Assessment of indoor environmental quality in existing multi-family buildings in North-East Europe

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

Background

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.

Method

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).

Generalisability

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.

Research aim

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.

Impact of improved indoor environment on recovery from COVID-19 infections: a review of literature

Purpose

This study aims to explore the impact of the indoor environment on recovery from COVID-19 infections. Extant literature on the impact of the four key themes of the indoor environment (indoor air quality, indoor thermal quality, daylighting and visual comfort, and acoustic comfort) on COVID-19 infection and recovery rates were reviewed.

Design/methodology/approach

Data collection for this study was based on extant literature within the Scopus database and scoped to a time frame of 2020–2021 because the topical issue of indoor environmental quality (IEQ) and its impact on COVID-19 arose in the wake of the pandemic. In total, 224 documents were systematically desk reviewed from various journals.

Findings

The study identified that air pollutants such as PM2.5 and PM10 as well as air-conditioned places, low ambient temperatures, poor ventilation and no views of the outdoor environment were deteriorating factors for COVID-19 patients. On the other hand, proper ventilation, the use of air cleaners, views of the outdoor environment and allowance for ample daylighting were improvement factors for COVID-19 patients. The inter-relationship of the various concepts was presented in an ontology chart.

Practical implications

As COVID-19 still exists and keeps evolving, this study provides suggestions to industry professionals, especially health-care Facility Managers, to create a post-pandemic environment focusing on the IEQ and finding long-term and reliable solutions for the well-being of occupants. Adaptability is crucial. New, creative technology solutions are being introduced daily, but it is up to the facility managers and health-care professionals to analyse and specify the most cost- and outcome-effective technologies for their facility.

Originality/value

The study brought to light the pivotal role of the indoor environment on the health and well-being of occupants, particularly in the contraction, spread, prevention and control of infectious diseases such as COVID-19.

Temperature and indoor environments

From the thermodynamic perspective, the term temperature is clearly defined for ideal physical systems: A unique temperature can be assigned to each black body via its radiation spectrum, and the temperature of an ideal gas is given by the velocity distribution of the molecules. While the indoor environment is not an ideal system, fundamental physical and chemical processes, such as diffusion, partitioning equilibria, and chemical reactions, are predictably temperature-dependent. For example, the logarithm of reaction rate and equilibria constants are proportional to the reciprocal of the absolute temperature. It is therefore possible to have non-linear, very steep changes in chemical phenomena over a relatively small temperature range. On the contrary, transport processes are more influenced by spatial temperature, momentum, and pressure gradients as well as by the density, porosity, and composition of indoor materials. Consequently, emergent phenomena, such as emission rates or dynamic air concentrations, can be the result of complex temperature-dependent relationships that require a more empirical approach. Indoor environmental conditions are further influenced by the thermal comfort needs of occupants. Not only do occupants have to create thermal conditions that serve to maintain their core body temperature, which is usually accomplished by wearing appropriate clothing, but also the surroundings must be adapted so that they feel comfortable. This includes the interaction of the living space with the ambient environment, which can vary greatly by region and season. Design of houses, apartments, commercial buildings, and schools is generally utility and comfort driven, requiring an appropriate energy balance, sometimes considering ventilation but rarely including the impact of temperature on indoor contaminant levels. In our article, we start with a review of fundamental thermodynamic variables and discuss their influence on typical indoor processes. Then, we describe the heat balance of people in their thermal environment. An extensive literature study is devoted to the thermal conditions in buildings, the temperature-dependent release of indoor pollutants from materials and their distribution in the various interior compartments as well as aspects of indoor chemistry. Finally, we assess the need to consider temperature holistically with regard to the changes to be expected as a result of global emergencies such as climate change.

Spatiotemporal variation in residential PM2.5 and PM10 concentrations in China: National on-site survey

BACKGROUND

Significant efforts have been directed toward addressing the adverse health effects of particulate matter, while few data exist to evaluate indoor exposure nationwide in China.

OBJECTIVES

This study aimed to investigate dwellings particulate matter levels in the twelve cities in China and provide large data support for policymakers to accelerate the legislative process.

