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Prevention of Air Pollution from cargo vapours, ozone depleting substances & Co2 emissions

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.

Ozone layer in the stratosphere protects the earth from excessive harmful UV radiation. Scientific studies show that certain man-made chemicals cause its depletion. Atmospheric measurements show that the ozone layer is getting thinner and that, at certain times of the year, an ozone layer hole appears over Antarctica.

Scientists believe that certain manmade chemicals are the cause of this damage. These chemicals include the chlorofluorocarbons (CFCs) found in refrigeration systems, solvents, blowing agents for polyurethane foam and halons used for fire-fighting. Collectively, there are named Ozone Depleting Substances or ODS.

Under MARPOL Annex VI, Regulation 12, deliberate emissions of ODS are prohibited. However it is important to understand what is meant by “deliberate”. Deliberate emissions refer to the release of ODS in the course of servicing, repairing or disposing of systems or equipment. It does not include the critical release of such ODS as halon used to fight a fire, nor does it include minimal releases associated with the recycling or recapture of ODS (e.g. in refrigeration systems).



It should be noted that this regulation has already been superseded by various other legislation (e.g. EU law and Montreal Protocol) and will no doubt change with future international environmental legislation. For example some alternatives to ODS (such as HFCs) may have no affect on ozone depletion however may have a high potential for global warming. Future legislation may therefore disallow these substances in years to come.


Meanwhile in order to comply with existing regulations the following procedures are to be adopted :
    Onboard Procedures

    Manuals or procedure sheets should be available on board that cover the operation and maintenance of each refrigeration system on board. If such procedures do not exist, then you should either ask the office to contact the manufacturer, or create your own procedures on board.

    Such procedures apply to mainly large systems as maintenance would not normally be required for small units. If all items that contain the primary refrigerant (e.g. compressor, receiver, condenser and evaporator) are part of a “stand alone” unit supplied in a fully charged condition (i.e. refrigerant already in the system) then this equipment is also NOT considered under regulation 12.

    Monitoring and Maintenance

    A method or system is to be adopted to monitor refrigerant leaks. This may be done by taking regular readings of refrigerants (e.g. level or pressure gauges) and maintaining a record of how much refrigerant is used to top-up the system. If the maintenance of refrigeration systems is undertaken by the ship’s staff, then a recovery unit is to be provided. The recovery unit will include a specialised container or external cylinder for each type of refrigerant to enable the recovered substance to be stored. Such recovery cylinders will be marked clearly e.g. “CFC R-12 – Recovered”

    Periodic Leak Detection

    All possible measures should be made to prevent and minimise leakage of refrigerants. In particular regular leak detection of the refrigeration systems is to take place. The period between detection tests is to be defined and entered into the planned maintenance system. Material or equipment used to detect leaks may include: soapy water, halide torch, electronic detector or fluorescent dye additive in the refrigerant.

    Record Keeping

    It is essential that records are kept that can be shown to port state control in order to verify that Regulation 12 is being adhered to. (MARPOL 73/78 Annex VI – Record book for Fuel Oil and Ozone Depleting Substances) is to be used for this purpose.



Regulation 12 – Ozone-depleting Substances

1. This regulation does not apply to permanently sealed equipment where there are no refrigerant charging connections or potentially removable components containing ozone-depleting substances.

2. Subject to the provisions of regulation 3.1, any deliberate emissions of ozone-depleting substances shall be prohibited. Deliberate emissions include emissions occurring in the course of maintaining, servicing, repairing or disposing of systems or equipment, except that deliberate emissions do not include minimal releases associated with the recapture or recycling of an ozone-depleting substance. Emissions arising from leaks of an ozone-depleting substance, whether or not the leaks are deliberate, may be regulated by Parties.

3.1. Installations that contain ozone-depleting substances, other than hydro-chlorofluorocarbons, shall be prohibited:

.1. on ships constructed on or after 19 May 2005; or
.2. in the case of ships constructed before 19 May 2005, which have a contractual delivery date of the equipment to the ship on or after 19 May 2005 or, in the absence of a contractual delivery date, the actual delivery of the equipment to the ship on or after 19 May 2005.

