Tier I, II, III NOx Limits

Tier I, II, and III are the NOx emission limits for marine diesel engines over 130 kW under MARPOL Annex VI Regulation 13, set as a function of rated engine speed and certified through the NOx Technical Code 2008. Tier I covers engines built from 2000 to 2010, Tier II engines built on or after 1 January 2011 globally, and Tier III engines operating in a NOx ECA. Tier III, about an 80% cut from Tier I, applies to 1 January 2016 keel dates in the North American and US Caribbean ECAs and to 1 January 2021 keel dates in the Baltic and North Sea NOx ECAs, usually requiring SCR or EGR.