A term applied to an electrical device that is constructed so as to prevent release of vapor-igniting sparks, and which may be installed in an area where the device might be surrounded by ignitible vapors.
An electric pump motor installed in a manhole, just above an underground storage tank, is located in an area where gasoline vapors might normally be present. A spark from the motor could ignite these vapors.
However, pump motors and other electrical devices used in such locations are designed to be explosion proof. This condition is achieved by enclosing the device in a housing capable of withstanding a vapor explosion that might occur within the device.
The housing is also designed to prevent escape of a spark or flash that could ignite vapors surrounding the unit. Explosion-proof devices are further designed so that the external temperature of the housing will not get hot enough to ignite vapors present in the area.
Fire safety codes require use of explosion-proof electrical devices in areas where ignitible vapors could be present.