The question “which gland do I need for Zone 1?” is usually asked backwards. A Zone 1 cable gland is not a product family you pick from a catalogue: it is the smallest set of glands whose certification covers the zone your area classification drawing has already assigned to that point on site.

The zone is a site decision, not a product feature. It sets a minimum equipment protection level (EPL), a group and a temperature class, and the gland either carries a marking covering all three or it does not. This guide covers what a Zone 1 gland must satisfy, what changes in Zone 2, how dust zones differ, and the errors that show up most often on operating plants. For the background, see what an explosion proof cable gland does.

What a Zone 1 Cable Gland Has to Satisfy

Four requirements apply, and the zone sets only the first.

1. Minimum EPL. Equipment in Zone 1 must be at least EPL Gb. A gland marked Gb or Ga qualifies; a Gc-marked gland does not, however well it seals.
2. Gas group. The group marking must cover the gas present. IIC covers IIA, IIB and IIC atmospheres, which is why it is usual where the gas is mixed or not fully characterised.
3. Temperature class. The assembly must not reach a surface temperature hot enough to ignite the gas — a property of the gas and the equipment, not of the zone.
4. Ingress protection. The IP rating answers to the physical environment and, where dust is present, to the dust group. See choosing the right IP rating for how the levels differ.

The gland must also match the enclosure it enters: protection concept, entry thread form and size, and cable construction. A thread that does not fully engage is not a compliant entry even when the gland is certified, which is why thread form is confirmed before ordering.

Zone 0 is outside the range of a standard power cable gland; it calls for the highest level of protection and is normally served by intrinsically safe circuits. Zones 1, 2, 21 and 22 are where cable entries are actually specified.

Where Your Zone Comes From, and What It Does Not Tell You

Zones come from area classification, which is the site’s work rather than the supplier’s: IEC 60079-10-1 for gas, IEC 60079-10-2 for dust. In the EU that duty sits with the employer under the worker protection directive — a different instrument from the equipment directive the gland is certified against, as the ATEX and IECEx comparison explains.

A zone gives a location’s minimum EPL. It does not give you:

• the protection concept, which the enclosure decides, because the entry has to preserve it;
• the entry thread form or size, which the enclosure also decides;
• whether a barrier gland is needed, which follows from the cable construction;
• the gas group or temperature class, which come from the process gas data.

Zone 1 vs Zone 2: What Actually Changes

Between Zone 1 and Zone 2, one line of the specification changes: the EPL floor. Zone 1 requires Gb; Zone 2 requires Gc, which also makes Gb and Ga equipment acceptable there. Group, temperature class, ingress protection, thread and cable compatibility are unchanged.

A Zone 2 area may therefore be served by lighter, cheaper hardware, but only where the classification genuinely holds. Glands near flanges, vents, drains and fill points sit where gas collects, and those points are often reclassified upwards at the next drawing review. A Gb version and a Gc version of the same gland usually look identical as well, so check the marking rather than the box.

Reading the marking

A marking carries group and EPL alongside the concept: Ex db IIC Gb for a flameproof entry rated for Zone 1, Ex ec IIC Gc for an increased safety entry limited to Zone 2. A marking that cannot be read after installation, because it was painted over or turned away from the inspection position, cannot be verified in an audit. The Ex d and Ex e comparison covers why the enclosure rather than the zone chooses between the two concepts.

Gas zones and dust zones are not interchangeable

Zone 2 and Zone 22 read alike and are not. The number alone is not enough to specify from.

A gas group approval is not a dust group approval: dust zones add an ingress requirement a gas-only gland may not carry, and conductive dust is treated more severely because it can bridge insulation.

Four Selection Mistakes That Show Up on Site

Treating “Zone 1 means Ex d, Zone 2 means Ex e” as a rule. It is not one. Both concepts exist at EPL Gb, and the enclosure, not the zone, picks between them.

Reading Zone 2 as permission to skip certification. Zone 2 lowers the required EPL, it does not remove it. IP68 without an Ex marking is not a hazardous area gland.

