Operational Information

Marpol 73/78 Annex VI



MARPOL 73/78 Annex VI Regulations for the prevention of Air Pollution from ships entered into force on 19 May 2005,


Basically the code covers the following


Regulation 12 - Emissions from Ozone depleting substances from refrigerating plants and fire fighting equipment.

Regulation 13 - Nitrogen Oxide (NOx) emissions from diesel engines

Regulation 14 - Sulphur Oxide (SOx) emissions from ships

Regulation 15 - Volatile Organic compounds emissions from cargo oil tanks of oil tankers

Regulation 16 - Emissions from shipboard incinerators.

Regulation 18 - Fuel Oil quality.


and will apply to all ships of 400 gross tons and above which will have to carry an International Air Pollution Prevention Certificate (IAPP Certificate). This certificate must be on board at delivery for a ship constructed (keel laid) after 19 May 2005. For ships constructed before this date, the IAPP certificate must be on board at the first scheduled dry-docking after 19 May 2005, but not later than 19 May 2008. Ships constructed (keel-laid) before 1 January 2000 need to comply with operational requirements in MARPOL Annex VI from 19 May 2005. Unless existing engines are subject to major modification, or new engines or incinerators are fitted, the requirements in Regulation 13 and constructive requirements in Regulation 16 do not apply to vessels constructed before 1 January 2000.


Ships of less than 400 tons will still have to comply with the legislation where applicable, but in there case the Administration may establish appropriate measures in order to ensure that Annex VI is complied with.


Because this web site is concerned with marine diesel engines, regulations 13, 14 and 16 will be discussed in further depth.


NOx Emissions


This regulation applies to diesel engines with a power output of more than 130 kW each which are installed on a ship constructed on or after 1 January 2000; and each diesel engine with a power output of more than 130 kW which undergoes a major conversion on or after 1 January 2000. It does not apply to lifeboat engines or emergency generators.


The NOx limits are shown on the graph on the right. the limits are set as follows:


For engines less than 130RPM (most 2 stroke crosshead engines): 17g/kWh


For Engines between 130 and 2000 rpm, a formula is used:

45 × n-0.2 g/kWh where  n is the engine speed.


e.g For an engine running at 600rpm:


45 × 600-0.2 = 12.52g/kWh


For engines above 2000 rpm: 9.8g/kWh

As From 1st January 2011 the limits change;:


For engines less than 130RPM: 14.4g/kWh

For Engines between 130 and 2000 rpm: 44 × n-0.23 g/kWh

For engines above 2000 rpm: 7.7g/kWh


After 2016 they change again to:


For engines less than 130RPM: 3.4g/kWh

For Engines between 130 and 2000 rpm: 9 × n-0.2 g/kWh

For engines above 2000 rpm: 2.0g/kWh


All certified engines are delivered with an individual Technical File that contains the engine’s specifications for compliance with the NOx regulation, and the applicable onboard verification procedure. The certification process includes an emission test for compliance with the NOx requirements on the manufacturer’s test bed


There are three on board verification procedures which can be used The method used is initially decided by the engine manufacturer, and is usually a specific chapter in the engine’s Technical File.

  • Engine parameter check method

  • Simplified measurement method

  • Direct measurement and monitoring method

The engine parameter check ensures that the present state of the engine corresponds to the specified components, calibration or parameter adjustment state at the time of initial certification. The engine’s Technical File identifies the components, settings and operating values that influences the exhaust emissions and these must be checked to ensure compliance during surveys and inspections. The components and settings will be those which affect the NOx produced by the engine, such as:

  • Injection timing

  • Injection system components (nozzle, injector, fuel pump)

  • Injection pressure

  • Camshaft components (fuel cam, inlet- and exhaust cam)

  • Valve timing

  • Combustion chamber (piston, cylinder head, cylinder liner)

  • Compression ratio (connecting rod, piston rod, shim, gaskets)

  • Turbocharger type and build (internal components)

  • Charge air cooler/charge air pre-heater

  • Auxiliary blower

  • NOx reducing equipment

The  Simplified measurement method is where the NOx content of the exhaust gas is measured during  a 20 minute full load run of the engine. Due to the possible deviations when applying the simplified measurement method, an allowance of 10% of the applicable limit value is accepted for confirmation tests and during periodical and intermediate surveys.


