TVOC Concentrations Research Articles

Spatio-temporal variations of indoor air quality in a university library

ABSTRACT The present study aims to assess the air quality status in the central library of Indian Institute of Technology Roorkee, India. Pollutants concentrations (i.e. PM10, PM2.5, PM1 and TVOC) and comfort parameters i.e. CO2, temperature and relative humidity were monitored across all floors of the library. Air quality was found to vary significantly (P < 0.05) among the different floors of the library. The average concentration of PM10, PM2.5 and PM1 was found to be highest at the first floor. On the other hand, the highest concentration of TVOC (51.7 ± 30 ppb) and CO2 (838.4 ± 99 ppm) was observed at the ground floor. Pollutant concentration was higher in the morning hours. The indoor pollutants were found positively correlated with each other except relative humidity. Indoor to outdoor ratio for PM1, TVOC and CO2 was found to be greater than 1, which indicate a substantial contribution from indoor sources. Exceedance of WHO guidelines was observed for the daily average PM2.5 concentration. Abbreviation: IAQ: indoor air quality; ASHRAE: American Society of Heating, Refrigerating, and Air-Conditioning Engineers; WHO: World Health Organization; PM: particulate matter; VOC: volatile organic carbon; CO2: carbon dioxide; TVOC: Total volatile organic compound; RH: relative humidity; HVAC: heating ventilation and air-conditioning; PID: Photo Ionization Detector; PTFE: Polytetrafluoroethylene; NDIR: Non-dispersive infra-red.

Material VOC Emissions and Indoor Air Quality Simulation

The contribution reports on a simulation study of indoor air quality in relation to different ventilation rates specified for 3 categories of the indoor environment according to EN 15 251. Indoor air quality and energy management are often at the opposite ends of the building management spectrum. The buildings are polluted by occupants of the building themselves. The indoor air quality can be expressed at the required level of ventilation or Carbon Dioxide (CO2) concentration. Actually, the indoor air quality is influenced by emission from building surface materials and furnishing, occupants and their activities. VOCs play an important role in the indoor air quality evaluation process. VOC emissions adversely affect both occupant comfort and health. Most of the health hazards associated with VOC emissions occur during the first few weeks of building use. The Indoor Air Quality Emission Simulation Tool developed by National Research Council is used for simulating the VOCs emission impact of selected materials based on the amount of materials used and the ventilation rates in a model room, in this case study. IA-Quest predicts the emission of VOCs from building surface materials and furnishings, helping to select low-emission materials and effective ventilation strategies. The results showed the benefit of removing the increased amount of TVOC generated in time of the unoccupied period. The differences in TVOC concentrations were not obvious between two higher ventilation conditions (2.00 and 1.40 l/s.m2). More significant difference was estimated between categories A, B and category C (0.80 l/s.m2).

The effects of temperature and humidity on the VOC emission rate from dry building materials

With the development of the economy and society, a wide variety of new building decoration and materials are widely used indoors. The concentration of pollutants such as formaldehyde, volatile organic compounds, benzene and ammonia in indoor air witnessed increase, causing increasingly serious indoor air pollution problems. Indoor building decoration materials are one of the main sources of indoor VOCs. In this paper, the emission law of VOCs in dry building materials with environmental conditions is studied. The environmental test cabin is used to test the formaldehyde and TVOC concentration released. The single factor variable method is used to study how different environmental conditions (temperature and relative humidity) affect the rate of formaldehyde and TVOC released from dry building materials. According to the results, increase of ambient temperature and relative humidity will promote the release of TVOC, which will affect its peak concentration and stable concentration, and the effect on formaldehyde release is more significant. This study clarified the release law of VOCs in artificial boards under different environmental conditions, which is of great significance for reducing indoor air pollutant levels and improving indoor air quality.

