ATEX certification — what it covers and what it does not

ATEX certification is frequently treated as a quality mark — evidence that a product is safe for use in hazardous areas. That is an incomplete reading. A certificate confirms that an equipment design has been evaluated against specific harmonised standards and found to meet those standards. It does not confirm that the equipment is appropriate for the zone it has been installed in, that it has been installed correctly, or that the installation as a whole meets the requirements of the applicable zone classification.

Understanding what a certificate covers — and what it explicitly does not — is essential for anyone specifying, installing or operating heating systems in classified areas. The gaps in certification coverage are where compliance failures most commonly occur in practice.

Most ATEX compliance failures do not come from missing certificates — they come from incorrect specification, installation decisions made without reference to the zone drawing, or system integration that was never properly verified.

Conformity assessment: Notified Body vs manufacturer self-declaration

The route to ATEX certification depends on the equipment category:

• Category 1 equipment (Zone 0 / Zone 20). The most demanding route. An EC Type Examination Certificate (Annex III) must be issued by a Notified Body, confirming that the design meets the applicable harmonised standards. Production quality assurance under Annex IV or V is also required. Category 1 heating equipment is extremely rare — Zone 0 is almost exclusively an internal classification (inside tanks and vessels) where external heating is not installed.
• Category 2 equipment (Zone 1 / Zone 21). An EC Type Examination Certificate from a Notified Body is required for the equipment design. For one-off or custom items not covered by an existing type certificate, EC Unit Verification under Annex V applies — the Notified Body examines each individual unit. Manufacturer self-declaration is not acceptable for Category 2 equipment.
• Category 3 equipment (Zone 2 / Zone 22). No Notified Body involvement is required. The manufacturer prepares technical documentation demonstrating compliance with the applicable harmonised standards and issues a Declaration of Conformity. The ATEX marking is applied on the basis of that self-declaration. The equipment must still comply with the standards — the difference is that compliance is manufacturer-assessed rather than independently verified.

For custom heating systems — non-standard drum dimensions, integrated follower plates, unusual power densities — the distinction matters practically. A custom Category 3 heater can be manufactured and certified by the manufacturer without external review at each iteration. A custom Category 2 heater requires either an extension to an existing Notified Body type certificate or Unit Verification of the specific item. This affects both lead time and cost, and should be factored into project planning from the outset.

What a certificate does not cover

Critical aspects of compliance that fall outside a certificate's scope:

• Suitability for the specific zone. A certificate confirms that equipment meets Category 2 standards. It does not confirm that the zone where it is to be installed is actually a Zone 1 area, or that the T-class and gas group are correct for the substances present at that installation. That determination is the responsibility of the specifier and installer, based on the zone classification drawing.
• Correct installation. A correctly certified heater installed with non-rated cable glands, connected to a non-rated control panel located inside the zone boundary, is a non-compliant installation regardless of the heater's certification status. IEC 60079-14 governs installation requirements and is the installer's responsibility, not the manufacturer's.
• The complete system. Individual component certificates do not aggregate into a certified system. The installation must be documented against the zone drawing and installation standard as a whole.
• Ongoing compliance. Certification applies to the equipment as supplied. Modifications, repairs and substitutions — even minor ones — can invalidate certification if they affect the parameters covered by the certificate. Post-installation modifications must be assessed against the original certification basis.
• Maintenance state. A certified item that has been damaged, incorrectly reassembled, or maintained with non-certified replacement parts may no longer meet the requirements of its certification. Periodic inspection under IEC 60079-17 is the mechanism for verifying ongoing compliance.