ATEX / IECEx Hazardous-Area Zoning and Equipment Marking
Compliance reference compiled by cBallast. 4-page PDF; the full content is on this page.
Compiled by
cBallast
Subject
Hazardous-area equipment
Document type
Compliance reference
Reference
IEC 60079-0 : 2017 / ATEX 2014/34/EU
Issued
2026-07-14
Pages
4
Format
Web page and PDF
Reference for hazardous-area zoning and equipment marking under the ATEX Directive 2014/34/EU (Europe) and the IECEx scheme (international). Decodes the zone designations (Zone 0, 1, 2 for gas; Zone 20, 21, 22 for dust), gas groups (IIA, IIB, IIC + IIIA-C), temperature classes (T1-T6), and the two-part equipment marking: category code (II 1G, II 2G, II 3G) plus protection code (Ex db IIB T4 Gb etc.).
Two schemes, one technical intent
ATEX (Atmosphères Explosibles) is the EU legal framework covering both equipment (Directive 2014/34/EU) and workplace safety (Directive 1999/92/EC). IECEx is the parallel global scheme operated by the IEC. The technical rules are identical because both reference the same IEC 60079 series of standards; ATEX adds EU-specific certification and market-surveillance requirements. Equipment certified under IECEx is generally accepted for use in Europe if it also carries a manufacturer's ATEX declaration of conformity.
Hazardous area zoning
Zone
Substance
Presence of hazard
Example
0
Gas / vapour
Continuous or long periods
Interior of a fuel-oil tank vapour space
1
Gas / vapour
Likely in normal operation
Immediate vicinity of a fuel-oil pump seal
2
Gas / vapour
Not likely in normal operation, short duration if it occurs
Ventilated pump room, remote from source
20
Combustible dust
Continuous or long periods
Interior of a flour mill bin
21
Combustible dust
Likely in normal operation
Dust extraction connection at a hopper
22
Combustible dust
Not likely in normal operation
Room adjacent to a dust process, well-cleaned
Equipment category (ATEX)
Category
Zone rating
Group I (mining)
Group II (surface)
M1 / 1
Highest protection
Mining, remain energised in gas
Zone 0 / 20 gas / dust
M2 / 2
High
Mining, de-energise on gas detection
Zone 1 / 21 gas / dust
3
Normal
—
Zone 2 / 22 gas / dust
Gas group (explosion group)
Group
Representative gas
MESG (mm)
MIC ratio
IIA
Propane, kerosene, methane (surface)
> 0.9
> 0.8
IIB
Ethylene, ethyl ether
0.5-0.9
0.45-0.8
IIC
Hydrogen, acetylene
< 0.5
< 0.45
IIIA
Combustible flyings
—
—
IIIB
Non-conductive dust
—
—
IIIC
Conductive dust (metal)
—
—
Temperature class
T class
Max surface temp
Suitable for gases with AIT above
T1
450 °C
> 450 °C (methane, hydrogen)
T2
300 °C
> 300 °C (propane, butane, acetylene)
T3
200 °C
> 200 °C (heptane, cyclohexane, diesel oil)
T4
135 °C
> 135 °C (acetaldehyde, ethyl ether)
T5
100 °C
> 100 °C
T6
85 °C
> 85 °C (carbon disulphide)
Protection technique (Ex code)
Ex code
Protection method
Typical use
Ex d
Flameproof enclosure
Motor terminal box, lamps, switchgear
Ex e
Increased safety
Terminal boxes, junction boxes, luminaires
Ex ia / ib / ic
Intrinsic safety (energy-limited)
Instrumentation, sensors, low-power signalling
Ex m
Encapsulation (resin-potted)
Electronic assemblies, small devices
Ex n / Ex nA / Ex nR
Non-sparking (Zone 2 only)
Squirrel-cage motors, terminal boxes for Zone 2
Ex p / Ex pxb / Ex pyb / Ex pzc
Pressurisation (purged enclosure)
Analyser cabinets, PLC panels in Zone 1/2
Ex q
Powder filling (sand-filled)
Capacitors, high-voltage components
Ex t
Dust protection by enclosure
Dust-atmosphere equipment
Reading a complete marking
Example: II 2G Ex db IIB T4 Gb. II = equipment group II (surface, not mining). 2G = category 2, gas atmosphere (suitable for Zone 1). Ex db = flameproof-enclosure protection at EPL level b. IIB = gas group IIB (safe for ethylene, ethyl ether, propane, etc.; not safe for hydrogen). T4 = surface temperature ≤ 135 °C. Gb = equipment protection level Gb (high protection, gas atmosphere).
Presence of the explosive gas atmosphere: continuous or long-period (Zone 0), likely in normal operation (Zone 1), unlikely and short-lived (Zone 2). Dusts mirror this as Zones 20/21/22.
Which equipment category suits Zone 1?
ATEX Category 2G (or 1G) — the marking line, e.g. II 2G Ex db IIC T4 Gb, must show it; Category 3G equipment is limited to Zone 2.
What does the T-class in an Ex marking mean?
Maximum surface temperature: T4 = 135 °C — it must stay below the ignition temperature of the gas present.
Are ATEX and IECEx the same?
Same technical basis (IEC 60079), different legal frames: ATEX is the EU directive marking, IECEx an international certification scheme; many products carry both.