Handheld grinders for mortar removal
Using handheld grinders to remove mortar (tuckpointing or removing mortar/concrete that has leaked from undersides of slab) 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 handheld grinders to remove mortar between brick, stone and concrete block are explained below.
Step 1: Use suitable engineering controls
Engineering control option:
Usea commercial dust collection system which includes:
- a commercially available shroud
- a dust collector that:
- provides at least an airflow of 25 cubic feet per minute per inch of blade (roughly 700 litres per 25mm of blade diameter)
- is rated to either M-Class or H-Class
- has a cyclonic pre-separator or filter cleaning mechanism.
Dust collection system
A dust collection system can be used to capture the dust generated when removing mortar with a handheld grinder. A person conducting a business or undertaking (PCBU) can comply by ensuring the dust collection system:
- has a commercially available shroud on the tool designed to fit the grinder and wheel size.
- provides at least 25 cubic feet per minute (cfm) of airflow per inch of blade (roughly 700litres per 25mm of wheel diameter) to capture dust at the point of grinding and removing mortar. For example, a five inch grinding wheel would require a rating of 125 cfm of air flow or more for effective capture
- is equipped with a cyclonic pre-separator
- is rated with a M-Class or H-Class as per AS/NZS60335.2.69.
The grinder and dust collector must be operated and maintained in accordance with the manufacturer’s instructions to minimise dust emissions. Dust collection systems are most effective when workers are properly trained and use good work practices.
- Keep the hose clear and free of debris, kinks and tight bends.
- Follow the equipment manufacturer’s directions to reduce dust build-up on the filter.
- Change vacuum-collection bags as needed. Do not overfill the bag.
- Set a regular schedule for maintenance and filter cleaning of the grinder and vacuum dust collection system.
- Avoid exposure to dust when changing vacuum bags and cleaning or replacing air filters.
Proper handling of the handheld grinder is very important.
- Place one side of the shroud against the working surface before inserting the blade into the mortar joint. This directs the dust into the shroud as the blade cuts into the mortar joint.
- Keep the shroud tight against the working surface to cut down on dust that would otherwise escape from the collection system.
- Move the grinder counter to the direction of blade rotation to minimise escaping dust.
- Back off the cutting pressure of the blade a short distance before removing it from the slot so the vacuum can have enough time to clear any dust build-up.
- Do not move the grinder back and forth along the slot, this will create a gap that increases dust escape. For best results, 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. Do not leave a large gap between the shroud and uncut mortar.
Compressed air
Unless there is a ventilation system that effectively captures the dust cloud, do not use compressed air or blowers to clean surfaces, clothing or filters as it can increase exposure to silica. Instead, clean with a M-Class or H-Class HEPA filter-equipped vacuum or by wet methods.
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 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.