IEC 60079-0 Equipment — General requirements
The foundation. Defines Ex equipment marking, temperature classes (T1-T6), gas groups (IIA/IIB/IIC), dust groups (IIIA/IIIB/IIIC), Equipment Protection Levels (EPL Ga/Gb/Gc, Da/Db/Dc).
IEC 60079
Explosive Atmospheres (ATEX / IECEx)
IEC 60079 is the international standards series for equipment intended for use in explosive atmospheres (gas and dust). Foundation of the IECEx certification scheme and the technical basis for the European ATEX Directive 2014/34/EU.
Dokumentstruktur
IEC 60079-10-1 Classification of areas — Explosive gas atmospheres
How to classify a plant area into Zone 0 (continuous), Zone 1 (likely in normal ops), Zone 2 (unlikely, brief). Output is the area classification document.
IEC 60079-10-2 Classification of areas — Explosive dust atmospheres
Same logic for dust : Zone 20, 21, 22. Common in agroindustry, pharma, metal processing.
IEC 60079-11 Equipment protection by intrinsic safety 'i'
The flagship protection method for instrumentation. Energy and stored capacity strictly limited so that no spark or hot surface can ignite. EX ia (Zone 0), EX ib (Zone 1), EX ic (Zone 2).
IEC 60079-1 Equipment protection by flameproof enclosure 'd'
Rugged metallic enclosure that contains an internal explosion without propagating to the outside. Used for motors, switchgear, lights. Heavy and expensive but extremely robust.
IEC 60079-14 Electrical installations design, selection and erection
How to install Ex equipment correctly. Cable glands, sealing, equipotential bonding, intrinsically safe loop documentation. The 'site engineer's manual'.
IEC 60079-17 Electrical installations inspection and maintenance
Periodic inspection regime for Ex installations. Visual, close, detailed inspections at defined intervals.
IEC 60079-25 Intrinsically safe electrical systems
How to design an intrinsically safe LOOP (not just individual devices). Includes barrier selection, system documentation.
Schlüsselbegriffe
- Zone classification (gas)
- Zone 0 : explosive atmosphere present continuously or for long periods (inside fuel tank). Zone 1 : likely in normal operation (around tank vents). Zone 2 : not likely in normal operation, brief if occurs (around bolted flanges).
- Zone classification (dust)
- Zone 20 / 21 / 22 — same logic for combustible dust (flour, coal, metal powders, sugar). Often forgotten but a major cause of historical industrial disasters (Imperial Sugar 2008).
- Equipment Protection Level
(EPL) - Ga / Gb / Gc for gas, Da / Db / Dc for dust. Indicates the level of protection required for each zone. EPL Ga (very high) is required in Zone 0. EPL Gc (enhanced) is acceptable in Zone 2.
- Temperature Class
(T-class) - Maximum surface temperature an Ex device can reach. T1 = 450°C, T2 = 300°C, T3 = 200°C, T4 = 135°C, T5 = 100°C, T6 = 85°C. Must be lower than the auto-ignition temperature of the surrounding gas.
- Gas Group
- Classification of gas hazards by ignition energy. IIA (propane, easiest), IIB (ethylene, methane intermediate), IIC (hydrogen, acetylene, hardest). An Ex device certified IIC works in IIA/IIB too, but not vice versa.
- Intrinsic Safety
(Ex i) - Protection by limiting electrical energy. Most common for instrumentation (4-20mA loops, HART sensors, thermocouples). Energy + temperature kept below ignition threshold even with multiple faults. Ex ia (2 faults tolerated, Zone 0), Ex ib (1 fault), Ex ic (no fault tolerance, Zone 2).
- Ex Marking
- Standardized marking on every Ex device : e.g., 'II 2 G Ex ia IIC T4 Ga' = Equipment Group II (surface, not mining), Category 2 (Zone 1 suitable), G (gas), protection Ex ia (intrinsic safety), gas group IIC (hydrogen-ready), T4 (≤135°C), EPL Ga (Zone 0 suitable). Read it like a license plate.
- ATEX vs IECEx
- Two co-existing certification schemes. **ATEX** = European Directive 2014/34/EU, mandatory for products on EU market, certification by Notified Bodies (e.g., DEKRA, TÜV). **IECEx** = global IEC scheme, accepted by many non-EU countries. Increasingly Ex products are dual-certified (ATEX + IECEx) on the same datasheet.
