Sources of formaldehyde,other aldehydes and terpenes in a new manufactured house

Formaldehyde, less volatile aldehydes, and terpene hydrocarbons are generally the predominant air contaminants in new manufactured and site-built houses. This study was conducted to identify the major sources of these compounds in a typically constructed, new manufactured house and to evaluate several source reduction practices. Specimens of materials used within the house were collected. These were individually pre-conditioned for 19 +/- 4 days, and tested for emissions of formaldehyde and other target compounds using small-scale chambers. Several cabinetry materials, passage doors, and the plywood subfloor were the predominant sources of formaldehyde and other aldehydes. The plywood subfloor was the predominant terpene source. Whole-house emission rates for combined materials were predicted based on the emission factors and the corresponding material quantities. These predicted rates were compared with whole-house emission rates derived from measurements made at the house 3 months after its installation. For 10 of 14 target compounds including formaldehyde, the predicted and derived rates were within a factor of two. Four emission barriers applied to plywood were shown to reduce emission factors for formaldehyde, hexanal, and other aldehydes.     

Variations of formaldehyde and VOC levels during 3 years in new and older homes

Indoor air organic compounds were continuously monitored during 3 years in new and older homes which were voluntarily selected throughout countries. The levels of volatile organic compounds (VOCs) in the new homes decreased markedly after 1 year, and steady emissions of VOCs were obtained in the initial months. Formaldehyde and a-pinene related to wooden materials need a longer flushing period than the other compounds in the new homes. The levels of the indoor air organic compounds in the older homes showed no significant fluctuation during the 3-year period. Decreases of the indoor-produced compounds in the new homes did not depend upon the ventilation systems. The results indicate that the indoor-produced compounds in the new homes will be more influenced by the aging decreases of emission source strengths than ventilation systems. The quantitative information on the trend of the indoor air organic compound levels will be useful for the risk assessment of indoor exposure to those compounds, and also for Japanese IAQ guidelines. PRACTICAL IMPLICATIONS: The initial levels of VOCs in the new homes decreased dramatically and were close to the mean values for the older homes after one year. The results suggest that steady emissions of VOCs are obtained within initial months. However, formaldehyde and a-pinene did not follow the trend for VOCs, particularly in the wooden framed houses. The results tend to suggest that formaldehyde and a-pinene related to wooden materials will need more long a flushing period than other compounds in the new homes. Decreasing tendency of indoor air organic compound levels in the new homes did not appear to show any dependency upon the ventilation systems over the whole period. Absence of data for ventilation rates in the houses dose not permit interpretation of the relation between ventilation rates and indoor air organic compound levels with statistical certainty, but the results suggest that indoor air organic compound levels in the homes will be more influenced by emission source strengths than ventilation systems. The levels of indoor air organic compounds in the new homes are sufficiently decreased according to the ageing decreases of organic compounds when the home is ventilated with adequate quantities.     

Volatile organic compounds in fourteen U.S. retail stores

Retail buildings have a potential for both short‐term (customer) and long‐term (occupational) exposure to indoor pollutants. However, little is known about volatile organic compound (VOC) concentrations in the retail sector and influencing factors, such as ventilation, in‐store activities, and store type. We measured VOC concentrations and ventilation rates in 14 retail stores in Texas and Pennsylvania. With the exception of formaldehyde and acetaldehyde, VOCs were present in retail stores at concentrations well below health guidelines. Indoor formaldehyde concentrations ranged from 4.6 ppb to 67 ppb. The two mid‐sized grocery stores in the sample had the highest levels of ethanol and acetaldehyde, with concentrations up to 2.6 ppm and 92 ppb, respectively, possibly due to the preparation of dough and baking activities. Indoor‐to‐outdoor concentration ratios indicated that indoor sources were the main contributors to indoor VOC concentrations for the majority of compounds. There was no strong correlation between ventilation and VOC concentrations across all stores. However, increasing the air exchange rates at two stores led to lower indoor VOC concentrations, suggesting that ventilation can be used to reduce concentrations for some specific stores.     

