Perceived Indoor Air Quality Research Articles

Prevalence of sick building syndrome symptoms and subjective–objective indoor air quality of stores in underground shopping districts of Korea

Most sick building syndrome (SBS) studies have been conducted on workers in office buildings, whereas those assessing store workers in underground shopping districts (USDs) are limited. The purpose of this study was to determine the relationship between SBS symptoms of USD store workers and subjective–objective indoor air quality (IAQ). In 2020, 128 stores across 10 USDs in Korea were assessed. One worker in each store was asked about 16 SBS symptoms and seven subjective IAQ perceptions (categorized into two levels [Yes or No]) via questionnaire. Objectively, indoor concentrations of aldehydes and volatile organic compounds (VOCs) were measured in each store. The prevalence of SBS symptoms within the previous month was 16.4%, 39.1%, 28.9%, and 43.8% for skin, eye irritation, respiratory, and general symptoms, respectively. IAQ perceptions were correlated with the concentrations of several aldehyde compounds and VOCs. After adjusting for demographic (e.g., sex, age, or education) and job-related variables (e.g., working hours), logistic regression models showed all SBS symptom groups (except skin) were significantly associated with IAQ perception. Environmentally, eye irritation symptoms were associated with n-butanol, n-heptane, and xylene; respiratory symptoms with n-heptane; and general symptoms with benzene, n-heptane, and decanal concentrations. The association of SBS symptoms with aldehyde compounds and VOCs suggests that the chemical levels in USD stores may require further control to reduce these symptoms in workers. As controlling the products sold or cooking activities within USDs is difficult, increasing ventilation rates or using low-VOC-emission building materials may be more practical.

Analyzing the Perception of Indoor Air Quality (IAQ) from a Survey of New Townhouse Residents in Dubai

According to UAE Health Ministry and Dubai Healthcare City reports, 15% of Dubai residents have a chronic respiratory disease such as asthma. Moreover, 90% of the 150,000 patients at Al Ain Hospital suffered from upper respiratory tract respiratory diseases, bronchitis, or asthma. Sick Building Syndrome (SBS) has emerged as a social problem in the United Arab Emirates (UAE). The Dubai Municipality regulates Indoor Air Quality (IAQ) with strict stipulations before moving in, but they are relatively passive about regulations related to healthy living. This paper aims to explore the actual state of perception of the IAQ from townhouse residents in Dubai, UAE. The characteristics of the resident’s perceptions of the IAQ are identified, and the influential factors affecting residents’ perceptions of IAQ are extracted. As a methodology, the survey was conducted on four townhouse projects in Dubai from December 2021 to January 2022. A total of 114 copies were distributed, and 98 documents were used. Analysis of the survey data was processed using IBM SPSS Statistics 26.0. The results showed a statistically significant correlation between the cognitive and anxiety levels of SBS with the presence or absence of experience. It was statistically confirmed that the most influential factors were the age of the children and the occupancy time of housewives and children. This is because of the perception that wives who spend a relatively long time in the house and their young children are exposed to indoor air pollution for a long period of time and are easily affected by this influence on the concerns about young children about SBS. Ninety-five percent of the respondents answered that they knew more than average about SBS, indicating a very high level of awareness. As for the degree of anxiety, 87.0% of the respondents felt higher levels of anxiety than usual. However, most of them did not know or were indifferent to the understanding of the air quality improvement methods. The awareness of actual contents was lower than that of residents who assessed that they knew about SBS.

Trimester-specific association of perceived indoor air quality with antenatal depression: China Medical University Birth Cohort Study.

