longer duration and a wider reach. Through multiscale research, this paper provides policy suggestions to improve the macrogovernance mechanism and risk prevention system for the light industry. [ABSTRACT FROM AUTHOR]

Background. Adequate ventilation is imperative for controlling respiratory transmission, particularly in the context of the COVID-19 pandemic. The commercial portable air cleaners have emerged as practical solutions to reduce contaminated aerosols in dental treatment rooms. This study employs computational fluid dynamics (CFD) to assess their impact on airflow dynamics. Methods. Dental treatment room models were constructed using SolidWorks software, encompassing two distinct air conditioner grille orientations (straightening and 45-degree downward directions) and five different positions for the portable air cleaner (two located at the rear left/right of the dental unit and three at the foot end of the dental unit—center, left, and right corners). The study examined alterations in airflow direction and residual aerosol concentrations using ANSYS Fluent software. Results. The incorporation of portable air cleaners in dental treatment rooms significantly reduced aerosol levels across all model configurations. Notably, the placement of the portable air cleaner emerged as a critical factor influencing airflow patterns. In models with straightening and 45-degree downward air conditioner grille orientations, optimal positioning was near the operating field and at the foot end of the dental chair, respectively. Conclusion. This investigation highlights the pivotal role of strategic portable air cleaner placement in dental treatment rooms for effective aerosol removal. Placing the air cleaner near the operating field or at the foot end of the dental chair not only improved airflow patterns but also enhanced aerosol removal efficiency, ultimately promoting superior air quality within dental treatment environments. [ABSTRACT FROM AUTHOR]

Air-change rate is an important parameter influencing residential air quality. This article critically assesses the state of knowledge regarding residential air-change rates, emphasizing periods of normal occupancy. Cumulatively, about 40 prior studies have measured air-change rates in approximately 10,000 homes using tracer gases, including metabolic CO2 . The central tendency of the air-change rates determined in these studies is reasonably described as lognormal with a geometric mean of 0.5 h-1 and a geometric standard deviation of 2.0. However, the geometric means of individual studies vary, mainly within the range 0.2-1 h-1 . Air-change rates also vary with time in residences. Factors influencing the air-change rate include weather (indoor-outdoor temperature difference and wind speed), the leakiness of the building envelope, and, when present, operation of mechanical ventilation systems. Occupancy-associated factors are also important, including window opening, induced exhaust from flued combustion, and use of heating and cooling systems. Empirical and methodological challenges remain to be effectively addressed. These include clarifying the time variation of air-change rates in residences during occupancy and understanding the influence of time-varying air-change rates on tracer-gas measurement techniques. Important opportunities are available to improve understanding of air-change rates and interzonal flows as factors affecting the source-to-exposure relationships for indoor air pollutants.

With the rapid development of the real estate industry in China, urban air quality is inevitably affected. By using data of Chinese cities located in the Yangtze River Delta from 2009 to 2018, this paper is aim at examining the casual impact of house prices on air quality. By considering the endogenous problems, in this study, first, the birth rate of the previous six years and the area of state-owned land supply per capita in the previous year are taken as instrumental variables of house price. Second, the two-stage least squares method is used to assess the causal impact of house price on air quality. The findings of this study show that there is no significant relationship between urban house prices and air quality, and these results are obtained without considering the endogenous problem. While, after considering the endogenous problem, urban house prices showed a significant negative effect on overall air quality, especially for low administrative level cities. The increase in house prices has hindered the improvement of air quality mainly through the blind-scale expansion of real estate development investments and the inhibitory effect of innovation. [ABSTRACT FROM AUTHOR]

We investigate source characteristics and emission dynamics of volatile organic compounds (VOCs) in a single-family house in California utilizing time- and space-resolved measurements. About 200 VOC signals, corresponding to more than 200 species, were measured during 8 weeks in summer and five in winter. Spatially resolved measurements, along with tracer data, reveal that VOCs in the living space were mainly emitted directly into that space, with minor contributions from the crawlspace, attic, or outdoors. Time-resolved measurements in the living space exhibited baseline levels far above outdoor levels for most VOCs; many compounds also displayed patterns of intermittent short-term enhancements (spikes) well above the indoor baseline. Compounds were categorized as "high-baseline" or "spike-dominated" based on indoor-to-outdoor concentration ratio and indoor mean-to-median ratio. Short-term spikes were associated with occupants and their activities, especially cooking. High-baseline compounds indicate continuous indoor emissions from building materials and furnishings. Indoor emission rates for high-baseline species, quantified with 2-hour resolution, exhibited strong temperature dependence and were affected by air-change rates. Decomposition of wooden building materials is suggested as a major source for acetic acid, formic acid, and methanol, which together accounted for ~75% of the total continuous indoor emissions of high-baseline species.

The smoking ban is not working in some entertainment venues in China. PM2.5 pollution induced by cigarette smoking in these places is still unknown. In this study, we took mahjong clubs as target places, monitored the real-time PM2.5 concentration, and recorded on-site inspection information to investigate the PM2.5 pollution characteristics induced by cigarette smoking. In occupied and smoking rooms, the geomean and median values of PM2.5 concentration were 276 and 347 μg/m3. The number of smoking persons in room is the dominant factor to enhance PM2.5 levels. For each additional person smoking in the room, PM2.5 increased by 32% (95% CI: 31%, 33%). Regarding adjacent nonsmoking rooms, PM2.5 increased due to the air penetration from smoking rooms and the increase trend usually had a lag time of 20 minutes. The geomean values of PM2.5 concentrations were 109 μg/m3 in the nonsmoking and occupied rooms and 148 μg/m3 in the vacant rooms. To close the door of the room is the most effective measure to alleviate the PM2.5 penetration. The geomean values of 24-hour and annual average excess exposure concentration if spending 5 hours/day and 2 days/week in mahjong club were 32.1 and 9.2 μg/m3, respectively; both exceeded the World Health Organization's air quality guidelines, 15 and 5 μg/m3, respectively. Our results revealed severe PM2.5 pollution and exposure risk by cigarette smoking in entertainment venues, as well as the penetration effect on adjacent nonsmoking areas. The smoking bans should be strictly enforced in entertainment venues, and the setting of smoking areas in indoor public places should be scientific to avoid diffusion into nonsmoking areas. [ABSTRACT FROM AUTHOR]

