What happens to wood molecules during Stage II of combustion?

During Stage II of combustion, wood molecules begin to vaporize as the temperature rises. This stage is characterized by the thermal degradation of the wood structure, leading to the breakdown of complex organic molecules into simpler compounds, including gases and smoke. As the heat continues to build, moisture is driven off, and the volatile compounds within the wood are released as a gas. These gases are primarily composed of water vapor, carbon dioxide, and various organic compounds, which are essential to the combustion process, as they will eventually ignite and contribute to the flames.

This vaporization is a critical step in combustion for wood because it prepares the material for the ignition phase that follows, where the gaseous byproducts will mix with oxygen and combust. Understanding the transformation of wood into gas helps in studying fire behavior and controlling efficient burning in fireplaces and stoves.