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Friday, September 21, 2018


Engines installed on ships constructed on or after 1 January 2000 or engines which undergo a major conversion on or after 1 January 2000 should meet the requirements of the Technical Code on Control of Emission of Nitrogen Oxides from Marine Diesel Engines (NOx Technical Code).

The NOx Technical Code was adopted at a conference held in September 1997 under the auspices of IMO. 

The Code was adopted at the same time as a new Annex VI, Prevention of Air Pollution from Ships, was added to MARPOL 73/78. 

Annex VI, when it comes into force, will set limits on sulphur oxide and nitrogen oxide emissions from ship exhausts and prohibit deliberate emissions of ozone-depleting substances. 

Regulation 13 of Annex VI sets limits for emission values of NOx, and the aim of the NOx Code is to establish mandatory procedures for the testing, survey and certification of marine diesel engines, in order to enable engine manufacturers, ship-owners and Administrations to ensure that all applicable marine diesel engines comply with the regulation. 

Although the regulation will not enter into force until Annex VI of MARPOL 73/78 enters into force, Administrations are encouraged to issue interim certificates confirming conformity with the NOx Technical Code for engines installed on ships on or after 1 January 2000, or for engines undergoing a major conversion on or after 1 January 2000. The aim is to ensure that new or modified engines will already be compliant with the NOx Code once it enters into force. 

IMO issued an MEPC Circular in November 1998, Interim Guidelines for the Application of the NOx Technical Code, which recommends that “Each engine which will become, retrospectively, subject to the provisions of regulation 13 of Annex VI of MARPOL 73/78 upon its entry into force, should be certified in accordance with the requirements of the NOx Technical Code.”

Annex VI of MARPOL 73/78 will enter into force 12 months after the date on which not less than 15 States, the combined tonnage of which shall be not less than 50% of the gross tonnage of the world's merchant shipping fleet, have become parties to the Protocol to MARPOL which contains Annex VI. To date, two countries have become Parties to Annex VI: Norway and Sweden. 

The Regulation 13 of Annex VI of MARPOL 73/78 – Nitrogen Oxides (NOX) and the Interim Guidelines for the Application of the NOXTechnical Code can be found at

[Source. IMO NEWS, No. 1: 2000]