Indoor Air Quality and Its Effects on Health among Urban Residents in Jakarta and Surabaya, Indonesia

In rapidly growing countries, such as in Indonesia, dramatic increase in new urban houses constructed of modern building materials without sufficient material standards or minimum ventilation rates may cause health problems related with indoor air quality (IAQ). This study investigates the current IAQ and health condition in Kampongs and high-rise apartments in Jakarta and Surabaya, Indonesia. Concentrations of formaldehyde and TVOC were measured, whereas a questionnaire was conducted to collect the data of building attributes, cleaning behaviour, ventilation duration, personal information and health. 707 respondents were interviewed, and 163 rooms were measured from September 2017 to October 2018 in Surabaya and Jakarta. The results showed that overall, the newly constructed apartments recorded higher formaldehyde compared to Kampongs—more than 60% in apartments exceeded the WHO standard of 0.08 ppm. On the other hand, there was little difference in TVOC between Kampongs and apartments and the maximum values reached from 8, 000 up to 21, 800 µg/m3. In general, the multiple chemical sensitivity (MCS) of occupants in apartments was twice as high as that in Kampongs. Further, the occupants with higher IAQ measurement results corresponded to the higher MCS risk. The primary results showed a high possibility of IAQ-related health problems in both Kampongs and newly constructed apartments in Indonesia although the main causes were probably different between them.

Comparative Study of the Impact of Biomass and Clean Fuels Burning as Cooking Energy on Rural Indoor Air Quality in Heilongjiang, China

In rural areas of the northeast China, the majority of residents use traditional Chinese Kang-stoves for heating and cooking by burning biomass fuels. However, this method is associated with serious indoor air pollution problems. The purpose of this study is to evaluate indoor air quality impacts from biomass combustion and indoor air quality improvements derived from using clean fuel. A comparative study was conducted in three rural households of Heilongjiang to determine indoor air pollution extent during burning biomass (rice straw, cornstalk and corncob) and liquefied petroleum gas (LPG) fuels for cooking. The results indicated that the concentration of CO from the combustion of four kinds of fuels was almost below the guidelines prescribed in Chinese In-door Air Quality Standard. On the contrary, PM2.5 concentrations exceeded the limiting value regardless of which fuel was used, and the lowest PM2.5 concentration values, which were obtained during burning LPG, were about 2.4-7.5 times of 24-h mean PM2.5 concentration limit. The mean values of formaldehyde concentrations during using four types of cooking energy were totally higher than the standard limit, and the lowest formaldehyde concentrations were detected when corncob was used as cooking energy. Compared with LPG fuel, biomass fuels combustion in traditional Kang-stove with chimney increased the concentrations of TVOC and BTEX. To conclude, the pollutants generated from using LPG are relatively less harmful. Among the three biomass fuels, the minimal pollution derives from the combustion of corncob.

Indoor Chemical Air Contaminants in Main Prayer Hall during Jumaat Prayer in Mosques with Different Mechanical Ventilation

Muslims generally pray five times a day. Every Friday, adult male Muslims congregate to perform Jumaat prayer, causing increased number of worshippers in mosques and vehicle movements. Consequently, indoor chemical air contaminants are produced inside and outside mosques. This study evaluated the compliance of indoor chemical air contaminants (CO, O3, TVOC, CH2O, and PM10) during Jumaat and Asar prayers in two mosques having different mechanical ventilations (i.e., air conditioning and non-air conditioned system) with the guideline limit recommended by Malaysia’s Industrial Code of Practice. Chemical air contaminants were monitored from 1200HH to 1700H in the air-conditioned mosque and from 1200H to 1730H in the non-air conditioned system mosque, which were the times for Jumaat and Asar prayers. The monitoring was conducted from November 2016 to March 2017, during the Northeast monsoon. Results showed that the mean concentrations of the four chemical air contaminants in both mosques did not exceed the acceptable guideline limit. The mean CO, TVOC, CH2O, and PM10 concentrations in the air-conditioned mosque were 0.29 ppm, 354.09 ppb, 31.28 ppb, and 13.45 μg/m3; those in the non-air conditioned system mosque were 2.36 ppm, 344.32 ppb, 19.78 ppb, and 49.91 μg/m3, respectively. However, the air-conditioned mosque’s maximum PM10 concentration of 164.48 μg/m3 exceeded the acceptable guideline limit of 150 μg/m3. Moreover, both mosques’ mean O3 concentrations of 140 and 80 ppb exceeded the limit of 50 ppb, respectively. These results suggested that the concentrations of three chemical air contaminants (TVOC, O3, and CH2O) in the air-conditioned mosque were higher than those in the non-air conditioned system mosque possibly because of the inadequate ventilation system inside the air-conditioned building. Therefore, air-conditioned mosques should have a good ventilation system to provide suitable temperature and humidity for the Jemaah, as well as sufficient amounts of air to remove indoor chemical air contaminants.

