A commonly used name for an Emission Control Area designated under MARPOL Annex VI to control sulphur oxides and particulate matter, where the 0.10%-by-mass fuel-sulphur limit applies unless an approved equivalent method is used. The legal text generally uses "Emission Control Area"; not every ECA has identical pollutant coverage, so a sulphur ECA should not be confused with an area designated only for nitrogen-oxide controls.
