Indoor Volatile Organic Compounds Levels Research Articles

Evaluation of the seasonal variation of VOC surface emissions and indoor air concentrations in a public building with bio-based insulation

The use of bio-based insulation materials is widely spreading in buildings. Due to their organic load, they can be an important source of Volatile Organic Compounds (VOCs). This study is among the first that evaluates the spatial and seasonal in-field VOC surface emissions from bio-based and conventional building structures as a whole, in a French public building insulated with wood wool. In addition to surface emissions, measurements of VOC concentrations in indoor air were taken. Results showed that a spatial difference (up to 5 times) in VOC emissions was observed due to the inhomogeneity of the surface. Moreover, the cardinal orientation of building structures with the same constitution induced a difference (up to a factor 30) in emission rates due to the exposure to different hygrothermal conditions. The variation in temperature and relative humidity between seasons led to higher summer VOC emissions and indoor air concentrations. In addition, indoor VOC concentrations were shown to be higher at night compared to daytime due to the decreased ventilation rate. Furthermore, an interesting approach was developed in this study to have a primary overview of the impact of surface emissions on indoor VOC levels. Results confirmed that the three bio-based walls have no significant specific VOC emissions at high rates compared to the floor and the ceiling. Bio-based insulations showed no impact on microbial indoor air concentrations during the two seasons. Moreover, no detected VOCs could be attributed to microbial development as they were also emitted from building materials.

Performance evaluation of activated carbon sorbents for indoor air purification during normal and wildfire events.

Volatile organic compounds (VOCs) are a significant class of indoor air pollutants and are known for their adverse effects on health. A common strategy to reduce indoor VOC levels is to use sorbents, including activated carbons (ACs). The amount of activated carbon is critical to achieving a reasonable AC filter lifetime in an air purification device. The study aims to estimate the amount of carbon needed in a typical indoor environment and in a heavy use setting such as during cooking, agriculture field fires, or wildfires. The problem is complex as various types of ACs are used, and the type and concentration of VOCs in the indoor environment also vary in different settings. Therefore, literature data on thermophysical parameters for 45AC-VOC pairs was used to estimate the required amount of AC under a given set of conditions. The study uses modeling distributions of the footprint of suitable carbon filters for the removal of common VOCs encountered indoors for a period of 30 days. It was found that while 50% of AC-VOC pairs surveyed will require about 190-370g at low indoor VOCs levels of 0.1-1μmol/m3(considered a good clean indoor environment), up to 1.1kg of ACs are needed for a carbon filter to survive 30 days in a typical indoor environment (VOCs levels of 10μmol/m3). On the other hand, 3-15kg or more AC will be needed in a filter to survive 30 days during adverse events such as wildfires. The objective of the present study is to aid consumers and businesses in making an informed decision on the type of AC-based indoor air filters that meet their needs. Using this data, an open-access online calculator is being developed to predict the amount of carbon needed in a filter/device at any specific indoor air condition.

Indoor exposure levels and risk assessment of volatile organic compounds in residences, schools, and offices in China from 2000 to 2021: A systematic review.

The last two decades have witnessed rapid urbanization and economic growth accompanied by severe indoor air pollution of volatile organic compounds (VOCs) in China. However, indoor VOC pollution across China has not been well characterized and documented. This study is a systematic review of field measurements of eight target VOCs (benzene, toluene, xylenes, acetaldehyde, p-dichlorobenzene, butadiene, trichloroethylene, and tetrachloroethylene) in residences, offices, and schools in China from 2000 to 2021. The results show that indoor pollution of benzene, toluene, and xylenes has been more serious in China than in other countries. Spatiotemporal distribution shows lower indoor VOC levels in east and south-east regions and a declining trend from 2000 to 2021. Moving into a dwelling more than 1 year after decoration and improving ventilation could significantly reduce exposure to indoor VOCs. Reducing benzene exposure is urgently needed because it is associated with greater health risks (4.5 × 10-4 for lifetime cancer risk and 8.3 for hazard quotient) than any other VOCs. The present study enriches the database of indoor VOC levels and provides scientific evidence for improving national indoor air quality standards as well as estimating the attributable disease burden caused by VOCs in China.

