Indoor Air Quality Measurements Research Articles

COVID-19 Mitigation in a K-12 School Setting: A Case Study of Avenues: The World School in New York City.

In this case study, we describe a well-resourced private school in New York City that implemented COVID-19 mitigation measures based on public health expert guidance and the lessons learned from this process. Avenues opened in New York City in 2012 and has since expanded, becoming Avenues: The World School, with campuses in São Paulo, Brazil; Shenzhen, China; the Silicon Valley, California; and online. It offers education at 16 grade levels: 2 early learning years, followed by a prekindergarten through grade 12. We describe the mitigation measures that Avenues implemented on its New York campus. We compare COVID-19 case prevalence at the school with COVID-19 case positivity in New York City, as reported by the New York State Department of Health. We also compare the school's indoor air quality to ambient indoor air quality measures reported in the literature. The school's mitigation measures successfully reduced the prevalence of COVID-19 among its students, staff, and faculty. The school also established a consistently high level of indoor air quality safety through various ventilation mechanisms, designed to reduce common indoor air pollutants. The school received positive parent and community feedback on the policies and procedures it established, with many parents commenting on the high level of trust and quality of communication established by the school. The successful reopening provides useful data for school closure and reopening standards to prepare for future pandemic and epidemic events.

Indoor Air Quality Measurements in Enclosed Spaces Combining Activities with Different Intensity and Environmental Conditions

The impact of the COVID-19 pandemic has caused an increase in knowledge in certain fields such as human breathing and respiratory diseases. In the current study, enclosed-space characteristics were assessed due to the great debate generated because of the pandemic. Temperature, relative humidity, carbon dioxide (CO2) concentration, particulate matter (PM) concentration and cumulative particle concentration percentage per size fraction were measured in three buildings under the occurrence of activities with different intensity levels. For the measurements, Arduino UNO, Sensiron SCD30 and APS-3321 devices were used. Natural ventilation was controlled via windows and/or doors, and the influence of air conditioning was studied in one of these rooms, in which medium- to high-intensity activities were conducted. All experiments revealed a decrease in temperature associated with an increase in the relative humidity when CO2 decreased. As a consequence, drastic decreases occurred a few minutes after windows and doors were opened. In no-ventilation intervals, the observed linear increase changed into an asymptotic trend below the 1000 ppm limit recommended by Sinphonie guidelines. Additionally, the opposite behavior was observed between particles above and below a certain size. This experiment is of interest to further investigate critical ventilation rate versus volume of air per individual.

A review of the indoor air quality in residential Passive House dwellings

The Passive House (PH) Standard is a voluntary building energy performance standard focused upon reducing space heating demand to a very low level and therefore considered a viable climate change mitigation technology. Besides comfort and energy requirements, the PH standard also defines criteria with respect to ventilation. However, the question remains, how well do PH dwellings perform when they are occupied? Does the PH approach provide good indoor air quality (IAQ) for its occupants and how does IAQ compare to non-PH homes, in particular, naturally ventilated homes? Additionally, can PH certification improve the quality of installed ventilation systems? This paper summarizes indoor air quality relevant aspects of the PH standard and presents results from measurements examining in-use IAQ in more than 600 PH or PH-like, newly built or retrofitted dwellings. The results reveal that pollutant and carbon dioxide concentration are generally lower compared to naturally ventilated homes, presumably due to the requirement to install a balanced Mechanical Ventilation with Heat Recovery (MVHR) system. Results also suggest that the quality assurance measures of PH certification are capable of improving ventilation and IAQ performance. However, the lack of cooking fume capture requirements in the PH standard, in combination with efforts to avoid energy losses associated with a possible extraction kitchen hood, may lead to elevated particulate matter concentration in PHs. Future research on cooking induced IAQ impairment is encouraged to assess the effectiveness of recently published PH-specific recommendations. Future efforts in empirical IAQ research should also address the lack of high quality IAQ measurement data and the standardisation of IAQ assessment methods and protocols.

