Which Ex protection concepts are allowed in Zone 1 and which only in Zone 2?
Abstract
Zone 1 needs EPL Gb or Ga: db, eb, ib, pxb, pyb, mb, ob, q, and all Ga levels. Zone 2 also accepts EPL Gc: dc, ec, ic, pzc, mc, oc, nC and nR. The level letter (b or c) and the EPL at the end of the marking decide, not the concept letter.
Zone 1 needs equipment with equipment protection level (EPL) Gb or Ga (ATEX category 2G or 1G). That covers flameproof db, increased safety eb, intrinsic safety ib, pressurisation pxb and pyb, encapsulation mb, liquid immersion ob, powder filling q, and every Ga level. Zone 2 accepts all of those plus the EPL Gc levels: dc, ec, ic, pzc, mc, oc, nC and nR, which are designed to be safe in normal operation only.
Short answer
- The rule: Zone 1 requires Ga or Gb; Zone 2 accepts Ga, Gb or Gc (IEC 60079-14 default, matching categories 1, 2 and 3 in Directive 1999/92/EC).
- Zone 1 levels:
db,eb,ib,pxb,pyb,mb,ob,q, plusia,maand other Ga equipment. Non-electricalEx hequipment and opticalopsystems are suitable when marked Gb (or Ga). - Zone 2 only:
dc,ec,ic,pzc,mc,oc,nC,nR, and older markingsnAandnL, all EPL Gc. - Same concept, two levels: Ex e exists as
eb(Zone 1) andec(Zone 2); Ex i asibandic; Ex d asdbanddc. The second letter is what matters. - Read the end of the marking:
Gbmeans Zone 1 is acceptable;Gcmeans Zone 2 only, unless a documented risk assessment under IEC 60079-14 justifies otherwise.
Why Zone 2 can accept a lower level
Zones describe how likely the explosive atmosphere is. In Zone 1 it is likely in normal operation, so equipment must stay safe in normal operation and in expected malfunctions such as a loose terminal or a single component failure: that is EPL Gb. In Zone 2 the atmosphere is not expected in normal operation and, if it occurs, lasts only a short time. An ignition would need two unlikely events at once, so equipment that is safe in normal operation (EPL Gc) is accepted.
The higher level always covers the lower zone. Gb equipment can go in Zone 2, and Ga equipment in Zone 1 or 2. The reverse is not allowed by default.
Levels of protection by zone
| Type of protection | Standard | Zone 1 (EPL Gb) | Zone 2 only (EPL Gc) |
|---|---|---|---|
| Flameproof "d" | IEC 60079-1 | db | dc (small devices with switching contacts) |
| Increased safety "e" | IEC 60079-7 | eb | ec (formerly type nA) |
| Intrinsic safety "i" | IEC 60079-11 | ib (and ia) | ic (formerly nL) |
| Pressurisation "p" | IEC 60079-2 | pxb, pyb | pzc |
| Encapsulation "m" | IEC 60079-18 | mb (and ma) | mc |
| Liquid immersion "o" | IEC 60079-6 | ob | oc |
| Powder filling "q" | IEC 60079-5 | q | (no separate level) |
| Type "n" | IEC 60079-15 | (none) | nC, nR |
| Non-electrical "h" | ISO 80079-36, ISO 80079-37 | Ex h ... Gb | Ex h ... Gc |
Ga levels such as ia and ma are acceptable in both zones. For dust zones the same logic applies with Db (Zone 21) and Dc (Zone 22), using tb/tc, ib/ic, mb/mc and pxb, pyb/pzc.
Choosing in practice: Zone 1 versus Zone 2
The c levels exist because they are simpler, lighter and cheaper. A few examples of what changes when the area is Zone 2 instead of Zone 1:
- Motors: a cage induction motor can be
Ex ecrather thanEx eborEx db; the time tE that IEC 60079-7 asks for on line-started eb machines is not needed, because the standard treats normal industrial motor protection as sufficient for ec machines. - Instruments:
Ex icloops need less margin thaniband allow simpler interfaces, but the loop still has to be documented. - Analyser cabinets: for an enclosure with ordinary (non-Ex) contents, the IEC 60079-14 table (2007 edition) calls for an alarm and automatic switch-off on loss of pressurisation in Zone 1 (
pxb), but only an alarm in Zone 2 (pzc). - Luminaires and junction boxes:
ecornR(restricted breathing) designs replace heavier Zone 1 products.
Example: A pump in a well-ventilated outdoor area is classified Zone 2 around the seal and Zone 1 within a small radius of a sampling point. The pump motor, outside the Zone 1 envelope, can be Ex ec IIA T3 Gc. The pressure transmitter next to the sampling point sits inside Zone 1 and must be at least Gb, for example Ex ib IIC T4 Gb or Ex db IIC T6 Gb. If the motor is moved into the Zone 1 envelope, an ec motor is no longer acceptable.
Common mistakes
- Reading only the concept letter. "It is Ex e, so it is fine for Zone 1" is wrong if the marking says
ecandGc. See can Ex ec be used in Zone 1. - Treating Zone 2 as "anything goes". Equipment in Zone 2 still needs EPL Gc, or a documented assessment; see standard equipment in Zone 2.
- Forgetting the gas group and temperature class. The right level is only one of three checks; IIA/IIB/IIC and the T class must also match the area.
- Mixing levels in one loop. An
ibfield device on an[Ex ic]interface forms an ic loop, suitable for Zone 2 only.
Related on excodex
- Ex protection concepts at a glance: d, e, i, p, m, o, q, n and t
- Equipment Protection Levels (EPL): Ga, Gb, Gc, Da, Db, Dc and how they match zones
- Hazardous area zones explained: Zone 0, Zone 1 and Zone 2
- Which protection concepts can be used in Zone 0?
- Tools: Ex marking check, standards space IEC 60079-14
Standards and further reading
- IEC 60079-14:2024 (edition 6), electrical installations design, selection and erection; contains the tables relating zones, EPLs and types of protection (public preview of contents): standards.iteh.ai
- IEC 60079-15:2017 (edition 5), type of protection "n": nC and nR, abstract: webstore.iec.ch
- IEC 60079-1:2014, flameproof enclosures, levels da, db and dc (replaced by IEC 60079-1:2026; 2014 text incorporated by reference in US federal regulations): law.resource.org
- IEC 60079-7:2015, increased safety, levels eb and ec: law.resource.org
- IEC 60079-2 (pressurisation, pxb, pyb, pzc), abstract of EN 60079-2: standards.iteh.ai
- IEC 60079-11:2023, intrinsic safety: webstore.iec.ch
- Directive 1999/92/EC, Annex II Part B (categories by zone): legislation.gov.uk
This article is general technical information prepared by the excodex editorial team. It does not replace the applicable standards, the equipment certificates and instructions, national regulations or the assessment of a competent person.