In-Depth Survey Report: Control Technology for Dowel Drilling in Concrete.

摘要

NIOSH scientists are conducting a study to assess the effectiveness of dust control systems sold by dowel drill manufacturers by measuring exposures to workers operating dowel drills with and without dust controls installed. This site visit was part of that study. The dust control assessed at this site consisted of a hood surrounding the drill steel at the drilling surface, flexible duct, an air cleaner, and an air mover. NIOSH staff performed industrial hygiene sampling at the Laborer's Local 172 Safety, Education and Training Center in Folsom, New Jersey on August 7 and 8, 2012. The personal sampling measured exposures to respirable dust and crystalline silica among two laborer-instructors who took turns operating a dowel drill to drill holes in a new concrete slab. The NIOSH personnel who visited the site also monitored the weather, collected data (e.g., air flow, design) about the dust collection system and observed the work process in order to understand the conditions that led to the measured exposures. Results: The quartz content in the bulk samples ranged from 17 to 28 percent by weight, with an arithmetic mean quartz content of 22 percent. No respirable dust was detected on any of the personal samples. The minimum detectable concentration was 0.31mg/m3 in a 32 minute sample collected when 27 holes were drilled. Quartz was only detected in one air sample; 0.09 mg/m3 of quartz was found on an 8-minute sample collected during a drill maintenance task. The minimum detectable concentration for quartz in personal air samples collected while drilling was performed was 0.02 mg/m3. The average number of holes drilled during each drilling sample was 23. Over the course of the two day study, air flow measured at the dust collector fell from 2.2 m3/sec (76 cfm) to 1.8 m3/sec (62 cfm).