The development of low volatile organic compound emission house—a case study

An aim in developing low volatile organic compound (VOCs) emission house is to reduce the level of VOCs in domestic housing. In this study, a case study for the reduction of exposure to VOCs from a newly constructed residential house was presented. Before application, the construction materials used in the house were tested in an environmental chamber and low VOC emission materials were then selected. Design of the house abided by the following principals: maximizing the ventilation rate and avoiding the use of high VOC emission materials in the house. By improved building design and proper construction materials selection, risk of personal exposure to VOCs in the house was significantly reduced. The total VOCs (TVOCs) concentrations measured in the house ranged from non-detectable to 43 μg/m³. These values were much lower than the published values (0.48–31.7 mg/m³) for new houses in Scandinavian countries and in the USA. The low TVOCs concentrations obtained in this study probably resulted from the high ventilation rates and the use of low VOCs emission materials. This study also combined the results with the three traditional ways in improvement of IAQ. The results obtained in this study confirmed that the most effective strategy for controlling IAQ was pollution prevention and the next most important was the design of ventilation rates to handle uncontrollable sources. The effectiveness of aging as a means of indoor pollution control was also reviewed.     

A study on the identification and quantification of sources of VOCs in 5 air-conditioned Singapore office buildings

Sources of VOCs were identified and quantified in five tropical air-conditioned office buildings in Singapore. A mass balanced model is applied to determine area-specific emission rates and to apportion the sources of VOCs into 3 broad categories of sources—building materials, ventilation systems and occupants and their activities. The highest contributor of TVOCs comes from the ventilation systems at 39.0%. This was followed by occupants and their activities at 37.3% and finally building materials at 23.7%. Ducted supply and return ventilation design has the lowest VOC area-specific emission rates as compared to buildings employing the open space above the false ceiling as return plenum. The TVOC area-specific emission rates from building materials and ventilation systems decreased from 6 to 12 months. However, some VOCs showed increased emission rates over the same period demonstrating sink effects which resulted in secondary emissions.     

Long-term Emission of Volatile Organic Compounds from Waterborne Paints – Methods of Comparison

The emission of volatile organic compounds (VOCs) from five different waterborne paints was measured in small climatic chambers under standard conditions over a one-year period. The aims of the study were to evaluate the time emission profiles and to develop methods for comparison of different paints. The paints were applied to tin-plated steel sheets. VOCs were sampled on Tenax TA and analysed by thermal desorption and gas chromatography. The chamber concentrations increased rapidly during the first few hours and then decreased as the emission rates dropped. A model expression including an exponentially decreasing emission rate of the paint film, the air exchange rate, and a normalization of the film thickness was fitted to the concentration versus time data. The time required to reach a given emission rate was estimated and found suitable for comparison of the emission of VOCs from the paints. It was found that data sampled within three weeks or less may be sufficient to predict the emission of VOCs up to one year. Reduction of long-term emissions may be achieved most efficiently by (1) substituting a more -volatile VOC whose emission is controlled by evaporation for a less volatile VOC characterized by diffusion-controlled emission and (2) reducing the paint film thickness rather than reducing the initial VOC content of the paint.     

Occupational exposure and health risks of volatile organic compounds of hotel housekeepers: Field measurements of exposure and health risks

Hotel housekeepers represent a large, low-income, predominantly minority, and high-risk workforce. Little is known about their exposure to chemicals, including volatile organic compounds (VOCs). This study evaluates VOC exposures of housekeepers, sources and factors affecting VOC levels, and provides preliminary estimates of VOC-related health risks. We utilized indoor and personal sampling at two hotels, assessed ventilation, and characterized the VOC composition of cleaning agents. Personal sampling of hotel staff showed a total target VOC concentration of 57 ± 36 µg/m³ (mean ± SD), about twice that of indoor samples. VOCs of greatest health significance included chloroform and formaldehyde. Several workers had exposure to alkanes that could cause non-cancer effects. VOC levels were negatively correlated with estimated air change rates. The composition and concentrations of the tested products and air samples helped identify possible emission sources, which included building sources (for formaldehyde), disinfection by-products in the laundry room, and cleaning products. VOC levels and the derived health risks in this study were at the lower range found in the US buildings. The excess lifetime cancer risk (average of 4.1 × 10⁻⁵) still indicates a need to lower exposure by reducing or removing toxic constituents, especially formaldehyde, or by increasing ventilation rates.     