We performed a cross‐sectional survey of 2143 female students in a university in Tianjin, China regarding perceived air quality (PAQ) and sick building syndrome (SBS) symptoms in the student dormitory. The prevalence of general, mucosal, and skin symptoms was 22.1%, 21.9%, and 26.3%, respectively. The three most prevalent PAQ complaints were "dry air" (48.9% often), "stuffy odor" (18.2%), and "other unpleasant odors" (5.1%), and they were significant risk factors for 11–12 out of 12 SBS symptoms (adjusted odds ratios [AOR]: 1.6–5.8). Survey data of 1471 undergraduates, whose dorms were of uniform layout and furnishing, were used to further investigate the influences of occupancy level and occupant behaviors on PAQ and SBS symptoms. Frequent use of air freshener/perfume was a significant risk factor for "dry air," less frequent room cleaning and higher occupancy density were significant risk factors for "stuffy odor," and less natural ventilation was a significant risk factor for both "stuffy odor" and "pungent odor." These factors were also significantly associated with some SBS symptoms. In particular, the use of air freshener/perfume exhibited a significant dose–response pattern with "fatigue" (sometimes: AOR 1.3; often: AOR 2.0) and with "irritated, stuffy, or runny nose" (sometimes: AOR 1.6; often: AOR 2.2). [ABSTRACT FROM AUTHOR]

We explored the importance of inhaled air temperature on thermal comfort, perceived air quality, acute non‐clinical health symptoms, and physiological responses. Sixteen subjects stayed in a stainless‐steel chamber for 90 min. They experienced four conditions with two inhaled air temperatures of 22 and 30°C and two ambient temperatures of 22 and 30°C in a 2 × 2 design. They wore breathing masks covering their mouth and nose to control the inhaled air temperature; the air was provided from an adjacent twin stainless‐steel chamber. The subjects evaluated thermal conditions and health symptoms on visual‐analogue scales. Skin temperature and electrocardiography were recorded. Whole‐body thermal sensation and skin temperature did not change when the temperature of inhaled air was changed. Perceived air quality was significantly improved when subjects sat in the chamber at 30°C and inhaled air with a temperature of 22°C; under these conditions lip and throat dryness were significantly reduced. The lower inhaled air temperature increased time‐domain heart rate variability indicators and decreased heart rate and the LF/HF ratio, suggesting that the parasympathetic nervous system was activated and the sympathetic nervous system was suppressed. [ABSTRACT FROM AUTHOR]

Airborne transmission of infectious diseases through air travel has become a major concern, especially during the COVID‐19 pandemic. The flying public and crew members have long demanded better air quality and thermal comfort in commercial airliner cabins. This paper reviewed studies related to the airliner cabin air environment that have been published in scientific journals since 2000, to understand the state‐of‐the‐art in cabin air environment design and the efforts made to improve this environment. In this critical review, this paper discusses the challenges and opportunities in studying the cabin air environment. The literature review concluded that current environmental control systems for airliner cabins have done little to stop the airborne transmission of infectious diseases. There were no reports of significant air quality problems in cabins, although passengers and crew members have complained of some health‐related issues. The air temperature in cabins needs to be better controlled, and therefore, better thermal comfort models for airliners should be developed. Low humidity is a major complaint from passengers and crew members. Gaspers are used by passengers to adjust thermal comfort, but they do not improve air quality. Various personalized and displacement ventilation systems have been developed to improve air quality and thermal comfort. Air cleaning technologies need to be further developed. Good tools are available for designing a better cabin air environment. [ABSTRACT FROM AUTHOR]

Classrooms are often under‐ventilated, posing risks for airborne disease transmission as schools have reopened amidst the COVID‐19 pandemic. While technical solutions to ensure adequate air exchange are crucial, this research focuses on teachers' perceptions and practices that may also have important implications for achieving a safe classroom environment. We report on a (pre‐pandemic) survey of 84 teachers across 11 California schools, exploring their perceptions of environmental quality in relation to monitored indoor environmental quality (IEQ) data from their classrooms. Teachers were not educated regarding mechanical ventilation. Errors in HVAC system installation and programming contributed to misunderstandings (because mechanical ventilation was often not performing as it should) and even occasionally made it possible for teachers to turn off the HVAC fan (to reduce noise). Teachers did not accurately perceive (in)sufficient ventilation; in fact, those in classrooms with poorer ventilation were more satisfied with IEQ, likely due to more temperature fluctuations when ventilation rates were higher combined with occupants' tendency to conflate perceptions of air quality and temperature. We conclude that classroom CO2 monitoring and teacher education are vital to ensure that teachers feel safe in the classroom and empowered to protect the health of themselves and their students. [ABSTRACT FROM AUTHOR]

A FAVORABLE COMPARISON WITH AIRCRAFT-SPECIFIC LIMITS DOES NOT ASSURE ACCEPTABILITY Chen et al. suggest that the favorable comparison of aircraft data to aircraft design standards implies acceptability. 5 The aircraft limit should be lower than that for ground-based applications; because, in operation, the aircraft environment is reduced pressure, which increases susceptibility to hypoxia. Keywords: air quality; aircraft; exposure limits; fumes; marker compounds; thermal environment EN air quality aircraft exposure limits fumes marker compounds thermal environment 1 4 4 03/02/22 20220201 NES 220201 CONFLICTS OF INTEREST The author is employed in the safety, health, and security department of a union, which represents nearly 50 000 flight attendants at 17 US airlines (Association of Flight Attendants, AFL-CIO). It is understandable that they did not cite a UFP limit in table 1 because there are no such limits currently, whether on or off aircraft.13 Notably, though, a World Health Organization guideline defines a count of >20 000 particles/cm SP 3 sp (1 h mean) as "high",14 which is considerably lower than some of the aircraft data. [Extracted from the article]

