IEC 60079-26 Explained: Equipment with Separation Elements

Not every piece of explosion-protected equipment operates entirely within a single hazardous area classification. Some equipment can be installed across a boundary where different levels of protection are required on each side.

This creates a specific engineering problem: the equipment must maintain the appropriate explosion protection on both sides of the boundary while preventing the hazardous conditions on one side from compromising the protection required on the other.

IEC 60079-26 addresses this situation through requirements for equipment with separation elements and equipment using combined Equipment Protection Levels (EPLs).

The current edition is IEC 60079-26:2021, Edition 4.0. It specifies requirements for construction, testing and marking of Ex Equipment containing parts with different EPLs and a separation element. :contentReference[oaicite:1]{index=1}

The standard also addresses equipment mounted across boundaries between different hazardous areas and provides requirements for combining two types of protection, each having EPL Gb, to achieve EPL Ga. :contentReference[oaicite:2]{index=2}

Quick Answer

What Is IEC 60079-26?

IEC 60079-26 is part of the IEC 60079 series covering equipment for explosive atmospheres.

Its title is:

The standard provides requirements for equipment where different parts of the equipment require different levels of protection and where a separation element is used between those parts.

This arrangement can occur when equipment is mounted across a boundary between different hazardous areas.

IEC 60079-26 supplements and modifies the general requirements of IEC 60079-0. Where a requirement of IEC 60079-26 conflicts with a requirement of IEC 60079-0, the requirements of IEC 60079-26 take precedence. :contentReference[oaicite:3]{index=3}

Why Are Separation Elements Needed?

Different locations within an installation can have different hazardous-area classifications.

For example, one side of a physical boundary may require a higher EPL while the other side requires a different EPL.

If a single piece of equipment crosses that boundary, the equipment cannot simply be treated as though the entire product is located in one identical hazardous environment.

A separation element can be used to maintain the required separation between the different parts of the equipment.

The separation element therefore becomes an important part of the explosion protection design.

Equipment Across a Hazardous Area Boundary

One of the key applications of IEC 60079-26 is equipment mounted across a boundary where different EPLs are required.

The boundary can exist between:

• Different gas hazardous areas.
• Different dust hazardous areas.
• A gas hazardous area and a dust hazardous area.

IEC specifically identifies these boundary arrangements within the scope of IEC 60079-26:2021. :contentReference[oaicite:4]{index=4}

The equipment therefore has to maintain the required protection for the respective areas on each side of the boundary.

What Is an Equipment Protection Level?

An Equipment Protection Level (EPL) expresses the level of protection assigned to Ex equipment based on the likelihood of the equipment becoming an ignition source and the conditions under which that protection is intended to remain effective.

For gas atmospheres, the commonly encountered EPLs include:

• Ga
• Gb
• Gc

For combustible dust atmospheres, the corresponding EPLs include:

• Da
• Db
• Dc

The applicable EPL depends on the equipment, protection concept and hazardous-area requirements.

How Separation Elements Work

A separation element provides a defined boundary between portions of equipment that are subject to different protection requirements.

The purpose is not simply mechanical separation.

The separation element forms part of the explosion protection arrangement and has to satisfy the applicable construction and testing requirements.

The equipment is therefore assessed as an integrated system rather than as two unrelated products that happen to be installed next to each other.

Electrical and Non-Electrical Equipment

IEC 60079-26:2021 applies to both electrical and non-electrical equipment. :contentReference[oaicite:5]{index=5}

This is important because mechanical equipment can also create potential ignition sources.

Where mechanical energy can be transformed into a potential ignition source, IEC 60079-26 identifies the need for an ignition hazard assessment in accordance with ISO 80079-36 and appropriate measures where required. :contentReference[oaicite:6]{index=6}

Separation Between Different EPLs

A separation element can be required when different parts of equipment are assigned different EPLs.

The basic arrangement can be represented conceptually as:

The exact EPL combination depends on the application and the hazardous-area boundary.

The separation element must provide the required protection between the two portions of equipment.

Gas-to-Gas Boundaries

A separation element can be used when equipment crosses a boundary between different hazardous gas areas.

