Indoor Air Quality Studies Research Articles

An Experimental Study of Thermal Comfort and Indoor Air Quality—A Case Study of a Hotel Building

Ensuring the comfort and health of occupants is the main objective of properly functioning building systems. Regardless of the season and building types, it is the priority of the designers and building managers. The indoor air parameters affect both the well-being and health of users. Furthermore, it could impact the effectiveness of their work and concentration abilities. In hotel facilities, the guests’ comfort is related directly to positive opinions or customer complaints, which is related to financial benefits or losses. The main goal of this study is the analysis of the indoor environmental quality in guests’ rooms, based on the example of a hotel in Poland. The article assesses the variability of air parameters, including temperature, humidity, and carbon dioxide concentrations, and the acceptability of indoor conditions. The research was carried out in November 2020. Based on the collected data, the dynamics of changes of selected air parameters were analyzed. The article analyzes the comfort indicators inside guest rooms, including the Predicted Mean Vote (PMV) and Predicted Percentage of the Dissatisfied (PPD) index. The obtained results were compared with the optimal conditions of use to ensure the guests’ comfort. As the analysis showed, the temperature and humidity conditions are maintained at a satisfactory level for most of the time. It was noticed that the CO2 concentrations temporarily exceeded the value of 2000 ppm in two of the analyzed guests’ rooms, which could cause discomfort to hotel guests. In these rooms, the increase in the volume of ventilation airflow should be considered. The measured parameters dynamically varied over time, and there was no repeatability or clear patterns of variation. This is due to the individual preferences and behavior of users. A detailed analysis is extremely difficult due to the possibility of opening windows by users, the irregular presence of hotel guests in the rooms, and the inability to verify the exact number of users in the room during the measurements.

Design and Implementation of a Strategy for the Study of Indoor Air Quality (Iaq) Including Respiratory Viruses in Educational Centers

Design and Implementation of a Strategy for the Study of Indoor Air Quality (Iaq) Including Respiratory Viruses in Educational Centers

Indoor Air Quality Campaign in an Occupied Low-Energy House with a High Level of Spatial and Temporal Discretization

Background and gaps. The topic of indoor air quality (IAQ) in low-energy buildings has received increasing interest over the past few years. Often based on two measurement points and on passive measurements over one week, IAQ studies are struggling to allow the calculation of pollutants exposure. Objectives. We would like to improve the evaluation of the health impacts, through measurements able to estimate the exposure of the occupants. Methodology. This article presents detailed IAQ measurements taken in an energy-efficient occupied house in France. Two campaigns were conducted in winter and spring. Total volatile organic compounds (TVOC), formaldehyde, the particle numbers and PM2.5, carbon dioxide (CO2), relative humidity (RH), temperature (T), ventilation airflows, and weather conditions were dynamically measured in several points. Laboratory and low-cost devices were used, and an inter-comparison was carried out for them. A survey was conducted to record all the daily activities of the inhabitants. IAQ performance indicators based on the different pollutants were calculated. Results. PM2.5 cumulative exposure did not exceed the threshold available in the literature. Formaldehyde concentrations were high, in the kitchen, where the average concentrations exceeded the threshold. However, the formaldehyde cumulative exposure of the occupants did not exceed the threshold. TVOC concentrations were found to reach the threshold. With these measurements performed with high spatial and temporal discretization, we showed that such detailed data allow for a better-quality health impacts assessment and for a better understanding of the transport of pollutants between rooms.

On the Water-Soluble Organic Matter in Inhalable Air Particles: Why Should Outdoor Experience Motivate Indoor Studies?

The current understanding of water-soluble organic aerosol (OA) composition, sources, transformations, and effects is still limited to outdoor scenarios. However, the OA is also an important component of particulate matter indoors, whose complexity impairs a full structural and molecular identification. The current limited knowledge on indoor OA, and particularly on its water-soluble organic matter (WSOM) fraction is the basis of this feature paper. Inspired by studies on outdoor OA, this paper discusses and prioritizes issues related to indoor water-soluble OA and their effects on human health, providing a basis for future research in the field. The following three main topics are addressed: (1) what is known about the origin, mass contribution, and health effects of WSOM in outdoor air particles; (2) the current state-of-the-art on the WSOM in indoor air particles, the main challenges and opportunities for its chemical characterization and cytotoxicity evaluation; and (3) why the aerosol WSOM should be considered in future indoor air quality studies. While challenging, studies on the WSOM fraction in air particles are highly necessary to fully understand its origin, fate, toxicity, and long-term risks indoors.

