Define "combustion" in the context of gas appliances.

Combustion, in the context of gas appliances, is defined as a chemical reaction that occurs when a fuel reacts with an oxidizing agent, typically oxygen, resulting in the release of heat and often producing gases as by-products. In gas appliances, this process is fundamental because it is how energy is generated for heating or cooking.

During combustion, the breaking and forming of chemical bonds produce heat, which is essential for the efficient operation of appliances such as gas stoves, furnaces, and water heaters. The heat generated not only serves to perform work such as heating water or cooking food but also creates exhaust gases that need to be safely vented away from the living space to avoid health hazards.

Other options such as the reaction between fuels and inhibitors reflect a different type of chemical interaction, while physical changes of state do not involve the creation of new substances or the release of energy whereas condensation and evaporation pertain to phase changes of matter rather than chemical reactions. Understanding combustion is crucial for ensuring safe and effective operation of gas appliances, as well as for monitoring exhaust emissions and operational efficiency.