We evaluated the impact of the lockdown restriction measures in the Paris area on the variation of in‐vehicle ultrafine particle (UFP) and black carbon (BC) concentrations between the pre‐ and post‐lockdown period and professional drivers' working conditions and practices. The study was conducted with 33 taxi drivers. UFP and BC were measured inside their vehicles with DiSCmini® and microAeth®, respectively, on two typical working days pre‐ and post‐lockdown. Job characteristics were self‐reported. Our results showed that post‐lockdown, both the number of clients and journey duration significantly decreased. Taxi drivers opened their windows significantly more and reduced the use of air recirculation. UFP decreased significantly by 32% and BC by 31% post‐lockdown, with a weaker positive correlation compared to pre‐lockdown. The reduction of in‐vehicle UFP was due mainly to the reduction of traffic flow and ventilation settings, though the latter probably varied according to traffic conditions. The variation of in‐vehicle BC also tended to be related to the decrease in traffic flow post‐lockdown. We emphasize the role of traffic emissions on in‐vehicle air pollution and that preventive measures such ventilation settings would help to minimize the exposure of professional drivers and passengers to air pollutants. [ABSTRACT FROM AUTHOR]

Furthermore, the aircraft hydraulic reservoir vent is connected to the cabin air ventilation system, making it possible for hydraulic oil aerosols to enter cabin air SP 118 sp ; they also have other sources as shown by Schuchardt et al. SP 89 sp . change to The presence of a range of SVOCs in aircraft cabin and cockpit air has been recorded in several studies SP 69,80,85,89,112-117 sp . The cabin air supply in most jet aircraft is obtained by extraction of heated and compressed bleed air from the jet engine cores, prior to mixing with filtered recycled cabin air. The cabin air supply in most jet aircraft is obtained by extraction of heated and compressed bleed air from the jet engine cores, prior to mixing with filtered recycled cabin air. [Extracted from the article]

Portable ultrasonic humidifiers are frequently used in heating rooms to ease air dryness. However, it has also posed serious health concerns such as "humidifier fever" because the bioaerosol concentration and community in the humidified space may alter quickly before the occupants could even notice. We compared the microbial proliferation rates in the humidifiers' reservoirs filled with three commonly used water types and investigated the impacts of the ultrasonic humidifiers on the temporal concentration, size distribution, and community variations of indoor bacterial and fungal aerosols during two‐week humidification. The concentration of indoor bacterial aerosols increased exponentially, concentrating in the respiratory size ranges (≤1.1 µm), and was proportional to the humidification level, which soon exceeded 1000 CFU/m3 in one week (at RH = 70%), while the fungal concentration always remained low (≤177 CFU/m3). The indoor bioaerosol community, significantly associated with the humidifier water, was substantially distorted after humidification and dominated by the pathogenic Pseudomonas spp. (40.50%), Brevundimonas spp. (3.02%), Acinetobacter spp. (0.98%) and Legionella spp. (0.69%). Our results show that ultrasonic humidification contaminates indoor air by raising bacterial concentrations and fueling the pathogenic genera. To minimize the exposure risks, occupants should avoid long‐term and excessive humidification (RH ≥ 70%) and clean the ultrasonic humidifier weekly. [ABSTRACT FROM AUTHOR]

Chinese civil aviation regulations part 25 airworthiness standards for transport aircraft, order of CAAC no. 23 of 2017; 2017. The Table 1 below provides the most up to date overview of standards and guidelines describing requirements for achieving high air quality in aircraft cabins on commercial flights. [Extracted from the article]

Carbon dioxide (CO2) is an important environmental parameter in aircraft cabins. To understand the most recent, real‐time CO2 concentration levels and their key influencing factors in aircraft cabins, we conducted in‐flight measurements of 52 randomly selected commercial flights with different aircraft types and durations from August 2017 to August 2019. The spatial temporal characteristics of CO2 concentrations on board were analyzed and summarized. For the flight time scale, the CO2 concentrations during the boarding phase (1680 ± 558 ppmv) were notably higher than that in other phases, whereas the condition of the cruising phase was the lowest in most flights. The flight average CO2 concentrations of the cruising phase were 1253 ± 164 ppmv, and the corresponding estimated outside airflow rates were 6.2 ± 1.3 L/s/p in the economy class across all flights. Single‐aisle and twin‐aisle flights did not show noticeable differences for the same phases. Relatively uniform CO2 concentrations were observed at different positions of the same class. By comparing the results of this study with those previously reported, CO2 concentrations showed a slightly decreasing trend over the last 30 years. This suggested a slightly increased ventilation rate and potentially superior air quality on board. [ABSTRACT FROM AUTHOR]

Space is a resource that is constantly being depleted, especially in mega‐cities. Underground workspaces (UGS) are increasingly being included in urban plans and have emerged as an essential component of vertical cities. While progress had been made on the engineering aspects associated with the development of high‐quality UGS, public attitudes toward UGS as work environments (ie, the public's design concerns with UGS) are relatively unknown. Here, we present the first large‐scale study examining preferences and attitudes toward UGS, surveying close to 2000 participants from four cities in three continents (Singapore, Shanghai, London, and Montreal). Contrary to previous beliefs, air quality (and not lack of windows) is the major concern of prospective occupants. Windows, temperature, and lighting emerged as additional important building performance aspects for UGS. Early adopters (ie, individuals more willing to accept UGS and thus more likely to be the first occupants) across all cities prioritized air quality. Present results suggest that (perceived) air quality is a key building performance aspect for UGS that needs to be communicated to prospective occupants as this will improve their attitudes and views toward UGS. This study highlights the importance of indoor air quality for the public. [ABSTRACT FROM AUTHOR]

