Flammable chemicals and petroleum products (eg methane, alcohol, acetylene, gas ...) production, operation, transport and storage of emergence can be gas and vapor leakage of the merger with oxygen in the atmosphere is essential to create an explosive concentration. Such a situation may arise in the electric energy, electric arc, static electricity or extreme surface temperature, can lead to an explosion will endanger the life and property security. The construction and use of electrical equipment used in these hazardous environments varies greatly from the normal field applications. Such materials, professional circles concerned with issues Ex-proof (flameproof) is called electricity supplies.