Abstract
Surface mine drill operators have the highest frequency of overexposure to quartz dust, and drilling is one of the occupations associated with the highest incidence of silicosis. Previous field assessment studies of drilling machines indicate that they can emit some of the highest airborne respirable quartz dust concentrations found at surface mining operations. Typically, the surface mine drills are equipped with dry dust collector systems to capture the dust being flushed with compressed air from the hole during the drilling process. The overall control effectiveness of the dust collector system is initially dependent on capturing the dust cloud at the source via the collector inlet. To assist the initial capture of the dust being flushed from the drill hole, the bottom of the drill deck is typically shrouded or enclosed on all sides to help contain the dust for the collector inlet plenum located on the underside perimeter of the drill deck. Openings, gaps, and breaches in the shroud enclosure permit dust to escape dust collector capture. NIOSH has developed a collector inlet hood that reconfigures the inlet plenum around the drill steel and above the hole to enhance dust capture. Lab development and testing show that this inlet hood improves dust capture by an average of nearly 50% over a wide range of collector flows and shroud leakage areas. This article describes the lab and subsequent field testing of this inlet hood concept.