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Source Characterization Abstracts
Abstract
The sink strength of two common indoor materials, a carpet and a gypsum board, was evaluated by environmental chamber tests with four volatile organic compounds (VOCs): propylene glycol, ethylene glycol, 2-(2-butoxyethoxy)ethanol (BEE), and Texanol. These oxygenated compounds represent the major VOCs emitted from a latex paint. Each chamber test included two phases. Phase 1 was the dosing/sorption period during which sink materials (pieces of carpet and gypsum board samples) were exposed to the four VOCs. The sink strength of each material tested was characterized by the amount of the VOCs adsorbed or absorbed. Phase 2 was the purging/desorption period during which the chambers with the dosed sink materials were flushed with purified air. The reemission rates of the adsorbed VOCs from the sinks were reflected by the amount of the VOCs being flushed. Phase 1 results indicated that the sink strength measured was more than 1 order-of-magnitude higher than that for other VOCs previously tested by EPA. The high sink strength reflected the unusually high sorption capacity of common indoor materials for the four VOCs. Phase 2 results showed that reemission was an extremely slow process. If all the VOCs adsorbed were reemittable, it would take more than a year to completely flush out the VOCs from the sink materials tested. The long reemission process can result in chronic and low level exposure to the VOCs after painting interior walls and surfaces.
Abstract
The effects of two substrates — a stainless steel plate and a gypsum board — on the volatile organic compound (VOC) emissions from a latex paint were evaluated by environmental chamber tests. It was found that the amount of VOCs emitted from the painted stainless steel was 2 to 10 times more than that from the painted gypsum board during the 2-week test period. The dominant chemical species emitted were also different between the two substrates. Data analysis indicated that most VOC emissions from the painted stainless steel occurred in the first 100 h via a fast, evaporation-like process. On the other hand, the majority of the gypsum board VOCs were emitted in a later stage via a slow, diffusion-controlled process. There were measurable emissions of VOCs 11 month after paint application on the gypsum board. It is suggested that, instead of the routinely used substrates such as stainless steel plates, real substrates such as wood or gypsum board should be used for evaluation of emissions in indoor environments.
Abstract
Latex paint (interior, water-based) is being evaluated as a source of indoor air pollution. The Indoor Air Branch of EPA's Air and Energy Engineering Research Laboratory, Research Triangle Park, NC, is using a three phase approach (i.e., small chamber source characterization - IAQ (indoor air quality) modeling - test house validation) for this effort. A three part study is underway: 1) Initial Assessment; 2) Static and Dynamic Chamber Testing; 3) Test House Validation Studies. The initial assessment determined the most appropriate techniques for conducting the overall latex paint assessment program, including: a) selection and purchase of test paint; b) analysis of VOC (volatile organic compounds) and water content using ASTM methods; c) determination of major organic compounds; d) development of optimal sampling and analysis methods for organic paint emissions; e) evaluation of paint application methods; and f) selection of substrate. The purpose of the static and dynamic chamber testing is to develop data for determining VOC emission rates and for developing, evaluating, and validating source emission models, including mass transfer models. The test house validation studies will develop data for evaluating and validating source emission models, including mass transfer models. In addition, the studies should provide data for assessing scale-up of small chamber source emissions data. The following information is expected to result from this assessment of latex paint: a) Emission rate data for VOCs from latex paint on gypsumboard for specific test parameters; b) Validated source emissions models for latex paint, including mass transfer models; c) test house data showing the concentrations of VOCs from latex paint.
Abstract
Latex paint (interior, water based) is being evaluated as a source of indoor pollution by the Indoor Air Branch of EPA's Air Pollution Prevention and Control Division, Research Triangle Park, NC. A major objective of the research is the development of methods for predicting emissions of volatile organic compounds (VOCs) over time. Test specimens of painted gypsumboard are placed in dynamic flow-through test chambers. Samples of the outlet air are collected on Tenax®TA sorbents and thermally desorbed for analysis by gas chromatography/flame ionization detection (GC/FID). These tests produce short and long term data for latex paint emissions of Texanol®, 2-(2-butoxyethoxy)-ethanol, and glycols.
Evaluation of the data shows that most of the Texanol® emissions occur within the first few days, and emissions of the glycols occur over several months. This behavior may be described by an evaporative mass transfer process that dominates the short term emissions, while long term emissions are limited by diffusion processes within the dry paint-gypsumboard.
Abstract
A series of tests was designed to evaluate the performance of the Field and Laboratory Emission Cell (FLEC) as applied to the testing of emissions from two indoor coating materials, floor wax and latex paint. These tests included validation of the repeatability of the test method, evaluation of the effect of different air velocities on source emissions, and a comparison of FLEC versus small chamber characterization of emissions.
The FLEC exhibited good repeatability in characterization of emissions when applied to both sources under identical conditions. Tests with different air velocities showed significant effects on the emissions from latex paint, yet little effect on emissions from floor wax. Comparisons of data from the FLEC and a 53 liter dynamic chamber show good correlation for measurements involving floor wax, but less favorable results for emissions from latex paint. The procedures and findings are discussed. Conclusions are limited and include emphasis on the need for additional study and the development of a standard method.
Abstract
Aldehyde emissions are widely held responsible for the acrid after-odor of drying alkyd-based paint films. The aldehyde emissions from three different alkyd paints were measured in small environmental chambers. It was found that, for each gram of alkyd paint applied, more than 2 mg of aldehydes (mainly hexanal) were emitted during the curing (drying) period. Since no measurable hexanal was found in the original paint, it is suspected that the aldehydes emitted were produced by autoxidation of the unsaturated fatty acid esters in the alkyd resins. The hexanal emission rate was simulated by a model assuming that the autoxidation process was controlled by a consecutive first-order reaction mechanism. Using the emission rate model, indoor air quality simulation indicated that the hexanal emissions can result in prolonged (several days) exposure risk to occupants. The occupant exposure to aldehydes emitted from alkyd paint also could cause sensory irritation and other health concerns.
Abstract
Small environmental chamber tests were conducted to characterize the emissions of a toxic chemical compound – methyl ethyl ketoxime (MEKO) – from three different alkyd paints. It was found that MEKO emissions occurred almost immediately after each alkyd paint was applied to a pine board. Due to the fast emission pattern, more than 90% of the MEKO emitted was released within 10 hours after painting. The peak concentrations of MEKO in chamber air correlated well with the MEKO content in the paint. Material balance showed that good recovery (more than 68%) was achieved between the MEKO applied with the paint and the MEKO emitted. The chamber data were simulated by a first order decay emission model assuming the MEKO emissions were mostly gas-phase mass transfer controlled. The model was used to predict indoor MEKO concentrations during and after painting in a test house. It was found that the predicted test house MEKO concentrations during and after the painting exceeded a suggested indoor exposure limit of 0.1 mg/m3 for all three paints. The predicted MEKO concentrations exceeded even the lower limit of a suggested sensory irritation range of 4 to 18 mg/m3 with two of the three paints tested. The model was also used to evaluate and demonstrate the effectiveness of risk reduction options including selection of lower MEKO paints and higher ventilation during painting.