What Determines the Level of Silica Dust Exposure?

The amount of dust generated and the resulting exposure risk will depend on factors including:

• The type of material and its crystalline silica content.
• The tool and working method used.
• The speed, power and duration of the activity.
• Whether the work takes place indoors or outdoors.
• The size and ventilation of the work area.
• The distance between workers and the dust source.
• The effectiveness of extraction or water suppression.
• The standard of workplace cleaning and housekeeping.

The absence of a visible dust cloud does not mean that exposure is adequately controlled. The smallest and most hazardous respirable particles may be difficult or impossible to see.

Cutting Concrete, Bricks, Blocks and Tiles

Cutting silica-containing materials is one of the most common high-risk activities. Handheld cut-off saws, disc cutters and angle grinders can release large amounts of fine dust directly into the operator's breathing zone.

High-risk cutting activities include:

• Cutting concrete slabs and paving.
• Cutting bricks and concrete blocks.
• Cutting roof tiles, floor tiles and wall tiles.
• Cutting kerbstones and natural stone.
• Chasing channels into concrete or masonry.

These tasks can expose the operator and other people nearby. Suitable on-tool extraction or water suppression should be used to control dust at its source. Additional RPE may also be required following the COSHH risk assessment.

Drilling, Chiselling and Breaking Masonry

Drilling or chiselling into concrete, walls, floors and masonry can produce significant quantities of respirable silica dust. Even drilling relatively small holes may create hazardous exposure if suitable controls are not used.

Examples include:

• Drilling fixing holes in concrete or brickwork.
• Using rotary hammer drills.
• Chasing walls for cables and pipework.
• Using powered chisels and breakers.
• Core drilling through concrete or masonry.

Exposure must be controlled even when the task lasts only a few minutes. The workplace exposure limit is not a boundary between safe and unsafe exposure; employers must prevent exposure where reasonably practicable or otherwise control it adequately.

Grinding and Sanding Operations

Grinding and sanding can generate hazardous dust because the process removes material at high speed and produces very fine particles.

Materials that may create hazardous dust during grinding or sanding include:

• Concrete and mortar.
• Natural and engineered stone.
• Plaster and plasterboard.
• Wood and wood-based products.
• Painted or coated surfaces.

Different materials produce different hazards. For example, wood dust and dust from old painted surfaces require their own suitable assessments and controls.

Grinding and sanding indoors can cause airborne dust to accumulate rapidly, particularly where ventilation and source extraction are inadequate.

Demolition and Refurbishment Dust

Demolition and refurbishment work can release large quantities of mixed dust when materials are broken, removed or disturbed.

High-risk activities may include:

• Breaking out concrete.
• Removing mortar and render.
• Knocking down walls.
• Removing tiles, flooring or screed.
• Cutting openings through masonry.
• Removing old fixtures and building materials.

The resulting airborne contamination may contain a mixture of silica dust, cement dust, plaster dust, wood dust and other hazardous substances.

Potential Asbestos During Refurbishment Work

Older buildings may also contain asbestos-containing materials. The appropriate asbestos survey and assessment must be completed before intrusive demolition or refurbishment work begins.

If a material suspected of containing asbestos is discovered, work should stop and the area should be left undisturbed. The employer must follow the site's asbestos procedures and obtain competent advice before work resumes.

Handling and Mixing Powdered Materials

Cement, grout, mortar, sand and other powdered products can release hazardous dust when bags or containers are opened, emptied or mixed.

Exposure can occur when workers:

• Open or split bags.
• Tip powders into mixers or containers.
• Scoop or measure dry materials.
• Pour materials from height.
• Mix powders too quickly.
• Clean up spillages using a dry brush.

Bags should be handled carefully and emptied close to the receiving container to reduce the distance through which the material falls. Where suitable, enclosed mixing, pre-mixed products or other lower-dust alternatives should be considered.

Powdered materials should be handled using methods that minimise disturbance and prevent visible dust clouds.

Dry Sweeping and Secondary Dust Exposure

Dry sweeping is a commonly overlooked source of hazardous dust exposure. Sweeping a contaminated floor with a broom can disturb settled particles and release them back into the air.

This secondary exposure may affect cleaners, tradespeople, visitors and anyone else nearby. Dust may also spread from the immediate work area into corridors, vehicles, welfare facilities and other clean spaces.

Safer cleaning methods include:

• Using a suitable M-class dust extractor.
• Using an H-class extractor where identified by the risk assessment.
• Using appropriate wet-cleaning methods.
• Damping down dust before carefully collecting it.

Dry sweeping should be avoided wherever it could make hazardous dust airborne.

Cleaning With Compressed Air

Using compressed air to clean tools, equipment, clothing or surfaces can disperse fine dust throughout the workplace. The dust may remain suspended and expose people who were not involved in the original task.

Compressed air should not be used to remove silica dust or other hazardous dust. Equipment and surfaces should instead be cleaned using a suitable dust extractor or an appropriate wet method.

Working in Enclosed or Poorly Ventilated Areas

Dust-producing work presents a greater risk when completed in enclosed or poorly ventilated spaces because airborne contamination cannot disperse easily.

Potentially high-risk locations include:

• Internal rooms and corridors.
• Basements.
• Lift shafts.
• Service ducts and risers.
• Tunnels.
• Small workshops and temporary enclosures.

Dust can accumulate quickly and remain airborne after the task has finished. General ventilation alone may not adequately control exposure.

Source extraction, water suppression, restricted access, suitable cleaning and appropriate RPE may all be necessary. Where the area meets the definition of a confined space, the additional legal requirements and emergency arrangements for confined-space work must also be addressed.

Assessing High-Dust Work Before It Begins

Employers and managers must identify hazardous dust-producing activities through a suitable and sufficient COSHH risk assessment. The assessment should determine:

• Which hazardous dusts may be produced.
• Who could be exposed.
• The likely amount and duration of exposure.
• Whether the task can be eliminated or completed differently.
• Which engineering and administrative controls are required.
• Whether suitable RPE is needed as additional protection.
• How the area and equipment will be cleaned safely.

Controls must be established before the activity starts and monitored throughout the work. If the controls fail or dust is escaping, the task should stop until adequate protection has been restored.