5.1 Hazardous Locations & Conduit Seal Fitting Rules
Classify hazardous environments (Class I gases, Class II dusts, Class III fibers) and apply 18-inch conduit sealing rules to prevent explosion propagation.
Key Blueprint Takeaways
- Class I locations contain flammable gases or vapors; Class II contains combustible dust; Class III contains ignitible fibers.
- Conduit seals must be placed within 18 inches of arcing enclosures in Class I, Division 1 areas.
- Explosionproof enclosures contain internal explosions without igniting the surrounding hazardous atmosphere.
NEC Articles 500 through 516 govern locations where fire or explosion hazards may exist due to flammable gases, vapors, liquids, or combustible dusts.
Conduit seals (EYS/EZS fittings) are packed with Chico compound to block flammable gases from traveling through raceways from hazardous areas to unclassified areas, and to isolate ignition sources within 18 inches of arcing switches.
Knowledge Checkpoint • Section 5.1
In a Class I, Division 1 hazardous location, what is the maximum distance from an enclosure containing arcing parts, switches, or relays that a conduit seal must be installed under NEC 501.15(A)(1)?