Modeling dynamic behavior of volatile organic compounds in a zero energy building

With increasing building airtightness, the design of an adequate ventilation system gains importance. The first generation of ventilation systems, based on continuous supply of the nominal airflow rate, are now being replaced by demand controlled ventilation (DCV). These systems, often H2O and/or CO2 controlled, typically do not take into account the emissions of volatile organic compounds (VOCs) to the indoor environment. A small, airtight, zero energy building that has been designed as the Belgian submission to the international Solar Decathlon competition (2011) was rebuilt afterwards in Ostend, Belgium. This building will be used as test facility for the development and validation of a holistic VOC source model. In this study, results are obtained from thermal, airflow and contaminant simulation models of the test facility to check the potential of this facility for research concerning VOCs. The different models and modeling assumptions are discussed. A dynamic VOC source model, derived from literature, is used as proxy to obtain possible VOC concentrations. The results show an important influence of temperature and humidity on the indoor VOC levels with VOC concentrations exceeding health guidelines. It is therefore important to design DCV systems and controls taking into account possible elevated VOC levels and while doing so, incorporate the dynamic behavior (influence of temperature and humidity) of the VOC emissions.

Performance assessment of demand controlled ventilation controls concerning indoor VOC exposure based on a dynamic VOC emission model

The performance assessment of ventilation systems often focusses only on CO2 and humidity levels. The indoor Volatile Organic Compounds (VOC) emissions of building materials or other products is thereby overlooked. The new generation of ventilation systems, Demand Controlled Ventilation (DCV), are systems that do not supply the nominal airflow continuously but are controlled by CO2 or humidity sensors in order to save energy. This poses potential problems for exposure to VOCs. In this study, a dynamic VOC model, which takes into account changing temperature and humidity that was derived from literature, is implemented in a CONTAM model of the Belgian reference apartment. The impact of a DCV system on the indoor VOC levels is investigated. Results show that the use of a dynamic model is necessary compared to the previously used approximation of a constant emission. Furthermore, on a system level, the influence of the ventilation system control on the indoor VOC levels shows. The overall VOC concentration in the different rooms will be higher because of lowered ventilation rates. Especially in rooms that are often unoccupied during the day, the accumulation of VOCs shows. In the development of DCV system controls, the aspect of VOC exposure should not be overlooked to be able to benefit from both the energy savings and improved Indoor Air Quality (IAQ).

Estimation of sources and factors affecting indoor VOC levels using basic numerical methods

Volatile Organic Compounds (VOCs) are a concern due to their adverse health effects and extensive usage. Levels of indoor VOCs were measured in six homes located in three different towns in Canakkale, Turkey. Monthly indoor VOC samples were collected by passive sampling throughout a year. The highest levels of total volatile organic compounds (TVOC), benzene, toluene, and xylenes occurred in industrial, rural, and urban sites in a descending order. VOC levels were categorized as average values annually, during the heating period, and non-heating period. Several building/environmental factors together with occupants’ habits were scored to obtain a basic indoor air pollution index (IAPi) for the homes. Bivariate regression analysis was applied to find the associations between the pollutant levels and home scores. IAPi scores were found to be correlated with average indoor VOC levels. In particular, very strong associations were found for occupants’ habits. Furthermore, observed indoor VOC levels were categorized by using self-organizing map (SOM) and two simple scoring approaches, rounded average and maximum value methods, to classify the indoor environments based on their VOC compositions (IAPvoc). Three classes were used for both IAPi and IAPvoc approaches, namely “good”, “moderate”, and “bad”. There is an urgent need for indexing studies to determine the potential sources and/or factors affecting observed VOCs. This study gives a basic but good start for further studies.

Levels and sources of volatile organic compounds in homes of children with asthma

Many volatile organic compounds (VOCs) are classified as known or possible carcinogens, irritants, and toxicants, and VOC exposure has been associated with the onset and exacerbation of asthma. This study characterizes VOC levels in 126 homes of children with asthma in Detroit, Michigan, USA. The total target VOC concentration ranged from 14 to 2274 μg/m(3) (mean = 150 μg/m(3); median = 91 μg/m(3)); 56 VOCs were quantified; and d-limonene, toluene, p, m-xylene, and ethyl acetate had the highest concentrations. Based on the potential for adverse health effects, priority VOCs included naphthalene, benzene, 1,4-dichlorobenzene, isopropylbenzene, ethylbenzene, styrene, chloroform, 1,2-dichloroethane, tetrachloroethene, and trichloroethylene. Concentrations varied mostly due to between-residence and seasonal variation. Identified emission sources included cigarette smoking, solvent-related emissions, renovations, household products, and pesticides. The effect of nearby traffic on indoor VOC levels was not distinguished. While concentrations in the Detroit homes were lower than levels found in other North American studies, many homes had elevated VOC levels, including compounds that are known health hazards. Thus, the identification and control of VOC sources are important and prudent, especially for vulnerable individuals. Actions and policies to reduce VOC exposures, for example, sales restrictions, improved product labeling, and consumer education, are recommended. Total target VOC concentrations in the Detroit homes ranged from 14 to 2274 lg/m3, generally lower than found in earlier studies. However, a subset of houses had elevated concentrations, and levels of 1,4-dichlorobenzene, naphthalene, and benzene reached levels commensurate with excess individual cancer risks of 10(-2), 10(-3), and 10(-4), respectively. VOC concentrations varied mostly due to between-residence and season effects. The most important sources included cigarette smoking, vehicle-related emissions, building renovation, solvents, household products, and pesticides.