The different areas can require different EPLs because the likelihood of an explosive atmosphere being present is different.

The equipment therefore has to be designed so that the portion exposed to each area has the appropriate protection.

Dust-to-Dust Boundaries

IEC 60079-26 also addresses equipment crossing boundaries between different dust hazardous areas.

Dust atmospheres introduce different explosion protection considerations from gas atmospheres, including enclosure and surface-temperature considerations.

The separation arrangement must therefore be assessed against the applicable dust protection requirements.

Gas-to-Dust Boundaries

A particularly interesting application occurs when equipment crosses a boundary between a gas hazardous area and a dust hazardous area.

The two sides of the boundary can have different explosion protection requirements because the hazardous substances and classification systems are different.

IEC 60079-26 specifically identifies equipment mounted across boundaries between gas hazardous areas adjacent to dust hazardous areas within its scope. :contentReference[oaicite:7]{index=7}

Combined Levels of Protection

IEC 60079-26 is not limited to separation elements.

The 2021 edition also specifies requirements for combining two Types of Protection, each having EPL Gb, to achieve EPL Ga. :contentReference[oaicite:8]{index=8}

This is an important concept because EPL Ga represents a higher level of protection than EPL Gb.

Instead of relying on one standardized Type of Protection to achieve the required EPL Ga arrangement, the standard allows a defined combination of two protection types under its applicable requirements.

Why EPL Ga Is Important

EPL Ga is associated with equipment intended for explosive gas atmospheres where a very high level of protection is required.

Equipment assigned EPL Ga is intended to remain safe in the presence of an explosive atmosphere under the conditions defined by the applicable protection concept.

IEC 60079-26 provides a specific route for certain equipment designs where two protection types with EPL Gb can be combined to achieve EPL Ga. :contentReference[oaicite:9]{index=9}

Separation Elements and the Equipment Boundary

The physical boundary between two areas is an important part of the engineering assessment.

A separation element can involve a physical component or construction that separates different portions of equipment.

The separation element must maintain the required protection throughout the intended operating conditions.

This means the separation element cannot be evaluated solely as a structural component.

Its explosion protection function has to be considered as part of the certified equipment.

Construction Requirements

IEC 60079-26 establishes specific construction requirements for equipment within its scope.

These requirements supplement the general requirements of IEC 60079-0.

The construction has to account for:

• The different EPLs assigned to portions of the equipment.
• The separation element.
• The applicable Types of Protection.
• The hazardous-area boundary.
• The intended operating conditions.
• The equipment's electrical or mechanical characteristics.

The exact construction requirements depend on the equipment configuration and the protection arrangement.

Testing Requirements

IEC 60079-26 also specifies testing requirements for equipment covered by the standard.

Testing is necessary to demonstrate that the separation arrangement and combined protection concept can provide the required protection.

The assessment can involve the relevant characteristics of:

• The separation element.
• The protected equipment sections.
• The applicable Types of Protection.
• The interfaces between different protection levels.
• The complete equipment assembly.

The exact tests depend on the construction and protection arrangement.

Marking Requirements

Ex equipment covered by IEC 60079-26 must be appropriately marked.

The marking provides information needed to identify the certified protection arrangement.

Depending on the equipment, relevant information can include:

• Ex protection marking.
• Equipment Protection Level.
• Equipment group.
• Applicable Type or Types of Protection.
• Temperature classification where applicable.
• Ambient temperature range.
• Certificate information.
• Special conditions for safe use where applicable.

The complete marking should be interpreted together with the equipment certificate and manufacturer's documentation.

IEC 60079-26 and IEC 60079-0

IEC 60079-26 is a supplementary standard.

The general requirements are established by IEC 60079-0, while IEC 60079-26 adds requirements specific to equipment using separation elements or combined protection arrangements.

Standard	Role
IEC 60079-0	General requirements for Ex Equipment and Ex Components.
IEC 60079-26	Specific requirements for separation elements and certain combined EPL arrangements.

Where the requirements of the two standards conflict, IEC 60079-26 takes precedence for equipment within its scope. :contentReference[oaicite:10]{index=10}

IEC 60079-26 and Other Types of Protection

IEC 60079-26 does not replace the individual protection standards.

