Abstract: An enclosure for housing electrical equipment is constructed to simplify use of general purpose electrical equipment at a location in a petroleum refinery which may contain combustible vapors. The construction provides an enclosure that is vapor tight except for an open front, thus providing user access and adequate ventilation to equipment such as a computer. In use a combustible gas monitor surveys the relatively small open area at the front of the enclosure and automatically disconnects electric current supplied to the general purpose rated equipment inside the enclosure on detection of a dangerous concentration of combustible gas entering through the front opening.