ATEX is the common name for the EU regulatory framework governing equipment and protective systems intended for use in potentially explosive atmospheres. The name derives from the French ATmosphères EXplosibles. The framework currently consists of two directives:
- ATEX Equipment Directive (2014/34/EU) — applies to manufacturers placing equipment, protective systems, and components for use in explosive atmospheres on the EU market
- ATEX Workplace Directive (1999/92/EC) — applies to employers operating workplaces where explosive atmospheres may occur (classified zone requirements, worker training)
For hardware manufacturers, the relevant directive is 2014/34/EU.
When ATEX Applies
ATEX applies to any equipment intended for use in an atmosphere that may be explosive due to:
- Flammable gases or vapours mixed with air (e.g., hydrogen, methane, propane in chemical plants, refineries, gas distribution)
- Combustible dusts suspended in air (e.g., grain silos, flour mills, woodworking, pharmaceutical manufacturing, coal handling)
- Combustible mists (e.g., hydraulic systems with flammable hydraulic fluid)
ATEX does NOT apply to:
- Medical devices intended for use in a medical environment
- Equipment for domestic and non-commercial use where an explosive atmosphere can arise only rarely, solely from accidental fuel-gas leakage
- Personal protective equipment covered by PPE legislation
- Means of transport (vehicles intended for use in a potentially explosive atmosphere remain in scope)
- Seagoing vessels and mobile offshore units, including equipment on board
Equipment Groups and Categories
ATEX divides equipment into two groups based on intended environment:
Group I — Mining (underground mines with firedamp/coal dust risk):
| Category | Protection level | User location |
|---|---|---|
| M1 | Very high (continues to function in explosive atmosphere) | Present even when explosive atmosphere arises |
| M2 | High (de-energised when explosive atmosphere arises) | Present but evacuates when explosive atmosphere arises |
Group II — All other explosive atmospheres (surface industry):
| Category | Zone classification | Example environment |
|---|---|---|
| 1G, 1D (Cat. 1) | Zone 0 (gas) or Zone 20 (dust) — highest risk; also usable in Zones 1/21 and 2/22 | Continuously or frequently explosive atmosphere |
| 2G, 2D (Cat. 2) | Zone 1/21 | Occasionally explosive atmosphere |
| 3G, 3D (Cat. 3) | Zone 2/22 | Rarely explosive atmosphere (under normal operation only) |
The “G” suffix indicates protection against gas/vapour atmospheres, “D” against dust atmospheres. Many products need certification for both.
Conformity Assessment for ATEX
Unlike EMC or RED, ATEX requires a Notified Body for all Category M1 and Category 1 equipment and for electrical equipment and internal combustion engines of Category M2 and 2; for other M2 and Category 2 equipment the manufacturer applies internal production control and lodges the technical documentation with a Notified Body:
| Equipment | Conformity Assessment Route |
|---|---|
| Group I, Cat. M1 | Module B (EU-type examination) + Module D or Module F; or Module G |
| Group I, Cat. M2 | Electrical equipment and internal combustion engines: Module B + Module C1 or Module E; other equipment: Module A + technical documentation lodged with a Notified Body; or Module G |
| Group II, Cat. 1 | Module B + Module D or Module F; or Module G |
| Group II, Cat. 2 | Electrical equipment and internal combustion engines: Module B + Module C1 or Module E; other equipment: Module A + technical documentation lodged with a Notified Body; or Module G |
| Group II, Cat. 3 | Module A (self-declaration) — no NB required |
The EU Type Examination Certificate defines the certified equipment type, the specific explosive atmosphere it is designed for, and any special conditions for safe use.
Key ATEX Standards (EN 60079 Series)
The EN 60079 series provides harmonised standards for different protection concepts:
| Protection Concept | Standard | Description |
|---|---|---|
| Ex d (Flameproof enclosure) | EN 60079-1 | Enclosure withstands internal explosion and prevents ignition of external atmosphere |
| Ex e (Increased safety) | EN 60079-7 | Additional measures to prevent sparks and excess temperatures |
| Ex i (Intrinsic safety) | EN 60079-11 | Circuit energy limited so it cannot ignite explosive atmosphere — most used for instrumentation/sensors |
| Ex nC / nR (type of protection “n”) | EN IEC 60079-15 | Sealed or non-incendive devices (nC) and restricted-breathing enclosures (nR) — Zone 2 only; non-sparking equipment is covered as increased safety “ec” in EN IEC 60079-7 |
| Ex p (Pressurised enclosure) | EN 60079-2 | Enclosure pressurised with protective gas to prevent explosive atmosphere from entering |
| Ex tb/tc (Dust enclosure) | EN 60079-31 | Protection by enclosure for dust atmospheres |
For embedded electronics in ATEX products, Ex i (intrinsic safety) is the most common protection concept — the circuit is designed so that under both normal and fault conditions, the electrical energy cannot cause ignition.
Practical Implications for Hardware Design
Designing for ATEX compliance imposes significant hardware constraints:
- Power dissipation limits (to prevent hot surfaces exceeding temperature class)
- Circuit energy budgets (for Ex i — maximum voltage, current, inductance, capacitance)
- Enclosure ingress protection and mechanical strength
- Material restrictions (risk of electrostatic discharge from non-conductive surfaces)
- Component qualification (capacitors, inductors, zener barriers must be ATEX-qualified)
ATEX projects require early engagement with the Notified Body to agree the protection concept and design intent — the NB must review and approve the design before the test phase, not only at the end.
Official References
- Directive 2014/34/EU (ATEX) — Full text — EUR-Lex, Official Journal of the European Union