Antenatal depression is associated with adverse birth and long-term outcomes for mothers and children. Pregnant women spend 90% of time indoors; however, the association between indoor air quality and risk of antenatal depression has not been established. In this study, we aim to determine the total and trimester-specific association of perceived indoor air quality (PIAQ) with antenatal depression. A total of 2166 pregnant women were enrolled during the first trimester and evaluated during the second and third trimesters in the China Medical University Birth Cohort Study, a prospective pre-birth cohort study in northeastern China. PIAQ scores were obtained during each of three trimesters, which a higher score indicated a worse indoor air quality. Antenatal depression was screened using an Edinburgh Postnatal Depression Scale (EPDS) and defined as an EPDS score ≥ 9. Prevalence of antenatal depression was 26.7%, 20.6%, and 20.9% during the first, second, and third trimesters, respectively. A higher PIAQ score was positively associated with a depression score throughout pregnancy (β=0.27, 95% CI=0.15-0.39). Trimester-specific adverse PIAQ exposure was associated with a higher depression score in the same trimester, but not with a higher score in a subsequent trimester. A dose-response pattern and incremental increases in risk of depression were observed with calculated adverse PIAQ exposures across all three trimesters, with the highest risk (OR=3.24; 95% CI=2.28-4.78) among women with adverse PIAQ across all three trimesters. The hazardous association between adverse PIAQ exposure and risk of depression were less pronounced among women with higher physical activity levels (P for interaction < 0.001). The results of present study provided important evidence that pregnant women's mental health was linked to indoor air quality during pregnancy. These findings could be helpful in the development of guidelines to prevent antenatal depression by improving indoor air quality.

Sweet foods dietary pattern enhances negative associations of perceived indoor air quality during pregnancy with postpartum depression.

Postpartum depression (PPD) is possibly caused by indoor air pollution and may be modified by maternal diet during pregnancy. Using the data from a prospective cohort study, we examined the interaction between indoor air quality and maternal dietary patterns on PPD development. A perceived indoor air quality (PIAQ) score was used to assess indoor air pollution. A higher PIAQ score indicated a worse indoor air quality. Women with higher PIAQ scores were at increased risk for PPD (tertile 3 vs. tertile 1, odds ratio [OR]=2.12, 95% confidence interval [CI]=1.37-3.29). Compared with a lower adherence to a "sweet foods pattern" (OR=1.20, 95% CI=0.66-2.18), a higher adherence to a "sweet foods pattern" enhanced the hazardous associations of the PIAQ on PPD (OR=3.09, 95% CI=1.81-5.27, adjusted p for interaction=0.044). Higher adherence to a "whole grain-seafood pattern" and lower adherence to a "traditional pattern" also increased the risk for PPD, although the p values for the interaction were not significant. Our findings provide further evidence of the link between diet during pregnancy, air pollution, and PPD, and it can be used to develop PPD prevention strategies.

Exploring the impact of perceived control on thermal comfort and indoor air quality perception in schools

Perceived control, as an integral part of the psychological impact, can be considered an important factor in the adaptive thermal comfort model. With the aim of exploring the relationship between perceived control and thermal comfort and indoor air quality (IAQ) in school buildings, a three-month field study was conducted during the heating season involving 26 school classrooms in the Italian Province of Pisa. The experimental campaign was conducted by carrying out measurements of thermal and IAQ parameters. In addition to instrumental measurements, subjective analysis was carried out by collecting 859 questionnaires filled in by students concurrently with objective measurements. The study demonstrate that the thermal neutral temperatures of the occupants with and without perceived control are, respectively, 21.7 °C and 22.2 °C and that the enhancing influence of the perceived control on the thermal sensation decreases with the increase of indoor operative temperature. The study shows that the perception of IAQ by the occupants is inversely proportional to the operative temperature and CO2 concentration. Furthermore, it emerges that students with the perception of control express better subjective judgments regarding the IAQ. It is suggested to ensure environmental control in order to improve indoor comfort and decrease the energy demand for heating.