3.2. Installations which contain hydro-chlorofluorocarbons shall be prohibited:
.1. on ships constructed on or after 1 January 2020; or
.2. in the case of ships constructed before 1 January 2020, which have a contractual delivery date of the equipment to the ship on or after 1 January 2020 or, in the absence of a contractual delivery date, the actual delivery of the equipment to the ship on or after 1 January 2020.

4. The substances referred to in this regulation, and equipment containing such substances, shall be delivered to appropriate reception facilities when removed from ships.

5. Each ship subject to regulation 6.1 shall maintain a list of equipment containing ozone-depleting substances. see footnote

6. Each ship subject to regulation 6.1 that has rechargeable systems that contain ozone-depleting substances shall maintain an ozone-depleting substances record book. This record book may form part of an existing log-book or electronic recording system as approved by the Administration.

7. Entries in the ozone-depleting substances record book shall be recorded in terms of mass (kg) of substance and shall be completed without delay on each occasion, in respect of the following:
.1. recharge, full or partial, of equipment containing ozone-depleting substances;
.2. repair or maintenance of equipment containing ozone-depleting substances;
.3. discharge of ozone-depleting substances to the atmosphere:
.3.1. deliberate; and
.3.2. non-deliberate;
.4. discharge of ozone-depleting substances to land-based reception facilities; and
.5. supply of ozone-depleting substances to the ship.


Carbon Dioxide Emissions (CO2)

Carbon dioxide, a by-product of combustion, is the main greenhouse gas blamed for trapping heat in the atmosphere and causing global warming.

IMO is working on measures to regulate greenhouse gas emissions from ships and various methods to achieve a reduction of greenhouse gas emissions.

It is important for the industry to identify and develop the mechanisms needed to achieve the limitation or reduction of carbon dioxide (CO2) emissions from ships, noting that climate change caused by greenhouse gas emissions from the burning of fossil fuel is a steadily growing concern for most countries.

Local and international regulations relating to the control of CO2 emissions from ships shall be strictly complied with.

Volatile Organic Compounds

During cargo operations on various types of tanker vessel, the need to discharge various types of cargo vapours to the atmosphere is sometimes unavoidable, while any emission of VOCs from Tankers at “designated” ports or terminals is prohibited by MARPOL ANNEX-VI.

The Local regulations relating to the vapor venting shall be strictly adhered to. If the Master has any doubt regarding compliance, he is to contact the Local authority.

VOC Requirements

The revised MARPOL Annex VI introduced a new mandatory requirement (regulation 15.6) regarding Volatile Organic Compounds (VOC) emissions control. This applies to all tankers carrying crude oil.

Since 1st July 2010, every tanker carrying crude oil is required to have on board and implement a ship-specific VOC Management Plan, approved by the Administration.

The Plan must take into account guidelines contained in: •MEPC.185 (59) and
•MEPC.1/Circ.680.

The purpose of the Plan is to ensure that VOC emissions resulting from tanker operations to which regulation 15.6 applies are prevented or minimised as much as possible.

The ship-specific VOC Management Plan must provide written procedures for minimising VOC emissions during:

•loading of cargo
•sea passage, and
•discharge of cargo.

Additionally, VOCs generated during crude oil washing needs to be considered.




Further reading: Regulations for Prevention of Air Pollution, Annex VI to MARPOL 73/78.



Other sources marine pollution by air:


Related articles

  1. Marpol annex I - Preventing pollution by oil -Notes on Oily Water Separators


  2. Marpol Annex II -Noxious Liquid Substances in Bulk


  3. Marpol annex III -Pollution by other harmful substances & harmful packaged goods


  4. Marpol annex IV - Prohibition on Sewage Discharge


  5. Marpol annex V - Pollution by garbage


  6. Marpol annex VI - Pollution by air


  7. Prohibition on use of harmful (TBT) anti-fouling paints


  8. Pollution by ballast water


  9. Prevention of pollution while carrying out overboard maintenance


  10. Environment friendly purchasing


  11. Environmental awareness


  12. Burning of heavy fuel oil & diesel oil - Environmental impacts






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