Experimental Study of Indoor Air Quality for Cooling Condition Using ARDUINO System and PMV Index Testing the Effect of Heat Sources

The human thermal comfort and the indoor healthy air quality in the houses and the offices have become a vital necessity, especially in the state of the development of the contagious virus as the COVID-19. In this study, the evaluation of the air distribution was investigated using a DHTT sensor connected to an ARDUINO card to benefit their simple use and their reasonable price comparing to other tools such as the infrared camera. The measurement of the temperature is made in 14 points divided on two directions: one near the sitting manikin and another in front with the cooling system. The impact of the heat sources was tested. In these conditions, the indoor temperature was examined for an empty room, a room occupied by one person and one computer, a room occupied by two persons and two computers and a lighted room. The experimental results prove that the indoor temperature increases with the multiplication of the heat sources. From a temperature equal to [Formula: see text]C, the PMV curves move away from the comfort zone and the indoor climate becomes hot.

Mixing state of printer generated ultrafine particles: Implications for the complexity of indoor aerosols

The operation of laser printers can lead to the emission of high numbers of ultrafine particles. Evidence on the toxicology and adverse health effects of these particles has been mounting, however few studies have investigated the complexity of these particles in terms of their volatility, hygroscopicity and mixing state. This study utilized a Volatility Hygroscopic Tandem Differential Mobility Analyzer (VH-TDMA) to explore the internal and external mixing states of printer-generated particles. Up to 6.0 × 105 particles. cm−3 were observed during the operation of the laser printer, and these ultrafine particles could be classified into three groups, each with its own particular volatility (i.e., gradually shrinkable, suddenly shrinkable and expandable), owing to the different internal mixing states. In particular, we propose shell-core structures to explain the special volatility of these particles. In addition, whilst the majority of the generated particles were initially hydrophobic at 90% relative humidity (RH), it was observed that there were a very small number of volatilized particles (less than 5%) that shrank (i.e., decreased in size) after humidification. This study can be used as a model for investigating the complex particle formation processes in relation to secondary organic aerosols from other sources. Furthermore, our results shed light on the complexity of indoor aerosols, which should be investigated further in future indoor air quality studies.

Passive cooling and natural ventilation by the windcatcher (Badgir): An experimental and simulation study of indoor air quality, thermal comfort and passive cooling power

The upper wing wall can be integrated into the windcatcher to prevent direct solar and rain penetration. The impact of this combination was not considered in previous studies. Moreover, analyzing adaptive thermal comfort is another gap that was not addressed by preceding windcatcher studies, particularly for the tropical climate. Therefore, the current research aims to evaluate a two-sided windcatcher incorporated with the upper wing wall from two views: indoor air quality (IAQ) and adaptive thermal comfort. A small-scale model was tested in the wind tunnel. Next, CFD models were validated against experimental data with a good agreement between the two methods. Windcatchers with different upper wing wall lengths ranging between 10 cm and 50 cm were assessed. The results showed that the length increase led to a slight increase in the ventilation rate, and the best performance was seen in the 50 cm configuration. Subsequently, IAQ and adaptive thermal comfort were evaluated at different wind speeds of this climate. The results demonstrated that even in wind speeds below the annual average (2.5 m/s), the windcatcher performance can still satisfy IAQ parameters such as airflow rate and air change rate, recommend by CIBSE Guide A. In addition, based on the simulated conditions the results showed that wind speed from 2.5 m/s to 4 m/s could provide thermal comfort within 50%–80% of the ventilated space. Finally, the estimation of passive cooling power showed that windcatcher could provide a maximum (9.6 kW) cooling power if the wind speed is at 4 m/s and outdoor temperature at 23 °C.

