A fire door holds back fire and smoke, protecting escape routes and buying people time to get out. But it only works if it's the right door, fitted properly and kept shut.

What Makes a Fire Door?

  • Rating – an FD30 door resists fire for 30 minutes; an FD60 for 60 minutes. An "S" (for example, FD30S) means it also has smoke seals.
  • Certification – look for a label or plug, usually on the top edge, showing it's been tested and certified.
  • Intumescent strips and smoke seals – see below.
  • Self-closer – shuts the door firmly from any position.
  • Hinges – at least three, fire-rated, with no missing screws.

The door, frame and fittings are tested together, so replacing parts with non-approved ones can stop it working.

Intumescent Strips and Smoke Seals

  • Intumescent strips expand in the heat of a fire to seal the gaps around the door, holding back flames and hot smoke. A plain intumescent strip is a flat strip, usually set into a groove.
  • Smoke seals stop cold smoke getting through before the strip has expanded. You can tell them apart because they have a soft brush (a line of bristles) or a flexible rubber or plastic fin sticking out of the strip, which touches the door when it's closed.
  • Many fire doors use a combined strip – an intumescent strip with a brush or fin smoke seal built in.
  • The strips can be fitted into a groove in the edge of the door or into the door frame, depending on how the door was certified.

Seals Under the Door

  • Fixed seals – a brush or rubber strip fixed along the bottom of the door or on the threshold, closing the gap at the bottom.
  • Drop-down (automatic) seals – fitted into the bottom of the door. They stay up while the door is open, so it doesn't drag on the floor, and drop down to seal the gap when the door closes.

Only fit seals that are approved for your door, so you don't affect its certification.

The Five-Step Fire Door Check

  1. Certification – is there a label or plug?
  2. Gaps – are the gaps around the top and sides even and less than about 4 mm? The gap at the bottom should be as small as practical.
  3. Seals – are the intumescent strips and smoke seals in place and undamaged?
  4. Hinges – are there at least three, firmly fixed?
  5. Closing – open it halfway and let go. Does it close fully on its own and latch?

Gap sizes vary slightly between manufacturers, so check the door's instructions.

Never Wedge a Fire Door Open

A wedged or propped door can't do its job. If a fire door needs to be open during the day, use a device that lets it close automatically when the fire alarm sounds:

  • Electromagnetic hold-opens – a magnet on the wall or floor, wired to the fire alarm. The door is released when the alarm sounds or if the power fails.
  • Battery-operated acoustic door retainers – such as Dorgard or DoorSense. They fit to the door, listen for the fire alarm and let the door close when it sounds. No wiring is needed. Some can also release the door at night, and many test themselves regularly. They need a fire alarm that's loud enough where they're fitted, aren't suitable for noisy areas, and may not be suitable for doors to kitchens, boiler rooms or a single staircase.
  • Free-swing door closers – the door moves freely like a normal door, with no resistance, and closes automatically when the alarm sounds. Helpful for people with limited strength and wheelchair users.

Your fire risk assessment should confirm which doors can be held open and how. Include these devices in your weekly fire alarm test, and make sure staff know never to wedge doors open.

Fire Door Signs

  • "Fire Door Keep Shut" – on normal fire doors, on both sides if used from both sides.
  • "Automatic Fire Door Keep Clear" – where a hold-open device is fitted.
  • "Fire Door Keep Locked" – on cupboards and riser doors.

Blocks of Flats

In England, the Fire Safety (England) Regulations 2022 require communal fire doors in buildings over 11 metres to be checked every three months, and flat entrance doors every year. In Wales, Scotland and Northern Ireland, fire doors must be maintained under the general fire safety law, and your fire risk assessment should set how often they're checked. See GOV.UK fire door guidance.

Worth remembering… your fire risk assessment is what decides what your premises need. This guide is general advice, not a substitute for it.

Not sure what you need? Get in touch with our team – we'll be delighted to help. No pressure. No sales patter.