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Ventilation - the concepts
Three words that get used as if they were the same thing - ventilation, extraction, LEV - and are not. They describe different systems, doing different jobs, held to different standards. Knowing which is which tells you what you actually have, and what it needs.
The short answer
General ventilation moves air through a space for comfort and air quality - supplying fresh air and removing stale. Kitchen extraction is the specific system removing hot, grease-laden air from over a cookline, where the concern is grease and fire. LEV - local exhaust ventilation - captures a contaminant like dust, fume or vapour at the point it is generated, in workshops and industrial settings, before a worker breathes it. Three different jobs, held to different standards, which is why the words are not interchangeable.
Why it matters
In everyday use, ventilation, extraction and LEV get thrown around loosely, as if they all just mean moving air about. But they refer to genuinely different systems with different purposes, and treating them as interchangeable causes real confusion - about what a building has, what it needs, and which standard applies to it. Getting the concepts straight is the foundation for making sense of everything else, because the right cleaning, testing and standard all depend on which of these you are actually talking about.
The clearest way to separate them is by what each is trying to achieve. General ventilation is about the overall air in a space. Kitchen extraction is about removing a specific, greasy exhaust from a cookline. LEV is about capturing a specific contaminant at the exact point it is produced. Once the purpose is clear, the differences in how they work, and how they are looked after, follow naturally - and the words stop being interchangeable and start pointing at distinct things.
General ventilation
General, or comfort, ventilation is the broadest of the three. Its job is to keep the air in an occupied space fresh and comfortable - supplying fresh air, removing stale air, and often heating or cooling it - across offices, shops, dining rooms and other spaces where people spend their time. It works on the whole volume of air in the space rather than targeting any one source, diluting and replacing the air generally to keep it acceptable to breathe and comfortable to be in.
Because its concern is general air quality and comfort, the standard that applies to keeping it clean is TR19 Air, the ventilation-hygiene standard for the internal cleanliness of general ventilation systems. The contaminant of concern is the dust and debris that accumulate in the ductwork and air handling units over time, degrading the air delivered. General ventilation is not about grease or about any single point source - it is about the overall air a space provides to everyone in it.
Kitchen extraction
Kitchen extraction is a specific kind of extract system with a specific problem: the air coming off a commercial cookline is hot, laden with grease, and full of cooking fumes, and it has to be removed from over the cooking equipment and taken out of the building. The canopy, filters, ductwork and fan that do this make up the kitchen extraction system, and what sets it apart is grease - the extracted air carries combustible grease that builds up inside the system.
That grease is why kitchen extraction has its own concern and its own standard. The build-up of grease in the ductwork and fan is a fire risk, so the standard that applies is TR19 Grease, which is about cleaning that grease out to control fire. Kitchen extraction is not general ventilation - it targets one greasy source rather than the whole space - and it is not LEV in the industrial sense; it is its own category, defined by grease and fire, sitting under the grease standard rather than the air one.
LEV
LEV - local exhaust ventilation - is different again, and the word local is the key to it. Rather than treating the whole space like general ventilation, or removing a greasy exhaust like kitchen extraction, LEV captures a specific hazardous contaminant right at the point it is generated, before it can spread into the air a worker breathes. A hood over a woodworking machine drawing away sawdust, an arm capturing welding fume, a booth containing paint spray - these are LEV, catching the contaminant at source.
Its concern is worker health: LEV controls exposure to hazardous dust, fume, vapour and mist in workshops and industrial settings, and because of that it is held to the health-based regime - it must be thoroughly examined and tested, typically at least every fourteen months, to prove it is controlling exposure. LEV is about a point source of a health hazard, captured locally. That distinct purpose - protecting workers from a specific contaminant at its source - is what separates it from both general ventilation and kitchen extraction.
The takeaway
Ventilation, extraction and LEV are three different things. General ventilation moves air through a space for comfort and air quality, and is cleaned to TR19 Air. Kitchen extraction removes hot, grease-laden air from a cookline, and is cleaned to TR19 Grease for fire safety. LEV captures a hazardous contaminant at the point it is generated to protect workers, and is examined and tested on the health regime. Different jobs, different concerns, different standards.
Knowing the difference is what lets you say precisely what a building has and what each part needs. A single premises might have all three - general ventilation for its offices, kitchen extraction for its kitchen, and LEV for a workshop - each looked after under its own standard. Using the words interchangeably blurs that; using them precisely is the first step to making sure each system gets the right care. Three words, three distinct things.
Questions
They are three different systems. General ventilation moves air through a space for comfort and air quality; kitchen extraction removes greasy air from a cookline for fire safety; LEV captures a hazardous contaminant at source to protect workers. Different jobs and standards.
The system that keeps the air in an occupied space fresh and comfortable - supplying fresh air, removing stale, often heating or cooling. It works on the whole volume of air, not a point source, and is cleaned to TR19 Air.
It targets one greasy source - the hot, grease-laden air off a cookline - rather than the whole space, and the grease it carries is a fire risk. That is why it has its own standard, TR19 Grease, focused on cleaning grease out to control fire.
Local exhaust ventilation - a system that captures a specific hazardous contaminant like dust, fume or vapour at the point it is generated, before a worker breathes it. Its concern is worker health, and it is examined and tested typically at least every fourteen months.
Yes. A single premises might have general ventilation for its offices, kitchen extraction for its kitchen, and LEV for a workshop - each a different system looked after under its own standard. That is exactly why the words are not interchangeable.
General ventilation is cleaned to TR19 Air; kitchen extraction to TR19 Grease; and LEV is thoroughly examined and tested on the health regime. Knowing which system you have tells you which standard applies to looking after it.
We clean general ventilation to TR19 Air and kitchen extract to TR19 Grease, and test LEV on the health regime - the right care for each of the three, whichever you have.
