Out of all the measures in place to protect a building from fire, fire doors are among the most visible and frequently used and many people do not know the full extent of their role within a fire protection strategy. As well as providing a safe evacuation route, fire doors help prevent a fire from spreading throughout a building partially due to the use of intumescent strips, which play a vital yet little-known role in helping save lives.
Intumescent strips for fire doors are generally designed to provide around 30 – 60 minutes of fire resistance, helping contain the fire in one area and prevent it from spreading. This gives occupants enough time to safely evacuate the building while emergency services work to extinguish the fire.
All fire doors are rated based on their fire resistance features known as an FD rating and is measured based on their ability to hold back fire from progressing further throughout a burning fire compartment.
FD 30 means a fire door has a minimum of 30 minutes of fire resistance, there was a door with a rating of FD60S offers a minimum of 60 minutes of fire resistance and is a smoke sealed door. It is generally accepted that to provide the required level of fire resistance, all fire doors should be reinforced with either intumescent strips, cold smoke seals or a combination of both.
According to the British Standard 476 fire safety standards, most doors need to be smoke-sealed doors and having a fireproof door installed with intumescent strips can help the door qualify for these standards. Seals need to limit leakage to a rate of 3 cubic metres of smoke through 1 metre of door edge per hour.
If a door does not meet the regulatory definition of a fire door, adding intumescent strips alone won’t mean it will provide the same level of protection as a fire door. While nothing is stopping you from installing intumescent strips on a regular door, the door will still fall short of regulatory requirements.
What are Intumescent Strips & How do they Work?
Intumescent Strips are a key part in helping to maintain fire safety standards of door installations. Whilst you may not be aware of them, all new doors are likely to have intumescent strips or brushes installed. But what are Intumescent Strips and how do they work?
Intumescent strips are specially produced seals and brushes that are fitted to the edge of the door frame and, in cases where FD60 fire rating is required they are also installed in the centre of the edges of the door leaf.
The function of these strips or brushes is to form a better seal around the door in the event of a fire. If a fire is present near the door, the heat will force the intumescent strips to expand; forming a more solid seal around the door and making it more difficult for fire and smoke to work its way through.
Fire door intumescent strip regulations
The main point of reference for compliant fire door installations is their fire rating, which would be provided by the manufacturer in the form of testing data. These ratings depict the amount of time that a door can withstand fire damage.
A building’s regulations will also stipulate where its fire doors are, as well as where intumescent strips need to be installed. In a standard fire door, the door leaf has to be able to move within the frame, and for this to be possible, there has to be a small gap around the perimeter.
As a general rule, the gap of a fire door should not be larger than 4mm, and this should be the case for the door’s two long edges, as well as across the top edge of the door leaf. The gap at the bottom of the door must be approximately 10mm for non-smoke conditions, but when smoke seals are in place this gap should be reduced to 4mm. The gap around the door sides, top and bottom is to allow the heat from fire to reach the intumescent strips to ensure they activate and work as intended.
Fitting intumescent strips to fire doors
Fire door seals are fitted to the stiles and head of a door set, either in the grooves of the doorframe or mounted on the surface. They are designed to swell once the ambient temperature exceeds 200°C, which will usually occur within the first 10-20 minutes of a fire. Properly installed intumescent strips will fill gaps between the door and frame to achieve fire compartmentation.
Regulations surrounding intumescent strips also require specific installation and fitting based on your building and fire door type as some doors require a cold smoke seal to protect people and property from smoke damage. In cases where smoke leakage is important to detect a fire, cold smoke seals may not be required.
Maintaining smoke seals and intumescent strips
Like all other fireproofing materials, intumescent strips should never be “set it and forget it.” Intumescent strips can crack, warp, or partially detach from a door with age. They can also sustain damage from door use or building repairs. Therefore, they should be checked at least every six months for imperfections or other issues that might inhibit them from working properly. Any damaged or missing strips should ideally be replaced with a new one of the same size, type and brand as the original.
Specialist Door Solutions Fire Testing
Specialist Door Solutions take fire safety extremely seriously, and therefore intumescent strips are a crucial part of our door installations in hospitals and other public environments.
These strips can give you up to 60 minutes of fire resistance, time which is vital in the event of serious fire incidents.
Interested in Bespoke High Quality Fire Safe Doors?
If you have any questions about the specialist doors we can provide, please get in touch on +441420543222, or email us on sales@specialistdoorsolutions.com. You can also fill in the contact form on our contact page, and someone will get back to you as soon as possible.
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