The process by which a material is decomposed, or broken down, into simpler molecular compounds by the effects of heat alone.

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NOTES

Thermal pyrolysis is the process by which a material is decomposed, or broken down, into simpler molecular compounds by the effects of heat alone. (NFPA 921, Pg. 17)

Pyrolysis typically starts between 100ºC to 250ºC.Fuel pyrolysis vapours are the "fuel vapours" that burn in a fire.

If the pyrolysis happens in the presence of oxygen, which is commonly the case in fires, it is called oxidative pyrolysis in which case vapours will be composed of different materials than when only thermal pyrolysis takes place.

In addition to the formation of flammable vapours some materials like wood and some plastics will also char.

Char is a carbonaceous material that builds up when a solid fuel is burned or pyrolyzed, char has a blackened appearance.(NFPA 921, Pg. 14)

It is this char that reacts directly with oxygen on the surface during the non-flaming combustion clip we saw earlier in this module.