To investigate the need of allergic population for indoor environment quality, exposure effects of poor air quality on subjects with respiratory allergies were compared with those on healthy people, including perceptual responses, health symptoms, mental performance, and physiological responses. The experimental intervention was with and without ventilation at thermally neutral rooms, creating two exposure conditions indicated by CO2 concentration ranges of 502 to 3297 ppm (2438 ± 1527 ppm) and 517 to 5687 ppm (3615 ± 1527 ppm). 63 subjects (32 allergic subjects and 31 non‐allergic subjects) were exposed to both conditions for 3 hours. The main results suggested that, compared with healthy people, people with respiratory allergy seem to be more sensitive or less acceptable to reduced air quality polluted by occupants during instantaneous exposure. Besides, the allergic group performed worse in cognitive tests than non‐allergic group. After 3 hours of continuous exposure, people with respiratory allergy reported stronger intensity of respiratory irritations and seemed to suffer more inflammation indicated by a higher level of interleukin 1L‐1β. [ABSTRACT FROM AUTHOR]

We reviewed 47 documents published 1967–2019 that reported measurements of volatile organic compounds (VOCs) on commercial aircraft. We compared the measurements with the air quality standards and guidelines for aircraft cabins and in some cases buildings. Average levels of VOCs for which limits exist were lower than the permissible levels except for benzene with average concentration at 5.9 ± 5.5 μg/m3. Toluene, benzene, ethylbenzene, formaldehyde, acetaldehyde, limonene, nonanal, hexanal, decanal, octanal, acetic acid, acetone, ethanol, butanal, acrolein, isoprene and menthol were the most frequently measured compounds. The concentrations of semi‐volatile organic compounds (SVOCs) and other contaminants did not exceed standards and guidelines in buildings except for the average NO2 concentration at 12 ppb. Although the focus was on VOCs, we also retrieved the data on other parameters characterizing cabin environment. Ozone concentration averaged 38 ppb below the upper limit recommended for aircraft. The outdoor air supply rate ranged from 1.7 to 39.5 L/s per person and averaged 6.0 ± 0.8 L/s/p (median 5.8 L/s/p), higher than the minimum level recommended for commercial aircraft. Carbon dioxide concentration averaged 1315 ± 232 ppm, lower than what is permitted in aircraft and close to what is permitted in buildings. Measured temperatures averaged 23.5 ± 0.8°C and were generally within the ranges recommended for avoiding thermal discomfort. Relative humidity averaged 16% ± 5%, lower than what is recommended in buildings. [ABSTRACT FROM AUTHOR]

Heating, ventilating, and air‐conditioning (HVAC) systems usually supply air, which is a mixture of fresh air from the outdoor environment, and return air from rooms via the ventilation ductwork. This air reduces the heat load and cost impact of air conditioning using outdoor air. This recirculation of room air in air‐conditioning systems is reasonable in terms of energy saving; however, the deterioration of air quality might be a concern because of the recirculation of contaminated room air. Here, we numerically investigate the effect of pollutant recirculation/return on the formation of concentration distributions of local pollutants in indoor environments when the mixing ratio of recirculated air in the HVAC system changes. We discuss the detailed structure of the formation mechanism of local pollutant concentration distributions using various indices for indoor ventilation efficiency in simplified room models. Among the indices, visitation frequency and net escape probability are the ones that directly assist in evaluating the recirculation/return characteristics of indoor pollutants. As a result, when the proportion of air that is recirculated becomes large, the number of pollutants returning to a target local domain, the visitation frequency, increases exponentially, and the net escape probability—which directly expresses the probability of pollutant discharged from the target domain—is close to zero. [ABSTRACT FROM AUTHOR]

The indoor environment influences occupants' health. From March 1, 2018, to February 28, 2019, we continuously monitored indoor temperature (T), relative humidity (RH), and CO2 concentration in bedrooms via an online system in 165 residences that covered all five climate zones of China. Meanwhile, we asked one specific occupant in each home to complete questionnaires about perceived air quality and sick building syndrome (SBS) symptoms at the end of each month. Higher CO2 concentration was significantly associated with a higher percentage of perceived stuffy odor and skin SBS symptoms. Higher relative humidity was associated with higher percentage of perceived moldy odor and humid air, while lower RH was associated with a higher percentage of perceived dry air. Occupants who lived in residences with high RH were less likely to have mucosal and skin SBS symptoms (adjusted odds ratio (AOR): 0.73–0.78). However, the benefit of high humidity for perceived dry air and skin dryness symptoms is weaker if there is a high CO2 concentration level. [ABSTRACT FROM AUTHOR]

This field study aimed to investigate naturally ventilated bedroom environment and its effects on subjective perception and sleep quality. Totally, 104 healthy subjects living in urban areas of Beijing participated in the study for one night during transition seasons. Bedroom environment parameters, including temperature, relative humidity, and CO2 concentration, were recorded before and during sleep. Objective sleep quality was measured by Fitbit Alta 2, a wrist‐type actigraphy sensor. Subjective assessments were collected by paper‐based questionnaires on sleep quality and environmental perceptions. The results showed that neutral temperature for waking state (before sleep) was estimated to be 23.8°C while for sleep state it was 26.5°C. Furthermore, pre‐sleep thermal sensation vote was found to be positively correlated with deep sleep percentage. Indoor air quality was correlated with sleep quality as indicated by statistically significant correlations between odor intensity assessment, air quality acceptability, average nightly CO2 concentration, and measures of sleep quality. For naturally ventilated bedrooms during transition seasons with a mild outdoor climate, present findings suggest that a bedroom with slightly warm pre‐sleep environment than neutral, and with high ventilation as indicated by low indoor CO2 concentration, could be beneficial for sleep quality of residents. [ABSTRACT FROM AUTHOR]

Recently, studies suggest that the average indoor temperature is typically >30°C and that the maximum temperature can reach 37.5°C in hot‐humid areas. However, the effects caused by increasing the humidity at high indoor temperatures are not clear. In this study, twelve female and twelve male subjects were exposed to different operative temperature (26.6, 30.6, and 37.4°C) and relative humidity (50% and 70%) in a climate chamber. Data concerning thermal sensation, perceived air quality, and Sick Building Syndrome (SBS) were collected during 190‐min‐long exposure to each thermal condition. Heart rate, respiration rate, respiratory ventilation rate, mean skin temperature, and eardrum temperature were measured. It was found that increasing the relative humidity from 50% to 70% at 26 and 30°C had no significant effects on the physiological responses, thermal comfort, perceived air quality, or SBS symptoms of the subjects. However, when the temperature was elevated to 37°C, the heart rate, respiration rate, respiratory ventilation rate, mean skin temperature, and eardrum temperature increased significantly as a result of the increase in the relative humidity from 50% to 70%. The subjects felt hotter and more uncomfortable, and they found indoor air quality was more difficult to accept. The subjects are acclimatized to hot environments and more tolerant to heat. Therefore, the results are applicable to the acclimated people living in hot‐humid climate. [ABSTRACT FROM AUTHOR]

