Ozone depleting substances (ODS)
These are man-made chemicals which degrade the ozone layer in the upper atmosphere and which are being phased out, both in terms of manufacture and use, in accordance with the Montreal Protocol. Within the marine context, these are the halons, as used in some older fire fighting systems, and the chlorofluorocarbons (CFC) used as refrigerants and in insulation material. Any deliberate emissions of ozone-depleting substances are prohibited.
Further reading: Regulations for Prevention of Air Pollution,
Annex VI to MARPOL 73/78.