What is ATEX?
ATEX refers to two European directives for controlling explosive atmospheres: Directive 2014/34/EU covers equipment and protective systems intended for use in explosive atmospheres, while Directive 1999/92/EC covers workplace safety requirements. The name derives from the French Atmosphères Explosibles.
Any electrical or mechanical equipment used in classified hazardous areas within the EU must be ATEX certified by a Notified Body. The directive defines Essential Health and Safety Requirements (EHSRs) that products must meet.
What is the difference between ATEX and IECEx?
ATEX is a European Union regulatory requirement — mandatory for products sold in the EU. IECEx is an international voluntary certification scheme managed by the International Electrotechnical Commission (IEC), accepted in over 35 countries.
IECEx certificates can speed up national approvals in participating countries, but they do not replace ATEX within the EU. Many manufacturers obtain both. The technical standards (IEC 60079 series) are largely the same for both schemes.
What are Zone 0, Zone 1, and Zone 2?
These classify how often an explosive gas atmosphere is expected to be present:
- Zone 0 — Explosive atmosphere present continuously or for long periods (inside tanks, vessels)
- Zone 1 — Likely during normal operation (near vents, filling points, seals)
- Zone 2 — Not likely during normal operation, may occur briefly (general plant areas)
For dust, the equivalent zones are 20, 21, and 22. Equipment for Zone 0 requires the highest protection level (EPL Ga).
What do the letters in Ex markings mean?
An Ex marking like Ex db IIC T6 Gb breaks down as:
- Ex — Explosion protected
- db — Flameproof enclosure, protection level "b"
- IIC — Gas group (hydrogen/acetylene — most stringent)
- T6 — Temperature class (max 85°C surface temperature)
- Gb — Equipment Protection Level (suitable for Zone 1)
What is the difference between Ex d and Ex e?
Ex d (flameproof) contains an internal explosion inside a robust enclosure. The precision-machined gap (flamepath) cools escaping gases below ignition temperature. Used for switchgear, motors, and lighting in Zone 1.
Ex e (increased safety) prevents ignition from occurring by eliminating sparks, hot surfaces, and arcs through enhanced design margins on clearances, creepage, and temperature rise. Used for junction boxes, terminals, and luminaires.
What is intrinsic safety (Ex i)?
Intrinsic safety limits the electrical energy in a circuit so it cannot produce a spark or thermal effect capable of causing ignition — even under fault conditions. It is the only protection concept that is inherently safe rather than containing an explosion.
- Ex ia — Safe with two simultaneous faults (Zone 0 / EPL Ga)
- Ex ib — Safe with one fault (Zone 1 / EPL Gb)
- Ex ic — Safe in normal operation (Zone 2 / EPL Gc)
Widely used for instrumentation, sensors, and communication devices.
What gas groups exist and what do they mean?
Group I — Mining (methane). Group II — Surface industries: IIA (propane — least stringent), IIB (ethylene), IIC (hydrogen/acetylene — most stringent). Group III — Dust: IIIA (flyings), IIIB (non-conductive dust), IIIC (conductive dust).
Equipment certified for a higher group (e.g., IIC) can always be used in lower groups (IIA, IIB). This "hierarchy rule" simplifies equipment selection.
What are temperature classes T1 through T6?
| Class | Max surface temp | Example gases |
|---|---|---|
| T1 | 450°C | Methane, hydrogen |
| T2 | 300°C | Ethanol, butane |
| T3 | 200°C | Petrol/gasoline, diesel |
| T4 | 135°C | Acetaldehyde, diethyl ether |
| T5 | 100°C | — |
| T6 | 85°C | Carbon disulphide |
The equipment surface temperature must stay below the auto-ignition temperature of any gas present.
How long does ATEX certification take?
- 3–6 months — Straightforward products with established protection methods
- 6–12 months — Complex products or novel designs
- 12–18+ months — Design modifications needed after testing
The process includes: application, design review, prototype testing, test report (ExTR), quality system audit, and certificate issuance.
What is an EPL (Equipment Protection Level)?
EPL defines the level of protection reliability:
- Ga / Da / Ma — Very high protection (Zone 0 / 20 / mining energized)
- Gb / Db / Mb — High protection (Zone 1 / 21 / mining de-energized)
- Gc / Dc — Enhanced protection (Zone 2 / 22)
EPL bridges zone classification and equipment selection — it tells you which zones the equipment can be installed in.
Can I use Zone 1 equipment in Zone 2?
Yes. Equipment certified for a more hazardous zone can always be used in a less hazardous zone. Zone 0 → Zones 0, 1, 2. Zone 1 → Zones 1, 2. The reverse is never allowed.
What is a Notified Body?
A Notified Body is an organization designated by an EU member state to assess products against ATEX directive requirements. They perform EU Type Examination (Module B), issue certificates, and audit manufacturer quality systems.
Examples: DEKRA, PTB, BASEEFA (SGS), INERIS, LCIE, Eurofins, CSA Group. For IECEx, the equivalent is an Examination Body (ExCB).