Can Ex ec equipment be used in Zone 1?
Abstract
No. Ex ec gives only EPL Gc (ATEX category 3G), which is for Zone 2. Zone 1 needs EPL Gb or Ga, for example Ex eb, Ex db, Ex ib or Ex pxb. The only route for Ex ec items in Zone 1 is inside an enclosure certified to give EPL Gb, such as Ex pyb.
No. Level of protection "ec" provides EPL Gc, which is suitable only for Zone 2. Zone 1 requires EPL Gb (or Ga), so increased safety equipment for Zone 1 must be level "eb", or the equipment must use another concept that gives Gb, such as flameproof Ex db, intrinsic safety Ex ib or pressurisation Ex pxb.
Short answer
- IEC 60079-7 defines two levels of increased safety: eb gives EPL Gb (or Mb in mines) and ec gives EPL Gc.
- Zone 1 needs EPL Gb or Ga. In the EU, Directive 1999/92/EC requires category 1 or 2 equipment in Zone 1 (a narrow derogation exists only where the explosion protection document justifies equivalent safety with other measures); Ex ec equipment is category 3 (
II 3 G). - The shared letter "e" does not make ec and eb interchangeable. ec is the former non-sparking type nA, rewritten in the increased safety format.
- An Ex ec item may sit inside a Zone 1 enclosure only where that enclosure is certified to provide EPL Gb for Gc contents, as in pressurisation level pyb.
- Higher always covers lower: Ex eb equipment can be used in Zone 2, but Ex ec cannot be used in Zone 1.
Why ec stops at Zone 2
The EPL describes how many faults the equipment can tolerate before it could ignite gas. In Zone 1 an explosive atmosphere is expected from time to time in normal operation, so equipment there must stay safe in normal operation and with the malfunctions that can be expected (EPL Gb). In Zone 2 gas is present only rarely and briefly, so equipment only has to be safe in normal operation and regular expected occurrences (EPL Gc). The chance that a fault and a gas cloud coincide is then judged low enough.
IEC 60079-7 reflects this directly. For level eb the standard excludes semiconductors and electrolytic capacitors, because expected malfunctions in them could cause excessive temperatures, arcs or sparks. For level ec they are allowed, because they are evaluated only for normal conditions and regular expected occurrences. Several construction rules are also relaxed for ec:
| Requirement in IEC 60079-7:2015 | Level eb (EPL Gb) | Level ec (EPL Gc) |
|---|---|---|
| Semiconductors and electrolytic capacitors | Excluded | Permitted |
| Maximum rated voltage | 11 kV | 15 kV |
| Clearance and creepage distances | Larger values | Smaller values |
| Thermal stability margin of solid insulation | At least 20 K above the maximum service temperature | At least the maximum service temperature |
| Retention of pluggable connections | Higher test forces | Lower test forces |
Each relaxation is acceptable for Zone 2 and unacceptable for Zone 1. A drive, power supply or LED driver built to ec cannot be "upgraded" to Zone 1 by the installer.
Reading the marking
The level of protection and the EPL are both on the label, so the check is quick:
| Marking example | EPL | Zone 1? |
|---|---|---|
II 2 G Ex eb IIC T4 Gb | Gb | Yes |
II 2 G Ex db eb IIB T4 Gb | Gb | Yes (flameproof with increased safety terminals) |
II 3 G Ex ec IIC T4 Gc | Gc | No, Zone 2 only |
II 3 G Ex nA IIC T3 Gc | Gc | No, Zone 2 only |
II 3 G Ex ec nC IIC T4 Gc | Gc | No, Zone 2 only |
When a marking combines several concepts, the equipment as a whole has one EPL, shown at the end. If any part of the marking says Gc, read the last symbol: that EPL is what the location must accept. Older equipment can be marked Ex e without the b or c; before 2015 increased safety had only one level, equivalent to today's eb, so such products are Zone 1 equipment.
Worked example: a motor for a pump in Zone 1
A pump skid sits in a Zone 1 area classified for propane, group IIA, and the site specification asks for T3. A supplier offers a motor marked II 3 G Ex ec IIC T3 Gc because it is cheaper than the eb version.
- Gas group IIC covers IIA, and T3 matches, but the EPL is Gc. The motor is not acceptable for Zone 1.
- Acceptable options: an
Ex ebmotor with EPL Gb, which also brings eb-specific requirements such as the tE time and its protective device; anEx dborEx db ebmotor; or a motor of another Gb concept. - If the motor is to run on a variable frequency drive, the certificate must cover converter operation; see Ex e motors on a VFD.
Had the skid stood in Zone 2, the ec motor would have been a sound and economical choice.
Common mistakes
- Reading "Ex e" as one category. eb and ec are two levels with different EPLs; always read the level letter and the EPL.
- Relying on the gas group. IIC or T6 says nothing about the zone; the EPL decides.
- Assuming a better IP rating raises the EPL. A sealed, IP66 ec luminaire is still Gc.
- Putting Ex ec items into an ordinary box in Zone 1. Only a certified enclosure concept such as pyb can provide the missing protection.
Related on excodex
- Ex ec, Ex nA and Ex nR: protection for Zone 2
- Increased safety (Ex e): preventing sparks, arcs and hot spots
- Equipment Protection Levels (EPL): Ga, Gb, Gc, Da, Db, Dc and how they match zones
- Which Ex protection concepts are allowed in Zone 1 and which only in Zone 2?
- Tools: Ex marking check, propane; standards spaces IEC 60079-7, IEC 60079-14
Standards and further reading
- IEC 60079-7, equipment protection by increased safety "e", levels eb and ec (2015 with Amendment 1 of 2017; a new edition is in draft).
- IEC 60079-14, design, selection and installation, including the zone to EPL relationship (edition 6, 2024).
- IEC 60079-2, pressurised enclosures, including level pyb for Gc contents.
- Directive 1999/92/EC, Annex II, Part B, categories of equipment for each zone: legislation.gov.uk
- IEC 60079-7:2015 text, scope and eb/ec requirements: law.resource.org
- SafeWork NSW TestSafe, pressurisation levels (pyb contents at least EPL Gc): nsw.gov.au
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.