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 how to fully and properly use a commercially-available shroud and a dust collection system to control dust when using a handheld grinder to remove mortar that contains crystalline silica.
The process of removing and replacing mortar is commonly called tuckpointing.
EDITOR'S NOTE: the process of removing and replacing mortar between bricks is NOT called tuckpointing, but it commonly thought to be called that. It is actually called repointing. Tuckpointing refers to decorative mortar enhancement, as explained in this building science podcast with engineer Sarah Gray.
A shroud and dust collection system can control dust created by handheld grinders used for repointing.
Use a shroud and a shop vac to suck up the dust
Commercially-produced shrouds and dust collection systems are readily available for use with handheld grinders.
To comply with Table 1, the dust collector must provide a minimum airflow of 25 cubic feet per minute 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 airflow through the dust collection system. It’s essential to maintain the dust collection system correctly.
When the dust collection system is not working properly, dust is not adequately 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.
Maintain dust collection equipment regularly
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 following the manufacturer’s instructions to minimize dust emissions.
Instructions often direct users to:
- 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 airflow and dust collection
- Clean and replace filters as needed
- Not overfill the waste container
- Follow a specified maintenance schedule
Be sure that used filters and dust collection bags are handled in a manner that will minimize workers’ exposure to silica dust.
If the task is performed for four hours or fewer during a shift, the tool operator and workers assisting the operator must use respirators with an assigned protection factor of at least 10.
Wear a respirator anyway
If the task is performed for more than four hours, the tool operator and workers assisting the operator must use respirators with an assigned protection factor of at least 25.
The appropriate respirator must be put on before beginning the task and must be worn the entire time the job is performed.
Employers who perform repointing must comply with OSHA’s respiratory protection standard. Using a handheld grinder for repointing 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 accurately implement the dust control method specified 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 everyday construction tasks, can be found at www.osha.gov/silica