Silica Control Measures for Workplace Exposure
Controls · Controls overview
Silica control measures are the engineering, work-pattern and respiratory controls that keep respirable crystalline silica exposure below the silica Workplace Exposure Limit. This page sets out how silica dust controls are selected against the COSHH hierarchy, where wet cutting silica methods and silica suppression actually work, and how silica management is evidenced through personal silica air sampling.
What silica control measures cover
Silica control measures are the practical steps an employer uses to prevent or reduce respirable crystalline silica (RCS) reaching the worker's breathing zone. They cover substitution of silica-bearing materials, water suppression at the cut, on-tool extraction matched to the tool, enclosure of high-energy silica work, dedicated silica LEV where extraction is fixed, work-pattern controls such as task rotation and exclusion zones, and RPE used as a residual control rather than a primary one.
Silica dust controls are not interchangeable. A water-fed cut-off saw is the appropriate primary control for kerb cutting; an M-class on-tool vacuum is the appropriate primary control for wall chasing; an enclosed wet processing line is the appropriate primary control for engineered stone fabrication. Choosing the wrong control — for example RPE in place of water suppression — is one of the most common reasons silica exposure stays above the silica WEL despite visible effort.
Selecting silica controls against the COSHH hierarchy
Silica exposure control follows the COSHH hierarchy in order: eliminate the silica-generating task where possible, substitute the silica-bearing material, apply engineering control at source, isolate the work, use administrative controls and only then rely on RPE. For silica specifically, this translates into a defined sequence: pre-cut units delivered to size, lower-silica or silica-free alternatives where available, wet cutting silica methods at the source, on-tool extraction into M- or H-class vacuums, enclosure for fixed-position work, and silica LEV where extraction is permanently installed.
Silica management does not finish at specifying the control. It finishes at evidencing that the control is in use at the cut, is maintained, is competent-tested and is keeping silica exposure below the WEL on representative shifts. That requires personal silica air sampling, not assumption.
- Eliminate or substitute silica-generating tasks and silica-bearing materials where possible.
- Apply wet cutting silica methods at the source — water-fed saws, water-fed chasers and water-fed grinders.
- Use on-tool extraction matched to the tool and routed into M-class or H-class vacuums.
- Enclose high-energy silica work where the layout supports it.
- Specify RPE only for residual silica exposure with documented fit testing.
Wet cutting silica and silica suppression in practice
Wet cutting silica methods are the single most effective control for many construction and stone tasks. A correctly specified water-fed cut-off saw, with adequate flow at the blade, can reduce RCS in the breathing zone by an order of magnitude relative to a dry cut. Water-fed wall chasers, water-fed core drills and water-fed engineered stone bridge saws follow the same logic.
Silica suppression depends on flow, not on intent. A water-fed tool with a dry or starved supply, with an unsuitable nozzle, or with water shut off because of housekeeping concerns is not a wet cut for silica control purposes. Operator training, supervisory verification and on-site checks of flow and coverage are part of the control, not an optional add-on. Where wet methods are not practical, on-tool extraction takes their place — but only where the capture hood, hose, vacuum and filter are matched and maintained.
Silica monitoring relevance for control assessment
Silica control measures are judged on outcomes — the residual silica exposure the operator actually breathes — not on equipment specifications. Personal silica air sampling on the operator's lapel with a respirable cyclone is the method used to confirm that water suppression, on-tool extraction, silica LEV and RPE are doing the job they were designed to do.
A defensible silica control assessment normally pairs each silica-generating task with at least one representative personal sample, documents the control configuration in use at the time, and compares the 8-hour time-weighted result against the silica WEL in HSE EH40 using the BS EN 689 strategy. Static (area) sampling supports diagnostic work — comparing two control configurations, characterising background, identifying hot spots — but does not replace personal sampling when the question is whether silica control is adequate.
When to request silica monitoring and control review
Workplaces typically commission silica control review and silica air sampling when introducing new silica-generating tasks, switching materials (engineered stone is a common trigger), changing water suppression or on-tool extraction provision, redesigning workshop layout, responding to a workplace inspection or enforcement notice, supporting a tender or insurance requirement, or refreshing an out-of-date COSHH assessment.
Review is also appropriate where supervisory observation suggests controls are drifting: water-fed tools running dry, on-tool vacuums disconnected, filter changes overdue, RPE without current fit testing, or housekeeping that re-entrains settled silica dust. Each is a routine finding and each is straightforward to fix when surfaced against measured silica exposure data.
Frequently asked questions
What is the most effective silica control measure for construction cutting tasks?
For most construction cutting tasks, wet cutting silica methods at the source are the most effective single control. A correctly specified water-fed cut-off saw, water-fed chaser or water-fed core drill, with adequate flow at the blade or bit, typically reduces respirable silica in the breathing zone by an order of magnitude compared with the equivalent dry cut.
When is on-tool extraction preferred over wet cutting for silica control?
On-tool extraction is the appropriate primary silica control where water introduces unacceptable secondary risks (live electrical work, certain finishing tasks) or where the substrate cannot be wetted. It is also used alongside water suppression for some grinding and polishing tasks. The on-tool vacuum should be M-class or H-class, matched to the tool's capture hood and to the volume of silica dust generated.
Is RPE on its own an acceptable silica control measure?
No. RPE is a residual silica control used to manage exposure that remains after engineering controls have been applied as far as reasonably practicable. RPE used as the primary silica control — without water suppression, on-tool extraction, enclosure or silica LEV in place — is not consistent with the COSHH hierarchy and is unlikely to keep silica exposure reliably below the silica WEL.
How are silica control measures evidenced for COSHH?
Silica control measures are evidenced through personal silica air sampling on representative operators and tasks, with the control configuration documented at each sample point. The 8-hour time-weighted exposure is compared against the silica WEL in HSE EH40. Maintenance records, on-tool extraction servicing, silica LEV thorough examination certificates and RPE fit-test records support the air monitoring data.
Do silica control measures need to be reviewed if nothing has changed?
Yes — periodic review is expected even where the work appears stable. Tools wear, water supply pressure drifts, on-tool extraction capture efficiency falls as filters load, operator behaviour shifts and materials are quietly substituted. Without periodic silica air sampling, a control assessment is working from assumptions rather than evidence.
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