Which hazardous class includes substances that produce flammable vapor?

Flammable liquids fall under the category of hazardous materials that produce flammable vapor. These substances can easily ignite and cause fires when exposed to an open flame or a spark. The defining characteristic of flammable liquids is their ability to release vapors at certain temperatures that can form ignitable mixtures with air. Understanding this class is vital for handling, storage, and transportation to ensure safety protocols are followed to minimize the risk of fire incidents.

On the other hand, corrosive materials are primarily defined by their ability to damage living tissue or corrode materials, not by their flammability. Explosives are substances that undergo a rapid reaction that produces gas and heat, but they are distinct from flammable liquids, as they involve different mechanisms (detonation or deflagration) and behaviors. Oxidizing agents can enhance the combustion of other materials but are not substances that produce flammable vapor on their own. Thus, the correct classification focusing on flammable vapors is flammable liquids.