NOx Tier III
Strictest IMO NOx limit (~3.4 g/kWh at 130 rpm); applies to engines >130 kW installed on ships built ≥2016 trading in NOx ECAs.
In practice
SCR or EGR or LNG dual-fuel operation engaged before crossing into NOx ECA. Engineer logs SCR urea consumption and dosing rate.
Regulatory detail & full definition
Strictest IMO NOx limit under MARPOL Annex VI Reg. 13, applying to engines above 130 kW installed on ships built on or after 1 January 2016 and trading in NOx ECAs (currently the North American and US Caribbean ECAs, with the Baltic and North Sea NOx ECAs effective 2021). Tier III is roughly 80% below Tier I. Compliance is achieved through Selective Catalytic Reduction (SCR), Exhaust Gas Recirculation (EGR), or LNG dual-fuel operation; engine builders certify and class verifies onboard.
Authoritative source: MARPOL Annex VI (Air pollution) ↗
Related
Source: MARPOL Annex VI Reg. 13
High confidence
Editorial confidence: how we grade.