Measurement of vapour-aerosol mixtures

Abstract

A particular problem in connection with the measurement of hazardous substances is posed by substances or groups of substances which may occur simultaneously in vapour and aerosol form. It is possible that, during sampling, the distribution of the two phases on the sampling medium is subject to changes due to vaporisation of aerosol or condensation of vapour. For workplace assessment purposes, it makes sense to consider the sum of vapour and aerosol, which never changes. Only then can the results of different sampling systems be compared. There are several ways in which vapour-aerosol mixtures can be sampled. Combining adsorption tubes or denuders with filters is the most important. Twofold requirements must be considered in the development of such sampling methods: those applying to sampling systems for aerosols as well as those for vapour sampling systems. To satisfy the requirements resulting from these substances and groups of substances, BIA's personal sampling system (PGP) was extended. In addition to the sampling head for inhalable dust (GSP), originally designed for a flow rate of 3.5 L min ^–1 , sampling heads for 0.5, 1 and 10 L min ^–1 were developed. Tests were conducted on these sampling heads, which all showed compliance with the requirements defined for inhalable fraction sampling. For the combined sampling of aerosol and vapour, a system was created which allows a filter and up to three usual adsorption tubes to be loaded simultaneously. The measuring methods for alkanolamines, inorganic acids and explosives are described to illustrate the use of the above PGP extensions and the framework conditions, account of which must be taken in the sample treatment.