IEC 60079-5 Explained: Powder Filling “q” Protection

Some explosion-protected electrical equipment cannot rely on a conventional enclosure alone to prevent ignition. One protection technique is to surround the protected components with a suitable filling material so that an explosive atmosphere cannot interact with the ignition sources in the protected space.

This protection concept is known as powder filling “q”, and its specific requirements are defined by IEC 60079-5.

IEC 60079-5 specifies requirements for the construction, testing, and marking of electrical equipment, parts of electrical equipment, and Ex components using the type of protection powder filling “q”. It is intended for equipment used in explosive gas atmospheres.

The standard works together with IEC 60079-0, which provides the general requirements for Ex equipment. IEC 60079-5 adds and modifies those requirements for the particular characteristics of powder-filled equipment.

For engineers, manufacturers, certification professionals, inspectors, and procurement teams, understanding IEC 60079-5 is important because the protection principle is based on the properties, arrangement, and integrity of the filling material inside the protected equipment.

This article explains what IEC 60079-5 is, how Ex q protection works, what the standard covers, and what engineers should understand when reviewing powder-filled Ex equipment.

Quick Answer

What Is IEC 60079-5?

IEC 60079-5 is the international standard titled Explosive Atmospheres – Part 5: Equipment Protection by Powder Filling “q”.

The standard defines specific requirements for equipment that uses powder filling as its explosion protection technique.

The basic principle is to use a suitable filling material within the protected equipment so that the electrical components and potential ignition sources are isolated from the surrounding explosive atmosphere in accordance with the requirements of the protection concept.

The standard applies to electrical equipment, parts of electrical equipment, and Ex components using powder filling “q”.

IEC 60079-5 does not replace IEC 60079-0. Instead, it supplements and modifies the general requirements of IEC 60079-0 for equipment using powder filling protection.

Why Is IEC 60079-5 Important?

Electrical equipment used in hazardous areas can contain components capable of producing sparks, arcs, or elevated temperatures. A protection technique therefore has to prevent those potential ignition sources from igniting the surrounding explosive atmosphere.

Powder filling takes a different approach from flameproof protection, intrinsic safety, or increased safety.

Instead of relying primarily on a flameproof enclosure, limiting electrical energy, or preventing ignition sources through increased safety construction, the protected components are embedded or surrounded by an appropriate filling material in accordance with the certified design.

The filling material and the construction of the equipment are therefore fundamental parts of the protection system.

IEC 60079-5 establishes the requirements necessary to assess those characteristics consistently.

How Does Ex q Protection Work?

The fundamental principle of Ex q protection is the use of a filling material to surround the protected electrical components.

The filling material forms part of the protection system and creates a physical environment around the protected components that limits the possibility of an explosive atmosphere reaching a potential ignition source in a hazardous manner.

The effectiveness of the protection depends on the construction of the equipment and the properties and arrangement of the filling material.

This means that the filling material cannot simply be treated as an ordinary packing material added to an electrical enclosure. Its role is directly connected to the certified explosion protection method.

IEC 60079-5 and IEC 60079-0

IEC 60079-5 should be understood together with IEC 60079-0.

IEC 60079-0 establishes the general requirements applicable to Ex equipment, while IEC 60079-5 provides additional requirements specific to powder filling protection.

Standard	Role
IEC 60079-0	General requirements for Ex equipment and Ex components.
IEC 60079-5	Specific requirements for equipment protection by powder filling “q”.

The relationship is similar to the way IEC 60079-0 works with other protection standards such as IEC 60079-1 for Ex d, IEC 60079-7 for Ex e, and IEC 60079-11 for Ex i.

The general requirements establish the common framework, while the protection-specific standard addresses the characteristics of the particular protection technique.

Scope of IEC 60079-5

IEC 60079-5 applies to electrical equipment, parts of electrical equipment, and Ex components using powder filling “q” and intended for use in explosive gas atmospheres.

The current consolidated edition specifies applicability to equipment with:

• Rated supply current of 16 A or less.
• Rated supply voltage of 1,000 V or less.
• Rated power consumption of 1,000 W or less.

