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ATEX / Explosive Atmospheres

ATEX

ATEX / Explosive Atmospheres

Regulatory and technical framework for equipment intended for areas where explosive atmospheres can form — gases, vapours, mists, combustible dusts. Everything you need to read an Ex marking, select the right equipment and classify zones.

Regulatory framework

Directive 2014/34/EU

Equipment and protective systems

CE Ex marking, certification by notified body, technical file, EU declaration of conformity. Applies to manufacturers.

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Directive 99/92/EC

Worker safety at workplaces

Explosion risk assessment, zone classification, explosion protection document. Applies to operators.

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IECEx

IEC international scheme

Worldwide equivalent of ATEX — mutual recognition of test labs (ExTL), CoC certificates, quality management (ExCB). Essential outside the EU.

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Zone classification

The frequency and duration of an explosive atmosphere determines the zone. Classification follows IEC 60079-10-1 (gas) and IEC 60079-10-2 (dust).

Type Zone Presence of atmosphere Min. category EPL
Gas / vapour 0 Continuously, long periods or frequently 1G Ga
1 Likely in normal operation 2G Gb
2 Unlikely / short duration 3G Gc
Combustible dust 20 Dust cloud continuously, long periods or frequently 1D Da
21 Likely in normal operation 2D Db
22 Unlikely / short duration 3D Dc

Anatomy of an Ex marking

The compact Ex marking combines ATEX (European frame) and IEC 60079 (technical). Every part is mandatory and codified.

II 2 G Ex db IIB T4 Gb
IIGroup — surface (non-mining)
2Category 2 — zone 1 (high protection)
GGas atmosphere
ExIEC 60079 compliant
dFlameproof mode
bProtection level (EPL = b)
IIBGas group — ethylene etc.
T4T_max surface ≤ 135 °C
GbEPL Gb — zone 1
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Protection modes (IEC 60079)

Each mode applies a distinct physical principle to prevent ignition: containment, prevention, energy limitation, exclusion.

Ex d

Flameproof enclosure

IEC 60079-1 Zones 1, 2

Enclosure contains internal explosion without propagating it — cools escaping gases.

Ex e

Increased safety

IEC 60079-7 Zones 1, 2

Constructive measures ensure no arcs or hot spots can occur — oversized terminals, conductors.

Ex ia

Intrinsic safety level a

IEC 60079-11 Zones 0, 1, 2

Energy limited below ignition threshold even with 2 simultaneous faults. Only mode allowed in zone 0.

Ex ib

Intrinsic safety level b

IEC 60079-11 Zones 1, 2

Energy limited with one fault. Sufficient for zone 1.

Ex p

Pressurized enclosure

IEC 60079-2 Zones 1, 2

Positive pressure of air or inert gas inside enclosure — prevents explosive atmosphere from entering.

Ex n

Type n

IEC 60079-15 Zones 2

Variants (nA, nC, nR) for zone 2 only — lower cost, less strict assumptions.

Ex m

Encapsulation

IEC 60079-18 Zones 0, 1, 2

Components embedded in resin — ignition sources isolated from atmosphere.

Ex t

Dust ignition protection

IEC 60079-31 Zones 20, 21, 22

Dust-tight (IP6X) + limited surface temperature. Variants ta / tb / tc.

Temperature classes

The T class guarantees that the hottest exposed surface of the equipment stays below the auto-ignition temperature of the gas present. Pick according to the worst-case gas of the installation.

Class Max surface T Example gases / vapours
T1 450 °C Methane, ammonia, carbon monoxide
T2 300 °C Ethane, acetone, butane
T3 200 °C Petrol, kerosene, fuel oil, hexane
T4 135 °C Acetaldehyde, diethyl ether
T5 100 °C Carbon disulfide
T6 85 °C Carbon disulfide (max safety)

ATEX tools

Ex marking decoder

Enter a full marking (e.g. II 2 G Ex db IIB T4 Gb) and get a line-by-line explanation with automatic category / EPL coherence check.

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ATEX & IECEx standards