Engineering Controls for Silica in Construction
Construction workers are potentially exposed to hazardous dust containing respirable crystalline silica (RCS) when using jackhammers to break concrete pavement. NIOSH found that such exposures could be reduced by using a water-spray attachment. This low-flow, water-spray control suppressed and reduced dust exposures by 70%–90%.
The Jackhammer without Engineering Controls video shows a worker breaking concrete with a jackhammer without any dust controls. The bar on the right shows the worker’s respirable dust exposure, which is elevated. The units are milligrams of dust per cubic meter of air.
NIOSH is not aware at this time of off-the-shelf, commercially available retrofit kits or jackhammers that come with built-in water-spray units. However, it is relatively simple to build a water-spray control for a jackhammer using the diagram below and the parts and instructions in Workplace Solution 2008-127. Plans for a simplified version are also available from a NIOSH partner.
The spray angle (the angle included between the sides of the cone formed by the water discharged by the nozzle) and the spray pattern are two critical design parameters required to match the performance of the tested device. The device tested used a solid-cone nozzle with an 80-degree spray angle. The third critical design parameter is the water flow rate. This spray used 350 milliliters (11.8 ounces) of water per minute for dust control. Higher water flow rates may not greatly improve dust control. Lower flow rates may not be as effective.
This Jackhammer with Engineering Controls video shows the same worker using a jackhammer with a water spray control attached. The bar on the right shows that the worker’s respirable dust exposure is much lower when the water spray is used.
For more information about dust controls for jackhammering see:
- Effectiveness of dust control by atomisation of water sprays on handheld demolition and soil compacting equipment.
Tijdschrift voor toegepaste Arbowetenschap: 2004 / 4:68-74.
- Control of respirable dust and crystalline silica from breaking concrete with a jackhammer.
Applied Occupational and Environmental Hygiene: 2003 / 18:491–495.
- In-depth survey report of a water spray device for suppressing respirable and crystalline silica dust from jackhammers at E.E. Cruz Company, South Plainfield, New Jersey
NIOSH Report No. EPHB 282-11c-2 (2004).
- Preliminary report on reduction of airborne dust produced by pneumatic jackhammers. American Industrial Hygiene Association Journal : 1967 / 28:479-481.
- Control of airborne dust produced by pneumatic jackpicks. II.
American Industrial Hygiene Association Journal : 1969 / 30:519-22.
- Control of airborne dust produced by pneumatic jackpicks with water attachments: report 3.
American Industrial Hygiene Association Journal : 1973 / 34:48-53.
- Control of airborne dust produced by pneumatic jackpicks. Report IV. Calibration of water attachments.
American Industrial Hygiene Association Journal : 1973 / 34:171-5.
- Airborne dust produced by pneumatic jackpick. V. Visible dust-steam clouds and concentrations.
American Industrial Hygiene Association Journal : 1974 / 35:433-7.
- Exposure assessment strategy for the reduction of airborne silica during jackhammering activities.
Orlando, FL: Presentation at AIHCE 2000.
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