Intumescent strips are fitted to the edges of fire doors. In in extreme heat, these strips expand to seal the gaps between the door leaf and its frame. This allows closed fire doors to act as a barrier to the spread of smoke and flames throughout a building. Therefore, it is essential that fire doors are installed, maintained with their seals intact. They must also be kept shut when not in use.
Intumescent seal on a fire door
Smoke seal vs intumescent strip
‘Intumescent strips’ are embedded in the door, and are dormant under normal conditions. These strips respond to heat, causing them to expand greatly in the event of a fire. This closes the gap between the door and its frame. These seals activate at temperatures that are above human survival levels. Therefore, there is no danger of them expanding and trapping people trying to escape.
A ‘brush’ seal or smoke seal will prevent the escape of cold smoke around the edges of the fire door. While these seals are also intumescent, smoke inhalation can be more dangerous than the fire itself. It is important, when fitting smoke seals, that they do not hinder the full and effective closure of the door.
Do all fire doors need intumescent strips and smoke seals?
In order to be effective, all fire doors must be fitted with intumescent strips. Without these, the door will not ‘seal’ to the frame in the event of a fire. These seals are essential to slow the spread of the fire throughout the building, providing occupants time to evacuate. If intumescent strips are found not to have been fitted in the event of a fire, the Responsible Person could be prosecuted.
Smoke seals, however, are required as specified in the fire risk assessment. Most commonly this is included on doors approaching escape routes and doors which open on to a common space.
All fire doors must have intumescent strips fitted
Why fit intumescent strips and smoke seals?
Intumescent seals only react to extreme heat, so they don’t seal up until the fire is very close. Before this, smoke from the fire which has accumulated will be able to pass through the gaps around the door. This puts building occupants in danger of smoke inhalation, which can be fatal. Smoke seals prevent this, and are typically either a soft brush or a plastic / rubber flap.
When should smoke seals not be fitted?
There are some applications where a gap should not have smoke seals: e.g. if the fire door has been installed on the exit of a room which has no smoke detectors on its own. In this case, the fire alarm system can only be triggered if smoke can leak out around the fire door and set off the fire alarm system in the circulation spaces, but these cases are quite rare.
Fire door ratings and smoke
Fire doors are rated in accordance with the length of time they will resist a fire. Therefore, a door rated ‘FD30’ will resist the passage of fire for 30 minutes, an ‘FD60’ for 60 minutes. If a fire door is rated FD30s, (‘s’ meaning ‘smoke’), it should have been fitted with the appropriate seal to resist the passage of cold smoke for 30 minutes as well. For more information about how fire doors are rated, visit our blog.
Fire door gaps and smoke seals
British Standards set out details on the permitted gaps around a fire door. The gap along the sides, top, and between the leaves of a double door, must be between 2mm and 4mm. Responsible Persons can use a gap gauge to ensure that their fire door gaps are compliant.
Under-door (threshold) gaps should be in accordance with the manufacturer’s installation instructions for the particular doorset design. This blog provides more information about threshold gaps.
Intumescent seals can only be effective with the correct gap size between the door and frame
Can smoke seals be painted?
Fire doors can be painted with ordinary paint. However, fire accessories, including intumescent seals should not be painted, as it can prevent them from being effective in the event of a fire.
Are intumescent strips required in letter boxes?
If a fire door has a letter box installed, this must have been tested and rated to the same standards as the door itself.
If an intumescent letter box needs to be added to a fire door retrospectively, this can only be done if specified in the scope of the fire door’s Certifire Approval documents, and in line with the manufacturer’s instructions. Further to this, alterations can only be made by a trained professional, and with certified hardware. This ensures that the performance of the door, and its associated certification, is not compromised.
What does the threshold drop seal do?
If smoke protection is required by Building Regulations or the fire risk assessment, the maximum gap underneath the fire door is reduced to 4mm. If the gap under a fire door is too large, surface mounted drop-down smoke seals or rebated drop-down smoke seals can be fitted to existing fire doors. When the door closes, a plunger makes contact with the door frame and lowers the seal to the floor, closing the gap under the door. This is usually a suitable solution for gaps of up to 14mm.
Can fire door seals be replaced?
Where a fire door rebate already exists, or the existing rebated fire door seal has been damaged, rebated intumescent fire door seals can be fitted.
Can fire door seals be fitted retrospectively?
Some older fire doors do not comply with the latest specifications. In some cases, this means that they do not have the appropriate intumescent or smoke seals. Fire door seals can be retrospectively added to these fire doors.
To avoid having to cut a rebate in either the door or the frame, surface mounted fire door seals can be fitted. These are stuck to the frame or door with their self-adhesive backing and sometimes nailed as well to give them increased longevity.
Replace intumescent seals if they are damaged
Who can fit fire door seals?
