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Ductwork - three types
Ductwork all looks similar, but it is not all the same job. A greasy kitchen extract, a general ventilation duct and a laundry lint duct each carry a different substance, a different risk, and a different cleaning need. Treating them all the same - or assuming one clean covers them - misses what each actually requires.
The short answer
Ductwork comes in kinds that need treating differently. Kitchen grease extract carries combustible grease - a fire risk, cleaned to the TR19 Grease standard. General dry ventilation carries dust and debris - an air-quality and hygiene concern, cleaned to the TR19 Air standard. Laundry ducts carry lint - a combustible fire risk, cleaned to control that. Each has a different substance, a different risk, and a different cleaning basis, so knowing which kind of duct you have tells you what its clean actually needs to address.
Ductwork is not all one thing
It is easy to think of ductwork as a single category - metal ducting carrying air - and assume it all needs much the same cleaning. But different ducts carry different substances, and the substance is what determines the risk and the cleaning need. A kitchen extract carries grease; a general ventilation duct carries dust; a laundry duct carries lint. These are genuinely different materials with different properties, so the ducts that carry them present different risks and require different cleans, despite looking broadly similar.
So knowing what kind of duct you are dealing with is the starting point for knowing how to look after it. The three common kinds - grease (kitchen extract), dry (general ventilation) and laundry (lint) - each need to be understood on their own terms, because what makes each a risk, and what cleaning each needs, differs. Assuming they are interchangeable, or that a clean of one covers another, misses the specific concern each carries. Three kinds of duct means three risks and three cleans, and telling them apart is how each gets treated correctly.
Grease ductwork
Kitchen grease extract ductwork carries the hot, grease-laden air from the cookline, so the substance building up in it is combustible grease. That makes its risk fire: grease accumulating in the ductwork is a concentrated fuel connected to the flames, and a path for fire to spread through the building. This is the most serious of the three risks, because grease is highly combustible and sits in a system directly connected to ignition.
So grease ductwork is cleaned to control fire risk, to the TR19 Grease standard - the recognised specification for managing the fire risk of grease accumulation in kitchen extract, with its measurable grease limits and verification. The whole point of cleaning it is fire safety: removing the combustible grease from the system to control the fire risk. This is a distinct concern and standard from the other two ducts, driven by the combustible nature of grease and its connection to the flames. When people talk about extract cleaning and TR19, this is the duct they mean.
Dry ductwork
Dry ductwork is general ventilation - the supply and extract ducting that moves air through offices, dining rooms and other occupied spaces, carrying no grease. The substance building up in it is dust and debris, so its concern is not fire but air quality and system hygiene: dust in ventilation ductwork degrades the air delivered into occupied spaces, can support microbial growth, and reduces how well the system ventilates. It is a health, comfort and performance matter rather than a fire one.
So dry ductwork is cleaned to a different standard for a different reason - to the TR19 Air standard, the recognised specification for the internal cleanliness of general ventilation systems, which classifies the required cleanliness by how the space is used. The purpose is clean, healthy air and a properly performing system, not fire control. This is a genuinely separate job from grease extract cleaning: different substance (dust not grease), different risk (air quality not fire), different standard (TR19 Air not Grease). A building with both a kitchen and general ventilation needs both, applied correctly.
Laundry ductwork
Laundry ductwork carries the exhaust from commercial tumble dryers, and the substance building up in it is lint - the fine, dry fibre shed from drying. Like grease, lint is combustible, so a laundry duct carries a fire risk, but of its own kind: lint is a highly ignitable fuel accumulating inside a duct that carries heat from the dryers, which is why tumble-dryer lint is a well-known cause of laundry fires. So the laundry duct shares the fire-risk concern with the grease duct, but from a different substance and in a different setting.
So laundry ductwork is cleaned to control the fire risk of lint accumulation - clearing the combustible lint from the exhaust run so it does not build to a dangerous level beside the dryers' heat. It is a fire-safety clean, like the grease duct, but for lint rather than grease, in a laundry rather than a kitchen. Recognising the laundry duct as its own kind - a combustible fire risk from lint, distinct from both greasy kitchen extract and dry ventilation - is what ensures it gets the fire-safety cleaning attention it needs, which it can easily miss if lumped in with either of the others.
The takeaway
Ductwork comes in kinds that need treating differently, because the substance each carries determines its risk and its cleaning need. Kitchen grease extract carries combustible grease - a fire risk, cleaned to the TR19 Grease standard. General dry ventilation carries dust - an air-quality concern, cleaned to the TR19 Air standard. Laundry ducts carry lint - a combustible fire risk, cleaned to control it. Three kinds, three substances, three risks, three cleans.
So knowing which kind of duct you have tells you what its clean must address - fire safety for grease and lint (to different standards and settings), air quality for dry ventilation. A premises with a kitchen, general ventilation and a laundry has all three, each needing its own clean; assuming one covers another, or treating them all the same, misses what each requires. Tell the ducts apart by their substance and risk, and each gets the right clean - which is how all three are genuinely looked after rather than one being neglected because it was mistaken for another.
Questions
No. Different ducts carry different substances, which determine the risk and cleaning need. Kitchen grease extract (combustible grease), general dry ventilation (dust) and laundry ducts (lint) present three different risks and require three different cleans.
Kitchen extract carrying combustible grease from the cookline. Its risk is fire - the grease is a concentrated fuel connected to the flames and a path for fire to spread - so it is cleaned to the TR19 Grease standard, with measurable grease limits and verification, to control that fire risk.
General ventilation - the supply and extract ducting moving air through occupied spaces, carrying dust rather than grease. Its concern is air quality and system hygiene, not fire, so it is cleaned to the TR19 Air standard, which classifies the required cleanliness by how the space is used.
Because it carries lint from tumble dryers - a fine, dry, highly combustible fibre accumulating inside a duct that carries heat from the dryers. That combination of combustible fuel and heat source makes tumble-dryer lint a well-known cause of laundry fires, so the duct is cleaned to control it.
A premises with a kitchen, general ventilation and a laundry has all three kinds of duct, each needing its own clean to its own standard. Assuming one clean covers another, or treating them all the same, misses what each requires - so each is looked after separately.
By the substance each carries and the risk it presents - grease (fire, TR19 Grease), dust (air quality, TR19 Air), or lint (fire, laundry). Knowing which kind of duct you have tells you what its clean must address, so each gets the right treatment.
We clean all three kinds of ductwork correctly - grease extract to TR19 Grease, general ventilation to TR19 Air, and laundry lint ducts for fire safety - each to the standard its risk requires.
