A study on dynamic volatile organic compound emission characterization of water-based paints

Volatile organic compounds (VOCs) emitted from surface coatings have caused growing public concern for air quality. Even the low-emitted VOC impact from water-based paints on indoor air quality in urban areas has caused concern. This paper presents experimental data using a mathematical model to simulate dynamic VOC emissions from water-based paints that is based on mass transfer and molecular diffusion theories. A series of field-analogous experiments were carried out to continuously measure the VOCs emitted from two typical water-based paints using a gas chromatography-flame-ionization detector monitor in an artificial wind tunnel system. In the study cases, the mass flux of VOCs emitted from the water-based paints was up to 50 microg/m2sec. It was found that the time needed to completely emit VOCs from water-based paints is just hundreds of seconds. However, the order of magnitude of the VOC emission rate from water-based paints is not lower than that from some dry building materials and solvent-based paints. The experimental data were used to produce a useful semiempirical correlation to estimate the VOC emission rates for water-based paints. This correlation is valid under appropriate conditions as suggested by this work with a statistical deviation of +/- 7.6%. With this correlation, it seems feasible to predict the dynamic emission rates for VOCs during a painting process. This correlation is applicable for assessing the hazardous air pollutant impact on indoor air quality or for environmental risk assessment. Associated with the dynamic VOC emission characterization, the air-exchange rate effect on the VOC emission rates is also discussed.     

Volatile organic compound concentrations, emission rates, and source apportionment in newly-built apartments at pre-occupancy stage

The present study investigated the indoor concentrations of selected volatile organic compounds (VOCs) and formaldehyde and their indoor emission characteristics in newly-built apartments at the pre-occupancy stage. In total, 107 apartments were surveyed for indoor and outdoor VOC concentrations in two metropolitan cities and one rural area in Korea. A mass balanced model was used to estimate surface area-specific emission rates of individual VOCs and formaldehyde. Seven (benzene, ethyl benzene, toluene, m,p-xylene, o-xylene, n-hexane, and n-heptane) of 40 target compounds were detectable in all indoor air samples, whereas the first five were detected in all outdoor air samples. Formaldehyde was also predominant in the indoor air samples, with a high detection frequency of 96%. The indoor concentrations were significantly higher than the outdoor concentrations for aromatics, alcohols, terpenes, and ketones. However, six halogenated VOCs exhibited similar concentrations for indoor and outdoor air samples, suggesting that they are not major components emitted from building materials. It was also suggested that a certain portion of the apartments surveyed were constructed by not following the Korean Ministry of Environment guidelines for formaldehyde emissions. Toluene exhibited the highest emission rate with a median value of 138 μg m⁻² h⁻¹. The target compounds with median emission rates greater than 20 μg m⁻² h⁻¹ were toluene, 1-propanol, formaldehyde, and 2-butanone. The wood panels/vinyl floor coverings were the largest indoor pollutant source, followed by floorings, wall coverings, adhesives, and paints. The wood panels/vinyl floor coverings contributed nearly three times more to indoor VOC concentrations than paints.     

Comparison of the substrate effect on voc emissions from water based varnish and latex paint