A 21-day sub-acute, whole-body inhalation exposure to printer-emitted engineered nanoparticles in rats: Exploring pulmonary and systemic effects

Engineered nanomaterials (ENMs) used in toners to improve their performance are released in the air during laser printer use. ENMs play an important catalytic role in the breakdown of the toner polymer and subsequent rearrangement of organic compounds as well as in the formation of reactive oxygen species (ROS). Cellular, animal, and human occupational exposure studies have shown that such printer-emitted particles (PEPs) induce inflammation, systemic oxidative stress, and genotoxicity, as well as, increase frequency of coughing, wheezing, and upper airway symptoms, raising concerns about their long-term impact on human health. No safety thresholds or regulatory guidelines currently exist for PEPs. In this study, Sprague-Dawley rats were exposed (by whole-body inhalation) to PEPs 5 h/day for up to 21 days using an exposure platform previously developed by the authors. The control group comprised of an equal number of rats exposed to high-efficiency particulate air (HEPA) filtered air. The PEPs had a mean particle diameter of approximately 45 nm, and a total particle number concentration ranging from 4 to 21 × 105 #/cm3. The maximum total volatile organic compound (tVOCs) concentration was 363.2 ± 162 ppb. The Multiple-Path Particle Dosimetry Model (MPPD) estimated the deposited fraction of PEPs to be around 7, 6 and 21% in the head, tracheobronchial (TB) and alveolar regions, respectively. Analysis of biochemical markers in the nasal and bronchoalveolar lavage fluids (NLF, BALF) of PEPs-exposed animals showed only mild oxidative stress and inflammation. No damage was detected in the histological and chemiluminescence analysis of lung and heart tissues of PEPs-exposed animals. Pro- and anti-inflammatory cytokines and chemokines, such as Interleukin (IL) 1β, IL-12, IL-18, MIP-1α, MIP-2, GRO/KC, and Fractalkine were found to be up-/down-regulated in NLF and BALF of the PEPs-exposed animals. Also, serum biomarkers of oxidative stress and inflammation, such as 8-isoprostane, 4-hydroxynonemal, and Leukotriene B4 were elevated in PEPs-exposed animals. In conclusion, following exposure to PEPs, there was modest lung injury and inflammation in the respiratory tract. Specifically, changes in expression of certain cytokines and chemokines, along with serum levels of 8-isoprostane, were the most significant adverse effects reported following exposure to PEPs.

On-site assessments on variations of PM2.5, PM10, CO2 and TVOC concentrations in naturally ventilated underground parking garages with traffic volume

