ATEX compliance is one of the most consistently misunderstood areas of project quality in the oil and gas, chemical, offshore and energy sectors. At one end, teams underestimate what it involves — assuming that "ATEX certified" stamped on a datasheet means a piece of equipment is ready to install. At the other, ATEX requirements are treated as so specialised that quality teams defer entirely to the supplier, losing the ability to ask the right questions or identify gaps before they become field problems.
This article cuts through both extremes. It explains what ATEX actually requires, how zones and equipment categories interact, where projects most commonly go wrong and what a well-managed ATEX compliance process looks like in practice.
What Is ATEX?
ATEX refers to two European Directives governing equipment and working environments in explosive atmospheres:
- ATEX 114 (Equipment Directive, formerly 94/9/EC): Governs the design and manufacture of equipment intended for use in potentially explosive atmospheres. Equipment must be designed, tested and certified to appropriate protection standards by an approved body.
- ATEX 153 (Workplace Directive, formerly 1999/92/EC): Governs the responsibilities of employers to assess and classify hazardous areas where explosive atmospheres may exist, and to ensure that suitable equipment is used within those areas.
In the UK post-Brexit, the EU ATEX directives are retained in UK law through the Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 2016 (EPS Regs). Products newly placed on the UK market must carry UKCA marking (rather than CE) and reference a UK Approved Body, though transitional arrangements have applied. For export to EU member states, CE marking and EU Notified Body involvement remains required.
The international equivalent, IECEx, is increasingly specified on global projects — particularly where equipment will be used across multiple jurisdictions.
Important: ATEX certification applies to the equipment — not to the installation. Certified equipment that is installed incorrectly, in the wrong zone or without correct cable entry protection, is not ATEX compliant in practice, regardless of its certificate.
Hazardous Area Zones
Before specifying ATEX equipment, the hazardous area must be classified. This is the employer's responsibility under the Workplace Directive and is governed in the UK by DSEAR (Dangerous Substances and Explosive Atmospheres Regulations 2002). The classification defines which zones apply — and zones dictate the equipment category required.
| Zone | Gas / Vapour | Dust | Description |
|---|---|---|---|
| Zone 0 / Zone 20 | Zone 0 | Zone 20 | Explosive atmosphere present continuously or for long periods |
| Zone 1 / Zone 21 | Zone 1 | Zone 21 | Explosive atmosphere likely to occur in normal operation |
| Zone 2 / Zone 22 | Zone 2 | Zone 22 | Explosive atmosphere not likely to occur in normal operation, but may occur briefly if it does |
Equipment Categories
Equipment is manufactured and certified to one of three categories. The category defines the level of protection and determines which zones the equipment may be used in:
| Equipment Group II Category | Suitable for Zones | Protection Level |
|---|---|---|
| Category 1 (Gas: Zone 0; Dust: Zone 20) | 0, 1, 2 / 20, 21, 22 | Very high — two independent means of protection |
| Category 2 (Gas: Zone 1; Dust: Zone 21) | 1, 2 / 21, 22 | High — suitable for normal and foreseeable faults |
| Category 3 (Gas: Zone 2; Dust: Zone 22) | 2 / 22 | Normal — suitable for normal operation only |
A Category 2 item can be installed in Zone 1 or Zone 2, but not Zone 0. A Category 3 item is only suitable for Zone 2. This distinction is the source of a very common compliance error: equipment certified to the correct standard but installed in a more hazardous zone than its category permits.
Protection Concepts
ATEX equipment uses various protection methods, each defined under the EN 60079 series of standards. Common protection concepts include:
- Ex d — Flameproof enclosure: The enclosure can withstand the pressure of an internal explosion and prevent ignition of the surrounding atmosphere. Common for motor terminal boxes, junction boxes and control equipment.
- Ex e — Increased safety: Additional measures are taken to prevent sparks or excessive temperatures from occurring under normal and fault conditions. Widely used for terminal boxes and lighting in Zone 1.
- Ex i — Intrinsic safety: The electrical energy in the circuit is limited to levels insufficient to cause ignition. Used for instrumentation and control circuits; requires matched IS barriers or galvanic isolators in the safe area.
