Clean-up and disposal of silica dust
Clean-up and disposal of silica dust
The proper clean-up of the workplace, including the decontamination of clothing and PPE, and the correct disposal of silica contaminated material, play an important role in further minimising exposure to silica dust for workers, or others in the vicinity of the workplace.
6.1. Cleaning and housekeeping
General cleaning and housekeeping
Regular cleaning should be undertaken to prevent the build-up of dust on floors, walls, other surfaces and equipment. Cleaning should be conducted at least daily, ideally at the end of the working day. Workers should wear RPE and use good housekeeping practices when cleaning. The wearing of RPE throughout the cleaning process will reduce the risk of workers being exposed to silica dust or contaminated water mist.
To ensure good housekeeping practices:
- implement daily and thorough housekeeping and cleaning procedures for wet slurry and settled dust to prevent dust build up on surfaces, or it becoming airborne, in areas where the stone is processed, for example:
- walls and building support structures such as girders and cross members, and
- wash engineered stone slabs prior to processing and again before sending out for installation
- use low pressure water, wet sweeping or an M- or H- class rated vacuum cleaner to clean, tools, equipment, floors, walls and other surfaces
- regularly clean vehicle track or high use areas and keep it wet during the day
- prohibit the use of dry sweeping or compressed air to clean surfaces or clothing
- provide low pressure water from hoses for cleaning between tasks, and
- ensure all waste products are disposed of in a manner that minimises the risk of dust being redistributed over the workplace (for example covered, kept wet or bagged).
Dry sweeping methods, such as using brooms, or using compressed air to clean up accumulated dust, should never be used. These methods can recirculate silica dust into the air. Household vacuum cleaners are not designed for use with hazardous dusts and should never be used where silica dust is or may be present, even if they have a HEPA filter.
Decontamination of workers’ clothing and PPE
Dusty clothing and PPE can expose workers and others to silica dust. PPE should be cleaned after use to ensure that silica dust does not accumulate. Information about maintaining and cleaning PPE should be sourced from the manufacturer or supplier.
Examples of how exposure to silica dust carried on PPE and work clothes can be minimised include:
- using an industrial M- or H- class rated vacuum cleaner to remove dust from clothes and PPE
- by positioning these units at the exits of engineered stone processing areas, workers are encouraged to vacuum their clothes and PPE before leaving
- providing workers with access to an area to wash their arms, hands, faces and hair
- a low-pressure hose or tray of water may also be useful for cleaning the bottom of footwear to prevent tracking dust into other areas
- providing a laundry service for dusty work clothes and PPE so they are not taken home for washing
- if a commercial laundry is used, dampen the clothes and place them in a sealed, labelled plastic bag, and inform the laundry that the clothes are contaminated with crystalline silica
- requiring workers to change dusty clothing after each shift, or if they have just finished a very dusty task to change at their next break, and
- providing workers with rubber boots and aprons.
When working outdoors, the ground can be covered with plastic sheeting and remaining dust can be removed using the above methods.
More information about managing facilities at the workplace can be found in the Code of Practice: Managing the work environment and facilities
6.2. Management of water and waste
Management of wet slurry
Wet slurry is the resultant waste from water suppression. This slurry has the potential to build up from continuous processing using water suppression on equipment and machinery. The slurry is not hazardous while wet. However, if it dries, the dust can become airborne when disturbed and expose workers and others.
Wet slurry can be managed by:
- capturing or containing it through floor grading, grates, curbing and channelling
- keeping floors and surfaces wet, and
- regularly cleaning, including at the end of each day, to prevent wet slurry drying overnight.
Any wet slurry that is de-watered so that it is still wet, but of cake-like consistency, should be disposed of in a way that minimises the risk of dust being redistributed over the workplace. This may include covering the slurry, keeping it wet or bagging it before disposal.
Recycled water
Water that is recycled on-site for use in water suppression should be effectively filtered to remove silica dust and prevent contaminated water continually passing through the system. Without an appropriate filtration system there is a risk that continual recycling of water will increase the concentration of silica dust in the water over time and subsequently the level of silica dust in the mist arising from the water suppression activities.
Water recycling systems can filter slurry so that silica and other dust particles are removed from the water before it is re-used. These systems can include:
- a pit that collects slurry from drains
- a slurry collection tank and filter press that compacts silica and other particles into a solid block for disposal
- a slurry settlement tank and waste bag, where waste forms into a solid block, and
- a filtered water tank that recirculates clean water back into the water supply.
Some products, such as commercially available flocculants, promote the clumping of particles, and will consolidate silica dust in recycled water more effectively. Water that is recycled needs to be visually assessed to ensure it is clear. If the water has a cloudy or milky appearance this means it is likely to contain a high concentration of silica dust and may increase the risk that airborne particles or contaminated mist will be released in the workplace.
For further information on the management of recycled water, please refer to guidelines in your state or territory.
Disposal of contaminated material
The PCBU must ensure that containers of waste produced or generated at a workplace from a hazardous substance, including silica dust, are labelled. The label needs to reflect the nature of the waste as closely as possible, for example the label should identify the substance as ‘Silica dust hazard’.
Waste contaminated by silica dust can include any disposable clothing or PPE, rags used to clean the work area or tools or equipment that cannot be decontaminated or are no longer required.
Bags used for containing waste need to be strong enough to ensure they will not tear and release dust. To minimise the risk of a bag tearing or splitting, bags should not be filled more than half-full and excess air gently evacuated from the bag in a way that does not cause the release of dust.
The PCBU should have a waste management system in place that eliminates the risk of silica dust being released and becoming airborne.