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How will compliance with MARPOL Annex VI be determined? - Updated

SSM Roundel

Published: October 26, 2022

This article supersedes the article originally published in January 2020.

One of the questions that follows from the introduction of the Global Sulphur Cap is exactly how compliance is to be determined, what procedures will apply and what will be used to ascertain whether the operation of the ship and the bunkers carried on board are compliant. Whilst much will depend on the jurisdiction that is in force this article attempts to examine some of these questions in relation to vessels without scrubbers, or other equivalent means of compliance, by reference to the IMO Guidelines available.

At the 74th session of MEPC the IMO approved (i) 2019 Guidelines for Consistent Implementation of the 0.50% Sulphur Limit under MARPOL Annex VI and (ii) 2019 Guidelines for Port State Control. The purpose of the former Guidelines is for Administrations, Port States, shipowners, builders and fuel suppliers to use them to ensure consistent implementation of the 0.50% sulphur limit. The latter are intended to provide guidance on the conduct of Port State Control inspections for compliance with MARPOL Annex VI and afford consistency in the conduct of these inspections, the recognition of deficiencies and the application of control procedures.

In order to verify compliance, the Port State will carry out an initial inspection which will include, amongst other things:

  • Evidence of fuel delivered to and used on board the vessel
  • Vessel certification and its validity
  • Maintenance and other records required under MARPOL
  • Existence of required procedures, such as fuel change over procedures

If all certificates and documents are valid and in order and the overall observations of the Port State are favourable that should be the end of the matter.

However, where the observations give ‘clear grounds’ for believing that the condition of the ship or equipment does not correspond with the particulars of the certification or documentation a more detailed inspection will be carried out.

Although not exhaustive, the ‘clear grounds’ for a detailed inspection could include:

  • Missing or expired/invalid certificates,
  • Missing documents or records – for example fuel changeover procedures, MARPOL Annex VI record books,
  • Inconsistencies between the bunker delivery note and other documentation/certification,
  • Inconsistencies between the voyage plan and compliant fuel reserves on board,
  • Data from a remote or portable emission measuring device or receipt of information which would indicate that the ship may not be compliant

The full list of ‘clear grounds’ is set out in the guidance.

In accordance with the Guidelines, as part of their detailed inspection, the Port State will conduct a more in-depth review of onboard documentation and examine the operational procedures and familiarity of the crew with regard to, amongst other things, bunkering and change over procedures in connection with MARPOL Annex VI.

The most important part of this detailed investigation will of course be to check and verify whether fuel oil used by the ship complies with Regulation 14 of MARPOL Annex VI. For undertaking this analysis MARPOL VI stipulates three types of samples that can be collected by the PSCO for investigating and establishing non-compliance. The samples as per the amended MARPOL Annex VI given in resolution MEPC. 324(75) are: 

  • ‘MARPOL delivered sample’ is used to verify the sulphur content of fuel oil delivered to the vessel at the point of custody transfer. 
  • In-use sample -used to verify the sulphur content of fuel oil in the fuel system at the point of consumption in the specific machinery such as main engine, auxiliary engine, boiler etc.
  • Onboard sample -used to verify the sulphur content of fuel oil stored in the bunker tank.

Depending on the nature of the suspected breach of compliance the port state might require one or all of the above samples for analysis in order to establish the exact nature and location of breach.

Sampling guidelines

The procedures for the means of sample collection forms an important part of the analysis. The results of any analysis will only be as good as the sampling that has been undertaken. It is therefore important that due regard to the adoption of proper procedures and methodology is considered.

A MARPOL delivered sample’ which is representative of the delivered bunkers is generally to be collected as per IMO guidelines MEPC 182(59) “Guidelines for the sampling of fuel oil for determination of compliance with the Revised MARPOL Annex VI”. Where there is disagreement with the supplier on the location utilised for the sample a letter of protest should be issued. 

‘In-use’ and ‘on board sampling

The IMO has issued ‘2019 Guidelines for on board sampling for the verification of the sulphur content of the fuel oil used on board ships’ (MEPC.1/Circ. 864 Rev.1) setting out the number and location of ‘in-use’ sample points required on a vessel. 
These sampling points are required to be installed – 

  • For new ships, where the keel was laid on or after 01 Apr 2022 on delivery
  • For existing ships no later than the first IAPP renewal survey due after 01 Apr 2023.

The number and location of these sampling points will depend on the number of systems that fall within the requirements of MARPOL VI Regulations 14. The location and designation of the sampling points must be clearly marked in the engine room and correspondingly identified in the fuel oil piping diagram. 

For on-board fuel oil samples the ‘2020 Guidelines for on board sampling of fuel oil intended to be used or carried for use on board a ship’ (MEPC.1/Circ.889) has been issued by the IMO. This guideline makes provision for the collection of samples directly from the fuel oil storage tank and from the fuel oil transfer system downstream of the transfer pump.

It is recommended that consideration be given to installation and/or designation of sampling points prior to the effective date such as at the vessel’s next dry dock. This is to ensure Port State Control authorities are able to obtain ‘in-use’ and ‘on board’ samples only from designated and approved locations, in the event that they wish to investigate a possible non-compliance.

Any modifications undertaken to the fuel oil piping and storage systems to facilitate these sample collections must be appropriately approved and surveyed by the classification society. Upon completion of any modifications the supplement to the ship’s IAPP certificate is required to be updated. For further information reference is drawn to Class News 02/2022 issued by Class LR. 