- Ex n — Non-sparking (Zone 2 only): Equipment that does not produce sparks in normal operation; suitable only for Zone 2.
- Ex p — Pressurisation: The enclosure is maintained at higher than atmospheric pressure with a protective gas to prevent explosive atmospheres from entering. Used for large control panels and analysers.
- Ex t — Dust protection by enclosure: Protection against dust by controlling surface temperatures and preventing dust ingress.
Common ATEX Compliance Mistakes on Projects
1. Late Area Classification
Hazardous area classification should be completed and formally documented before equipment is specified, purchased or designed. On many projects, area classification drawings (hazardous area drawings) are not issued until detailed design is well advanced, which means equipment may already have been ordered against the wrong zone or category. The result is expensive de-specification, delays awaiting certified replacements or, worse, non-compliant equipment being installed.
2. Purchasing Against a Datasheet Rather Than a Zone Schedule
Procurement teams often purchase ATEX equipment based on a supplier's datasheet statement that the product is "ATEX certified." Without cross-referencing the certificate against the specific zone, gas group, temperature class and protection concept required for each installation location, there is no assurance that the equipment is appropriate. The ATEX certificate number must be verified against the certificate itself, not just the datasheet.
3. Temperature Classification Errors
Every ATEX item carries a T-class (T1 to T6) that defines its maximum surface temperature. The T-class must be lower than the auto-ignition temperature of the specific gas or vapour in the hazardous area. A T4 (135°C) item may be perfectly safe in one application and dangerously non-compliant in another where the auto-ignition temperature of the hazardous substance is lower.
4. Incorrect Cable Gland Selection
ATEX certified equipment becomes non-compliant if it is connected using incorrect or non-certified cable glands, or if glands are incorrectly fitted. This is one of the most common installation-stage failures, particularly on complex skid assemblies assembled by suppliers unfamiliar with ATEX requirements.
5. Ignoring IECEx or UKCA Differences
On global projects or UK-to-EU supply, the difference between CE marking (EU), UKCA marking (UK) and IECEx certification (international) creates compliance complexity. These are separate certification schemes with separate bodies. An item carrying CE marking (EU Notified Body) may not be compliant for UK market placement post-Brexit without UKCA marking — though transitional arrangements must be tracked as they change.
A Well-Managed ATEX Process
Effective ATEX compliance on a project requires coordination between several disciplines. Quality's role is to ensure that the compliance evidence chain is complete and verifiable:
- Area Classification: Hazardous area drawings formally issued, reviewed and approved before equipment purchasing commences.
- Equipment Schedule: A project-level ATEX equipment schedule (or Ex Equipment Register) listing every item in a hazardous area, its location, required zone/category, actual certificate number and T-class.
- Certificate Verification: Every certificate is reviewed — not just referenced. Certificates expire, can be withdrawn and may have conditions or restrictions that the datasheet does not show.
- Supplier Quality Surveillance: ATEX items are flagged on the ITP as requiring certificate review and, for complex items, factory inspection of markings and protection integrity before despatch.
- Installation Verification: A pre-commissioning inspection checklist specifically covering ATEX requirements: correct equipment in correct zone, correct cable glands fitted and sealed, correct earthing, no physical damage to enclosures or Ex protection.
- ATEX Documentation Package: A complete ATEX documentation package (certificates, declarations of conformity, Ex equipment register, hazardous area drawings) is compiled and handed over as part of the project LTQR.
Remember: The duty holder (the operator of the facility) is ultimately responsible for ensuring that equipment in hazardous areas is appropriate and correctly installed. A well-documented ATEX compliance trail protects everyone in the supply chain and demonstrates due diligence if an incident investigation ever occurs.
Summary
ATEX compliance is not a single box to tick — it is a thread that runs through hazardous area classification, equipment specification, purchasing, supplier quality surveillance, installation inspection and documentation handover. Projects that treat ATEX as a certificate-collection exercise routinely discover problems at commissioning or handover that are expensive and time-consuming to resolve. Projects that integrate ATEX compliance into their quality planning from the outset consistently achieve first-time compliance with minimal rework.
Project Quality People provides ATEX compliance support from specification development through to final documentation handover. Contact us to discuss your project requirements.
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