Indoor Air Quality in Buildings: A Comprehensive Review on the Factors Influencing Air Pollution in Residential and Commercial Structure.

Worldwide people tend to spend approximately 90% of their time in different indoor environments. Along with the penetration of outside air pollutants, contaminants are produced in indoor environments due to different activities such as heating, cooling, cooking, and emissions from building products and the materials used. As people spend most of their lives in indoor environments, this has a significant influence on human health and productivity. Despite the two decades of indoor air quality (IAQ) research from different perspectives, there is still a lack of comprehensive evaluation of peer-reviewed IAQ studies that specifically covers the relationship between the internal characteristics of different types of building environments with IAQ to help understand the progress and limitations of IAQ research worldwide. Therefore, this review of scientific studies presents a broad spectrum of pollutants identified in both residential and commercial indoor environments, highlighting the trends and gaps in IAQ research. Moreover, analysis of literature data enabled us to assess the different IAQs in buildings located in different countries/regions, thus reflecting the current global scientific understanding of IAQ. This review has the potential to benefit building professionals by establishing indoor air regulations that account for all indoor contaminant sources to create healthy and sustainable building environments.

Monitoring of paraben compounds in indoor and outdoor air of a populated city

Detection of paraben compounds in numerous human biological samples and their association with many health disorders imply that the humans can be exposed to parabens in many ways. Although many researchers have studied dermal and oral exposures to parabens, a few of them have considered indoor and outdoor air as a source for human exposure to these compounds. Therefore, this study was conducted to monitor the indoor and outdoor air concentrations of parabens in different places and age groups in Isfahan, Iran. For this purpose, ten sites were selected to determine four parabens in indoor and outdoor air simultaneously. Sampling was carried out using a polyurethane foam (PUF) tube connected to a SKC pump operating at a flow rate of 10 L/min. Parabens desorption from PUF, their extraction from solvents and their analysis were performed using methanol/water solvents, ultrasonic-assisted dispersive liquid-liquid and micro-extraction (DLLME) and gas chromatography-mass spectrometer (GC-MS), respectively. Results showed a significant difference among MePB (p = 0.002), EtPB (p = 0.001), PrPB (p = 0.001) and BuPB (p = 0.013) concentrations in indoor and outdoor air. Moreover, the lowest and the highest concentrations of MePB (0.36 and 0.63 ng/m3), EtPB (0.31 and 0.65, ng/m3), PrPB (0.64 and 1.07 ng/m3) and BuPB (0.0 and 0.21 ng/m3) were detected in green spaces and barbershops. The infants and children (6–8 years) were found to be exposed to the highest risk of indoor air. The obtained results can provide a basis for future indoor and outdoor air quality studies.

Why cleaning the invisible in restaurants is important during COVID-19: A case study of indoor air quality of an open-kitchen restaurant.

During the COVID-19 pandemic, restaurant sanitation and disinfection have become more important than ever although customers can hardly check visually. The most recent research argues that one invisible element leaving people vulnerable to the health effects of COVID-19 is particulate matter (PM), micron-sized particles known to cause acute or chronic respiratory illnesses, including lung cancer. While research shows PM is emitted from cooking, this study examines indoor PM pollution of an open-kitchen full-service chain restaurant, where commercial cooking occurs in the dining room, as a case study. The results of a week-long field test showed offensively harmful levels of PM10 and PM2.5, far beyond US EPA and WHO standards, while ambient outdoor PM associated with the sample restaurant was safe. The study reveals that working or frequently dining in an open-kitchen restaurant where grilling or frying takes place is likely to cause respiratory health problems and elevate susceptibility to COVID-19 unless surveillance and preventative measures are taken. Based on our findings, implications and recommendations for the industry are provided.

Reporting Results of a Community-Based In-Home Exposure Monitoring Study: Developing Methods and Materials.

