Large drivable milling machines (half lane and larger)
Using large drivable milling machines (half lane and larger) 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) when using large drivable milling machines are explained below.
Step 1: Use suitable engineering controls
Engineering control options:
- For cuts of any depth in asphalt, use a machine equipped with exhaust ventilation on the drum enclosure and supplemental water sprays designed to suppress dust.
- A machine equipped with exhaust ventilation on drum enclosures and supplemental water sprays designed to supress dust.
- For cuts of four inches or less in depth on any substrate, use a machine equipped with exhaust ventilation on the drum enclosure and supplemental water sprays designed to suppress dust.
Details of controls
Large drivable milling machines can be equipped with a combination of water sprays, exhaust ventilation and surfactants to effectively control silica dust.
The exact combination varies with milling depth and substrate material:
- Any depth on asphalt only: use a machine with exhaust ventilation on the drum enclosure and supplemental water sprays designed to suppress dust. When properly used, this control can effectively control silica dust.
- Four inches or less in depth on any substrate: use a machine equipped with either:
- exhaust ventilation on the drum enclosure and supplemental water sprays designed to suppress dust
- a machine equipped with supplemental water spray designed to suppress dust. Water must be combined with a surfactant.
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 of large drivable milling machines.