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The EMC Directive requires equipment to meet the essential requirements in Annex I. For apparatus, conformity assessment must demonstrate that generated electromagnetic disturbance does not exceed the level above which radio, telecommunications, or other equipment cannot operate as intended, and that the apparatus has adequate immunity for its intended use.

A failed emission or immunity test therefore means the tested configuration has not demonstrated the relevant part of the essential requirements. It may still be possible to show conformity after redesign, a justified technical change, a corrected installation condition, a different representative configuration, or a properly documented standards route, but the failed result must be addressed rather than buried.

Start with a controlled failure record, not a rewritten pass narrative. Preserve the failed test report, lab observations, plots, limits, setup photos, operating modes, cable routing, auxiliary equipment, and deviations from the planned test method. Then identify whether the failure is caused by the product design, the representative configuration, production variation, installation conditions, or an incorrect standard or test setup.

Remediation should be technical enough to explain why the corrected configuration now meets the relevant phenomenon. Typical records include changes to filtering, shielding, grounding, PCB layout, enclosure bonding, firmware operating modes, clocking, cable selection, power supply, installation instructions, or component specification. If the product is a fixed installation issue rather than apparatus, document the good engineering practice and component intended-use information that support the installation correction.

Update the technical documentation before release. The file should show the failed result, what changed, why the change addresses the emission or immunity issue, what standard or technical specification now supports the claim, and whether the change affects other Union legislation listed on the same EU declaration of conformity.

For harmonised standards, check that the reference is one published for the EMC Directive and that the product still falls within the standard's scope, limits, test methods, and Annex ZZ mapping. If a standard was superseded, part-applied, or deviated from, record the date and scope of the standard used, the parts applied, the deviation, and the additional evidence used to cover the essential requirements. Do not sign or update the EU declaration of conformity for the affected model until the evidence supports the statement that the essential requirements have been demonstrated.

The retest should prove the same risk has been closed, not merely that a different sample passed a different setup. Match the retest to the failed phenomenon, the corrected configuration, and the intended operating conditions. Where the apparatus has multiple representative configurations, retain the rationale for the worst-case configuration and explain why untested configurations remain covered.

Keep the retest package readable for a market-surveillance request: final sample identification, version-controlled design changes, test plan, lab report, applied standards and dates, deviations or alternative specifications, photographs or diagrams of the setup, measured results against limits or criteria, and an approval note that connects the retest to the EU declaration of conformity.

Reassess the product when a change can affect the electromagnetic compatibility conclusion already documented for the apparatus. Examples include changes to circuit design, power supply, shielding, enclosure, grounding, filters, ports, cables, installation conditions, firmware behavior that affects emissions or immunity, operating configuration, or the intended electromagnetic environment.

Directive 2014/30/EU requires manufacturers to take changes in apparatus design or characteristics, and changes in the harmonised standards or technical specifications used for the declaration, adequately into account. The EMC assessment must also cover normal intended operating conditions and the configurations the manufacturer identifies as representative of intended use.

If the existing assessment relied on harmonised standards, a standards change does not automatically require a complete retest. The Commission EMC Guide says the evaluation may be limited to modifications directly affecting the apparatus, but the manufacturer must evaluate whether the newer standard, clause, phenomenon, or scope change affects the product and may consider re-testing.

The original manufacturer remains responsible for apparatus it places on the market, including the conformity assessment, technical documentation, EU declaration of conformity, and CE marking. But the Directive also says an importer or distributor is treated as the manufacturer when it places apparatus on the market under its own name or trade mark, or modifies apparatus already placed on the market in a way that may affect compliance.

That matters for private-labeling, refurbishment, retrofit kits, field upgrades, local power-supply substitutions, enclosure changes, and software or accessory packages sold as a changed product. The company making or commissioning the compliance-affecting modification should not assume the original manufacturer, test lab, supplier, or notified body carries the updated conformity responsibility.

Importers also have their own gatekeeping role: before placing apparatus on the market, they must ensure that the manufacturer carried out the appropriate conformity assessment, drew up technical documentation, applied CE marking, and supplied required documents. If the importer has reason to believe the modified apparatus does not conform, it must not place it on the market until it is brought into conformity.

If the modification is covered by the existing assessment, the file should show why. If the modification changes the assessed apparatus, the EU declaration of conformity may need to be updated so it identifies the modified apparatus, the applicable Union acts, the standards or technical specifications applied, and any notified-body certificate information where applicable.

The CE marking is not a substitute for the reassessment. CE marking is affixed after the applicable conformity assessment has been completed. If the change creates a new product or invalidates the existing assessment basis, the modifier must complete the relevant conformity work before placing the modified apparatus on the market with CE marking.

If the product used the EU-type examination route and there is an EU-type examination certificate, modifications to the approved type that may affect conformity or certificate validity must be reported to the notified body holding the technical documentation. The Directive requires additional approval as an addition to the original certificate for those modifications.

A useful modification record lets a market-surveillance authority, importer, distributor, or customer understand whether the existing CE-marked product evidence still applies. It should connect the physical change to the EMC phenomena, standards, test configurations, and DoC entries that were reviewed.

For targeted re-testing, the record should explain why the selected tests, clauses, frequency ranges, configurations, or engineering comparisons are enough. For no-test decisions, the Commission EMC Guide says technical documentation should include explanations demonstrating how the essential requirements are met when tests are not performed under the manufacturer's responsibility.

For fixed-installation-specific apparatus, do not mix the apparatus exemption into ordinary product sales. The EMC Guide describes that exemption as tied to a particular fixed installation and a direct link between the manufacturer of that apparatus and the responsible installation parties.