Association Between Air Microbiological Exposure With Sick Building Syndrome (SBS) among College Dormitory Students in Public University

Introduction: Microbiological pollutants in indoor air can lead to sick building syndrome (SBS). A conducive academic environment in university dormitories requires healthy indoor air quality to enhance student performance. This study aimed to determine the association between indoor air microbiological exposure and SBS among college dormitory students at a public university. Methods: A cross-sectional study was conducted among 112 male and female college dormitory students who stayed in the public university dormitory for more than three months. Respondents were given a self-administered questionnaire-based NIOSH Indoor Environmental Quality Survey. 14 houses were selected for the measurement of indoor air quality which included PM2.5, PM10, relative humidity (%), temperature (°C), air velocity (m/s), indoor bacterial concentration (cfu/m3), and indoor mould concentration (cfu/m3). Results: Higher percentages of SBS symptoms were reported among female (94.6%) college dormitory students compared to male (82.1%). A significant difference in itching symptom on the arms and forearms was found among individuals of different genders (p<0.05). Indoor air parameters such as temperature (OR = 2.56, 95% CI = 2.66-9.87), relative humidity (OR = 1.77, 95% CI = 1.54 – 5.79), indoor bacteria concentration (OR=2.28, 95% CI = 2.48 – 10.93), and indoor mould concentration (OR=2.59, 95% CI = 1.75 – 8.98) were significantly associated with the recent SBS symptoms. Multiple logistic regression showed that the most significant predictor of SBS was indoor mould concentration. Conclusion: Exposure to high concentrations of indoor bacteria and mould, high temperatures, and high relative humidity influenced the prevalence of SBS among college dormitory students. Further assessment and preventive action need to be taken to reduce the exposure of indoor air microbiological to the students.

Impact of industrial pollution on children's lungs: A comparative analysis of pulmonary function in critically polluted and non-polluted areas in western India

BackgroundAir pollution is a pressing global health concern, particularly in low- and middle-income countries like India. Children living near industrialized and critically polluted areas (CPAs) face heightened health risks due to their developing respiratory systems. This study aimed to assess the impact of industrial pollution on children's lung function in a CPA in western India. MethodologyThe study evaluated 362 children studying in 5th to 7th standard from both a CPA and a relatively non-polluted area (NPA) for comparison. Ambient and indoor air quality measurements were taken, and pulmonary function tests were conducted to assess lung health. Group difference and regression analysis were performed with SPSS 26.0. ResultsThe CPA group showed significantly higher air pollution levels and a higher prevalence of obstructive and restrictive patterns in pulmonary function compared to the NPA group. The findings also revealed that children residing in CPA exhibited a significant decline of 530 ml forced expiratory flow rate (FEF 25–75%), and a reduction of 3.9% FEV1/FVC ratio when compared to children residing in relatively NPA. ConclusionWhile this study's cross-sectional design has limitations, it provides valuable evidence of the impact of air pollution on children's lungs in a semi-urban industrialized area. To mitigate these health risks, integrating respiratory health check-ups, including pulmonary function tests, in existing health programs, like Rastriya Bal Swasthya Karyakram (RBSK), is recommended for early detection and intervention. Implementing initiatives such as enhancing green belts around schools and continuous air quality monitoring will be crucial.

Systematically omitting indoor air quality: sub-standard guidance for shelters, group homes and long-term care in Ontario during the COVID-19 pandemic

ABSTRACT Public Health Ontario (PHO) is mandated by legislation to share scientific advice during infectious disease outbreaks and help reduce health inequities in Ontario, Canada. PHO was founded in part to address the failures of Ontario’s public health system during the 2003 outbreak of SARS-CoV-1, which included the failure to address airborne transmission. By January 2021, public health authorities had access to a body of literature suggesting SARS-CoV-2 was airborne, and had received urgent warnings from scientists. We set out to document how PHO responded to the likelihood – and, eventually, the certainty – of airborne transmission in the context of its guidance for congregate settings such as long-term care and shelters. In October 2021, we reviewed PHO’s public, written COVID-19 guidance for these settings, with a focus on indoor air quality (IAQ) measures that mitigate airborne transmission, such as ventilation. We identified 11 PHO documents for congregate settings. They contained no references to IAQ measures. We did, however, find references to IAQ measures in parallel documents for schools, summer camps, and clinical offices. Our findings demonstrate PHO omitted key infection prevention measures from its COVID-19 guidance for congregate settings, putting workers and residents at greater risk of exposure, illness and death, and exacerbating health inequities.

