Zones: how likely is an explosive atmosphere?
| Gas zone | Dust zone | Explosive atmosphere is present | Required EPL |
|---|---|---|---|
| Zone 0 | Zone 20 | continuously, for long periods or frequently | Ga / Da |
| Zone 1 | Zone 21 | likely to occur occasionally in normal operation | Ga or Gb / Da or Db |
| Zone 2 | Zone 22 | not likely in normal operation, and only for a short time if it does | Ga, Gb or Gc / Da, Db or Dc |
Zones are set by the plant's area classification (IEC 60079-10-1 for gas, IEC 60079-10-2 for dust). The equipment protection level (EPL) on the product must match or exceed what the zone needs.
Protection concepts
- Ex d (flameproof, IEC 60079-1): the enclosure contains an internal explosion and stops it escaping. Used for motors, junction boxes, control stations and light fittings.
- Ex e (increased safety, IEC 60079-7): extra measures prevent arcs, sparks and hot spots. Common for terminal boxes and light fittings.
- Ex i (intrinsic safety, IEC 60079-11): energy is limited so a spark cannot ignite the gas; levels ia, ib, ic. Used for instruments and signals, with barriers or isolators in the safe area.
- Ex nA / Ex ec (Zone 2 only): non-sparking equipment; the older "nA" has largely moved into "ec" under IEC 60079-7.
- Ex t (dust, IEC 60079-31): protection by enclosure against dust ingress and surface temperature.
Other concepts include Ex p (pressurisation) and Ex m (encapsulation). One product can combine concepts, such as an Ex d motor with an Ex e terminal box.
Gas groups and temperature classes
| Group | Typical gas |
|---|---|
| IIA | propane |
| IIB | ethylene |
| IIC | hydrogen, acetylene |
IIC equipment is also suitable for IIB and IIA; the reverse is not true. Dust groups are IIIA (combustible flyings), IIIB (non-conductive dust) and IIIC (conductive dust).
| Temperature class | T1 | T2 | T3 | T4 | T5 | T6 |
|---|---|---|---|---|---|---|
| Max. surface temperature | 450 °C | 300 °C | 200 °C | 135 °C | 100 °C | 85 °C |
The equipment's maximum surface temperature must be below the ignition temperature of the gas present, so a T4 product also covers T1 to T3 gases.
Ambient temperature in Saudi plants
Unless marked otherwise, Ex equipment is certified for an ambient of −20 °C to +40 °C. Outdoor plant areas on the Red Sea and Gulf coasts can be hotter, so check the marked ambient range (Ta) on the certificate and the nameplate against the site's design temperature. A higher ambient can also lower the temperature class, which the maker states.
ATEX or IECEx?
ATEX is the European Union's legal framework (Directive 2014/34/EU), marked with the hexagon Ex symbol, the equipment group and category, for example II 2 G (category 1, 2, 3 broadly matching zones 0, 1, 2). IECEx is the international certification scheme based on the IEC 60079 standards, with a certificate you can check online. Many products carry both. The plant owner's or project specification states which certification is accepted, so check it before ordering.
Reading an Ex marking
Ex db eb IIC T4 Gb
- db: flameproof enclosure, protection level b (Zone 1)
- eb: increased safety, level b, for example the terminal compartment
- IIC: gas group, suitable for IIA, IIB and IIC
- T4: maximum surface temperature 135 °C
- Gb: equipment protection level for Zone 1 (and Zone 2)
Cable glands for Ex equipment
The gland is part of the protection. Use glands certified for the concept of the enclosure: Ex d glands for flameproof enclosures and Ex e glands for increased-safety enclosures (many glands are certified Ex db eb for both). IEC 60079-14, the installation standard, decides when a barrier gland (sealed with compound around each core) is needed on flameproof enclosures. The gland must also suit the cable type and armour, keep the IP rating, and match the entry thread exactly (metric or NPT). Unused entries are closed with certified Ex stopping plugs.
What to send us for a quotation
Zone, gas or dust group and temperature class from the area classification, the required certification (ATEX, IECEx or both), the site ambient temperature, IP rating, voltage, and for glands the cable type, outer diameter, armour and entry thread. A photo of the existing nameplate helps for replacements. We quote certified items with their certificates.
Common questions
Can Zone 1 equipment be used in Zone 2?
Yes. Equipment with EPL Gb (Zone 1) is also suitable for Zone 2. The reverse is not allowed: Gc equipment is only for Zone 2.
What does IIC mean on Ex equipment?
It is the gas group for the most easily ignited gases, such as hydrogen and acetylene. IIC equipment can also be used for IIB and IIA gases.
Is ATEX accepted in Saudi Arabia?
It depends on the plant owner and the project specification. Many specifications accept ATEX, IECEx or both; check the requirement before ordering.
Need these items? Send your list or a nameplate photo; your quotation arrives within 24 hours.
This guide is general information. Final selection must follow the project design, the applicable standards and the maker's data.