Evaluating machine learning models to classify occupants’ perceptions of their indoor environment and sleep quality from indoor air quality

ABSTRACT A variety of factors can affect a person’s perception of their environment and health, but one factor that is often overlooked in indoor settings is the air quality. To address this gap, we develop and evaluate four Machine Learning (ML) models on two disparate datasets using Indoor Air Quality (IAQ) parameters as primary features and components of self-reported IAQ satisfaction and sleep quality as target variables. In each case, we compare models to each other as well as to a simple model that always predicts the majority outcome. In the first analysis, we use open-source data collected from 93 California residences to predict occupant’s satisfaction with their indoor environment. Results indicate building ventilation rate, Relative Humidity (RH), and formaldehyde are most influential when predicting IAQ perception and do so with an accuracy greater than the simplified model. The second analysis uses IAQ data gathered from a field study we conducted with 20 participants over 11 weeks to train similar models. We obtain accuracy and F1 scores similar to the simplified model where PM2.5 and TVOCs represent the most important predictors. Our results underscore the ability of IAQ to affect a person’s perception of their built environment and health and highlight the utility of ML models to explore the strength of these relationships. Implications: The results from this study show that two outcome variables – occupant’s indoor air quality (IAQ) satisfaction and perceived sleep quality – are related to the measured IAQ parameters but not heavily influenced by typical values measured in apartments and homes. This study highlights the ability of machine learning models as exploratory analysis tools to determine underlying relationships within and across datasets in addition to understanding the importance of certain features on the outcome variable. We compare four different models and find that the random forest classifier has the best performance in both analysis on IAQ satisfaction and perceived sleep quality. It is a suitable model for predicting IAQ-related subjective metrics and also provides value insight into the feature importance of the IAQ parameters. The accuracy of any of these machine learning models in predicting occupants’ comfort or sleep quality is limited by the dataset size, how data is collected, and range of data. This study identifies the factors that are important to IAQ perception: ventilation rate, relative humidity, and concentrations of formaldehyde, NO2, and particulate matter. It indicates that sensors that can measure these variables are necessary for future, related studies that model occupants’ IAQ satisfaction. However, this study does not find strong relationships between any of the IAQ parameters measured in this study and perceived sleep quality despite the logical pathway between these many pollutants and respiratory issues. A prediction model of IAQ perception or sleep quality can be integrated into home management systems to automatically adjust building operations such as ventilation rates in smart buildings. Once buildings are equipped with a network of low-cost sensors that measure concentrations of pollutants and operating conditions of the ventilation system, the prediction model can be used to predict the occupants’ comfort and facilitate the control of the ventilation system.

Effects of covid-induced lockdown on inhabitants’ perception of indoor air quality in naturally ventilated homes

The intensified indoor living during the spring 2020 lockdown, with enhanced user awareness of the prevailing conditions in their homes, constituted a natural stress test for the housing design in place today. Surveys conducted during this period have yielded lessons for designing better intervention strategies for the residential sector, taking into account the systematic morphological and economic limitations of the buildings concerned. These considerations should inform the development of policies and strategies for improving environmental quality compatible with lower residential energy consumption and higher quality of life. This study explores the effect of occupant behaviour on home ventilation and the perception of the impact of indoor air quality on user health before and during lockdown. The method deployed consisted in monitoring environmental variables and conducting user surveys before and after restrictions came into force. The findings showed that prior to lockdown, occupants were unaware of or paid little heed to changes in indoor air quality, failed to perceive stuffiness, and, as a rule, reported symptoms or discomfort only at night during the summer months. During lockdown, however, users came to attach greater importance to air quality, and a greater sensitivity to odours and a heightened awareness of CO2 concentration prompted them to ventilate their homes more frequently. In the spring of 2020, occupants also indicated a wider spectrum of indisposition, in particular in connection with sleep patterns.

