What Does LEV Stand For? Local Exhaust Ventilation Explained

LEV stands for Local Exhaust Ventilation. It's an engineering control that captures airborne contaminants — dust, fume, vapour, mist — at or near the point where they're generated, before they reach a worker's breathing zone.

That's the textbook definition. In practice, LEV is the extraction arm above a welding bench, the dust hood on a table saw, the fume cupboard in a dental lab, the ventilation unit at a nail station. If your business creates airborne substances that could harm people's lungs, an LEV system is likely how you're required to control them.

How LEV Systems Work

LEV is a means of controlling airborne contaminants at source, removing them before they can spread into the wider workplace. Every LEV system follows the same basic sequence: capture, transport, clean, discharge. The components differ between a woodworking dust extractor and a laboratory fume hood, but the engineering principle is identical.

1. Capture — the hood or inlet

The hood is the business end. It's positioned at the source of contamination — over a workbench, around a sanding machine, at the opening of a spray booth. Its job is to capture contaminated air before it disperses into the room. Hood design matters enormously. A well-designed hood positioned correctly will capture contaminants efficiently. The same hood positioned 30 cm too far from the source may capture almost nothing.

HSG258 describes several hood types: enclosing hoods (which surround the source), receiving hoods (which catch contaminants already in motion, like rising hot fumes), and captor hoods (which pull contaminants towards them against still air). Each suits different situations.

2. Transport — the ductwork

Ductwork carries contaminated air from the hood to the air cleaning equipment. The design has to maintain sufficient transport velocity — fast enough to keep particles airborne and moving through the system rather than settling and blocking the ducts. For most dusts, that means air speeds of at least 15-20 metres per second in the duct.

Ductwork problems are common. Holes, loose joints, crushed sections, and poorly designed bends all reduce system performance. A 10% air leak in the ductwork between the hood and the fan can cut capture velocity at the hood significantly.

3. Clean — the air cleaning equipment

Before air is discharged, contaminants need to be removed. The cleaning method depends on what you're capturing:

• Particulate filters and bag collectors — for dust (wood, metal, flour, stone)
• HEPA filters — for fine or hazardous particles
• Activated carbon filters — for vapours and gases
• Wet scrubbers — for certain chemicals and mists

Filter maintenance is critical. A clogged filter increases resistance across the system, reduces airflow, and degrades capture performance at the hood — the exact point where it matters most.

4. Discharge — the exhaust

Cleaned air is either discharged outside the building or, in some recirculating systems, returned to the workspace. External discharge is more common and generally simpler. Recirculating systems need additional safeguards — continuous monitoring to ensure the cleaning stage is working properly, because if it fails, contaminated air goes straight back into the room.

The discharge point must be positioned so that expelled air doesn't re-enter the building through windows, doors, or other air intakes.

Common LEV Types and Where They're Used

LEV isn't just found in factories. These systems operate across a wide range of UK workplaces.

LEV type	Common in	What it captures
Dust extraction (fixed hoods, on-tool extraction)	Woodworking, stonemasonry, manufacturing	Wood dust, silica dust, metal swarf, general particulate
Fume cupboards / fume hoods	Laboratories, dental labs, education	Chemical vapours, solvent fumes, resin dust
Spray booth ventilation	Automotive bodyshops, painting, coating	Paint mist, solvent vapour, isocyanates
Welding fume extractors (fixed or portable arms)	Fabrication, engineering, construction	Welding fume (metal oxides, gases)
Kitchen extraction	Commercial kitchens, bakeries	Cooking fumes, flour dust, cleaning chemical vapour
Dental suction	Dental practices	Aerosols, dust from drilling and polishing
Nail bar ventilation	Nail salons, beauty salons	Acrylic dust, solvent vapour (methacrylates, acetone)
Pharmaceutical extraction	Pharmaceutical manufacturing, compounding	Drug dust, powder aerosols

The HSE's work-related lung disease programme drives enforcement activity across many of these sectors. Occupational lung disease remains one of the biggest causes of work-related ill health in the UK, and inadequate LEV is a primary contributing factor.

LEV vs General Ventilation — What's the Difference?

This distinction matters because the legal requirements are different.

General ventilation moves air through an entire room. Opening a window, running a ceiling fan, or operating an HVAC system are all forms of general ventilation. It dilutes contaminants by mixing them with clean air across the whole space. It doesn't capture anything at source.

