Equipment Protection Levels (EPL)

Equipment Protection Levels (EPL)

Equipment Protection Level (EPL) indicates the likelihood that a piece of equipment will become a source of ignition. Defined in IEC/EN 60079-0, EPL provides a bridge between zone classification (the hazard) and protection methods (the solution).

EPL Definitions

Gas Atmospheres

EPL Protection Level Definition Suitable for
Ga Very high Equipment remains safe even with two independent faults Zone 0, 1, 2
Gb High Equipment remains safe with a single fault Zone 1, 2
Gc Enhanced Equipment remains safe under normal operation; may have additional measures for fault conditions Zone 2

Dust Atmospheres

EPL Protection Level Definition Suitable for
Da Very high Equipment remains safe even with two independent faults Zone 20, 21, 22
Db High Equipment remains safe with a single fault Zone 21, 22
Dc Enhanced Equipment remains safe under normal operation Zone 22

Mining

EPL Protection Level Definition
Ma Very high Equipment can be left energized in an explosive atmosphere; safe with two faults
Mb High Equipment must be de-energized when explosive atmosphere is detected; safe with one fault

EPL to Zone Mapping

The fundamental rule: the EPL of installed equipment must match or exceed the zone requirement.

Zone Minimum EPL Required
Zone 0 Ga
Zone 1 Gb (or Ga)
Zone 2 Gc (or Gb, or Ga)
Zone 20 Da
Zone 21 Db (or Da)
Zone 22 Dc (or Db, or Da)

Equipment with a higher EPL can always be used in a less hazardous zone (Ga equipment in Zone 2 is acceptable, though often unnecessarily expensive).

EPL to Protection Method Mapping

EPL Available Protection Methods
Ga Ex ia, Ex ma
Gb Ex db, Ex eb, Ex ib, Ex mb, Ex px, Ex py, Ex o, Ex q, [Ex Op pr, Ex Op sh]
Gc Ex dc, Ex ec, Ex ic, Ex mc, Ex pz, Ex nA, Ex nC, Ex nR, Ex nL
Da Ex ia, Ex ma, Ex ta
Db Ex ib, Ex mb, Ex tb, Ex pd
Dc Ex ic, Ex mc, Ex tc

EPL vs ATEX Categories

ATEX Directive 2014/34/EU uses categories rather than EPL. The mapping is:

ATEX Category EPL Equivalent Zone
1G Ga Zone 0, 1, 2
2G Gb Zone 1, 2
3G Gc Zone 2
1D Da Zone 20, 21, 22
2D Db Zone 21, 22
3D Dc Zone 22
M1 Ma Mines (energized in Ex atm)
M2 Mb Mines (de-energized in Ex atm)

In ATEX marking, the category appears as the number+letter: II 2G means Group II, Category 2G (= EPL Gb).

Fault Tolerance

The EPL letter suffix (a, b, c) directly relates to fault tolerance:

EPL "a" (Very High — Ga/Da/Ma)

  • Equipment must remain safe during normal operation AND with two independent faults
  • Must apply a safety factor of 1.5× to all protection parameters
  • Only Ex ia and Ex ma meet this requirement
  • Most rigorous testing and documentation

EPL "b" (High — Gb/Db/Mb)

  • Equipment must remain safe during normal operation AND with one fault
  • Safety factor of 1.5×
  • Covers most common industrial protection methods (Ex d, Ex e, Ex ib, Ex p, etc.)
  • Majority of installed Ex equipment worldwide is EPL Gb/Db

EPL "c" (Enhanced — Gc/Dc)

  • Equipment must remain safe during normal operation
  • May include measures to reduce ignition probability during fault conditions
  • Equipment may simply shut down or alarm on fault detection
  • Lower cost, suitable for Zone 2/22 where explosive atmosphere is unlikely

Practical Considerations

Over-specifying EPL

Installing Ga/Da equipment in Zone 2/22 is technically acceptable but:

  • Significantly more expensive
  • May be harder to maintain (Ex ia restrictions on modifications)
  • The zone classification should be reviewed first — the area may qualify as Zone 1

Under-specifying EPL

Installing Gc equipment in Zone 1 is a violation. This is a common compliance error discovered during inspections. Always verify:

  1. Zone classification drawing is current
  2. Equipment EPL matches or exceeds the zone
  3. Gas group and temperature class are also correct

Mixed Installations

A single piece of equipment can have multiple EPLs for different parts:


Ex db [ib Ga] IIC T4 Gb

This means the main enclosure is EPL Gb (flameproof), but it contains intrinsically safe circuits rated EPL Ga.

Creato per ingegneri che lavorano in aree pericolose. Contenuto basato su IEC 60079, ATEX 2014/34/EU e norme IECEx.

Non sostituisce documenti normativi ufficiali o consulenza ingegneristica professionale.