INTERNAL FIRE DOORS
Internal fire doors are engineered door assemblies fitted inside a building to hold back fire and smoke for a set period, giving people time to escape and helping the emergency services do their job. They work by sealing off one part of a building from another, so a fire that starts in one room cannot spread freely through corridors, stairwells and escape routes.
A fire door is never just a heavier version of an ordinary door. It is a tested system where the leaf, frame, glazing, seals and hardware all have to work together to achieve the rating it claims. At Aluminium Fire Systems we manufacture and supply fire rated aluminium doors for internal use, classified to EI30, EI60 and EI90 under the European standard, and every project is delivered with a full compliance pack so you can prove what you have installed.
What Are Internal Fire Doors
An internal fire door is a fire resisting door used within a building rather than at its external envelope. Its purpose is to slow the passage of fire and smoke between compartments, which protects escape routes and limits damage to property. The principle behind it is called compartmentation. By dividing a building into fire resisting sections, you contain a fire close to where it started instead of letting it run through the whole structure.
These doors are required wherever a building’s fire strategy calls for a barrier between areas. That includes the doors onto protected stairwells, doors that subdivide long corridors, doors into higher risk rooms such as plant rooms and commercial kitchens, and doors onto escape routes in commercial and residential buildings. The door has to keep performing under intense heat for the full rated time, which is why each one is tested as a complete assembly rather than as separate parts.
The interior fire doors most people picture are timber. Much of the wider market is built around timber and composite leaves rated to FD30 or FD60, finished in oak, white primed or flush styles. Aluminium fire doors are a different proposition. They use a thermally broken aluminium frame with fire resistant glass and intumescent components housed inside the profile, which allows much larger glazed areas and slim sightlines while still achieving a high rating. That makes them well suited to modern commercial and residential interiors where natural light and clean lines matter as much as safety.
How Internal Fire Doors Work
A fire door buys time. When a fire breaks out, the door and its surrounding frame form a sealed barrier that resists flames, hot gases and smoke for a defined number of minutes. During that window, occupants can move away from the fire along a protected route, and firefighters can enter safely. The longer the rating, the longer that protection lasts.
Several components make this possible. Intumescent strips fitted around the leaf or frame expand when they get hot, sealing the gap between the door and the frame so flames and smoke cannot pass through. Smoke seals deal with cold smoke at room temperature. The frame itself has to match the rating of the leaf, because a fire resistant leaf in a weak frame protects nobody. In an aluminium system, specially designed cooling inserts inside the profile chambers absorb heat and protect the structure of the metal, which is what lets the door keep its shape and its seal as the temperature climbs.
Integrity and Insulation Explained
Fire performance is described using two separate ideas, and understanding the difference is the single most useful thing when specifying a door.
Integrity, shown by the letter E, is the door’s ability to stop flames and hot gases passing from the fire side to the safe side. A door with integrity alone holds the fire back, but it can still get extremely hot on the side away from the fire.
Insulation, shown by the letter I, is the door’s ability to limit how much heat passes through to the safe side. A door rated for both integrity and insulation keeps the unexposed face cool enough that people can stand near it and pass by it without being burned, and so that materials on the safe side do not ignite from radiated heat.
This is why an EI rated door offers a higher level of protection than one rated for integrity only. Our fire rated aluminium doors are EI rated, so they manage both the flames and the dangerous transfer of heat. You can read a fuller explanation of how this applies to glazing in our guide on the types of fire safety glass.
EI Ratings Versus FD Ratings
Two rating systems appear across the fire door market, and they are not interchangeable.
FD ratings, such as FD30 and FD60, come from the British Standard test BS 476 Part 22. The number is the number of minutes of fire resistance, so FD30 means thirty minutes and FD60 means sixty. The FD test measures integrity, the ability to hold back flames and hot gases. This is the system most timber fire doors are tested and sold against.