Fire doors should always be professionally installed, as should any work which structurally alters the door or its hardware. Therefore, rebated fire door seals can only be fitted by a qualified professional, whether as a replacement or retrofit.
Surface mounted fire door seals, on the other hand, can be fitted by a ‘Competent Person’. If new fire door seals are fitted for the first time, make sure that fire door hinges, fire door closers and, where necessary, intumescent door lock protection are fitted as well.
Visit our website to see Safelincs’ full range of fire door seals. This includes ‘fire only’ (intumescent) and ‘fire and smoke’ (intumescent and brush) fire door seals. Safelincs supply both rebated and surface-mounted application, in both FD30 and FD60 ratings. If you are still unsure what type of seal your door requires, or whether a retrofit is appropriate for your door, contact our friendly fire door team on 0800 433 4289 or by emailing firedoors@safelincs.co.uk.
Frequently Asked Questions
What is the difference between intumescent strips and smoke seals?
Intumescent strips remain dormant under normal conditions but expand greatly when exposed to extreme heat during a fire. This expansion seals gaps between the door and frame to block flames and hot gases. Cold smoke seals, often appearing as brush or rubber flaps, work differently by blocking smoke at normal temperatures. While intumescent strips activate only at high temperatures beyond human survival levels, cold smoke seals work immediately to prevent smoke from passing around door edges, protecting against smoke inhalation, which can be fatal before the fire itself reaches you. Many modern products combine both functions as intumescent smoke seals, providing complete protection against fire and smoke.
Do fire doors need intumescent seals?
Yes, all fire door sets must have intumescent seals to function correctly. Without these seals, a fire door cannot perform its essential purpose of containing fire within compartments. The lack of proper seals will allow fire to spread quickly through gaps around the door. The Responsible Person could face prosecution if fire doors are found without properly fitted intumescent seals during an incident. Building regulations require these seals to ensure the door achieves its fire rating (FD30, FD60, etc.). Cold smoke seals, while not always required on every fire door, are typically specified in fire risk assessments for doors near escape routes or those opening into common areas.
How do I fit intumescent fire seals?
The fitting method depends on whether you are using rebated or surface-mounted seals. For rebated seals: 1) Ensure the rebate in the door or frame is clean and free from obstructions, 2) Measure and cut the seal to the correct length, 3) Remove the backing from the adhesive strip, 4) Press firmly into the rebate, ensuring it sits flush, 5) Secure with pins if recommended by the manufacturer. For surface-mounted seals: 1) Clean the surface where the seal will be applied, 2) Measure and cut the seal to size, 3) Remove the backing from the adhesive, 4) Apply to the door or frame, pressing firmly, 5) Some seals require additional fixing with pins for long-term security. Professional installation is required for rebated seals, while Competent Persons can fit surface-mounted types. Always check the fire door after fitting the intumescent seals to ensure it self-closes. Adjustments may need to be made to the door if the newly fitted fire door seals prevent the door from closing.
Can fire door seals be fitted to the door instead of the frame?
Yes, intumescent seals can be fitted to either the door or the frame for single fire doors. Both options comply with regulations as long as the seals meet the required fire rating. For double doors or door-and-a-half configurations, the seals should be fitted to the door leaves themselves to ensure the gaps between door leaves are properly sealed during a fire.
What types of intumescent strips are available?
Several types of intumescent strips are available to suit different fire door requirements: 1) Standard intumescent strips (fire-only seals), 2) Combined intumescent and smoke seals (fire and smoke protection), 3) Rebated seals that fit into grooves in the door or frame, 4) Surface-mounted seals that attach to the face of doors or frames, 5) Threshold drop seals for under door gaps, 6) Specifically rated seals for FD30 (30-minute) or FD60 (60-minute) doors. Each type serves specific applications depending on your building regulations requirements and fire risk assessment findings.
Why are cold smoke seals important?
Cold smoke seals provide protection against smoke spread at normal temperatures before a fire heats up enough to activate intumescent strips. This is crucial because: 1) Smoke inhalation causes most fire-related deaths, 2) Smoke travels much faster than fire through a building, 3) Even small gaps around doors allow significant smoke passage, 4) Clear escape routes free from smoke improve survival chances. Combining intumescent strips for fire containment and cold smoke seals for smoke containment provides complete protection.
When should intumescent smoke seals be used?
Intumescent smoke seals, which combine both fire and smoke protection, should be used: 1) On doors along escape routes, 2) For doors opening onto common areas or shared spaces, 3) When specified by your fire risk assessment, 4) In buildings with vulnerable occupants, 5) Where smoke control is critical for evacuation strategy. Some exceptions exist where smoke seals might not be appropriate, such as rooms without smoke detectors where smoke leakage is needed to trigger external alarms. Always consult your fire risk assessment.
What are the requirements for intumescent seals for fire doors?
