Fire suppression & interlocks
A fire damper is a heat-triggered shutter that closes a duct where it crosses a fire compartment, stopping fire spreading through the ductwork. The important twist for kitchens is that dampers are usually not fitted in the grease extract itself - and knowing where they do belong matters.
The short answer
A fire damper is a heat-triggered shutter that closes a duct where it crosses a fire compartment, stopping fire spreading through the ductwork. The important twist for kitchens is that dampers are usually not fitted in the grease extract itself - and knowing where they do belong matters.
The detail
A fire damper sits in a duct at a compartment boundary - a wall or floor rated to hold fire back. Normally it is open and air passes through. On a fire, a fusible link rated around 72C melts, or a motorised actuator interfaced to the fire alarm drives the blades shut, sealing the duct so fire and smoke cannot travel along it into the next compartment.
Here is the nuance for kitchens: fire dampers are generally not fitted in grease extract ductwork. Grease clogs and jams them, so a damper in the extract is as likely to fail shut as to work - a liability, not a safeguard. TR19 and DW/172 instead favour fire-rated ductwork or a fire-rated enclosure where grease extract crosses compartment lines.
So where do you find dampers near a kitchen? In older or non-compliant extract installations that predate current guidance, and in the building's general ventilation - the supply air, the toilet extract, the comfort systems serving the kitchen area - which carry no grease and are the proper home for dampers.
That distinction decides who tests what. The grease extract is managed by cleaning and by the integrity of its fire-rated enclosure; any dampers in the surrounding general ventilation are managed by inspection and drop testing. Confusing the two leaves a real gap in the fire strategy.
What it means for you
Where dampers are present, BS 9999 sets the regime: test by a competent person on completion of the installation and at least annually, and more often - typically six-monthly - in dust or grease-laden environments such as a commercial kitchen area. DW/145 from BESA is the authoritative install and maintenance framework.
A test is a drop test: access the damper, release the link or actuator, confirm the blades fully close and seal, then reset and log the location, condition and result. Access panels either side let the engineer reach and reset it. Any damper that will not close or seal is a fail and needs remedial work.
For the grease extract itself, the equivalent discipline is cleaning to TR19 and maintaining the fire-rated ductwork - not fitting a damper that grease would defeat. Getting this right means testing the dampers you have while keeping the extract clean and its enclosure intact.
The service behind the guide
Sibling guides
Fire damper drop testing and how often · Why nozzles need a clean canopy · Who is responsible in a leased kitchen
Questions
Usually not, and deliberately so. Grease jams dampers, so fitting one in grease extract is a liability. Current guidance uses fire-rated ductwork or enclosures at compartment lines instead, with dampers reserved for the non-grease general ventilation.
Heat. A fusible link rated around 72C melts and lets the blades close, or a motorised actuator linked to the fire alarm drives them shut. Either way the duct is sealed so fire cannot travel through it to the next compartment.
BS 9999 requires a competent-person test on installation and at least annually, and more frequently - typically six-monthly - in dust or grease-laden areas like a commercial kitchen. DW/145 is the framework for how it is done.
A damper is a shutter that closes on heat; fire-rated ductwork resists fire along its whole length. Grease extract uses the ductwork or enclosure approach because it does not clog the way a damper does.
The building's responsible person, usually via a competent fire damper contractor for the general ventilation. The grease extract is a separate discipline, kept safe by TR19 cleaning and intact fire-rated ductwork.
Phoenix Duct Clean · by the numbers
Phoenix Duct Clean maintains your kitchen extract to TR19 Grease and fire-rated integrity - the right protection for grease ductwork, where a fire damper would only clog.