What does pyrolysis refer to in the context of combustibles?

Pyrolysis refers to the process in which organic materials are thermally decomposed in the absence of oxygen. In the context of combustibles, this means that pyrolysis can lead to a lowering of the ignition temperature as a material ages and is subjected to heat. As materials undergo pyrolysis, they break down into simpler compounds, which can ignite more easily when exposed to flame or heat, thus reducing the temperature needed for ignition. This can be particularly relevant in the context of materials that have been stored or have been subjected to varying environmental conditions over time.

Understanding this process is crucial when dealing with storage and handling of combustible materials, as it highlights how materials can become more hazardous under certain conditions. It helps in recognizing the importance of managing the aging of combustibles and controlling their exposure to heat. The other options describe concepts related to combustibles but do not accurately define pyrolysis in terms of the processes that lead to changes in ignition temperatures.