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Ventilation hygiene - offices
An office has no cookline and no grease, so it is easy to assume its ventilation looks after itself. It does not. Dust, debris and the slow fouling of the system degrade the air people breathe all day - and that has its own standard, and its own reasons to be cleaned.
The short answer
Office ventilation carries dust and debris rather than grease, but it still fouls over time and degrades the air delivered into the workspace. There is no single interval - the right frequency depends on how the space is used and how quickly the system fouls, and the required cleanliness is classified by use under TR19 Air, drawing on BS EN 15780. General offices typically sit at a medium classification. The point is to keep the delivered air clean and the system performing, on a cycle matched to the building.
Why it needs cleaning at all
It is a natural assumption that office ventilation, with no cooking and no grease, does not need cleaning the way a kitchen extract does. But ventilation ductwork and the air handling units serving an office accumulate their own load over time - dust, debris, and the general fouling that any system moving large volumes of air collects on its filters, coils and internal surfaces. It is slower and cleaner than grease, but it still builds, and it still has effects.
Those effects are about the air people breathe and the system's performance. Dust and debris in the ductwork degrade the quality of the air delivered into the workspace, can support microbial growth in the damp parts of an air handling unit, and reduce how effectively the system ventilates. An office full of people relies on that ventilation for fresh, clean air all day - so a fouled system is quietly delivering worse air to everyone in the building, which is reason enough to keep it clean.
The standard
Office ventilation falls under TR19 Air, the standard for the internal cleanliness of general ventilation systems, as opposed to TR19 Grease which covers kitchen extract. TR19 Air does not set one blanket cleanliness level for everywhere - it classifies the required standard by how the space is used, drawing on the classification in BS EN 15780, so a system serving a more sensitive space is held to a higher standard than one serving a less sensitive one.
For a general office, that classification is typically medium - below the high standard required for something like an operating theatre or laboratory, but above the low standard for an infrequently occupied store or plant room. The classification matters because it sets how clean the ductwork has to be and informs how it is assessed and how often it is likely to need attention. So office ventilation has a defined, use-appropriate cleanliness standard to be kept to, not just a vague sense that it should be clean.
What drives frequency
The right cleaning frequency for office ventilation is set by the building rather than a universal number. How the space is used and how densely it is occupied matter - a busy, full office generates and circulates more dust than a lightly used one. The local environment matters too: a system drawing air in a dusty or polluted area fouls faster than one in a clean setting. And the condition and design of the system itself affects how quickly debris accumulates to a level that needs clearing.
So the honest approach is to match the interval to the actual system and its use, rather than quoting a single figure. The way to know is assessment - inspecting the ductwork and the air handling unit to see how fouled they are against the cleanliness the space's classification requires, and cleaning when they approach or exceed that level. That keeps the frequency proportionate: a system that fouls slowly is cleaned less often, one that fouls quickly more often, each judged against its proper standard.
The air handling unit
Within an office ventilation system, the air handling unit deserves particular attention, because it is where the conditioning happens and where much of the fouling concentrates. The AHU draws in, filters, heats or cools and moves the air, so it collects dust on its filters and coils and holds moisture in its damp sections. Neglected, it can shift from being the source of clean, conditioned air to a source of contamination in its own right - which undermines the whole point of the ventilation.
So cleaning office ventilation is not only about the ductwork but about the AHU that feeds it. Keeping the unit's filters, coils and internal surfaces clean maintains the quality of the air it delivers and keeps it working efficiently - a fouled AHU also has to work harder, using more energy, to move air through clogged filters and coils. Attending to the AHU as well as the ducting is what keeps both the air quality and the efficiency of the office ventilation where they should be.
The takeaway
Office ventilation should be cleaned on a cycle set by how the space is used and how fast the system fouls, judged against the cleanliness its TR19 Air classification requires - typically medium for a general office. There is no universal interval, because a busy office in a dusty setting fouls faster than a quiet one in a clean one, and the right frequency follows that reality.
The reason to do it at all is the air people breathe all day and the system's performance - both of which a fouled system quietly degrades, grease or no grease. Assessing the ductwork and the air handling unit against the required standard, and cleaning when they approach it, keeps the frequency proportionate and the air clean. Office ventilation looks after the whole workforce's air supply, which is exactly why it should not be left to look after itself.
Questions
On a cycle set by how the space is used and how fast the system fouls - there is no universal interval. The required cleanliness is classified by use under TR19 Air, with general offices typically at a medium classification.
Because dust and debris still build up in the ductwork and air handling unit, degrading the air delivered into the workspace, supporting microbial growth in damp AHU sections, and reducing how well the system ventilates.
TR19 Air, the standard for the internal cleanliness of general ventilation - as opposed to TR19 Grease for kitchen extract. It classifies the required cleanliness by use, drawing on BS EN 15780, with offices typically medium.
How the space is used and how densely it is occupied, the local environment the system draws air from, and the condition and design of the system - all of which affect how fast dust and debris accumulate to a level needing clearing.
Because it filters, conditions and moves the air, so it collects dust on filters and coils and holds moisture - and neglected it can become a source of contamination rather than clean air, as well as using more energy to run.
By assessment - inspecting the ductwork and AHU to see how fouled they are against the cleanliness the space's classification requires, and cleaning when they approach or exceed that level. That keeps the frequency proportionate to the building.
We clean office and general ventilation - ductwork and air handling units - to TR19 Air, matched to how your space is used, for cleaner air and an efficient system.
