What is IEC 60079?
IEC 60079 is the international standard for electrical equipment in explosive atmospheres. The standard sets out safety principles, types of protection and installation requirements for equipment used in Zones with flammable gases, vapours or dust.
In OT systems, IEC 60079 is crucial for installations in refineries, chemical plants, silos, hydrogen filling stations and other environments where explosive atmospheres can occur.
🧠 Purpose of IEC 60079
- Preventing ignition – Equipment must not act as an ignition source
- Classifying zones – Categorising areas based on explosion risk
- Safe installation and maintenance – Requirements for design, inspection and training
- Marking of explosion-proof equipment – Through codes and labelling
- Harmonisation with the ATEX directive – Supports CE marking in the EU
🔥 Zone classification (ATEX/IEC explosive areas)
| Zone | Gas/vapour | Dust | Description |
|---|---|---|---|
| Zone 0 | Gases permanently present | – | Continuous explosive atmosphere |
| Zone 1 | Gases regularly present | – | Risk of explosive atmosphere during operation |
| Zone 2 | Gases occasionally present | – | Rare and short-lived |
| Zone 20 | – | Dust permanently present | Always present (e.g. inside silos) |
| Zone 21 | – | Dust regularly | Frequent during normal operation |
| Zone 22 | – | Dust occasionally | Only during faults or briefly |
🛡️ Types of protection in line with IEC 60079
| Code | Method | Use |
|---|---|---|
| Ex d | Flameproof enclosure | Enclosures that can contain an internal explosion |
| Ex e | Increased safety | No sparks or hot surfaces |
| Ex i | Intrinsically safe | Limits energy so that ignition is impossible |
| Ex n | Limited risk (zone 2) | For use in low-risk areas |
| Ex t | Protection against dust ignition | For zones 20–22 (dust explosions) |
| Ex p | Pressurised enclosure | Overpressure prevents gas ingress |
The right choice depends on zone, equipment type, gas group and temperature class.
✅ Marking of explosion-proof equipment
A typical marking on a device in line with IEC 60079 looks like this:
Ex II 2 G Ex d IIC T4 Gb
| Segment | Meaning |
|---|---|
| Ex | Suitable for explosive atmospheres |
| II | Group II: for industrial use (not mining) |
| 2 | Equipment category (1 = very high, 2 = high, 3 = normal) |
| G | Gas environment (D = dust) |
| Ex d | Type of protection (here: flameproof enclosure) |
| IIC | Gas group (A = methane, C = acetylene/hydrogen) |
| T4 | Max. surface temperature (T1–T6) |
| Gb | Equipment Protection Level (Ga, Gb, Gc: very high to normal) |
🔁 Relationship with other standards and frameworks
| Standard / Directive | Relation |
|---|---|
| ATEX | IEC 60079 is the technical basis for ATEX certification |
| NEN-EN-IEC 60079 | European version of the IEC standard |
| IEC 61439 | Construction of switchgear cabinets for Ex zones requires Ex variants |
| IEC 60204-1 | General electrical safety – Ex supplement required |
| Machinery Directive | For explosion-proof machinery, IEC 60079 applies |
⚠️ Practical pitfalls
- Use of non-certified components in Ex zones
- Incorrect cable glands that fail to provide proper sealing
- No documentation of zone classification or maintenance status
- Errors in temperature classification or gas group selection
- Insufficiently trained personnel for Ex inspection or installation
📌 In summary
IEC 60079 is the definitive standard for explosion-proof electrical equipment. In OT environments where explosive atmospheres can occur, compliance with this standard is crucial for safety, liability and CE conformity.