How to Read Ex Markings on Equipment

Every certified Ex device carries a marking that encodes its protection type, gas/dust group, temperature class, and equipment protection level. Understanding these markings is essential for selecting, installing, and inspecting equipment.

ATEX Marking Structure

ATEX equipment carries a structured marking per Directive 2014/34/EU:


CE 0539  ⟨Ex⟩  II 2G  Ex db IIC T4 Gb
│   │     │     │  │    │  │  │   │  │
│   │     │     │  │    │  │  │   │  └─ EPL (Gb = High, Zone 1)
│   │     │     │  │    │  │  │   └──── Temperature class (T4 = max 135°C)
│   │     │     │  │    │  │  └──────── Gas group (IIC = hydrogen/acetylene)
│   │     │     │  │    │  └─────────── Protection type (db = flameproof, EPL b)
│   │     │     │  │    └────────────── Ex symbol (explosion protected)
│   │     │     │  └─────────────────── Category (2G = Category 2, Gas)
│   │     │     └────────────────────── Equipment Group (II = surface industries)
│   │     └──────────────────────────── ATEX hexagonal "Ex" symbol
│   └────────────────────────────────── Notified Body number
└────────────────────────────────────── CE mark

ATEX Equipment Groups

Group	Application
I	Mining (firedamp)
II	Surface industries — gas/vapour
III	Surface industries — dust

ATEX Categories

Marking	Category	EPL	Zonas
1G	Cat 1 Gas	Ga	0, 1, 2
2G	Cat 2 Gas	Gb	1, 2
3G	Cat 3 Gas	Gc	2
1D	Cat 1 Dust	Da	20, 21, 22
2D	Cat 2 Dust	Db	21, 22
3D	Cat 3 Dust	Dc	22

IECEx Marking Structure

IECEx markings follow IEC 60079-0:


Ex db IIC T4 Gb
│  │  │   │  │
│  │  │   │  └─ EPL
│  │  │   └──── Temperature class
│  │  └──────── Gas group
│  └─────────── Protection type with level suffix
└────────────── Ex symbol

IECEx markings do not include the CE mark, group number, or category. Instead, the IECEx certificate number provides traceability:


IECEx BAS 12.0034X
│     │   │
│     │   └─ Certificate number + revision (X = specific conditions)
│     └───── ExCB code (BAS = Baseefa, UK)
└─────────── IECEx scheme identifier

Reading the Protection Type

The protection type uses the two-letter "Ex" prefix followed by the method letter and level suffix:

Marking	Method	Level	Meaning
Ex ia	Intrinsic safety	a	Zone 0 capable
Ex ib	Intrinsic safety	b	Zone 1 capable
Ex ic	Intrinsic safety	c	Zone 2 only
Ex db	Flameproof	b	Zone 1 capable
Ex dc	Flameproof	c	Zone 2 only
Ex eb	Increased safety	b	Zone 1 capable
Ex ec	Increased safety	c	Zone 2 only
Ex ma	Encapsulation	a	Zone 0 capable
Ex mb	Encapsulation	b	Zone 1 capable
Ex mc	Encapsulation	c	Zone 2 only
Ex px	Pressurized	x	Zone 1 → non-haz
Ex py	Pressurized	y	Zone 1 → Zone 2
Ex pz	Pressurized	z	Zone 2 → non-haz
Ex nA	Non-sparking	—	Zone 2 only
Ex nC	Closed/sealed contacts	—	Zone 2 only
Ex nR	Restricted breathing	—	Zone 2 only
Ex ta	Dust enclosure	a	Zone 20 capable
Ex tb	Dust enclosure	b	Zone 21 capable
Ex tc	Dust enclosure	c	Zone 22 only
Ex o	Oil immersion	—	Zone 1 capable
Ex q	Powder filling	—	Zone 1 capable

Combined Markings

Equipment with multiple protection methods:


Ex db eb IIC T4 Gb

Main body: flameproof (db). Terminal compartment: increased safety (eb).


Ex db [ib Ga] IIC T4 Gb

Flameproof enclosure (Gb) containing intrinsically safe circuits (Ga). The brackets indicate the IS circuits inside.


Ex db IIC T6...T4 Gb

Temperature class varies with ambient temperature. T6 at standard ambient, T4 at elevated ambient.

Dual Gas and Dust Marking

Equipment certified for both gas and dust:


II 2G  Ex db IIC T4 Gb
II 2D  Ex tb IIIC T125°C Db

Both lines appear on the nameplate. The equipment can be used in gas Zone 1 or dust Zone 21.

Reading Real-World Examples

Example 1: Junction Box


CE 0539 ⟨Ex⟩ II 2G Ex eb IIC T5 Gb

ATEX Group II, Category 2G (Zone 1 gas)
Increased safety (Ex eb)
All gas groups (IIC)
T5 (max 100°C surface)
EPL Gb

Example 2: LED Floodlight


CE 0539 ⟨Ex⟩ II 2G Ex db eb IIC T4 Gb
                    II 2D Ex tb IIIC T135°C Db

Dual rated: gas (Zone 1) and dust (Zone 21)
Flameproof body with increased safety terminal box
All gas groups (IIC), all dust groups (IIIC)
Gas: T4 (135°C max), Dust: 135°C max

Example 3: ATEX Certified iPhone Case (Xshielder)


⟨Ex⟩ II 2G Ex db IIC T4 Gb
     II 2D Ex tb IIIC T135°C Db

Zone 1 gas + Zone 21 dust
Flameproof + dust-protected enclosure
Covers all gas groups and dust groups
IP65 rated, wireless charging compatible

Example 4: Intrinsically Safe Transmitter


CE 0539 ⟨Ex⟩ II 1G Ex ia IIC T4 Ga

Category 1G — suitable for Zone 0
Intrinsically safe (highest level, Ex ia)
All gas groups (IIC)
T4 (135°C max)
EPL Ga (very high protection)

Example 5: Zone 2 Motor


CE 0539 ⟨Ex⟩ II 3G Ex nA IIB T3 Gc

Category 3G — Zone 2 only
Non-sparking (Ex nA)
Gas groups IIA and IIB only (not IIC)
T3 (200°C max)
EPL Gc

Additional Markings on the Nameplate

Beyond the Ex marking, equipment labels include:

Marking	Meaning
Ta or Tamb	Ambient temperature range (e.g., −40°C to +60°C)
IP66 / IP68	Ingress protection rating
X	Special conditions of use (see certificate)
U	Component certificate (not stand-alone)
Certificate no.	Reference to the full test certificate
Serial number	Unique device identifier for traceability
Year of manufacture	Required for audit trail

The "X" suffix is important — it means there are special conditions documented in the certificate that must be observed during installation and use. Always retrieve and read the certificate when you see "X".

NEC/CEC Markings (North America)

North American marking follows a different format:


Class I, Division 1, Groups B, C, D, T4

Or in the Zone system:


Class I, Zone 1, AEx db IIC T4 Gb

The "A" prefix before "Ex" indicates the equipment is certified to North American standards (NEC/CEC) using the Zone system.

Protection Methods — detailed explanation of each method
Gas Groups — what IIA/IIB/IIC means
Temperature Classes — what T1–T6 means
EPL — what Ga/Gb/Gc means
Normas — which standard governs each marking element
Certification — how certificates and markings are issued