This study investigates the performance of two systems: personalized ventilation (PV) and ductless personalized ventilation (DPV). Even though the literature indicates a compelling performance of PV, it is not often used in practice due to its impracticality. Therefore, the present study assesses the possibility of replacing the inflexible PV with DPV in office rooms equipped with displacement ventilation (DV) in the summer season. Numerical simulations were utilized to evaluate the inhaled concentration of pollutants when PV and DPV are used. The systems were compared in a simulated office with two occupants: a susceptible occupant and a source occupant. Three types of pollution were simulated: exhaled infectious air, dermally emitted contamination, and room contamination from a passive source. Results indicated that PV improved the inhaled air quality regardless of the location of the pollution source; a higher PV supply flow rate positively impacted the inhaled air quality. Contrarily, the performance of DPV was highly sensitive to the source location and the personalized flow rate. A higher DPV flow rate tends to decrease the inhaled air quality due to increased mixing of pollutants in the room. Moreover, both systems achieved better results when the personalized system of the source occupant was switched off. [ABSTRACT FROM AUTHOR]

Our focus was on volatile organic compounds (VOCs), but we also reported the measurements of other parameters characterizing the aircraft cabin environment reported in the identified papers. One reason why we reported guideline values for other environments than aircraft is the lack of such guideline values for aircraft cabins because, for decades, stakeholders have been unable to agree on such values. Our purpose was not to judge whether the measured conditions regarding air quality in aircraft cabins could be rated as acceptable or not acceptable following recommendations included in the occupational guidelines and aircraft standards. [Extracted from the article]

Microbes in buildings have attracted extensive attention from both the research community and the general public due to their close relationship with human health. However, there still lacks comprehensive information on the indoor exposure level of microbes in China. This study systematically reviews exposure levels, the community structures, and the impact factors of airborne bacteria and fungi in residences, schools, and offices in China. We reviewed the major literature databases between 1980 and 2019 and selected 55 original studies based on a set of criteria. Results show that the concentration of indoor bacteria varies from 72.5 to 7500 CFU/m3, with a median value of 1000 CFU/m3, and the concentration of fungi varies from 12 to 9730 CFU/m3, with a median value of 526 CFU/m3. The concentration level of microbes varies in different climate zones, with higher bacterial concentrations in the severe cold zone, and higher fungal concentrations in the hot summer and warm winter zone. Among different buildings, classrooms have the highest average bacteria and fungi levels. This review reveals that a unified assessment system based on health effects is needed for evaluating the exposure levels of bacteria and fungi. [ABSTRACT FROM AUTHOR]

In this paper, we provide a detailed description of the application of passive sampling with Carbopack X tubes followed by thermal desorption‐gas chromatography‐mass spectrometry (TD‐GC‐MS) to determine the concentrations of volatile organic compounds (VOCs) in different school environments. The main objective of the study was to monitor VOCs in seven indoor and three outdoor environments at a school in Tarragona, Spain. However, in order to obtain more accurate information, it was necessary to determine the experimental diffusive uptake rates of the target VOCs in indoor settings through parallel passive and active sampling in one classroom. The results showed experimental diffusive uptake rates in the range of 0.38 mL min‐1 and 0.95 mL min‐1 with RSD % below 5% for up to 44 VOCs. The monitoring results showed that ethanol (23.84‐83.16 µg m‐3) and isopropyl alcohol (5.42‐25.92 µg m‐3) were the most common compounds found in indoor environments, with cleaning products as the main emission source. The VOCs i‐pentane and n‐pentane were found at the highest concentrations in the three sampling sites set in the school's playground, and their concentrations were strictly related to combustion processes from automobile traffic. [ABSTRACT FROM AUTHOR]

This study investigated whether adjusting clothing to remain in neutral thermal comfort at moderately elevated temperature is capable of avoiding negative effects on perceived acute subclinical health symptoms, comfort, and cognitive performance. Two temperatures were examined: 23°C and 27°C. Twelve subjects were able to remain thermally comfortable at both temperatures by adjusting their clothing. They rated the physical environment, their comfort, the intensity of acute subclinical health symptoms, and their mental load, and they performed a number of cognitive tasks. Their physiological reactions were monitored. Their performance of several tasks was significantly worse at 27°C, and they reported increased mental load at this temperature. Skin temperature and humidity and respiration rate were higher, while blood oxygen saturation (SpO2) and pNN50 were lower at this temperature, the latter indicating increased stress. It is inferred that the observed physiological responses were mainly responsible for the negative effects on performance, as the subjects did not indicate any increased intensity of acute subclinical health symptoms although perceived air quality was worse at the higher temperature. The present results suggest that moderately elevated temperatures should be avoided even if thermal comfort can be achieved, as it may lead to reduced performance. [ABSTRACT FROM AUTHOR]

This study evaluated the interrelations between indoor and outdoor bioaerosols in a bedroom under a living condition. Two wideband integrated bioaerosol sensors were utilized to measure indoor and outdoor particulate matter (PM) and fluorescent biological airborne particles (FBAPs), which were within a size range of 0.5‐20 μm. Throughout this one‐month case study, the median proportion of FBAPs in PM by number was 19% (5%; the interquartile range, hereafter) and 17% (3%) for indoors and outdoors, respectively, and those by mass were 78% (12%) and 55% (9%). According to the size‐resolved data, FBAPs dominated above 2 and 3.5 μm indoors and outdoors, respectively. Comparing indoor upon outdoor ratios among occupancy and window conditions, the indoor FBAPs larger than 3.16 μm were dominated by indoor sources, while non‐FBAPs were mainly from outdoors. The occupant dominated the indoor source of both FBAPs and non‐FBAPs. Under awake and asleep, count‐ and mass‐based mean emission rates were 45.9 and 18.7 × 106 #/h and 5.02 and 2.83 mg/h, respectively. Based on indoor activities and local outdoor air quality in Singapore, this study recommended opening the window when awake and closing it during sleep to lower indoor bioaerosol exposure. [ABSTRACT FROM AUTHOR]

