How does intumescent paint work? Complete Guide

Intumescent paint is a crucial fire protection product used to coat building materials to greatly improve their fire resistance. But how exactly does this unique paint work to slow the spread of flames? This complete guide will explain what intumescent paint is, how it works, and its key applications.

What is Intumescent Paint?

Intumescent paint, also sometimes referred to as fire-retardant paint, is a specialised protective coating that swells up when exposed to heat from a fire. It expands into a thick, insulating char that temporarily blocks heat, flames, and smoke from getting through.

This provides critical time to allow people to escape safely and for firefighters to contain the fire. Intumescent coatings contain certain chemicals that cause this unusual swelling reaction. They also contain binders to hold the coating onto surfaces.

Intumescent paints are available in many forms including oil-based and water-based for both indoor and outdoor uses. They can be tinted to desired colours. When applied correctly to substrates like wood, steel, and drywall, intumescent paints greatly boost fire resistance ratings and prevent the rapid spread of fire and smoke.

Retardant Paint vs Intumescent Paint

While the terms fire-retardant paint and intumescent paint are sometimes used interchangeably, they refer to slightly different products:

  • Fire-retardant paints contain chemicals that inhibit ignition and slow the progression of fire along a painted surface. But they don’t swell up.
  • Intumescent paint contains both fire-retardant chemicals and additional compounds that cause the paint to expand enormously when heated, up to over 100 times the original thickness. This expansion blocks fire.

So intumescent paint provides superior fire resistance compared to standard fire-retardant coatings. The swelling action creates a very effective insulating barrier unlike any other type of paint.

Intumescent Paint Application

Intumescent paint can be applied to many common construction materials to improve their capacity to withstand fire. Some key applications include:

  • Structural steel beams and columns – Intumescent paint applied to steel members can achieve fire resistance ratings over 3 hours.
  • Wood surfaces – Coating timber with intumescent paint limits the spread of flames across the wood’s surface.
  • Drywall – Intumescent paint used on drywall improves fire ratings and reduces smoke spread between compartments.
  • Electrical cables – Cables coated in intumescent paint stay protected for longer in a fire.
  • Pipework and ducting – Applying intumescent paint to pipes and air ducts prevents fire penetrating service shafts and ventilation channels.

The paint is best applied off-site in a factory setting for optimal quality control. It can also be applied on-site, requiring controlled drying conditions before use. Two or more coats are usually required.

What does intumescent paint do?

When standard paints are exposed to high heat from flames, they simply burn off the substrate. Intumescent paint reacts very differently thanks to its special heat-activated chemicals. Here’s a step-by-step overview:

  1. The coating first dries and cures onto the substrate to form a thin protective layer.
  1. Upon reaching around 200°C from a nearby fire, the paint’s unique ingredients activate a chemical reaction.
  1. Rapid expansion occurs as volatile compounds in the layer form inert gases. The paint swells up like bread rising, increasing approximately 50 to 150 times in thickness.
  2. This expanded char insulates the underlying surface. It slows heat transfer and prevents direct flame contact.
  3. The swollen paint chars and hardens into a thick, stable insulating layer. This barrier remains in place protecting the substrate until temperatures exceed 1000°C.
  4. Eventually at very high temperatures, the char will erode away exposing the substrate again to fire damage. But the delay provided is critical.

This remarkable process allows intumescent coatings to temporarily replace destroyed structural capacity and fire resistance of substrates. The extra time enabled by the paint can save lives and property.

Intumescent Paint Testing Service

Responsible builders, contractors and architects will want verification of intumescent paints through standardised fire testing before application. Testing confirms that required fire resistance levels will be met and that the intumescent coating is fit for purpose.

Firestoppers provides professional intumescent paint testing services to validate real-world performance. Our ISO 17025 accredited lab uses full-scale active fire testing methods to evaluate intumescent coatings under simulated fire conditions. This includes:

  • Fire resistance testing to AS1530.4 to determine fire rating times.
  • Assessment of insulation, integrity and load bearing ability criteria.
  • Testing samples for different paint types, thicknesses and substrates.

We thoroughly examine factors like char expansion, surface spread of flame, and temperature transmission. Our fire testing engineers also evaluate durability, adhesion and application.

Technical reports detail the fire performance results for specifications. We maintain close partnerships with major intumescent paint manufacturers.

Intumescent Painting Service

In addition to fire testing intumescent coatings, Firestoppers offers professional intumescent painting services on-site and in our facilities. Our highly experienced teams manage the entire intumescent coating process:

  • Detailed evaluation of substrates and required fire ratings.
  • Specification of suitable intumescent systems and thicknesses.
  • Preparation and repair of surfaces for painting.
  • Multi-coat application of intumescent paint under controlled conditions.
  • Validation testing of completed intumescent coating installations.

We work closely with architects and builders to design and install cost-effective intumescent solutions that provide guaranteed fire performance. Our work is completed to the highest quality standards and to ASFP technical guidance.

For any project requiring upgraded reaction-to-fire performance, rely on Firestoppers intumescent coating services backed by full-scale fire testing expertise. Contact our team today to discuss your needs.

Benefits of Intumescent Paint

Using intumescent paint is one of the most effective ways to improve fire resistance and slow the spread of flames. Here are some of the key benefits intumescent coatings provide:

  • Greatly increased fire resistance periods – Intumescent paint can prevent fire damage to substrates for periods over 3 hours depending on the thickness applied. This provides vital additional time for building evacuation.
  • Excellent thermal barrier – The expanded intumescent coating insulates surfaces underneath for prolonged periods from heat and flame contact. This prevents or delays structural failures.
  • Reduces smoke spread – The protective char formed by intumescent paint inhibits smoke penetration between compartments, especially through cracks and openings.
  • Versatile applications – Intumescent paint can be used to boost the fire resistance of many common building materials such as steel, timber, concrete and more.
  • Available in various colors – While traditionally white or off-white, intumescent coatings can now be supplied in many colors to match building décor.
  • Ease of application – Modern intumescent paints go on easily with conventional spray or roller application. They provide even, consistent coverage on-site or off-site.
  • Enhances active fireproofing – Used together with sprinklers and alarms, intumescent paint improves overall fire protection for more resilient buildings.
  • Cost-effective upgrade – Applying intumescent paint is an affordable way to upgrade existing buildings to comply with new fire safety regulations.

Intumescent coatings provide a simple, reliable passive fire protection solution. They represent a wise investment given their proven capacity to save lives and property in building fires.

Passive Fire Safety Experts 

Firestoppers is the leading provider of passive fire protection products and services in Ireland.

Our team of highly qualified fire engineers, technicians and installers are experts in designing comprehensive firestopping systems for commercial, industrial and residential buildings. We utilise only rigorously tested, certified fire protection products from major global brands.

Firestoppers is fully accredited to ISO 17025 standards for testing fire rated assemblies. We also hold all necessary accreditations to design, supply and install passive fire products to meet building codes and safety regulations. Firestoppers operates its own on-site fire test furnace facilities.

For any project requiring firestopping, fireproofing, or intumescent coatings, rely on Firestoppers to deliver the highest quality solutions with guarantees. Contact us today or visit our website to learn more.

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