Reading ATEX markings — what does the Ex marking mean?
An Ex equipment marking tells you exactly where and in which atmosphere it can be used safely. Below I break down a typical gas and dust marking piece by piece — so you can tell at a glance whether a piece of equipment belongs in its zone.
How to read it — gas marking
Take a typical gas marking and split it into pieces:
ExExplosion-protected design.IISurface industry (I = mining).2GEquipment Category 2, for gas (G).Ex dbFlameproof enclosure (d), protection level "b".IICGas group (the strictest: hydrogen, acetylene).T4Max. 135 °C surface temperature.GbEPL — high protection level (Zone 1).How to read it — dust marking
The logic of a dust marking is similar, but with its own groups and the IP rating:
Ex tDust protection by enclosure.IIICConductive dust.T85°CMax. surface temperature (in °C for dust).DbEPL for dust (Zone 21).IP6XFull ingress protection against dust.Ex tD A21 IP6X — here A21 indicated Zone 21.
Temperature classes (T1–T6) — gas
The T-class is the maximum permitted surface temperature of the equipment. It must always be lower than the ignition temperature of the gas present:
| T-class | Max. surface temperature |
|---|---|
T1 | 450 °C |
T2 | 300 °C |
T3 | 200 °C |
T4 | 135 °C |
T5 | 100 °C |
T6 | 85 °C |
EPL protection levels and zones
EPL (Equipment Protection Level) links the equipment to the zone. Read this alongside the zone classification:
| EPL | Atmosphere | Permitted zone |
|---|---|---|
Ga | Gas | Zone 0 (and 1, 2) |
Gb | Gas | Zone 1 (and 2) |
Gc | Gas | Zone 2 |
Da | Dust | Zone 20 (and 21, 22) |
Db | Dust | Zone 21 (and 22) |
Dc | Dust | Zone 22 |
Common Ex protection types
The letter in the marking tells you on which principle the equipment is protected against ignition:
Flameproof enclosure — the enclosure contains an internal explosion.
Increased safety — no ignition source in normal operation.
Intrinsic safety — energy limited so it cannot ignite (ia/ib/ic).
Pressurised — clean gas/air keeps the explosive atmosphere out.
Encapsulation — parts sealed inside a solid compound.
Dust protection by enclosure (for dusty areas).
Used for Zone 2; non-igniting in normal operation (formerly "n" type).
Not sure whether the equipment belongs in its zone?
During an inspection I check the markings, the zone classification and the Ex compliance on site. Book a free 30–60 minute online needs assessment.