Monitoring improved cookstove adoption and usage in developing countries can help anticipate potential health and environmental benefits that may result from household energy interventions. This study explores stove‐usage monitor (SUM)‐derived usage data from field studies in China (52 stoves, 1422 monitoring days), Honduras (270 stoves, 630 monitoring days), India (19 stoves, 565 monitoring days), and Uganda (38 stoves, 1007 monitoring days). Traditional stove usage was found to be generally similar among four seemingly disparate countries in terms of cooking habits, with average usage of between 171 and 257 minutes per day for the most‐used stoves. In Honduras, where survey‐based usage data were also collected, there was only modest agreement between sensor data and self‐reported user data. For Indian homes, we combined stove‐usage data with a single‐zone Monte Carlo box model to estimate kitchen‐level PM2.5 and CO concentrations under various scenarios of cleaner cookstove adoption. We defined clean cookstove performance based on the International Standards Organization (ISO) voluntary guidelines. Model results showed that even with 75% displacement of traditional stoves with the cleanest available stove (ISO tier‐5), World Health Organization 24 hours PM2.5 standards were exceeded in 96.4% of model runs, underscoring the importance of full displacement. [ABSTRACT FROM AUTHOR]

This paper reviews the published literature on indoor thermal environment and air quality in Chinese‐style residential kitchens (CRKs). The paper first discusses typical characteristics of CRKs, including kitchen layout, cooking methods, and ventilation systems used. Next, the paper describes the current state of the indoor thermal environment and air quality in CRKs. Finally, this paper summarizes measures to control and improve the environment inside CRKs. The results indicate that the indoor environment of CRKs is too hot in summer and exhibits a large vertical temperature difference. No appropriate model was available for accurately evaluating the thermal environment in CRKs. At the same time, CRKs are highly polluted by COx, NOx, TVOC, and particulate matter (PM). Although existing exhaust hoods could improve the indoor environment to some extent, the use of a combined exhaust, make‐up air, and air‐conditioning system should be considered to provide a comfortable and healthy environment in CRKs. [ABSTRACT FROM AUTHOR]

The aim of this study was to (a) develop a method for converting particle number concentrations (PNC) obtained by Dylos to PM2.5 mass concentrations, (b) compare this conversion with similar methods available in the literature, and (c) compare Dylos PM2.5 obtained using all available conversion methods with gravimetric samples. Data were collected in multiple residences in three European countries using the Dylos and an Aerodynamic Particle Sizer (APS, TSI) in the Netherlands or an optical particle counter (OPC, GRIMM) in Greece. Two statistical fitted curves were developed based on Dylos PNC and either an APS or an OPC particle mass concentrations (PMC). In addition, at the homes of 16 volunteers (UK and Netherlands), Dylos measurements were collected along with gravimetric samples. The Dylos PNC were transformed to PMC using all the fitted curves obtained during this study (and three found in the literature) and were compared with gravimetric samples. The method developed in the present study using an OPC showed the highest correlation (Pearson (R) = 0.63, Concordance (ρc) = 0.61) with gravimetric data. The other methods resulted in an underestimation of PMC compared to gravimetric measurements (R = 0.65‐0.55, ρc = 0.51‐0.24). In conclusion, estimation of PM2.5 concentrations using the Dylos is acceptable for indicative purposes. [ABSTRACT FROM AUTHOR]

Indoor environmental quality (IEQ) has become an important component of green building certification schemes. While green buildings are expected to provide enhanced IEQ, higher occupant satisfaction, and less risks of occupant health when compared with non‐green buildings, the literature suggests inconsistent evidence due to diverse research design, small sample size, and weak statistical analysis. This study compared several outcomes pertinent to IEQ performance in green and non‐green office buildings in Singapore. Adopting a cross‐sectional study design, objective measurements were taken in eight green and six non‐green buildings, and satisfaction and acute health symptom risks of 367 occupants were obtained. Green buildings exhibited lower concentration of PM2.5, bacteria, and fungi and maintained temperature and humidity more consistently compared to non‐green counterparts. The mean ratings for satisfaction with temperature, humidity, lighting level, air quality, and indoor environment were higher in green buildings (with statistical significance P < 0.05). There was statistically significant reduction in risk of occupants having headache, unusual fatigue, and irritated skin in green buildings. Although matching of buildings and occupant characteristics, survey participation bias, and sampling duration (a 1‐week snapshot) of IEQ monitoring remain as limitations, this study offered positive association of green buildings with qualitatively and quantitatively measured performance of IEQ. [ABSTRACT FROM AUTHOR]

Abstract: The ability to inexpensively monitor PM2.5 to identify sources and enable controls would advance residential indoor air quality (IAQ) management. Consumer IAQ monitors incorporating low‐cost optical particle sensors and connections with smart home platforms could provide this service if they reliably detect PM2.5 in homes. In this study, particles from typical residential sources were generated in a 120 m3 laboratory and time‐concentration profiles were measured with 7 consumer monitors (2‐3 units each), 2 research monitors (Thermo pDR‐1500, MetOne BT‐645), a Grimm Mini Wide‐Range Aerosol Spectrometer (GRM), and a Tapered Element Oscillating Microbalance with Filter Dynamic Measurement System (FDMS), a Federal Equivalent Method for PM2.5. Sources included recreational combustion (candles, cigarettes, incense), cooking activities, an unfiltered ultrasonic humidifier, and dust. FDMS measurements, filter samples, and known densities were used to adjust the GRM to obtain time‐resolved mass concentrations. Data from the research monitors and 4 of the consumer monitors—AirBeam, AirVisual, Foobot, Purple Air—were time correlated and within a factor of 2 of the estimated mass concentrations for most sources. All 7 of the consumer and both research monitors substantially under‐reported or missed events for which the emitted mass was comprised of particles smaller than 0.3 μm diameter. [ABSTRACT FROM AUTHOR]

