CAN WE USE VOC DIFFUSION COEFFICIENTS IN AIR FOR ESTIMATING THE UPTAKE RATE OF PASSIVE VOC SAMPLERS FOR LARGE SCALE INDOOR AIR SURVEYS?

Currently, uptake rates of passive samplers have only been validated for a limited number of VOCs, and are largely for occupational settings (relatively short exposure times). According to Fick's First Law of Diffusion, the passive uptake rate of a chemical is proportional to its air diffusivity. Many vendors of the passive samplers also recommend the VOCS uptake rates based on air diffusivity. In this paper, we systematically evaluate the validity of using VOC air diffusion coefficients for estimating uptake rates of passive VOC samplers. Relationships between cited and calculated air diffusion coefficients, and between air diffusion coefficients and published VOC uptake rates in three commonly used commercial passive samplers were examined. Finally, for the Canadian national indoor air survey, uptake rates of target VOCs in Perkin-Elmer passive samplers with Carbopack B adsorbent were estimated using the above discussed relationship and reference chemicals whose uptake rates were experimentally determined.