METHODS

The current study was based on the CIEHS 2018 study and conducted in 12 cities of China. A total of 2128 air samples were collected from 610 residential households during the summer and winter. Both PM₁₀ and PM_2.5 were detected with a light-scattering dust meter in both the living room and bedroom. The Wilcoxon rank-sum test was performed to evaluate the correlations between PM_2.5 and PM₁₀ concentrations and both sampling season and site. Ratios of the living room to bedroom were calculated to evaluate the particulate matter variation between rooms. Hierarchical clustering was used to probe the question of whether the concentration varies between cities throughout China.

RESULTS

The geometric means of the PM_2.5 in living rooms and bedrooms were 39.80 and 36.55 μg/m³ in the summer, and 70.97 and 67.99 μg/m³ in the winter, respectively. In the summer, approximately 70 % of indoor dwelling PM_2.5 exceeded the limit of 25 μg/m³, and for PM₁₀ approximately 60 % of dwellings demonstrated levels higher than 50 μg/m³; the corresponding values were over 90 % and 80 % in winter, respectively. In Shijiazhuang, Lanzhou, Luoyang and Qingdao, the geometric means of the PM_2.5 concentrations were observed to be 1.5 to 4.3 times higher during winter than during summer; similar concentrations in summer and winter were observed in Harbin, Wuxi, and Shenzhen, while the PM_2.5 concentrations in Panjin were approximately 1.5 times higher in summer than in winter. There was no significant difference in particulate matter concentrations between the living rooms and bedrooms. Scatter plots showed that cities with low GDP and a small population had higher concentrations, while Shenzhen, which has a higher GDP and a large permanent population, had a relatively low concentration of particulate matter.

CONCLUSIONS

Our results suggest that indoor air pollution is a severe problem in China. It is necessary to continue monitoring indoor air quality to observe the changing trend under the tremendous effort of the Chinese government.

Volatile Organic Compounds in Underground Shopping Districts in Korea

Underground shopping districts (USDs) are susceptible to severe indoor air pollution, which can adversely impact human health. We measured 24 volatile organic compounds (VOCs) in 13 USDs throughout South Korea from July to October 2017, and the human risk of inhaling hazardous substances was evaluated. The sum of the concentrations of the 24 VOCs was much higher inside the USDs than in the open air. Based on factor analysis, six indoor air pollution sources were identified. Despite the expectation of a partial outdoor effect, the impacts of the indoor emissions were significant, resulting in an indoor/outdoor (I/O) ratio of 5.9 and indicating elevated indoor air pollution. However, the effects of indoor emissions decreased, and the contributions of the pollution sources reduced when the USD entrances were open and the stores were closed. Although benzene, formaldehyde, and acetaldehyde exhibited lower concentrations compared to previous studies, they still posed health risks in both indoor and outdoor settings. Particularly, while the indoor excess cancer risk (ECR) of formaldehyde was ~10 times higher than its outdoor ECR, benzene had a low I/O ratio (1.1) and a similar ECR value. Therefore, indoor VOC concentrations could be reduced by managing inputs of open air into USDs.

Determination of optimal ventilation rates in educational environment in terms of radon dosimetry

INTRODUCTION

New and renovated energy efficient buildings with minimised ventilation rates together with increased building airtightness are often associated with higher indoor radon concentrations compared to the concentrations in existing buildings. The purpose of our study is to analyse the problem associated with the increased radon concentration and ventilation requirements and recommendations in schools. The radon concentration was critically assessed by varying the design ventilation rates (DVRs) within fifteen cases according to legislative requirements and recommendations. The case study is a branch primary school in western part of Slovenia situated in a radon prone area.

METHODS

Radon (²²²Rn) concentrations were simulated in the classroom, using CONTAM 3.2.

PROGRAM

For validation, measurements were performed on 8 measuring days in September and 6 measuring days in March. The simulated and measured ²²²Rn concentrations are well correlated for all measurement days, with the simulated/measured ratio of 0.85-1.39. In order to define optimal DVRs in terms of dosimetry, the effective dose and its ratio to the worldwide average effective dose at workplace, received by radon progeny in 950 h (expected effective dose, 0.13 mSv/y), were calculated for each case.

