Why do newer markings say 'Ex db' or 'Ex eb' instead of 'Ex d' or 'Ex e'?
Abstract
The added letter is the level of protection (a, b or c), which matches the EPL Ga, Gb or Gc. IEC 60079-1:2014 split flameproof into da, db, dc and IEC 60079-7:2015 split increased safety into eb and ec. Older Ex d and Ex e equal today's db and eb.
The extra lower-case letter is the level of protection: a, b or c, matching the equipment protection level (EPL) Ga, Gb or Gc. Flameproof and increased safety used to have only one level, so Ex d and Ex e needed no letter. When IEC 60079-1:2014 introduced the flameproof levels da, db and dc, and IEC 60079-7:2015 the increased safety levels eb and ec, the marking had to say which level applies. An older Ex d or Ex e product corresponds to today's db or eb (EPL Gb).
Short answer
db= flameproof enclosure, level b, EPL Gb.eb= increased safety, level b, EPL Gb.- The level letter lets one protection standard cover several EPLs:
ec(Gc) is the former Zone 2 typenAmoved into the increased safety standard, anddc(Gc) took over enclosed-break devices from the type n standard. - IEC 60079-7:2015 states that the former marking
eis replaced byebandnAbyec: a product certified to the new edition takes the new marking even if nothing else about it changes. - Equipment already marked
Ex dorEx eis not downgraded or invalidated by the new marking; it is selected as Gb equipment. - Intrinsic safety has used levels (
ia,ib) for decades; encapsulation, pressurisation and dust enclosures followed in the 2000s.
How the level letters arrived, concept by concept
| Type of protection | Older marking | Current levels (EPL) | Where the change came from |
|---|---|---|---|
| Flameproof enclosure | d | da (Ga), db (Gb), dc (Gc) | IEC 60079-1:2014 (edition 7); da only for catalytic sensors of portable gas detectors, dc from type n enclosed-break devices |
| Increased safety | e (and nA for Zone 2) | eb (Gb), ec (Gc) | IEC 60079-7:2015 (edition 5), which absorbed type nA |
| Intrinsic safety | ia, ib | ia (Ga), ib (Gb), ic (Gc) | ic added in EN 60079-11:2007 |
| Encapsulation | m, then ma, mb | ma (Ga), mb (Gb), mc (Gc) | ma and mb in EN 60079-18:2004, mc added in EN 60079-18:2009 |
| Pressurisation | p, then px, py, pz | pxb, pyb (Gb), pzc (Gc) | px, py, pz from the mid-2000s; EPL letter added in IEC 60079-2:2014 |
| Dust enclosure | tD | ta (Da), tb (Db), tc (Dc) | EN 60079-31:2009 |
The IEC 60079-0 marking list of 2004 still shows plain "d" and "e" next to "ia", "ib", "ma", "mb", "px", "py" and "pz". The EPL concept followed in IEC 60079-0 of 2007 (EN 60079-0:2009 in Europe), and over the next decade each protection standard was revised so that its level letters line up with the EPL.
Why the change was made
One standard, several levels. Before the change, Zone 2 versions of increased safety and flameproof devices lived in a separate standard (type of protection "n", IEC 60079-15) with their own codes nA and nC. Moving them into the main standards as ec and dc put each technique and its relaxed Zone 2 variant under one set of rules.
A self-checking marking. With the level letter, the type of protection and the EPL at the end of the marking agree: Ex db IIC T4 Gb, Ex ec IIC T4 Gc, Ex ia IIC T6 Ga. An inspector can see at a glance whether a combination is consistent.
Clear selection. The letter makes it obvious that eb and ec are not interchangeable even though both are "increased safety". Without it, an e marking could not show whether the product was built to the full Zone 1 requirements.
What it means for existing and mixed installations
The US Coast Guard's hazardous location guidance notes that the EPL-related letter did not exist in earlier editions of the standards and may be missing from older markings. That is expected and is not a defect. Treat older markings as follows:
| Marking on existing equipment | Read as | Zones |
|---|---|---|
Ex d IIB T4 or EEx d IIB T4 | Flameproof, level equivalent to db, EPL Gb | 1 and 2 |
Ex e II T3 or EEx e II T3 | Increased safety, level equivalent to eb, EPL Gb | 1 and 2 |
Ex nA II T3 | Non-sparking, equivalent to ec, EPL Gc | 2 only |
Ex ia IIC T4 | Intrinsic safety ia, EPL Ga | 0, 1 and 2 |
Both the European notified bodies' list of changes between standard editions and the foreword of IEC 60079-7:2015 note that such revisions should not normally affect equipment already placed on the market. Inspection of older equipment is done against the standards that applied when it was installed (IEC 60079-17). A replacement bought today will simply carry the new marking.
Common mistakes
- Rejecting a spare because it says
Ex dbwhile the drawing saysEx d. For selection they are the same level; check group, T-class and ambient range instead. - Reading the b in
dbas gas group IIB. It is the level of protection; the gas group appears separately. - Assuming
ecis a lighterebthat still suits Zone 1. It is the formernA, Zone 2 only.
Related on excodex
- How to read an Ex marking: decoding II 2 G Ex db IIC T4 Gb step by step
- Equipment Protection Levels (EPL): Ga, Gb, Gc, Da, Db, Dc and how they match zones
- Can Ex nA equipment still be installed now that Ex ec has replaced it?
- Can old equipment marked 'EEx' still be used in a hazardous area?
- Tools: Ex marking check; standards spaces IEC 60079-1, IEC 60079-7
Standards and further reading
- IEC 60079-1:2014, flameproof enclosures "d", with levels da, db and dc (a 2026 edition has since been published): preview
- IEC 60079-7:2015, increased safety "e", levels eb and ec; foreword on the marking changes from e to eb and nA to ec: law.resource.org
- IEC 60079-0:2004, marking list before EPLs: law.resource.org
- ExNB clarification sheet ExNB/10/388/CS, changes between European standard editions: prestations.ineris.fr (PDF)
- US Coast Guard OCS National Center of Expertise, Drill Down 26, protection techniques: dco.uscg.mil
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.