Procedures for sample analysis

The Appendix VI of MARPOL Annex VI provides an agreed method for determining whether the fuel oil delivered to the vessel, in-use and carried on board is in accordance with MARPOL Annex VI. In addition to the procedure for the ‘MARPOL sample’, procedures have been included for the collection and analysis of ‘in-use’ samples from the vessel’s service system and ‘on board’ samples from the storage tanks.

Sampling and testing of the fuel is to be in accordance with Regulation 18.8.2 of MARPOL Annex VI, following the procedures set out in the amended Appendix VI (Verification Procedures for a MARPOL Annex VI fuel oil sample). Procedures under Part 1 are for the MARPOL delivered sample and Part 2 for the in-use and onboard sample.

When the samples have been taken by the authorities, as much detail as possible, such as the method adopted to collect the tank samples, seal numbers, adequacy of line clearing before collection etc must be recorded in the ship’s logbook for traceability. These details might prove useful in event of a dispute. In each case, where possible, a sealed sample, representative of that taken by the authorities, should also be retained on board.

The below table sets out the allowable sulphur m/m% limits in accordance with the amended Appendix VI:

Sample type Compliance limit per Reg. 14 Applicable limit
Marpol sample for ECA 0.1% m/m Sulphur Less than or equal to 0.10
Marpol sample 0.5% m/m Sulphur Less than or equal to 0.50
In-use or on-board sample for ECA 0.1% m/m Sulphur Less than or equal to 0.11
In-use or on-board sample 0.5% m/m Sulphur Less than or equal to 0.53


As can be seen, so far as the in-use/on-board samples are concerned fuel should be considered compliant if within 0.53%, incorporating a tolerance to account for repeatability and reproducibility.

Where suppliers are required to supply fuel oil that does not exceed the 0.5% m/m limit, it has been recommended by IMO in its Guidance on best practice for fuel suppliers (MEPC.1/Circ. 875 Add.1), that suppliers should consider the statutory limit minus 0.59R reproducibility i.e. a value of 0.47% m/m as a target limit during production.

A test certificate will be issued by the laboratory which, if fuel is found to be non-compliant, is then to be evaluated by the concerned Port State authority to determine the nature of control measures or penalties which might be applied. A copy of this certificate must be kept on board (MEPC 320(74) para


The Port State is required to consider all relevant circumstances and evidence when determining the appropriate control measures to be taken if non-compliance has been established. The vessel’s implementation plan may be taken into consideration. If non-compliance of the fuel oil is established the Port State will consider control measures in accordance with para of the MEPC 320(74).

Contingency measures for addressing non-compliant fuel oil MEPC.1/Circ.881 provides guidance to PSCOs on possible contingency measures in cases where non-compliant fuel oil remains on board a ship.

Depending on the circumstances and the judgment of the Port State, penalties may include significant fines, detention, an order to off-load non-compliant fuel and load compliant fuel sufficient for the voyage or permission to sail on a single voyage to procure compliant fuel oil (subject also to permission from the State of destination).

Members are encouraged to take note of the Port State Control Guidelines and review their MARPOL Annex VI applicable documentation and certification, and to verify that all records are being properly maintained up to date (including in accordance with Flag State requirements). Crews should be properly trained and made aware of the ‘clear grounds’ upon which detailed inspection and possible sampling will be considered.

On board blending of non-compliant fuel oil with compliant low sulphur fuel oil to avoid de-bunkering of the non-compliant fuel oil should not be undertaken. Such blending could result in compatibility and instability issues and void the bunker delivery note and the MARPOL representative sample. For further details reference is drawn to a recent publication by BIMCO on the topic at: Is on board fuel blending allowed? ( [subscription required]

A full review of the bunkering procedures should be undertaken, and specifically with reference to the guidelines for collection of a MARPOL representative sample as detailed in Resolution MEPC 182(59).

A periodic review of entries in the Oil Record Book, recording of fuel changeover, MARPOL representative sample and bunker delivery notes should be undertaken. The bunker delivery note must be issued by the supplier’s representative as per Appendix V of MARPOL Annex VI and must include a declaration that the sulphur content of the delivered fuel oil does not exceed a limit value % m/m. The retention period of the bunker delivery note is 3 years from the date of delivery of the fuel on board and the MARPOL representative sample must be retained until “the fuel oil is substantially consumed, but, in any case for a period of not less than 12 months from the time of delivery”. 

The on-board fuel changeover procedure should also be reviewed for any changes that might have been implemented in the fuel sampling procedures. It is recommended that the time required for flushing and change-over between fuel types should follow a recognised change over calculator such as those issued by Class Societies.  Samples should be taken to verify the timing of the changeover and that the appropriate fuel can be drawn from the sampling points. This is of particular significance where the vessel needs to regularly change over to low sulphur fuel such as for ECA compliance or where the vessel is unable to use the open loop scrubber system and needs to changeover to a low sulphur fuel oil.


Further reference is also drawn to the below links to the websites of the CIMAC guidelines on fuel oil testing:
 CIMAC Guideline – The Interpretation of Marine Fuel Analysis Test Results




MEPC.1-Circ.864-Rev.1 2019 Guidelines for on board sampling

MEPC.1-Circ.889 -2020 Guidelines for on board sampling of fuel oil

Class News 02/2022 MARPOL Annex VI – Fuel Oil Sampling Points

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