Special Occupancies, Special Equipment, and Hazardous Locations
Core concepts
Articles 500 through 506 define classified locations. Class I is flammable gas or vapor, Class II is combustible dust, Class III is ignitable fibers. Division 1 means the hazard is present under normal conditions; Division 2 means it is present only under abnormal conditions or is contained. The zone system (Zones 0, 1, 2 for gas; 20, 21, 22 for dust) is an alternative classification. Equipment must be identified for the class, division or zone, and group, and 500-series rules control sealing, wiring methods, and boundary distances.
Other special-occupancy articles frequently tested include 511 commercial garages, 513 aircraft hangars, 514 motor fuel dispensing, 517 health care facilities, 520 places of assembly, 680 pools and fountains, and 690 solar photovoltaic systems. Special equipment includes 625 electric vehicle charging, 680 pool equipment, and 705 interconnected power production.
Separately, remember that GFCI protection (210.8) and AFCI protection (210.12) expand with each code cycle. Dwelling-unit kitchen, bathroom, garage, outdoor, and laundry receptacles all require GFCI, and most 120 V branch circuits in dwelling units require AFCI.
Traps
- Confusing Division 1 with Division 2 - normal versus abnormal conditions.
- Applying 210.8 to receptacles that are not in the listed locations.
- Assuming any "explosion-proof" fitting is acceptable in a dust location.
Rule of thumb
For hazardous locations, verify three things at once: class, division or zone, and group. If any one element is missing from the equipment marking, it is not suitable.