Standards and regulations
Class I Div 1 and Div 2
Also known as NEC Class I Div 1, NEC Class I Div 2, Class I Division 1, Class I Division 2.
Class I Div 1 and Class I Div 2 are the US National Electrical Code (NEC) classifications for hazardous areas where flammable gases or vapours are or could be present. The NEC framework is the dominant US standard, paralleling but not identical to the ATEX / IECEx zone system used in the rest of the world.
NEC classes and divisions
| Classification | Equivalent ATEX zone | Description |
|---|---|---|
| Class I Div 1 | Zone 0 / Zone 1 | Flammable gas / vapour present in normal operation |
| Class I Div 2 | Zone 2 | Flammable gas / vapour not present in normal operation |
| Class II Div 1 | Zone 20 / Zone 21 | Combustible dust present in normal operation |
| Class II Div 2 | Zone 22 | Combustible dust not present in normal operation |
| Class III | n/a | Ignitable fibres (textiles, fine wood) |
NEC also adopts the IEC zone system (Zone 0/1/2 for gas, Zone 20/21/22 for dust) for newer installations alongside the legacy Class/Division system.
Practical implications for sonic horns
US power-plant and refinery sonic-horn purchases routinely specify Class I Div 2 or Class II Div 2 certification depending on the application. European-sourced horns typically carry both ATEX and a third-party-certified NEC equivalent to satisfy US buyers.
Related terms
Related terms
- ATEX directiveThe ATEX directive sets EU requirements for equipment used in explosive atmospheres. Categorises zones 0/1/2 (gas) and 20/21/22 (dust); industrial sonic horns are routinely certified for Zone 20/21/22 dust service.
- IECExIECEx is the global IEC certification scheme for equipment used in explosive atmospheres. Accepted in most jurisdictions outside the EU and US.
- IEC 60079IEC 60079 is the IEC's standard series for equipment used in explosive atmospheres. The technical foundation for both ATEX and IECEx certifications.