What feature should electrical units have when operating in areas exposed to flammable vapors?

When operating electrical units in areas exposed to flammable vapors, it is essential that they are explosion-proof. This means that the electrical equipment is designed to withstand internal explosions without igniting the surrounding explosive atmosphere. The construction typically includes sealed enclosures that contain any explosion and prevent ignition sources from escaping. This safety feature is crucial in environments where combustible gases, vapors, or dust may be present, as it significantly reduces the risk of fire or explosion, ensuring the safety of both the equipment and personnel.

While being waterproof, having high insulation, and being rust-resistant can be important aspects of electrical equipment in many contexts, they do not specifically address the risks associated with flammable vapors. Waterproof units are crucial in wet conditions, high insulation helps in preventing electrical failure and corrosion resistance protects against rust, but none of these features provide the necessary protection against potential explosions in hazardous environments.