Silica LEV Systems
Controls · Controls overview
Silica LEV systems — local exhaust ventilation engineered specifically for respirable crystalline silica — capture silica dust at source before it reaches the operator's breathing zone. This page sets out how silica extraction systems are specified, how silica fume extraction differs from generic dust extraction, and how silica LEV is verified through statutory thorough examination and personal silica air sampling.
What silica LEV systems are designed to do
Silica LEV is local exhaust ventilation designed and installed with the specific purpose of controlling respirable crystalline silica at source. That includes on-tool LEV connected to portable M- or H-class vacuums, fixed capture hoods over bridge saws, edge-polishers and CNC routers in engineered stone workshops, enclosed wet processing lines, downdraft tables for finishing tasks, and ducted booth extraction for blast rooms.
Local exhaust ventilation silica systems are not the same as general workshop airflow. General ventilation dilutes residual silica that has already entered the room; silica LEV captures silica dust before it gets there. The two are complementary, but only source capture changes the silica exposure profile of the operator at the cut.
Silica extraction systems and silica fume extraction
Silica extraction systems are specified around the task: the volumetric flow needed at the capture point, the static pressure required for the duct run, the filter class needed for the respirable silica fraction, and the discharge route (recirculation back into the workshop is rarely appropriate for respirable silica without H-class filtration and competent verification). Dust extraction silica equipment serving high-energy tools such as bridge saws or edge profilers typically needs higher flow and more robust filtration than the same equipment used on coarse, non-respirable dust.
Silica fume extraction is the term often used where silica-bearing material is heated or thermally cut — for example certain stone cutting and refractory tasks — and a finer aerosol fraction is generated. The extraction principle is the same: capture as close to the source as practical, route through filtration matched to the respirable fraction, and verify that capture velocity at the source is maintained as filters load and ductwork ages.
- On-tool LEV connected to M-class or H-class vacuums for portable tools.
- Fixed capture hoods over bridge saws, polishers and engineered stone CNC routers.
- Enclosed wet processing lines for high-throughput stone fabrication.
- Downdraft tables and ducted booths for finishing and abrasive blasting.
- Filter class and discharge route specified for the respirable silica fraction.
Workplace context for silica LEV
Silica LEV is most often encountered in engineered stone fabrication workshops, monumental masonry, refractories, foundries, blast rooms and high-volume concrete cutting facilities. In each case the LEV exists to control a defined silica task — sizing, mitring, profiling, polishing, blasting, finishing — rather than to ventilate the room as a whole.
Mobile construction work tends to rely on on-tool LEV (portable vacuums connected to the tool) rather than fixed silica extraction systems, because the work moves. The same principles apply: the capture point must remain at the cut, the hose and vacuum must be matched to the tool, and the filter class must be appropriate for respirable silica.
Verifying silica LEV — thorough examination and air sampling
Silica LEV systems used to control a substance hazardous to health are subject to thorough examination and test under COSHH Regulation 9, normally at intervals not exceeding 14 months. The thorough examination records design intent, measures capture velocity or face velocity at defined points, checks filter integrity and pressure drop, inspects ductwork and dampers, and confirms the system is operating within its specified envelope.
Thorough examination is necessary but not sufficient evidence of silica control. The defensible question is whether the operator's silica exposure, with the LEV running, sits below the silica WEL on representative shifts. That answer comes from personal silica air sampling on the operator's lapel, with the silica LEV configuration documented in the sample log.
When to request silica monitoring against LEV provision
Silica monitoring against LEV provision is typically commissioned after installation or modification of a silica extraction system, after a thorough examination flags capacity or capture issues, after changes to tools, materials or work patterns that the original silica LEV was not sized for, after a workplace inspection or enforcement notice, or as periodic verification that the silica LEV is still controlling exposure as designed.
It is also commissioned where workshop expansion has outgrown the original system — more operators, longer shifts, more aggressive cutting — and where the existing silica LEV may now be undersized for the silica dust loading it is asked to handle.
Frequently asked questions
What makes silica LEV different from general workshop ventilation?
Silica LEV captures respirable silica at source — at the saw, the polisher, the chaser, the blasting booth — before it reaches the operator's breathing zone. General workshop ventilation dilutes residual silica that has already entered the room. For RCS control, source capture is the part of the system that changes the operator's exposure profile.
How often must silica LEV be examined?
LEV used to control a substance hazardous to health is subject to thorough examination and test under COSHH Regulation 9 at intervals not exceeding 14 months, with shorter intervals for certain higher-risk processes. The examination covers capture velocity, filter integrity, ductwork and overall fitness against the original design intent for silica control.
Can on-tool extraction count as silica LEV?
Yes — on-tool LEV (a portable vacuum matched to the tool's capture hood) is a form of local exhaust ventilation silica system and is subject to the same Regulation 9 thorough examination duty. The vacuum class (typically M or H for respirable silica), the hose, the hood and the filter change schedule all form part of the assessed system.
Does silica LEV remove the need for RPE?
Often, well-designed and maintained silica LEV reduces the operator's residual exposure to a level where RPE is a short-duration or task-specific control rather than the primary one. Whether RPE remains necessary is answered by personal silica air sampling against the silica WEL with the LEV running, not by assumption.
What filter class is appropriate for silica extraction systems?
Equipment serving tasks that release respirable crystalline silica typically uses M-class or H-class filtration appropriate to the respirable size fraction. Specification should reflect the task, the dust loading and the discharge route; recirculation back into the workshop is rarely appropriate for respirable silica without H-class filtration and competent verification.
Related pages