Do time‐averaged,whole‐building,effective volatile organic compound (VOC) emissions depend on the air exchange rate? A statistical analysis of trends for 46 VOCs in U.S. offices

We used existing data to develop distributions of time‐averaged air exchange rates (AER), whole‐building ‘effective’ emission rates of volatile organic compounds (VOC), and other variables for use in Monte Carlo analyses of U.S. offices. With these, we explored whether long‐term VOC emission rates were related to the AER over the sector, as has been observed in the short term for some VOCs in single buildings. We fit and compared two statistical models to the data. In the independent emissions model (IEM), emissions were unaffected by other variables, while in the dependent emissions model (DEM), emissions responded to the AER via coupling through a conceptual boundary layer between the air and a lumped emission source. For 20 of 46 VOCs, the DEM was preferable to the IEM and emission rates, though variable, were higher in buildings with higher AERs. Most oxygenated VOCs and some alkanes were well fit by the DEM, while nearly all aromatics and halocarbons were independent. Trends by vapor pressure suggested multiple mechanisms could be involved. The factors of temperature, relative humidity, and building age were almost never associated with effective emission rates. Our findings suggest that effective emissions in real commercial buildings will be difficult to predict from deterministic experiments or models.     

Performance of ultraviolet photocatalytic oxidation for indoor air cleaning applications

Ultraviolet photocatalytic oxidation (UVPCO) systems for removal of volatile organic compounds (VOCs) from air are being considered for use in office buildings. Here, we report an experimental evaluation of a UVPCO device with tungsten oxide modified titanium dioxide (TiO2) as the photocatalyst. The device was challenged with complex VOC mixtures. One mixture contained 27 VOCs characteristic of office buildings and another comprised 10 VOCs emitted by cleaning products, in both cases at realistic concentrations (low ppb range). VOC conversion efficiencies varied widely, usually exceeded 20%, and were as high as approximately 80% at about 0.03 s residence time. Conversion efficiency generally diminished with increased airflow rate, and followed the order: alcohols and glycol ethers > aldehydes, ketones, and terpene hydrocarbons > aromatic and alkane hydrocarbons > halogenated aliphatic hydrocarbons. Conversion efficiencies correlated with the Henry's law constant more closely than with other physicochemical parameters. An empirical model based on the Henry's law constant and the gas-phase reaction rate with hydroxyl radical provided reasonable estimates of pseudo-first order photocatalytic reaction rates. Formaldehyde, acetaldehyde, acetone, formic acid and acetic acid were produced by the device due to incomplete mineralization of common VOCs. Formaldehyde outlet/inlet concentration ratios were in the range 1.9-7.2. PRACTICAL IMPLICATIONS: Implementation of air cleaning technologies for both VOCs and particles in office buildings may improve indoor air quality, or enable indoor air quality levels to be maintained with reduced outdoor air supply and concomitant energy savings. One promising air cleaning technology is ultraviolet photocatalytic oxidation (UVPCO) air cleaning. For the prototype device evaluated here with realistic mixtures of VOCs, conversion efficiencies typically exceeded the minimum required to counteract predicted VOC concentration increases from a 50% reduction in ventilation. However, the device resulted in the net generation of formaldehyde and acetaldehyde from the partial oxidation of ubiquitous VOCs. Further development of the technology is needed to eliminate these hazardous air pollutants before such a UVPCO device can be deployed in buildings.     

