Unified Interpretations


Unified Interpretations are adopted resolutions on matters arising from implementing the requirements of IMO Conventions or Recommendations. Such adopted resolutions can involve uniform interpretations of Convention Regulations or IMO Resolutions on those matters which in the Convention are left to the satisfaction of the Administration or vaguely worded.

Interpretations are circulated to Administrations concerned or are sent to IMO for information, as appropriate.


  1. IACS, as an international Non-Governmental Organization having observer status at IMO, works in co-operation with IMO in order to endeavour that regulations developed at IMO are clear, unambiguous and can easily be applied without the need of interpretations.
  2. However, interpretations may still be needed in cases where IMO regulations contain only functional requirements, allow alternative solutions to prescriptive requirements, are left to the satisfaction of Administrations or are generally or vaguely worded.
  3. The following Unified Interpretations (UIs) have been developed by IACS to assist the unified implementation of IMO regulations falling in the above-mentioned cases. It should be noted that the development of IACS Unified Interpretations (UIs) is not aiming at introducing additional requirements but at achieving uniform application of IMO regulations.
  4. IACS UIs are to be applied by IACS Societies to ships whose flag Administrations have not issued definite instructions on the interpretation of the IMO regulations concerned, in the course of statutory certification on behalf of those flag Administrations.

The technical backgrounds (development histories) of Unified Interpretations since 2004 can be found by following this link.

A list of the IACS working groups responsible for each Unified Interpretation may be found here.


FTP6 Testing and approval of pipe penetrations and cable transits for use in “A” class divisions (IMO FTP Code 2010 Annex 1 Part 3) Rev.1 July 2015


Liquified Gases in Bulk

UI GC1 Deleted

UI GC1 Deleted

UI GC2 New

UI GC2 Interpretation of the second sentence of paragraph 13.2.1 - 1977

UI GC3 Deleted

UI GC3 Deleted 1997

UI GC4 Deleted

UI GC4 Deleted 1997


UI GC5 Closing Devices for Air Intakes - Rev.1 February 2016


UI GC6 Cargo tank clearances - Rev.1 Feb 2016


UI GC7 Carriage of products not covered by the code - Rev.1 June 2016


UI GC8 Permissible stresses in way of supports of type C cargo tanks - Rev.1 June 2016

UI GC9 New

UI GC9 Guidance for sizing pressure relief systems for interbarrier spaces - 1988

UI GC10 New

UI GC10 Reliquefaction plant of moter-driven LNGcarriers - 1988

UI GC11 Rev1 CLN

GC11 Loading of cargo C tanks for ships constructed before 1 July 2016 and subject to IMO International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (MSC.5(48)) Rev.1 Feb 2016

UI GC12 Rev2 CLN

GC12 Secondary barrier testing requirements Rev.2 Aug 2015

UI GC13 Rev1 CLN

UI GC13 Examination before and after the first loaded voyage - Rev.1 March 2016

UI GC14 New

UI GC14 Pump Vents in Machinery Spaces (IGC Code Chapters 3.7.4 as amended by Res. MSC. 103(73) and IGC Code Chapters 3.7.5 as amended by Res. MSC. 370(93)) - April 2015

UI GC15 New

UI GC15 Closing Devices for Air Intakes - February 2016

Note: UI GC15 Rev 1 will come into force on 1 January 2018 and can be found in "Previous Revisions" 

UI GC16 New

UI GC16 Cargo tank clearances (on ships constructed on or after 1 July 2016) - March 2016

UI GC17 New

UI GC17 Unprotected openings - June 2016

UI GC18 New Corr1 CLN

UI GC18 - Test for cargo tank’s high level alarm - New Corr1 March 2017. Implementation date 1 January 2018.

Note: UI GC18 Rev.1 will come into force on 1 July 2018 and can be found in "Previous Revisions" 

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