What is LEV, and what counts as Local Exhaust Ventilation?

Ask most people what LEV means, and you'll get a blank stare like a mechanical engineer looking at modern art. Ask them what a fume cupboard is, and they'll have a decent chance of getting somewhere. That gap matters, because Health and Safety Executives use the term LEV, while lab technicians name each piece of equipment individually. But while LEV may seem like another arbitrary reference to a fume hood or biosafety cabinet, it covers much more equipment than most people recognise.

Local exhaust ventilation isn't niche terminology reserved for compliance officers or subject matter experts. If you specify, install or operate anything that removes fumes, dust or vapour from the air, you're working with LEV. “But Aaron, if that’s the case, how is LEV different from general ventilation?” Well, let’s find out.

What is LEV (and how is it different from ventilation)?

LEV stands for local exhaust ventilation. In simple terms, it's any engineering control that captures a contaminant at the point it's created and removes it before it spreads into the room. Fumes, dust, vapour and mist all fall within this umbrella. It doesn't matter what form the hazard takes. If the equipment captures it at the source and removes it, that's LEV.

Compare that to general ventilation, which is a different job entirely. General ventilation dilutes whatever’s in the room by mixing it with fresh air. It doesn't target the source or remove the hazard. It just decreases the ppm (parts per million), essentially spreading it thinner. Think of the difference between mopping up a spill and opening a window and hoping the smell goes away. One deals with the problem, while the other manages the symptoms, albeit not very effectively.

However, HSE doesn’t treat LEV as a nice-to-have byproduct of good airflow design. It’s a control measure with its own legal obligations. This is why the term frequently appears in COSHH guidelines rather than being swapped for a more generic term like extraction.

What counts as LEV equipment in a lab?

Now, here’s the most common mistake. Say LEV out loud in a lab, and most people might think you’re talking about fume cupboards. That’s fair enough. It’s the most visible example. But it’s one piece of equipment among several.

Ducted and ductless fume cupboards are LEV. So are walk-in fume cupboards, wet scrubbing systems, extraction arms, and the ductwork that connects them to a roof-mounted exhaust stack. Class I and Class II biosafety cabinets also qualify as LEV. Why? Because both systems draw air away from the operator and filter it before exhaust. Which, not coincidentally, is precisely the job LEV is meant to do.

But what doesn't qualify is just as important. Take a laminar flow cabinet, for example. Yes, it protects the sample, but not the operator standing in front of it. So, it doesn’t qualify as LEV. It pushes filtered air outward to keep the work surface clean, not to prevent contamination inside the lab or keep the operator safe. Mixing these up could have disastrous consequences. You may end up with a lab that looks fully protected on paper, but with equipment that serves an entirely different purpose.

If it pulls contaminated air away from a person and filters or exhausts it before it circulates, you're talking about LEV. That's the test to apply, not whether the equipment happens to have a fume cupboard label written on it.

Why LEV matters

Airborne exposure doesn't announce itself. Nobody collapses the first time they breathe in a low dose of something they shouldn't. The damage tends to be cumulative, which is exactly what makes it dangerous. Occupational lung disease, chemical sensitisation and long-term respiratory damage are still among the most common outcomes of poorly controlled lab environments. In most cases, the equipment that should have stopped it was missing, unsuitable, or simply not doing its job, and this is why the terminology matters.

LEV exists to stop exposure where it’s prone, rather than relying on the room to dilute it to something survivable. Get the specification wrong, whether it’s the wrong airflow, the wrong cabinet, or ductwork not sized for the appropriate load, and the risk doesn't go away. It just becomes invisible, which in a laboratory is far worse than a risk everyone can see.

LEV testing: the legal requirement

LEV testing isn't optional, and it’s not something you quietly deprioritise when budgets tighten. COSHH Regulation 9 places a legal duty on employers to keep LEV equipment in efficient working order, enforced through examination and testing carried out by a competent person. Not a self-assessment by whoever's free that week.

HSG258 is the HSE's own guidance on what that testing should look like in practice, and it's worth knowing, even if you never read it cover to cover. Why? Because it's exactly what an inspector will reference if your paperwork doesn't add up.

What the test involves and how often it needs to happen depends entirely on the equipment. For fume cupboards specifically, we've covered the details, the standards and the intervals in our guide to fume cupboard servicing. The short version is simple: if you're using LEV, you have a legal duty to have it tested, and that isn't a grey area.

What are the most frequently asked questions on LEV?

Here are a few FAQ’s worth remembering:

What does LEV stand for?

LEV stands for local exhaust ventilation, the term the HSE uses for any engineering control that captures a contaminant at source and removes it before it reaches the person working near it.

Is LEV testing a legal requirement?

Yes, and it isn't up for debate. COSHH Regulation 9 requires LEV equipment to be thoroughly examined and tested, typically by a competent person working to HSG258.

How often does LEV need to be checked?

That depends on the equipment and what it's controlling. For fume cupboards specifically, our servicing guide covers the interval and what the test involves in full.

What is the purpose of LEV?

To protect the person working near a hazard by removing the contaminant before it reaches their breathing zone, rather than leaving the room to dilute it down over time.

LEV systems from TION

At TION, LEV isn't a single product; it's a category we design around. Fume cupboards, biosafety cabinets, extraction arms and the ductwork that ties a laboratory's extraction systems together all sit in the same classification. To capture the hazard at the source and protect the person standing in front of it. We build products that still perform in five years, as they did on day one.

If you're specifying LEV equipment for a new lab or trying to work out whether your existing setup still does the job, get in touch with our team, and we'll talk it through.

Final thoughts: LEV isn't a niche acronym for compliance teams to worry about. It's the umbrella your fume cupboard, biosafety cabinet, and half the extraction hardware in your building should already comply with. Know what counts as LEV; know that testing it is a legal duty and not a courtesy. Understand the risks and make that knowledge accessible. More importantly, remember that the equipment doesn't need you to call it LEV. The law does.