FIELD TRIALS OF AN ELECTRET-BASED PASSIVE DUST SAMPLER IN METAL-PROCESSING INDUSTRIES

A prototype passive dust sampler using an electret to capture dust particles has been designed on the basis of previous laboratory investigations. The device weighs 15 g whereas conventional samplers, which require a pump and a battery, can weigh more than 1 kg. The electret used in the sampler is the same size as a standard sampling filter and can, to a large extent, be analysed in the same way, though sample weights tend to be small. The device has potential as both a static sampler and a personal sampler. Personal samplers have been assessed by field trials involving a number of volunteers, each wearing a passive sampler and one or more conventional samplers. The industries chosen for the trials were a hard-metal factory, platinum processing works and iron foundries, five factories in all being included in the tests. Correlations between the results of the passive samplers and those obtained using conventional inhalable dust samplers were good in four cases. Quantitative estimates of dust concentration require the electrical mobility of the dust to be known; and values were consistently high when scaled with measurements of aerosol electrical mobility made on the same occasion using a miniaturized electret device. In the instance where the passive sampler data could be compared with respirable dust samples the correlation was not particularly good.