Local exhaust ventilation captures contaminants at the point of generation, before they enter the wider room air. It extracts rather than dilutes.

General ventilation is suitable for low-risk situations — controlling background odours, maintaining comfortable temperatures, providing fresh air. It is not suitable as the primary control for hazardous substances. If your COSHH assessment identifies airborne substances that could cause harm, general ventilation alone almost certainly won't be adequate. You'll need LEV, or an equivalent engineering control, to capture contaminants at source.

A workshop that relies on "leaving the roller door open" for ventilation is using general ventilation. It might feel like it's working — you can't see dust in the air, it doesn't smell too bad. But airborne contaminants at harmful concentrations are often invisible and odourless. Wood dust at the workplace exposure limit of 3 mg/m3 is barely visible. By the time you can see a dust cloud, concentrations are likely many times above the limit.

When Do You Legally Need an LEV System?

There's no single regulation that says "you must install LEV." Instead, the requirement flows from your COSHH assessment.

The Control of Substances Hazardous to Health Regulations 2002 require every employer to assess the risks from hazardous substances in the workplace (Regulation 6) and then provide adequate control measures (Regulation 7). COSHH sets out a hierarchy of controls:

1. Eliminate the hazardous substance entirely
2. Substitute it with something less harmful
3. Enclose the process so substances can't escape
4. Engineering controls — this is where LEV sits
5. Administrative controls and PPE (personal protective equipment) — the last resort

If you can't eliminate or substitute the substance, and full enclosure isn't practical, LEV is the next step. PPE (dust masks, respirators) should only be relied on when engineering controls like LEV aren't reasonably practicable, or as a supplement while LEV is being installed or repaired.

In practical terms, if your workers are exposed to wood dust, welding fume, silica dust, flour dust, solvent vapour, or any other substance with a workplace exposure limit, and you can't eliminate the source, you almost certainly need LEV.

Legal Requirements Once You Have LEV

Once an LEV system is in place as a COSHH control measure, specific legal requirements apply:

• Maintain the system in efficient working order, efficient working condition, and good repair — an ongoing duty (COSHH Regulation 9)
• Thorough examination and test (TExT) at intervals not exceeding 14 months — carried out by a competent person with calibrated instruments
• Keep records of every examination for at least 5 years — available for HSE inspectors on request
• User checks — daily or weekly inspections by trained staff to confirm the system is working between formal examinations. You can do these yourself

These duties apply to every employer operating LEV, regardless of business size or sector. A two-person nail salon has the same legal framework as a 200-employee manufacturing plant.

The HSE ran 4,000 targeted dust inspections in 2024/25. Missing TExT reports, overdue examinations, and absent user check records are among the most common findings. Fines for COSHH breaches can reach six figures, and directors can face personal liability.

Getting Started

If you're reading this because you've just discovered you might need an LEV system — or because you've got one and aren't sure you're managing it properly — here's the sequence:

1. Check your COSHH assessment. Does it identify airborne hazards? Does it specify LEV as a control measure? If you don't have a COSHH assessment, that's the first problem to solve.
2. Identify your LEV systems. List every piece of local exhaust ventilation on your premises. Include systems you might not think of as "LEV" — dental suction, nail station ventilation, kitchen extraction.
3. Check your TExT status. When was each system last examined? Is it within the 14-month window? Use our LEV testing due date calculator to check.
4. Set up user checks. Create a simple checklist for daily or weekly inspections. Our compliance checklist generator builds a sector-specific checklist for your LEV type.
5. Organise your records. Gather your TExT reports and user check logs. Check for gaps. The record-keeping requirements checker can identify what you might be missing.

LEV isn't complicated technology. It's a hood, some ductwork, a fan, and a filter. The challenge is managing it consistently — keeping checks on schedule, records organised, and examinations within the 14-month deadline. LEVproof will be a digital compliance tool built for exactly this. Join the waitlist for early access.

Sources

• HSG258: Controlling airborne contaminants at work — HSE
• Control of Substances Hazardous to Health Regulations 2002 (COSHH) — legislation.gov.uk
• Local exhaust ventilation (LEV) guidance — HSE
• LEV guidance for employers — HSE
• COSHH main page — HSE
• Work-related lung disease — 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.