There have been an increasing number of automobile vehicles in cities, so that newly developed residential areas are mostly designed with underground parking garages (UPGs). For naturally ventilated UPGs, the ventilation performance may be insufficient to discharge totally vehicle-induced pollutants out of the enclosed underground spaces, which consequently results in threats to residents' health. This study, therefore, aims at examining the patterns of pollutant concentrations in naturally ventilation UPGs as well as their sensitivities to traffic volume. In particular, the naturally ventilated UPGs' weekday particulate matters (PM2.5 and PM10), CO2 and TVOC concentration as well as their relationships between traffic volume were quantitively evaluated based on field measurements in eight residential areas in Baoding, China. Results indicated that daily average PM2.5, PM10, CO2 and TVOC concentrations in studied UPGs were 105.81 μg/m3, 464.17 μg/m3, 571 ppm and 24 ppb, respectively. The PM2.5 concentrations in UPGs were slightly higher than that in ambient environments, while the PM10 concentrations in UPGs were significantly higher. Furthermore, both PM10 and TVOC concentrations in UPGs were in significant relationships with traffic volume at the p < 0.01 level, while the concentration of UPG PM2.5 generally exhibited a significant correlation (p < 0.01) with that of the ambient. Nevertheless, a combination of traffic volume, the ambient and accumulative effect was much better to explain the hourly PM10 concentration in UPGs. These findings will be conducive to instruct engineers with fundamental knowledge of UPG ventilation design.

Particulate matters and gaseous pollutants in indoor environment and Association of ultra-fine particulate matters (PM1) with lung function.

Real-time particulate matters (PM1, PM2.5, PM4, PM7, PM10, and TSP) with AEROCET 531S (USA), gaseous pollutants (NO2 and TVOC) with Aeroquel 500 gas sampler (NZ) were measured from the indoor air of houses at four residential locations in Dhaka, Bangladesh. PM10 samples were collected on quartz filters with a dual channel dust sampler (IPM-FDS 2510, India) for selected trace metal determination from five houses of Dhaka. Respiratory function of the occupants was assessed by using a peak expiratory flow meter (Rossmax PF 120). Mean PM1, PM2.5, and PM10 concentrations were 46.1 ± 13.4, 76.0 ± 16.2, and 203.9 ± 44.8μgm-3, respectively. Higher enrichment factors of Pb, Zn, and Ni were found for traffic, industrial, and constructional activities. The correlation between indoor and outdoor PM2.5 (R2 = 0.42) and ratios (I/O < 1) suggesting indoor air was effected by outdoor air. The concentration of NO2 (0.076 ± 0.007ppm) and TVOC (90.0 ± 46.0ppm) was found above than other studies. The average total hazard ratio (THR) in Dhaka was 9.06 and has the highest exposure to air pollutants (PM2.5, PM10, NO2) in Khilkhet (THR 10.1) residents. A negative association between ultra-fine particles (PM1) and peak flow rate measurements of the residents living in these houses indicates that inhalations of ultra-fine particles has great influence on the reduced lung efficiency.

Interior Materials Combination and Perceived Indoor Air Quality

The materials used in the buildings, either as surface structural materials or as furnishings, are mostly the sources of indoor air pollution. Interior surfaces are generally accepted as the main source of indoor TVOCs emissions. The poor indoor microclimate quality can cause the sick building syndrome, as well as negatively affects the people activities and wellbeing. In recent years the needs of indoor air quality and building performance improvement have been increasing. The indoor materials impact on perceived indoor air quality for various surface interior materials and its combination was studied within this paper. Traditional and progressive materials comparison reveals new fact regarding the TVOCs concentration. The task of the study was to investigate the possibility using individual material surfaces sorption ability. The chemical analysis and sensory assessments identifies health adverse of indoor air pollutants (TVOCs). Also we can use knowledge about the targeted use of sorption effect already in the building design phase. The results demonstrate the various sorption abilities of various indoor materials as well as various sorption ability of the same indoor material in various combinations.

