In most cases, Ex t assessment requires testing or verification to demonstrate compliance with IEC 60079-31 requirements for equipment used in combustible dust atmospheres.

The extent of testing depends on the equipment design, enclosure type, surface temperature limits, ingress protection level, and intended operating conditions. Typical evaluations include temperature measurement, dust ingress protection checks, and verification of marking and constructional requirements.

However, in some cases, existing test reports, certified enclosures, or previously evaluated designs may be used to support the assessment and reduce the need for full repeat testing. The applicability of such evidence is determined during the technical review.

A product-specific evaluation is always required to confirm whether additional testing is necessary for Ex t compliance.

Changes to an Ex t product may require re-testing or re-evaluation if they could affect the enclosure integrity, surface temperature performance, or dust protection characteristics defined in IEC 60079-31.

Typical triggering changes include modifications to enclosure design, material substitution, wall thickness changes, sealing systems, cable entries, or ventilation features. Alterations that affect heat dissipation, internal power dissipation, or component layout may also require reassessment due to their impact on maximum surface temperature limits.

Additionally, changes to ingress protection measures, gaskets, or fastening methods can influence dust-tightness and therefore may necessitate further testing.

Yes. Ex t testing can often cover multiple enclosure sizes or variants, provided they belong to the same enclosure family and maintain consistent design principles relevant to dust ignition protection.

Grouping is typically possible when variants share the same material type, sealing concept, construction method, and comparable thermal behavior. Differences in size or layout may be acceptable if they do not negatively affect dust ingress protection or surface temperature limits defined in IEC 60079-31.

However, significant design changes—such as different materials, modified sealing systems, or altered heat dissipation characteristics—may require additional testing or separate evaluation. A technical review is normally performed to define the allowable range of variants within one Ex t assessment scope.

The number of samples required for Ex t (dust protection by enclosure) testing depends on the enclosure design, size range, product configuration, and the scope of the evaluation under IEC 60079-31.

In many cases, multiple samples are needed because different tests may be performed on separate units, especially when testing involves thermal measurements, ingress protection checks, or verification of constructional features. Additional samples may be required for different enclosure sizes or variants within the same product family.

The exact sample quantity is determined during the technical review based on the test plan and applicable certification requirements. The manufacturer is usually informed of the required number of samples before testing begins.

Yes. Ex t evaluation can begin before the enclosure design is fully finalized, and early-stage involvement is often beneficial to identify potential compliance risks at an early design phase.

An initial assessment can be carried out using preliminary drawings, material specifications, and expected thermal and electrical loading data. This allows early verification of key requirements under IEC 60079-31, such as surface temperature limits, ingress protection concept, and suitability of the enclosure design for dust atmospheres.

However, final certification can only be completed once the enclosure design is finalized and all relevant documentation and, where applicable, test results are available. Any design changes introduced during development may require reassessment or additional testing to confirm continued compliance.