IMO NOx Tier III

IMO NOx Tier III is the strictest engine NOx limit under MARPOL Annex VI Reg.13, applying to marine diesels above 130 kW fitted on ships built from 2016 (North American and US Caribbean ECAs) and 2021 (North and Baltic Sea ECAs), and only while operating inside those ECAs. The limit is a speed-dependent curve, about 3.4 g/kWh at low speed, roughly 80 percent below Tier I. Compliance needs SCR, EGR, or a gas-fueled (LNG, methanol) engine.