Indoor VOCs from Religious and Ritual Burning Practices in India

Measurements of selected volatile organic compounds (VOCs), known as markers of emissions resulting from burning practices using natural- and synthetic biomaterials, have been carried out in major religious/ritual-indoors in India. Four different religious/ritual-indoors were selected for monitoring purposes: 1) Hindu Marriage Places (MP), 2) Muslim Holy Shrines (MG), 3) Buddhist Temples (BT), and 4) Hindu Temples (HT). One pure residential-indoor (RESID) site was also examined for comparison studies. Indoor VOCs sampling was carried out throughout the three seasons of summer, fall and winter of the calendar year of 2012–2013 in Raipur, India. VOCs samples, collected by passive sampling over a 48-h period, were analyzed using thermal desorption (TD), followed by high-resolution gas chromatographic separation and mass spectrometric detection (GC/MS). A total of 14 volatile organic compounds (n-hexane, cyclohexane, n-heptane, noctane, n-nonane, n-decane, n-undecane, styrene, o-xylene, m,p-xylene, 1,2,4-trimethyl benzene, ethylbenzene, benzene, and toluene.) were quantified. The annual mean concentrations for total VOCs (TVOCs) were 216.61 ± 75.15, 656.34 ± 220.82, 681.75 ± 219.83, 129.51 ± 45.24 and 82.67 ± 40.96 µg/m 3 for MP, MG, BT, HT and RESID respectively. The results were found to be higher than the prescribed standards and earlier reported indoor VOCs levels. Indoor/outdoor ratios (I/O), correlation analyses, seasonal variations and indoor/outdoor contributions to the measured levels are also investigated.

Selective permeation of moisture and VOCs through polymer membranes used in total heat exchangers for indoor air ventilation

Fresh air ventilation is central to indoor environmental control. Total heat exchangers can be key equipment for energy conservation in ventilation. Membranes have been used for total heat exchangers for more than a decade. Much effort has been spent to achieve water vapor permeability of various membranes; however, relatively little attention has been paid to the selectivity of moisture compared with volatile organic compounds (VOCs) through such membranes. In this investigation, the most commonly used membranes, both hydrophilic and hydrophobic ones, are tested for their permeability for moisture and five VOCs (acetic acid, formaldehyde, acetaldehyde, toluene, and ethane). The selectivity of moisture vs. VOCs in these membranes is then evaluated. With a solution-diffusion model, the solubility and diffusivity of moisture and VOCs in these membranes are calculated. The resulting data could provide some reference for future material selection. Total heat exchangers are important equipment for fresh air ventilation with energy conservation. However, their implications for indoor air quality in terms of volatile organic compound permeation have not been known. The data in this article help us to clarify the impacts on indoor VOC levels of membrane-based heat exchangers. Guidelines for material selection can be obtained for future use total heat exchangers for building ventilation.

Impact of regulation on indoor volatile organic compounds in new unoccupied apartment in Korea

Abstract The Indoor Air Quality (IAQ) Control in Public Use Facilities Act in Korea, which came into effect on January 1, 2006, set standards of indoor environmental concentrations for benzene, toluene, ethylbenzene, xylenes, styrene, and formaldehyde. This study aimed to determine the impact of the Act on levels of volatile organic compounds (VOCs) and to identify factors associated with indoor VOCs levels. VOCs and formaldehyde levels were measured in 228 new, unoccupied apartments from 2005 to 2007. In 2005, the mean total VOC (TVOC) concentration in 108 unoccupied apartments was 1606 μg m−3. After 2006, mean TVOC concentration in 120 unoccupied apartments was 645 μg m−3, significantly lower than the 2005 level. In 2005, the percentages of apartments exceeding standards were 14% for xylenes, 5% for ethylbenzene, 3% for toluene, and 1% for formaldehyde. After 2006, no apartment exceeded standards. When other building characteristics were controlled, the concentrations of TVOC, toluene, ethylbenzene, xylenes, and formaldehyde after 2006 were significantly lower than 2005 levels. However, benzene and styrene levels did not change. The reduction in VOCs levels was significantly associated with flooring materials, adhesive, and paint. These findings demonstrate that regulation can reduce VOC concentrations in new apartments through the use of low-emission building materials.