BACKGROUND, AIMS AND SCOPE: The building materials are recognised to be major contributors to indoor air contamination by volatile organic compounds (VOCs). The improvement of the quality of the environment within buildings is a topic of increasing research and public interest. Legislation in preparation by the European Commission may induce, in the near future, European Union Member States to solicit the industries of paints, varnishes and flooring materials for taking measures, in order to reduce the VOC emissions resulting from the use of their products. Therefore, product characterisation and information about the influence of environmental parameters on the VOC emissions are fundamental for providing the basic scientific information required to allow architects, engineers, builders, and building owners to provide a healthy environment for building occupants. On the other hand, the producers of coating building materials require this information to introduce technological alterations, when necessary, in order to improve the ecological quality of their products, and to make them more competitive. Studies of VOC emissions from wet materials, like paints and varnishes, have usually been conducted after applying the material on inert substrates, due to its non-adsorption and non-porosity properties. However, in real indoor environments, these materials are applied on substrates of a different nature. One aim of this work was to study, for the first time, the VOC emissions from a latex paint applied on concrete. The influence of the substrate (uncoated cork parquet, eucalyptus parquet without finishing and pine parquet with finishing) on the emissions of VOC from a water-based varnish was also studied. For comparison purposes, polyester film (an inert substrate) was used for both wet materials. METHODS: The specific emission rates of the major VOCs were monitored for the first 72 h of material exposure in the atmosphere of a standardized test chamber. The air samples were collected on Tenax TA and analysed using thermal desorption online with gas chromatography provided with both mass selective detection and flame ionisation detection. A double exponential model was applied to the VOC concentrations as a function of time to facilitate the interpretation of the results. RESULTS AND DISCUSSION: The varnish, which was introduced in the test chamber 23 h after the application of the last layer of material, emitted mainly glycolethers. Only primary VOCs were emitted, but their concentrations varied markedly with the nature of the substrate. The higher VOC concentrations were observed for the parquets of cork and eucalyptus, which indicated that they have a much higher porosity and, therefore, a higher power of VOC adsorption than the finished pine parquet (and polyester film). The paint was introduced in the chamber just after its application. Only primary VOCs were emitted (esters, phthalates, glycolethers and white spirit) but some compounds, like 2-(2-butoxyethoxy)ethanol and diethylphthalate, were only observed for paint/polyester, which suggested that they were irreversibly adsorbed by the paint/concrete. Compared with the inert substrate, the rate of VOC emissions was lower for concrete in the wet-stage (first hours after the paint application) but slightly higher later (dry-stage) as a consequence of desorption. CONCLUSIONS: As to varnish, the substrates without finishing, like cork and eucalyptus parquets, displayed a higher power of adsorption of VOCs than the pine parquet with finishing, probably because they have a higher porosity. As concerns paint, the total masses of VOCs emitted were lower for concrete than for polyester, indicating that concrete reduces the global VOC emissions from the latex paint. Concrete is seen to have a strong power of adsorption of VOCs. Some compounds, namely 2-(2-butoxyethoxy)ethanol, diethylphthalate and TEXANOL (this partially), were either irreversibly adsorbed by the concrete or desorbed very slowly (at undetected levels). A similar behaviour had not been reported for gypsum board, a paint substrate studied before. RECOMMENDATIONS AND OUTLOOK: The present data suggest that concrete may be a recommendable substrate for paint in an indoor environment. As the nature of the substrate conditions the rate and nature of VOC emissions from wet materials, it must be explicit when emissions from composite materials are reported, in order to allow comparisons and labelling of the product in terms of indoor air quality.     

Attitudes and Responses Towards Air Pollution in Medieval England

ABSTRACT

The concentrations of contaminants in the supply air of mechanically ventilated buildings may be altered by pollutant emissions from and interactions with duct materials. We measured the emission rate of volatile organic compounds (VOCs) and aldehydes from materials typically found in ventilation ducts. The emission rate of VOCs per exposed surface area of materials was found to be low for some duct liners, but high for duct sealing caulk and a neo-prene gasket. For a typical duct, the contribution to VOC concentrations is predicted to be only a few percent of common indoor levels. We exposed selected materials to ~100-ppb ozone and measured VOC emissions. Exposure to ozone increased the emission rates of aldehydes from a duct liner, duct sealing caulk, and neoprene gasket. The emission of aldehydes from these materials could increase indoor air concentrations by amounts that are as much as 20% of odor thresholds. We also measured the rate of ozone uptake on duct liners and galvanized sheet metal to predict how much ozone might be removed by a typical duct in ventilation systems. For exposure to a constant ozone mol fraction of 37 ppb, a lined duct would initially remove ~9% of the ozone, but over a period of 10 days the ozone removal efficiency would diminish to less than 4%. In an unlined duct, in which only galvanized sheet metal is exposed to the air-stream, the removal efficiency would be much lower, ~0.02%. Therefore, ducts in ventilation systems are unlikely to be a major sink for ozone.     

