What modification is required for heating equipment to safely heat flammable materials?

The requirement for heating equipment that is used to safely heat flammable materials is that it must be designed to prevent internal explosions. This is crucial because flammable materials can produce vapors that form explosive mixtures when combined with air. If heating equipment allows for the buildup of flammable vapors, it could lead to an explosion if ignition occurs.

Therefore, equipment designed with proper safety features, such as pressure relief valves, explosion vents, or specific materials that minimize ignition risks, is essential in laboratory settings where flammable substances are used. This design consideration significantly reduces the risk of accidents, ensuring a safer working environment.