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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.

Further information