A Comparative Study of Indoor VOC Exposures and Associated Cancer Risk in Four North American Cities

WS4-06 Abstract: Recent studies have shown that indoor exposures to volatile organic compounds (VOCs) can significantly contribute to cancer risk. Although indoor VOC levels may originate from outdoor sources, exposures to these compounds are typically controlled by emissions from numerous indoor sources, including building materials, floor and wall coverings, tobacco smoking, consumer products, and volatilization from indoor water use. Although a detailed source apportionment can be difficult in this context, the coincident collection of indoor, outdoor, and personal samples allows for a determination of the relative contribution of source location(s) for measured compounds. Studies that use these methodologies can be used to understand exposure pathways, set research priorities, and design interventions focused on risk reduction. We present the results from personal exposure studies conducted in 4 large North American cities: Boston, New York, Los Angeles, and Mexico City. These studies used personal, indoor, and outdoor air sampling methods to assess the relative contribution of indoor and outdoor sources to personal exposures. These exposure estimates were used to estimate cancer risk through inhalation using published unit risk values. Despite significant ambient sources in large urban areas, indoor VOC sources were shown to contribute a significant portion of cancer risk across these cities. Exposures that contributed significantly to this risk include: 1,4-dichlorobenzene, chloroform, and several aldehydes, particularly formaldehyde. For example, in both Los Angeles and New York, indoor sources of these compounds accounted for more than 40% of the total cancer risk based on personal exposures. These studies highlight the importance of indoor VOC sources as a contributor to health risk. This comparative analysis presents data on the dominant pathways of exposure, the magnitude of cancer risk from measured exposures, and the observed between-city differences that may shed light on controlling variables such as product types, product use patterns, and differences in housing stock.

Volatile organic compounds concentrations in residential indoor and outdoor and its personal exposure in Korea

To date, personal volatile organic compounds (VOCs) exposure and residential indoor and outdoor VOCs levels have not been characterized in Korea. In this study, residential indoor and outdoor VOCs concentrations were measured and compared simultaneously with the personal exposure for each of 30 participants in a medium city, Asan, and in a metropolitan city, Seoul. Factors that influence personal VOCs exposures were assessed in relation to house characteristics and time activity information. All VOC concentrations were measured using passive samplers during a 24-h period and analyzed using GC-MS. Ten target VOCs were benzene, trichloroethylene, toluene, o-xylene, p-xylene, ethylbenzene, MIBK, n-octane, styrene, and 1,2-dichlorobenzene. Residential indoor and outdoor VOCs concentrations measured in Seoul were significantly higher than those in Asan. Indoor/outdoor (I/O) ratios for all target compounds ranged from 0.94 to 1.51 and I/O ratios of Asan were a little higher than those of Seoul. Results indicate that time activity information can be used to predict personal exposures, although such predictions will result in an over estimation compared to measured exposures. Factors which influence the indoor VOCs level and its personal exposure in relation to house characteristics included house age, indoor smoking, and house type.

Estimation of optimum requirements for indoor air quality and energy consumption in some residences in Kuwait

Contrasting effects of the dilution of indoor generated pollutants and the energy efficiency of heating and ventilating air conditioning systems (HVAC) for indoor air quality (IAQ) and thermal comfort were studied for 10 Kuwaiti residences. The levels of volatile organic compounds (VOCs) and the calculated cooling load of the HVAC systems were used as indicators for the IAQ and for the energy consumption, respectively. Air exchange rates and VOCs levels (both indoor and outdoor) were measured. It was found that the outdoor VOC concentrations were always less than the indoor values. Therefore reduction of indoor VOC levels can be accomplished either by increasing the ratio of the makeup air to the recirculation air of the HVAC system or by increasing the infiltration airflow rate through openings. A single compartment IAQ model, modified by the authors, was used to test for the variation in the above two dilution modes and to test the performance sensitivity. Hence, the optimum parameters in terms of IAQ and energy consumption were determined. The results indicated that it was necessary to increase the ratio of the makeup air to the recirculation air from its typical design value of 0.5 to a range of 0.7–1.3 in order to reduce indoor VOC to acceptable levels.

Volatile organic compounds in dutch homes

Weekly average concentrations of 45 volatile organic compounds (VOC) were determined in living rooms of more than 300 homes divided in three age groups. Repeated measurements of the same VOC were carried out in 4 homes every second week for half a year, and in 11 newly built homes before and during occupancy. The results of this exploratory study showed that virtually all VOC had higher indoor than outdoor concentrations; a wide range in indoor VOC levels was observed. Clusters of solvent type compounds were tentatively identified, which suggests the existence of common sources. The repeated measurements showed fairly stable indoor levels for some compounds in some homes, while large variations were observed for other compounds and other homes. During the first few months of occupation, the straight-chain and aromatic hydrocarbon concentrations were generally higher than in older homes. It is concluded that most of the measured VOC have both consumer products and building materials as indoor sources. The highest observed concentrations in the occupied homes were probably the result of incidental occupant activities.