Dust control
What the silica table requires for this job
Preparing concrete generates respirable crystalline silica, and the federal construction standard publishes a table that says exactly which controls make a given task acceptable and when a respirator becomes mandatory. This page reads that table for the method you are using rather than offering general advice about wearing a mask.
Respiratory protection
None required by the table, provided the listed control is in place and working.
Table 1 item (xiii), walk-behind milling machines and floor grinders
What has to be in place for this row to apply
- A machine with the dust collection system its own manufacturer recommends, running at or above the manufacturer airflow.
- A collector filter of at least 99 percent efficiency, with a filter-cleaning mechanism.
- Indoors or in an enclosed area, a HEPA-filtered vacuum used to lift loose dust between passes.
What follows from the answer above
- This row requires no respirator at either shift length when the control is in place, which is the strongest argument in the standard for renting the machine with the extraction rather than without.
- Preparing 440 square feet is not a five-minute exposure. The shift length in this calculation is what decides whether a respirator is on the required list, so it is worth being honest about it.
- Concrete dust also destroys equipment. A shop vacuum without a proper filter and pre-separator becomes an aerosol generator, redistributing the fine fraction that matters.
The exact sentences this page is reading
These are the two rows of the federal table that cover floor preparation, quoted rather than paraphrased so you can check them against the source.
Dust collector must provide the air flow recommended by the manufacturer, or greater, and have a filter with 99% or greater efficiency and a filter-cleaning mechanism When used indoors or in an enclosed area, use a HEPA-filtered vacuum to remove loose dust in between passes
Dust collector must provide 25 cubic feet per minute (cfm) or greater of airflow per inch of wheel diameter and have a filter with 99% or greater efficiency and a cyclonic pre-separator or filter-cleaning mechanism
The employer shall ensure that no employee is exposed to an airborne concentration of respirable crystalline silica in excess of 50 μg/m 3 , calculated as an 8-hour TWA.
This standard binds employers. Read it anyway.
Grinding or shot-blasting concrete generates respirable crystalline silica. The federal construction standard applies to employers rather than to a homeowner working on their own house, but the control it requires is the same control that keeps the dust out of your lungs and off everything you own.
There is also a practical reason to control the dust. Uncontrolled dry grinding can distribute fine concrete dust through open doors and air returns and into rooms outside the work area. The same matched extraction needed for the table row also limits that migration.
Rental pricing varies, so price the grinder and its compatible vacuum as one control system rather than assuming the vacuum is included or treating it as an optional clean-up accessory.
Wet versus dry, and the thing nobody mentions about slurry
Water suppression is the other branch of the table and it works: it stops the dust at the source rather than capturing it afterwards. What it produces instead is slurry, which is concrete fines suspended in water, and slurry sets.
It has to be squeegeed up while it is still wet, and where it can be poured is a local question with a real answer that varies by jurisdiction — it is not a thing to put down a domestic drain on the assumption that it is only water and concrete. Wet grinding also leaves the slab soaked, which on a moisture-sensitive job means a drying delay you have to build into the schedule.
For a domestic garage, dry grinding with a properly filtered vacuum is usually the more practical of the two. For a large commercial floor with drainage and a plan for the slurry, wet is faster.
Biggest swing factor Whether the machine comes with working extraction. It changes the respirator requirement, the clean-up, and whether the rest of the building is habitable during the work.