RESULTS

Simulations showed that the highest radon concentrations were observed in case 1 with a DVR of 79.6 m³/h (621 Bq/m³) and case 4 with a DVR of 69.4 m³/h (711 Bq/m³), both defined by national regulations. The calculated values in both cases exceeded the national reference value for radon (300 Bq/m³) by 2.1 times and 2.4 times, and the WHO guideline value (100 Bq/m³) by 6.2 times and 7.1 times, respectively. The simulations are in line with the results of radon dosimetry. Both DVRs correspond to the highest effective doses, 1.88 mSv/y (about 14-fold higher than expected effective dose) for case 1 and 2.15 mSv/y (about 17-fold higher than expected effective dose) for case 4. Case 11_Cat I with a DVR of 1999.7 m³/h defined by EN 15251: 2007 resulted in minimal Rn concentration (35 Bq/m³) and corresponds to the lowest effective dose 0.11 mSv/y and its ratio to the expected effective dose 0.8.

CONCLUSIONS

Ventilation is an immediate measure to reduce radon concentration in a classroom and it must be performed in line with other holistic measures to prevent and control radon as a health risk factor.

A Systematic Review of Air Quality Sensors, Guidelines, and Measurement Studies for Indoor Air Quality Management

The existence of indoor air pollutants—such as ozone, carbon monoxide, carbon dioxide, sulfur dioxide, nitrogen dioxide, particulate matter, and total volatile organic compounds—is evidently a critical issue for human health. Over the past decade, various international agencies have continually refined and updated the quantitative air quality guidelines and standards in order to meet the requirements for indoor air quality management. This paper first provides a systematic review of the existing air quality guidelines and standards implemented by different agencies, which include the Ambient Air Quality Standards (NAAQS); the World Health Organization (WHO); the Occupational Safety and Health Administration (OSHA); the American Conference of Governmental Industrial Hygienists (ACGIH); the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE); the National Institute for Occupational Safety and Health (NIOSH); and the California ambient air quality standards (CAAQS). It then adds to this by providing a state-of-art review of the existing low-cost air quality sensor (LCAQS) technologies, and analyzes the corresponding specifications, such as the typical detection range, measurement tolerance or repeatability, data resolution, response time, supply current, and market price. Finally, it briefly reviews a sequence (array) of field measurement studies, which focuses on the technical measurement characteristics and their data analysis approaches.

PM2.5 mass concentration variation in urban residential buildings during heating season in severe cold region of China: A case study in Harbin

Recent years, people pay great attention to fine particle matter (PM_2.5) in indoor environment due to its negative impacts on health. Household cooking and severe air pollutant aggravate indoor PM_2.5 level, especially during heating season in severe cold region of China. To find the variation of actual household PM_2.5 influenced by both cooking activities and penetration from outdoor environment, a field measurement of PM_2.5 concentrations in living room of residential buildings was conducted in Harbin, China. Firstly, six households in urban residence were selected to monitor the indoor PM_2.5 mass concentration sequentially. Simultaneously, outdoor PM_2.5 concentrations, temperature and indoor occupants' behavior were collected. Secondly, indoor to outdoor (I/O) ratios of PM_2.5 in each household during monitoring campaigns were calculated. Influence of cooking activities and outdoor penetration on indoor PM_2.5 concentrations in living room were also analyzed. Thirdly, some discussions were done for explanation of variation of PM_2.5 in urban residential buildings. Results showed that the average PM_2.5 mass concentrations varied from 11.7 to 48.6 μg/m³ indoor, while average I/O ratio value ranged from 0.33 to 1.23. Cooking in kitchen had significant impact on PM_2.5 mass concentrations in living room, especially when frying, which could lead to peak value of 456.8 μg/m³ within 10 min from background level. Penetration led to the indoor PM_2.5 level approximately 2 h behind with outdoor PM_2.5 concentrations in general residences.

