The chemical process that causes production of ignitable vapors from solid wood fuels is called pyrolysis. Pyrolysis is the thermal decomposition of organic materials in the absence of oxygen. When wood is heated in the absence of oxygen, it breaks down into a variety of volatile gases and vapors, including methane, carbon monoxide, hydrogen, and water vapor. These gases and vapors are flammable and can be easily ignited, which is why wood is a good fuel for fires.

The process of pyrolysis begins when wood is heated to a temperature of around 300 degrees Celsius. As the temperature rises, the wood begins to decompose and release volatile gases and vapors. The rate of pyrolysis increases as the temperature increases. At around 500 degrees Celsius, the wood is completely decomposed and all of the volatile gases and vapors have been released.

Pyrolysis is an important process in the production of charcoal, which is a solid fuel made from wood. Charcoal is produced by heating wood in a kiln in the absence of oxygen. The volatile gases and vapors are released from the wood and the remaining charcoal is a solid, porous material that is easy to ignite.

Pyrolysis is also used in the production of wood gas, which is a fuel gas made from wood. Wood gas is produced by heating wood in a gasifier in the absence of oxygen. The volatile gases and vapors are released from the wood and the remaining charcoal is used to produce a combustible gas.