Field study of indoor environment quality in an open atrium with ETFE membrane in a healthcare facility

The hospital street is widely utilized in the modern health care facilities as a main traffic streamline to connecting all of the outpatient rooms and treatment departments for easy access. This study investigate the indoor environment quality of a typical hospital street, i.e., a high space atrium with ETFE membrane structure in the top. The investigation combines the on-site measurement and subjective survey. The results indicates that the indoor air temperature in the atrium reaches up to 32.6oC in a summer day causing thermal discomfort according to ASHRAE 55. The CO2, PM2.5, TVOC concentration in the hospital street comply with the Chinese standard for hospitals. The illumination in the corridors around the atrium is below the threshold of Chinese standard, i.e., 100 lux. Due to the vibration of the light ETFE membrane structure, the noise level in rainy days is as high as 79.5 dB which causes acoustic discomfort of occupants. This study is beneficial for the design of the hospital street design with the ETFE membrane structure.

Feasibility of a Passive Ventilation System with a Thermal Damper - Simulations and measurement results of an experimental house in a mild region of Japan -

In order to retain good indoor air quality through the year in detached houses with passive ventilation systems, the authors investigated a mechanical control air-supply method. Firstly, indoor environments in houses with passive ventilation systems with thermal dampers, were examined using a simulation program (Fresh). Secondly, a passive ventilation system with a thermal damper, an under-floorheating system with a heat pump and were installed in an airtight house at Maebashi in Japan and measurements on its ventilation characteristics and indoor air quality were made. The simulation results showed that if the thermal damper is well tuned, this mechanically controlled air-supply opening keeps ventilation rates adequate through the year especially in airtight houses. The measurement results showed that the ventilation rates were kept above the required level through the year and the TVOC concentration decreases from 3000 to 200 μg/m3 in 5 months after the construction.

Pollution Characteristics and Health Risk Assessment of VOCs in Areas Surrounding a Petrochemical Park in Shanghai

To investigate the pollution characteristics of volatile organic compounds (VOCs) in the vicinity of a petrochemical park, the composition and concentration of VOCs was successively monitored by application of a gas chromatography-flame ionization detector in the residential area surrounding a petrochemical park in Shanghai in October 2017. Moreover, the maximum incremental reactive method was employed to estimate the O3-formation potential contributed by VOCs, and health risks were assessed. Results showed that during the observation period, TVOCs concentrations ranged from 16.4 μg·m-3 to 1947.8 μg·m-3 with an average concentration of 40.7 μg·m-3, whereas the average proportions of alkanes, alkene/alkynes, and aromatic hydrocarbons were 66.2%, 25.9%, and 7.9%, respectively. The diurnal variation of total VOCs concentration showed a monomodal change, with a peak concentration of 127.9 μg·m-3 at 07:00, whereas the TVOCs had an average ozone formation potential (OFP) of 249.7 μg·m-3. Analysis of OFP indicated that trans-2-butene and ethylene were the most important species in ozone production with accountabilities for total OFP of 153.4 μg·m-3. Propylene, trans-2-butene, and ethylene were the key active species. Furthermore, health risk assessments revealed that no significant health risks had been caused by hexane, benzene, toluene, ethylbenzene, o-xylene, and m-xylene.

Indoor air quality analysis of residential buildings in northeast China based on field measurements and longtime monitoring

Outdoor air contamination was frequently observed and focused in northeast China in winter when severe cold days are common and understanding dynamic characteristics of indoor air quality in this area is essential for occupants' ventilation strategies. Herein, using spectrophotometric method, GC-MS (Gas Chromatography-Mass Spectrometer) method, TSI DustTrak particle tester and Telaire 7001 CO2 tester, we investigated the concentration change of formaldehyde (HCHO), volatile organic compounds (VOCs), PM2.5 and CO2 of 21 houses for 4 seasons under 2 conditions (airtight and natural ventilation). Moreover, 6 houses were selected to install convenient sensors for longtime monitoring. Outdoor temperature, concentration of PM2.5, residents' opening window behavior, indoor infiltration rate, temperature, relative humidity and the furniture surface area were also recorded for comparison and correlation analysis. According to the detected results, worst indoor conditions were revealed that average concentrations of HCHO (autumn), TVOC (summer), PM2.5 (winter) and CO2 (winter) were 0.094 mg/m3, 0.924 mg/m3, 0.073 mg/m3, and 883 ppm, respectively. Indoor concentration of PM2.5, TVOC and CO2 exceeded the standard limit and they changed with seasonal characteristics. The observed 4 factors have different effects on indoor air quality. Based on this research, it is recommended that outdoor condition be considered while opening and closing window in winter and ventilation be strengthened in summer.

