Effects of wind on the dust and benzene-soluble matter captured by a small sampler

When dust is collected by means of filter holders for industrial hygiene measurements, quite low winds can cause serious errors which are often completely ignored. Collection efficiencies are presented for a filter-holder dust sampler now being used for dust measurements at British coke ovens. When the holder faces the wind, efficiency initially increases with particle size to above 100 per cent, but above about 15 μm efficiency falls. It probably increases again at larger particle sizes. Efficiency rapidly falls with increasing particle size when the holder is side-on to the wind.

Dust measurements were made in a dusty place on a coke oven, with one sampler facing, and another side-on to, a 2·6 m s−1 wind. The ratio of the concentrations measured by the two samplers was about 4 for total dust, but only about 1·5 for the benzene-soluble matter (BSM), suggesting that the BSM was concentrated on the smaller particles. These ratios are probably overestimates of the normal sampling errors. The errors are clearly important, however, although less so than with more open filter holders.