EI ratings, such as EI30 and EI60, come from the European standard EN 13501-2. Here the door is classified for both integrity (E) and insulation (I) for the stated number of minutes. So an EI30 door provides thirty minutes of integrity and insulation, while EI60 provides sixty minutes of both.
The practical takeaway is that an FD rating and an EI rating are not the same thing, even when the minute figure matches. BS 476 Part 22 remains a valid and widely recognised UK benchmark and is still in common use, while the industry continues to move towards the EN classification. AFS products are classified under the EI system. Where you see FD figures mentioned here, they are included to help you compare, not because the two are equivalent. If you want the detail on a specific rating, our knowledge base covers the EI 30 classification and the EI 60 classification in full.
Aluminium Internal Fire Doors
Aluminium is an excellent material for internal fire doors. It is strong, durable and naturally resistant to corrosion, yet light enough to be formed into slim frames. Those slim profiles let you have far larger glazed panels than a timber door allows, without giving up the fire rating. The result is a door that looks contemporary, lets light flow between spaces and still performs as a serious fire barrier.
We manufacture our internal fire doors using the MB-78EI system, an aluminium fire partition system designed for exactly this purpose. It produces internal or external fire partitions with single and double leaf doors, and it integrates directly with fire rated partition walls so a door and the screen around it form one continuous tested barrier. The profiles are thermally insulated and carry fire resistant glass and intumescent components within the frame, which is how the system holds its EI rating while keeping a slim, modern appearance.
EI30 to EI120 Fire Resistance
We supply internal fire doors across four classifications, each providing both integrity and insulation for the stated time:
- EI30 provides 30 minutes of fire rated integrity and thermal insulation. It is the common requirement for protected routes in many buildings.
- EI60 provides 60 minutes of integrity and insulation, used where the fire strategy calls for a longer hold or where occupancy and risk are higher.
- EI90 provides 90 minutes, suited to protected routes in complex or taller buildings and to compartment boundaries around higher risk areas.
The right rating for any opening is set by the building’s fire strategy, not by preference. The strategy looks at the size and use of the building, the location of the door and how long people need to get out. We work to the rating your strategy specifies and supply the classification evidence to match.
Internal Fire Doors With Glass
One of the strongest reasons to choose an aluminium system is glazing. Because the frame is slim and strong, our internal fire doors with glass can carry large fire rated panes while keeping their rating. This lets you create internal glazed fire doors that bring daylight deeper into a building and keep sightlines open across offices, receptions and circulation areas, all without breaking the fire compartment.
The glass itself has to be the right kind. EI rated openings need insulating fire glass, typically a multi laminate or intumescent construction matched to the aluminium system, with a specific thickness and edge cover set out in the classification report. You cannot simply drop ordinary glazing, or even integrity only glass, into an EI door and expect it to perform. Our fire rated glass is specified to match the tested system, and where a project needs larger expanses of glazing alongside the door we can extend the same approach into fire rated glass partitions.
Single and Double Leaf Configurations
Internal fire doors can be supplied as single or double leaf, with or without overpanels and side lights, to suit the opening and the traffic through it. A single leaf suits a standard doorway onto a corridor or stairwell. A double leaf suits wider openings and busier routes. Overpanels and side lights extend the glazed area above and beside the door.
The important rule is that whatever configuration you choose has to be covered by the test evidence for the system. A combination of door, screen and overpanel is only valid at the rating claimed if that exact assembly has been tested or formally assessed. We confirm the configuration against the classification report for every order so there are no surprises at building control.
Where Internal Fire Doors Are Used
Internal fire doors appear across almost every building type once it reaches a certain size or occupancy. In commercial buildings they protect stairwells, separate offices and meeting rooms, and form the compartment boundaries that keep escape routes clear of smoke. In multi-occupancy residential buildings they protect communal corridors and stairs and form part of the protection between flats and common parts. In healthcare, education and care settings they protect routes used by people who may be slower to evacuate, and they separate higher risk rooms such as plant rooms and kitchens from the spaces people move through.
