The effectiveness of integrated dust extraction units on hammer drills

Drilling is a common task throughout various industry sectors. When holes are drilled in silica-containing materials such as concrete, brick, and stone, respirable dust containing respirable crystalline silica (RCS) can be generated. Prolonged exposure to RCS can lead to silicosis, lung cancer, chronic obstructive pulmonary disease. Current good control practice includes the application of local exhaust ventilation (LEV) directly to the drills. This is via an external extraction system fitted to a shroud which extracts the dust generated during drilling. For several years, integrated LEV has been available for drills. Integrated LEV offers advantages over external LEV by providing increased portability, interlocked control, reduced trip hazards and reduced costs. However, little is known regarding the control effectiveness of integrated systems. The capture efficiency of 4 different integrated extractors and 1 external extraction system for controlling dust was measured using a real time respirable dust monitor. Furthermore, for 1 drill personal air sampling was conducted to assess the exposure potential to respirable dust from drilling repeatedly into concrete over a 1-h period using no LEV, integrated LEV, and external LEV options. The capture efficiency for respirable dust for 4 integrated drill LEV units ranged between 98.6% and 99.6%. This was comparable to the respirable dust capture efficiency provided by a self-sealing shroud fitted to an external extraction unit which provided efficiencies between 99.4% and 99.8%. The personal exposure testing showed respirable dust exposure was reduced by 87.6% for integrated LEV and 93.3% for external LEV fitted with a self-sealing shroud. The reason for the lower efficiency for the integrated LEV was attributed to dust generated as their dust bins were emptied more often throughout the tests. Given the size of the integrated LEV dust bins and the frequency at which they may require emptying, appropriate control measures to protect workers from dust exposure should be considered-eg emptying the units outdoors in conjunction with RPE.