ATEX, IECEX, COMPEX
ATEX vs IECEx vs CompEx: What Each One Means
ATEX, IECEx and CompEx are often mixed up. One is European law, one is an international certification system, one is a personnel competence scheme. Here is what each covers, how zones map to NEC classes and divisions, and which one you need.
ATEX is European Union law that sets the rules for equipment used in explosive atmospheres and for protecting the workers around it; IECEx is the IEC's international certification system for Ex equipment, repair workshops and people; and CompEx is a certification scheme that proves an individual technician or engineer is competent to work on Ex equipment. In short, ATEX tells you what is legally required in Europe, IECEx certifies products and people against IEC 60079 worldwide, and CompEx certifies only people.
Checked on 11 October 2026 against the sources listed under this post.
The three names turn up side by side in job adverts, equipment datasheets and site inductions, which is why they are so often confused. This guide explains each one using the primary sources: the European Commission's ATEX page, the IECEx site and CompEx Certification. It also shows how the zone system lines up with the classes and divisions used in North America.
What is ATEX?
ATEX is the name given to two European Union directives about explosive atmospheres ("ATEX" comes from the French atmosphères explosibles).
- Directive 2014/34/EU, the equipment directive. The European Commission says it "covers equipment and protective systems intended for use in potentially explosive atmospheres". It has been applicable since 20 April 2016 and replaced Directive 94/9/EC. It is aimed at manufacturers: a product must pass the right conformity assessment before it can be placed on the EU market.
- Directive 1999/92/EC, the workplace directive. It sets "minimum requirements for improving the level of health and safety protection of workers" who may be at risk from explosive atmospheres. It is aimed at employers, who must classify areas into zones, assess the risk and choose suitable equipment.
In Great Britain, the UK Health and Safety Executive explains that the workplace directive is implemented through DSEAR (the Dangerous Substances and Explosive Atmospheres Regulations 2002) and the equipment directive through the Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 2016, which HSE says "apply to all equipment intended for use in explosive atmospheres being placed on the GB market".
What ATEX does not have is a personnel certificate. The workplace directive expects employers to use competent people, but it does not create a card or qualification for technicians. That gap is what IECEx personnel certification and CompEx fill.
What is IECEx?
IECEx is "the IEC System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres", run under the International Electrotechnical Commission. It certifies against the IEC 60079 and IEC 80079 series, and it is voluntary: it carries legal force in a country only where that country's regulator chooses to accept or require it. The IECEx home page lists four schemes:
| IECEx scheme | What it certifies | Typical holder |
|---|---|---|
| Certified Equipment Scheme | Ex equipment, through a test report and certificate of conformity | Manufacturers |
| Certified Service Facility Scheme | Workshops that repair, overhaul or inspect Ex equipment | Repair and service companies |
| Conformity Mark Licensing System | Use of the IECEx mark on certified products | Manufacturers |
| Certified Persons Scheme (CoPC) | An individual's competence, unit by unit | Technicians, inspectors, designers |
The IECEx Certificate of Personnel Competence
The personnel scheme is the one that matters for comparing with CompEx. IECEx says it "provides the means for an individual working in, or associated with, hazardous areas to obtain a Certificate of Personnel Competence (CoPC)", and that it is "a verification by assessment, by an independent organization". An IECEx approved certification body assesses you against one or more units, and the certificate is then published on the IECEx online system where anyone can check it.
The IECEx personnel scheme page lists twelve units of competence, Ex 000 to Ex 011:
- Ex 000 basic knowledge and awareness to enter a site with a classified hazardous area
- Ex 001 basic principles of protection in explosive atmospheres
- Ex 002 classifying hazardous areas
- Ex 003 installing explosion-protected equipment and wiring
- Ex 004 maintaining equipment in explosive atmospheres
- Ex 005 overhauling and repairing explosion-protected equipment
- Ex 006 to Ex 008 testing, visual and close inspection, and detailed inspection
- Ex 009 designing installations
- Ex 010 audit inspection
- Ex 011 basic knowledge of hydrogen system safety
IECEx states that "the Ex expert is re-assessed every 5 years to maintain their CoPC."
