What happens to intumescent materials in a fire?

Intumescent materials are designed to provide fire protection by responding to heat in a specific way. When exposed to high temperatures during a fire, these materials undergo a chemical reaction that causes them to swell significantly. This expansion creates a thick, insulating char layer that protects the underlying structure or materials from direct exposure to flames and heat. This swelling action not only helps to insulate and impede the spread of fire but also increases the thickness of the material, thereby extending the time it takes for the heat to reach the substrate below. Consequently, the swelling of intumescent materials plays a crucial role in enhancing fire resistance and ensuring the safety of structures.