Zone System vs Division System
Side by side comparison: how they work, where each fits, and which to choose.
Quick answer: The zone system (IEC, ATEX, NEC 505) uses three levels for gas; the North American division system (NEC 500) uses two. Zones 0 and 1 roughly match Division 1, Zone 2 roughly matches Division 2.
Zone System vs Division System: Comparison Table
| Aspect | Zone System | Division System |
|---|---|---|
| Gas levels | Zone 0, 1, 2 | Division 1, 2 |
| Dust | Zone 20, 21, 22 | Class II Division 1, 2 |
| Gas groups | IIA, IIB, IIC | Groups A, B, C, D |
| Used in | IEC countries, India, Europe, NEC 505 | USA, Canada (NEC 500, CEC) |
| Equipment marking | Ex code with EPL | Class, Division, Group |
Choose Zone System when
- Projects under IEC, ATEX, PESO or IECEx
Choose Division System when
- Projects in North America using NEC 500
Key Differences Explained
Equipment approvals are not automatically interchangeable. A Zone 1 certificate does not by itself prove Division 1 suitability, and the reverse.
Gas group lettering differs: IIC covers hydrogen and acetylene, which are Groups A and B in the division system.
Related Glossary Terms
Free Calculators
Free Tools
Free Downloads
Frequently Asked Questions
What is the difference between Zone System and Division System?
The zone system (IEC, ATEX, NEC 505) uses three levels for gas; the North American division system (NEC 500) uses two. Zones 0 and 1 roughly match Division 1, Zone 2 roughly matches Division 2.
Is Zone 2 the same as Division 2?
Similar in concept, but not identical in definition or approval.
Which does India use?
The zone system under IS/IEC 60079 and PESO approval.
Can the US use zones?
Yes, NEC 505 allows the zone system.
Learn more on the blog
Hazardous area classification zones
A practical guide on instrumentationblog.in that goes deeper into this topic with field examples.
Read Full ArticleMore Comparisons
All comparisons · Instrumentation glossary