Other Considerations

Depending on the material, task, control selected, working conditions, weather, and location of the job there are other things you may need to address when putting together your silica exposure control plan.  The following are examples:

Using Water as a Control:

• Collect the water -- tools with water collection systems can help avoid creating wet, slippery ground and walking surfaces.  During cold weather a layer of ice can form on wet surfaces and increase the risk of slips and falls. Depending on the system, wet cutting can result in run-off that may need to be controlled.
• Remove silica-containing debris while wet to prevent the dust from becoming airborne and hazardous once dry.
• Avoid electric shocks when using an electric-powered tool with a water control by making sure that the electrical cords and extensions are rated for the tool's power requirements, regularly inspected, and used in combination with ground fault interrupt circuits.
• Factor in the impact of wet cutting on materials being used -- the time that may be required to allow masonry materials to dry after cutting and before use will depend on the material, the amount of water used, and the application. Concern that excess shrinkage as the units dry might lead to cracks has led some to prohibit wet cutting. The amount of water added to the unit during site cutting is insignificant, in terms of shrinkage. This was clarified in the ACI 530.01-05/ASCE6-05/TMS 602-05 Specification for Masonry Structures.

Using Vacuum Controls:

• Vacuum controls must be located as close to the dust generation as possible to be effective. A shroud may be needed to contain the dust so the vacuum can capture it. The shroud must be kept as close to the work surface as is practical to provide adequate dust capture. The shroud should be connected to the vacuum with 2-inch, or greater, diameter tubing with a relatively smooth interior.
• For dust containing silica, it is important to use as high efficiency filters as practical. The best available are called HEPA (High Efficiency Particle Air) filters because they capture 99.97% of the most penetrating particles. But HEPA filters also create a greater pressure drop and decrease in air flow rate because it is more difficult to pull air through these denser filters so capture velocity may be reduced. HEPAs require routine cleaning or disposal of prefilters, which can cause exposures to those performing the filter maintenance.
• For operations that generate large amounts of dust, cyclonic collection units may be a good option. These units spin the particles and drop them into cheap bags that do not need to be replaced as frequently as other types of vacuum bags because the vacuum pressure does not drop as the bags fill up.
• Vacuum performance must be monitored on a regular basis to ensure the control’s effectiveness. A vacuum with a pressure gauge allows for frequent and easy monitoring of air flow.
• Vacuums require an adequate power source -- large electric vacuums commonly require 20 amp electrical circuits in addition to the power required for the tool.

Other issues:

• Avoid using gasoline-powered equipment in areas without adequate ventilation or confined spaces to prevent carbon monoxide poisoning.  When using gas-powered equipment, small, inexpensive personal monitors can be worn by the operator to warn of unacceptable exposures.
• Monitor noise levels and ensure workers use hearing protection. Equipment-control combinations may generate sound levels that are greater than 90 decibels, the OSHA Permissible Exposure Limit (PEL).  The NIOSH "Buy-Quiet" website provides helpful information on available tools and noise levels.