NOx emission limits (Tier I, II, III)

The vi_1 entry records MARPOL Annex VI nitrogen-oxide emission limits, defining three progressive tiers: Tier I applies to ships built before 2011 with a baseline limit, Tier II applies to vessels built after 2011 with a 20 % reduction, and Tier III imposes a 80 % cut in designated emission control areas. Compliance is verified through engine testing and certification.