Seasonal patterns of non-terpenoid C6-C10 VOC emission from seven Mediterranean woody species

The seasonal pattern of non-terpenoid C6-C10 VOC emission by seven Mediterranean woody species (Bupleurum fruticosum, Cistus albidus, Pinus halepensis, Arbutus unedo, Erica arborea, Quercus coccifera, and Q. ilex) was studied under field conditions. Branch chamber samples were sorbed on carbotrap and analyzed by thermal desorption in combination with GC-MS. These non-terpenoid C6-C10 VOC emissions were large, almost of similar magnitude to those of terpenes. Overall, maximum values were recorded in spring and summer (up to 12 microg g(-1) DM h(-1) in Q. ilex) and minimum values in autumn and winter (up to 5 microg g(-1) DM h(-1) in Q. ilex). These C6-C10 VOC emissions represented 2.82% of the photosynthetic C fixation in summer and 0.22% in winter. Some compounds such as 2-ethoxyethyl acetate were emitted by most species, others such as 3-hexen-1-ol, phenol or decanal were significantly emitted only by few species. The greatest diversity of emitted non-terpenoid C6-C10 VOCs was observed in spring and in Q. ilex. Temperature seemed a strong driver of these seasonal changes but other species-specific and seasonal factors seem involved. These results indicate that C6-C10 non-terpenoid VOCs contribute a rather significant fraction of the total biogenic VOC flux from these Mediterranean species, especially in spring and summer, and therefore should be considered in VOC emission inventories and in model predictions of tropospheric chemistry.     

A mass transfer model for simulating VOC sorption on building materials

The sorption of volatile organic compounds (VOCs) by different building materials can significantly affect VOC concentrations in indoor environments. In this paper, a new model has been developed for simulating VOC sorption and desorption rates of homogeneous building materials with constant diffusion coefficients and material–air partition coefficients. The model analytically solves the VOC sorption rate at the material–air interface. It can be used as a “wall function” in combination with more complex gas-phase models that account for non-uniform mixing to predict sorption process. It can also be used in conjunction with broader indoor air quality studies to simulate VOC exposure in buildings.     

Using the chemical mass balance model to estimate VOC source contributions in newly built timber frame houses: a case study

Basing on the material emission data obtained in a test chamber, chemical mass balance (CMB) was used to assess the source apportionment of volatile organic compound (VOC) concentrations in three newly built timber frame houses. CMB has been proven to be able to discriminate the source contributions for two contrasted environmental conditions (with and without ventilation). The shutdown of the ventilation system caused an increase in the VOC concentrations due to the increased contribution of indoor surface materials like the door material and furniture explaining together over 65% of total VOCs. While the increase in formaldehyde concentration is mainly due to furniture (contribution of 70%), the increase in α-pinene concentration is almost exclusively attributable to the emission of door material (up to 84%). The apportionment of VOC source contributions appears as highly dependent on the position of source materials in the building (surface materials or internal materials) and the ventilation conditions explaining that the concentrations of compounds after the shutdown of ventilation system do not increase in equivalent proportion. Knowledge of indoor sources and its contributions in real conditions may help in the selection of materials and in the improvement of construction operations to reduce the indoor air pollution.     

Characterization of Volatile Organic Chemical Emissions From Carpet Cushions

Abstract

The U.S. Consumer Product Safety Commission is investigating chemical emissions from carpet systems in order to determine whether the emissions may be responsible for the numerous health complaints associated with carpet installation. As part of this effort, a study was conducted to identify and quantify volatile organic compounds (VOCs) released into the air by five major product types of new carpet cushions. Cushion samples were tested in small-volume dynamic chambers over a six-hour exposure period. Airborne VOCs collected on multisorbent samplers were identified using sensitive gas chromatography/mass spectrometry. The emissions of selected VOCs were quantitated with the small-scale chamber method and further characterized in larger environmental chambers conducted over a 96-hour period under conditions more representative of indoor environments. A separate chamber method was developed to screen polyurethane cushions for emissions of toluene diisocyanates (TDI). Over 100 VOCs, spanning a broad range of chemical classes, were emitted from 17 carpet cushions. The pattern of emitted VOCs varied between and among product types, which reflects probable differences in manufacturing processes and ingredients. No significant quantities of TDI or formaldehyde were released by any cushions. Emission profiles were characterized for total VOCs and for the predominant individual VOCs. As a group, the synthetic fiber cushion samples emitted the lowest quantities of VOCs. Cushion samples purchased from carpet retailers released lesser amounts of VOCs than samples of the same cushion types obtained directly from the manufacturing mills, suggesting that chemical losses from the bulk material may ensue as a result of transport, handling, and storage prior to installation. The data suggest that placement of carpet on top of a carpet cushion, as would occur in a residential installation, reduced the rate of some VOC emissions when compared to the cushion alone.     

