What country are you in? Check your hazardous area definition code.
Gas detectors are nice, but perform no function in electrical protection. They will detect gas only if they are still functioning after the explosion.
The U.S. National Electric Code classifies specific hazardous locations by use in Articles 511 through 517. Article 500 is also loaded with Fine Print Notes. While not Code requirements [90.5(C]), they are immensely helpful in making a hazardous location safe.
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ABSOLUTE MINIMUM IS CLASS I, DIV 2
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Class I, Division 1. Ignitible concentrations of flammable gases or vapors may exist in the course of normal operations [500.5(B)(1)].
Class I, Division 2. Volatile flammable gases or vapors would become hazardous only in case of an accident or some unusual operating condition — or under certain conditions [500.5(B)(2)]:
Where volatile flammable liquids or gases are handled, processed, or used, but are normally confined within closed containers and the gases would escape only in the case of accidental rupture or breakdown — or by abnormal operation of equipment.
Where ignitible concentrations of flammable gases or vapors are normally prevented by positive mechanical ventilation, but might become hazardous through abnormal operation of ventilating equipment.
Areas adjacent to a Class I, Division 1 location where flammable gases or vapors might occasionally be present unless prevented by adequate positive-pressure ventilation with effective safeguards against ventilation failure.
Protection. You must protect electrical equipment and wiring within hazardous locations [500.7].
Use any of the following:
Explosionproof enclosures (Class I locations)
These withstand and contain the force of an internal explosion — the hot gases within the enclosure cool as they escape [500.2].
Dust-ignitionproof enclosures (Class II locations)
These exclude dusts. They will not permit arcs, sparks, or heat within the enclosure to cause ignition of exterior dust [500.2].
Dusttight enclosures (Class II, Division 2 and Class III locations)
These prevent the entrance of dust or flyings. They have no openings to allow electrical sparks or burning material to escape [500.2 and 502.115(B)].
Purged and pressurized systems
For Class I Locations (containing flammable gases or vapors), these permit general-purpose enclosures [500.2]. For Class II Locations (contains combustible dust), these supply positive pressure to general-purpose enclosures [500.2].
Intrinsically safe systems (all locations)
These are incapable of releasing sufficient electrical or thermal energy to cause ignition of flammable gases or vapors [500.2]. None of the requirements in Articles 501 through 503, or 510 through 516 apply to intrinsically safe system installations, except as required by Article 504.
Nonincendive circuits (Class I, Division 2; Class II, Division 2; or Class III, locations)
These are incapable of releasing sufficient electrical or thermal energy to cause ignition of flammable gases, vapors, or dust [500.2].
Oil-immersed make-and-break contacts (Class I, Division 2)
You can install these in a general-purpose enclosure in an area that doesn't contain explosive or ignitible mixtures under normal conditions [500.2].
Hermetically sealed contacts (Class I, Division 2; Class II, Division 2; or Class III, Division 1 and 2 locations)
You can install these in a general-purpose enclosure in an area that doesn't contain explosive or ignitible mixtures under normal conditions [500.2].
Going the Big Inch!
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