Human transport of thirdhand tobacco smoke: A prominent source of hazardous air pollutants into indoor nonsmoking environments

The contamination of indoor nonsmoking environments with thirdhand smoke (THS) is an important, poorly understood public health concern. Real-time THS off-gassing from smokers into a nonsmoking movie theater was observed with online and offline high-resolution mass spectrometry. Prominent emission events of THS tracers (e.g., 2,5-dimethylfuran, 2-methylfuran, and acetonitrile) and other tobacco-related volatile organic compounds (VOCs) coincided with the arrival of certain moviegoers and left residual contamination. These VOC emission events exposed occupants to the equivalent of 1 to 10 cigarettes of secondhand smoke, including multiple hazardous air pollutants (e.g., benzene and formaldehyde) at parts-per-billion concentrations. Nicotine and related intermediate-volatility nitrogen-containing compounds, which vaporized from clothes/bodies and recondensed onto aerosol, comprised 34% of observed functionalized organic aerosol abundance. Exposure to THS VOC emission events will be considerably enhanced in poorly ventilated or smaller spaces in contrast with a large, well-ventilated theater-amplifying concentrations and potential impacts on health and indoor chemistry.

Factors Influencing Residents’ Intention toward Green Retrofitting of Existing Residential Buildings

The green retrofitting of existing residential buildings is an important approach to realise the sustainable development of stock buildings. In addition to the new technologies and materials related to green retrofitting, the intention of residents toward the green retrofitting of existing residential buildings must be understood. However, the factors affecting such intentions are still unclear. Hence, this study refers to the extended theory of planed behaviour and constructs a theoretical model of the intention toward the green retrofitting of existing residential buildings. On the basis of the data from 507 questionnaires collected from eastern and western China, the theoretical model is tested via structural equation modelling (SEM). Multigroup SEM is used to analyse the differences in population characteristics and the intention of residents toward the green retrofitting of existing residential buildings in residential areas. Research results reveal the following: (1) the most important factors affecting residents’ intention toward green retrofitting are policy factors, followed by cognition of green retrofitting, behaviour, subjective norms, and perceived behavioural control; (2) policy factors not only directly affect residents’ intention toward green retrofitting but also indirectly affect their intention toward existing residential green retrofitting through perceived behavioural control; (3) residents’ cognition of green retrofitting exerts no significant direct impact on their intention toward green retrofitting, but it does indirectly affect their intention toward green retrofitting through behaviour and subjective norms; (4) behaviour, subjective norms, and perceived behavioural control have direct and significant influences on intention toward green retrofitting; (5) demographic characteristics (gender, age, monthly family income, education level, and occupation) and regional variables (east and west) present significant differences in different influence paths. The conclusion of the study provides a targeted path reference for the promotion of the green retrofitting of existing residential buildings.

Effects of energy retrofits on Indoor Air Quality in multifamily buildings

We assessed 45 multifamily buildings (240 apartments) from Finland and 20 (96 apartments) from Lithuania, out of which 37 buildings in Finland and 15 buildings in Lithuania underwent energy retrofits. Building characteristics, retrofit activities, and energy consumption data were collected, and Indoor Air Quality (IAQ) parameters, including carbon monoxide (CO), nitrogen dioxide (NO₂ ), formaldehyde (CH₂ O), selected volatile organic compounds (benzene, toluene, ethylbenzene, and xylenes (BTEX), radon, and microbial content in settled dust were measured before and after the retrofits. After the retrofits, heating energy consumption decreased by an average of 24% and 49% in Finnish and Lithuanian buildings, respectively. After the retrofits of Finnish buildings, there was a significant increase in BTEX concentrations (estimated mean increase of 2.5 µg/m³ ), whereas significant reductions were seen in fungal (0.6-log reduction in cells/m² /d) and bacterial (0.6-log reduction in gram-positive and 0.9-log reduction in gram-negative bacterial cells/m² /d) concentrations. In Lithuanian buildings, radon concentrations were significantly increased (estimated mean increase of 13.8 Bq/m³ ) after the retrofits. Mechanical ventilation was associated with significantly lower CH₂ O concentrations in Finnish buildings. The results and recommendations presented in this paper can inform building retrofit studies and other programs and policies aimed to improve indoor environment and health.

