Performance of the porton down charcoal cloth diffusive sampler

Abstract

The Porton Down diffusive sampler has been calibrated for eight organic vapours and the results were compared with theoretical calculations of the rate of diffusive uptake. Diffusive uptake by the sampler is affected by ambient air velocity below about 0.1 m s^–1, a value exceeded in most personal sampling situations, and also by the capacity of the charcoal cloth adsorbent. A procedure is described which estimates the time of onset of saturation under given conditions of vapour concentration and ambient humidity and the results are compared with laboratory calibrations of the samplers. Field trials confirmed that under appropriate conditions the Porton sampler gives valid results.