Chimney Safety Institute of America (CSIA) Certification Practice Test

During the burning of wood, which stage involves the release of volatile gases?

1. Drying

2. Pyrolysis

3. Combustion

4. Cooling

The correct answer is: Pyrolysis

The stage that involves the release of volatile gases during the burning of wood is pyrolysis. This stage occurs when wood is heated in the absence of oxygen, causing it to break down chemically. As the wood is subjected to heat, it undergoes thermal degradation, resulting in the formation of gases such as water vapor, methane, acetic acid, and other organic compounds. These gases can then ignite and contribute to combustion if there is enough heat and oxygen present. Understanding pyrolysis is essential in the context of combustion as it prepares the wood for the subsequent combustion stage, where the volatile gases released can burn if conditions are suitable. This highlights the importance of each phase in the burning process, with pyrolysis serving as a critical precursor to the flames we see during burning.