Decoder
The two markings on an Ex label
An Ex label usually carries two separate markings. The directive marking (the hexagon “Ex”, then the group, category and
G or D, e.g. II 2G) shows legal conformity under Directive 2014/34/EU. The standard marking (starting with “Ex” and
ending with the EPL, e.g. Ex db IIB T4 Gb) gives the technical detail. An “X” after the certificate number means specific
conditions of use; a “U” means an Ex component that cannot be used on its own.
Zones, categories and EPLs
The ATEX directives use equipment categories; IEC standards express the same idea as equipment protection levels (EPL). Labels usually carry both.
| Zone | Category | EPL |
|---|---|---|
| Zone 0 | 1G | Ga |
| Zone 1 | 2 or 1G | Gb or Ga |
| Zone 2 | 3, 2 or 1G | Gc, Gb or Ga |
| Zone 20 | 1D | Da |
| Zone 21 | 2 or 1D | Db or Da |
| Zone 22 | 3, 2 or 1D | Dc, Db or Da |
Types of protection
| Code | Type of protection | Standard | Level → EPL |
|---|---|---|---|
d | Flameproof enclosure | IEC 60079-1 | db → Gb, dc → Gc |
e | Increased safety | IEC 60079-7 | eb → Gb, ec → Gc |
i | Intrinsic safety | IEC 60079-11 | ia → Ga/Da, ib → Gb/Db, ic → Gc/Dc |
p | Pressurization | IEC 60079-2 | pxb, pyb → Gb; pzc → Gc |
m | Encapsulation | IEC 60079-18 | ma, mb, mc |
o | Liquid immersion | IEC 60079-6 | ob → Gb, oc → Gc |
q | Powder filling | IEC 60079-5 | Gb |
t | Dust protection by enclosure | IEC 60079-31 | ta → Da, tb → Db, tc → Dc |
n | Type n (former nA is now ec) | IEC 60079-15 | nC, nR → Gc |
op | Optical radiation | IEC 60079-28 | op is, op pr, op sh |
s | Special protection | IEC 60079-33 | sa, sb, sc |
h | Non-electrical equipment | ISO 80079-36/-37 | EPL on the label |
One item may combine several types: “db eb”, for example, means a flameproof housing with an increased-safety terminal box. A marking in square brackets (e.g. [Ex ia Ga]) describes associated apparatus installed outside the hazardous area.
Groups and temperature classes
The group tells you which substances the equipment is suitable for; the temperature class gives its maximum surface temperature. For dust, the maximum surface temperature is marked directly in °C.
| Class | Maximum surface temperature |
|---|---|
T1 | 450 °C |
T2 | 300 °C |
T3 | 200 °C |
T4 | 135 °C |
T5 | 100 °C |
T6 | 85 °C |
- IIA: IIA only (propane, acetone, toluene)
- IIB: IIB and IIA (ethylene, ethanol, diethyl ether)
- IIC: all gases (hydrogen, acetylene, carbon disulphide)
- IIIA / IIIB / IIIC: flyings / non-conductive dust / conductive dust; a higher group covers the lower ones
What the decoder does not do
It explains what the marking says. It does not verify that the label is genuine, that the certificate is valid, that the specific conditions of use are met on site, or the physical condition of the equipment. Whether the zone and the substance have been determined correctly is a separate question. For sites in Turkey we check all of this in an Ex equipment compliance review.
Basis
Marking under Directive 2014/34/EU (EU ATEX guidelines §146–149), the IEC 60079-0 standard marking, the IEC 60079 standards for each type of protection, ISO 80079-36/-37, and IEC 60079-14 for equipment selection. The relationship between zones and categories is set in Annex II of Directive 1999/92/EC.
This tool is for information. For equipment selection, the certificate, the instructions and the current text of the standards apply.
Frequently asked questions
Can “Ex-proof” equipment be used in any zone?
No. The category or EPL must suit the zone, and the group and temperature class must suit the substance. Select the zone and the substance group in the decoder to check.
The label has no EPL. What does that mean?
Older labels may not show an EPL. The decoder then derives it from the level of the type of protection (e.g. db → Gb) and says so. Check the certificate for certainty.
Why is temperature checked separately for dust?
For dust, the maximum surface temperature must not exceed two thirds of the dust cloud ignition temperature or the 5 mm layer ignition temperature minus 75 K (IEC 60079-14). Thicker layers need a separate assessment.