Intumescent coatings, often referred to as intumescent paint, are used in buildings as a passive fire resistance measure. They can be applied to structural members as an aesthetically pleasing fireproofing product.
Intumescent Fireproofing
INTUMESCENT FIREPROOFING
Another type of intumescent product is a firestopping pillow or putty that is used to protect openings from fire.
The key feature of intumescents is that they expand significantly when exposed to high temperatures, such as those found in a fire. Some intumescent products can expand to more than 100-times the original thickness.
As the product expands it becomes much less dense, which makes it act as in insulator that keeps the high temperatures away from structural members or protected openings.
Intumescent products are made of a series of chemicals suspended in a binder. When the binder is exposed to heat it begins to soften, which allows the suspended chemicals to the heat. The chemicals begin to react, which releases vapors that create a foam. A carbonization occurs and the foam solidifies into a black insulating material that is often referred to as char.
The most common use for intumescent paint in architecture is to provide an aesthetically pleasing finish on exposed structural steel members. Typical spray applied fireproofing provides a thick and spongey surface that requires a finished surround to hide and protect the steel member. Intumescent paint provides the same level of protection in a coating that looks like a thin layer of paint.
The paint product is applied to the steel in layers as needed to generate the thickness that corresponds to the level of protection mandated by the building code. A final layer of intumescent paint is mixed with pigments that provide the desired finish color for the steel.
Intumescent coatings are also being used on structural members made of wood. For wood, the protection is not as much about the heat, but more about stopping the spread of flame and smoke. A coating can be applied to provide a rating on the wood member, but only if a painted look is acceptable. If a natural wood look is preferred, intumescent coatings are not a good choice.