Air quality in indoor go-kart facilities in Germany

Indoor go-kart driving and viewing is enjoyed by people of all ages. However, it may pose health hazards, especially for children, pregnant women, cardiovascular patients, and elderly individuals. Depending on the race length, for example, high concentrations of various contaminants may result in severe health problems. Therefore, this project investigated the Indoor Air Quality of eight indoor go-kart facilities. In general, karts that used regular fuel produced the highest concentrations of CO, benzene, TVOC, and BaP, with maximum levels up to 150mg/m3 , 170μg/m3 , 2690μg/m3 , and 8.7ng/m3 , respectively. As expected, the maximum CO concentrations at go-kart facilities that used liquid gas and electric karts (20 and <6mg/m3 , respectively) were significantly lower than those at other facilities. The highest 95th percentile values for NO (2680μg/m3 ) and NO2 (280μg/m3 ) were measured for karts with liquid gas. The alkane, alkene, and cycloalkane groups, as well as benzene and the alkyl benzenes, were the predominant components of the measured TVOCs. Overall, owners of indoor go-kart tracks should ensure that the ventilation with regard to combustion products is optimally adapted in any case to reduce the levels of critical air pollutants.

Secondary VOCs emission from used fibrous filters in portable air cleaners and ventilation systems

Previous research suggests that filters used in indoor portable air cleaners or ventilation systems may be an indoor pollutant source at some point of using when it is loaded with certain amount of particle or gas phase pollutants. To evaluate its influence on indoor air quality, both qualitative and quantitative analysis of the potential source is needed. This study aims at investigating secondary volatile organic compounds (VOCs) emission from used fibrous particle filters. Used filters from portable air cleaners used in real life were collected. HEPA fibrous filters challenged by outdoor dust were investigated to simulate its application in residential fresh air system. Filter samples were stored in room temperature and three different relative humidity settings before testing. The emitted VOCs species and emission rate were measured using a single-pass test system, with TENAX sorbent tubes sampling and GC-MS analysis method. The emitted TVOC concentration profile with time presented a single-peak curve. The data indicated that the TVOC emission rate of used filters were influenced by both dust loading amount and environmental VOCs level. With the same dust loading, TVOC emission rate of filters challenged by indoor dust was 2–10 times higher than filters challenged by outdoor dust. When the environmental VOCs concentration was stable, there is a liner relationship between TVOC emission rate and dust loading. The TVOC emission rate was in the range of 0.63mg/m2-3.46 mg/m2 for filters used in portable air cleaners. After exposure in humid environment, the total emitted TVOC generally decreased with the major decrease of Alkanes, Aromatics, Esters and Alcohols categories, while the emission rate of Aldehydes, Ketones and Olefins increased. Possible reason was discussed.

Characteristics and Source Apportionment of Volatile Organic Compounds in the Rainy Season of Guangzhou City

Atmospheric volatile organic compounds (VOCs) were measured in an urban area of Guangzhou on July 2016 using an on-line gas chromatography mass spectrometry/fire ion detector. Seventy-three VOCs were detected with an average concentration of (118.83±79.40) μg·m-3, a maximum concentration of 492.42 μg·m-3, and a minimum concentration of 10.54 μg·m-3 during the period. The peak value of the TVOC concentration appeared at about 07:00 in the morning, indicating that motor vehicle pollution had a significant contribution at the site. The minimum value appeared at about 14:00 in the afternoon, related to photochemical losses. High concentrations were also observed from 21:00 to 24:00, which was probably related to pollution emissions and boundary layer compression. Source analysis by PMF showed that the site was mainly affected by five VOC sources: vehicle exhaust, solvent use, fuel loss at fuel stations, plant emissions, and cooking exhaust, the contributions of which were 29.79%, 26.61%, 24.86%, 9.91%, and 8.84%, respectively. Vehicle exhaust was the largest source of VOCs during the daytime, while the contribution of plant emissions increased significantly at noon. The contribution of solvent uses and fuel loss at fuel stations rose during the night and became the main source of VOCs until early morning.

