The Office of Commercial Vessel Compliance issued CG-CVC Policy Letter 12-04 in 2012 asking for correspondence from flag administrations regarding equivalencies for exhaust gas cleaning systems (scrubbers) under MARPOL Annex VI Regulation 4.
As CG-CVC no longer requests this notification, flag administrations should continue to make appropriate notifications to the IMO regarding equivalencies issued under MARPOL Annex VI Regulation 4, in order to avoid control and enforcement action by the Coast...
https://safety4sea.com/scrubber-notifications-in-ecas-established-within-the-us/