Effect of Using a Cowl When Measuring the Fiber Number Concentration by the Membrane Filter Method

Abstract

This article compares samples taken with three different sampling heads: (1) open-faced sampling head, (2) open-faced sampling head with stainless-steel extension cowl, and (3) open-faced sampling head with graphite-impregnated extension cowl. Sampling was performed in three factories producing man-made mineral fibers (alkaline silicate fibers, refractory ceramic fibers, glass fibers). Flow rate was varied (1 L/min or 2 L/min). The average densities measured on the sampling filter for fibers of <3 μm in diameter varied from 19 to 91 fibers/mm 2 . No significant difference in fiber density was observed in relation to the nature of the sampling head for fibers with a diameter of <3 μm. The deposits noted on the internal walls of the cowl were small and much less than that documented in the literature for man-made mineral fibers until now. They were greater for fibers with a diameter of >3 μm than for those with a diameter of <3 μm. For large-diameter fibers, it would appear that cowl deposit can be reduced by increasing the sampling flow rate.