A novel low sampling rate and cost-efficient active sampler for medium/long-term monitoring of gaseous pollutants

Active sampling is a dependable approach for gaseous pollutants monitoring, offering high accuracy and precision that is unaffected by environmental factors such as wind and temperature in comparison to passive sampling. To measure long-term average concentrations while minimizing the use of materials, a reduced sampling rate is necessary. Thus, this study aims to develop a novel low sampling rate (down to 1 mL/min) and cost-efficient active sampler (LASP) for medium/long-term monitoring of gaseous pollutants. The LASP mainly consisted of a syringe pump, a Y-shaped fitting with two one-way valves, and a control unit for intermittent operation. Results showed that LASP can obtain a sampling rate of less than 1 mL/min and sampling rate exhibited a high level of stability. Daily average concentrations measurements for nitrogen dioxide and formaldehyde by LASP had normalized mean biases of 2.8% and 5.2%, respectively. These numbers were − 5.8% and 6.1% for weekly-average samplings. This study demonstrated applications of LASP in real outdoor (daily-average) and indoor (weekly-average) air quality measurements. It worked well with low noise levels, and without interfering with occupants' daily activities. LASP can assist in improving our ability to monitor air quality and pollutants emissions, thereby supporting health research and policy development. Environmental implicationGaseous air pollution is an important hazardous factor threatening human health. Medium/long-term air quality monitoring is essential for outdoor and indoor air quality assessment and control. However, air sampler for medium/long-term sampling is lacking. This study developed a novel low sampling rate and cost-efficient active sampler and applied it to medium/long-term air sampling. The sampler can work at a sampling rate of less than 1 mL/min. This technology provides a feasible strategy for medium/long-term monitoring of gaseous air pollutants in both environments and emission hotspots.

Internet of Things (IoT) in Buildings: A Learning Factory

Advances towards smart ecosystems showcase Internet of Things (IoT) as a transversal strategy to improve energy efficiency in buildings, enhance their comfort and environmental conditions, and increase knowledge about building behavior, its relationships with users and the interconnections among themselves and the environmental and ecological context. EU estimates that 75% of the building stock is inefficient and more than 40 years old. Although many buildings have some type of system for regulating the indoor temperature, only a small subset provides integrated heating, ventilation, and air conditioning (HVAC) systems. Within that subset, only a small percentage includes smart sensors, and only a slight portion of that percentage integrates those sensors into IoT ecosystems. This work pursues two objectives. The first is to understand the built environment as a set of interconnected systems constituting a complex framework in which IoT ecosystems are key enabling technologies for improving energy efficiency and indoor air quality (IAQ) by filling the gap between theoretical simulations and real measurements. The second is to understand IoT ecosystems as cost-effective solutions for acquiring data through connected sensors, analyzing information in real time, and building knowledge to make data-driven decisions. The dataset is publicly available for third-party use to assist the scientific community in its research studies. This paper details the functional scheme of the IoT ecosystem following a three-level methodology for (1) identifying buildings (with regard to their use patterns, thermal variation, geographical orientation, etc.) to analyze their performance; (2) selecting representative spaces (according to their location, orientation, use, size, occupancy, etc.) to monitor their behavior; and (3) deploying and configuring an infrastructure with +200 geolocated wireless sensors in +100 representative spaces, collecting a dataset of +10,000 measurements every hour. The results obtained through real installations with IoT as a learning factory include several learned lessons about building complexity, energy consumption, costs, savings, IAQ and health improvement. A proof of concept of building performance prediction based on neural networks (applied to CO2 and temperature) is proposed. This first learning shows that IAQ measurements meet recommended levels around 90% of the time and that an IoT-managed HVAC system can achieve energy-consumption savings of between 10 and 15%. In summary, in a real context involving economic restrictions, complexity, high energy costs, social vulnerability, and climate change, IoT-based strategies, as proposed in this work, offer a modular and interoperable approach, moving towards smart communities (buildings, cities, regions, etc.) by improving energy efficiency and environmental quality (indoor and outdoor) at low cost, with quick implementation, and low impact on users. Great challenges remain for growth and interconnection in IoT use, especially challenges posed by climate change and sustainability.

