# Commission Implementing Regulation (EU) 2017/656 of 19 December 2016 laying down the administrative requirements relating to emission limits and type-approval of internal combustion engines for non-road mobile machinery in accordance with Regulation (EU) 2016/1628 of the European Parliament and of the Council (Text with EEA relevance), Division 2.4.14: Exhaust after-treatment systems


The function and combination of the following devices are regarded as membership criteria for an engine family:
(a) Oxidation catalyst;
(b) DeNOx system with selective reduction of NOx (addition of reducing agent);
(c) Other DeNOx systems;
(d) Particulate after-treatment system with passive regeneration:
(1) wall-flow,
(2) non-wall-flow;
(e) Particulate after-treatment system with active regeneration:
(1) wall-flow,
(2) non-wall-flow;
(f) Other particulate after-treatment systems;
(g) Other devices.
When an engine has been certified without exhaust after-treatment system, whether as parent engine or as member of the engine family, then this engine, when equipped with an oxidation catalyst (not with particulate after-treatment system), may be included in the same engine family, if it does not require different fuel characteristics.
If it requires specific fuel characteristics (e.g. particulate after-treatment systems requiring special additives in the fuel to ensure the regeneration process), the decision to include it in the same engine family shall be based on technical elements provided by the manufacturer. These elements shall indicate that the expected emissions level of the equipped engine complies with the same limit value as the non-equipped engine.
When an engine has been certified with exhaust after-treatment system, whether as parent engine or as member of an engine family, whose parent engine is equipped with the same exhaust after-treatment system, then this engine, when equipped without exhaust after-treatment system, shall not be added to the same engine family.

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Source: https://www.legislation.gov.uk/eur/2017/656/attachment/10/division/division/2./division/2.4./division/2.4.14. (the official version)
Page: https://openlegislation.uk/eu-regulation-2017-656/attachment-10/division/division-2./division-2.4./division-2.4.14.
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.