Abstract: Building ventilation rates and indoor airflow conditions influence occupants’ exposure to indoor air pollutants. By making time‐ and space‐resolved measurement of 3 inert tracers steadily released in a single‐family house in California for 8 weeks in summer and 5 weeks in winter, this study quantifies the air change rate of the living zone with 2‐hour time resolution; estimates airflow rates between the living zone, attic, and crawlspace; and characterizes mixing of air in the split‐level living space. Occupant behaviors altered the air change rates, primarily through opening windows and secondarily through operating the heating system. The air change rate correlated with the number of window openings, accounting for 57% of the variability measured across 2 seasons. There were substantial upward interzonal airflows between the crawlspace, living zone, and attic; downward airflows were negligible by comparison. More than 70% of the airflow entering the living zone in the winter and at night during summer came through the crawlspace, rather than directly from outdoors. The airflow from the living zone to the attic increased with the attic‐outdoor temperature difference, indicating that buoyancy associated with solar heating of the attic induced airflow from the living zone, increasing the air change rate. [ABSTRACT FROM AUTHOR]

Abstract: Strong evidence suggests that clothing serves as a reservoir of chemical pollutants and particles, including bioaerosols, which may have health significance. However, little is known about the role that clothing may play as a transport vector for inhaled airborne particles. Here, we contribute toward bridging the knowledge gap by conducting experiments to investigate clothing release fraction (CRF), determined as the size‐dependent ratio of released to deposited particulate matter in the diameter range 0.5‐10 μm. In a fully controlled chamber with low background particle levels, we deployed a programmable robot to reproducibly quantify the size‐dependent CRF as a function of motion type and intensity, dust loadings, and activity duration. On average, 0.3%‐3% of deposited particles were subsequently released with fabric motion, confirming that clothing can act as a vehicle for transporting airborne particles. The CRF increased with the vigor of movement and with dust loading. Rubbing and shaking the fabric were more effective than fabric stretching in resuspending particles. We also found that most of the release happened quickly after the onset of the resuspension activity. Particle size substantially influenced the CRF, with larger particles exhibiting higher values. [ABSTRACT FROM AUTHOR]

Abstract: High‐efficiency particulate air (HEPA) filtration in combination with an electrostatic precipitator (ESP) can be a cost‐effective approach to reducing indoor particulate exposure, but ESPs produce ozone. The health effect of combined ESP‐HEPA filtration has not been examined. We conducted an intervention study in 89 volunteers. At baseline, the air‐handling units of offices and residences for all subjects were comprised of coarse, ESP, and HEPA filtration. During the 5‐week long intervention, the subjects were split into 2 groups, 1 with just the ESP removed and the other with both the ESP and HEPA removed. Each subject was measured for cardiopulmonary risk indicators once at baseline, twice during the intervention, and once 2 weeks after baseline conditions were restored. Measured indoor and outdoor PM2.5 and ozone concentrations, coupled with time‐activity data, were used to calculate exposures. Removal of HEPA filters increased 24‐hour mean PM2.5 exposure by 38 (95% CI: 31, 45) μg/m3. Removal of ESPs decreased 24‐hour mean ozone exposure by 2.2 (2.0, 2.5) ppb. No biomarkers were significantly associated with HEPA filter removal. In contrast, ESP removal was associated with a −16.1% (−21.5%, −10.4%) change in plasma‐soluble P‐selectin and a −3.0% (−5.1%, −0.8%) change in systolic blood pressure, suggesting reduced cardiovascular risks. [ABSTRACT FROM AUTHOR]

Abstract: In low‐resource settings, there is a need to develop models that can address contributions of household and outdoor sources to population exposures. The aim of the study was to model indoor PM2.5 using household characteristics, activities, and outdoor sources. Households belonging to participants in the Mother and Child in the Environment (MACE) birth cohort, in Durban, South Africa, were randomly selected. A structured walk‐through identified variables likely to generate PM2.5. MiniVol samplers were used to monitor PM2.5 for a period of 24 hours, followed by a post‐activity questionnaire. Factor analysis was used as a variable reduction tool. Levels of PM2.5 in the south were higher than in the north of the city (P < .05); crowding and dwelling type, household emissions (incense, candles, cooking), and household smoking practices were factors associated with an increase in PM2.5 levels (P < .05), while room magnitude and natural ventilation factors were associated with a decrease in the PM2.5 levels (P < .05). A reasonably robust PM2.5 predictive model was obtained with model R2 of 50%. Recognizing the challenges in characterizing exposure in environmental epidemiological studies, particularly in resource‐constrained settings, modeling provides an opportunity to reasonably estimate indoor pollutant levels in unmeasured homes. [ABSTRACT FROM AUTHOR]

This study describes the size distribution and concentration of particles expelled by a portable, 3-L ultrasonic humidifier. The ultrasonic humidifier was filled with waters of varying mineral content and hardness. Aerosol size distributions were measured during 8 hours of humidifier operation in a typical bedroom. Humidifiers produced approximately 1.22 × 1010-2.50 × 1010 airborne particles per milliliter of water consumed, resulting in airborne particle concentrations of 3.01-5.91 × 104 #/cm3, with modes ranging between 109 and 322 nm in diameter. The emission rate of particles varied by water type from 1.02 × 109 to 2.27 × 109 #/s. Lower mineral waters produced fewer, smaller particles when compared to higher mineral waters. Chemical analyses of particles collected with a cascade impactor indicated that the minerals in emitted particles had the same relative mineral concentrations as the fill water. Our results demonstrate that ultrasonic humidifiers should be considered a source of inhalation exposure to minerals dissolved in water, and that the magnitude of exposure to inhalable particles will vary with water quality. [ABSTRACT FROM AUTHOR]