These limits are part of the scope of the standard and should be checked against the actual equipment being assessed.

What Equipment Can Use Ex q Protection?

Powder filling can be used for electrical equipment and Ex components where the design is suitable for this type of protection.

The protection concept is particularly relevant to compact electrical assemblies and components where the protected parts can be incorporated into a controlled powder-filled construction.

Examples can include equipment containing:

• Electrical components.
• Electronic circuits.
• Components capable of producing electrical arcs or sparks.
• Components requiring separation from the surrounding explosive atmosphere.
• Cells or batteries where the certified construction permits their use.

The exact equipment types and configurations depend on the certified design and the applicable requirements of IEC 60079-5.

Powder Filling Material

The filling material is one of the most important elements of Ex q protection.

The material has to provide the characteristics required by the protection concept and the certified construction.

The filling material therefore cannot be selected simply because it appears physically suitable for filling an enclosure.

Its properties, arrangement, quantity, and relationship with the protected components form part of the equipment design assessed for certification.

This is one reason why Ex q equipment should be treated as a certified assembly rather than as an ordinary enclosure that can be opened and refilled with an alternative material.

Construction Requirements

IEC 60079-5 establishes specific construction requirements for equipment using powder filling protection.

The construction has to ensure that the filling material remains in the intended location and that the protective characteristics of the equipment are maintained.

Important design considerations include:

• Arrangement of the protected components.
• Position and distribution of the filling material.
• Integrity of the enclosure or container.
• Protection against movement or loss of filling material.
• Electrical connections and external interfaces.
• Mechanical integrity of the finished assembly.
• Thermal conditions within the filled equipment.

The exact requirements depend on the equipment construction and the applicable clauses of the standard.

Filling and Enclosure Integrity

The effectiveness of powder filling depends on maintaining the intended physical arrangement of the filling material.

If the material can move, escape, settle in an unintended way, or otherwise change its certified configuration, the protective characteristics of the equipment may be affected.

The enclosure or container therefore has an important role in retaining the filling material and maintaining the certified construction.

This is particularly relevant during transportation, installation, maintenance, and service because mechanical damage can potentially affect the integrity of the protected assembly.

Thermal Considerations

Electrical components inside powder-filled equipment still generate heat during operation.

The thermal characteristics of the filling material and the equipment construction therefore have to be considered during design and testing.

Temperature is important in explosion protection because a surface or component that becomes excessively hot can potentially become an ignition source.

The certified design therefore has to account for the thermal behaviour of the equipment under its intended operating conditions.

Electrical Connections

Electrical connections form an important part of any Ex equipment design, including equipment using powder filling protection.

IEC 60079-5 contains requirements related to the construction of the protected equipment and its external connections.

The connection arrangement must be compatible with the certified design and the applicable requirements of the standard.

When equipment is installed in the field, engineers should therefore follow the manufacturer's certified installation instructions rather than treating external connections as ordinary electrical terminations.

Testing of Ex q Equipment

IEC 60079-5 includes specific testing requirements used to assess whether powder-filled equipment meets the requirements of the protection concept.

Testing forms an important part of the certification process because the protection cannot be established simply from the appearance of the finished equipment.

Depending on the equipment design, the assessment can involve verification of characteristics associated with:

• Construction.
• Filling material.
• Electrical characteristics.
• Temperature behaviour.
• Mechanical integrity.
• Enclosure or filling containment.
• Marking and documentation.

Additional requirements can apply depending on the particular equipment and construction.

Marking Requirements

Ex equipment marking provides users with information about the certified protection method and the equipment's intended application.

For equipment using powder filling, the protection concept is identified by the “q” designation within the Ex marking.

The complete marking can also communicate other information required by the applicable standards, such as:

• Equipment group.
• Equipment Protection Level.
• Gas group.
• Temperature classification where applicable.
• Ambient temperature limitations.
• Certificate identification.
• Special conditions for safe use where applicable.

The complete marking should always be evaluated rather than selecting equipment based only on the presence of “Ex q”.

