NEC 500: Hazardous (Classified) Locations
What This Article Covers
NEC Article 500 introduces the classification system for hazardous locations — Class I (gases/vapors), Class II (dusts), and Class III (fibers/flyings) — and Divisions 1 and 2 within each class. Articles 501, 502, and 503 contain the actual installation requirements.
Key Requirements
- Class I = flammable gases or vapors; Class II = combustible dust; Class III = ignitable fibers
- Division 1 = hazard present in normal operation; Division 2 = present only under fault conditions
- Equipment must be listed for the specific class, division, and gas/dust group
- Wiring methods are restricted in each location type
- Seal fittings required where conduit passes from a Division 1 location to another area
Common Field Applications
- Gas station forecourt (Class I Div 2 around dispensers)
- Spray paint booth (Class I Div 1 inside, Div 2 around)
- Grain elevator (Class II Div 1 inside processing)
Common Mistakes & Inspection Failures
- Using ordinary wiring in a classified location
- Missing or improperly poured seal fittings
- Substituting non-listed luminaires
Related NEC Articles
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What does NEC 500 cover?
NEC Article 500 introduces the classification system for hazardous locations — Class I (gases/vapors), Class II (dusts), and Class III (fibers/flyings) — and Divisions 1 and 2 within each class. Articles 501, 502, and 503 contain the actual installation requirements.
What are the key requirements of NEC 500?
Key requirements include: Class I = flammable gases or vapors; Class II = combustible dust; Class III = ignitable fibers; Division 1 = hazard present in normal operation; Division 2 = present only under fault conditions; Equipment must be listed for the specific class, division, and gas/dust group. See the full requirements list on this page.
What are common mistakes with NEC 500?
Using ordinary wiring in a classified location Missing or improperly poured seal fittings Substituting non-listed luminaires
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IBEW Local 134 Journeyman · Licensed Contractor · IL Educator
Michael started in the IBEW at 18 and made foreman as a 3rd-year apprentice. Thirteen years in, he’s a Local 134 journeyman, a licensed electrical contractor, a licensed Illinois teacher, and OSHA 30 and EPA 608 certified. He teaches a federally recognized pre-apprenticeship on the south side of Chicago — where he’s helped 100+ students get into the IBEW. He built Sparky AI around exactly what the NJATC exam tests and what trips people up. Prep with this and you walk in ready.