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Intumescent Strips for Fire Doors
Fire door seals aren't just strips of material. They're your first line of defence when flames threaten lives and property. Intumescent seals expand when exposed to heat, creating an impenetrable barrier that stops smoke and fire from spreading through gaps around your fire doors. What are intumescent seals, and how do they work? Intumescent seals are specialised strips that contain heat-activated materials. When temperatures reach around 200°C, these materials expand dramatically – sometimes up to 20 times their original size. This expansion fills gaps around door frames, preventing deadly smoke and flames from passing through. The science is straightforward but effective. The seal's intumescent material reacts to heat by forming a charred foam that seals gaps completely. This process occurs automatically, providing passive fire protection that remains effective even when nobody is present to activate it. Which fire doors need intumescent seals? Every fire door needs proper sealing to meet building regulations. You'll find intumescent seals are compulsory on: Commercial buildings, schools, hospitals, and residential blocks all depend on these seals. Without them, your fire doors can't achieve their rated fire resistance, leaving you non-compliant and vulnerable. How do you choose the proper intumescent seal? Selecting the correct seal depends on several factors. The door gap size matters most – measure the space between your door and its frame when closed. Standard seals handle gaps from 2mm to 4mm; however, larger gaps require different solutions. Fire rating compatibility is crucial. Your seal must match or exceed the fire rating of your door. A 30-minute door needs seals tested for at least 30 minutes of fire resistance. Consider the door's use too. Heavy-traffic doors need robust seals that won't wear out quickly. Acoustic seals combine fire protection with sound damping for areas that require both. Where should intumescent seals be installed on fire doors? Proper placement ensures maximum protection. Install seals around the entire door perimeter, including the top, sides, and bottom. The meeting style with double doors also requires seals. Most seals fit into grooves routed into the door or frame. Some adhesive strips are suitable for retrofit situations, although routed installations offer better durability. Always follow the manufacturer's instructions for groove dimensions and positioning. Door closers and hinges create potential weak points. Make sure seals run continuously past these areas without gaps. Can you install intumescent seals yourself? Basic installations are straightforward for competent DIY enthusiasts. You'll need a router for groove-cutting and measuring tools for accuracy. However, fire door compliance is serious business. Professional installation guarantees proper fitting and maintains your door's certification. Incorrect installation can void warranties and create compliance issues. When in doubt, use certified installers who understand the requirements for fire doors. How often should intumescent seals be replaced? Regular inspections ensure your fire doors remain compliant. Check seals every six months for damage, wear, or gaps. Look for: Replace damaged seals immediately. Even small gaps can significantly compromise fire resistance. Well-maintained seals typically last 10 to 15 years under normal conditions. What happens if intumescent seals fail? Seal failure can be catastrophic. Smoke spreads rapidly through unsealed gaps, creating deadly conditions before flames arrive. Fire can breach doors in minutes, rather than the rated 30-120 minutes. Legal consequences include prosecution for non-compliance with building regulations. Insurance claims may be rejected if fire doors lack proper seals. More importantly, lives are at risk when passive fire protection fails. Are there different types of intumescent seals? Several seal types suit different applications. Graphite-based seals offer excellent expansion rates and durability. They're ideal for most commercial applications. Hybrid seals combine intumescent materials with acoustic foam for sound control. These work well in offices, hotels, and residential buildings. Brush seals add flexible bristles for better gap filling around irregular door edges. They're particularly useful for older buildings with less precise door fitting. How do intumescent seals compare to other fire door hardware? Seals work in conjunction with other fire door components. Hinges, closers, and locks all contribute to fire resistance. However, seals are often the weakest link when poorly maintained. Unlike active systems that need power or human intervention, intumescent seals work passively. They don't rely on detection systems or electrical supplies. This reliability makes them essential for 24/7 fire protection. Ready to upgrade your fire door protection? Don't compromise on fire safety. Browse our comprehensive range of intumescent seals designed for every fire door application. From basic strips to advanced acoustic combinations, we stock solutions for residential, commercial, and industrial buildings. Order online for fast delivery, or contact our fire safety experts for specification advice tailored to your project. Frequently Asked Questions (FAQs) Can intumescent seals be surface-mounted on existing fire doors? Yes, surface-mounted intumescent strips offer a practical solution for retrofitting older fire doors or replacing damaged seals. These self-adhesive strips attach directly to the door leaf or frame without routing, making them ideal for doors that didn't initially have seals installed. At what temperature do intumescent seals activate? Intumescent seals activate at approximately 200°C, expanding many times their original size to seal gaps around the door. This heat-activated response happens automatically during a fire, creating an effective barrier against flames and smoke without any manual intervention. Do you need different seals for FD30 and FD60 fire doors? Our intumescent seals are designed to resist fire for up to either 30 or 60 minutes, matching FD30 and FD60 fire door ratings, respectively. The seal you choose must correspond to your door's fire rating to maintain compliance and ensure proper protection. Should intumescent seals be fitted to the door or the frame? Intumescent seals can be fitted either way - in grooves routed into the door leaf or the frame. The choice depends on your door type and installation preferences. Both methods are effective when installed correctly according to the manufacturer's specifications. When would you use fire-only seals instead of fire and smoke seals? Fire-only seals are suitable for specific applications, such as broom cupboards without fire alarms that lead to corridors equipped with automatic fire detection. In these cases, you want cold smoke to leak out and trigger the corridor's fire alarm system, alerting occupants. For more detailed information about fire door sealing requirements, read our comprehensive guide on intumescent strips for fire doors.
