Expert Services | Environmental Contamination | Risk Management | Third-Party Review

The United States Environmental Protection Agency is considering recommending longer-term sampling to achieve more accurate time-weighted-average detections for indoor air monitoring of volatile organic chemicals. The purpose of the research presented herein was to compare longer sampling times using passive diffusion samplers to the results from shorter-term testing periods using sorbent tubes and low-flow pumps (US EPA Method TO-17) at great frequency for trichloroethene (TCE) in indoor air. A controlled release of TCE in a large room allowed for over two-orders-of-magnitude daily concentration variability over the course of the two-week monitoring event. The daily concentration measurements by US EPA Method TO-17 and the passive diffusion samplers were performed in triplicate and had excellent reproducibility. The results of daily tests were averaged and compared with four passive diffusion devices exposed to indoor air for three, seven, ten, and fourteen days in accordance with ASTM D6196-02. A specific uptake rate for each of the passive devices at the four different time intervals and the statistical significance of the time-varying uptake rates were evaluated. The performance of each passive diffusion device was determined using a statistical performance criterion. The average concentration for all of the exposure periods could be reliably predicted using the established uptake rates for two of the four passive devices.

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