Dowel drilling rigs for concrete
Using dowel drilling rigs, also known as gang drills, to drill holes in concrete 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 dowel drilling rigs are explained below.
Step 1: Use suitable engineering controls
Engineering control options (one of the following two controls must be used):
- Commercially available shroud or cowling with a tool mounted HEPA filtered dust collector.
- Commercially available shroud or cowling with an on-tool capture hood connected to a dust extractor/vacuum which meets or exceeds the minimum air flow requirements recommended by the tool manufacturer and is rated to either M-Class or H-Class.
Note: Use a M or H class vacuum when cleaning drilling holes.
Dust collection systems
When drilling into material that contains one per cent or more crystalline silica, dowel drill rigs need to be equipped with a dust collection system.
The dust collection system must be equipped with a:
- shroud or cowling sized to fit around the drill bit
- dust collector rated to provide the airflow recommended by the tool manufacturer or greater and either:
- A tool mounted HEPA-filtered dust collector
- an on-tool capture hood connected to a dust extraction system rated to either M or H-Class in accordance with AS60335.2.69.
The drill and vacuum dust collection system must be operated and maintained in accordance with the manufacturer’s instructions to minimise dust emissions.
- Keep the vacuum hose clear and free of debris, kinks and tight bends.
- Activate non-automatic filter-cleaning mechanisms as needed to reduce dust build-up on the filter.
- Change vacuum-collection bags as needed.
- Set a schedule for filter cleaning and maintenance.
- Avoid exposure to dust when changing vacuum bags and cleaning or replacing air filters.
- Clean the dust and debris from the drilled holes, a HEPA-filtered vacuum system must be used to capture the dust.
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 required when using dust extraction. Half face reusable or disposable RPE has a minimum protection factor (MPF) of 10.
| Engineering control used | Time spent doing task during shift | |
|---|---|---|
| Equal or less than 4 hours | Greater than 4 hours | |
| Dust extraction |
Outdoors P1 or P2 filtered RPE with a MPF 10 required |
Outdoors P1 or P2 filtered RPE with a MPF 10 required |
|
Indoors / enclosed area P1 or P2 filtered RPE with a MPF 10 required |
Indoors / enclosed area P1 or P2 filtered RPE with a MPF 10 required | |
For tight fitting RPE, workers must be fit-tested to the specific make and model before using it. See section 7.6 of the Code (PDF, 1.71 MB) for more information on fit-testing and other requirements for using RPE.
Health monitoring
A person conducting a business or undertaking (PCBU) must provide health monitoring to a worker if their tasks require them to wear RPE 30 times or more in 12 months.