Barrier or Non-Barrier Is a Cable Question, Not a Zone Question

The most common under-specification in Zone 2 is a compression gland on a cable that lets gas travel through the core. Whether a barrier is needed depends on the cable and on whether the enclosure volume makes an internal explosion credible, not on the zone number.

If a cable can pass gas along its core into a flameproof enclosure, a barrier type is called for in Zone 1 or Zone 2 alike. If it cannot, a compression type is normally sufficient in either zone, provided the EPL, group and ingress requirements are met.

One Site, Several Zones: Stocking and Spares

Real plants are rarely uniform: a Zone 1 pocket around a compressor or sampling point usually sits inside a larger Zone 2 area, and both sit inside the unclassified balance of the site.

The usual compromise is to standardise on the highest EPL in use at that location, accept the small premium, then keep lower-rated items physically separate and labelled. Relying on an installer to read a marking is a weak control, especially when the marking is only legible before the gland is fitted.

Installation and Inspection After the Zone Is Fixed

Once the zone is fixed it also fixes the inspection regime: under IEC 60079-17 the schedule is risk-driven, so higher-risk zones are inspected more often and in more detail. Cable entries are among the defects inspection finds most often.

Inspectors look for predictable things: seal damage, a thread that is not fully engaged, armour that was never clamped, a missing shroud or earth tag, a gland the wrong size for the cable, and a marking painted over during maintenance.

Three habits prevent most of it:

• record the gland size, cable range, marking and certificate reference for every entry, so the next inspection does not have to infer them;
• fit the accessory set the entry needs — locknut, sealing washer, earth tag, shroud — and confirm the enclosure wall thickness suits the thread length;
• keep the marking clean and visible, and do not paint over certified equipment.

A Spec Line You Can Copy

Most procurement failures are specification failures. A hazardous area gland order should carry every line below; anything left blank will be assumed by the supplier.

Certified glands ship with their certificate and material documentation; the CMP explosion proof gland range is one example of the documentation set an Ex order should include. An order that names a certificate rather than a marketing description is far easier to verify on delivery.

Next Step

Start with the drawing, not the catalogue. Pull the zone, group and temperature class for the location, confirm the enclosure’s concept and entry thread, then specify against those values. Suitable glands are available in nickel-plated brass for most onshore service and in stainless steel where chlorides, sour service or washdown are present; a representative entry is the PG42 gland for hazardous areas. If the zone boundary on your drawing is ambiguous, settle that classification question before ordering.

FAQ

Can I use a Zone 2 cable gland in Zone 1?

Not if it is marked Gc only. Zone 1 requires at least EPL Gb, so a Gc-marked gland is inadmissible regardless of its IP rating or material. If the same gland exists in a Gb-marked version, that is the version for a Zone 1 entry.

Is a Zone 1 cable gland the same as an explosion proof cable gland?

Not quite. “Explosion proof” describes a protection approach, usually flameproof Ex d. A Zone 1 gland is defined by its EPL, so it may be flameproof, increased safety or another concept rated at Gb. Zone 1 is the requirement; flameproof is one way to meet it.

Do Zone 1 installations always need barrier glands?

No. A barrier is required where gas or vapour can migrate through the cable into the enclosure, which is a property of the cable construction and the enclosure rather than of the zone. A Zone 1 entry on a suitable filled cable may not need one; a Zone 2 entry on an unfilled multi-core cable may well need one.

What is the difference between Zone 2 and Zone 22?

Zone 2 is a gas zone: an explosive gas atmosphere is not expected during normal operation and, if it occurs, lasts only briefly. Zone 22 is a dust zone with the same expectation about frequency. They differ in group marking, in the ingress protection needed for dust, and in how surface temperature is assessed.

Can I use an IP68 gland in Zone 2?

Only if it also carries Ex certification for that zone. IP68 addresses water and dust ingress and says nothing about ignition risk. Many glands are both IP68 and Ex certified; the Ex marking is the part that qualifies an entry for a hazardous area.