Do Ex components with a U certificate carry the CE mark?

No. Under the ATEX directive 2014/34/EU, components are assessed by the same procedures as the equipment they are meant for, but they must not carry the CE marking and are not covered by an EU declaration of conformity. They are supplied with a written attestation of conformity that states their characteristics and how they must be built in. The CE marking goes on the finished equipment, after that equipment has had its own conformity assessment. A CE marking can appear on a component only when another EU law, such as the EMC Directive, requires it.

Short answer

• Legal basis: Article 13(3) of Directive 2014/34/EU applies the conformity procedures to components "with the exception of" the CE marking and the EU declaration of conformity, and requires a written attestation of conformity instead.
• What a component is: an item essential to the safe functioning of equipment or protective systems but with no autonomous function. Ex components in the harmonised standards, the items whose certificate number ends in U, are components in this sense.
• Typical examples given in the Commission's ATEX Guidelines: terminals, push-button assemblies, relays, empty flameproof enclosures, ballasts, encapsulated relays and contactors.
• Marking: the Ex hexagon with group and category is recommended where these can be assessed; a temperature class is normally not given. Where a notified body is involved in production control, the Guidelines say its identification number should be placed on the component, but without the CE marking.
• The equipment built from components needs its own conformity assessment, declaration and CE marking.

Why components cannot carry CE

The CE marking says that a product is ready for use and meets all the essential health and safety requirements. A component does not: its safety depends on how it is mounted, which enclosure surrounds it, how much heat it sees and what is connected to it. The Commission's ATEX Guidelines therefore compare the two directly:

The IEC standards say the same in their own language. IEC 60079-0 (the 2018 edition, as quoted in the Guidelines) defines an Ex component as equipment intended to be part of Ex equipment, not intended to be used alone and needing additional consideration when incorporated; the symbol "U" after the certificate number identifies it. The 2004 edition of IEC 60079-0 notes that the "X" symbol is not used for Ex components; the conditions for building them in are given in the component certificate and the manufacturer's documents.

What a buyer of components should receive

• A written attestation of conformity naming the component model, its characteristics and how it must be incorporated. The Guidelines accept that it can be made available through a web link or QR code on the packaging or delivery papers, because components are often supplied in large quantities.
• The component certificate (EU-type examination certificate with U, or IECEx certificate with U) where a notified body or certification body was involved. For an EU-type examination of a component, the certificate must state which Annex II requirements were assessed.
• Assembly instructions and the limits of use: for example permitted current, dissipated power, service temperatures or cross-sections for terminals, and free internal space or permitted openings for empty enclosures.

Common mistakes

• Expecting a declaration of conformity for a component. The correct document is the attestation of conformity.
• Treating a CE marking on a component as a quality sign. Unless another directive requires it, CE has no place on an ATEX component; ask the supplier why it is there.
• Installing a U-certified item on its own in a hazardous area. It is not complete equipment. The Guidelines note that a user who has to add parts such as an enclosure becomes a manufacturer.
• Assuming U certificates cover the assembly. The finished equipment still needs its own assessment, see does an assembly of ATEX parts need certification.

Related on excodex

• The ATEX Declaration of Conformity and the CE and Ex marking: what must be on the label
• The X and U suffixes on Ex certificates: specific conditions of use and Ex components
• Why does an Ex component have no temperature class?
• Is the CE mark alone enough to show equipment is ATEX compliant?
• Ex marking check: /tools/ex; standard space: ATEX 2014/34/EU

Standards and further reading

• Directive 2014/34/EU, Article 13(3) (components and the written attestation of conformity): legislation.gov.uk
• European Commission, ATEX 2014/34/EU Guidelines, 6th edition (January 2026), sections on components, the difference between equipment and components, the written attestation of conformity and the marking of components: webgate.ec.europa.eu
• IEC 60079-0, explosive atmospheres, general requirements (Ex component definition and marking); public text of the 2004 edition: law.resource.org

This article is general technical information prepared by the excodex editorial team. It does not replace the applicable standards, the equipment certificates and instructions, national regulations or the assessment of a competent person.