Intumescent

[1] Intumescent materials are typically used in passive fire protection and require listing, approval, and compliance in their installed configurations in order to comply with the national building codes and laws.

Typically the light char consists of microporous carbonaceous foam formed by a chemical reaction of three main components: ammonium polyphosphate, pentaerythritol, and melamine.

[2] The reaction takes place in a matrix formed by the molten binder which is typically based on vinyl acetate copolymers or styrene acrylates.

Once the water is spent, the insulation characteristics of the char that remains can retard heat transfer through the fire stop assembly.

Soft char products are typically used in thin film intumescent materials for fireproofing protection of structural steel as well as in firestop pillows.