Phoenix Journal · LEV Testing
Three words, three jobs - and mixing them up is how kitchens end up over-served in one place and dangerously under-protected in another. Here is what separates ventilation, extraction and LEV.
Air, and what we ask of it
Stand in a busy commercial kitchen at the height of service and you are surrounded by three different jobs happening at once, even though most people would call all of it "the extraction".
Fresh air is being pushed in somewhere near the door to keep the room breathable. A canopy over the range is dragging heat, steam and grease-laden vapour straight up and out. And, in a room off to the side where someone is decanting cleaning chemicals or running a small workshop task, a little hood on a flexible arm is quietly catching fumes at the exact point they are created. Same building, same air, three completely different design intentions - and the words we use for them get swapped around so casually that it causes real confusion when something goes wrong.
It matters because the standards, the testing regimes and the legal duties attached to each one are not the same. Call your grease extract an "LEV system" to the wrong person and you will either be sold a test you do not strictly need, or worse, reassured that a statutory examination has been done when it has not. So it is worth slowing down and being precise about what each term actually means, and where the lines between them sit.
The cleanest way to separate these ideas is to ask what problem the air movement is solving. General ventilation treats the whole room as the thing to manage. Local extraction treats a specific source as the thing to manage. That single distinction sits underneath almost everything else.
General ventilation is about the volume of the space. You are supplying fresh air and removing stale air so that heat, humidity, odours and background contaminants are diluted to comfortable, safe levels across the room as a whole. It is deliberately broad - it does not care much where a problem starts, only that the average condition of the air stays acceptable. In a commercial kitchen this is the make-up air side of the equation, and it is closely tied to the extract. Under BESA's DW/172, the UK specification for kitchen ventilation systems, a mechanical make-up air supply is designed to replace up to a maximum of 85% of the total extracted volume, with the remaining share infiltrating naturally from surrounding areas. Get that balance wrong and the room goes into heavy negative pressure - doors become hard to open, fans work against themselves, and the canopy cannot pull properly.
Extraction is more purposeful. Rather than diluting, it captures contaminated air close to where it is generated and carries it out of the building through ductwork. Commercial kitchen canopy extract is the classic example: the hood sits directly over the cooking line, collects the grease-laden vapour and combustion products, and moves them through the duct system to discharge. Because that grease then coats the inside of the ductwork, extraction carries its own maintenance regime - TR19 Grease governs how those internal surfaces are cleaned and to what standard, working hand in hand with DW/172, which governs how the system was designed and built with access and fire safety in mind. Extraction and ventilation are two ends of the same conversation, and it is genuinely useful to keep the supply, extract and any recirculated portion straight in your head.
Here is the part most people miss. LEV is not a fourth type of air system sitting apart from the others - it is a specific, legally meaningful category of extraction. Local Exhaust Ventilation is engineered controlled extraction whose whole purpose is to protect health by capturing a hazardous substance at source before anyone can breathe it in. When extraction crosses into that territory, a set of duties switches on.
The trigger is the substance, not the fan. If a process releases something hazardous to health - dust, mist, vapour, fume, gas - and you have installed engineering controls to capture it at source, you are almost certainly running LEV under the Control of Substances Hazardous to Health Regulations. A typical LEV system has the same anatomy people recognise from extraction: a capture hood, ducting, an air cleaner or filter, and a fan discharging outside. HSE's guidance HSG258 sets out how these systems should be designed and assessed so that the control actually works in practice, considering the process, how the contaminant behaves, and whether the hood is close enough to do its job. A pot-wash steam canopy is ventilation. A grease canopy is extraction. A hood over a bench where staff decant solvents or handle a dusty ingredient can be LEV - because now it is standing between a person and a health hazard.
Once a system is LEV, COSHH Regulation 9 requires a Thorough Examination and Test - often shortened to TExT - at least once every 14 months for most processes, and more frequently for higher-risk ones. That is a legal maximum interval, not a recommended best practice for every setting. The examination is far more than a quick look: a competent engineer, typically holding BOHS-recognised qualifications such as P601, will measure airflows and capture velocities, check duct velocities, filter condition and fan performance, and judge whether the system is genuinely controlling exposure. Records must be kept for at least five years. The reason the distinction matters so much is that no amount of general ventilation cleaning or grease-duct work discharges the LEV duty - they are different obligations, and only the thorough examination satisfies the law.
So when you hear the three words used interchangeably, it is worth mentally sorting them by intent. Ventilation keeps the room liveable. Extraction removes a defined stream and sends it outside. LEV is extraction with a health-protection job and a legal test attached. A neglected grease extract that is straining against poor make-up air will cost you in fouling and running costs, which is a real problem in its own right - our note on the link between dirty extraction and higher energy bills covers that side. But a neglected LEV system exposes people and breaches the regulations, and that is a line no operator wants to be found on the wrong side of.
Questions
Usually not by default. A standard grease extract canopy over a cooking line is extraction managed under DW/172 for design and TR19 Grease for cleaning, rather than LEV. It becomes an LEV system when its purpose is to capture a substance hazardous to health at source - for example a hood over an area where staff decant chemicals or handle dusty ingredients. If that applies, COSHH Regulation 9 requires a Thorough Examination and Test at least every 14 months.
Ventilation manages the whole room by diluting heat, moisture and odours with fresh air to keep conditions comfortable and safe on average. LEV, or Local Exhaust Ventilation, does the opposite of diluting - it captures a specific health hazard right at the point it is released, before anyone can breathe it in. Because LEV protects health, it carries legal duties under COSHH, including regular thorough examination and testing, which general ventilation does not.
Phoenix Duct Clean · by the numbers
Phoenix examines and tests local exhaust ventilation to HSG258 and COSHH - measured, reported and certificated, UK-wide.