Fire door checks: how to tell if a door is a fire door

A fire door is a piece of engineering that only works when it's shut and in good order. Its job is to hold back fire and smoke long enough for people to get out — often 30 minutes (FD30) or 60 (FD60). Wedge it open, or let it fall into disrepair, and it protects no one.

How to tell if a door is a fire door

Before you can check a fire door, you need to know it is one — they're not always obvious. Look for these signs:

• A certification label or plug. Most certified fire doors carry a colour label or a small plug set into the top or hinge edge of the door — the clearest single giveaway.
• Intumescent seals. A strip set into the door edge or frame that expands in heat to seal the gap. Ordinary internal doors don't have them.
• A self-closer. Fire doors are designed to close themselves — usually an overhead closer or concealed device.
• Solid, heavy construction. Fire doors are noticeably heavier and thicker (typically 44–54 mm) than a standard internal door.
• Three hinges. Fire doors usually have three (or more) fire-rated hinges to carry the extra weight.
• A "Fire door — keep shut" sign. The blue mandatory disc is a strong hint (though a sign alone doesn't make a door a fire door).

If you can't confirm a door is a genuine, certified fire door, treat that as a finding for your fire risk assessment and get it checked by a competent person.

Why the shut door matters

Buildings are divided into fire-resisting compartments so a fire in one area can't quickly take the whole building. Fire doors are the moving parts of that compartmentation. That's why the most common — and most dangerous — failing isn't a broken door at all: it's a good door propped open. An open fire door is just a door. If it needs to stay open for traffic, it must be held by a device that releases and closes it automatically when the alarm sounds.

The five-point check: spotting a failing fire door

You don't need to be an inspector to run a sensible visual check. Walk up to the door and look at five things:

1. Gaps. The gap around the top and sides should be consistent and small — commonly around 3 mm. Too wide and smoke gets through; wildly uneven gaps suggest the door has dropped or been rehung badly.
2. Seals. Look for the intumescent strip (which expands in heat) and any smoke seal (brush or fin) in the frame or door edge. They should be present, continuous, and undamaged — not painted over, cut, or missing.
3. Self-closer. Open the door and let go. It should close fully, on its own, into the latch — not stop an inch short. A door that doesn't close is a door that won't be shut when it counts.
4. Hinges & ironmongery. Hinges firm, screws present and tight, no missing fixings. Fire doors are heavy and rely on their hardware being intact.
5. Condition & certification. No holes, large splits, or unauthorised alterations (a letterbox cut into a flat entrance door, say). Many certified doorsets carry a label or plug on the top or hinge edge — a useful sign the door is what it claims to be.

How often, and by whom

Frequency is ultimately driven by your fire risk assessment and the building's use. High-traffic settings — schools, care homes, hospitals — justify more frequent checks than a quiet low-rise. A common baseline for non-domestic buildings and lower-rise communal areas is a formal inspection roughly every six months by a competent person, with quick visual checks far more often. Anyone can be trained to spot the obvious faults; the point is that someone is actually looking.

The takeaway

Most fire door failures are boringly simple: propped open, closer not closing, seals missing, gaps too big. None of them need a specialist to notice — they need a trained eye and the habit of looking. That habit is the whole game.

This guide is for learning and applies to England & Wales. Always work from the current regulations and your own fire risk assessment; Scotland and Northern Ireland have equivalent regimes.