Reporting exposure results to study participants provides information that can ideally be used to decrease harmful exposures, improve health, and prevent disease. In reality, we often do not fully understand how an environmental exposure contributes to disease. This is the case when reporting back indoor air exposures in the absence of regulations. We reported nitrogen dioxide (NO2) and fine particulate matter (PM2.5) results back to individual participants of an in-home study in Chelsea, Massachusetts. We aimed to provide participants with information on the pollutant concentrations in their homes and in their community and to suggest strategies for decreasing in-home exposures. Our goals were to improve environmental health literacy and empower residents to take action on air quality issues in their community. The main objective of this paper is to describe how we developed our report back process and materials. Our team of academic and community partners developed a two-part report back process. The first part included a mailing tailored to every home containing daily indoor and outdoor NO2 and PM2.5 concentrations, community averages, outdoor standards and guidelines, and results from other indoor air quality studies for comparison. The second part included a community meeting for participants. Our report back process and materials benefitted from the contributions of multiple diverse stakeholders. We recommend at least a two-part strategy for facilitating communication within the community and between community and academic researchers. The materials and methods can be easily adapted by other researchers to report back exposure results in other community-specific contexts.

Work Exposure to VOC in Storage Areas of Retail Stores.

Poor indoor air quality (IAQ) has been linked to airway disease and early deaths. The ESQUISSE study of IAQ conducted by the French Research and Safety Institute (INRS), characterized the concentrations of various volatile organic compounds (VOCs) in 10 retail stores and storage areas. The IAQ was generally better in sales areas than storage areas, which are more often unventilated and overloaded with new products. For example, in clothing stores, formaldehyde concentrations between 29.0 and 45.0 µg m-3 were measured in non-ventilated storage areas located in the basement; in sales areas, concentrations did not exceed 10.2 µg m-3. Similarly, total VOC (TVOC) concentrations in the two main storage areas were 1153 and 1223 µg m-3 toluene equivalent, whereas they were less than 77.0 µg m-3 toluene equivalent in all sales areas. Many employees work in these high-exposure areas either temporarily or for the entire day, unpacking boxes, placing products on shelves, or collecting products. Reporting primarily on formaldehyde, toluene, or TVOC concentrations, this article shows, in addition to the distinction between sales and storage areas, how an unpacking task can affect an employee's exposure, and an example of the impact of ambient temperature on VOC concentrations. The results presented clearly highlight the issue of occupational exposure of workers in storage areas.

Deposition of E-cigarette aerosol in human airways through passive vaping.

Secondary exposure to e-cigarette aerosol (passive vaping) will soon become a pressing public health issue in the world. Yet, the current knowledge about respiratory depositions of e-cigarette aerosol through passive vaping in human airways is limited due to critical weaknesses of traditional experimental methods. To fill in this important knowledge gap, this study proposed a special approach involving an upgraded Mobile Aerosol Lung Deposition Apparatus (MALDA) that consists of a set of human airway replicas including a head airway, tracheobronchial airways down to the 11th lung generation, and a representative alveolar section. In addition to the comprehensive coverage of human airways, the MALDA is easily transportable for providing efficient estimations of aerosol respiratory deposition. In this study, the MALDA was first evaluated in the laboratory and then applied to estimate the respiratory deposition associated with passive vaping in an indoor real-life setting. The results showed that the respiratory deposition data aligned closely with the conventional respiratory deposition curves not only in the head-to-TB region but also in the alveolar region. The strengths of MALDA demonstrate great promise for a wide variety of applications in real-life settings that could provide crucial information for future public health and indoor air quality studies.

Numerical simulation of the influence of external urban environmental conditions in the building windows performance

This paper presents a numerical study of the influence of external urban environmental conditions, namely, the solar radiation, in the building windows performance. A software that simulates the building thermal behaviour with complex topology, in transient conditions, is developed and used in the study of indoor air quality and indoor thermal comfort of the occupants of a building, under typical summer conditions. As management strategy was implemented a control system to the Heating, Ventilation and Air Conditioning (HVAC) using the PMV (Predicted Mean Vote) index as controllable variable. The studied university building is located in a Mediterranean-type climate in the south of Portugal. The indoor thermal comfort, evaluated by the PMV index, and the indoor air quality, evaluated by the carbon dioxide concentration, were obtained for all occupied spaces. In order to evaluate the implemented control strategy a set of results was obtained for the situations with and without HVAC system control. To exemplify the results obtained, two large compartments were chosen, one with windows facing South and the other without windows. As main conclusion, it can be stated that the use of the HVAC system controllable by the PMV index allows acceptable levels of thermal comfort within the category C of the ISO 7730 standard, and acceptable levels of indoor air quality within the limit proposed by the ASHRAE 62.1 standard.