Ex q and Hazardous Area Classification

The use of Ex q equipment still depends on the hazardous-area classification and the certified characteristics of the equipment.

The presence of an Ex q marking does not by itself mean that the equipment is suitable for every hazardous area.

Engineers should consider:

• Hazardous area Zone.
• Gas group.
• Equipment Protection Level.
• Temperature classification where applicable.
• Ambient temperature.
• Equipment certification.
• Special conditions for safe use.

Hazardous-area classification is addressed separately within the IEC 60079 series, including IEC 60079-10-1 for explosive gas atmospheres.

Ex q Compared With Other Protection Concepts

Powder filling is one of several protection techniques within the IEC 60079 series.

Protection	Basic Principle	Standard
Ex d	Uses a flameproof enclosure to contain an internal explosion and prevent flame transmission.	IEC 60079-1
Ex e	Uses increased safety design to prevent ignition sources under specified conditions.	IEC 60079-7
Ex i	Limits electrical and thermal energy to prevent ignition.	IEC 60079-11
Ex p	Uses a controlled protective atmosphere within an enclosure.	IEC 60079-2
Ex q	Uses powder filling as the protection technique.	IEC 60079-5
Ex o	Uses liquid immersion as the protection technique.	IEC 60079-6
Ex m	Uses encapsulation to prevent an explosive atmosphere from reaching protected ignition sources.	IEC 60079-18

The correct protection concept depends on the equipment design, application, hazardous-area requirements, and certification basis.

Advantages of Ex q Protection

Powder filling provides a distinct method of protecting electrical components in explosive gas atmospheres.

Potential advantages of the technique include:

• Provides physical separation between protected components and the surrounding atmosphere.
• Can be applied to compact electrical assemblies and components.
• Can protect components that may otherwise present ignition sources.
• Provides a defined protection method that can be assessed through standardized testing.
• Can complement other Ex protection techniques within a wider equipment design.

The practical value of Ex q depends on whether the equipment can be designed and certified effectively using powder filling.

Limitations of Ex q Protection

Powder filling also creates design and maintenance considerations that should not be overlooked.

The protection depends on the integrity of the filling arrangement and the certified construction.

Potential considerations include:

• Filling material must remain consistent with the certified design.
• The filling arrangement must not be disturbed without following the manufacturer's requirements.
• Damage to the enclosure or container can affect the protection.
• Thermal behaviour must be considered.
• Maintenance and repair must preserve the certified construction.
• Field modifications may affect the certification basis.

For these reasons, Ex q equipment should not be treated like an ordinary electrical enclosure that can be freely modified in the field.

Ex q Equipment in Engineering and Procurement

When Ex q equipment is specified or procured, the equipment should be evaluated against the complete project requirements.

A technical review should consider:

• Applicable IEC 60079 standards.
• Ex marking.
• Equipment Protection Level.
• Gas group.
• Temperature classification where applicable.
• Ambient temperature range.
• Equipment certificate.
• Manufacturer's instructions.
• Special conditions for safe use.
• Rated electrical characteristics.

The rated current, voltage, and power limits specified by IEC 60079-5 should also be checked against the actual equipment.

This is particularly important when reviewing equipment with batteries, electronic circuits, or other internal components that form part of the powder-filled assembly.

Maintenance and Modification of Ex q Equipment

Because the filling material forms part of the explosion protection method, maintenance of Ex q equipment requires particular care.

Opening, removing, replacing, or disturbing the filling material can potentially change the certified construction.

Likewise, replacing an internal component with a different component can affect the thermal, electrical, or physical characteristics of the certified assembly.

Maintenance should therefore be performed in accordance with the manufacturer's instructions and the applicable certification requirements.

Where repair or modification is required, the certification basis should be considered before work is carried out.

Common Misunderstandings About IEC 60079-5

Ex q Means the Equipment Is Filled With Any Powder

No. The filling material forms part of the certified protection concept. Its characteristics and arrangement have to be compatible with the applicable requirements and certified design.

