Area Class

Module from the Electrical Engineering Curriculum curriculum.

Module 6 - Area Classification · Learning Objectives · 1. Apply NEC 500 Division system (Class I Div 1, Div 2) · 2. Apply NEC 505 / IEC 60079 Zone system (Zone 0, 1, 2) · 3. Select gas groups: NEC A/B/C/D vs IEC IIA/IIB/IIC · 4. Determine temperature class (T1-T6) by autoignition of fluid · 5. Select enclosures: explosion-proof (XP), intrinsically-safe (IS), purged (Type X/Y/Z) · Division and Zone System Cross-Reference

NEC Div	IEC Zone	Presence of Gas/Vapor	Duration	Typical Location	Example
Class I Div 1	Zone 0	Continuous	>1000 hr/yr	Inside process vessel	Atmospheric tank vapor space
Class I Div 1	Zone 1	Periodic during normal ops	10-1000 hr/yr	Near seals, vents	Pump seal cavity
Class I Div 2	Zone 2	Only during abnormal/failure	<10 hr/yr	Process areas	Pump station platform
Unclassified	Non-hazardous	Not expected	-	Offices, control rooms	Admin building
Gas Groups and Temperature Classes
NEC Group	IEC Group	Example Gas	AIT Range	T-Class Typical	Notes
A	IIC	Acetylene	581F	T2 (572F)	Very energetic
B	IIC	Hydrogen, ethylene oxide	932-1040F	T1 (842F)	Hydrogen service
C	IIB	Ethylene, ethyl ether	914F	T2 (572F)	Olefins
D	IIA	Propane, gasoline, methane	842-1003F	T1/T2	Most HC services

Source: Electrical_Engineering_Curriculum_v1.xlsx · Sheet: Area Class

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