Dust control
What the silica table requires for this job
Grinding concrete can release respirable crystalline silica. The federal construction standard has a table (Table 1) that lists eighteen tasks with the controls and respirator protection specified for each. This page reads that table for floor and handheld grinders, and says so when the method you choose, such as shot blasting, has no row.
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
- With the listed control in place, this row requires no respirator at either shift length.
- Preparing 440 square feet takes hours, and the shift length you enter decides which respirator column of the table applies.
The sentences this page is reading
These are cells from the two Table 1 rows that cover floor grinding (items xiii and xii), the sentence that sends tasks not in the table to the alternative route, and the airborne limit. Each is quoted so you can check it 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
For tasks not listed in Table 1, or where the employer does not fully and properly implement the engineering controls, work practices, and respiratory protection described in Table 1
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 can release respirable crystalline silica. The federal construction standard places its duties on employers rather than on a homeowner working on their own house, but the controls its Table 1 lists for floor grinders are the same controls that keep the dust out of your own lungs and out of the rest of the house.
There is also a practical reason to control the dust. Uncontrolled dry grinding can carry fine concrete dust through open doors and air returns into rooms outside the work area, and the extraction the table row calls for also limits that.
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 slurry
Water delivery is the other branch of the table: it suppresses the dust at the cutting surface rather than collecting it afterwards. What it produces instead is slurry, 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 that varies by jurisdiction; do not assume it can go down a domestic drain. Wet grinding also wets the slab, which on a moisture-sensitive job adds a drying delay to the schedule.
Which branch suits a job depends on drainage, on whether the slurry has somewhere to go, and on the drying time the coating allows. The table accepts either for a walk-behind floor grinder.
Biggest swing factor Whether the machine comes with working extraction. For a floor grinder it decides whether a Table 1 control is in place at all, and how much dust reaches the rest of the building.
Where this table sits among the other rules that apply
Permits and federal rules sets this standard beside three other federal documents that bear on a resinous floor in different ways — the VOC table, a federal specification's moisture clause and the ADA slip-resistance requirement — and the local permit question.