When using handheld grinders to remove mortar, which involves tuckpointing or addressing mortar/concrete leaks from undersides of slabs, it's crucial 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 safeguard against 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):
Use suitable engineering controls
Opt for a commercial dust collection system, which includes:
- A commercially available shroud
- A dust collector with a minimum airflow of 25 cubic feet per minute per inch of blade (roughly 700 litres per 25mm of blade diameter)
- A rating of either M-Class or H-Class
- A cyclonic pre-separator or filter cleaning mechanism.
Dust collection system
Employ a dust collection system to capture dust when removing mortar with a handheld grinder. Ensure the system:
- Utilizes a commercially available shroud designed to fit the grinder and wheel size.
- Provides at least 25 cubic feet per minute (cfm) of airflow per inch of blade (roughly 700 litres per 25mm of wheel diameter) for effective dust capture.
- Includes a cyclonic pre-separator.
- Holds a rating of M-Class or H-Class according to AS/NZS60335.2.69.
The grinder and dust collector must be operated and maintained following the manufacturer’s instructions to minimize dust emissions. Workers should be properly trained, and good work practices should be followed.
Proper handling of the handheld grinder is crucial.
- Place one side of the shroud against the working surface before inserting the blade into the mortar joint.
- Keep the shroud tight against the working surface to minimize dust escape.
- Move the grinder counter to the direction of blade rotation to reduce escaping dust.
- Back off the cutting pressure of the blade a short distance before removing it from the slot to allow the vacuum to clear any dust build-up.
- Avoid moving the grinder back and forth along the slot, as it creates a gap that increases dust escape. Move the grinder in one direction, making a second pass only if necessary.
- Use only enough cutting force to operate the tool effectively and keep the leading tool edge flush against the working surface. Avoid leaving a large gap between the shroud and uncut mortar.
Compressed air
Avoid using compressed air or blowers to clean surfaces, clothing, or filters, as it can increase exposure to silica. Instead, clean with an M-Class or H-Class HEPA filter-equipped vacuum or by wet methods.
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.
RPE is required for the use of handheld grinders for mortar removal.
| 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 P2 filtered full face or half face piece with a positive pressure air supply with a MPF 50 required |
| Indoors / enclosed area P1 or P2 filtered RPE with a MPF 10 required | Indoors / enclosed area P2 filtered full face or half face piece with a positive pressure air supply with a MPF 50 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 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.