How to Identify a Fire Door: Labels, Plugs and Physical Checks

How can you tell if a door is a fire door?

Fire doors are designed to hold back fire, and in many cases cold smoke, for a defined period, so a building's escape routes stay usable. Because a fire door only works as a complete, tested assembly, you cannot reliably identify one by appearance alone: many fire doors look identical to ordinary doors once decorated. Identification therefore works in two layers. First, look for certification evidence — a label or plug applied by the manufacturer under a third-party scheme. Second, look for physical features such as intumescent seals, leaf thickness, hinges and a self-closing device, which support (but never replace) that evidence.

Getting this right matters legally as well as practically. Under article 17 of the Regulatory Reform (Fire Safety) Order 2005, the responsible person must ensure fire doors and other fire safety measures are "maintained in an efficient state, in efficient working order and in good repair" — a duty you cannot discharge if you do not know which doors are fire doors in the first place. Our fire door regulations overview explains the wider legal framework.

Where is the fire door certification label or plug?

Third-party certification schemes require manufacturers to mark every fire door so it can be traced back to its test evidence. According to the BWF Fire Door Alliance, the label is fixed to the top edge of the door leaf (or within the frame for complete doorsets) and typically shows the manufacturer's name and contact details, the certification number, a unique serial number for traceability and the door's fire rating. A standard unglazed door usually carries one label; doors glazed or modified by a licensed processor may carry two. Labels should never be removed or painted over.

Reading the label

• Scheme mark — for example Certifire (Warringtonfire) or BM TRADA Q-Mark, identifying which third-party scheme certified the door.
• Certificate number — such as a Certifire "CF" number, which corresponds to that particular door design and can be checked against the scheme's online register.
• Fire rating — for example FD30 or FD60; see our guide to FD30 vs FD60 ratings for what these mean.
• Manufacturer details and serial number — allowing the door to be traced through the supply chain if further information is needed.

Coloured plugs in the door edge

Some schemes use plugs instead of, or as well as, labels. BM TRADA explains that Q-Mark certified timber fire doors carry colour-coded plastic plugs, typically in the top edge or the hanging edge of the leaf. The plug confirms the door is third-party certificated, and the colour indicates the status of that certification — for example, that certification is conditional on intumescent seals being fitted or on the door being paired with a certified frame. You may also find coloured plugs from older, now-discontinued marking systems in existing buildings; these still indicate the door was supplied as a fire door, but the certification conditions should be verified rather than assumed.

Whichever mark you find, record the certificate number and check it on the relevant scheme register (Certifire certificates via Warringtonfire, Q-Mark via BM TRADA). A label is strong evidence of how the door was manufactured — it does not confirm the door was installed correctly or remains in good condition, which is why installation and inspection matter separately.

What physical features identify a fire door?

Where there is no obvious label, physical features can build a picture — but each clue has limits. The table below summarises what each feature does and does not tell you.

Intumescent strips and smoke seals

Look along the edges of the door leaf or the frame reveal for a thin strip, usually around 10-20 mm wide, set into a groove. Intumescent seals expand many times their size under heat to seal the gap between leaf and frame; smoke seals (brushes or fins, often combined with the intumescent strip) block cold smoke and are what earns a door its "s" suffix, as in FD30s. Their presence is one of the strongest visual clues — though older notional fire doors may lack them entirely, and seals that have been painted over are impaired. See our detailed guide to intumescent strips and smoke seals.

Leaf thickness and weight — a caveat

Typical timber fire doors are around 44 mm thick for FD30 and 54 mm for FD60, compared with roughly 35-40 mm for many standard internal doors. Measuring the leaf is quick and worth doing — but treat it strictly as supporting evidence. A 44 mm leaf may be an ordinary solid-core door with no fire performance at all, and thickness reveals nothing about the core material, the frame, the seals or the hardware, all of which the tested assembly depends on. The same applies to weight: fire doors are usually noticeably heavy, but heaviness alone identifies nothing.

Hinges, closers and glazing

Fire doors are normally hung on three hinges or more to carry the heavier leaf, and certification requires ironmongery — locks, latches, hinges and closers — to be conformity marked and compatible with the door's certification. Most fire doors in escape routes must have a working self-closing device (closers to EN 1154, or EN 1155 for electromagnetic hold-open units); our guide to fire door self-closers covers the requirements. Any glazing should be fire-rated glass, usually etched with a marking in the corner of the pane, and unauthorised apertures cut into a certified door void its certification.

