Does modifying certified Ex equipment void its certificate?
Abstract
In effect, yes. A certificate covers only the construction in its schedule drawings, so a change to material, fit, form or function outside them leaves the item uncertified. Alterations the certificate allows and like-for-like repair under IEC 60079-19 do not.
In effect, yes. A certificate and the manufacturer's declaration cover only the construction described in the certificate's schedule drawings. A change that affects material, fit, form or function and is not described there is a modification: the unit no longer matches what was certified, and nobody vouches for it any more. Changes that the certificate itself allows, and repairs that restore the certified construction under IEC 60079-19, do not have this effect.
Short answer
- Modification: a change to the design that affects material, fit, form or function. The IEC vocabulary notes that a modified item no longer complies with the construction in the schedule drawings.
- Alteration: a change to an alternative construction that the certificate already describes, for example an extra cable entry of a size and position the certificate permits. Done as documented, it keeps the equipment within its certificate.
- Repair: restoring function after a defect without new features, ideally to the schedule drawings. The ATEX directive does not apply again, but national workplace rules apply and the repair should follow IEC 60079-19.
- Substantial modification in the EU: a change that affects a characteristic covered by the essential requirements (for example temperature) or the integrity of a type of protection. The ATEX directive applies again if the item is then placed on the market or used for one's own purposes, and whoever made the change takes on the manufacturer's duties.
- Before reuse: restore the certified construction, have the change assessed and covered by the manufacturer or a certification body, or replace the item.
Why a change takes the equipment outside its certificate
An Ex certificate is not a general statement that a product type is safe. It certifies a defined construction: the drawings, materials, gaps, creepage distances, components and ratings listed in the certificate. The test results apply to that construction only. IEC 60050-426 (entry 426-15-06) defines a modification as a change to the design that affects material, fit, form or function. Its note gives the consequence: because the certificate describes a specific construction, a modified item no longer complies with the construction described in the schedule drawings.
IEC 60079-19:2025 (edition 5), the repair and overhaul standard, keeps the distinction. It defines an alteration as a change to an alternative construction that is described in the certificate. Edition 5 also splits the earlier joint clause on alterations and modifications into two separate clauses. For motors and other equipment with windings it adds that the type of winding may not be changed during reclamation.
| Change | Usually |
|---|---|
| Fitting a certified gland or plug in an entry the certificate already provides | Normal installation |
| Adding an entry in a flameproof enclosure where the certificate defines permitted size, thread and position | Alteration |
| Drilling an entry the certificate does not provide for | Modification |
| Fitting a lamp or heater of higher power than marked | Modification (temperature class at risk) |
| Replacing a metal cover with a plastic one, or repainting with a different coating | Modification (static charge, impact) |
| Adding terminals or devices inside an increased safety box beyond its certified layout | Modification |
| Rewinding a motor to different winding data | Modification |
What the law says in the EU
The European Commission's ATEX 2014/34/EU Guidelines (6th edition, January 2026) treat repaired, refurbished and reconfigured products separately from substantially modified ones. Repair without new features does not bring the directive back. A substantial modification, one that affects a characteristic covered by the essential requirements or the integrity of a type of protection, does: Directive 2014/34/EU applies again when the modified item is placed on the market or used for one's own purposes. The person who makes such a modification therefore has to carry out a conformity assessment as if manufacturing new equipment. For a single item, unit verification by a notified body is one possible route.
Under the workplace directive 1999/92/EC the employer remains responsible for using only equipment that is safe in its zone. Inspection standard IEC 60079-17 has long included a check that there are no unauthorised modifications in its inspection schedules, while noting that some changes, for example to printed circuit boards, are hard to spot.
Example: Maintenance needs one more cable into a flameproof control station on a Zone 1 skid. The certificate lists two M20 entries in defined positions; both are in use. Drilling a third hole on site would be a modification: the flamepath length of the thread, the wall strength and the reference pressure are no longer covered. The options are to ask the manufacturer whether a certified variant or supplement covers a third entry, to add a separate certified junction box, or to replace the station. The workshop must not simply drill and tap it.
Common mistakes
- "It still works, so it is still certified." Function says nothing about flamepaths, temperatures or creepage distances.
- Swapping parts for "equivalents". Only parts specified by the manufacturer, or proven identical to the schedule drawings, keep the construction certified.
- Assuming a repair workshop can certify a modification. A service facility repairs to the certificate; a change outside it needs the certificate holder or a certification body.
- No records. Without a repair or modification record, the next inspector cannot tell what was changed.
Related on excodex
- Repair, overhaul and modification of Ex equipment (IEC 60079-19)
- EU-Type Examination Certificates and Notified Bodies explained
- The ATEX Declaration of Conformity and the CE and Ex marking: what must be on the label
- Who is allowed to repair Ex equipment?
- Does refurbished or second-hand Ex equipment need a new certificate?
Standards and further reading
- IEC 60079-19:2025, equipment repair, overhaul and reclamation (edition 5); preview with scope, definitions and list of changes: vde-verlag.de (PDF)
- IEC 60050-426 (International Electrotechnical Vocabulary), entry 426-15-06 "modification": electropedia.org
- European Commission, ATEX 2014/34/EU Guidelines, 6th edition (January 2026), section on used, repaired or modified products and spare parts: single-market-economy.ec.europa.eu (PDF)
- IEC 60079-17, inspection and maintenance; the public Indian adoption of the 2007 edition shows the "no unauthorised modifications" inspection item: archive.org
- UK government guidance on the 2016 Regulations (Great Britain): products substantially changed in performance, purpose or type count as new: gov.uk
This article is general technical information prepared by the excodex editorial team. It does not replace the applicable standards, the equipment certificates and instructions, national regulations or the assessment of a competent person.