When using dowel drilling rigs, also known as gang drills, to drill holes in concrete, it's important for workers to be aware that this activity can generate respirable crystalline silica dust. Inhaling these small silica particles over time can lead to irreversible lung damage.
To address potential exposure, WorkCover Queensland recommends the following controls 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):
Use suitable engineering controls
Choose one of the following engineering control options:
- Implement a commercially available shroud or cowling with a tool-mounted HEPA filtered dust collector.
- Use a commercially available shroud or cowling with an on-tool capture hood connected to a dust extractor/vacuum that meets or exceeds the minimum airflow requirements recommended by the tool manufacturer and is rated to either M-Class or H-Class. Note: Utilize an M or H class vacuum when cleaning drilling holes.
Dust collection systems
When drilling into material containing one percent or more crystalline silica, dowel drill rigs must be equipped with a dust collection system.
The dust collection system should include 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.
Operate and maintain the drill and vacuum dust collection system according to the manufacturer’s instructions to minimize 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. Establish 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.
Select appropriate respiratory protective equipment (RPE)
The type of RPE needed depends on:
- The type of engineering controls in use.
- The duration of the task during the shift.
- The location where the work is being undertaken.
| Engineering control used | Time spent doing task during shift | |
|---|---|---|
| Equal or less than 4 hours | Greater than 4 hours | |
| Wet cutting (Option 1) | RPE not required | RPE not required |
| Dust extraction (Option 2) | Outdoors RPE not required | Outdoors RPE not required |
| Indoors / enclosed area RPE not 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.
A PCBU must provide health monitoring to a worker if their tasks require them to wear RPE 30 times or more in 12 months. See section 10 of the Code (PDF, 1.71 MB) for more information on health monitoring requirements.