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

UNLABELLED: 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.

Evaluation of VOC emission measurement methods for paint spray booths.

Interest in regulations to control solvent emissions from automotive painting systems is increasing, especially in ozone nonattainment areas. Therefore, an accurate measurement method for VOC emissions from paint spray booths used in the automotive industry is needed to ascertain the efficiency of the spray booth capture and the total emissions. This paper presents the results of a laboratory study evaluating potential VOC sampling and analytical methods used in estimating paint spray booth emissions, and discusses these results relative to other published data. Eight test methods were selected for evaluation. The accuracy of each sampling and analytical method was determined using test atmospheres of known concentration and composition that closely matched the actual exhaust air from paint spray booths. The solvent mixture to generate the test atmospheres contained a large proportion of polar, oxygenated hydrocarbons such as ketones and alcohols. A series of identical tests was performed for each sampling/analytical method with each test atmosphere to assess the precision of the methods. The study identified significant differences among the test methods in terms of accuracy, precision, cost, and complexity.