Abstract
Diffusive sampling is a cheap and simple method for measuring indoor air quality. The method requires a material sampling rate (SR) for each target pollutant. Usually, SRs are obtained from literature or a comparative experiment between active and passive sampling. However, the literature does not contain an SR for all compounds, and performing experiments to determine SRs can be burdensome. In this study, we tried to calculate SRs based on the diffusion theory, using the structure of samplers and material's physical properties. Nine types of diffusive sampler for volatile organic compounds (VOCs) marketed in Japan were examined. The SRs for benzene, toluene, and xylene were calculated using Fick's first law of diffusion. The diffusion area and length of each sampler were measured accurately using an electron microscope. The diffusion coefficient was calculated from the material's molecular structure using Fujita's Equation. The SRs were also determined experimentally with the vapor diffusion method, which can generate the reference gases stably. Each reference gas for VOCs with a given concentration was introduced into a 350 L chamber, and each sampler was exposed in the chamber over a designated period. The SRs derived based on the diffusion theory were almost the same as the experimental SRs for most samplers and for most substances. Thus, accurate calculation of SRs for VOCs based on the diffusion theory seems possible without the need to perform experimental measurements.