In this short lesson, BARTEC walks through the regulators, standards and certifying bodies in explosion protection, which is exactly the map this post draws. It comes from our free Hazardous Areas: Ex Equipment, Zones and Inspection course, where it sits beside lessons on protection concepts, marking strings and IEC 60079-14 inspection.
What is CompEx?
CompEx is a personnel certification scheme for people who install, inspect, maintain or design equipment in explosive atmospheres. CompEx Certification describes it as "a globally recognised certification scheme that validates the competency of individuals" in hazardous atmospheres, and says it is "accredited to ISO/IEC 17024 and based on IEC 60079 and related standards". CompEx personnel certification appears on the UKAS schedule of accreditation 0270, the UK's national accreditation body.
The best-known qualification is the core gas and vapour course, units Ex01 to Ex04:
| CompEx unit | Activity | Protection concepts |
|---|---|---|
| Ex01 | Prepare and install | Ex d, Ex e, Ex n, Ex p |
| Ex02 | Inspect and maintain | Ex d, Ex e, Ex n, Ex p |
| Ex03 | Prepare and install | Ex i (intrinsic safety) |
| Ex04 | Inspect and maintain | Ex i (intrinsic safety) |
Around that core, the scheme offers dust units, design and mechanical units, an awareness level and a foundation level. CompEx says its certificates "are valid for five years" and must be renewed before they expire; a recognised practitioner route exists for renewal. Assessment combines theory papers with practical tasks on real equipment in an approved centre, so it cannot be completed by reading alone.
CompEx vs IECEx: which personnel certificate should you get?
Both schemes test the same body of knowledge, IEC 60079 installation, inspection and maintenance, and both use practical assessment. The differences are in who runs them and who asks for them.
- Structure. IECEx issues a separate CoPC for each unit you pass, from Ex 000 to Ex 011. CompEx groups tasks into its own units, such as the Ex01 to Ex04 core.
- Who asks for it. In practice, employers and project specifications decide which personnel scheme they accept. Some name CompEx, some name the IECEx CoPC, and some accept either or an equivalent.
- What it does not do. Neither certificate is a licence to work. Your employer still has to judge you competent for the job, issue permits and supervise as their own procedures require.
The practical rule is to read the specification for the job or site you want. If it names one scheme, get that one. If it says "CompEx or equivalent", ask what they accept as equivalent before you book.
How do zones compare with classes and divisions?
Europe and IEC countries classify hazardous areas into zones: Zone 0, 1 and 2 for gas and vapour, and Zone 20, 21 and 22 for combustible dust, graded by how often and how long an explosive atmosphere is present. North America traditionally uses classes and divisions (Class I gas, Class II dust, Class III fibres; Division 1 or Division 2), defined in the National Electrical Code (NEC, NFPA 70) Article 500, with the zone system in Articles 505 and 506.
US federal law allows both. OSHA's 29 CFR 1910.307 says "Employers may use the zone classification system as an alternative to the division classification system", and lists Class I, Zone 0, 1 and 2 designations.
The mapping is approximate, not exact. Equipment certified for one system is not automatically acceptable in the other, so check the marking string and the local code. Our IP rating chart explains how ingress protection codes, which also appear on Ex equipment labels, differ from Ex protection.
Which one do you actually need?
It depends on whether you are dealing with a product, a place or a person.
| Your situation | What applies |
|---|---|
| Selling Ex equipment into the EU | ATEX equipment directive conformity (and the GB equivalent for Great Britain) |
| Selling Ex equipment worldwide | Often IECEx certification as well, accepted or required by many national regulators |
| Running a plant with explosive atmospheres in Europe | ATEX workplace directive (DSEAR in Great Britain): zoning, risk assessment, competent people |
| Running a US plant | OSHA 1910.307 and the NEC, with divisions or zones |
| Technician applying for Ex work | Usually CompEx or an IECEx CoPC, whichever the employer names |
| Repair workshop | IECEx Certified Service Facility, where customers ask for it |
For control and instrument engineers, hazardous areas meet process safety and safety instrumented systems at the same sites. Our posts on oil and gas automation and safety PLCs, SIL and SIS cover those layers.
