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IEC 60079-7 Explained: Increased Safety "e"

Understand IEC 60079-7 and Ex eb versus Ex ec, including terminals, insulation, temperature limits, equipment marking, and selection.
Engineer checking terminal connections inside an increased safety electrical enclosure.

Increased Safety, marked Ex e, is used for electrical equipment designed with additional measures to reduce the risk of ignition in an explosive gas atmosphere. Rather than containing an internal explosion, as flameproof protection does, increased safety focuses on the equipment's construction and electrical characteristics.

The requirements are specified in IEC 60079-7, Explosive atmospheres – Part 7: Equipment protection by increased safety "e". The standard covers the design, construction, testing and marking of equipment and Ex components using this protection concept.

In practical equipment reviews, the details matter. Terminal arrangements, insulation, electrical separation, temperature rise and the certified configuration can all affect whether a product is suitable for its intended application.

How Increased Safety Works

Electrical equipment can become an ignition source if connections overheat, insulation fails or electrical faults create excessive temperatures, arcs or sparks. Increased Safety requirements address relevant risks through additional construction and verification measures.

Depending on the equipment, these measures can involve:

  • Secure electrical connections and suitable conductor termination.
  • Specified insulation and separation between conductive parts.
  • Control of temperature rise under the applicable operating conditions.
  • Construction requirements for terminals, windings, lamps, batteries or other relevant parts.
  • Verification and testing required by the applicable standard.

Ex e is not simply a claim that equipment will never produce heat or experience an electrical fault. Its protection level depends on the applicable requirements and the construction assessed for certification.

IEC 60079-7 and IEC 60079-0

IEC 60079-7 supplements and modifies the general equipment requirements in IEC 60079-0. The two standards are used together as applicable to the equipment.

Standard Purpose
IEC 60079-0 General requirements for Ex equipment, including relevant construction, testing and marking provisions.
IEC 60079-7 Additional requirements specific to Increased Safety protection.

When reviewing a certificate or technical datasheet, check which editions of the standards are listed and whether they match the applicable certification basis and project requirements.

Ex eb and Ex ec: What Is the Difference?

IEC 60079-7 defines two levels of protection for increased safety equipment: eb and ec. They are not interchangeable designations.

Characteristic Ex eb Ex ec
Equipment Protection Level Mb or Gb, depending on the equipment and application Gc
Typical gas-zone application Gb is commonly associated with Zone 1; Mb applies to the relevant mining application Gc is commonly associated with Zone 2
Rated voltage scope in IEC 60079-7:2015+A1:2017 Up to 11 kV RMS, AC or DC Up to 15 kV RMS, AC or DC
Electronic components Semiconductors and electrolytic capacitors are excluded from the specified eb provisions These components can be included subject to the applicable requirements

The table summarizes distinctions in the cited edition of IEC 60079-7. The applicable standard, certificate and equipment construction must be checked for a real product.

Do not choose between Ex eb and Ex ec based on the zone alone. Confirm the required Equipment Protection Level (EPL), equipment type, complete marking and project specification. An Ex ec product marked Gc does not meet a requirement for EPL Gb simply because both products use increased safety protection.

Terminals and Electrical Connections

Terminals are a common application of increased safety. A poor connection can create local heating, while incorrect conductor installation can affect the reliability of the electrical connection.

When reviewing an Ex e terminal box or junction box, pay attention to:

  • Terminal type and approved conductor range.
  • Conductor cross-section and current rating.
  • Specified tightening torque, where applicable.
  • Clearance between conductive parts.
  • Insulation and separation requirements.
  • Space available for the intended number of conductors.
  • Temperature limits and the certified equipment configuration.

These are not independent checks. The permitted conductor size, terminal arrangement and current loading must be consistent with the equipment's assessed construction.

Example: A supplier may offer a terminal box with an Ex eb marking, but the proposed terminals may not accommodate the conductor size specified in the project datasheet. The correct response is to confirm the certified terminal arrangement and obtain a compliant configuration—not to assume that any terminal block can be substituted.

Creepage and Clearance Distances

Electrical separation is another important aspect of increased safety equipment.

Creepage distance

Creepage distance is the shortest distance along the surface of an insulating material between conductive parts.

Clearance distance

Clearance is the shortest distance through air between conductive parts.

Insufficient separation can increase the risk of electrical breakdown, tracking or flashover. The required distances depend on the applicable standard provisions and factors such as voltage, insulation material and the construction being assessed.

There is no single creepage or clearance value that applies to every Ex e product. Use the applicable requirements and certified design rather than applying a generic dimension during equipment selection or modification.

Temperature Rise and Insulation

Electrical losses generate heat. In increased safety equipment, the relevant temperature limits must be controlled under the conditions specified by the applicable requirements.