Ex q Is the Same as Ex t for Dust

No. Ex q and Ex t are different protection concepts. IEC 60079-5 addresses powder filling for equipment intended for explosive gas atmospheres, while IEC 60079-31 addresses protection by enclosure “t” for explosive dust atmospheres.

IEC 60079-5 Replaces IEC 60079-0

No. IEC 60079-5 supplements and modifies the general requirements of IEC 60079-0 for equipment using powder filling protection.

Ex q Equipment Can Be Refilled With Another Material

Not automatically. The filling material and its arrangement form part of the certified construction. Any replacement must follow the applicable manufacturer and certification requirements.

Ex q Automatically Means the Equipment Can Be Used in Any Zone

No. The complete Ex marking, EPL, gas group, certification, ambient conditions, and hazardous-area classification must be compatible with the intended application.

IEC 60079-5 Applies to Combustible Dust

Not as its primary scope. The current IEC 60079-5 scope covers powder-filled equipment intended for explosive gas atmospheres.

Frequently Asked Questions (FAQ)

What is IEC 60079-5?

IEC 60079-5 is the standard for equipment protection by powder filling “q”. It specifies requirements for the construction, testing, and marking of electrical equipment, parts of electrical equipment, and Ex components using powder filling in explosive gas atmospheres.

What does Ex q mean?

Ex q identifies the powder filling type of explosion protection. The protection uses a suitable filling material as part of the certified equipment construction to protect the relevant electrical components from the surrounding explosive atmosphere.

What is the current edition of IEC 60079-5?

The current consolidated version is IEC 60079-5:2015+AMD1:2022, identified by IEC as Edition 4.1.

Does IEC 60079-5 apply to dust atmospheres?

The current standard specifies its scope for electrical equipment, parts of equipment, and Ex components using powder filling “q” intended for use in explosive gas atmospheres.

What is the difference between Ex q and Ex p?

Ex q uses powder filling as the protection technique, while Ex p uses a pressurized enclosure and a controlled protective atmosphere. They are covered by different standards: IEC 60079-5 for Ex q and IEC 60079-2 for Ex p.

Does Ex q use IEC 60079-0?

Yes. IEC 60079-5 supplements and modifies the general requirements of IEC 60079-0 for equipment using powder filling protection.

Can Ex q equipment be modified in the field?

Modifications require careful evaluation because the filling material, internal components, and construction can form part of the certified protection system. Manufacturer instructions and applicable certification requirements should be followed.

What electrical limits are specified by IEC 60079-5?

The current consolidated edition specifies applicability to equipment with a rated supply current of up to 16 A, rated supply voltage up to 1,000 V, and rated power consumption up to 1,000 W.

Conclusion

IEC 60079-5 provides the specific requirements for equipment protection by powder filling “q”.

The protection concept uses a suitable filling material as part of the certified equipment construction, providing a controlled physical environment around the protected electrical components.

Because the filling material, internal components, enclosure construction, and electrical characteristics can all form part of the protection system, Ex q equipment should be treated as a certified assembly rather than an ordinary enclosure that can be freely modified.

IEC 60079-5 works together with IEC 60079-0 and must be considered alongside the complete Ex marking, equipment certification, hazardous-area classification, and manufacturer's instructions.

For engineers and procurement teams, the key point is simple: Ex q protection depends on the certified powder-filled construction, not simply on the presence of a filling material inside an electrical enclosure.

Technical Review

References

• IEC 60079-5:2015+AMD1:2022 – Explosive Atmospheres – Part 5: Equipment Protection by Powder Filling “q”.
• IEC 60079-0 – Explosive Atmospheres – Part 0: Equipment – General Requirements.
• IEC 60079-1 – Explosive Atmospheres – Part 1: Equipment Protection by Flameproof Enclosures “d”.
• IEC 60079-2 – Explosive Atmospheres – Part 2: Equipment Protection by Pressurized Enclosure “p”.
• 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 Series – Explosive Atmospheres.
• IECEx System – International Certification System for Equipment Used in Explosive Atmospheres.