Instead, it works together with the applicable Type of Protection standards.

Protection	Primary Standard
Flameproof "d"	IEC 60079-1
Increased safety "e"	IEC 60079-7
Intrinsic safety "i"	IEC 60079-11
Encapsulation "m"	IEC 60079-18
Powder filling "q"	IEC 60079-5
Liquid immersion "o"	IEC 60079-6
Pressurization "p"	IEC 60079-2

Where an equipment design uses one or more of these protection concepts together with a separation element or a combined EPL arrangement, IEC 60079-26 may provide the additional requirements.

Mechanical Equipment

IEC 60079-26 is not restricted to electrical equipment.

The 2021 edition explicitly includes both electrical and non-electrical equipment. :contentReference[oaicite:11]{index=11}

For non-electrical equipment, mechanical movement can potentially generate an ignition source.

Where mechanical energy can be transformed into a potential ignition source, the standard identifies an additional ignition hazard assessment in accordance with ISO 80079-36. :contentReference[oaicite:12]{index=12}

This makes IEC 60079-26 relevant to a broader range of equipment than a purely electrical interpretation might suggest.

Application Example: Equipment Crossing a Zone Boundary

Consider equipment installed through a physical boundary between two hazardous areas with different EPL requirements.

One portion of the equipment is exposed to the conditions on one side of the boundary, while another portion is exposed to the conditions on the other side.

A separation element can be incorporated into the equipment to maintain the required protection between those portions.

The actual design, protection types and EPLs must be determined from the applicable equipment certification and hazardous-area requirements.

Application Example: Gas and Dust Boundary

A more complex application can occur where equipment crosses from an explosive gas atmosphere into a combustible dust atmosphere.

Gas and dust areas use different equipment groups and EPL designations.

The equipment therefore needs a protection arrangement appropriate to each environment.

IEC 60079-26 specifically recognizes this type of boundary application. :contentReference[oaicite:13]{index=13}

Engineering Considerations

When engineering equipment covered by IEC 60079-26, the following should be considered:

• Hazardous-area classification on each side of the boundary.
• Required EPL for each area.
• Location of the physical boundary.
• Type and function of the separation element.
• Protection concept used on each equipment section.
• Electrical and mechanical interfaces.
• Potential ignition sources.
• Mechanical ignition hazards where applicable.
• Temperature requirements.
• Environmental conditions.
• Equipment certification.
• Special conditions for safe use.

The final equipment should be evaluated as a complete certified assembly rather than as unrelated components.

Procurement Considerations

IEC 60079-26 can become particularly important during equipment procurement when a vendor proposes equipment that crosses a hazardous-area boundary.

A procurement review should verify:

• Applicable IEC 60079 standards.
• Complete Ex marking.
• EPL assigned to each relevant portion of equipment.
• Separation element arrangement.
• Applicable Type or Types of Protection.
• Equipment certificate.
• Installation requirements.
• Special conditions for safe use.
• Manufacturer's technical documentation.

A product should not be accepted simply because it carries an Ex marking. The marking and certification must demonstrate suitability for the actual boundary arrangement.

Inspection and Maintenance

Once installed, equipment using a separation element remains dependent on the integrity of its certified construction.

Inspection and maintenance should therefore consider the relevant parts of the equipment and any conditions that could compromise the separation arrangement.

Potential concerns include:

• Mechanical damage.
• Unauthorized modification.
• Damage to interfaces.
• Changes to cable or process connections.
• Damage to sealing arrangements where applicable.
• Evidence of overheating or abnormal operation.
• Changes that could affect the certified protection concept.

Maintenance should follow the manufacturer's instructions and the applicable inspection requirements of the IEC 60079 series.

Common Misunderstandings

IEC 60079-26 Is Only for EPL Ga

Not in the current edition. The 2021 edition specifically addresses equipment with separation elements or combined Levels of Protection and includes equipment with different EPLs. It also addresses certain combinations of two EPL Gb protection types to achieve EPL Ga. :contentReference[oaicite:14]{index=14}

A Separation Element Is Just a Physical Partition

Not necessarily. Within the context of IEC 60079-26, the separation element is part of the explosion protection arrangement and is subject to the applicable requirements.