Temperature performance can be affected by current loading, conductor connections, winding design, insulation characteristics, ambient temperature and heat dissipation. The significance of each factor depends on the equipment type.

For example, a motor and a terminal enclosure do not have identical thermal considerations. A motor assessment may involve winding temperatures and operating conditions, while a terminal enclosure review may focus on connections, conductor loading and the permitted configuration.

The equipment marking and documentation should be checked for its temperature classification, ambient range and any relevant restrictions. A correct T-class alone does not establish suitability if the site ambient temperature falls outside the certified range.

Equipment Commonly Using Ex e

Increased safety is used for equipment whose design can meet the applicable requirements for this protection method. Examples can include:

  • Terminal boxes and junction boxes.
  • Electric motors.
  • Electrical connection compartments.
  • Selected luminaires and lighting equipment.
  • Terminal and connection devices.
  • Other equipment or Ex components assessed for increased safety.

The equipment category alone does not establish compliance. A standard industrial junction box, motor or luminaire is not automatically suitable for hazardous areas just because its construction appears similar to an Ex e product.

Understanding Ex e Marking

A marking such as the following illustrates the information that may appear on increased safety equipment:

Ex eb IIC T4 Gb

In this example:

  • Ex eb identifies the protection type and level.
  • IIC identifies the gas group.
  • T4 indicates a maximum surface temperature of 135 °C under the applicable gas temperature-class system.
  • Gb identifies the Equipment Protection Level.

This is an illustrative marking, not a complete specification for a real product. Actual markings may include additional information or multiple protection concepts. Check the complete marking against the certificate and the intended application.

For more detail, see How to Read IECEx Equipment Markings.

Ex e Compared With Ex d

Both protection methods are used in explosive atmospheres, but they rely on different design principles.

Aspect Ex e Ex d
Protection principle Additional measures reduce the likelihood of ignition. A flameproof enclosure contains an internal explosion and prevents flame transmission.
Key design concerns Connections, insulation, separation, temperature and applicable construction requirements. Enclosure strength, flamepaths, joints and certified assembly.
Typical marking examples Ex eb or Ex ec Ex db

Neither method is universally suitable for every device. Selection depends on the required protection level, equipment design, hazardous area and project conditions.

What to Check During Technical Bid Evaluation

For procurement and engineering teams, the most useful review compares the supplier's offer with the RFQ, project datasheet and supporting certification documents.

Check What to verify
Equipment marking Protection type, EPL, gas group and temperature information.
Certificate Equipment identity, applicable standards, marking and any stated limitations.
Terminals Terminal type, conductor range, loading and certified arrangement.
Ambient conditions Permitted operating range and any relevant restrictions.
Cable entries Entry thread, gland selection and compatibility with the equipment and cable.
Installation instructions Requirements for conductor termination, assembly and use.
Special conditions Any conditions for safe use identified in the certificate or accompanying documents.

If a quotation states Ex eb but the certificate or datasheet identifies a different protection level or configuration, request clarification before accepting the offer. Do not treat a generic statement of compliance as a substitute for checking the actual product documentation.

Inspection and Maintenance

Increased safety depends on equipment remaining in its assessed condition. During inspection, the relevant checks depend on the equipment type and the applicable inspection requirements.

Potential inspection points include:

  • Loose or damaged electrical connections.
  • Signs of overheating or discolouration.
  • Damaged insulation or evidence of contamination.
  • Incorrect conductor termination.
  • Changes to terminals or internal components.
  • Damaged enclosure parts or cable entries.
  • Equipment identification and marking.

Inspection and maintenance of installed Ex equipment are addressed by IEC 60079-17. The equipment protection requirements in IEC 60079-7 and the inspection requirements in IEC 60079-17 serve different purposes.

Replacing a terminal or internal component without checking the certified design can affect temperature performance, electrical separation or other characteristics. Use the manufacturer's instructions and applicable certification documentation to determine whether a proposed replacement or modification is acceptable.

Common Mistakes When Selecting Ex e Equipment

Assuming Ex eb and Ex ec are interchangeable

They represent different protection levels and requirements. Check the required EPL and complete marking before selecting equipment.

Checking only the enclosure IP rating

An IP rating describes ingress protection; it does not establish suitability for an explosive gas atmosphere.

Ignoring terminal loading

Terminal type, conductor size, current loading and the assessed equipment configuration must be compatible.

Assuming all equipment in the same product category is suitable

Two junction boxes or motors can have different protection concepts, EPLs, temperature limits and certification conditions.

Modifying internal components without verification

Changes to terminals, insulation or other components can affect the characteristics assessed for certification.

Related IEC 60079 Guides

References

This article is a practical introduction to Increased Safety protection. It does not reproduce IEC 60079-7 and does not replace the applicable standard edition, equipment certificate, manufacturer's instructions, project specification or national requirements. Confirm the applicable certification basis before making design, procurement, inspection or modification decisions.