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Intumescent Sealant

Intumescent Sealant

A Guide to Passive Fire Protection

Intumescent Sealant is an excellent tool to help protect against the damage caused by fires. The extreme heat triggers the sealant to expand to 40 times its original size. The sealant can burn for up to 240 minutes, preventing the fires from spreading to other areas causing further destruction

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Intumescent Sealant - A Guide to Passive Fire Protection

Fire spreads fast. It can take 30 seconds from the time fire ignites for it to burn out of control. Intumescent sealant can slow the spread down.

If you’re looking to add an extra layer of passive fire protection and fire safety to your building, read on to find out what is an intumescent sealant and how it can help.

What Is Intumescent Sealant?

An intumescent sealant is a form of passive fire protection that slows down the burning process and doesn’t aid the spread of flames. This helps reduce the damage to structures and gives firefighters more time to arrive and get the fire under control. 

Intumescent sealants are also known as expansion sealants. The extreme heat of the fire triggers a chemical reaction which causes the sealant to expand up to 40 times its original size. It forms a char layer by increasing in volume but decreasing in density.  

What Is the Benefit of Intumescent Sealant?

Intumescent sealant is a flame retardant that creates a thermally insulating layer. It can resist burning and smoke for up to 240 minutes, depending on the surface it’s applied to. The sealant won’t catch fire but does burn up eventually, though much slower than regular building materials.

You may wish to combine this protective measure with others such as fire batts or fire collars and wraps.

What Are the Applications of Intumescent Sealant?

While you can’t coat the entire inside of your building in intumescent sealant, you can use it strategically to halt fire in its tracks for a limited time. Common applications include linear gap joints, penetration seals, movement joints and compartment walls, for example:


Using intumescent sealant around windows will prevent the fire from spreading outside. It will also block off the flow of oxygen from outside that would feed the fire and make it spread faster.


What is intumescent sealant used for in relation to fire doors? Fire doors are sealed with intumescent sealant for two reasons. Fire will be kept from spreading beyond the doorway. Not only does this inhibit the fire’s progress, but it also keeps the evacuation routes open.


There is no gap too small for fire and smoke to pass through. Seal the openings made through walls for cables to run through to stop the spread of both. Some products are suitable for sealing cable trays and cables.

Plastic Piping

Fire collars are usually needed for pipes that go through walls. Using intumescent sealant does away with the need for a fire collar while offering the same level of fire resistance.

Smoke Versus Fire - Which Is More Dangerous?

During fires, fatalities are more often the result of carbon monoxide poisoning and smoke inhalation than burns and other fire-related injuries. Smoke is known as the ‘silent killer’ as it claims 50-80% of fire-related deaths. Smoke inhalation causes burns to the respiratory systems.

Fire retardant measures such as fire doors will slow down the progression of flames, but smoke can seep in through the smallest gaps. It only takes seconds for it to fill the room and poison those inside. Smoke travels and will reach all parts of the building unless it’s contained. 

This dynamic poses a huge threat to buildings with a central access corridor such as hospitals, blocks of flats or schools. A fire under these conditions puts many lives at risk of smoke inhalation and carbon monoxide poisoning

A building sealed with intumescent sealant reduces the impact of smoke-related casualties significantly.

International Standards for Building and Structure Fireproofing

Fire safety and adherence to fire safety regulations is an essential part of building construction, with preference given to products with a good international and national fire safety rating. Standards are usually based on time/temperature curves. They consider the level of insulation and integrity, as well as flammability or the contribution to flame or smoke production.

European standard EN 13501 – 2 is the most relevant standard used in Europe and North America.

It uses a classification from A to F, which is based on how much the substance contributes to the spread of flames.

Passive Fire Protection

Compartmentation is an effective method of passive fire protection. The aim is to contain the fire at the point of origin, thereby slowing the spread of flames and smoke.

Intumescent sealant is a crucial element of a passive fire protection system. For complete fire protection, Fire compound, fire barriers, batt and mastic, and fire doors are other means of passive fire protection.

Where Not to Use Intumescent Sealer

Intumescent sealer isn’t suitable for applications that would be immersed underwater permanently. Avoid using it in areas that are subject to constant abrasion.

Contain Fire, Slow the Progress

Fire is a destructive force that can cause major property damage and claim lives. Because of this, UK Building regulations require all new buildings and refurbishments to incorporate passive fire protection measures.

Now that you know the answer to the question of what is intumescent sealant, you can incorporate it into your fire protection strategy.

If you need advice regarding using intumescent sealant or other passive fire protection measures, contact us today, and one of our knowledgeable staff members will be happy to advise you. 

We also offer installation services carried out by our fully trained NVQ Level 2 engineers. Visit our fire stopping installation page to find out more.

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