Amendments to NOx Technical Code 2008 (in force on 1 Sep 2026)

C26039| 25 August 2026

Notice to: Ship Owners / Managers / Operators / Surveyors / Auditors

This is to inform of amendments to NOx Technical Code 2008, adopted by IMO Res. MEPC.398(83) on 11 Apr 2025 and coming in force on 1 Sep 2026. The amendments refer to certification of an engine subject to substantial modification or being certified to a Tier to which the engine was not certified at the time of its installation.

Meaning of Substantial Modification

A substantial modification means any change or alteration to a marine diesel engine that could potentially cause the engine to exceed the applicable NOx emission limits defined in Regulation 13 of MARPOL Annex VI.

Examples of substantial modification could be:

• Change of key technical parameters or core components such as camshafts, fuel injection systems, air systems, combustion chamber configurations, or timing calibrations;
• Upgrade or alteration of parts listed in the engine’s official NOx Technical File with unverified or non-OEM parts that change combustion or emission characteristics.

What is not a substantial modification:

• Normal / routine maintenance and replacement of parts specified in the NOx Technical File of an engine;
• Installation of a certified “Approved Method” designated for pre-2000 engines under MARPOL Annex VI, Regulation 13.7.

Key points to know as per the Amendments

• The amendments refer to an Individual Engine or an Engine Group represented by the Parent Engine. They shall not be accepted for Engine Family certification;
• Where, as a result of a substantial modification, the rated power and/or the rated speed of the engine is altered from the original condition, the engine nameplate shall be replaced accordingly;
• In setting the load points of the test cycle, load points with 100% load point no lower than 85% of rated power are allowed;
• The Administration agreement on Engine Emission test plan is required before scheduling;
• A new Figure 4, flowchart guidance on the certification process has been added as Appendix II of the Code.

Act now

Ship Owners / Managers / Operators should take note of the circular and seek Dromon Head Office advice in case an engine is going to be subject to a substantial modification or to be certified to a Tier to which the engine was not certified at the time of its installation.

Surveyors will receive special instructions from Dromon Head Office in case they are requested to inspect / certify such engines.