Evaluation of impact factors on VOC emissions and concentrations from wooden flooring based on chamber tests

In this study, the impact factors of temperature, relative humidity (RH), air exchange rate, and volatile organic compound (VOC) properties on the VOC (toluene, n-butyl acetate, ethylbenzene, and m,p-xylene) specific emission rates (SERs) and concentrations from wooden flooring were investigated by chamber test for 8 days. The tested wood in this study is not common solid wood, but composite wood made of combined wood fibers. The experiments were conducted in a stainless-steel environmental test chamber coated with Teflon. The experimental results within 8 days of testing showed that, when the temperature increased from 15 to 30 °C, the VOC SERs and concentrations increased 1.5–129 times. When the RH increased from 50% to 80%, the VOC concentrations and SERs increased 1–32 times. When the air change rate increased from 1 to 2 h⁻¹, the VOC concentrations decreased 9–40%, while the VOC SERs increased 6–98%. The relations between the boiling points of the VOCs and each of the normalized VOC SERs and concentrations were linear with negative slopes. The relations between the vapor pressures of the VOCs and each of the normalized VOC SERs and concentrations were linear with positive slopes. At 15 °C, RH50%, the relations between the diffusivities of VOCs and each of the normalized VOC equilibrium SERs and concentrations were linear with a positive slope.     

TVOC and formaldehyde emission behaviors from flooring materials bonded with environmental-friendly MF/PVAc hybrid resins

Polyvinyl acetate (PVAc) was added as a replacement for melamine-formaldehyde (MF) resin in the formaldehyde-based resin system to reduce formaldehyde and volatile organic compound (VOC) emissions from the adhesives used between plywoods and fancy veneers. A variety of techniques, including 20-l chamber, field and laboratory emission cell (FLEC), VOC analyzer and standard formaldehyde emission test (desiccator method), were used to determine the formaldehyde and VOC emissions from engineered flooring bonded with five different MF resin and PVAc blends at MF/PVAc ratios of 100:0, 70:30, 50:50, 30:70 and 0:100. Although urea-formaldehyde (UF) resin had the highest formaldehyde emission, the emission as determined by desiccator method was reduced by exchanging with MF resin. Furthermore, the formaldehyde emission level was decreased with increasing addition of PVAc as the replacement for MF resin. UF resin in the case of beech was over 5.0 mg/l, which exceeded E2 (1.5-5.0 mg/l) grade. However, MF30:PVAc70 was 相似文献   

Estimation of biogenic volatile organic compounds emissions in subtropical island--Taiwan

Elevated tropospheric ozone is harmful to human health and plants. It is formed through the photochemical reactions involving volatile organic compounds (VOCs) and nitrogen oxides (NO(x)). The elevated ozone episodes occur mainly in summer months in the United States, while the high-ozone episodes frequently occur during the fall in Taiwan. The unique landscape of Taiwan produces tremendous amounts of biogenic VOCs in the mountain regions that are adjacent to concentrated urban areas. The urban areas, in turn, generate prodigious amounts of anthropogenic emissions. Biogenic VOC emissions have direct influence on tropospheric ozone formation. To explore the air quality problems in Taiwan, this study attempts to develop a biogenic VOC emission model suitable for air quality applications in Taiwan. The emission model is based on the Biogenic Emissions Inventory System Version 2 and coupled with a detailed Taiwan land use database. The 1999 total Taiwan biogenic VOC emissions were estimated at 214,000 metric tons. The emissions of isoprene, monoterpenes, and other VOCs were about 37.2%, 30.4%, and 32.4% of total biogenic VOC emissions, respectively. The annual total biogenic VOC emission per unit area was more than two times the value of that in any European country, implying that detailed emissions estimates in any size of region will benefit the global biogenic emission inventories.     

The effect of temperature on the emission of formaldehyde and volatile organic compounds (VOCs) from laminate flooring — case study

The effect of temperatures of 23, 29, 50°C on formaldehyde and volatile organic compounds (VOCs) emission from laminate flooring Type A (with particleboard as substrate) and Type B (with high density fibre (HDF)) was examined. At 23 and 29°C the measurements did not show any emissions of formaldehyde and very low emissions of VOCs. At a temperature of 50°C, Type A showed a high initial emission of formaldehyde and VOCs, which decreased with time. The emission from Type B was much lower. In conclusion, some laminate flooring may affect the chemical contamination of indoor air with the use of floor heating.     