Indoor environmental quality and Sick Building Syndrome in office buildings

In the last decades public health problems caused by indoor air pollution, such as Sick Building Syndrome (SBS), have been drawing strong public concerns. This study aims at investigating the indoor environment quality (IEQ) and people’s complaints in office buildings in Egypt. Indoor environment parameters including air temperature, relative humidity, air speed, TVOC, formaldehyde, Benzene, and Toluene were measured at two office buildings, which located in Giza, and Port Said. The study was done during March 2017-May 2017. Occupants’ perception on indoor environmental quality (IEQ), and SBS symptoms were surveyed by questionnaire.High TVOCs concentration, should be of health effect concern. It was indicated that indoor air quality (IAQ) may lead to SBS symptoms in office building in Egypt.

Indoor air quality investigation of a university library based on field measurement and questionnaire survey

This article presents field studies and questionnaire survey on the indoor air quality (IAQ) in library rooms in University of Science and Technology Beijing in April 2016, with no heating, to find out actual situation of IAQ in university library. Nine rooms equipped without centralized air-conditioning system were carefully selected for the test. Results showed that each room had diverse indoor thermal environment and concentrations of CO2, PM2.5, formaldehyde and TVOC. The concentration of CO2 ranged from 575 to 2400 ppm, PM2.5 concentration was 40–70% of the outdoor, the highest concentration of formaldehyde and TVOC was ~0.042 and 0.285 mg m−3, respectively with half of the upper limit. The concentrations of CO2 and PM2.5 in the holding-reading rooms were higher than that in the rooms only holding books. The situation of formaldehyde and TVOC concentrations was just opposite. The correlations between satisfaction of IAQ and the concentrations of indoor air pollutants were not as a constant, but changing with different rooms. Based on gray system theory, satisfactions were affected seriously by CO2 and PM2.5. One improving plan with the theme of ‘ventilating rapidly along with purifying’ was determined based on a general mass balance equation. In theory, IAQ can be improved <5 min for the most unfavorable condition. Through analysis, requirements of fresh air and functionality of the space usages should be considered in the ventilation or central air-conditioning system design.

Indoor environmental conditions in urban and rural homes with older people during heating season: A case in cold region, China

China's aging population is growing rapidly. To date, there have been few literatures concerning indoor environment of private houses with older people. This study fully investigated indoor environment in 10 houses (5 urban and 5 rural houses) with older people during heating season in Beijing, China. Each house was assessed for temperature, relative humidity, CO2, PM2.5, CO, NOx, formaldehydes, acetaldehyde, VOCs, SVOCs and fungi. Results indicated older people in urban houses experienced a steadier and warmer thermal environment than those in rural houses, due to the difference of heating devices between urban and rural houses. Indoor CO2 levels mainly increased up to 1000 ppm in the bedroom during sleeping time. For rural houses, indoor fuel combustion contributed to an extremely high PM2.5 and CO level. Formaldehyde, acetaldehyde, toluene, ethylbenzene and xylenes levels in most houses were lower than the limit values. However, the integrated influence of these compounds was unnegligible. TVOC concentrations in four measured houses exceeded the reference value of 600 µg/m3. The most frequent fungi was Cladosporium spp. (90%), followed by Penicillium spp. (70%) and Aspergillus spp. (60%). The fungal levels in rural houses were higher than urban houses. These results will be beneficial to improve housing environmental quality for older people in China.