Comprehensive Report: Laboratory Evaluation of Saw Blades for Cutting Fiber-Cement Siding

Details

• Personal Author:
  Kang, Seungkoo ; Qi, Chaolong
• Corporate Authors:
  National Institute for Occupational Safety and Health. Division of Applied Research and Technology
• Description:
  Workplace exposure to respirable crystalline silica (RCS) can cause silicosis, a progressive lung disease marked by scarring and thickening of the lung tissue. Quartz is the most common form of crystalline silica. Crystalline silica is found in several construction materials, such as brick, block, mortar, and concrete. Construction tasks that cut, break, grind, abrade, or drill those materials have been associated with overexposure to dust containing RCS. Fiber-cement products can contain as much as 50% crystalline silica and cutting this material has been shown to cause excessive exposures to RCS. NIOSH scientists conducted this study to evaluate different saw blades for cutting fiber-cement siding, aiming at identifying blade design features that lead to lower dust generation and releasing. Detailed characterizations of the dust generated from cutting fiber-cement siding using a circular saw with 22 different saw blades were conducted in a laboratory setting. The releasing rate of respirable dust, i.e., GAPS, was analyzed and compared with and without engineering control measures for each blade. Two passive control measures were specifically evaluated. First, a dust-collecting box with a capped exhaust port was attached to the circular saw. Second, the dust-collecting box was connected to a passive dust collector, which includes a cyclone and a filter cartridge. Both control measures help collect a portion of the dust by the induced airflow from the spinning blade. The GAPS generally increases with the number of teeth and the kerf width of the blades. The Plank Kutter blade, which has a continuous rim of blade tips, generated the highest amount of dust in all three test conditions. The effect of the number of blade teeth was reduced when the passive dust control measures were used, possibly because more teeth may induce a higher airflow rate and generate more dust. Excluding the Plank Kutter blade, the GAPS for the uncontrolled test condition ranges from 0.25 to 0.50 g/m, and reduces to 0.22-0.40 g/m with the capped dust-collecting box, and to 0.12-0.29 g/m when the passive dust collector was connected to the dust-collecting box. The 4-tooth Hitachi blade results in the lowest dust releasing rate under the testing conditions with both passive dust control measures, possibly due to fewer teeth, thinner kerf, and its specific design characteristics of a "smooth" gullet design for an optimized balance between inducing airflow and transporting the dust into the dust collectors. Both passive dust control measures led to certain amounts of dust collection for most of the tested blades. The control measure with the passive dust collector provided a dust collection efficiency as high as 66% depending on the blade design. The gullet design of the blade seems to play an important role affecting the amount of dust releasing as well as the collection efficiency of the passive dust controls. Based on the exposure data from previous field surveys, additional improvement in blade designs might reduce the 8-hour time weighted average exposure to RCS below the NIOSH REL and OSHA PEL while cutting fiber-cement siding using a circular saw with passive on-tool dust collectors. Further investigation will be needed to improve the blade design with the passive dust control measure, and to validate its performance through field studies.
• Subjects:
  Air Movements Construction Industry Construction Materials Dust Engineering Environmental Exposure Laboratories Occupational Health Particulate Matter Safety Silicon Dioxide

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• Keywords:
  Air Flow Cements Concretes Construction Construction Equipment Construction Materials Construction Workers Control Methods Control Technology Crystalline Silica Cutting Tools Dust Collection Dust Collectors Dust Control Dust Suppression Engineering Control Engineering Controls Equipment Design Equipment Testing Exposure Levels Exposure Limits Fiber-cement Fibers Laboratory Testing PELs Performance Tests Permissible Exposure Limits Power Tools Recommended Exposure Limits RELs Respirable Crystalline Silica Respirable Dust Saw Blade Silica Dusts Threshold Limit Values Time Weighted Average Exposure TLV

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• Series:
  Engineering and Physical Hazards Survey Reports
• DOI:
  https://doi.org/10.26616/NIOSHEPHB19114
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Genre:
  Field Study
• Place as Subject:
  Ohio ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DART - Division of Applied Research and Technology ; EPHB - Engineering and Physical Hazards Branch
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-29
• NIOSHTIC Number:
  nn:20057363
• NTIS Accession Number:
  PB2021-100210
• Citation:
  Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, EPHB 19-114, 2019 May ; :1-29
• CAS Registry Number:
  Quartz (SiO2) (CAS RN 14808-60-7)
• Federal Fiscal Year:
  2019
• Peer Reviewed:
  False
• NAICS and SIC Codes:
  238170 - Siding Contractors - (NAICS)
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:a3b43d35536157fc54388a1505101c1cf199617b7322a0d38edd49985008ff505f418a4750db27a13d5d982fd8e92d81c87a0e3269efd49aa23a65e31d46d057
• Download URL:
  https://stacks.cdc.gov/view/cdc/174845/cdc_174845_DS1.pdf
• File Type:
  [PDF - 919.33 KB ]