Controlling the risk of dust exposure to workers in mines
From 1 September 2020, the occupational exposure limits (OEL) for respirable dust and respirable crystalline silica (RCS) are 1.5mg/m3 and 0.05mg/m3 respectively.
The risk of workers being exposed to hazardous dust particles should be controlled using the hierarchy of controls shown below. Controls should focus on higher-order controls (e.g. elimination, substitution and isolation of the hazard) as the most effective means of treating the hazard.
Note: The Mining and Quarrying Safety and Health Regulation 2017 includes a specific requirement for controls to be applied in this order.
Hierarchy of controls
Hazard controls should be applied in this order:
- Elimination—remove the hazard, or the need to perform the hazardous activity.
- Substitution—substitute a safer alternative.
- Separation/isolation—isolate or separate people from the hazard by use of barriers, distance or time.
- Engineering controls—redesign or modify tools or equipment.
- Administrative controls—use training, rules, procedures to reduce the risk of the hazard.
- Personal protective equipment—provide fit-for-purpose protective equipment.
More than one control may need to be used to adequately control the hazard. Controls used must be maintained to ensure they continue to remain effective.
Examples of dust controls
- Adopt production processes that generate less dust (any wet method is likely to generate less dust than a dry one).
- Treat the dust at its point of generation, as this is more effective than capturing airborne dust.
- Treat the dust on its transmission path using dust suppression techniques (e.g. water sprays, chemical additives, local exhaust ventilation (LEV), vacuum).
Substitution with a lesser hazard
- Substitute with a less hazardous substance, such as the use of pellets rather than powders, or replace sand with garnet as abrasive blasting agent.
Separation/isolation of workers from the hazard
- Place a physical barrier between the dust-generating task and the worker, such as the use of enclosed cabins to isolate workers.
- Use remotely operated machinery, such as remotely controlled conveyors.
- Choose appropriate equipment (e.g. correct cutting blades for ore body).
- Replace and maintain equipment regularly to ensure cutting blades and picks remain sharp.
- Suppress dust by using water sprays on stockpiles and roads, and when using machinery and cutting equipment. Use additive in water sprays to suppress dust and adjust the droplet size of the spray according to dust particle size.
- Use enclosures (e.g. covered conveyors, enclosed cabs on vehicles, plant and equipment).
- Rehabilitate exposed mine land to reduce environmental dust load.
- Use ventilation and filtration to minimise dust (e.g. adjust ventilation rates for maximum efficiency, use local exhaust ventilation when necessary).
- Enclose cabins where possible, ensure seals are well-maintained, provide inlet air filtration for respirable particles, and use positive pressure air inside cabs to prevent dust penetration.
- Cover product conveyors.
- Cover loads for road haulage where practicable.
- Apply stone dust to underground workings.
- Ensure regular maintenance and housekeeping of vehicles and mine workings.
- Position personnel away from dust-generating activity by establishing exclusion zones.
- Maintain unmade roads and ensure ground conditions throughout sites are appropriate to the machines using them.
- Provide training and information to workers on the hazards, risks and controls of dusty tasks, as well as supervision for workers.
- Limit the duration and magnitude of exposure to dust (e.g. worker rotation, job task changes).
- Ensure work schedules have adequate rest periods to limit exposure.
- Change the location of dumping operations or modify blasting programs to suit weather conditions.
- Provide adequate signage.
Personal protective equipment (PPE)
- Ensure higher-order controls are adopted before resorting to PPE.
- Select the most appropriate respiratory protection for the task (e.g. P1 or P2, full face, half face, powered air, purifying). Read AS/NZS 1715 – Selection, use and maintenance of respiratory protective equipment for guidance.
- Ensure training, comfort and fit testing are provided before use. Respirators should not be shared.
- Maintain and store respiratory protective equipment properly.