Emission behavior of formaldehyde and TVOC from engineered flooring in under heating and air circulation systems

Formaldehyde and volatile organic compounds (VOCs) from the adhesive, flooring, and flooring with adhesive were measured using a desiccator, a 20-L chamber and a field and laboratory emission cell (FLEC). Flooring with an adhesive is similar to that used in construction was applied to a floor heating system and an air circulation system, and the surface temperature of the flooring was set to 20 °C, 26 °C and 32 °C. The rate of formaldehyde emission from the flooring was the highest at 32 °C using a desiccator and decreased with time. The formaldehyde and aldehyde emissions from the samples using a 20-L chamber and FLEC showed a similar tendency. The VOCs emission trends with the 20-L chamber and FLEC were similar. The rate of formaldehyde and TVOC emission determined using FLEC was higher than that determined using the 20-L chamber method. The flooring emitted primarily benzene, toluene, ethylbenzene, styrene, xylene, as well as some unknown VOCs. There was a strong correlation between formaldehyde and TVOC emission for the 20-L chamber and FLEC. Samples using a floor heating system showed higher formaldehyde emission than those using an air circulation system. The level of TVOC emission was higher from the samples using an air circulation system than those using the floor heating system.     

Investigation of volatile organic compounds in office buildings in Bangkok,Thailand: Concentrations,sources, and occupant symptoms

To conserve energy, office buildings with air-conditioning systems in Thailand are operated with a tight thermal envelope. This leads to low fresh-air ventilation rates and is thought to be partly responsible for the sick building syndrome symptoms reported by occupants. The objectives of this study are to measure concentrations and to determine sources of 13 volatile organic compounds (VOCs) in office buildings with air-conditioning systems in the business area of Bangkok. Indoor and outdoor air samples from 17 buildings were collected on Tenax-TA^™ sorbent tubes and analyzed for individual VOCs by thermal desorption-gas chromatography/mass spectrometry (TD–GC/MS). Building ventilation was measured with a constant injection technique using hexafluorobenzene as a tracer gas. The results show that the VOC concentrations varied significantly among the studied buildings. The two most dominant VOCs were toluene and limonene with average concentrations of 110 and 60.5 μg m⁻³, respectively. A Wilcoxon sum rank test indicated that the indoor concentrations of aromatic compounds and limonene were statistically higher than outdoor concentrations at the 0.05 level, while the indoor concentrations of chlorinated compounds were not. Indoor emission factors of toluene and limonene were found to be highest with the average values of 80.9 and 18.9 μg m⁻² h⁻¹, respectively. Principal component analysis was applied to the emission factors of 13 VOCs, producing three components based on source similarities. Furthermore, a questionnaire survey investigation and field measurements of building air exchange pointed to indoor air complaints related to inadequate ventilation.     

建筑装饰材料挥发性有机物的散发模型

分析了现有室内挥发性有机物(VOC)散发模型存在的问题，建立了室内VOC散发的通用模型，该模型适用于两种情况：一是计算各种条件下室内VOC的浓度；二是已知房间内允许的VOC浓度，计算VOC散发量，为吸附器、光催化设备的选择和通风量的确定提供依据。     

Contaminant levels,source strengths,and ventilation rates in California retail stores

This field study measured ventilation rates and indoor air quality in 21 visits to retail stores in California. Three types of stores, such as grocery, furniture/hardware stores, and apparel, were sampled. Ventilation rates measured using a tracer gas decay method exceeded the minimum requirement of California's Title 24 Standard in all but one store. Concentrations of volatile organic compounds (VOCs), ozone, and carbon dioxide measured indoors and outdoors were analyzed. Even though there was adequate ventilation according to standard, concentrations of formaldehyde and acetaldehyde exceeded the most stringent chronic health guidelines in many of the sampled stores. The whole‐building emission rates of VOCs were estimated from the measured ventilation rates and the concentrations measured indoor and outdoor. Estimated formaldehyde emission rates suggest that retail stores would need to ventilate at levels far exceeding the current Title 24 requirement to lower indoor concentrations below California's stringent formaldehyde reference level. Given the high costs of providing ventilation, effective source control is an attractive alternative.     