Impact of indoor aroma on students’ mood and learning performance

Indoor environment has an appreciable impact on occupants' mood, health and performance. Among numerous indoor environmental components, indoor air quality is often considered to be one of the most crucial ones. While odor is a decisive factor for evaluating perceived indoor air quality, its effects - particularly the positive effects of pleasant aromas - on human responses and performance have yet to be revealed. In this study, experiments were conducted to investigate the effect of indoor aroma on students' mood and learning performance. Participants comprised 76 university students and they performed two learning tasks under one of the four odor conditions: “control (aromaless)”, “rosemary”, “lemon”, and “peppermint.” First, the way in which students sense the indoor aroma in a study space was investigated using several mood scales, including odor intensity, pleasantness, preference, acceptability, and impression. Second, the influence of indoor aroma on learning and memory performance was quantitatively assessed using a reading task and a verbal memory task. Lastly, the impacts of odor preference on subjective evaluation and performance were explored. This experiment showed that subjective evaluations were significantly different before and after olfactory adaptation, particularly in the rosemary condition. Of all three aroma conditions, the lemon aroma had the highest preference and led to the highest scores in the memory task. Although the significant impact of indoor aroma on learning performance was not detected, our results indicated that pleasant aroma has the potential to enhance students’ mood and learning performance.

A study on human perception in aircraft cabins and its association with volatile organic compounds

More than 8 million people fly on commercial aircraft each day with approximately 5% having a pre-existing respiratory disease. Thus it is necessary to provide high air quality in aircraft to protect public health. Volatile organic compounds (VOCs) present in aircraft cabins are suspected to contribute to the reported complaints. We investigated concentrations of VOCs, air temperature, relative humidity, and CO2 concentrations in a total of 46 flights, including 26 Chinese domestic flights and 20 international flights. We focused on the data from the cruising phase without meal serving in which the air supply and air recirculation were steady. A total of 284 passengers (i.e., 101 on international flights and 183 on Chinese domestic flights) were invited to participate in questionnaire surveys in this phase. We performed a linear mixed model analysis by controlling for potential confounders (age, gender, smoke habits, and history of allergy) to study associations between VOCs exposures and passengers' complaints. Xylene was significantly associated with irritations of the eyes, nose, and throat on both international and domestic flights, with antilog beta values from 1.12 to 1.28 (p < 0.05). The association of some aldehydes (i.e., nonanal, decanal, and heptanal), which are potential oxidation products with ozone, with passengers’ sensory irritations was also significant, especially during international flights (antilog beta values: 1.19–1.22). It indicates that VOCs, especially xylene and aldehydes, in aircraft cabins may influence the perceived indoor air quality and complaints among passengers.

The appearance of indoor plants and their effect on people's perceptions of indoor air quality and subjective well-being

• Indoor plant appearance impacts people's responses. • Interest and beauty of indoor plants benefits well-being. • Perceptions of indoor air quality are influenced by healthiness and appearance of plants. • Shape ranked as the most important characteristic affecting plant attractiveness. • People prefer indoor plants with rounded canopy contours.

Towards Personalization of Indoor Air Quality: Review of Sensing Requirements and Field Deployments.

As humans spend more time indoors, ensuring acceptable indoor air quality (IAQ) through ubiquitous sensing systems has become a necessity. Although extensive studies have been conducted on the IAQ sensing systems, a holistic review of the performance and deployment of Ubiquitous IAQ Sensing (UIAQS) systems with associated requirements in IAQ sensing standards is still lacking. In this study, we first reviewed IAQ pollutants and other IAQ-related factors and the associated requirements in the prominent IAQ sensing standards. We found that while non-pollutant factors are influential on occupants’ perception of IAQ and their satisfaction, they do not have evaluation metrics in the IAQ standards. Then, we systematically reviewed field studies on UIAQS technologies in the literature. Specific classes of information were recorded and analyzed further. We found that the majority of the UIAQS systems did not meet the requirements of the prominent IAQ sensing standards and identified four primary research gaps. We concluded that a new holistic and personalized approach that incorporates UIAQS measurements and subjective feedback is needed. This study provides valuable insights for researchers and policymakers to better improve UIAQS technologies by developing personalized IAQ sensors and sensing standards.

