The matching table
| Zone | Category required | What it means |
|---|---|---|
| 0 (gas) / 20 (dust) | 1G / 1D | Very high protection: will not ignite even with two independent faults |
| 1 (gas) / 21 (dust) | 2G / 2D | High protection: will not ignite with frequently occurring faults |
| 2 (gas) / 22 (dust) | 3G / 3D | Normal protection: will not ignite in normal operation |
The rule works one way only: a higher category may be used downwards — category 1 equipment in zone 2 is no problem. The reverse is never accepted.
The group has to match too
Category alone is not enough. The equipment group must also fit: Group I for firedamp atmospheres in mines, Group II for surface installations, and Group III for dust atmospheres. Equipment selected for a surface plant is not automatically suitable underground, nor mining equipment above ground.
Where inspections most often catch it
The classification is done, the drawing is clean, the document is written — and the luminaire on site, the cable transit, the torch, the portable pump or the camera is not of the right category for the zone. The finding always reads the same way: the document is correct, the site does not follow it.
What about non-Ex equipment
Everything entering the zone counts as equipment: hand tools, measuring devices, phones, welding sets, forklifts. Either the zone-suitable version is used, or entry happens under a permit with atmosphere measurement. “It will only take a minute” is the most expensive sentence on site.
How this stands in Optifora
The module holds 7 equipment categories and 4 equipment groups alongside the zone records; for every item assigned to a zone, a category mismatch appears as its own finding.