LEV is a ventilation system designed to capture airborne hazardous substances — dust, fume, mist, vapour, gas — at or close to the point where they are released, and convey them through ductwork, an air cleaner and a discharge to a safe location. Unlike general ventilation, LEV does not rely on dilution; it removes the contaminant before it can mix with the room air.
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The definition
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The five parts of an LEV system
- Hood / capture device — the inlet placed close to the source (enclosing hood, captor hood, receptor hood)
- Ductwork — sized for transport velocity to keep particles airborne
- Air cleaner — filter, scrubber or cyclone matched to the contaminant
- Fan — provides the static pressure to overcome system resistance
- Discharge — to outside, sited away from intakes and openable windows
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Where you'll find LEV in UK workplaces
Wood-dust extraction in joinery; welding fume extraction in fabrication shops; soldering extraction in electronics; paint spray booths; flour dust extraction in bakeries; laboratory fume cupboards; isocyanate paint booths; pharmaceutical compounding isolators; vehicle exhaust extraction in MOT bays; nail bar extraction. Anywhere the COSHH risk assessment concludes engineering controls are needed.
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How COSHH links to LEV
COSHH Regulation 7 requires employers to prevent or adequately control exposure. Regulation 9 requires any engineering control — including LEV — to be examined and tested at least every 14 months by a competent person, with the report retained for five years. See LEV testing & the TExT procedure →
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Frequently asked questions
What does LEV stand for?
LEV stands for Local Exhaust Ventilation. It is an engineering control that captures airborne contaminants — dust, fume, mist, vapour, gas — at or close to their source, before they reach the worker's breathing zone.
When does the law require LEV?
The Control of Substances Hazardous to Health Regulations 2002 (COSHH) require employers to control exposure to hazardous substances. Where the risk assessment shows that elimination, substitution or process change cannot reduce exposure below the Workplace Exposure Limit, engineering controls — typically LEV — are required.
What's the difference between LEV and general ventilation?
General ventilation dilutes contaminants across the whole workspace; LEV captures them at source. For most COSHH-listed substances, dilution alone cannot achieve the Workplace Exposure Limit, so LEV is mandatory.
How do I know if my LEV is working?
Visual indicators (capture velocity at the hood, smoke testing, dust visibility) suggest performance; the legally required Thorough Examination and Test (TExT) under COSHH Regulation 9 measures it. Both are needed.