Tier III emissions
MARPOL Annex VI NOx emission standard for engines installed on vessels constructed after 1 January 2016 operating in designated NOx Emission Control Areas.
Tier III applies to marine diesel engines on vessels constructed after 1 January 2016 operating in NOx Emission Control Areas (the North American ECA, the US Caribbean ECA, the Baltic Sea NECA, and the North Sea NECA). The standard requires roughly 75 percent reduction in NOx emissions versus Tier I, achieved through SCR (selective catalytic reduction) or EGR (exhaust gas recirculation). New build superyachts crossing into NECAs must specify Tier III propulsion at design.