NOx Tier I/II/III

MARPOL Annex VI Regulation 13 sets nitrogen oxide emission limits for marine diesel engines above 130 kW by the ship’s keel-laying date and rated engine speed n. Tier I applies to engines on ships built 2000 to 2010, Tier II from 1 January 2011 with about a 20 percent cut, and Tier III a roughly 80 percent cut below Tier I for engines on ships built from 1 January 2016 operating inside designated NOx emission control areas. Tier III is usually met by selective catalytic reduction or exhaust gas recirculation. Compliance is documented through the engine’s EIAPP certificate and Technical File.