Step-by-step fire door identification checklist

Work through the following steps for each door you need to identify. This mirrors the logic of the BWF Fire Door Alliance's five-step check, which covers certification, gaps, seals, closing and hardware.

1. Open the door and inspect the top edge for a certification label. Note the scheme, certificate number, serial number and fire rating.
2. Check the hanging stile and top edge for coloured plugs set into the timber — a sign of Q-Mark or older scheme certification.
3. Verify the certificate number against the scheme's online register (Certifire via Warringtonfire, Q-Mark via BM TRADA) to confirm the door design and rating.
4. Look for intumescent and smoke seals in the door edges or frame reveal, and check they are continuous, undamaged and not painted over.
5. Measure the leaf thickness — around 44 mm suggests FD30 construction and 54 mm suggests FD60, remembering this is supporting evidence only.
6. Count the hinges — expect three or more, firmly fixed with no missing screws, ideally with visible CE or UKCA conformity markings.
7. Test the self-closer by opening the door to about halfway and releasing it: it should close fully into the frame and engage the latch unaided.
8. Check the gaps between leaf and frame — consistent gaps of roughly 2-4 mm at the head and sides are what installation standards expect; see our gap tolerances guide.
9. Inspect glazing and hardware for fire-rated glass markings and unauthorised alterations such as cut-in vents, letterplates or pet flaps.
10. Record your findings for every door. Where you find no certification evidence, flag the door for competent assessment rather than assuming it performs.

You can use our free fire door inspection checklist to record these checks systematically, and the fire door compliance checker to work out which duties apply to your building.

What if there is no label? Notional and nominal fire doors

Many doors that were installed as fire doors — particularly in older buildings — carry no label or plug, either because they pre-date modern certification schemes or because the evidence has been lost under decades of paint. The industry uses two terms for these doors, as explained by fire door inspection specialists.

• A notional fire door is one that satisfied the standard applicable to fire-resisting doors at the time the building was constructed. It was a legitimate fire door in its day, but it may lack features now expected, such as intumescent strips and smoke seals.
• A nominal fire door is one that, in the opinion of a competent fire door inspector, can provide fire resistance for a specified period — but carries no certification evidence, so its performance is a professional judgement rather than a tested fact.

Neither type carries the assurance of a certified door, so both represent a higher level of uncertainty that should be recorded in the building's fire risk assessment. The assessment route is a survey by a competent person, who considers the door's construction, thickness, condition, frame, hardware and location, and then recommends one of three outcomes: accept the door as adequate for its risk, upgrade it (for example by adding intumescent seals, smoke seals, a self-closer and a protected letterplate, where the leaf is substantial enough to justify it), or replace it with a certified doorset. Upgrading only makes sense where the door itself is suitable — lightweight doors with thin panels cannot be meaningfully upgraded — and where the upgrade products have test evidence applicable to that door type.

When should you commission a professional inspection?

Routine checks and professional identification are different jobs. In England, government guidance under the Fire Safety (England) Regulations 2022 requires responsible persons in multi-occupied residential buildings over 11 m to check communal fire doors at least every three months and to use best endeavours to check flat entrance doors at least every twelve months. The same guidance is explicit that these regulation 10 checks are "simple and basic" — and that identifying whether a door is of the right type in the first place "is a matter for your fire risk assessment", not for the routine checks. Our guide to regulation 10 fire door checks covers the routine regime in detail.

Commission a competent fire door inspection when any of the following applies:

• You have doors on escape routes or compartment lines with no certification label or plug, and their status has never been professionally assessed.
• Your fire risk assessment identifies fire doors but does not evidence their type, rating or condition.
• The building has changed use or been refurbished, and doors may have been replaced, modified or re-glazed without records.
• Routine checks keep finding defects — damaged seals, excessive gaps, failed closers — suggesting the doorset may be unsuitable rather than merely worn.
• You manage an HMO or block of flats and need documented evidence of door status for the responsible person's records under the Fire Safety Order.

A professional inspection identifies each door's likely rating, records certification evidence where it exists, classifies unlabelled doors as notional or nominal, and recommends acceptance, upgrade or replacement. See our guide to fire door inspection for what a competent survey involves and how often one is appropriate.