title: Evaluation of a Dust Control for a Small Slab-Riding Dowel Drill for Concrete Pavement.
abstract: OBJECTIVE
  To assess the effectiveness of local exhaust ventilation to control respirable crystalline silica exposures to acceptable levels during concrete dowel drilling.
  
  
  METHODS
  Personal breathing zone samples for respirable dust and crystalline silica were collected while laborers drilled holes 3.5 cm diameter by 36 cm deep in a concrete slab using a single-drill slab-riding dowel drill equipped with local exhaust ventilation. Data were collected on air flow, weather, and productivity.
  
  
  RESULTS
  All respirable dust samples were below the 90 µg detection limit which, when combined with the largest sample volume, resulted in a minimum detectable concentration of 0.31 mg m(-3). This occurred in a 32-min sample collected when 27 holes were drilled. Quartz was only detected in one air sample; 0.09 mg m(-3) of quartz was found on an 8-min 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 m(-3). The average number of holes drilled during each drilling sample was 23. Over the course of the 2-day study, air flow measured at the dust collector decreased from 2.2 to 1.7 m(3) s(-1).
  
  
  CONCLUSIONS
  The dust control performed well under the conditions of this test. The initial duct velocity with a clean filter was sufficient to prevent settling, but gradually fell below the recommended value to prevent dust from settling in the duct. The practice of raising the drill between each hole may have prevented the dust from settling in the duct. A slightly higher flow rate and an improved duct design would prevent settling without regard to the position of the drill.
authors.affiliation: Division of Applied Research and Technology, Engineering and Physical Hazards Branch, National Institute for Occupational Safety and Health, Cincinnati, OH, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Echt
authors.affiliation: Division of Applied Research and Technology, Engineering and Physical Hazards Branch, National Institute for Occupational Safety and Health, Cincinnati, OH, USA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Mead
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis*; D060389:Construction Industry; D003252:Construction Materials / Q000032:analysis; D004391:Dust / Q000032:analysis* / Q000517:prevention & control; D004784:Environmental Monitoring / Q000379:methods; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis / Q000517:prevention & control*; D016273:Occupational Exposure / Q000032:analysis / Q000517:prevention & control*; D011791:Quartz / Q000032:analysis; D012822:Silicon Dioxide / Q000032:analysis*; D014691:Ventilation / Q000379:methods / Q000592:standards*
chemical_list: D000395:Air Pollutants, Occupational; D004391:Dust; D011791:Quartz; D012822:Silicon Dioxide
keywords: concrete; drilling; respirable; silica; ventilation
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