An effect of numerical data through monitoring device on perception of indoor air quality

Despite a growing interest in indoor air quality (IAQ), a scientific basis for human self-awareness and understanding of IAQ has yet to be provided. To fill this research gap, this study examined the effect of numerical data through monitoring devices on the occupants’ perception of IAQ. Therefore, an experiment was planned to evaluate the perceived IAQ based on a self-report questionnaire among ten subjects in an office environment. The experiment was divided into three sessions, with a classification model built for each session using automated machine learning and then derived variable importance for predictor variables. Results showed that when occupants did not check the numerical data of IAQ factors, they tended to perceive IAQ based on the perceived thermal comfort. In addition, occupants made a biased judgment of the current IAQ condition based on the past perceived IAQ checked 30 min ago. When occupants checked the numerical data of IAQ factors, they responded more sensitively to IAQ factors than to thermal environment factors when perceiving IAQ conditions. The results of this study confirmed that real-time numerical data of IAQ factors measured using monitoring devices are essential for occupants to perceive and judge the current IAQ clearly.

Characterizing the Environmental Health Literacy and Sensemaking of Indoor Air Quality of Research Participants.

This study is based on in-depth semi-structured interviews with the participants of an indoor air quality monitoring study. The purpose of the interviews was to capture participants’ perceptions of indoor air quality and engage them in a discussion of those factors that influenced their behavior. Interview study participants (n = 20) noted the importance of family health concerns and their own sensory awareness of possible contaminants. They discussed their level of personal control over their home environment as well as their access to needed resources. This study is based on grounded theory and applies interpretivist epistemological methods. Study findings offer insights into how people perceive their home environment and what influences their decision making and action. Analyses indicate that perceived agency, risk perception, access to resources, and information all influenced participants’ sense of ability to take action as well as their interest in taking action. These insights serve to challenge some of the current work in environmental health literacy which tends to focus on and measure an individual’s knowledge or skills. Our analysis suggests that consideration be given to a number of factors that include perceived agency, access to resources, and the quality of information provided.

Why do people use portable air purifiers? Evidence from occupant surveys and air quality monitoring in homes in three European cities

ABSTRACT One of the most widely available technologies to clean the air in homes of particulate matter of less than 2.5 µm in diameter (PM2.5), known to have negative health impacts, are portable home air purifiers (HAPs). This paper presents research which (1) explored the effectiveness of HAPs in real-world conditions in 57 homes in three European cities; (2) examined if HAPs affect users’ perceptions of the indoor air quality (IAQ) at home; and (3) considered the motivations for occupants’ operation of HAPs. Results from this study found that PM2.5 concentrations in bedrooms were reduced by 45% to 69%; perceptions of IAQ were not correlated with measured high PM2.5 levels; occupants reported the HAPs to have a ‘cooling’ effect, which may explain why the predominant driver of HAP use was thermal comfort, rather than IAQ, in all three cities. The latter finding was supported by a statistically significant increase in the probability of HAP use with increasing indoor temperatures. If the operation of HAPs can be managed, or fully automated, to reflect indoor air pollution levels rather than thermal conditions, better pollutant reduction would be feasible and their use to reduce PM2.5 may help mitigate the negative health effects of exposure whilst at home.