For the direct measurement and monitoring method, the engine will be fitted with a direct measurement system which monitors the NOx emissions, either as spot checks logged regularly or continuous monitoring. Records must be kept for at least 3 months and must have been taken in the past 30 days.


SOx Emissions




Marpol annex VI in force from May 19 2005 limits the maximum sulphur content of fuel to 4.5%

This changes to 3.5% after 1st Jan 2012 and to 0.5% after 2020 (or 2025, depending on the outcome of a review in 2018.)


Under the revised MARPOL Annex VI, the term Sulphur Emission Control Area, or SECA, has been replaced with Emission Control Area, or ECA. This will allow for ECAs to specify limits not just for sulphur oxides (SOx), but also for particulate matter (PM), and  (NOx).




In  Emission Control Areas (ECAs) Sulphur limit in fuel used on board is 0.1% The interpretation of “fuel oil used on board” includes use in main and auxiliary engines and boilers. Exemptions are provided for securing the safety of the ship or saving life at sea, or as a result of damage to a ship or its equipment. Also, provisions for trials for ship emission reduction and control technology research provide for a time limited exemption.


Instead of limiting the sulphur content to 0.1% a scrubber can be used to reduce sulphur emissions to less than 20ppm

ECAs are:

the Baltic Sea area;

the North Sea area;

the North American area (covering designated coastal areas off the United States and Canada); the United States Caribbean Sea area (around Puerto Rico and the United States Virgin Islands).


Proposed new ECAs are  The Mediterranean, Singapore and around Australia.


Low and high sulphur fuel has to be stored in different tanks. Different grades of cylinder oils may have to be carried if operating with low sulphur fuel for any length of time to prevent excessive calcium deposits and resultant liner wear. If low sulphur fuels are used, high wear rates may be experienced with fuel injection equipment.


Ships using separate fuel oils entering or leaving an Emission Control Area must carry a written procedure showing how the fuel oil change-over is to be done, allowing sufficient time for the fuel oil service system to be fully flushed of all fuel oils exceeding the applicable sulphur content prior to entry into an Emission Control Area. The volume of low sulphur fuel oils in each tank as well as the date, time, and position of the ship when any fuel-oil-change-over operation is completed prior to the entry into an Emission Control Area or commenced after exit from such an area, shall be recorded in the Oil Record Book or approved log book..




Fuel Oil Quality


Although fuel oil quality is currently primarily a matter between owners/managers and suppliers, it will under Annex VI of MARPOL 73/78 also become a statutory matter. In addition to requirements limiting the sulphur content of oil fuel, Annex VI contains requirements preventing the incorporation of potentially harmful substances, and in particular waste streams (e.g. chemical waste), into fuel oils.


Bunker delivery notes must be kept on board for a minimum of three years and must contain the following information:

  • Name and IMO number of receiving ship

  • Bunkering Port

  • Date of commencement of bunkering

  • Name, address, and telephone number of marine fuel oil supplier

  • Product name

  • Quantity (metric tons)

  • Density at 15°C (kg/m3)

  • Sulphur content (% m/m)

A signed declaration from the the fuel oil supplier's representative that the fuel supplied has a sulphur level below 4.5% and that the fuel is free from inorganic acid and does not include any added substance or chemical waste which either jeopardises the safety of ships, adversely affects the performance of the machinery, is harmful to personnel, or contributes overall to additional air pollution is also required.


Samples must be taken by either a manual valve-setting continuous-drip sampler (shown opposite) a time-proportional automatic sampler, or a flow-proportional automatic sampler.


Samples must be kept on board for at least 12 months and the labels must contain the following information:

  • Location at which, and the method by which, the sample was drawn

  • Bunkering date

  • Name of bunker tanker/bunker installation

  • Name and IMO number of the receiving ship

  • Signatures and names of the supplier’s representative and the ship's representative

  • Details of seal identification

  • Bunker grade.


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