The common thread is the protected escape route. Wherever people need a safe path out of a building, fire doors are what keep that path usable while a fire is held back elsewhere. Our doors are used across commercial and residential projects UK wide, supplied to architects, contractors, developers, fabricators and installers.
Internal Fire Door Regulations in the UK
Fire doors in the UK sit within a framework of building regulations and fire safety law. In England, where fire resisting construction is required is set out in the building regulations, specifically Approved Document B, which deals with fire safety. Products have to be tested to British Standards or the superseding European Standards to prove they perform. This is why classification evidence matters so much. A door is only compliant if you can show it was tested to the right standard and installed as tested.
For occupied multi-occupied residential buildings, the Fire Safety (England) Regulations 2022 introduced specific duties on responsible persons, including checks on fire doors in the common parts and on flat entrance doors in buildings above a set height. These duties are about keeping installed doors in working order over the life of the building. They sit alongside the wider duty to specify and install compliant doors in the first place.
Compartmentation and the Golden Thread
Compartmentation is the principle that underpins every fire door. The building is divided into fire resisting compartments so a fire is contained close to its source. A fire door is the moveable part of that barrier, the point where people pass through a compartment wall, so it has to be as reliable as the wall around it.
Modern fire safety also expects you to be able to prove all of this on paper, which is where the golden thread comes in. The golden thread is the continuous, reliable record of a building’s fire safety information, from design through to occupation. For it to hold, every fire rated element needs documentation showing it was correctly specified, manufactured to a tested system and properly certified. Every project we deliver comes with a customised compliance pack built for that job, containing the technical specification, position drawings, a signed compliance agreement, test certificates and classification evidence, fabrication photographs and material invoices for full traceability. That pack is designed to slot straight into the golden thread, giving principal designers, contractors and accountable persons what they need to evidence compliance. We explain how this works in more detail in our article on the golden thread of information.
Inspection and Maintenance
A fire door only protects people if it stays in good condition and closes properly. Damaged seals, gaps that are too large, missing or wrong hinges, a self closing device that no longer works, or a door that has been propped open all stop it doing its job. Over the life of a building, fire doors need checking and maintaining so that every component still matches the condition it was certified in.
Where the regulations require formal checks, those checks look at the whole assembly, the leaf, frame, seals, glazing and hardware, not just the door itself. Keeping a record of inspections and certifications for every fire rated opening is part of maintaining the golden thread for the building. The detail of who must inspect what, and how often, depends on the building type and height, so it is worth confirming your specific duties against current guidance. You can read our overview of the current law on fire doors for more on this.
Specifying Internal Fire Doors
Specifying a fire door well is about treating it as a system and matching every part to the tested configuration. Get that right and the door performs and passes building control. Get it wrong, by substituting glass or changing hardware or oversizing a pane, and the rating can be void even if the door looks identical.
What Makes Up a Complete Doorset
A complete internal fire doorset is more than a leaf. It includes the door leaf itself, the frame, the fire rated glazing where the design includes glass, the intumescent and smoke seals, and the hardware, which means the hinges, locks, closers and any panic hardware. Each item has to be compatible with the tested system. Listed hinges, closers and seals are specified because they were part of the assembly that earned the rating. Swapping in an untested component breaks the chain.
This is why we supply the door as a coordinated system rather than a collection of parts, and why an installation guide and the correct fixings come with it. The door has to be installed as it was tested, with the right gaps and the right fixings, for the classification to hold on site.
Getting the Classification Evidence Right
The classification report is the document that proves what a door can do. It sets out the exact combination of profiles, glazing, beads, seals, intumescent components, fixings and hardware that achieves the rating, along with the tested sizes and limits. Staying within that evidence is what keeps the door compliant.
