lnside samplers: the odd behavior of SVOC aerosols

Assessing the exposure of workers to semi-volatile organic compound (SVOC) aerosols generally involves sampling an unstable diphasic chemical agent on a filter and a sorbent in series. Experiments at a macroscopic scale demonstrated that the behavior of any liquid SVOC aerosol collected could be modeled if the mass of compound collected on the filter was sufficient to produce saturated vapors downstream. If this was not the case, the theory failed to describe the evaporation behavior. Unfortunately, during persona! sampling for exposure assessment, the masses collected on sampling deviees rarely produce saturated vapors downstream.

To understand where the gap between the theory and the experimental data originate, droplets of collected SVOC were observed under a microscope. A specifie behavior was noted which cannat be explained by the diffusion theory generally used to madel evaporation. Comprehending evaporation behavior remains within the scope of our research because we believe that it is the key to understanding the gap between theory and experimentation at microscopie and macroscopic scales. Information on evaporation behavior is also essential when calculating the corrected quantities of particulate and vapor phases after sampling.

However, even if this madel has yet to be developed, these observations have allowed us to draw useful conclusions asto how a semi-volatile compound should be defined, how a compound in the workplace can be identified, and how to deal with the sampler, the analytical method and the results. Sorne of these conclusions have already been included in a CEN standard: EN 13936.