Field study of air environment perceptions and influencing factors in waiting spaces of general hospitals in winter cities

Subjective evaluation is an important topic in the study of hospital indoor air quality. This study investigates air environment perception and factors influencing that perception in different types of waiting spaces in large general hospitals. Field interviews and questionnaires were conducted in six typical large general hospitals in Harbin. First, we found that the rates of air environment dissatisfaction with halls spaces and corridor spaces were less than 20%. The air environment satisfaction with corridor spaces was significantly higher than it was with hall space, with an increase of 0.31; however, air environment acceptability was similar for both. Second, air stuffiness was the most important factor affecting air environment satisfaction. At the same time, crowd density and waiting time only affected satisfaction with hall spaces. The threshold for satisfaction with crowd density was approximately 1 person/m2. Participants reported the least amount of satisfaction with the quality of acoustic environments and air environments, but these rates of satisfaction were closely related. Finally, in hall spaces, the higher the air environment satisfaction, the lower the anxiety and the higher the pleasure. The air environment satisfaction experienced by younger participants was significantly higher than that of older participants, with an increase of 0.39. In corridor spaces, the air environment satisfaction of patients and females was higher than that of escorts and males, with an increase of 0.62 and 0.31 respectively. Based on these results, this study provides recommendations for optimizing the air environment in large general hospitals.

Analysis of Carbon Dioxide Concentration Prediction Model and Diffusion Tendency of Expiratory by Simultaneous Multipoint Sensing

Recent indoor air quality studies show that even 1000 parts per million (ppm) concentration of Carbon Dioxide (CO2) has an adverse effect on human intellectual activities. Therefore, it is required to keep the CO 2 concentration below a certain value in a room. In this study, in order to analyze the diffusion tendency of carbon dioxide by breathing, we constructed a simultaneous multi-point sensing system equipped with a carbon dioxide concentration sensor to measure indoor environment. Furthermore, it was evaluated whether the prediction model can be effectively used by comparing the prediction value by the model and the actually measured value from the sensor. The experimental results showed that CO 2 by exhaled breathing diffuses evenly throughout the room regardless of the sensor’s relative positions to the human test subjects. The existing model is sufficiently accurate in a room which has above at least a 0.67 cycle/h ventilation cycle. However, there is a large gap between the measured and the model’s predicted values in a room with a low ventilation cycle, and that suggests a measurement with a sensor still is necessary to precisely monitor the indoor air quality.

Indoor Air Quality in Passivhaus Dwellings: A Literature Review.

Indoor air quality (IAQ) is a critical consideration in airtight buildings that depend on mechanical ventilation, such as those constructed to the Passivhaus standard. While previous reviews of IAQ on Passivhaus-certified buildings foccused on offices, this study examines residential buildings. A summary of data collection methods and pollutant concentrations is presented, followed by a critical discussion of the impact of Passivhaus design strategies on IAQ. This review indicates that IAQ in Passivhaus-certified dwellings is generally better than in conventional homes, but both occupant behaviour and pollution from outdoor sources play a significant role in indoor concentrations. Moreover, there are differences in data collection and reporting methods. Many of the available studies depend on short-term IAQ monitoring of less than two weeks, making it difficult to determine the longer impact of housing design on IAQ and occupants’ well-being. There is also a lack of studies from non-European countries. Future research should focus on investigating associations between IAQ and Passivhaus design strategies in hot and humid climates, where evidence is particularly lacking. Further effort is also required to investigate potential links between occupant’s perception of IAQ and physical exposure to indoor pollution. Finally, the lack of homogeneous monitoring and reporting methods for IAQ studies needs to be addressed.

