What Do Zones 0, 1, 2 and 20, 21, 22 Mean?
Zone classification is the basis for selecting equipment according to how frequently and for how long an explosive atmosphere may be present. Zones 0, 1 and 2 are used for gas atmospheres, while Zones 20, 21 and 22 are used for combustible dust atmospheres.
Why is Zone classification important?
A Zone indicates the likelihood and duration of an explosive atmosphere. The required equipment protection level is selected accordingly; the word “explosion-proof” on its own is not enough to establish suitability.
Gas atmospheres: Zone 0, Zone 1 and Zone 2
Zone 0 covers areas where an explosive gas atmosphere is present continuously, for long periods or frequently. Zone 1 covers areas where it is likely to occur occasionally in normal operation. Zone 2 covers areas where it is not likely in normal operation and, if it occurs, exists only for a short time.
Dust atmospheres: Zone 20, Zone 21 and Zone 22
A similar approach is used for combustible dusts with Zones 20, 21 and 22. Equipment selection must consider not only the Zone but also the dust group and the permitted maximum surface temperature.
What should be checked when selecting equipment?
Equipment category or EPL, gas/dust group, temperature class, protection concept, ambient-temperature range and IP rating must match the project conditions. The certificate and product marking should be verified for the ordered configuration.
Site documentation is the basis
Final selection should follow the facility hazardous-area classification document and the relevant project specification. Where conditions are unclear, the application should be reviewed by competent engineering personnel.