Suitability of Low-Cost Sensors for Submicron Aerosol Particle Measurement

The measurement and assessment of indoor air quality in terms of respirable particulate constituents is relevant, especially in light of the COVID-19 pandemic and associated infection events. To analyze indoor infectious potential and to develop customized hygiene concepts, the measurement monitoring of the anthropogenic aerosol spreading is necessary. For indoor aerosol measurements usually standard lab equipment is used. However, these devices are time-consuming, expensive and unwieldy. The idea is to replace this standard laboratory equipment with low-cost sensors widely used for monitoring fine dust (particulate matter—PM). Due to the low acquisition costs, many sensors can be used to determine the aerosol load, even in large rooms. Thus, the aim of this work is to verify the measurement capability of low-cost sensors. For this purpose, two different models of low-cost sensors are compared with established laboratory measuring instruments. The study was performed with artificially prepared NaCl aerosols with a well-defined size and morphology. In addition, the influence of the relative humidity, which can vary significantly indoors, on the measurement capability of the low-cost sensors is investigated. For this purpose, a heating stage was developed and tested. The results show a discrepancy in measurement capability between low-cost sensors and laboratory measuring instruments. This difference can be attributed to the partially different measuring method, as well as the different measuring particle size ranges. The determined measurement accuracy is nevertheless good, considering the compactness and the acquisition price of the low-cost sensors.

Highly sensitive portable laser absorption spectroscopy formaldehyde sensor using compact spherical mirror multi-pass cell

A portable sensor with an optical case dimension of 46 × 28 × 16 cm3 based on laser absorption spectroscopy for highly sensitive measurement of formaldehyde was reported. A compact improved spherical mirror multi-pass cell consisting of two 5-cm diameter spherical mirrors separated by 17.7 cm was developed. The cell offered a sample volume of 350 mL and an optical absorption path length of 50.6 m, giving a high path length-to-volume ratio of 14.6 cm−2. The sampling response time was less than 1 s, allowing the application of rapid spectral background subtraction technique to effectively suppress optical fringes. The achieved detection limit was 650 pptv (1σ, 1 s), corresponding to a minimum detection absorption coefficient of 2.3 × 10−9 cm−1. The capability of the HCHO sensor was demonstrated by two days of continuous indoor air monitoring. The developed portable sensor is suitable for mobile and fast indoor air quality measurements.

Assessment of indoor air quality of porous media combustion-based cookstoves.

The present study analyzes the emission mitigation ability of a porous media combustion (PMC) technology-based cookstove compared to a free flame combustion (FFC) technology-based cookstove. Emission of pollutants, i.e., PM2.5, PM10, and CO, caused due to burning of fuels, namely, methanol, ethanol, kerosene, and LPG in the kitchen environment are measured. The study incorporated exhaustive real-time indoor air quality (IAQ) measurements and presented the temporal variation of measured pollutant concentrations for 2 h (morning meal duration). In addition, 24 h average concentration of the measured pollutants is also compared with the limits prescribed in WHO guidelines for domestic settings. The results emphasized that the utilization of cookstove based on PMC would help in improving the IAQ of the kitchen area by decreasing the concentrations of PM2.5, PM10, and CO. For 2 h duration measurements, the methanol cookstove based on PMC reduced the concentrations of PM2.5, PM10, and CO by 7.7%, 8.1%, and 17.2%, respectively, compared to FFC cookstove. Similarly, in the case of PMC-based LPG cookstove and kerosene cookstove, the respective values were 11.7%, 20.4%, and 41.6% and 55.3%, 62.6%, and 66.6%. Among all the tested cookstoves, PMC-based LPG cookstove achieved the lowest emission values (PM2.5: 20.6 μg/m3, PM10: 31.3 μg/m3, and CO: 1 ppm) which are lower than the prescribed WHO values (PM2.5: 25 μg/m3, PM10: 50 μg/m3, and CO: 6 ppm).

