How do I read an Ex certificate number such as 'ABC 12ATEX1234X' or 'IECEx ABC 12.0034U'?

Read it from left to right: scheme, issuer, year, serial number, suffix. In IECEx ABC 12.0034U, "IECEx" is the scheme, "ABC" stands for the certification body that issued it, "12" means 2012, "0034" is the certificate's serial number for that year and "U" marks an Ex component. In ABC 12ATEX1234X the word ATEX takes the place of the full stop, and "X" means the certificate contains specific conditions of use.

Short answer

• Scheme: IECEx at the front for the international IECEx scheme; by common notified body practice, the word ATEX between year and serial number for an EU-type examination certificate under the ATEX directive (the directive itself does not prescribe a number format).
• Issuer code: letters that identify the certification body that issued the certificate. It is not the four-digit notified body number printed next to the CE mark.
• Year: the last two digits of the year the certificate was issued, not the year the equipment was built.
• Serial number: the running number of that issuer's certificates in that year.
• Suffix: X for specific conditions of use, U for an Ex component, nothing for plain equipment. X and U are never used together.
• Issue number: changes are published as new issues (IECEx) or additions to the original certificate (ATEX); these are shown on the certificate, not in the number on the label.

The parts, one by one

IEC 60079-0 requires the marking to include the name or mark of the certificate issuer and a certificate reference made of the last two figures of the year of the certificate followed by its serial number in that year. An X goes after the reference when special conditions for safe use apply, and a U marks an Ex component. The IECEx scheme explains its own format the same way: IECEx XXX 18.0001 means an IECEx certificate from the body with code XXX, issued in 2018, number 0001 of that year.

Spacing varies: ABC 12 ATEX 1234 X and ABC12ATEX1234X are the same number.

What the number does not tell you

• It is not a production date. A certificate issued in 2012 can cover equipment built in 2026. The year of construction is a separate item of the ATEX marking.
• It does not show which edition of a standard applies. That is listed on the certificate. The IECEx scheme notes that a new edition of a standard does not by itself invalidate an existing certificate; manufacturers may have it re-issued against the newer edition.
• It does not show the current issue. IECEx certificates are "living" documents with issue numbers (0, 1, 2 and so on); each up-issue describes what changed in a "details of certificate changes" section, and a new issue does not cancel the earlier ones. Under ATEX, a modification of the approved type is approved as an addition to the original EU-type examination certificate, often called a supplement or variation. Conditions, variants and ambient ranges can change between issues.
• It is not the notified body number. Under ATEX the four-digit identification number next to the CE mark belongs to the body involved in production control (quality assurance or product verification). That can be a different body from the one that issued the EU-type examination certificate.

Checking a number you have been given

1. IECEx: search the IECEx online certificate system. The online version is the controlled master copy. IECEx states that a certificate not found there does not exist, and the status field shows Current, Suspended or Cancelled.
2. ATEX: there is no single public database of EU-type examination certificates. Ask the manufacturer for the full certificate with all supplements and, if in doubt, confirm it with the issuing notified body.
3. Compare the type, variants, marking and ambient range on the certificate with the nameplate.

Common mistakes

• Reading the year as the age of the product. It is the age of the certificate.
• Treating the issuer code as the notified body number. They are different identifiers.
• Checking an old PDF instead of the current issue. Downloaded copies are uncontrolled; the status can change.
• Ignoring the suffix. An X means you must read the conditions; a U means the item cannot be installed on its own.

Related on excodex

• The X and U suffixes on Ex certificates: specific conditions of use and Ex components
• The IECEx scheme explained: CoC, ExTR, QAR and the online certificate database
• How to verify that an Ex certificate is genuine
• What does the U suffix mean on an Ex certificate?
• Standards: IECEx, ATEX 2014/34/EU

Standards and further reading

• IEC 60079-0, general requirements: marking of the certificate issuer, certificate reference, X and U (edition 8, 2026); format paraphrased from the public 2004 edition: law.resource.org (PDF)
• IECEx, FAQs from Ex equipment manufacturers, purchasers and users (certificate number format, issues, status, online master copy): iecex.com
• US Coast Guard OCS National Center of Expertise, Drill Down 29 on hazardous location certificate numbers: dco.uscg.mil
• European Commission, ATEX 2014/34/EU Guidelines, 6th edition (January 2026), CE marking and notified body numbers: single-market-economy.ec.europa.eu (PDF)

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.