Understanding Intumescent Coatings

In recent years, fire safety has become a top priority for commercial and residential buildings.

One critical aspect of fire safety is passive fire protection, which helps to contain fires, limit their spread, and ensure occupants have time to evacuate. This article will examine intumescent coatings and their role in passive fire protection. We will discuss what they are, how they work, their benefits, and how they can be applied to various surfaces.

What Are Intumescent Coatings?

Intumescent coatings are specially formulated paint-like substances that expand when exposed to high temperatures. This expansion, in turn, creates a protective char barrier that insulates the underlying material from the heat of a fire. 

Intumescent coatings are widely used in the construction industry to protect steel structures, timber, and other combustible surfaces. Protecting the integrity of the structural elements of a building allows more time for occupants to escape and emergency services to respond.

How to Do Intumescent Coatings Work?

Intumescent coatings contain three primary components: acid source, carbon source, and blowing agent. 

When exposed to heat, these components react to form a foam-like char that expands in volume, typically 15-30 times its original thickness. This char barrier insulates the underlying material from the heat, thus delaying its ignition and structural collapse.

The Importance of Expansion

Expansion in intumescent coatings is crucial to their effectiveness in passive fire protection. The char barrier’s thickness provides insulation, limiting the heat transfer to the protected material. This delays the onset of material deformation, providing valuable time for occupants to evacuate and fire suppression systems to take effect.

Benefits of Intumescent Coatings in Passive Fire Protection

Intumescent coatings offer several advantages over other passive fire protection solutions, such as:

Aesthetic Appeal

Intumescent coatings can be applied in thin layers, allowing the architectural details and design of the underlying surface to remain visible. They can also be painted over with regular paint, enabling them to blend seamlessly with the surrounding décor.


Intumescent coatings can be applied to various materials, including steel, timber, and concrete. They are suitable for interior and exterior applications, making them a versatile solution for passive fire protection.

Ease of Application

Intumescent coatings can be applied using conventional painting equipment like brushes, rollers, or spray systems, making them an accessible choice for construction projects, maintenance, and retrofits.

Application of Intumescent Coatings

Proper application is crucial to ensure intumescent coatings’ effectiveness in passive fire protection. Factors to consider include surface preparation, coating thickness, and curing time.

Surface Preparation

Before applying intumescent coatings, surfaces ought to be clean, dry, and devoid of contaminants such as grease or rust, ensuring optimal adhesion and performance of the coating.

Coating Thickness

The thickness of the intumescent coating plays a critical role in determining its effectiveness in fire protection. Manufacturers supply guidelines for the necessary dry film thickness (DFT) based on the specific product and application.

Curing Time

Intumescent coatings demand sufficient curing time to develop their protective properties fully. This period varies depending on the product, ambient temperature, and humidity, and adhering to the manufacturer’s recommendations guarantees optimal performance.

Common types of intumescents

Intumescent paint (coatings) comes in a few variations, and each variant is tailored to the surface to which it will be applied.

Water-based Intumescent 

Water-based coatings are by far the most eco-friendly option. Because of their water content, they also smell less than their chemical counterparts. 

The downside is that these coatings are less tolerant to humidity and low temperatures due to their high water content, which results in a longer drying time, particularly in dry environments.

Solvent-based Intumescent

Solvent-based coatings are often used in semi-open environments and are much more resistant than water-based coatings against the elements. They also dry substantially faster, which gives a smoother, more aesthetically pleasing finish.

Epoxy-based Intumescent

Epoxy coatings are easily the most robust and weather resistant. Epoxy coatings would typically be used in environments subject to the worst weather/environmental conditions (offshore rigs, marine industry and chemical plants)

Epoxy intumescent comes in two applications that cause a chemical reaction when combined. This chemical reaction results in a thick, robust film that insulates the surface on which it is applied. 

Epoxy-based solutions are extremely corrosion and weather resistant.

What is a Hybrid Intumescent Paint?

In 2014 a new range of “Hybrid” Intumescent paint was released. This new technology allows for faster cure times with multiple coats while offering the same fire protection level.

Intumescent Coatings – A Key Component in Passive Fire Protection

In conclusion, intumescent coatings are vital in passive fire protection, offering a practical and versatile solution. 

Expanding in response to heat and forming a protective char barrier, they help delay the ignition and deformation of underlying materials, providing valuable time for evacuation and fire suppression efforts.

With proper application and adherence to manufacturers’ guidelines, intumescent coatings can significantly contribute to the overall fire safety strategy of a building. As awareness of their benefits grows, we expect to see even more incredible future advancements and applications of this innovative technology.

Passive Fire Protection Dublin

If you are looking to upgrade your system, install a completely new system or would like some advice on what’s required to protect your business from fire risk, Firestoppers can help. Contact us today to speak to a member of the team. 

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