Building and indoor environmental quality assessment of Nigerian primary schools: A pilot study

A total of 15 classrooms went through on-site assessments/inspections, including measurements of temperature (T), and concentrations of carbon monoxide (CO) and carbon dioxide (CO₂ ). In addition, the level of surface biocontamination/cleaning effectiveness was assessed by measuring adenosine triphosphate (ATP) levels on students' desks. Based on the data, the quality of facilities in the buildings was low. Classroom occupancy exceeded ASHRAE 50 person/100 m² standard in all cases indicating overcrowding. However, concentrations of CO₂ remained below 1000 ppm in most classrooms. On the other hand, indoor T was above the recommended levels for thermal comfort in all classrooms. Maximum indoor CO was 6 ppm. Median ATP concentrations on the desk tops were moderately high in all schools. The use of open incinerators and power generator sets near classrooms, which was suspected to be the main source of CO, should be discouraged. Improved hygiene could be achieved by providing the students access to functioning bathroom facilities and cafeteria, and by effective cleaning of high contact surfaces such as desks. Although ventilation seems adequate based on CO₂ concentrations, thermal comfort was not attained especially in the afternoon during extreme sunlight. Therefore, installing passive and/or mechanical cooling systems should be considered in this regard.

Indoor and outdoor concentrations of BTEX and formaldehyde in Tehran, Iran: effects of building characteristics and health risk assessment

BTEX (benzene, toluene, ethylbenzene, xylene) and formaldehyde are toxic compounds that can induce adverse health effect in humans. This study measured in-home and ambient concentrations of BTEX and formaldehyde across Tehran, Iran. These pollutants were sampled from the indoor and adjacent outdoor air of 45 houses (9 in each city zone) during the winter of 2015. Sampling was repeated three times for each house. The analyses were performed according to NIOSH procedures. The effect of flooring material, wall covering, ventilation system, heating system, height above ground, presence of attached garages, and distance from highways was evaluated. In addition, carcinogenic and non-carcinogenic risks of these compounds were assessed. The average indoor concentrations of benzene, toluene, ethylbenzene, xylene, and formaldehyde were 53.2, 21.5, 14.4, 21.1, and 17.9 μg/m³, respectively. The average outdoor concentrations of benzene, toluene, ethylbenzene, xylene, and formaldehyde were 43.5, 26.2, 10.0, 19.1, and 6.9 μg/m³, respectively. Separate regression models showed that wall coating, ventilation system, heating system, flat level, and distance from highways explained 29, 60, 16, 60, and 59% of the BTEX concentrations, respectively. Houses with oil painted walls and parquet flooring had higher concentrations of BTEX and formaldehyde, respectively. The health risk assessment found that the carcinogenic risks of benzene and formaldehyde exceeded 1 × 10^-4 and represent a definite risk. New buildings can be designed based on the results of this study to use better materials and optimum building designs to reduce exposure to these toxic air pollutants.

Indoor thermal environment, air exchange rates, and carbon dioxide concentrations before and after energy retro fits in Finnish and Lithuanian multi-family buildings

Impacts of energy retrofits on indoor thermal environment, i.e. temperature (T) and relative humidity (RH), as well as ventilation rates and carbon dioxide (CO₂) concentrations, were assessed in 46 Finnish and 20 Lithuanian multi-family buildings, including 39 retrofitted case buildings in Finland and 15 in Lithuania (the remaining buildings were control buildings with no retrofits). In the Finnish buildings, high indoor T along with low RH levels was commonly observed both before and after the retrofits. Ventilation rates (l/s per person) were higher after the retrofits in buildings with mechanical exhaust ventilation than the corresponding values before the retrofits. Measured CO₂ levels were low in vast majority of buildings. In Lithuania, average indoor T levels were low before the retrofits and there was a significant increase in the average T after the retrofits. In addition, average ventilation rate was lower and CO₂ levels were higher after the retrofits in the case buildings (N=15), both in apartments with natural and mixed ventilation. Based on the results, assessment of thermal conditions and ventilation rates after energy retrofits is crucial for optimal indoor environmental quality and energy use.