Read more about intumescent strips for fire doors...
Surface-Mounted Intumescent Strips Kit - 25mm - Fire and Smoke
- Retrofit fire door seals
- Suitable if no rebate for seals exists in the fire door
- Intumescent strip plus smoke brush
- 1050mm long in packs of 5 (single door) or 8 (double door)
- 30 minute fire and smoke (FD30s)
Surface Mounted Drop Down Smoke Seal
- Suitable for gaps of up to 14mm
- No rebating necessary - ideal for retrofitting
- Available in a range of lengths: 330mm - 1030mm
- Supplied complete with fixing screws
Astroflame Door Edge Guards - Rounded
- 30 and 60 minute fire rated versions
- Impact tested to 200kg at 3.5mph
- Tested to BS 476-22:1987
Astroflame Door Edge Guards - Flat
- 30 and 60 minute fire rated versions
- Impact tested to 200kg at 3.5mph
- Tested to BS 476-22:1987
What are intumescent strips?
How intumescent strips work
Types of intumescent strips
What are intumescent strips?
Fire doors are designed in such a way that it creates a barrier, compartmentalising a section or part of a premises, preventing smoke and fire from travelling though one part of the building and quickly onto another. When fire doors are installed correctly, small gaps can be seen between the door and frame which could impair the fire door’s ability to prevent the spread of fire and smoke. Intumescent strips, or intumescent seals, are heat activated seals that are placed on either the edge of the door or the frame to essentially fill these gaps for the event of a fire.
How intumescent strips work
Intumescent strips contain a heat reactive chemical that causes it to swell up when exposed to these conditions, typically in the event of a fire. Activating at around 200°C, the intumescent strips expand to many times its original size, in order for it to “seal” the gap around the door. This in turn, ensures that fire and smoke cannot lip itself around the door and occupy the escape route, making it difficult to escape.
Smoke seals, also known as cold smoke seals, have a distinctive feature of an additional brush that fits around the edges of the door and is usually combined with an intumescent strip. The brush is designed in such a way that even when the fire has not reached the intumescent seals activation temperature, the brush will reduce the amount of smoke that can lip itself around the door, keeping the escape route as clear as possible for as long as possible to not hinder evacuation.
Types of intumescent strips
Intumescent strips are often supplied in either rebated or surface mounted options. Rebated strips can often be found in brand new doors, as a channel is often routed out during manufacture to allow for the strip to be installed when it is being fitted. As the routing is done at the manufacturing stage of the door, it does not void its fire rating. Surface mounted intumescent strips are a solution to replace damaged strips on older fire doors or to be retrofitted on doors that did not originally have seals installed. Intumescent strips are only installed on the top and sides of fire doors, different seals can be fitted to the bottom of the door, should these be required.
Intumescent seals prevent the spread of fire but you may also need smoke seals, in addition to also prevent the spread of toxic smoke. Your fire door inspector, or fire risk assessor, will be able to advise you on which type or types of seals you require for your fire door needs.
Fire Only – Intumescent seals are for use where no smoke seals are required. These are likely to be used for doors that are for a small side room, such as a broom cupboard without a fire alarm, which in turn leads to a corridor with automatic fire detection. On this occasion, it is important that the door allows for the cold smoke to leak from the cupboard into the corridor so that the fire alarm is able to be activated and alert the occupants to the fire.
Fire and Smoke – Fire and smoke seals create a safe and effective barrier against fire, cold smoke, and hot gases produced in a fire. The smoke seal, in particular provides a permanent barrier to toxic smoke, which may impede an individuals’ ability to effectively escape via the emergency routes. This is particularly important as it is key to know that smoke fumes travel faster and further than the fire itself, causing more harm to an individual.