SOX and particulate matter emission controls apply to all fuel oil, combustion equipment and devices onboard and therefore include both main and all auxiliary engines together with items such boilers and inert gas generators.

These controls divide between those applicable inside Emission Control Areas (ECA) established to limit the emission of SOX and particulate matter and those applicable outside such areas and are primarily achieved by limiting the maximum Sulphur content of the fuel oils as loaded, bunkered, and subsequently used onboard. These fuel oil Sulphur limits (expressed in terms of % m/m – that is by mass) are subject to a series of step changes over the years.

The applicable rules and its evolution over the years is as follows.

Outside an ECA established to limit SOx and particulate matter emissions	Inside an ECA established to limit SOx and particulate matter emissions
4.50% m/m prior to 1 January 2012	1.50% m/m prior to 1 July 2010
3.50% m/m on and after 1 January 2012	1.00% m/m on and after 1 July 2010
0.50% m/m on and after 1 January 2020	0.10% m/m on and after 1 January 2015

The ECAs established are:

• Baltic Sea area – as defined in Annex I of MARPOL (SOX only)
• North Sea area – as defined in Annex V of MARPOL (SOX only)
• North American area (entered into effect 1 August 2012) – as defined in Appendix VII of Annex VI of MARPOL (SOX, NOx and PM)
• United States Caribbean Sea area (entered into effect 1 January 2014) – as defined in Appendix VII of Annex VI of MARPOL (SOX, NOx and PM)