A few things commonly catch people out. Mixing an EI door with an integrity only screen in the same elevation is only valid if the combined assembly is covered by evidence. Oversizing panes or changing the ironmongery is not allowed without a formal assessment extending the field of application. Unframed or butt jointed glass is generally not permitted for an EI rating unless it has been specifically tested. We check each order against the classification report and supply the evidence in the compliance pack, so the documentation matches exactly what was made and delivered.
FAQs
Internal Fire Doors FAQs
What are internal fire doors
Internal fire doors are fire resisting door assemblies fitted inside a building to hold back fire and smoke between compartments. They protect escape routes and limit fire spread, giving people time to evacuate and the emergency services time to respond. A fire door is a tested system, so the leaf, frame, glazing, seals and hardware all have to work together to achieve the rating it carries.
Should you prop a fire door open?
A fire door should never be propped open. It can only do its job if it is closed when a fire starts, because a door wedged open leaves the compartment unsealed and lets smoke and flame travel straight through. If a door genuinely needs to stay open for day to day use, the compliant way to achieve that is an automatic hold open device linked to the fire alarm, which releases the door so it closes the moment the alarm sounds. Wedging or propping a fire door with anything else defeats the protection entirely.
What are the rules for fire doors in the UK?
In England, the building regulations set out where fire resisting construction is required, with the detail in Approved Document B, and fire door products must be tested to British or European standards to prove they perform. On top of that, the Fire Safety (England) Regulations 2022 place duties on responsible persons of multi-occupied residential buildings to check and maintain fire doors in common parts and flat entrance doors. The exact duties depend on the building’s type and height, so you should confirm your responsibilities against current government guidance.
What are the 4 P's of fire safety?
The four P’s of fire safety are commonly given as Prevention, Protection, Preparedness and People. Prevention is reducing the chance of a fire starting. Protection is the built in measures, including fire doors and compartmentation, that limit a fire’s effect once it begins. Preparedness is planning and procedures such as evacuation routes and drills. People is making sure everyone knows what to do. Fire doors sit squarely in the protection element, forming the passive barriers that contain a fire and keep escape routes usable.
Can internal fire doors have glass?
Yes. Internal fire doors can include glass, and aluminium systems are particularly good at it because their slim, strong frames carry large fire rated panes without losing the rating. The glazing has to be the correct insulating fire glass, matched to the tested system with the right thickness and edge cover set out in the classification report. Ordinary glass, or integrity only glass, cannot be substituted into an EI rated door. Done correctly, glazed fire doors bring daylight and open sightlines into a space while keeping the fire compartment intact.
What is the difference between EI and FD ratings?
FD ratings come from the British Standard BS 476 Part 22 and measure integrity, the ability to hold back flames and hot gases, for a set number of minutes. EI ratings come from the European standard EN 13501-2 and classify a door for both integrity and insulation, so an EI door also limits how much heat passes to the safe side. The two are not equivalent even when the minute figure is the same, because an EI rating includes the insulation performance that an FD rating does not. AFS products are EI classified.
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Why Choose Aluminium Fire Systems for Internal Fire Doors
We are a fire rated product specialist. Fire rated windows, doors and glass partitions are not a sideline for us, they are the whole business, and every member of the team from quoting through to manufacturing works in fire rated products day in and day out. That focus is the reason contractors and architects come to us with the openings other suppliers find difficult.
A few things set our fire rated products apart:
- We manufacture in the UK, in house, which gives us control over quality, traceability and lead times.
- We are an approved Aluprof fire partner, so we stay aligned with technical developments and changes in legislation and work with proven, certified systems.
- Our products are EI classified, managing both flame and heat transfer rather than integrity alone.
- Every project is delivered with a full compliance pack built for the golden thread, so you can evidence compliance to building control.
- We buy direct as the manufacturer, which keeps pricing competitive without compromising on quality or service.
If you are weighing up internal fire doors for a project, Aluminium Fire Systems can help you specify the right rating and configuration and supply the evidence to back it up.