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The job of a fire door is to prevent the spread of fire from room to room, and the length of time the door will contain the fire is given in the fire rating of the door. An FD30 door will resist fire for 30 minutes and an FD60 door will resist fire for 60 minutes. The weak point of a fire door is the gap between the door and the frame, and this is where the presence of an intumescent strip is crucial. 

People often ask us if and how intumescent strips can be fitted and we’ve got the answers right here. We should first mention that installing any fire safety seals are best left to professionals. That said, it is possible for you to fit or replace intumescent seals yourself with the right tools.

Intumescent strips can stop the spread of fire and smoke for up to an hour, but they should be regularly inspected to ensure there are no tears or damage. If there is damage present, the strip should be replaced as soon as possible as it’s likely the damage will affect its performance against stopping fire and/or smoke. 

There are different types of intumescent strips, fire only and fire and smoke.


Fire Only

Fire & Smoke


Fire only, as the name suggests, only comes into effect against fire and expands when exposed to heat. The fire and smoke seals expand in the same way, but also have the ability to stop the spread of smoke even before they expand due to the heat of the fire. 

Intumescent strips are generally fitted into the door frame but are sometimes into grooves in the door itself. If you don’t have grooves in your fire door or frame, you can use a router to make a groove suitable for the intumescent strip.

Selecting the appropriate seal using door test evidence is essential, this will identify the size of seal required. The intumescent strip will need to be cut to length, and most will have self-adhesive backing strip to stick easily into the groove.


We have lots of options and colours available in intumescent strips to help them blend into their surroundings. You can browse our selection over here

If you know the specific intumescent strip you’re looking to fit, take a look at our Fitting Guide Library. Here you’ll find access to all of our product installation guides.


Q. Can I fit an intumescent strip to a regular door? 

Yes. However, adding an intumescent strip does not make the door a fire door. For protection against fire we would always recommend a door with a fire resistance rating (FD30/FD60 depending on your building requirements), as well as having intumescent strips in place.


Q. Do I need intumescent strips fitted in the door and the frame? 

No. In the event of a fire the seal will expand enough to close the gap regardless of where it is placed. Seals are not needed on both the door and frame.


Q. Will an intumescent strip without a brush or flipper stop smoke, as it closes the gap between the door or the frame? 

Not always. Smoke can travel without the fire (and heat), and it is the heat that makes the strip expand. Having a flipper or brush present stops the cold smoke from passing through the door. We have a great article about how intumescent strips work with cold smoke if you’d like to learn more.

Still got questions? Check out our Fitting Guide Library or give us a call and speak with one of our intumescent experts for help with your specific project.


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