NOx Technical Code

The NOx Technical Code is the mandatory IMO code governing testing, survey, and certification of marine diesel engines for nitrogen oxide emissions under MARPOL Annex VI Regulation 13. The current version, the NOx Technical Code 2008, was adopted by resolution MEPC.177(58) and applies to engines over 130 kW installed on ships. It defines the weighted test cycles, the parent-engine and engine-group concepts, the Engine International Air Pollution Prevention (EIAPP) Certificate, and the onboard NOx verification procedures (engine parameter check, simplified measurement, direct measurement). Tier I, II, and III limits scale with rated engine speed; Tier III applies to engines on ships built on or after the relevant date operating in NOx Emission Control Areas.