Fire doors must have correctly specified intumescent seals that: 1) Match the fire rating of the door (FD30, FD60, etc.), 2) Seal gaps of between 2mm and 4mm around the sides and top, 3) Remain unmodified by paint or other coatings, 4) Are correctly fitted according to manufacturer instructions, 5) Remain intact and undamaged. The British Standards set out specific requirements for gap sizes and seal placement. The gap along the sides, top, and between double door leaves must be between 2mm and 4mm.
Can damaged intumescent fire seals be replaced?
Yes, damaged intumescent fire seals can and should be replaced as soon as damage is noticed. Damaged seals compromise the fire resistance of the entire door assembly. For replacement: 1) Remove the damaged seal completely, 2) Clean the rebate or surface, 3) Install a new seal of the same type and fire rating, 4) Ensure proper adhesion, 5) Check fire door self-closes after the new seal is fitted. Rebated seals require professional replacement, while surface-mounted seals can often be replaced by a Competent Person within your organisation.
How do I maintain the intumescent seals?
Regular inspection of intumescent seals is essential for fire safety. Check for: 1) Physical damage or degradation, 2) Proper adhesion to the door or frame, 3) Complete coverage with no missing sections, 4) Signs of tampering or paint overspray, 5) Correct operation of any moving parts on drop seals. We recommend including seal checks in your regular fire door inspections. Replace any damaged seals promptly to maintain fire safety compliance.
Why should I choose Safelincs for my intumescent seal needs?
Safelincs provides quality intumescent seals backed by our commitment to customer satisfaction. Our team can help you select the right seals for your fire doors, whether you need a single replacement or products for an entire building. As winners of customer service awards and the trusted supplier to major organisations, including the Church of England and the Catholic Church in the UK, we offer: 1) Quality products that meet all relevant standards, 2) Expert advice on selection and installation, 3) Competitive pricing, 4) Next-day delivery on many items, 5) Ongoing support for all your fire safety needs. Contact our friendly fire door team on 0800 433 4289 or email firedoors@safelincs.co.uk for personalised advice on your intumescent seal requirements.
Fire safety company Safelincs operates a website called firescout that invites visitors to submit photographs of any potentially dangerous situations they have spotted. All entries are anonymous, the idea being to educate rather than ‘name and shame’. Safelincs then offers advice as to whether the situation could incur a fine and how much, if anything, it would cost to remedy the situation.
A common misdemeanour is to prop open a fire door, sometimes with a fire extinguisher – a double transgression!
Fire doors are an essential part of the fabric of a building and have two important functions in the event of a fire; when closed they form a barrier to stop the spread of fire or smoke and when opened they provide a means of escape. They are designed to be kept closed except when people are passing through them. In some businesses, and in places such as care homes or schools, closed fire doors can act as a hindrance to general mobility and moving around to perform essential tasks. However, there is a way in which the situation can be overcome without compromising safety or breaking the law.
Safelincs provide a number of products manufactured by specialist manufacturer Fireco which allow fire doors to be kept open legally and safely. Each of these products works by responding to the sound (anything above 65 decibels) of a fire alarm; the mechanism holding the door open is released and the door closer on the fire door closes it to prevent the spread of fire and smoke spreading around the building.
Dorgard, the first innovative product from Fireco, is a wireless appliance that can be screwed to the base of a door in less than five minutes. The standalone device will then hold the door open at any angle allowing freedom of access throughout the building. Utilising acoustic technology, Dorgard ‘listens’ for a continuous alarm of 65dBA or higher which, once heard, will automatically release the door. Dorgard is available in a variety of colours and finishes which will blend in with any décor.
Fireco also produces the Dorgard Pro System which extends the versatility of Dorgard by linking several different devices and overcomes the issue of noisy workplaces. A transmitter is wirelessly installed next to a fire alarm sounder or hardwired into the fire alarm system. In the event of a fire, Dorgard Pro will wirelessly transmit simultaneously to multiple Dorgard Pro units within a 100 metre range. Safelincs will visit an organisation’s premises and undertake a free survey and make recommendations for siting an effective system.
Another product from Fireco is Freedor, a unique wire free solution that allows a door to free-swing just like a normal door and to be held open at any angle – automatically closing the door in a controlled manner when a fire alarm sounds. It utilises the same technology that is employed in Dorgard but is fixed unobtrusively to the top of the door. Using Freedor allows freedom of access throughout the building for disabled people and people less able to operate the doors, and assists businesses complying with the Equality Act 2010.
All these products have applications in a wide variety of environments and allow easy movement through a building without compromising safety or contravening fire safety regulations.
To find out more about the Fireco range go to www.safelincs.co.uk and follow the link to Fire Door and Exit Equipment or call 0800 433 4289 where there are friendly experts on hand to offer advice.
Frequently Asked Questions
When is it acceptable to hold a fire door open?