User Recognition Factors for Preference Evaluation of Fire Extinguishers in Residential Spaces

Fire extinguishers are considered essential safety items to be installed in residential spaces to improve the fire safety in buildings. However, they are usually placed in inconspicuous locations owing to design and practical constraints, making their immediate use difficult in a fire scenario. This study identifies problems regarding the application of existing fire extinguishers in residential spaces, and investigates factors influencing user preferences in recognizing fire extinguishers. A draft fire extinguisher design that aims to address the problems associated with existing fire extinguishers in terms of design and practicality was derived. Using this draft, a survey was conducted to analyze the factors influencing user preference while considering the improvement of practical problems with existing fire extinguishers. A life-friendly product design is proposed to ensure its use at all times in daily life; an indoor air quality measurement sensor and fire detection/alarm system are installed. Results of the survey confirmed that aesthetic factors and novelty had the most influence on overall likeability towards preferring a fire extinguisher. This study is expected to contribute to the future development of fire extinguishers by verifying the preference factors for users to be willing to keep fire extinguishers indoors.

A scoping review of indoor air quality assessment in refurbished buildings

PurposeExposure to poor indoor air in refurbished buildings is a matter of health concern due to the growing concentrations of various contaminants as a result of building airtightness without amendment of ventilation, or the use of building materials such as glue, paint, thinner and varnishes. Recent studies have been conducted to measure indoor air pollutants and assess the health risks affecting the quality of life, productivity and well-being of human beings. However, limited review studies have been recently conducted to provide an overview of the state of knowledge. This study aims to conduct a scoping review of indoor air quality (IAQ) in the context of refurbished or energy-retrofitted buildings.Design/methodology/approachA systematic screening process based on the PRISMA protocol was followed to extract relevant articles. Web of Science, Scopus, Google Scholar and PubMed were searched using customised search formulas. Among 276 potentially relevant records, 38 studies were included in the final review covering a period from 2015 to 2022.FindingsResearchers mapped out the measured compounds in the selected studies and found that carbon dioxide (CO2) (11%) and total volatile organic compounds (11%) were among the most commonly measured contaminants. Two trends of research were found including (1) the impact of ventilative properties on IAQ and (2) the impact of introducing building materials on IAQ.Originality/valueThe contribution of this study lies in summarising evidence on IAQ measurements in refurbished buildings, discussing recent advancements, revealing significant gaps and limitations, identifying the trends of research and drawing conclusions regarding future research directions on the topic.

The first test of indoor air quality in kindergartens of the Republic of Srpska

The first experimental results of the indoor air quality in two kindergartens located in the Republic of Srpska are presented in this paper. Kindergarten representatives for the year of construction (old and new), building materials, and energy efficiency have been chosen. Indoor air quality measurements (air temperature, relative humidity, ventilation rate, CO2, and radon concentration) were performed during the winter of 2015/2016. Measured indoor air quality parameters are discussed and compared to the international standards BAS EN 16798-1, ASHRAE 62.1, and ISO 7730. The average measured radon concentrations for both buildings have not exceeded the level of 200 Bqm-3, but for reliable results, long-term measurement needs to be performed. The CO2 concentration in the old kindergarten fulfills the BAS EN 16798-1 requirement for category I during 62.43% of total occupancy time, while for the new kindergarten, it is only 5.79% of full occupancy time. Results of CO2 concentration confirm that good sealing of the envelope of new buildings and user behavior (number of users and natural ventilation) does affect air quality. Furthermore, a high correlation between CO2 concentration and relative humidity in both buildings and a more considerable correlation for the new building have been observed.