Sensory and chemical characterization of VOC emissions from building products: impact of concentration and air velocity

The emissions from five commonly used building products were studied in small-scale test chambers over a period of 50 days. The odor intensity was assessed by a sensory panel and the concentrations of selected volatile organic compounds (VOCs) of concern for the indoor air quality were measured. The building products were three floor coverings: PVC, floor varnish on beechwood parquet and nylon carpet on a latex foam backing; an acrylic sealant, and a waterborne wall paint on gypsum board. The impacts of the VOC concentration in the air and the air velocity over the building products on the odor intensity and on the emission rate of VOCs were studied. The emission from each building product was studied under two or three different area-specific ventilation rates, i.e. different ratios of ventilation rate of the test chamber and building product area in the test chamber. The air velocity over the building product samples was adjusted to different levels between 0.1 and 0.3 m s^-1. The origin of the emitted VOCs was assessed in order to distinguish between primary and secondary emissions. The results show that it is reasonable after an initial period of up to 14 days to consider the emission rate of VOCs of primary origin from most building products as being independent of the concentration and of the air velocity. However, if the building product surface is sensitive to oxidative degradation, increased air velocity may result in increased secondary emissions. The odor intensity of the emissions from the building products only decayed modestly over time. Consequently, it is recommended to use building products which have a low impact on the perceived air quality from the moment they are applied. The odor indices (i.e. concentration divided by odor threshold) of primary VOCs decayed markedly faster than the corresponding odor intensities. This indicates that the secondary emissions rather than the primary emissions, are likely to affect the perceived air quality in the long run. Some of the building products continued to affect the perceived air quality despite the concentrations of the selected VOCs resulted in odor indices less than 0.1. Therefore, odor indices less than 0.1 as an accept criterion cannot guarantee that a building product has no impact on the perceived air quality.     

Destruction of Volatile Organic Compounds Using Catalytic Oxidation

Catalytic oxidation is an air pollution control technique in which volatile organic compounds (VOCs) and vapor-phase air toxics in an air emission stream are oxidized with the help of a catalyst Design of catalytic systems for control of point source emissions is based on stream-specific characteristics and desired control efficiency. This paper discusses the key emission stream characteristics and VOC characteristics that affect the applicability of catalytic oxidation. The application of catalytic oxidation technology to four types of air emission sources is discussed: (1) groundwater stripping operations; (2) graphic arts facilities; (3) flexographic printing plants; and (4) latex monomer production. The characteristics of each of these emissions are discussed along with the catalytic technology used to control these emissions.     

Using fugacity to predict volatile emissions from layered materials with a clay/polymer diffusion barrier

Structural insulated panels (SIPs) have significant environmental and energy advantages. However, the tight structure that results may cause degraded indoor air quality and the potential release of volatile organic compounds (VOCs) from these layered materials must be considered. A physically based model for predicting VOC emissions from multi-layer materials is described. Fugacity is used to eliminate the concentration discontinuities at the interface between layers. This avoids an obstacle associated with numerically simulating mass transfer in composite materials. The numerical model is verified for a double-layer system by comparing predicted concentrations to those obtained with a previously published analytical model. In addition, hexanal emissions from multi-layer SIPs are simulated to demonstrate the usefulness of the fugacity approach. Finally, the multi-layer model is used to investigate the impact that clay/polyurethane nanocomposite diffusion barriers can have on VOC emissions. Indoor gas-phase concentrations can be greatly reduced with a barrier layer on the surface, thereby minimizing the environmental impact of SIPs.     

