What Are Intumescent Strips?
Posted: 18/11/2022
4 minute read
What are intumescent strips?
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What Are Intumescent Strips?

You may be under the assumption that by simply having a working fire door, you are fully compliant with all fire safety regulations. This is false; all fire doors also require intumescent strips. But what are intumescent strips and how are they installed? Surrey Tech Services Ltd is here to answer all of your questions.

An intumescent strip is a chemically designed product fitted to the frame of a fire door, intended to help prevent the spread of fire. In the event of a blaze, the intumescent strips will expand to close the gap between the fire door and the frame. This ensures a snug fit that prevents the fire from encroaching on evacuation routes and maximises the effectiveness of your fire doors. Most strips are able to withstand a fire for 30-60 minutes.

What are intumescent strips?

Do all fire doors need an intumescent strip?

Yes, all fire doors require intumescent strips. The Regulatory Reform (Fire Safety) Order 2005 establishes that all non-domestic premises must be fitted with appropriate fire doors. Additionally, a fire risk assessment is required by law for a building to be deemed fire safe. During this assessment, your fire doors will be examined for several factors, including the effectiveness of the intumescent strips. Should a fire door not have intumescent strips or be fitted with defective ones, the Responsible Person for the building will be found in breach of the Fire Safety Order and could be found liable.

How to fit intumescent strips

Modern fire exits already have pre-cut channels to make installation of intumescent strips simpler, however surface-mounted seals can be used on older doors. Intumescent strips are easy to install and require little equipment; you will only need a knife or scissors.

However, most modern fire doors can be ordered with the intumescent strip already in place. In order to ensure you’re meeting your legal obligations, you always need a competent professional to carry out the installation of fire doors and the associated intumescent strips. That’s because a professional will be able to adhere to the specific British Standard for installation, giving you full confidence. 

At Surrey Tech Services Ltd, we have a trained and skilled team to handle all your fire door and intumescent stip installation requirements.

Intumescent strips regulations

According to British Standard 476 regulations, most fire doors should be smoke-sealed. Adding intumescent strips will help a fire door to comply with these standards. Intumescent strips should be fitted to all four sides of the door for maximum effectiveness and the gap between door and frame must be suitable; it should be 3mm or less along the sides and top and 10mm at the bottom.

Difference between intumescent strips and smoke seals 

Difference between intumescent strips and smoke seals

When exposed to extreme temperatures, intumescent strips expand to provide an extra layer of protection. They are mainly effective in protecting those evacuating from the intense heat and in assisting fire compartmentation. This contrasts with smoke seals, which only block smoke and offer no extra protection against fire. However, smoke seals are vital for avoiding the intake of toxic fumes; smoke inhalation is one of the leading causes of death in a fire so this can prove critical. 

Smoke seals and intumescent strips are positioned in the same place but a smoke seal is always visible. It is sensible to use both devices in conjunction with each other to make your fire door as robust as possible.


For the safety of all building occupants, it’s vital to ensure your fire door is fully compliant with all safety regulations. At Surrey Tech Services, we have been operating in commercial premises across Surrey, London and the Home Counties since 2014 and have a BAFE-accredited team with a wealth of experience.

To arrange installation of fire doors with intumescent strips or discuss your fire safety needs with a specialist, contact us today.

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