Using walk-behind milling machines or floor grinders on concrete or other silica-containing materials can generate respirable crystalline silica dust. When inhaled, the small particles of silica can irreversibly damage the lungs.
Exposure controls needed in accordance with Appendix 4 of the Managing respirable crystalline silica in construction and manufacturing of construction elements code of practice 2022 (PDF, 1.71 MB) (the Code) when using walk-behind milling machines and floor grinders are explained below.
Step 1: Use suitable engineering controls
Engineering control options (one of the following two controls must be used):
- An integrated water delivery system that continuously delivers water to the cutting surface.
- A commercially available vacuum dust collection system which:
- meets or exceeds the minimum air flow requirements recommended by the tool manufacturer
- is rated to either M-Class or H-Class.
When using a dust collection system indoors or an enclosed area, use an M-Class or H-Class vacuum to remove loose dust between passes.
In each case the milling machine or grinder must be operated and maintained in accordance with manufacturer’s instructions to minimise dust emissions.
Using wet methods effectively reduces the amount of silica dust that becomes airborne when milling or grinding silica containing materials as it controls the exposure at its source. Walk-behind milling machines and floor grinders must be equipped with an integrated water delivery system that continuously delivers water to the cutting surface.
Clean up slurry produced before it dries and releases silica dust into the air. Wet slurry can be cleaned up using shovels or a wet vacuum.
Dust collection system
A commercially available dust collection system has been shown to reduce silica exposure. When using a machine equipped with a dust collection system, ensure it is operated and maintained in accordance with manufacturer's instructions to minimise dust emissions.
The dust collector must:
- provide the air flow recommended by the manufacturer or greater
- be rated to either M-Class or H-Class in accordance with AS/NZS 60335.2.69.
When used indoors or in an enclosed area, use a dust collector with either a M-Class or H-Class in accordance with AS/NZS 60335.2.69 to remove loose dust in between passes.
Step 2: Select appropriate respiratory protective equipment (RPE)
RPE is not required for the use of walk-behind milling machines and floor grinders.