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The Occupational Safety and Health Administration requires employers to limit workers’
exposure to respirable crystalline silica on the job.
This is one of a series of videos showing dust control methods that OSHA specifies
for many common construction tasks in Table 1 of the Respirable Crystalline Silica Standard for Construction.
When used properly, these methods are effective in limiting workers’ exposure to respirable crystalline silica dust.
This video describes two methods that can be used to control dust when using handheld grinders on materials
that contain crystalline silica, specifically for uses other than mortar removal:
An integrated water delivery system, when grinders are used outdoors; Or,
A commercially-available shroud and dust collection system, when grinders are used outdoors,
indoors, or in an enclosed area.
First, let’s review the full and proper use of an integrated water delivery system when grinding outdoors.
Many handheld grinders have a built-in water delivery system that applies water to the grinding surface.
The application of the water can effectively control dust when grinding materials containing crystalline silica.
To comply with Table 1, the water delivery system must be integrated with the grinder
and must continuously feed water to the grinding surface.
An integrated water delivery system is one that was supplied by the equipment manufacturer
and developed to be used with the specific make and model of the tool.
An integrated water delivery system for a handheld grinder can be gravity-fed or pressurized.
It typically consists of a water source, hose, connections, and nozzle.
It’s important to correctly maintain the water delivery system.
When the water delivery system is not working properly, dust is not effectively controlled.
With regular use, hoses can become pinched, hose connections may fail,
and water reservoirs and nozzles can become clogged with debris.
When applying water to the grinding surface, the operator should also make sure
that the amount of water is sufficient to minimize the release of visible dust.
To make sure a continuous stream of water is delivered to the grinding surface,
operators should regularly check that the water supply is sufficient; check nozzles for damage;
remove clogs; and be sure the hoses and connections are intact and functioning correctly.
The grinder must be operated and maintained according to the manufacturer’s instructions to minimize dust emissions.
Instructions often specify the following:
The type and diameter of the grinding wheel;
The recommended amount of water to apply to the grinding surface;
Procedures for checking the grinding wheel for wear or damage; and
A maintenance schedule.
Any slurry produced should be cleaned up, to prevent the slurry from drying
and releasing silica dust into the air.
As long as the integrated water delivery system is fully and properly implemented on the handheld grinder
and used outdoors, the grinder operator, and workers who are assisting the grinder operator,
are not required to wear respirators.
Now let’s review the full and proper use of a commercially-available shroud
and dust collection system for use outdoors, indoors, or in an enclosed area.
A shroud and dust collection system can control dust created by the handheld grinder.
To comply with Table 1, the dust collector must provide at least 25 cubic feet per minute
of airflow for each inch of wheel diameter.
For example, if a grinding wheel is four inches in diameter,
then the dust collector must provide at least 100 cubic feet of airflow per minute.
The dust collector must also have a filter with 99 percent or greater efficiency
and a cyclonic pre-separator or filter-cleaning mechanism.
Cyclonic pre-separators and filter-cleaning mechanisms prevent debris from building up on the filter.
This allows more time between filter changes and helps maintain
the proper amount of air flow through the dust collection system.
It’s important to correctly maintain the dust collection system.
When the dust collection system is not working properly, dust is not effectively controlled.
With regular use, the shroud can become excessively worn,
vacuum hoses can become clogged, filters can become overloaded, and dust collection bags will fill up.
To help ensure the system is working correctly, the shroud must be intact
and installed according to the manufacturer’s instructions.
The grinder must also be operated and maintained in accordance
with the manufacturer’s instructions to minimize dust emissions.
Instructions often specify the following:
Regularly check the dust collection system for signs of damage,
Make sure the hose connecting the tool to the vacuum is intact and without kinks
or tight bends that can reduce air flow and dust collection,
Clean and replace filters as needed,
Do not overfill the waste container; and
Follow a maintenance schedule.
Be sure used filters and dust collection bags are handled in a manner
that will minimize workers’ exposure to silica dust.
As long as the commercially-available shroud and dust collection system is fully and properly implemented
on the handheld grinder, OSHA does not require the grinder operator,
and workers who are assisting the operator to wear a respirator,
unless the task is performed indoors or in an enclosed area for more than four hours during a shift.
If the task is performed indoors or in an enclosed area for more than four hours during a shift,
the tool operator, and workers assisting the operator, must use respirators
with an assigned protection factor of at least 10.
When respirators are required, they must be put on before beginning the task,
and must be worn the entire time the task is performed.
When respirators are used, the employer must comply with OSHA’s respiratory protection standard.
Using a handheld grinder indoors or in an enclosed area requires an exhaust method,
such as a portable fan, as needed to minimize the accumulation of visible airborne dust.
Be sure that any exhaust method chosen moves airborne dust away from workers and does not block an exit route.
Employers who fully and properly implement the appropriate dust control method specified by OSHA
in Table 1 are not required to measure the tool operator’s exposure to respirable crystalline silica,
or the exposure of other workers assisting with the task.
The respirable crystalline silica standard for construction also includes additional requirements
to protect workers exposed to respirable crystalline silica.
Many of these requirements apply whether employers are using a dust control method specified by OSHA
in Table 1, or an alternative dust control method.
More information on the standard’s requirements to protect workers exposed to respirable crystalline silica,
including information on specified exposure control methods for other common construction tasks,
can be found at www(dot)osha(dot)gov(slash)silica.
For information about other OSHA health and safety standards,
visit www(dot)osha(dot)gov or call OSHA at 1-800-321-OSHA.
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