Fire doors should generally remain closed to perform their essential fire safety function. However, it becomes acceptable to hold a fire door open when you use approved fire door holding devices like the Dorgard or Freedor systems. These specialised devices automatically release the door when a fire alarm sounds, allowing the door to close and perform its fire containment function. Without such devices, manually holding or propping open fire doors is not acceptable and may violate fire safety regulations.
What is the purpose of a fire door holder?
The purpose of a fire door holder is to safely keep fire doors open during normal use while ensuring they close automatically during emergencies. Fire door holders like those manufactured by Fireco allow freedom of movement throughout buildings, which is especially beneficial in environments like care homes, schools and businesses where closed doors can hinder mobility and ventilation. These holders respond to fire alarms by immediately releasing the door, allowing the door’s closer mechanism to shut it and prevent the spread of fire and smoke.
Should fire doors be left open?
No, fire doors should not be left open without proper safety mechanisms in place. Fire doors are designed to form barriers that prevent the spread of fire and smoke when closed, and they should only be open temporarily when people pass through them. If operational needs require doors to remain open, you must use approved devices such as Dorgard or Freedor that automatically close the door when a fire alarm sounds. Manually propping or wedging fire doors open is unsafe and could result in prosecution.
When is it acceptable to open a fire door?
It is acceptable to open a fire door when you need to pass through it or when using approved fire door holding devices. Fire doors are designed to allow passage while normally remaining closed. You can temporarily open fire doors manually when moving through the doorway, but they should be fitted with a fire door closer to shut them immediately after use, unless fitted with proper holding devices. If you need to keep a fire door open for operational reasons, you must use approved acoustic or electromagnetic devices that release automatically during fire alarms.
When can you hold a fire door open?
You can hold a fire door open only when using approved fire door holding devices that automatically release upon hearing a fire alarm. Products like Dorgard can be installed at the base of a door in minutes and hold the door open at any angle, releasing it when detecting an alarm of 65dBA or higher. For noisier environments, systems like Dorgard Pro use wireless transmitters connected to fire alarm systems to ensure reliable door closure. Without such approved devices, holding fire doors open with wedges, extinguishers or other objects is unsafe and against regulations.
When is it acceptable to go through a closed fire door?
It is acceptable to go through a closed fire door whenever you need to move between areas of a building during normal operations. Fire doors are specifically designed to allow passage while maintaining fire safety when closed. You should ensure the door closes properly behind you after passing through unless the door is equipped with an approved holding device. During emergencies, fire doors also serve as crucial escape routes, making it not only acceptable but potentially life-saving to go through closed fire doors when evacuating a building.
What is the fine for wedging fire doors open
The fine for wedging fire doors open can be substantial, as this practice violates fire safety regulations. While the specific fine amount varies based on severity and jurisdiction, business owners and building managers can face significant penalties during fire safety inspections if doors are found improperly propped open. Rather than risking these fines, you should consider installing approved fire door holding devices from Safelincs, such as the Fireco range, which allows doors to be held open legally and safely. These solutions cost significantly less than potential fines and provide peace of mind that you’re compliant with regulations.
Is propping open fire doors allowed?
Propping open fire doors is not allowed unless you’re using approved fire door holding devices. The common misdemeanour of propping doors open with objects like fire extinguishers creates a serious safety hazard and violates fire safety regulations. Fire doors are essential building components designed to contain fire and smoke when closed. If you need to keep fire doors open for operational reasons, you should use authorised products like Dorgard or Freedor that automatically release the door when a fire alarm sounds, ensuring the door can perform its vital safety function during emergencies.
What are the fire door regulations for domestic properties and commercial buildings in the UK?
Fire door regulations for domestic properties and commercial buildings in the UK require that fire doors remain closed except when people are passing through them. In commercial settings, fire doors must have appropriate fire resistance ratings and self-closing mechanisms. You must ensure fire doors are not wedged or propped open unless fitted with approved holding devices that release automatically when fire alarms sound. For domestic properties with internal fire doors, similar principles apply, though requirements may vary depending on the building’s design. Both settings require regular inspection and maintenance of fire doors to ensure they function correctly during emergencies.
What type of fire spread can occur if fire doors are propped or wedged open?
If fire doors are propped or wedged open, backdraft conditions can develop, creating an extremely dangerous type of fire spread. When fire doors remain open, oxygen flows freely to the fire, and hot gases and smoke can rapidly spread throughout a building. This situation can lead to backdraft – a phenomenon where a fire smouldering in an oxygen-depleted area suddenly receives a rush of oxygen, causing an explosive ignition. You significantly increase the risk of backdraft and other rapid fire spread scenarios when compromising fire doors by keeping them propped open. Proper fire door holders from Safelincs provide a safe alternative that maintains safety while allowing convenient access.
Fire safety company Safelincs operates a website called