Although the North American term “explosionproof” and IEC term “flameproof” are identical concepts, the
requirements in the product standards are different. Explosionproof is a Div. 1 technology which can be
used in a NEC or CEC defined Zone 1 environment. Flameproof is a Zone 1 technology and can not be used in a Div. 1 environment.
Since flammable gases and vapors are expected inside an enclosure, the equipment must be capable of withstanding an explosion caused by sparking contacts of
devices, high temperatures, or an electrical fault. The enclosure is designed so that hot gases generated during an internal explosion are cooled below the ignition
temperature of the surrounding flammable atmosphere as they escape through the joints of the unit.
In addition, the external surfaces of the enclosure must not become hot enough to ignite the surrounding atmosphere due to heat energy within the unit. This heat
energy may be the result of normal operation of heat-producing equipment, or the result of an electrical arc to the enclosure from an arcing ground fault. Safety
factors are applied to all testing of this type of enclosure to ensure the unit will not rupture as a result of an internal explosion