The Classification System that found in Article 506:
- divides locations having dusts, fibers or flyings into Zones (20, 21 & 22).
- Zone 20: a location where ignitible concentrations are present continuously or for long periods of time under normal operating conditions.
- Zone 21: a location where ignitible concentrations are likely to exist occasionally under normal operating conditions.
- Zone 22: a location where ignitible concentrations are not likely to exist under normal operating conditions.
- NEC - National Electrical Code of USA
- Article 506 covers the requirements for the zone classification system as an alternative to the division classification system covered in Article 500, Article 502 (Class II Locations) and Article 503 (Class III Locations) for electrical and electronic equipment and wiring for all voltages in Zone 20, Zone 21 and Zone 22 hazardous (classified) locations where fire and explosion hazards may exist due to combustible dusts, or ignitible fibers or flyings. Combustible metallic dusts are not covered by the requirements of this article.
GCS Safety Team