I-CUB: ‘Indoor Climate-Users-Buildings’: Relationship between measured and perceived indoor air quality in dwellings

Assessment of indoor environmental quality has recently moved to a combined methodology of both measurements and questionnaire surveys. In this study, we have used data from the national survey of the Swedish housing stock, BETSI, conducted in 2007/2008, during the heating season. The study included, among others, measurement of selected indoor air pollutants and an extensive questionnaire survey on the occupants’ perception of their dwellings. Measured concentrations of the air pollutants NO2, TVOCs and formaldehyde were aggregated into one Indoor Air Pollution Index (IAPI) on a continuous scale between 0 (excellent Indoor Air Quality; IAQ) and 10 (poor IAQ). The perceived IAQ was assessed by the occupants on a 5-point category scale from very good to very poor. On the entire scale of IAPIs, 92% of the respondents in single-family houses perceived the IAQ as very good or good and 8% as acceptable, while in the apartments, the ratings ‘very good’ and ‘good’ accounted for 58%, acceptable for 33% and 9 % for ‘poor’ and ‘very poor’, respectively. In both building types, the tendency of IAPIs was shifted to lower values (good IAQ). Analysis of IAPI-medians showed no statistically significant differences between and among the air quality perception ratings.

Draught sensation assessment in an occupied space heated by stratified ventilation system: Attachment ventilation with relayed fans

The application of stratified ventilation systems for winter heating brings out the doubt of draught issues on the lower part of body. The purpose of this study is to quantify the thermal sensation and air movement acceptability of occupants in an occupied space with the stratified convective–heating systems. Twenty subjects participated in eighteen trials and they were blinded to test conditions. Three air temperatures of 20.5, 21.5 and 23.0 °C and three local air speeds of 0.4, 0.6 and 0.8 m/s are chosen as the examined parameters in the warm air lake. Two shoe types of low–cut and high–top being considered for providing different protection on ankles were also used. Local and overall thermal sensation, thermal comfort and acceptability, air movement acceptability, the preference on thermal environment and air movement were collected. Perceived indoor air quality and dry eye symptoms were also acquired. Results demonstrated that subjects were sensitive to local air movement at both calves and ankles rather than the ankles only. Low air temperature (<23.0 °C) and high air speed (>0.4 m/s) in warm air lake may cause 20–65% of subjects to complain about the unacceptable air movement. High–top shoes could increase the air movement acceptability on ankles by 15% but little effects on calves were discovered. Only 7% of the subjects reported eye dryness in all tested conditions and almost all subjects could accept the indoor air quality. This work may help improve the understanding of draught sensation on lower body parts in an occupied space with the stratified convective–heating system.

HVAC energy savings, thermal comfort and air quality for occupant-centric control through a side-by-side experimental study

Building sensing technologies have evolved rapidly in the last two decades in aid of monitoring building environment and energy system performance. A series of occupancy sensing systems were developed to track the occupant behavior in the indoor space. Occupancy-based building system control is defined as a control method that adjusts the building system operation schedules and setpoints based on the measured occupant behavior and has been identified as a smart building control strategy that can improve building energy efficiency as well as occupant comfort. Some studies demonstrated energy-saving potential and comfort-maintaining capability from occupancy-based control. This study adopted a first-of-its-kind side-by-side experimental approach to quantify the performance of the occupancy-based control in commercial buildings. Three state-of-the-art occupancy sensing technologies were integrated into the real-time Heating, Ventilation, and Air-Conditioning (HVAC) system control in this study. Their detection accuracy and its effectiveness on energy-saving and thermal comfort were analyzed. It was found that the occupancy-based control can maintain good thermal comfort and perceived indoor air quality with a satisfaction ratio greater than 80%. Although the daily energy-saving varied with occupancy sensor accuracy and outdoor environment conditions, the weekly averaged energy saving was between 17 and 24%.