Two EPL Gb Products Automatically Become EPL Ga

No. The combination must satisfy the specific requirements of IEC 60079-26.

IEC 60079-26 Applies Only to Electrical Equipment

No. The 2021 edition covers both electrical and non-electrical equipment. :contentReference[oaicite:15]{index=15}

IEC 60079-26 Replaces IEC 60079-0

No. IEC 60079-26 supplements and modifies IEC 60079-0 for equipment within its scope.

Any Equipment Can Be Installed Across a Hazardous-Area Boundary

No. Equipment crossing a boundary where different EPLs are required needs an appropriate certified protection arrangement.

Frequently Asked Questions

What is IEC 60079-26?

IEC 60079-26 is the IEC standard for Ex Equipment with separation elements or combined Levels of Protection.

What is a separation element in IEC 60079-26?

A separation element is part of an equipment arrangement used to separate portions of equipment having different Equipment Protection Levels where the applicable conditions require such separation.

Can IEC 60079-26 apply to equipment crossing a Zone boundary?

Yes. The standard specifically addresses equipment mounted across boundaries where different EPLs are required. :contentReference[oaicite:16]{index=16}

Does IEC 60079-26 cover gas and dust boundaries?

Yes. The scope includes equipment mounted across boundaries between different gas hazardous areas, different dust hazardous areas, and gas hazardous areas adjacent to dust hazardous areas. :contentReference[oaicite:17]{index=17}

Does IEC 60079-26 cover non-electrical equipment?

Yes. The current edition covers both electrical and non-electrical equipment. :contentReference[oaicite:18]{index=18}

Can two EPL Gb protection types achieve EPL Ga?

IEC 60079-26 specifies requirements for combining two Types of Protection, each with EPL Gb, to achieve EPL Ga. This is not an automatic conversion and must comply with the standard's requirements. :contentReference[oaicite:19]{index=19}

What standard works with IEC 60079-26?

IEC 60079-26 supplements IEC 60079-0 and can be used together with the applicable Type of Protection standards depending on the equipment design.

What is the current edition of IEC 60079-26?

The current edition listed by IEC is IEC 60079-26:2021, Edition 4.0. IEC lists a stability date of 2027. :contentReference[oaicite:20]{index=20}

Conclusion

IEC 60079-26 addresses a specialized but important engineering problem: Ex equipment that must operate across boundaries where different levels of protection are required.

The standard provides requirements for equipment containing parts with different EPLs and a separation element, including applications involving gas-to-gas, dust-to-dust and gas-to-dust hazardous-area boundaries. :contentReference[oaicite:21]{index=21}

It also addresses a specific combined-protection arrangement where two Types of Protection, each with EPL Gb, can be combined to achieve EPL Ga under the requirements of the standard. :contentReference[oaicite:22]{index=22}

For engineers and procurement teams, the important point is that the separation element and the different equipment sections cannot be evaluated independently from the overall certified design.

IEC 60079-26 treats the boundary, separation arrangement, protection concepts and EPL requirements as part of one engineered Ex equipment solution.

Technical Review

References

• IEC 60079-26:2021 – Explosive atmospheres – Part 26: Equipment with Separation Elements or combined Levels of Protection.
• IEC 60079-0:2026 – Explosive atmospheres – Part 0: Equipment – General requirements.
• IEC 60079-1 – Explosive atmospheres – Part 1: Equipment protection by flameproof enclosures "d".
• IEC 60079-5 – Explosive atmospheres – Part 5: Equipment protection by powder filling "q".
• IEC 60079-6 – Explosive atmospheres – Part 6: Equipment protection by liquid immersion "o".
• IEC 60079-7 – Explosive atmospheres – Part 7: Equipment protection by increased safety "e".
• IEC 60079-11 – Explosive atmospheres – Part 11: Equipment protection by intrinsic safety "i".
• IEC 60079-18 – Explosive atmospheres – Part 18: Equipment protection by encapsulation "m".
• ISO 80079-36 – Explosive atmospheres – Part 36: Non-electrical equipment for explosive atmospheres – Basic method and requirements.