Fire, insurance & risk
A damper is only a safeguard if it can close. In a grease run the same deposit that lines the duct is what jams the blade - so cleaning and drop-testing are one job.
The short answer
Where a fire damper sits in ductwork, it must close freely to hold a fire compartment. Grease and dust on the blades, guides and springs can choke it so it never drops. That is where dampers and cleaning meet: a grease system with dampers turns each one into a cleaning-and-drop-test item. The standards' preferred answer is fire-rated duct and a clean run, not a damper.
How a damper is meant to work
A fire damper sits where a duct crosses a fire-rated wall, floor or riser. A fusible link - typically rated to release at around seventy-two degrees - melts in a fire and lets a spring-loaded blade or curtain drop, sealing the duct so flame and smoke cannot pass through the breach the duct created in the barrier. Motorised versions close on a signal instead. Either way, the whole safeguard depends on one thing: the blade being able to fall fully and freely.
That is a demonstrable requirement, not an assumption. Under the Regulatory Reform (Fire Safety) Order 2005 the Responsible Person must keep dampers in efficient working order, which in practice means a drop test - releasing the link or actuator, confirming full closure, then cleaning, lubricating, resetting and logging the unit with photographs.
Where cleaning comes in
In a kitchen grease run, the deposit that lines the duct is the same deposit that coats the damper. Grease and dust on the guide channels and springs can wedge the blade open, so when the link finally melts, the damper cannot complete its drop - and the compartmentation it exists to provide simply fails. A choked damper is worse than none, because the fire strategy assumes it will close.
This is why testing frequency steps up in kitchens. General guidance sets at least annual drop tests, but dust-laden or high-risk environments such as commercial kitchen extract are commonly tested every six months, with a commissioning test within a year of installation and again after any alteration. Access to test and clean needs quick-release insulated sealed panels to the BESA DW144 specification - the same access the cleaner uses.
The standards' actual position
Here is the point most operators miss. BS 9999:2017 states that fire dampers should not be fitted in kitchen grease-extract ductwork at all - the run should instead be fire-rated duct or a dedicated protected shaft where it leaves the kitchen compartment. Where legacy dampers are found in older installations, the guidance is to test them at least annually, or to remove them entirely, with removal recommended and triggering a review of the fire risk assessment.
So the honest answer to where dampers and cleaning meet is this: in a grease system a surviving damper is a maintenance liability, kept safe only by being cleaned and drop-tested at every visit - and the cleaner and the damper engineer are doing one connected job, not two separate ones. A proper TR19 clean accounts for the dampers in the run; it does not clean around them.
Questions
Because a damper only holds a fire compartment if its blade can drop freely, and the grease that lines a kitchen extract duct is exactly what coats and jams the blade. A grease run with dampers turns each one into a cleaning-and-drop-test item.
General guidance sets at least annual drop tests, but dust-laden or high-risk environments such as commercial kitchen extract are commonly tested every six months, plus a commissioning test within a year of installation and after any alteration.
A fusible-link damper typically releases at around seventy-two degrees, letting a spring-loaded blade drop to seal the duct. Motorised dampers close on a signal instead.
BS 9999:2017 says fire dampers should not be fitted in kitchen grease-extract ductwork - the run should be fire-rated duct or a protected shaft. Legacy dampers should be tested at least annually or removed, with removal recommended and an FRA review.
The engineer accesses the damper, releases the fusible link or actuator, confirms the blade closes fully, then cleans, lubricates, resets and logs the unit with photographs - proving it will actually close in a fire.
Phoenix Duct Clean · by the numbers
We clean the whole extract run to TR19 Grease and account for every damper and access panel along it. Book a compliant clean.