Dampness affects a substantial percentage of homes and is associated with increased risk of respiratory ailments; yet, the effects of dampness on indoor chemistry are largely unknown. We hypothesize that the presence of water-soluble gases and their aqueous processing alters the chemical composition of indoor air and thereby affects inhalation and dermal exposures in damp homes. Herein, we use the existing literature and new measurements to examine the plausibility of this hypothesis, summarize existing evidence, and identify key knowledge gaps. While measurements of indoor volatile organic compounds ( VOCs) are abundant, measurements of water-soluble organic gases ( WSOGs) are not. We found that concentrations of total WSOGs were, on average, 15 times higher inside homes than immediately outside (N = 13). We provide insights into WSOG compounds likely to be present indoors using peer-reviewed literature and insights from atmospheric chemistry. Finally, we discuss types of aqueous chemistry that may occur on indoor surfaces and speculate how this chemistry could affect indoor exposures. Liquid water quantities, identities of water-soluble compounds, the dominant chemistry, and fate of aqueous products are poorly understood. These limitations hamper our ability to determine the effects of aqueous indoor chemistry on dermal and inhalation exposures in damp homes. [ABSTRACT FROM AUTHOR]

Although many U.S. children spend time in child care, little information exists on exposures to airborne particulate matter (PM) in this environment, even though PM may be associated with asthma and other respiratory illness, which is a key concern for young children. To address this data gap, we measured ultrafine particles (UFP), PM2.5, PM10, and black carbon in 40 California child-care facilities and examined associations with potential determinants. We also tested a low-cost optical particle measuring device (Dylos monitor). Median (interquartile range) concentrations for indoor UFP, gravimetric PM2.5, real-time PM2.5, gravimetric PM10, and black carbon over the course of a child-care day were 14 000 (11 000-29 000) particles/cm3, 15 (9.6-21) μg/m3, 15 (11-23) μg/m3, 48 (33-73) μg/m3, and 0.43 (0.25-0.65) ng/m3, respectively. Indoor black carbon concentrations were inversely associated with air exchange rate (Spearman's rho = −.36) and positively associated with the sum of all Gaussian-adjusted traffic volume within a one-kilometer radius (Spearman's rho = .45) ( P-values <.05). Finally, the Dylos may be a valid low-cost alternative to monitor PM levels indoors in future studies. Overall, results indicate the need for additional studies examining particle levels, potential health risks, and mitigation strategies in child-care facilities. [ABSTRACT FROM AUTHOR]

The aim of this laboratory experiment was to study the effects of ventilation rate, and related changes in air quality, predominantly bioeffluents, on work performance, perceived indoor air quality, and health symptoms in a typical conditions of modern open-plan office with low material and equipment emissions. In Condition A, outdoor air flow rate of 28.2 l/s person ( CO2 level 540 ppm) was applied and in Condition B, outdoor air flow rate was 2.3 l/s person ( CO2 level 2260 ppm). CO2 concentration level was used as an indicator of bioeffluents. Performance was measured with seven different tasks which measure different cognitive processes. Thirty-six subjects participated in the experiment. The exposure time was 4 hours. Condition B had a weak negative effect on performance only in the information retrieval tasks. Condition B increased slightly subjective workload and perceived fatigue. No effects on health symptoms were found. The intensity of symptoms was low in both conditions. The experimental condition had an effect on perceived air quality and observed odor intensity only in the beginning of the session. Although the room temperature was controlled in both conditions, the heat was perceived to impair the performance more in Condition B. [ABSTRACT FROM AUTHOR]

The article discusses workshop to identify a modeling enterprise for studying the chemistry of indoor environments held in Washington, District of Columbia (D.C.). Topics discussed include impact of partitioning, phase change and chemical transformations on indoor air; indoor aerosol modeling and use of Monte Carlo simulations.

Residential endotoxin exposure is associated with protective and pathogenic health outcomes. Evaporative coolers, an energy-efficient type of air conditioner used in dry climates, are a potential source of indoor endotoxins; however, this association is largely unstudied. We collected settled dust biannually from four locations in homes with evaporative coolers (n=18) and central air conditioners (n=22) in Utah County, Utah ( USA), during winter (Jan-Apr) and summer (Aug-Sept), 2014. Dust samples (n=281) were analyzed by the Limulus amebocyte lysate test. Housing factors were measured by survey, and indoor temperature and relative humidity measures were collected during both seasons. Endotoxin concentrations ( EU/mg) were significantly higher in homes with evaporative coolers from mattress and bedroom floor samples during both seasons. Endotoxin surface loads ( EU/m2) were significantly higher in homes with evaporative coolers from mattress and bedroom floor samples during both seasons and in upholstered furniture during winter. For the nine significant season-by-location comparisons, EU/mg and EU/m2 were approximately three to six times greater in homes using evaporative coolers. A plausible explanation for these findings is that evaporative coolers serve as a reservoir and distribution system for Gram-negative bacteria or their cell wall components in homes. [ABSTRACT FROM AUTHOR]

Low ventilation rates ( VRs) in schools have been associated with absenteeism, poorer academic performance, and teacher dissatisfaction. We measured VRs in 37 recently constructed or renovated and mechanically ventilated U.S. schools, including LEED and EnergyStar-certified buildings, using CO2 and the steady-state, build-up, decay, and transient mass balance methods. The transient mass balance method better matched conditions (specifically, changes in occupancy) and minimized biases seen in the other methods. During the school day, air change rates ( ACRs) averaged 2.0±1.3 hour−1, and only 22% of classrooms met recommended minimum ventilation rates. HVAC systems were shut off at the school day close, and ACRs dropped to 0.21±0.19 hour−1. VRs did not differ by building type, although cost-cutting and comfort measures resulted in low VRs and potentially impaired IAQ. VRs were lower in schools that used unit ventilators or radiant heating, in smaller schools and in larger classrooms. The steady-state, build-up, and decay methods had significant limitations and biases, showing the need to confirm that these methods are appropriate. Findings highlight the need to increase VRs and to ensure that energy saving and comfort measures do not compromise ventilation and IAQ. [ABSTRACT FROM AUTHOR]