Spatial and temporal variability in VOC levels within a commercial retail building

A study was performed to characterize the concentration of dozens of volatile organic compounds (VOCs) at 10 locations within a single large building and track these concentrations over a 2-year period. The study was performed at a shopping center (strip mall) in New Jersey. A total of 130 indoor air samples were collected from 10 retail stores within the shopping center and analyzed for 60 VOCs by US EPA Method TO-15. Indoor concentrations of up to 55,100 microg/m(3) were measured for individual VOCs. The indoor/outdoor ratio (I/O) was as high as 1500 for acetone and exceeded 100 at times for various compounds, indicating that significant indoor air sources were present. A large degree of spatial variability was observed between stores within the building, with concentrations varying by three to four orders of magnitude for some compounds. The spatial variability was dependent on the proximity of the sampling locations to the indoor sources. A large degree of temporal variability also was observed for compounds emitted from indoor sources, but the temporal variability generally did not exceed two standard deviations (sigma). For compounds not emitted from indoor sources at significant rates, both the spatial and temporal variability tended to range within an order of magnitude at each location. PRACTICAL IMPLICATIONS: Many cross-sectional studies have been published where the levels of volatile organic compounds (VOCs) were measured in indoor air at one or two locations for houses or offices. This study provides longitudinal data for a commercial retail building and also addresses spatial variability within the building. The data suggest that spatial and temporal variability are important considerations for compounds emitted from indoor sources. Elevated concentrations were found in retail spaces with no apparent emission sources due to their proximity to other retail spaces with emission sources.     

Factors controlling volatile organic compounds in dwellings in Melbourne,Australia

This study characterized indoor volatile organic compounds (VOCs) and investigated the effects of the dwelling characteristics, building materials, occupant activities, and environmental conditions on indoor VOC concentrations in 40 dwellings located in Melbourne, Australia, in 2008 and 2009. A total of 97 VOCs were identified. Nine VOCs, n‐butane, 2‐methylbutane, toluene, formaldehyde, acetaldehyde, d‐limonene, ethanol, 2‐propanol, and acetic acid, accounted for 68% of the sum of all VOCs. The median indoor concentrations of all VOCs were greater than those measured outdoors. The occupant density was positively associated with indoor VOC concentrations via occupant activities, including respiration and combustion. Terpenes were associated with the use of household cleaning and laundry products. A petroleum‐like indoor VOC signature of alkanes and aromatics was associated with the proximity of major roads. The indoor VOC concentrations were negatively correlated (P < 0.05) with ventilation. Levels of VOCs in these Australian dwellings were lower than those from previous studies in North America and Europe, probably due to a combination of an ongoing temporal decrease in indoor VOC concentrations and the leakier nature of Australian dwellings.     

Characterization Of Ofice Dust By VOCs And TVOC Release - Identification Of Potential Irritant VOCs By Partial Least Squares Analysis

Floor dust from nine city hall office buildings was separated into fiber and particulate fractions and analyzed for volatile organic compounds (VOCs) and total VOC (TVOC) by thermal desorption/high resolution gas chromatography (HRGC). Components were identified by HRGC/mass spectroscopy (MS). Principal component analysis was applied to VOC emission profiles revealing similarities between buildings and correlations between profiles and SBS symptoms of mucous membrane irritation and “concentration difficulty”. While the dominant pattern in emission profiles was not correlated with SBS irritation complaints, partial least squares analysis in latent variables (PLS analysis) identified VOCs for which peak areas were correlated with SBS irritation complaints and the CNS Complaint, “concentration difficulty”