Estimation of the rate of VOC emissions from solvent-based indoor coating materials based on product formulation

Two computational methods are proposed for estimation of the emission rate of volatile organic compounds (VOCs) from solvent-based indoor coating materials based on the knowledge of product formulation. The first method utilizes two previously developed mass transfer models with two key parameters – the total vapor pressure and the average molecular weight for total volatile organic compounds (TVOCs) – being estimated based on the VOC contents in the product. The second method is based on a simple, first-order decay model with its parameters being estimated from the properties of both the source and the environment. All the model parameters can be readily obtained. Detailed procedures for computing the key parameters are described by using examples. The predictive errors were evaluated with small chamber data, and the results were satisfactory. Thus, the proposed methods provide a way to predict the VOC emissions in the indoor environment without having to conduct costly chamber testing. The two proposed methods work for both TVOCs and individual VOCs. Pros and cons for each method are discussed.     

VOC source identification from personal and residential indoor,outdoor and workplace microenvironment samples in EXPOLIS-Helsinki,Finland

Principal component analyses (varimax rotation) were used to identify common sources of 30 target volatile organic compounds (VOCs) in residential outdoor, residential indoor and workplace microenvironment and personal 48-h exposure samples, as a component of the EXPOLIS-Helsinki study. Variability in VOC concentrations in residential outdoor microenvironments was dominated by compounds associated with long-range transport of pollutants, followed by traffic emissions, emissions from trees and product emissions. Variability in VOC concentrations in environmental tobacco smoke (ETS) free residential indoor environments was dominated by compounds associated with indoor cleaning products, followed by compounds associated with traffic emissions, long-range transport of pollutants and product emissions. Median indoor/outdoor ratios for compounds typically associated with traffic emissions and long-range transport of pollutants exceeded 1, in some cases quite considerably, indicating substantial indoor source contributions. Changes in the median indoor/outdoor ratios during different seasons reflected different seasonal ventilation patterns as increased ventilation led to dilution of those VOC compounds in the indoor environment that had indoor sources. Variability in workplace VOC concentrations was dominated by compounds associated with traffic emissions followed by product emissions, long-range transport and air fresheners. Variability in VOC concentrations in ETS free personal exposure samples was dominated by compounds associated with traffic emissions, followed by long-range transport, cleaning products and product emissions. VOC sources in personal exposure samples reflected the times spent in different microenvironments, and personal exposure samples were not adequately represented by any one microenvironment, demonstrating the need for personal exposure sampling.     

Investigation of the Treatability of the Primary Indoor Volatile Organic Compounds on Activated Carbon Fiber Cloths at Typical Indoor Concentrations

Abstract

Volatile organic compounds (VOCs) are a major concern for indoor air pollution because of the impacts on human health. In recent years, interest has increased in the development and design of activated carbon filters for removing VOCs from indoor air. Although extensive information is available on sources, concentrations, and types of indoor VOCs, there is little or no information on the performance of indoor air adsorption systems for removing low concentrations of primary VOCs. Filter designs need to consider various factors such as empty bed contact time, humidity effects, competitive adsorption, and feed concentration variations, whereas adsorption capacities of the indoor VOCs at the indoor concentration levels are important parameters for filter design. A preliminary assessment of the feasibility of using adsorption filters to remove low concentrations of primary VOCs can be performed. This work relates the information (including VOC classes in indoor air, the typical indoor concentrations, and the adsorption isotherms) with the design of a particular adsorbent/adsorbates system. As groundwork for filter design and development, this study selects the primary VOCs in indoor air of residences, schools, and offices in different geographical areas (North America, Europe, and Asia) on the basis of occurrence, concentrations, and health effects. Activated carbon fiber cloths (ACFCs) are chosen as the adsorbents of interest. It is demonstrated that the isotherm of a VOC (e.g., toluene on the ACFC) at typical indoor concentrations—parts per billion by volume (ppbv) level—is different than the isotherm at parts per million by volume (ppmv) levels reported in the publications. The isotherms at the typical indoor concentrations for the selected primary VOCs are estimated using the Dubinin–Radushkevitch equation. The maximum specific throughput for an indoor VOC removal system to remove benzene is calculated as a worst-case scenario. It is shown that VOC adsorption capacity is an important indicator of a filter’s lifetime and needs to be studied at the appropriate concentration range. Future work requires better understanding of the realistic VOC concentrations and isotherms in indoor environments to efficiently utilize adsorbents.     

