Using small drivable milling machines (less than half lane) on asphalt pavement, concrete and 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 small drivable milling machines are explained below.
Step 1: Use suitable engineering controls
Engineering control options:
Wet cutting machines equipped with supplemental water supplies designed to supress dust and surfactant combined with the water.
When using a small milling machine (a width of less than one lane) the machine should be equipped with a supplemental water spray system. The water sprayed must be combined with a surfactant.
Supplemental systems use a pump to deliver water (with surfactant) to the milling surface and conveyor which combines with dust and silica particles and reduces airborne levels.
The keys to effective dust control are:
- water pressure and water flow rate
- proper application of water combined with a surfactant
- nozzle location and orientation
- controlling droplet size
- selecting the best spray pattern and spray nozzle type for the operation
- correct maintenance of nozzles and water spray application equipment.
The machine must be operated and maintained to minimise dust emissions.
Step 2: Select appropriate respiratory protective equipment (RPE)
The type of RPE you will need depends on:
- what type of engineering controls you are using
- how long the worker is going to do the task during the shift
- where the work is being undertaken.
RPE is not required for the use small milling machines (less than half-lane)