All fixed boxes, fittings, and joints must be explosionproof in which locations?

• A. Class I, Division 1 locations
• B. Class II, Division 2 locations
• C. Class II, Division 1 locations
• D. Class III, Division 1 locations

Answer: (A)

In hazardous locations the required equipment depends on how dangerous the atmosphere is. In Class I Division 1 locations, flammable gases or vapors are present during normal operation, so any fixed boxes, fittings, and joints must be explosionproof to contain any arcing, sparks, or heat inside the enclosure and prevent ignition of the surrounding gas or vapor. This level of protection is what keeps ignition sources from triggering an explosive atmosphere when faults occur. In other classifications, like Division 2 or Class II or III, the hazards differ (such as dust or fibers or gases only under abnormal conditions), so the universal requirement for explosionproof enclosures on every fixed box, fitting, and joint isn’t applied in the same way. Therefore, the locations that mandate explosionproof fixed boxes, fittings, and joints are Class I Division 1 locations.