On 1st January 2020 the UK and EU legal systems separated, the UK went in to a transition period and for that year it was business as normal as all EU directives were still valid in the UK i.e. the 2014/34/EU Atex directives was still being implemented up until the end of 2020.

Atex is not product certification but an EU legal framework to allow the sale/use of equipment within the hazardous area and the UK was no longer part of the EU legal system
Full Brexit was implemented as of 1st January 2021 UKCA Mark

  • Strictly speaking the Atex directive as a legal construct and therefore Atex certification is no longer valid in the UK. However, temporary exceptions have been put in place to accept the CE mark and hence Atex in place of the UK certification

The hazardous area changes are not backdated so all equipment either installed or within the supply chain can still be used.

The manufacturer has an obligation
To draw up a declaration of conformity, or a written attestation of conformity (for components of products), ensure that declaration or attestation accompanies the product, where applicable affix the UKCA marking3 and the specific marking of explosion protection followed by the symbol of the equipment group and category to the product.

Using Atex labelled equipment, by inference temporarily accepts the EU Type certificate but what is not clear is whether the EU DoC, as EU legal document is valid. or must an UK DoC be issued to include relevant to Atex labelling. Either way in practice it will me little difference to the user as, by either option, they will have fulfilled their duty of care.
Update: the exception to allow CE (Atex) marking in place of UKCA has been extended until the end of 2022.
For further information please refer to the relevant government guidelines.