Temperature-dependent ventilation rates might improve perceived air quality in a demand-controlled ventilation strategy

The aim of the Best Vent project was to find the optimal control strategy for demand-controlled ventilation (DCV) without compromising on indoor air quality. In this paper, we discuss control strategies that would ensure acceptable perceived air quality for unadapted users.This study is a part of a series of field studies where sensory panels of untrained persons visited classrooms at a school. The sensory panel visited classrooms occupied by different user groups, at different ventilation rates and temperatures, and in empty classrooms at different ventilation rates, and with different pollutant loads. This study aims to assess whether it would be reasonable to control the supply airflow rate towards a higher CO2 setpoint at low air temperature, and still maintain the same perceived indoor air quality upon entry. The results indicate that the perception of indoor air quality does not deteriorate at higher CO2 concentrations when the air temperature is kept at 21 °C as opposed to at 24 °C. Furthermore, an increase in air temperature yielded poorer perceived air quality scores at similar CO2 concentrations in the classrooms.Our results indicate that a DCV-control strategy with a higher CO2 setpoint in classrooms at low temperatures would not compromise perceived air quality. Further research would be needed to assess whether the same is true for indoor climate-related symptoms or performance.

An Investigative Study on Perceived Indoor Air Quality During COVID-19 Lockdown in India

The air we breathe is a worldwide concern, especially in developing countries like India. Recently, the coronavirus pandemic resulted in restricted activities which showed noteworthy improvement in ambient air. As it hassled people to reach home, corporations began work from home schemes. Conforming to WHO, coronavirus is airborne as transmission cannot be disregarded in crowded and inadequately ventilated indoor spaces. A high-density population spending more time indoors raises questions on existing indoor requirements of accommodating a healthy long-duration inhabitation. Indoor time is also likely to extend with higher than before acceptance to online learning, entertainment, and shopping. Even though air pollution is mostly thought of as an outdoor concern, studies suggest that the air indoors can be contaminated as well, and sometimes even more than the air outside. India has shown growth in building-related illness, whereas lack of specific standards and limited research raises a concern. The countrywide lockdown to control the coronavirus situation in India has brought overwhelming improvement in the air quality due to restricted anthropogenic activities. This study is based on a pan India survey and ambient air quality data by the central pollution control board to understand the change in outdoor air pollution and indoor air quality perception before and during the lockdown in 205 cities categorized as per government guidelines. It also aims to understand the relationship between various parameters and perceived indoor air quality. Even though the COVID-19 pandemic has bought unprecedented health and economic crisis, the pandemic may act as a promoter for healthy and sustainable indoor environments.

Which Risk Factors Matter More for Psychological Distress during the COVID-19 Pandemic? An Application Approach of Gradient Boosting Decision Trees.

Background: A growing body of scientific literature indicates that risk factors for COVID-19 contribute to a high level of psychological distress. However, there is no consensus on which factors contribute more to predicting psychological health. Objectives: The present study quantifies the importance of related risk factors on the level of psychological distress and further explores the threshold effect of each rick factor on the level of psychological distress. Both subjective and objective measures of risk factors are considered in the model. Methods: We sampled 937 individual items of data obtained from an online questionnaire between 20 January and 13 February 2020 in China. Objective risk factors were measured in terms of direct distance from respondents’ housing to the nearest COVID-19 hospital, direct distance from respondents’ housing to the nearest park, and the air quality index (AQI). Perceived risk factors were measured in regard to perceived distance to the nearest COVID-19 hospital, perceived air quality, and perceived environmental quality. Psychological distress was measured with the Kessler psychological distress scale K6 score. The following health risk factors and sociodemographic factors were considered: self-rated health level, physical health status, physical activity, current smoker or drinker, age, gender, marital status, educational attainment level, residence location, and household income level. A gradient boosting decision tree (GBDT) was used to analyse the data. Results: Health risk factors were the greatest contributors to predicting the level of psychological distress, with a relative importance of 42.32% among all influential factors. Objective risk factors had a stronger predictive power than perceived risk factors (23.49% vs. 16.26%). Furthermore, it was found that there was a dramatic rise in the moderate level of psychological distress regarding the threshold of AQI between 40 and 50, and 110 and 130, respectively. Gender-sensitive analysis revealed that women and men responded differently to psychological distress based on different risk factors. Conclusion: We found evidence that perceived indoor air quality played a more important role in predicting psychological distress compared to ambient air pollution during the COVID-19 pandemic.