Utilizing Unobtrusive Portable Electronic Devices for Real-Time Assessment of Indoor PM2.5 and tVOC Exposure and Its Correlation with Heart Rate Variability

Real-time monitoring of Heart Rate Variability (HRV) and Indoor Air Quality (IAQ) can help individuals and organizations identify potential causes of poor indoor air quality and implement corrective measures to improve the indoor environment as well as evaluating the effectiveness of interventions and measuring their impact on both HRV and overall health and well-being. Simultaneously measuring HRV and IAQ allows for the real-time observation of the correlation between the two. The proposed solution uses a non-intrusive system utilizing the wrist wearable MAXREFDES103# Health Sensor Band by Maxim Integrated® and the portable Atmotube PRO by ATMOTECH INC® for real-time monitoring of HRV and IAQ, respectively. The results of the deployment provide evidence that exposure to Particulate Matter (PM) and total Volatile Organic Compounds (tVOC), has a negative impact on HRV. The data indicates that for every increase of 10.37 μg/m3 in PM2.5 and 57.4ppb in tVOC, there was an average decrease of 5.3% in SDNN and 7.08% in RMSSD of HRV. The findings of this study have important implications for public health, as HRV is a useful indicator of cardiovascular health.

The HOME-Health (HOusing, environMEnt, and Health) Study; Description of a Danish natural experiment, designed as a longitudinal study with repeated measurements, providing internal- and external validity of the study.

The ambient and indoor environment are pivotal to our health. We spend most of our time indoors within our home, why our home is where we are most exposed to indoor pollutants and indoor air quality (IAQ). Populations within social housing areas are more vulnerable due to advanced age, co-morbidity and social economic status. Commonly, studies within social housing are cross-sectional, few Nordic longitudinal studies exist, and fewer studies combine quantitative and qualitative measurements in a mixed method approach. This research proposal provides an extensive detailed description of the design and methodology of the HOME-Health study. The study is a longitudinal study and is a natural experiment employing structured surveys, objective measurements of indoor air parameters, lung function test and qualitative semi-structured interviews. Data collection are conducted seasonally (winter and summer), before and after building energy renovation (BER). The study population before BER (n = 432) was explored and found similar to the Danish social housing population in terms of age, gender, persons per apartment and migration status. Future analyses should be stratified by multi-family apartments and terraced houses. The aim of the HOME-Health study is to provide knowledge about residents' seasonal state of health, perception of indoor enviromental quality (IEQ), IEQ-related behaviours and practices, and objective measurements of IAQ before and after BER. By applying a design with repeated measurement before and after BER, and combining both objective and subjective quantitative as well as qualitative data the study is expected to create in-depth knowledge. Future results will provide evidence of both energy-savings and non-energy savings from different BER projects. Knowledge which are expected to benefit future renovation projects within social housing areas.

Measurement and rapid assessment of indoor air quality at mass gathering events to assess ventilation performance and reduce aerosol transmission of SARS-CoV-2.

To assess risk factors for COVID-19 transmission and address the closure of mass gathering events since March 2020, the UK Government ran the Events Research Programme (ERP), following which it reopened live events in sports, music, and culture in July 2021. We report the rapid post-occupancy evaluation of Indoor Air Quality (IAQ) and associated long-range airborne transmission risk conducted in the Environmental Study of the ERP. Ten large venues around the UK were monitored with CO2 sensors at a high spatial and temporal resolution during 90 events. An IAQ Index based on CO2 concentration was developed, and all monitored spaces were classified in bands from A to G based on their average and maximum CO2 concentrations from all events. High resolution monitoring and the IAQ Index depicted the overall state of ventilation at live events, and allowed identification of issues with ventilation effectiveness and distribution, and of spaces with poor ventilation and the settings in which long-range airborne transmission risk may be increased. In numerous settings, CO2 concentrations were found to follow patterns relating to event management and specific occupancy of spaces around the venues. Good ventilation was observed in 90% of spaces monitored for given occupancies. Practical applications: High-resolution monitoring of indoor CO2 concentrations is necessary to detect the spatial variation of indoor air quality (IAQ) in large mass gathering event venues. The paper summarises COVID-19 ventilation guidance for buildings and defines a methodology for measurement and rapid assessment of IAQ during occupancy at live events that can be implemented by venue managers. Comparisons of the CO2 concentrations measured during the events identified the spaces at high risk of long-range transmission of airborne pathogens. Building operators should be mindful of the ventilation strategies used relative to the total occupancy in different spaces and the occupant's activities.

