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Ventilation hygiene - TR19 Air
Most talk of duct cleaning is about grease and kitchen extract. But the air being blown into your building travels through supply ductwork and an air handling unit too - and that side has its own standard, its own concern, and its own reasons to be clean.
The short answer
TR19 Air is the BESA standard for the internal cleanliness of general ventilation systems - the supply ductwork and air handling units (AHUs) that deliver air into occupied spaces. Its concern is air quality and system hygiene, not fire, and it classifies required cleanliness by how the space is used - high, medium or low - drawing on BS EN 15780. It is the counterpart to TR19 Grease, which covers greasy kitchen extract for fire safety; the two address different systems for different reasons.
The distinction
When people say duct cleaning they usually mean kitchen extract - the greasy ductwork carrying air away from the cookline, cleaned to TR19 Grease for fire safety. But that is only one part of a building's ventilation. The other part is the supply and general ventilation: the ductwork and air handling units that draw in, condition and deliver fresh air into the offices, dining rooms and occupied spaces. That side carries no grease, but it is not exempt from needing to be clean.
TR19 Air is the standard for that other side. It covers the internal cleanliness and hygiene of general ventilation systems - supply ductwork, extract that is not greasy kitchen extract, and the air handling units that serve them. Where TR19 Grease is about fire, TR19 Air is about the quality of the air the system delivers and the hygiene of the system itself. Recognising that these are two distinct standards for two distinct jobs is the first step to knowing what your building actually needs.
The concern
The reason to clean supply ductwork and an AHU is different from the reason to clean kitchen extract. Over time, dust and debris accumulate inside ventilation ductwork and within the air handling unit - on filters, coils and internal surfaces. That accumulation degrades the air being delivered into occupied spaces, can support microbial growth in the damp parts of an AHU, and reduces how effectively the system ventilates. The concern is the health and comfort of the people breathing that air, and the performance of the system.
An AHU in particular is where much of this concentrates, because it is where air is filtered, heated or cooled and moved - so it collects dust, holds moisture, and can become a source of contamination rather than a supply of clean air if neglected. Cleaning it and the supply ductwork to TR19 Air keeps the delivered air clean and the system working as designed. It is a health, comfort and efficiency matter, where TR19 Grease is a fire-safety one.
The classification
TR19 Air does not demand the same cleanliness everywhere - it classifies the required standard by how the ventilated space is used, drawing on the classification in BS EN 15780. The idea is that a system serving a highly sensitive space needs a higher cleanliness standard than one serving a space where air purity matters less. So the required class is matched to the use, rather than applying one blanket level to every duct in every building.
In broad terms, a system serving a highly sensitive environment - an operating theatre or a laboratory, for instance - falls into a high classification; general occupied spaces such as offices and living areas typically sit at a medium classification; and infrequently occupied spaces such as a store or plant room fall into a low classification. The classification then sets how clean the ductwork has to be and, in turn, informs how it is assessed and how often it is likely to need attention. Matching the standard to the use is what makes TR19 Air proportionate.
Why it matters
For a premises with a commercial kitchen, the practical upshot is that it likely needs both standards, applied to different systems. The kitchen extract needs TR19 Grease, because that is where the grease and the fire risk are. The general ventilation serving the dining area, offices and other occupied spaces - the supply ductwork and AHU - needs TR19 Air, because that is where the air-quality and hygiene concern sits. They are not alternatives, and one does not cover the other.
Assuming a kitchen extract clean has dealt with the whole building's ventilation is a common gap - it leaves the supply side and the AHU unaddressed, quietly degrading the air delivered into the occupied spaces. Understanding that TR19 Air is a separate standard for a separate system is what lets a building look after both sides of its ventilation properly: the greasy extract for fire, and the supply and AHU for the air the people in the building actually breathe.
The takeaway
TR19 Air, in brief, is the standard for keeping general ventilation clean - supply ductwork and air handling units - for the sake of air quality and system hygiene, with the required cleanliness classified by how the space is used under BS EN 15780. It is the counterpart to TR19 Grease, which handles greasy kitchen extract for fire safety. Same family of ventilation hygiene, two different concerns.
For most buildings with a kitchen, both apply, to different systems. The extract needs cleaning for fire; the supply and AHU need cleaning for the air they deliver. Knowing the difference means neither side gets neglected on the assumption that the other was covered - and the people in the building get both a lower fire risk and cleaner air, which are two genuinely separate benefits from two genuinely separate pieces of work.
Questions
The BESA standard for the internal cleanliness of general ventilation systems - supply ductwork, non-greasy extract, and air handling units that deliver air into occupied spaces. Its concern is air quality and system hygiene, not fire.
TR19 Grease covers greasy kitchen extract and is about fire safety. TR19 Air covers general ventilation and is about air quality and hygiene. They address different systems for different reasons - a building often needs both.
TR19 Air classifies the required cleanliness by how the space is used - high, medium or low - drawing on the classification in BS EN 15780, so the standard is matched to the use rather than applied as one blanket level everywhere.
An air handling unit filters, conditions and moves air, so it collects dust and holds moisture on filters and coils. Neglected, it can become a source of contamination rather than clean air, degrading what is delivered into occupied spaces.
Broadly, highly sensitive spaces like operating theatres or laboratories are high; general offices and living areas are typically medium; infrequently occupied spaces like stores or plant rooms are low. The class sets how clean the ductwork must be.
No. Kitchen extract is cleaned to TR19 Grease for fire; the supply ductwork and AHU are cleaned to TR19 Air for air quality. Assuming one covers the other leaves the supply side and AHU unaddressed, degrading the air delivered into the building.
We clean supply ductwork and air handling units to TR19 Air, matched to how each space is used - so the air your building delivers is cared for, not just its greasy extract.
