What is the “X” in Ex Certificates?

Published 26 Jan 2021

What is the ‘X’ in Ex certificates, and why do you need to know?

Ex Certificates

Certifications For Equipment In Hazardous Areas

Special thanks to Tuomas Seilo Business Development Manager at 
Atexor for allowing T&D to republish this article

When it comes to equipment for Explosion Hazardous Areas, an ‘X’ in the Ex certification carries special meaning. In this article, Tuomas from Atexor explains the significance of ‘X’ (and ‘U’) in Ex certifications, why it is used, and how you should handle it.

The ‘X’ at the end of the certificate number in an ATEX or IECEx certification is a symbol indicating there is some specific condition(s) that should be taken into account when using the equipment in Ex areas.

The specific condition can be about installation, use or maintenance of the equipment. For example, the equipment might not have good protection against static electricity and therefore cannot be used where electrostatic charge build-up is common. The specific condition could be something like a specific torque for installation screws.

The specific condition could also be as simple, yet important, as how to clean the equipment, e.g. with a damp cloth and no solvents, which may damage the equipment.

In other cases, the special condition is not a limitation, but rather a clarification or additional information about how the equipment can be used.

How should you handle ‘X’?

Whenever you see the X-symbol in an Ex certificate, look for more information from the equipment manufacturer. The full certification document should be available with the product data. For equipment manufacturers and resellers, it is not enough to just supply the first page of the certification with the signatures.

The certificate, as well as the product manual, must include explanations of what the X conditions are. X in the certification number is by no means automatically bad thing, but hiding information about the specific conditions certainly is.

Equipment operators must get all the necessary information required to safely install, use and maintain equipment for Explosion Hazardous Areas. For equipment purchases, knowing the details of the special conditions is essential for ensuring the equipment satisfies all the purchase requirements.

A quick word about ‘U’

The letter ‘U’ is another symbol that appears in Ex certifications. However, this is only used for components and not ‘equipment’ or an ‘assembly’ as defined by the international set of standards under IEC/EN 60079.

A ‘U’ in an Ex certificate number means the item is certified as an Ex component, not Ex equipment. If you are purchasing or using Ex equipment, you should never see a ‘U’ in the certificate number.

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