Emission of non-methane volatile organic compounds (VOCs) from boreal peatland microcosms—effects of ozone exposure

Non-methane volatile organic compounds (VOCs) emitted from boreal peatland microcosms were semiquantitatively determined using gas chromatography–mass spectrometry techniques in a growth chamber experiment. Furthermore, effects of vegetation composition and different ozone concentrations on these emissions were estimated by multivariate data analyses. The study concentrated on the less-studied VOCs, and isoprene was not analyzed. The analyses suggest that a sedge Eriophorum vaginatum is associated with emissions of the four most-emitted VOC groups (cyclic, aromatic, carbonyl and aliphatic hydrocarbon compounds) and also with VOCs emitted in smaller amounts (terpenoids and N-containing compounds). A woody dwarf shrub Andromeda polifolia was strongly associated with emissions of aromatic, carbonyl and terpenoid compounds. Results suggest that exposure to an ozone concentration of 150 ppb leads to an increased emission of most VOC groups. Emission of aromatic compounds seems to increase linearly with increasing ozone concentration. These observations indicate that peatlands may be a source of a vast range of volatile compounds to the atmosphere. For more accurate assessment of the impact of elevated tropospheric ozone on the terpenoid and non-terpenoid VOC emissions from peatlands, well-replicated open-air ozone-exposure experiments should be conducted.     

The emission patterns of volatile organic compounds during aerobic biotreatment of municipal solid waste using continuous and intermittent aeration

Because volatile organic compounds (VOCs) are one of the main concerns during municipal solid waste (MSW) treatment, the release patterns and the environmental effects of VOCs were investigated during laboratory-scale aerobic biotreatments of MSW with continuous and intermittent negative ventilation. When the same airflow amounts were used, intermittent ventilation was found to reduce the total VOC emissions from continuous ventilation process by 28%. In this study, 23 types of volatile organic compounds were analyzed, of which butyraldehyde, ethanol, and butanone were emitted in the highest concentrations of 748, 372, and 260 mg/m3, respectively. During the aerobic biotreatment process, ketones, aldehydes, and alcohols were primarily released during the first 4 days, accounting for 86-98% of the total VOC emissions during this period. The emission concentrations of malodorous sulfide compounds displayed two peaks on day 4 and day 9, with the contribution to the total VOC emissions being enhanced from less than 10% to 76-83%. The release of terpenes and aromatics lasted for more than 10 days with no significant emission peaks and the proportions of those compounds in the total VOCs increased gradually, but no more than 50% even at the end of the process. Considering the strength of the odors, aldehydes were the predominant contributors at the beginning of the experiment, whereas malodorous sulfide compounds became the most odorous compound as the biological process continued. Most of the VOCs emitted at the concentrations beneath the level causing health threat to the workers.     

Temperature and air velocity effects on ethanol emission from corn silage with the characteristics of an exposed silo face

Volatile organic compounds (VOCs) from agricultural sources are believed to be an important contributor to tropospheric ozone in some locations. Recent research suggests that silage is a major source of VOCs emitted from agriculture, but only limited data exist on silage emissions. Ethanol is the most abundant VOC emitted from corn silage; therefore, ethanol was used as a representative compound to characterize the pattern of emission over time and to quantify the effect of air velocity and temperature on emission rate. Ethanol emission was measured from corn silage samples removed intact from a bunker silo. Emission rate was monitored over 12 h for a range in air velocity (0.05, 0.5, and 5 m s^?1) and temperature (5, 20, and 35 °C) using a wind tunnel system. Ethanol flux ranged from 0.47 to 210 g m^?2 h^?1 and 12 h cumulative emission ranged from 8.5 to 260 g m^?2. Ethanol flux was highly dependent on exposure time, declining rapidly over the first hour and then continuing to decline more slowly over the duration of the 12 h trials. The 12 h cumulative emission increased by a factor of three with a 30 °C increase in temperature and by a factor of nine with a 100-fold increase in air velocity. Effects of air velocity, temperature, and air-filled porosity were generally consistent with a conceptual model of VOC emission from silage. Exposure duration, temperature, and air velocity should be taken into consideration when measuring emission rates of VOCs from silage, so emission rate data obtained from studies that utilize low air flow methods are not likely representative of field conditions.     

