Development of impactor size-selective dust samplers at the Elliot Lake Laboratory.

The Elliot Lake Laboratory designs and uses impactor size selectors for respirable and other dust samplers both in the laboratory and in mines. Advantages of the selectors are compact size, reproducibility of size-selection performance based on the high precision of drill manufacture and use, flexibility in design and layout, and manufacturing ease in a machine shop. The major problems in design and performance were secondary deposition of dust and overloading with coarse dust. Secondary deposition modified the calculated size selection and either limited the spacing between adjacent orifices or orifices and other features or required a final calibration. Overloading of the coarse dust deposition zone led to changes in size-selection characteristics as the dust load increased, giving a definite limit to acceptable dust collection quantities. The use of multiple stages increased the coarse dust-holding capability manyfold. All the dust samplers developed at the Elliot Lake Laboratory used two or more successive stages to increase dust-holding capacity.