The efficiency of sandblasters' hoods in the prevention of silica exposure

This study evaluates the efficiency of abrasive blasting hoods in protecting sandblasters on two different Los Angeles Jobs (A and B) from crystalline silica exposure greater than the federal standard. Respirable, breathing zone air samples were taken outside and inside each hood in April, 1977 on Job A and between August and December, 1978 on Job B. Air samples were taken using portable pumps and PVC filters. The results of this study showed that the exposures were negligible since none of the samples collected inside the hoods had sufficient mass for X-ray diffraction analysis. According to the Occupational Exposure to Crystalline Silica [17] definition of “exposure to free silica,” the sandblaster on Job A was experiencing exposure to free silica outside his hood during this study, but the sandblasters and workers on Job B were not. The sampling results on Job A outside the hood were greater than the recommended half level indicating “exposure to free silica.” All samples collected outside the hoods were less than ten times the calculated or hypothetical threshold limit standards. All the hoods tested were effective in reducing the respirable free silica quantity outside the hoods to a quantity inside the hoods that was less than the accuracy of the electrobalance.