Investigation of Indoor Air Quality in Houses of Macedonia

People who live in buildings are exposed to harmful effects of indoor air pollution for many years. Therefore, our research is aimed to investigate the indoor air quality in family houses. The measurements of indoor air temperature, relative humidity, total volatile organic compounds (TVOC), particulate matters (PM) and sound pressure level were carried out in 25 houses in several cities of the Republic of Macedonia. Mean values of indoor air temperature and relative humidity ranged from 18.9 °C to 25.6 °C and from 34.1% to 68.0%, respectively. With regard to TVOC, it can be stated that excessive occurrence was recorded. Mean values ranged from 50 μg/m³ to 2610 μg/m³. Recommended value (200 μg/m³) for human exposure to TVOC was exceeded in 32% of houses. Mean concentrations of PM2.5 (particular matter with diameter less than 2.5 μm) and PM10 (diameter less than 10 μm) are determined to be from 16.80 μg/m³ to 30.70 μg/m³ and from 38.30 μg/m³ to 74.60 μg/m³ individually. Mean values of sound pressure level ranged from 29.8 dB(A) to 50.6 dB(A). Dependence between characteristics of buildings (Year of construction, Year of renovation, Smoke and Heating system) and data from measurements (Temperature, Relative humidity, TVOC, PM2.5 and PM10) were analyzed using R software. Van der Waerden test shows dependence of Smoke on TVOC and PM2.5. Permutational multivariate analysis of variance shows the effect of interaction of Renovation and Smoke.

Re-evaluation of the WHO (2010) formaldehyde indoor air quality guideline for cancer risk assessment

In 2010, the World Health Organization (WHO) established an indoor air quality guideline for short- and long-term exposures to formaldehyde (FA) of 0.1 mg/m3 (0.08 ppm) for all 30-min periods at lifelong exposure. This guideline was supported by studies from 2010 to 2013. Since 2013, new key studies have been published and key cancer cohorts have been updated, which we have evaluated and compared with the WHO guideline. FA is genotoxic, causing DNA adduct formation, and has a clastogenic effect; exposure-response relationships were nonlinear. Relevant genetic polymorphisms were not identified. Normal indoor air FA concentrations do not pass beyond the respiratory epithelium, and therefore FA's direct effects are limited to portal-of-entry effects. However, systemic effects have been observed in rats and mice, which may be due to secondary effects as airway inflammation and (sensory) irritation of eyes and the upper airways, which inter alia decreases respiratory ventilation. Both secondary effects are prevented at the guideline level. Nasopharyngeal cancer and leukaemia were observed inconsistently among studies; new updates of the US National Cancer Institute (NCI) cohort confirmed that the relative risk was not increased with mean FA exposures below 1 ppm and peak exposures below 4 ppm. Hodgkin's lymphoma, not observed in the other studies reviewed and not considered FA dependent, was increased in the NCI cohort at a mean concentration ≥0.6 mg/m3 and at peak exposures ≥2.5 mg/m3; both levels are above the WHO guideline. Overall, the credibility of the WHO guideline has not been challenged by new studies.

Household indoor air quality and its associations with childhood asthma in Shanghai, China: On-site inspected methods and preliminary results

Few studies were conducted for associations of home environment with childhood health by on-site inspection in China. During 2013-2014, we conducted a case-control study with home inspection among 454 children (186 asthma children and 268 non-asthma children) in Shanghai, China. In this paper, we detailedly described the inspected methods and analyzed the preliminarily collected data. Except in winter, most residences meet the national standard for indoor temperature and relative humidity. Most living rooms had ≤1000ppm CO₂, whereas over half of the child's bedrooms had slightly >1000ppm CO₂ during night. Most residences had notably lower than 2500cfu/m³ airborne culturable fungi and ≤100μg/m³ formaldehyde. More than 70% of the child's bedrooms had ≤75μg/m³ PM_2.5 and ≤150μg/m³ PM₁₀. Indoor and outdoor concentrations of particulate matters had strong linear correlations (r=0.891-0.922; p-value <0.001). Most differences between cases and controls were not significant with respect to CO₂, culturable fungi, formaldehyde, and particulate matters. Before and after adjusted for potential confounders, indoor averaged concentration of CO₂ and particulate matters generally had negative associations with childhood history of doctor-diagnosed asthma in spring, summer, and autumn. Only in winter, indoor CO₂ concentration was significantly associated with the increased odds of childhood asthma. Our results indicated that air quality among most residences in Shanghai could meet the national standard for indoor air quality in warm seasons; but household air quality and ventilation status in winter should be greatly improved. We suspected that those "unexpected" negative associations could exist due to changes in lifestyle behaviors regarding indoor air quality after the child being diagnosed asthma by a doctor.