Common questions builders ask about silica dust on construction sites.
What is the workplace exposure limit for silica dust?
The workplace exposure limit (WEL) for respirable crystalline silica in the UK is 0.1 mg/m³, measured as an 8-hour time-weighted average. This limit is set out in HSE document EH40 and applies to all workplaces where silica dust may be generated. To put that number in context, 0.1 mg/m³ is an extremely small concentration — you cannot see it, smell it, or taste it, which is exactly what makes silica dust so dangerous. Dry-cutting a single concrete block can exceed this limit within minutes. The WEL is not a safe level; it is the maximum legally permitted concentration. You are expected to reduce exposure as far below the WEL as is reasonably practicable, not simply aim to stay just under it. If you are regularly carrying out tasks that generate silica dust — cutting, grinding, drilling concrete, brick, or stone — you must have effective controls in place and should consider whether exposure monitoring is needed to confirm those controls are working.
Do I need an FFP3 mask for cutting concrete?
Yes. When cutting, grinding, or drilling concrete, brick, stone, or mortar, an FFP3-rated disposable mask or a reusable half-mask with P3 filters is the minimum standard of respiratory protective equipment (RPE) for silica dust. An FFP2 mask is not sufficient — it does not provide enough protection against respirable crystalline silica. However, RPE should always be your last line of defence, not your first. Before reaching for a mask, you should be using engineering controls such as wet cutting or on-tool extraction to reduce dust at source. RPE is there to deal with whatever residual dust those controls cannot eliminate. Crucially, every tight-fitting RPE must be face-fit tested to the individual wearer. A mask that does not seal properly to your face will let contaminated air leak in around the edges, making it effectively useless. Face-fit testing must be carried out by a competent person, and records must be kept. If you have facial hair that breaks the seal, you will need a powered air-purifying respirator or a loose-fitting hood instead.
What is on-tool extraction and do I need it?
On-tool extraction means attaching a dust extraction unit directly to the power tool that generates the dust. When you cut, grind, or chase concrete with a tool fitted with on-tool extraction, the dust is captured at source before it becomes airborne and enters your breathing zone. A typical setup consists of a shroud or hood fitted around the blade or disc, connected by a hose to a Class M or Class H dust extraction unit with a HEPA filter. The HSE considers on-tool extraction to be one of the most effective engineering controls for silica dust, and for many tasks it is now effectively mandatory. The HSE’s guidance INDG463 makes clear that dry cutting, grinding, or chasing without dust suppression or extraction is not acceptable. If you are using angle grinders, wall chasers, concrete saws, or breakers on concrete, brick, or stone, you should have either on-tool extraction or wet suppression in place. On-tool extraction is often the more practical choice indoors, where water suppression can create slip hazards and mess. The extraction unit must be suitable for the task — a standard workshop vacuum is not adequate.
How often do workers need health surveillance for silica exposure?
Under the COSHH Regulations, health surveillance is required for any worker who is regularly exposed to respirable crystalline silica above a level where there is a reasonable likelihood of disease developing. In practice, this means anyone who routinely cuts, grinds, drills, or demolishes concrete, brick, or stone. Health surveillance for silica typically involves a health questionnaire and lung function test (spirometry) carried out by a qualified occupational health professional. The initial assessment should be done before or shortly after the worker begins the exposed role, with follow-up assessments at least every 12 months. If the occupational health professional identifies any concerns — a decline in lung function, respiratory symptoms, or abnormal results — they may recommend more frequent testing or referral for a chest X-ray. Employers must keep health surveillance records for at least 40 years, because silica-related diseases can take decades to develop. Health surveillance is not a substitute for dust controls. Its purpose is to detect early signs of disease so that exposure can be reduced before irreversible damage occurs.
Is wet cutting enough to control silica dust?
Wet cutting is one of the most effective methods for suppressing silica dust and can reduce airborne dust by up to 90 per cent compared to dry cutting. However, whether it is “enough” on its own depends on the task, the duration, the environment, and the residual dust levels after suppression. For short-duration outdoor tasks — such as cutting a few paving slabs or bricks — wet cutting with an adequate water supply may be sufficient to keep exposure well below the workplace exposure limit. For prolonged or repetitive cutting, or for work in enclosed or poorly ventilated spaces, wet cutting alone may not reduce dust levels far enough. In those situations, you should combine wet cutting with other controls such as on-tool extraction, local exhaust ventilation, or segregation of the cutting area from other workers. You should also provide RPE as a backup. The key principle is that you must reduce exposure as far below the WEL as is reasonably practicable — if wet cutting alone does not achieve that, you need additional measures. Always check that the water supply is reaching the blade effectively and that run-off slurry is managed safely to avoid slip hazards.