Association between human health and indoor air pollution in the Gulf Cooperation Council (GCC) countries: a review.

Studies on the assessment of indoor air pollutants in terms of concentration and characterization in the Gulf Cooperation Council (GCC) countries have been recently carried out. This review assesses the health effects associated with indoor air pollution exposures in GCC, including other air pollutants (siloxanes, flame retardants, synthetic phenolic antioxidants) which were not explored in a previous study. In addition, the influence of ventilation conditions due to different indoor environments was also investigated. It was revealed that there is a lack of human health assessment studies on most indoor air pollutants in almost all GCC countries, except the United Arab Emirates, Kingdom of Saudi Arabia and Kuwait, where few attempts were made for some specific pollutants. Commonly reported plausible health effects potentially associated with indoor air pollution were related to respiratory symptoms and sick building syndrome (SBS). Many of the current health assessment studies in GCC countries were based on predictions and/or estimates of exposures rather than clinically based observational studies. Measured ventilation levels and indoor air velocities in most buildings failed to meet the American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) threshold limits of 8 L/s/p and 0.18-0.25 m/s, respectively. Additionally, limited studies have investigated respiratory symptoms and SBS potentially attributable to poor ventilation in the region. It is highly recommended that future indoor air quality (IAQ) studies in GCC should focus more on epidemiologic and intervention studies.

Experimental study on tracer gas method for building infiltration rate measurement

The use of occupant-exhaled CO2 as the tracer gas enables the actual indoor infiltration rate to be measured, but the number and location of measuring points have a great impact on the accuracy of the results. This paper compares the experimental results from two tracer gas measurement techniques, decay with SF6 and constant injection with CO2 (exhaled by occupant). The results show a deviation of –9.0 to 7.4% between these two methods. This paper compares the result of this study with previous ones, and it confirmed that the CO2 method is an effective technique to calculate the infiltration rate in a room with a certain air volume when one measuring point is provided, and this is more accurate with good mixing of the indoor air. The impact of the measurement duration and distribution of indoor air on the measurement accuracy are also analysed. It is found that an extended monitoring period can reduce the impact of indoor air distribution. In actual measurements in residential building, it is recommended to select the data after occupants have been in the room for half an hour and to take measurements over 1 h after that. Practical application: Accurate air change per hour (ACH) is beneficial to the study of building energy consumption and indoor air quality. This paper explores the effectiveness of CO2 method, which provides useful reference for the large sample measurements of infiltration rates in residential buildings.

A Comparison Study of Indoor and Outdoor Air Quality in Nanjing, China

ABSTRACT Because humans spend much of their time in indoor microenvironments, the air quality indoors has attracted significant attention. This study simultaneously conducted real-time indoor observations and comprehensive outdoor measurements of O3, CO and PM2.5 in suburban Nanjing in eastern China from September to December 2018. The O3, CO and PM2.5 exhibited median indoor concentrations of 3.2 ppb, 395.8 ppb and 17.3 µg m–3, respectively, based on measurements in a room with closed windows and relatively regular daily indoor human activity, and median outdoor values of 30.5 ppb, 386.1 ppb and 37.2 µg m–3, resulting in median indoor-outdoor (I/O) ratios of 0.14, 1.01 and 0.46. Moreover, the indoor concentrations traced the outdoor variations with correlations of approximately 0.68, 0.82 and 0.82 for the O3, CO and PM2.5, respectively. During pollution episodes, the indoor O3 and PM2.5 concentrations reached about 30 ppb and 130 µg m–3, respectively. Both meteorological conditions (e.g., wind speed or relative humidity) and human activity indoors influenced the relationships between the indoor and outdoor concentrations, including the I/O ratios and time lag. A simplified indoor-outdoor mass-balance equation was developed to simulate the indoor concentrations, and the predictions fitted the observed data for most of the testing period, especially after considering the human activity indoors and limited penetration of particles. This study enhances our understanding of the indoor-outdoor relationships for gaseous and particulate matter concentrations in polluted areas such as the Yangtze River Delta and highlights the urgent need for improving indoor air quality in the megacities of China.