What type of fire hazard is involved with a vapor cloud explosion?

A vapor cloud explosion is primarily associated with a gas combustion hazard because it occurs when flammable vapors—often from liquids that have evaporated—mix with air in the right proportions. When these vapor clouds reach an ignition source, they can ignite and lead to an explosion. This type of hazard is linked to the combustion of gases created from the evaporation of volatile substances, demonstrating the critical role that the gas phase plays in such explosive scenarios.

In contrast, solid combustion hazards typically involve ignition and burning of solid materials, which is not relevant to vapor cloud explosions. Liquid combustion hazards relate to the ignition of liquid fuels, which could produce vapors that contribute to a vapor cloud, but the explosion itself is primarily driven by the gas phase. Thermal radiation hazards involve the exposure to heat energy released by a fire or explosion but do not encompass the process of how a vapor cloud explosion occurs, as it focuses more on the resultant heat effects rather than the combustion mechanism itself.