How to Identify a Fire Door: 7 Signs to Look For
Fire doors can look almost identical to ordinary doors — but they are engineered very differently. Knowing how to tell them apart is the first step to managing fire door safety in your building. Here are the seven signs that identify a genuine fire door.
Quick answer: A fire door usually has a certification label or plug on its top edge, intumescent seals, three hinges, a self-closer, and a thicker, heavier leaf. Several of these signs together point to a genuine fire door.
The 7 Signs of a Fire Door
A certification label or plug
Look on the top edge (or hinge edge) for a label or colour-coded plug stating the manufacturer and fire rating, such as FD30 or FD60. This is the clearest proof of a certified fire door.
Intumescent and smoke seals
A strip set into the edge of the door or frame that expands in heat to seal the gap. A brush or fin seal alongside it indicates smoke protection (the “S” rating).
Three or more hinges
Fire doors are heavy and are usually hung on three hinges (sometimes more), all CE/UKCA marked and fully fitted with the correct screws.
A self-closing device
A controlled closer that returns the door fully to the closed and latched position. A fire door only protects when closed.
A thicker, heavier leaf
FD30 doors are typically ~44mm thick and FD60 ~54mm, against ~35mm for a standard door. The solid core makes them noticeably heavier.
Consistent gaps around the door
Even gaps of around 3mm at the sides and top, with a controlled threshold gap. Large or uneven gaps undermine the seal.
Correct, fire-rated ironmongery
Latches, locks and any glazing should be fire-rated and intact, with no unauthorised holes or modifications cut into the leaf.
What Do FD30 and FD60 Mean?
FD30
30 minutes of fire resistance. The most common rating for flat entrance doors and doors onto protected stairways in lower-rise buildings.
FD60
60 minutes of fire resistance. Used where greater protection is needed, such as taller buildings and higher-risk compartment lines.
FD30S / FD60S
The “S” means the door also restricts the spread of cold smoke and has smoke seals fitted.
FD90 / FD120
90 and 120 minutes of fire resistance, used in specialist and high-risk situations.
No Label Doesn't Always Mean No Fire Door
Labels are often painted over, trimmed off or lost over the years. A door without a visible label may still be a genuine fire door — and a thick door with seals is not automatically certified. Where the rating cannot be confirmed, have the doorset assessed by a competent fire door inspector.
Identifying a Fire Door Is Only the Start
Once you have identified your fire doors, they need to be checked and maintained. Under the Fire Door Regulations 2022, communal fire doors in taller residential buildings must be checked quarterly. Our guide on how to inspect a fire door walks through exactly what to check.
Not Sure Your Fire Doors Are Up to Standard?
Fyrup carries out professional fire door inspections and remedial works across London.
Frequently Asked Questions
How can I tell if a door is a fire door?
Look for a certification label or colour-coded plug on the top or hinge edge of the door, intumescent seals fitted into the door or frame, three hinges, a self-closing device, and a thicker, heavier leaf (usually 44mm or more). A genuine fire door will normally show several of these signs together. If in doubt, have it assessed by a competent person.
Where is the label on a fire door?
The certification label or plug is most commonly found on the top edge of the door (visible when the door is opened and viewed from above) or occasionally on the hinge edge. It identifies the manufacturer and the fire rating, such as FD30 or FD60. If a door has been painted over or trimmed, the label may be obscured or missing even though the door is a genuine fire door.
What does FD30 and FD60 mean?
FD stands for Fire Door, and the number is the minutes of fire resistance the doorset is tested to provide. FD30 offers 30 minutes and FD60 offers 60 minutes of fire resistance. You may also see FD30S or FD60S, where the “S” means the door also restricts the spread of cold smoke and has smoke seals fitted.
How thick is a fire door?
Fire doors are noticeably thicker and heavier than standard internal doors. An FD30 fire door is typically around 44mm thick, and an FD60 fire door is around 54mm thick, compared with about 35mm for a standard internal door. The extra thickness and a solid core are part of how the door resists fire.
Can a fire door be identified if there is no label?
A missing label does not always mean the door is not a fire door — labels can be painted over, trimmed off or lost over time. Other signs (intumescent seals, three hinges, a self-closer, thickness and a solid core) can indicate a fire door, but without certification it cannot be confirmed. A competent fire door inspector can assess the doorset and advise whether it provides the required protection.
Do fire doors have to have a self-closer?
Most fire doors must be fitted with a controlled self-closing device so they return fully to the closed position and latch after use, because a fire door only works when closed. Some flat entrance doors and certain doors held open on approved hold-open devices linked to the fire alarm are exceptions, but a self-closer is one of the strongest indicators that a door is intended to be a fire door.
Get Your Fire Doors Professionally Inspected
Fyrup provides certified fire door inspections, surveys and remedial works across London — giving you a clear record of which doors comply and which need attention.