How to prepare before a CompEx or IECEx assessment
A five-day CompEx course moves quickly. Candidates who already understand the fire triangle, gas groups, temperature classes, protection concepts and marking strings spend their course time on the practical tasks instead of the basics. You can build that background at no cost:
- Hazardous Areas: Ex Equipment, Zones and Inspection covers area classification, gas groups and T-classes, every protection concept from Ex d to Ex t, IEC 60079-14 installation, and inspection grades.
- HAZOP and Process Safety Management explains where explosive atmospheres come from in the first place and how process hazards are studied.
- Electrical Safety: Arc Flash, NFPA 70E and LOTO covers isolation and safe work practice that every Ex task depends on.
If an employer asks how to check a training certificate, our guide to verifying engineering training certificates explains what to look for, including on CompEx and IECEx records.
Every course is free in full. An optional EDWartens Certificate of Completion, from US$8.99, records that you finished the course. It is not a CompEx or IECEx certificate, is not ATEX approval and is not accredited; anyone can verify it at edwartens.com/verification.
Take the free course
Questions
Is CompEx the same as IECEx?
No. CompEx is a personnel certification scheme run by CompEx Certification Limited and accredited to ISO/IEC 17024. IECEx is the IEC's certification system, which covers equipment, service facilities and, through its Certified Persons Scheme, individual competence. Both assess people against IEC 60079 knowledge, but they are separate schemes with separate certificates.
Is ATEX the same as IECEx?
No. ATEX is European Union law: Directive 2014/34/EU covers equipment placed on the EU market and Directive 1999/92/EC covers worker protection. IECEx is a voluntary international certification system. Many manufacturers hold both an ATEX certificate and an IECEx certificate of conformity for the same product because each answers a different market.
How long is a CompEx certificate valid?
CompEx says its certificates are valid for five years and that holders must re-certify before they expire. The IECEx Certified Persons Scheme also re-assesses each person every five years to keep their Certificate of Personnel Competence. Always check the expiry date printed on the certificate itself.
Do I need CompEx to work in a hazardous area in the US?
No US law requires CompEx. US hazardous locations follow OSHA 29 CFR 1910.307 and the National Electrical Code, which use classes and divisions with zones as an alternative. Some employers, especially international oil and gas operators, still ask for CompEx or an IECEx CoPC as their own competence requirement, so read the job specification.
What do CompEx units Ex01 to Ex04 cover?
Ex01 to Ex04 are the core gas and vapour units. Ex01 and Ex03 cover preparing and installing protected equipment (Ex d, e, n, p in Ex01; intrinsically safe Ex i in Ex03). Ex02 and Ex04 cover inspecting and maintaining the same equipment. Dust, design and mechanical units sit beside them in the wider scheme.
Does a free online course make me CompEx or IECEx certified?
No. Only CompEx Certification Limited, through its approved centres, issues CompEx certificates, and only an IECEx approved certification body issues a Certificate of Personnel Competence. A free course can build the background knowledge both assessments expect, but its certificate of completion is not either credential.
Sources
- European Commission: Equipment for potentially explosive atmospheres (ATEX) (read 11 October 2026)
- HSE: ATEX and explosive atmospheres (read 11 October 2026)
- IECEx: home page and list of schemes (read 11 October 2026)
- IECEx: Introduction to the IECEx Personnel Competency Scheme (read 11 October 2026)
- CompEx Certification: About the CompEx scheme (read 11 October 2026)
- UKAS: schedule of accreditation 0270, personnel certification (read 11 October 2026)
- OSHA: 29 CFR 1910.307, Hazardous (classified) locations (read 11 October 2026)
Written by the EDWartens engineering team for general education. Product names are trademarks of their owners; mentioning them does not imply endorsement. Prices and terms of other providers were checked on the date shown and can change.
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