- Category of equipment
Category type Presence or duration of
explosive atmosphere
Inflammable substances Level of protection faults to allow for Comparison with present practice
1 Continuous presence long periodsfrequent Gas, Vapors, Mist, Dust Very high Group II
Zone 0 (gas)
Zone 20 (dust)
2 Likely to occur Gas, Vapors, Mist, Dust High level Group II
Zone 1 (gas)
Zone 21 (dust)
3 Unlikely to occur present for short period Gas, Vapors, Mist. Dust Normal Group II
Zone 2 (gas)
Zone 22 (dust)