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Intumescent coatings are part of an effective passive fire protection system. When exposed to extreme temperatures, it quickly expands to protect the surface on which it is applied. This can prevent, minimize or delay fire damage to the building structure, and ultimately provide occupants with a safe evacuation time.

In this guide, Alex Chenery-Howes from CLM Fireproofing explains in more detail how intumescent coatings work, the materials they protect and how to apply them.

Due to the endothermic reaction, the intumescent coating can protect the surface. They absorb heat energy from the surrounding environment and undergo chemical processes, thereby rapidly expanding (the Latin word for expansion "tumesco" actually means "expansion"). Generally, thin film coatings of intumescent coatings will swell at a rate of 50:1, while thick film coatings will swell at a rate of 5:1. This expansion produces a microporous carbonaceous foam, which effectively slows down the heat transfer rate from the fire to the underlying surface.

At the same time, the intumescent coating also has an active cooling effect on the substrate in the event of a fire. They contain hydrates, which decompose when exposed to high temperatures, releasing water vapor to cool the surface below.

Intumescent coatings are rated based on how long they can effectively withstand temperatures above 250°C-this is the approximate temperature at which the endothermic reaction occurs.

Paints are usually classified as 30, 60, 90 or 120 minutes-these times represent the longest time a paint can provide effective passive fire protection against extreme temperatures. Which paint you choose depends on the exact purpose it should serve.

Intumescent coatings can be used to protect a variety of materials, including steel, wood, concrete, and composite materials. Here are some ways to use it with these materials.

The critical temperature of steel is between 350°C and 750°C. This is the temperature at which its nominal tensile strength and load-bearing capacity are significantly reduced, thereby increasing the risk of structural collapse. Intumescent coatings can be applied to a range of steel elements to extend the time required to reach the critical temperature. These elements include beams, columns, brackets and studs.

The most effective way to apply intumescent coatings to steel structures is spraying. It can be used as a base layer to be directly coated on the steel surface, or coated on a compatible anti-corrosion primer. For aesthetic reasons, a top coat can also be added, but it must be approved for use in combination with an intumescent coating.

Wood structural elements (such as beams) scorch at a rate of 0.8 mm/min and release combustible gas, which further contributes to fires. Despite some natural fire-resistant properties, wood can be fire-resistant by applying a thin-film intumescent coating.

Intumescent paint can be directly applied to the surface of the wood structure by brush, roller or spraying. There are a variety of transparent intumescent coatings that can be used on wood to maintain its appearance.

As a non-combustible, non-toxic, and low thermal conductivity material, concrete is very fire-resistant. Although its precise fire resistance depends on factors such as its density, moisture content and thickness, it can usually withstand temperatures exceeding 900°C without a significant negative impact on its load-bearing capacity.

Intumescent paint can be applied to the concrete surface by brush, roller or spraying. Paint is usually applied to concrete ceilings and walls to limit and control fire damage. When combined with other separation technologies (i.e. fire sealant), it can significantly improve the passive fire protection performance of concrete structures.

Whether used in residential or commercial buildings, intumescent coatings can improve the passive fire resistance of the structure. By slowing the transfer of heat from the fire to the internal structure (various materials), it helps maintain the integrity of the building and ensures more time for occupants to evacuate.

You can also find more advice on intumescent coatings on the Professional Fire Protection Association (ASFP) website. The organization regularly produces and updates guidance on passive fire protection techniques for engineers and fire safety professionals, including the use of intumescent coatings in specific situations. For example, its latest guidance notes are related to the protection of structural steel. 

More passive fire protection recommendations can be found from the following link

Relive this webinar not to be missed and listen to Niall Rowan of ASFP, Jonathan O'Neill of FPA, Dennis Davies of FSF and Ian Moore of FIA on how COVID-19 affects the fire safety department. Listening to the present is essential.

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