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How to Read IECEx Equipment Markings (Ex db IIC T6 Gb Explained)

Learn how to read IECEx equipment markings, including Ex db, IIC, T6, and Gb, and understand what each marking means.
IECEx equipment nameplate showing Ex db IIC T6 Gb hazardous area certification marking

IECEx equipment markings provide critical information about protection concepts, gas groups, temperature classes, and equipment protection levels.

When selecting hazardous area equipment, one of the most important skills is understanding how to read IECEx equipment markings.

A marking such as:

Example IECEx Marking

Consider the following marking:

Ex db IIC T6 Gb

contains critical information about the equipment's protection concept, gas group suitability, temperature class, and equipment protection level.

Understanding these markings helps engineers verify whether equipment is suitable for a specific hazardous area application.

What Does "Ex" Mean?

The "Ex" symbol indicates that the equipment is designed and certified for use in explosive atmospheres.

This is the internationally recognized designation used within the IEC 60079 standards and IECEx certification system.

What Does "db" Mean?

The letters following Ex identify the protection concept.

In this example:

Ex db

indicates Flameproof Protection.

The enclosure is designed to contain an internal explosion and prevent ignition of the surrounding atmosphere.

Ex db equipment is commonly used for:

  • Lighting fixtures

  • Junction boxes

  • Motor starters

  • Control stations

What Does "IIC" Mean?

IIC identifies the gas group.

Gas groups classify flammable gases according to their ignition characteristics.

IIC represents the most demanding gas group and includes gases such as:

  • Hydrogen

  • Acetylene

Equipment certified for IIC applications may generally be used in IIA and IIB locations as well.

What Does "T6" Mean?

T6 identifies the temperature class.

Temperature classes limit the maximum surface temperature of equipment.

T6 equipment has a maximum permitted surface temperature of:

85°C

This helps prevent equipment from becoming an ignition source.

What Does "Gb" Mean?

Gb is the Equipment Protection Level (EPL).

The EPL system indicates the level of protection provided by equipment.

For gas atmospheres:

  • Ga = Very high protection

  • Gb = High protection

  • Gc = Enhanced protection

Equipment marked Gb is commonly used in Zone 1 applications.

Breaking Down the Full Marking

MarkingMeaning
ExExplosion protected equipment
dbFlameproof protection
IICGas group
T6Temperature class
GbEquipment Protection Level

Understanding each element allows engineers to evaluate equipment suitability quickly and accurately.

Why Equipment Markings Matter

IECEx markings help engineers verify:

  • Hazardous area suitability

  • Protection concept

  • Gas group compatibility

  • Temperature class requirements

  • Compliance with applicable standards

Reviewing equipment markings should always be part of hazardous area equipment selection.

Frequently Asked Questions

Does IIC include IIA and IIB?

Generally, yes. IIC equipment may typically be used in IIA and IIB applications.

Is T6 always better than T4?

T6 provides a lower maximum surface temperature, but equipment selection should always be based on the actual hazardous substance and application requirements.

Can Gb equipment be installed in Zone 0?

Not necessarily. Equipment must be suitable for the applicable area classification and protection level requirements.

Conclusion

IECEx equipment markings provide a concise method of communicating critical hazardous area information.

By understanding the meaning of Ex, protection concepts, gas groups, temperature classes, and EPL ratings, engineers can make informed equipment selection decisions and maintain compliance with hazardous area standards.

References

  • IEC 60079-0

  • IEC 60079-1

  • IECEx System