Proxy methods for detection of inhalation exposure in simulated office environments

BackgroundModern health concerns related to air pollutant exposure in buildings have been exacerbated owing to several factors. Methods for assessing inhalation exposures indoors have been restricted to stationary air pollution measurements, typically assuming steady-state conditions.ObjectiveWe aimed to examine the feasibility of several proxy methods for estimating inhalation exposure to CO2, PM2.5, and PM10 in simulated office environments.MethodsIn a controlled climate chamber mimicking four different office setups, human participants performed a set of scripted sitting and standing office activities. Three proxy sensing techniques were examined: stationary indoor air quality (IAQ) monitoring, individual monitoring of physiological status by wearable wristband, human presence detection by Passive Infrared (PIR) sensors. A ground-truth of occupancy was obtained from video recordings of network cameras. The results were compared with the concurrent IAQ measurements in the breathing zone of a reference participant by means of multiple linear regression (MLR) analysis with a combination of different input parameters.ResultsSegregating data onto sitting and standing activities could lead to improved accuracy of exposure estimation model for CO2 and PM by 9–60% during sitting activities, relative to combined activities. Stationary PM2.5 and PM10 monitors positioned at the ceiling-mounted ventilation exhaust in vicinity of the seated reference participant accurately estimated inhalation exposure (adjusted R² = 0.91 and R² = 0.87). Measurement at the front edge of the desk near abdomen showed a moderate accuracy (adjusted R² = 0.58) in estimating exposure to CO2. Combining different sensing techniques improved the CO2 exposure detection by twofold, whereas the improvement for PM exposure detection was small (~10%).SignificanceThis study contributes to broadening the knowledge of proxy methods for personal exposure estimation under dynamic occupancy profiles. The study recommendations on optimal monitor combination and placement could help stakeholders better understand spatial air pollutant gradients indoors which can ultimately improve control of IAQ.

Ventilation strategies and indoor air quality in Swedish primary school classrooms

The present study aimed at investigating the effects of ventilation strategies on indoor air quality (IAQ) in schools. Measurements of thermal environment and IAQ were performed over 5 school days in 45 primary school classrooms in Gothenburg, Sweden, grouped into three categories according to their ventilation system: category A) natural or exhaust ventilation, or automated window opening; category B) balanced mechanical ventilation systems with constant air volume (CAV) and category C) balanced mechanical ventilation systems with variable air volume (VAV). The classrooms performed equally well with respect to temperature and relative humidity regardless of the ventilation system. The concentrations of the air pollutants in all classrooms were generally below the respective guideline values. The concentrations of CO2, formaldehyde, PM10, and PM2.5 were lower in the B and C category classrooms with higher ventilation rates than in the A category classrooms. Indoor Air Pollution Index integrating concentrations of multiple pollutants was significantly higher the A category classrooms, reflecting poorer IAQ. Majority of the classrooms had lower ventilation rates than the Swedish ventilation requirements. The periodically reduced ventilation rates in the classrooms with VAV systems did not lead to substantial increase in the measured indoor pollutant concentrations.

A field intervention study of the effects of window and door opening on bedroom IAQ, sleep quality, and next-day cognitive performance

Indoor Air Quality (IAQ) and sleep quality measurements over a period of two weeks were performed all night in 40 bedrooms in Denmark during the heating season. In the first week, the bedroom conditions were typical of what participants would normally experience during sleep. In the second week, the participants were asked to open the doors or windows if they had been closed or the opposite. A change in the 95th percentile of the measured CO2 concentration by more than 200 ppm in the expected direction on the same weekdays of the two-week measurement period was taken to indicate that an effective intervention had taken place. The measurements in the 29 bedrooms that met this criterion were grouped depending on how the windows or doors had been manipulated. Objectively measured and subjectively rated bedroom IAQ improved when the windows were open except that the NO2 concentration was slightly higher. Sleep was longer under this condition and sleep quality was subjectively assessed to be better. Similar effects were not observed when the doors were open although the 95th percentile of CO2 concentration decreased by as much as when the windows were open. No effects were seen in the 11 bedrooms in which the change to the bedroom conditions made by the participants did not change the CO2 concentration by at least 200 ppm, as would be expected. The present study provides evidence that sufficient dilution and/or removal of pollutants is necessary to ensure good bedroom IAQ and good sleep quality.