What is meant by flame propagation?

Flame propagation refers to the spread of combustion through a medium, which can be a gas, vapor, liquid, or solid. This process is critical in understanding how fires and explosions occur, as it describes how flames travel from one point to another within a combustible mixture or material. Propagation occurs due to the heat generated by the combustion process, which ignites adjacent fuel and maintains the fire. Understanding this concept is essential for assessing explosion hazards and mitigating risks in environments where flammable materials are present.

The other options do not align with the definition of flame propagation. For instance, the extinguishing of flames or the re-ignition of flames deals with the lifecycle of a fire rather than its spread. Likewise, measuring flame temperature is more focused on thermal characteristics, rather than the dynamics of how flames move through combustible media. Hence, the notion of flame propagation is specifically tied to the movement and continuity of combustion within a medium.