Bottom edge: Threshold gap per the evidence and any smoke control need
Fire-resisting leafDrag to rotate · click a markerIllustrative example, not a specification
In the fire door
Where it sits
Inspection focus
What inspectors check
Locate the certification label or plug: usually the top edge, sometimes the hanging edge
Check perimeter gaps at head, jambs and threshold against the manufacturer's evidence
Look over both faces and all four edges for impact damage and splits
Sight down the leaf for bow or twist
Extended knowledge
Go deeper
Certification label or plug missing
Planed down beyond the permitted margin
Impact damage, splits or gouges in the face or edges
Holes or unfilled fixings through the leaf
Test yourself
5 questions
All questions are based directly on the content in this section.
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Before you go in
This is an introduction to fire doors, not the whole subject.
Fire Door Anatomy opens one timber fire door, looks hard at ten of its components, and puts it through one furnace test. It is dense, and it is deliberately narrow. A fire door is a far bigger subject than any one tool can hold.
In here
Ten components of a timber fire door or escape door
The furnace test, to BS EN 1634-1
A free CPD certificate of participation, after a short knowledge check
It is engineered to save lives: an assembly of components, working as one.
10 common components00 / 10
Door leafDoor frameIntumescent sealSmoke sealHingesDoor closerLock & latchPanic hardwareGlazingSignage
Ten components of a timber fire door
Door leaf. The leaf is the mass of the fire door. The core chars slowly and holds the barrier against fire, while the other components keep it sealed, closed and in place. The rating belongs to the tested door assembly, not the leaf alone. This model is a timber leaf, the most common type in UK buildings. Fire doors are also made in steel, glass and composite, and hardware proven on timber does not transfer to them.
Door frame. The frame carries the leaf and completes the barrier. The stops form the rebate the leaf closes into. The fixings tie the fire door to the structure. The gap between frame and wall must be fire-stopped.
Intumescent seal. Intumescent material set into the leaf edge or the frame. Under heat it expands to many times its size, closes the perimeter gap against hot gases and helps hold the leaf in the frame. Activation is a property of the material rather than a single number.
Smoke seal. Fire takes minutes. Smoke takes seconds. Brush or fin seals close the perimeter gap at room temperature, holding back cold smoke long before flames arrive. The seal modelled here is a combined fire and smoke seal: an intumescent core with a brush standing proud of the same housing, a common arrangement where smoke control is required. Smoke seals are also fitted on their own, commonly as a flexible fin in the frame rebate.
Hinges. Three hinges typically carry a full-size leaf, through years of daily traffic and then through a fire. The hinges are part of what the fire door's evidence covers: single axis hinges within the scope of BS EN 1935 are conformity marked, and other types are permitted where the evidence covers them. Every screw is structural.
Door closer. An open fire door is just a door. The closer is required to reliably return the leaf into its closed position from any angle, every time, and into its latch where one is fitted, without anyone deciding to do it. It is what makes the rating true in use rather than on paper. Switch to the cutaway to see what is doing the work: a spring wound up by opening the door, and hydraulic fluid pushed through valves on the way back.
Lock & latch. A lock secures a door; a latch holds it closed. Some fire doors are tested and specified latched, and there the latch is what the closer closes into: a positive hold that keeps the leaf seated while pressure builds on the fire side. Others are tested and specified unlatched, relying on the closer and the seals, and the installed configuration must match the door's evidence either way. Cutting a mortice takes timber out of the leaf and puts metal in its place, which changes how that part of the door behaves in fire. The lock shown here has no intumescent on it. Many fire doors need it around the case, and whether yours does is set by the evidence rather than by eye.
Panic hardware. On a locked escape door the way out must not depend on a key, a code or prior knowledge. Panic hardware releases every locking point in one action: a horizontal bar, pushed in the direction of escape, working under crowd pressure. Devices range from a bar driving a single latch to vertical rod devices bolting at head and threshold, and emergency exit devices to BS EN 179 use a lever or push pad in place of the bar. A door can be both fire-resisting and part of an escape route, and then the hardware has two jobs at once.
Glazing. A vision panel lets people see what they are opening a door into. It is also a hole cut in the barrier. Fire-rated glazing uses specialist glass, intumescent-lined beads and strict limits on size and position, all fixed by the fire door's evidence.
Signage. The blue disc carries the instruction: fire door, keep shut. It is the cheapest component of the assembly and the only one addressed to people rather than to fire. Fire safety guidance calls for it, and fire safety legislation requires it to be maintained.