Notes & guidance
Reading an Ex marking
Every Ex-rated device has a marking that summarizes its certification. Once you know the format, you can grade compliance in 30 seconds. Example marking on a level transmitter:
II 2 G Ex ia IIC T4 Ga
│ │ │ │ │ │ │
│ │ │ │ │ │ └─ EPL Ga : suitable for Zone 0 (highest level)
│ │ │ │ │ └─ Temperature class T4 : max surface 135°C
│ │ │ │ └─ Gas group IIC : up to hydrogen / acetylene
│ │ │ └─ Protection method 'ia' : intrinsic safety, 2-fault tolerance
│ │ └─ G : gas atmosphere (D for dust)
│ └─ Category 2 : suitable for Zone 1 and 2 (and Zone 0 with the EPL Ga)
└─ Equipment Group II : surface industries (I = mining)
This level transmitter is suitable for the most demanding scenarios: Zone 0 (inside a fuel tank), hydrogen environment, surface temperature stays below 135°C even on fault.
A cheaper Zone 2 sensor would be marked something like : II 3 G Ex nA IIC T4 Gc (Category 3, EPL Gc, protection method ‘nA’ non-arcing).
Hierarchy of Ex protection methods
| Method | Code | Zone | Use case |
|---|---|---|---|
| Intrinsic Safety | Ex ia / ib / ic | 0 / 1 / 2 | Instrumentation, low-power signals (4-20mA, HART, thermocouples) |
| Flameproof | Ex d | 1 / 2 | Motors, lights, switchgear, junction boxes |
| Increased Safety | Ex e | 1 / 2 | Terminals, motors (limited arcing) |
| Pressurization | Ex p | 1 / 2 | Control cabinets in Zone 1 (constant overpressure with clean air) |
| Encapsulation | Ex m | 1 / 2 | Small electronics potted in resin |
| Oil immersion | Ex o | 1 (rare) | Transformers (legacy) |
| Powder filling | Ex q | 1 (rare) | Quartz-filled components |
| Non-sparking | Ex nA | 2 only | Low-cost Zone 2 instrumentation, no fault tolerance |
| Special | Ex s | per assessment | Novel methods, case-by-case approval |
Intrinsic Safety dominates instrumentation because :
- Compatible with standard 4-20mA loops (just add a barrier or galvanic isolator)
- Allows hot work (calibration, replacement) without permits
- Lower cost than flameproof enclosures
- Fault-tolerant by design
Flameproof dominates power equipment (motors, lights) because intrinsic safety can’t deliver the energy these devices need.
The 5 steps of an Ex installation
- Area Classification (engineering documentation per IEC 60079-10-1/2). Output: a plan with Zone 0/1/2 (or 20/21/22) coloring.
- Equipment Selection : choose devices with appropriate Ex marking for the zone. Check temperature class against the most volatile substance present.
- Cabling and Installation per IEC 60079-14. Cable glands, segregation of IS circuits, equipotential bonding.
- System Documentation : for IS loops, an installation document proving the loop assessment (matching barrier + cable parameters per IEC 60079-25).
- Periodic Inspection per IEC 60079-17. Visual annually, detailed every 3-6 years depending on environment severity.
In practice, most plants have an Ex register : every Ex device with its tag, location, certificate, last inspection date. Maintaining this register is a regulatory obligation in most jurisdictions and the first thing a compliance audit will check.
ATEX Directive 2014/34/EU — the EU legal layer
ATEX is the legal framework in the EU. IEC 60079 is the technical basis. The relationship:
- ATEX 2014/34/EU (the “Equipment Directive”) = mandatory for products placed on the EU market. CE marking + Ex marking + EC Type Examination Certificate by a Notified Body.
- ATEX 99/92/EC (the “Workplace Directive”) = employer obligations for workplaces with explosive atmospheres. Risk assessment, area classification, Explosion Protection Document.
- IEC 60079 series = the harmonized technical standards. Compliance with these grants presumption of conformity to ATEX.
The dual marking on a device certified for EU + global IECEx looks like :
ATEX : II 2 G Ex ia IIC T4 Ga
IECEx : Ex ia IIC T4 Ga
Certificates: PTB 14 ATEX 1234 X / IECEx PTB 14.0123X
Edition 3 / current work
IEC 60079 has many parts under continuous revision. Notable current activity:
- IEC 60079-0 : harmonization with newer IECEx scheme certifications, simplification of marking rules
- IEC 60079-10-1 and -10-2 : tighter quantitative methods for area classification (replacing qualitative judgement)
- Wireless in Ex : new parts addressing 5G, Wi-Fi, Bluetooth in Ex environments
- Hydrogen economy : increased rigor on Group IIC (hydrogen) given the H2 production / storage growth
- Battery storage : new guidance for large lithium battery installations in Ex contexts
Betroffene Branchen
- Oil & Gas (upstream platforms, refineries, LNG terminals)
- Chemical and petrochemical plants
- Pharmaceutical manufacturing (solvents)
- Pulp & Paper (flammable solvents)
- Grain handling and food processing (dust)
- Coal mining and metal processing (dust)
- Paint and varnish manufacturing
- Hydrogen production and storage (Group IIC critical)