Characterization of Emissions of Volatile Organic Compounds from Interior Alkyd Paint

ABSTRACT

Alkyd paint continues to be used indoors for application to wood trim, cabinet surfaces, and some kitchen and bathroom walls. Alkyd paint may represent a significant source of volatile organic compounds (VOCs) indoors because of the frequency of use and amount of surface painted. The U.S. Environmental Protection Agency (EPA) is conducting research to characterize VOC emissions from paint and to develop source emission models that can be used for exposure assessment and risk management. The technical approach for this research involves both analysis of the liquid paint to identify and quantify the VOC contents and dynamic small chamber emissions tests to characterize the VOC emissions after application. The predominant constituents of the primer and two alkyd paints selected for testing were straight-chain alkanes (C9–C12); C8–C9 aromatics were minor constituents. Branched chain alkanes were the predominant VOCs in a third paint. A series of tests were performed to evaluate factors that may affect emissions following application of the coatings. The type of substrate (glass, wallboard, or pine board) did not have a substantial impact on the emissions with respect to peak concentrations, the emissions profile, or the amount of VOC mass emitted from the paint. Peak concentrations of total volatile organic compounds (TVOCs) as high as 10,000 mg/m³ were measured during small chamber emissions tests at 0.5 air exchanges per hour (ACH). Over 90% of the VOCs were emitted from the primer and paints during the first 10 hr following application. Emissions were similar from paint applied to bare pine board, a primed board, or a board previously painted with the same paint. The impact of other variables, including film thickness, air velocity at the surface, and air-exchange rate (AER) were consistent with theoretical predictions for gas-phase, mass transfer-controlled emissions. In addition to the alkanes and aromatics, aldehydes were detected in the emissions during paint drying. Hexanal, the predominant aldehyde in the emissions, was not detected in the liquid paint and was apparently an oxidation product formed during drying. This paper summarizes the results of the product analyses and a series of small chamber emissions tests. It also describes the use of a mass balance approach to evaluate the impact of test variables and to assess the quality of the emissions data.     

Comparison of VOC emissions between air-dried and heat-treated Norway spruce (Picea abies), Scots pine (Pinus sylvesteris) and European aspen (Populus tremula) wood

Heat-treated wood is an increasingly popular decoration material. Heat-treatment improves dimensional stability of the wood and also prevents rot fungus growth. Although production of heat-treated wood has been rapidly increasing, there is only little information about the VOC emissions of heat-treated wood and its possible influences on indoor air quality. In the present study, VOC emissions from three untreated (air-dried) and heat-treated wood species were compared during a four weeks test period. It appeared that different wood species had clearly different VOC emission profiles. Heat-treatment was found to decrease VOC emissions significantly and change their composition. Especially, emissions of terpenes decreased from softwood samples and aldehydes from European aspen samples. Emissions of total aldehydes and organic acids were at the same level or slightly higher from heat treated than air-dried softwood samples. In agreement with another recent study, the emissions of furfural were found to increase and those of hexanal to decrease from all the wood species investigated. In contrast to air-dried wood samples, emissions of VOCs were almost in steady state from heat treated wood samples even in the beginning of the test.     

A New Method for the Rapid Determination of Volatile Organic Compound Breakthrough Times for a Sorbent at Concentrations Relevant to Indoor Air Quality

Abstract

The use of sorbents has been proposed to remove volatile organic compounds (VOCs) present in ambient air at concentrations in the parts-per-billion (ppb) range, which is typical of indoor air quality applications. Sorbent materials, such as granular activated carbon and molecular sieves, are used to remove VOCs from gas streams in industrial applications, where VOC concentrations are typically in the parts-per-million range. A method for evaluating the VOC removal performance of sorbent materials using toluene concentrations in the ppb range is described. Breakthrough times for toluene at concentrations from 2 to 7500 ppb are presented for a hydrophobic molecular sieve at 25% relative humidity. By increasing the ratio of challenge gas flow rate to the mass of the sorbent bed and decreasing both the mass of sorbent in the bed and the sorbent particle size, this method reduces the required experimental times by a factor of up to several hundred compared with the proposed American Society of Heating, Refrigerating, and Air-Conditioning Engineers method, ASHRAE 145P, making sorbent performance evaluation for ppb-range VOC removal more convenient. The method can be applied to screen sorbent materials for application in the removal of VOCs from indoor air.