LEV for Silica Dust: Controlling RCS in Stone, Concrete and Construction Work

Respirable crystalline silica is the biggest cause of occupational lung disease in construction after asbestos. Cutting, grinding, drilling and polishing stone, concrete, brick and engineered worktops releases a fine dust that lodges deep in the lungs. Over time it causes silicosis, chronic obstructive pulmonary disease, and lung cancer. There is no cure for silicosis, and the damage is permanent.

The dust that causes the harm is the part you cannot see. Respirable crystalline silica — RCS — is small enough to reach the deepest parts of the lung. A visible dust cloud is a warning sign, but even when the air looks clear, dangerous levels of fine silica can be present.

For most cutting and grinding operations, controlling that dust means water suppression, local exhaust ventilation, or both.

What Respirable Crystalline Silica Is

Crystalline silica is a natural mineral found in most rocks, sand, clay and the materials made from them — concrete, mortar, bricks, tiles, sandstone, granite, and engineered stone worktops. Engineered (resin-bound) worktops can contain very high proportions of crystalline silica, which is why fabricating them is a particularly high-risk activity.

When you work these materials with power tools, you generate dust. The proportion of that dust that is fine enough to be inhaled deep into the lungs is the respirable fraction. RCS is the respirable fraction that is crystalline silica.

Tasks that generate RCS include:

• Cutting paving, kerbs, blocks and slabs
• Chasing walls and cutting channels for cables or pipes
• Grinding and smoothing concrete and screed
• Drilling into masonry, concrete and stone
• Fabricating and polishing stone and engineered worktops
• Demolition and clean-up where silica-containing debris is disturbed

The Workplace Exposure Limit for RCS

The workplace exposure limit for respirable crystalline silica is set in EH40:

• Respirable crystalline silica: 0.1 mg/m³ (8-hour time-weighted average)

There is no separate short-term limit for RCS. The 0.1 mg/m³ figure is very low — a level you cannot judge by eye. A worker can be exposed well above the limit even when the visible dust seems modest. This is why the law does not rely on workers spotting dust; it requires you to design out the exposure with proper controls.

Because silica is a carcinogen and a cause of irreversible disease, COSHH Regulation 7 requires exposure to be controlled so far as is reasonably practicable — not simply kept below the limit. The lower you can get exposure, the lower the long-term risk.

How to Control Silica Dust at Source

The HSE's guidance for construction sets out two main engineering controls for silica dust, used alone or together.

Water suppression. Feeding water to the cutting point keeps the dust damp so it cannot become airborne. Many cut-off saws, floor saws and core drills have integrated water feeds. Water suppression is simple and effective, but it must deliver enough water at the right point, and it must be kept running for the whole task — not just at the start.

On-tool extraction (LEV). A dust extraction unit attached directly to the power tool captures dust at the point it is created, before it reaches the operator's breathing zone. This is local exhaust ventilation built into the tool. On-tool extraction needs a shroud or hood that fits the tool, an extraction unit rated for fine dust (typically an M-class or H-class dust extractor for silica), and the right hose and filter combination.

On-tool extraction is LEV, and it carries the same legal duties as any other LEV system: it must be suitable for the job, used correctly, maintained, and thoroughly examined and tested.

Why On-Tool Extraction Is a COSHH LEV System

It is easy to think of LEV as fixed ductwork bolted to a wall in a factory. But a dust extractor clipped to a hand-held grinder is just as much a local exhaust ventilation system in the eyes of the law. It captures a hazardous contaminant at source and removes it from the air the worker breathes.

That means the COSHH duties for LEV apply:

• The extraction must be suitable — the right class of extractor, the right shroud, sufficient airflow for the tool and material
• It must be used correctly every time the task is done — not left in the van
• It must be maintained so it keeps performing — filters cleaned or replaced, hoses checked for blockages, seals intact
• It must be thoroughly examined and tested at suitable intervals

This last point catches many businesses out. On-tool extraction units are LEV, and where they are used to control exposure to a hazardous substance, they fall within the thorough examination and test regime.

Thorough Examination and Testing for Silica LEV

COSHH Regulation 9 requires LEV systems to be thoroughly examined and tested at least once every 14 months. For most silica-control LEV — fixed extraction at a fabrication bench, a downdraught table for worktop polishing, or on-tool extraction units used routinely — that 14-month deadline applies.

The thorough examination and test, or TExT, is more than a quick visual check. It is a structured examination by a competent person that verifies the system is still capturing dust effectively and performing as it should. The result is a TExT report that you must keep.

You also need to keep records for at least five years, carry out and record user checks between tests, and act on any defects the examination finds. Our guide on how often LEV must be tested explains the 14-month rule in detail, and the LEV testing due date calculator works out your next deadline for each system.

HSE Enforcement on Silica

The HSE treats silica as a priority health risk. Inspectors visiting construction sites, stone fabrication workshops and demolition jobs will look closely at how silica dust is controlled. Stoneworking — especially the fabrication of engineered worktops — has drawn particular scrutiny because of a rise in serious silicosis cases among relatively young workers.

During an inspection, the HSE will typically check:

• Whether a risk assessment identifies the silica-generating tasks and the controls needed
• Whether water suppression or on-tool extraction is in place and being used for those tasks
• Whether dust extractors are the right class for fine dust
• Whether LEV used to control silica has a current TExT report within the 14-month window
• Whether records of testing, maintenance and user checks are available
• Whether respiratory protective equipment is provided where engineering controls alone are not enough, and whether it is face-fit tested
• Whether health surveillance is in place where workers are regularly exposed

Practical Compliance Steps

1. Identify every silica-generating task. Walk through your work — on site and in the workshop — and list every operation that cuts, grinds, drills or polishes silica-containing material. Include occasional tasks, not just routine ones.

2. Decide the control for each task. Water suppression, on-tool extraction, or both. For workshop fabrication and polishing, fixed LEV or downdraught benches are usually appropriate. For site cutting and drilling, on-tool extraction or water suppression on the tool.

3. Match the extractor to the dust. Fine silica dust needs an extractor rated for it — typically M-class or H-class. A general workshop vacuum is not adequate for RCS.

4. Bring your LEV into the TExT regime. Every silica-control LEV system, including routinely-used on-tool extraction, needs thorough examination and testing within 14 months. Use the LEV compliance checklist generator to build a structured assessment of your systems.

5. Keep your records. TExT reports, user check logs, maintenance records. The record-keeping requirements checker helps you confirm you are meeting the requirements.

6. Provide RPE where needed. Where engineering controls cannot get exposure low enough, suitable respiratory protection — correctly chosen, face-fit tested and maintained — controls the residual risk.

7. Arrange health surveillance. Where workers are regularly exposed to RCS and silicosis could develop, health surveillance is required.

LEVproof is being built to help UK businesses manage LEV compliance — TExT tracking, automated 14-month reminders, and digital record-keeping for every system including on-tool extraction. Join the waitlist for early access.

Sources

• Control of Substances Hazardous to Health Regulations 2002 (COSHH) — legislation.gov.uk
• EH40/2005 Workplace exposure limits — HSE
• Cancer and construction: Silica — HSE
• Construction silica — COSHH essentials — HSE
• HSG258: Controlling airborne contaminants at work — HSE

This guide summarises published HSE and government guidance. It does not constitute legal advice. Consult a qualified professional for advice specific to your situation.