In-depth survey report: control technology for mine assay laboratories at Pinson Mine, Winnemucca, Nevada, report no. CT-198-11b.
A study was made to document and evaluate effective technologies for the control of potential health hazards at the assay laboratory of the Pinson Mine (SIC-8734), Winnemucca, Nevada. The mine was a gold and silver operation, employing 110 workers. Ten workers were employed in the assay laboratory on two shifts. The laboratory performed about 10,000 determinations per month, of which 2,500 to 3,000 were fire assay analyses. Workers were potentially exposed to lead (7439921), crystalline silica (14808607), respirable dust, mercury (7439976), and arsenic (7440382). Engineering controls in the mine assay laboratory consist of local exhaust ventilation and enclosures in the sample preparation area, a local exhaust ventilation hood over the flux mixing table, and local exhaust hoods over the furnace doors in the fire assay room. The premixed flux contained a mineral oil to help control lead dust during flux mixing. Half mask respirators were worn in the fire assay area and during flux mixing operations. The assayist's lead exposures were controlled to less than permissible levels. Arsenic (7440382) exposures were all less than one fiftieth of the permissible levels. All mercury levels were less than the permissible levels. Compressed air was used to clean dust off equipment and work surfaces. The authors recommend that the air hose pressure be lowered from 50 to 30 pounds per square inch. Workers in the fire assay area must take showers after work.