Equivalents (SOx scrubber, etc.) – Regulation 4
The Administration of a Party may allow any fitting, material, appliance or apparatus, such as SOx scrubbers, to be fitted in a ship or other procedures, alternative fuel oils, or compliance methods used as an alternative to that required by MARPOL Annex VI.
The Administrations of Party that allow a fitting, material, appliance, apparatus or other procedures, alternative fuels, or compliance methods used as an alternative to that required by MARPOL Annex VI shall advise IMO on it. Notifications of use of equivalent provision from Parties are available through the Global Integrated Shipping Information System (GISIS) (Registration required for public users).