A portable instrument for respirable dust sampling

Abstract

Dust-laden air is drawn into the instrument, which is known as the long running thermal precipitator, by means of a clockwork-driven diaphragm pump. Passage through a horizontal elutriator removes all but the respirable fraction which is then deposited on a single horizontal microscope slide by a combination of gravity settlement and thermal precipitation. A single sample covers up to eight hours operation, giving a measure of average dustiness. Evaluation is normally by visual microscopy, but the method of collection employed provides a deposit particularly well suited to bulk evaluation techniques. The instrument is intrinsically safe for use in gassy coal-mines, self-contained, and simple to operate. Extended pit trials have proved it to be robust and reliable and to give results in agreement with those obtained by the conventional thermal precipitator.