Marine fuel sulphur is capped at 0.50% by mass worldwide and 0.10% inside an Emission Control Area, under regulation 14 of MARPOL Annex VI. What catches ships out is rarely the limit itself. It is that three different samples are judged against two different thresholds.
The two limits, and where each one applies
| Where | Limit | Since |
|---|---|---|
| Worldwide, outside an ECA | 0.50% m/m | 1 January 2020 |
| Inside an Emission Control Area | 0.10% m/m | 2015 for the original areas |
The 2020 step down from 3.50% to 0.50% is what the industry calls IMO 2020, and it remains the single largest fuel change the sector has been through (IMO). Which areas carry the 0.10% limit, and from when, is set out here.
A ship can meet the limit two ways: burn compliant fuel, or use an approved equivalent such as an exhaust gas cleaning system. The obligation is the emission, not the fuel in the tank.
Three samples, two thresholds, and this is where ships get caught
Regulation 14 is tested through samples, and the amended Appendix VI sets out how (MEPC.1/Circ.882). There are three, and they do not carry the same threshold.
| Sample | Where it comes from | Threshold applied |
|---|---|---|
| MARPOL delivered sample | Sealed at bunkering, signed by both parties | 0.50%, no allowance |
| In-use sample | Drawn from the fuel oil service system | 0.53% |
| On board sample | Drawn from a storage tank | 0.53% |
A fuel that fails at 0.51% on the delivered sample can pass at 0.51% on an in-use sample. Same number, different sample, different outcome.
Why 0.53% and not 0.50%
The gap is not leniency. It is measurement science.
Test methods have a reproducibility, meaning two competent laboratories testing the same fuel will not return an identical number. The verification procedure accounts for that: an in-use or on board sample is deemed to meet the requirement provided the laboratory result does not exceed the specification limit plus 0.59R, where R is the reproducibility of the method under ISO 4259 (IBIA). Applied to the 0.50% limit, that produces the 0.53% figure.
The delivered sample gets no such allowance, and the reason is logical. It tests what the supplier sold you, under controlled conditions, against a contractual specification. The in-use sample tests what is in a running system that may still hold traces of a previous grade.
This distinction is the single most useful thing to understand about sulphur enforcement, and it is also why the sampling procedure at bunkering matters so much (Britannia P&I). Four sealed samples leave every bunkering operation, and only one of them is the regulator’s.
Which grade meets which limit
The limits are what the regulation says. The grades are what a supplier actually offers, and the mapping is worth knowing before you nominate a stem.
| Grade | Sulphur | Where it is compliant |
|---|---|---|
| HSFO, high sulphur fuel oil | Above 0.50% | Only with an approved exhaust gas cleaning system |
| VLSFO, very low sulphur fuel oil | At or below 0.50% | Worldwide outside an ECA |
| ULSFO, ultra low sulphur fuel oil | At or below 0.10% | Inside an ECA |
| MGO and MDO, distillates | Typically at or below 0.10% | Inside an ECA, and widely used for manoeuvring |
| LNG, methanol and biofuel blends | Effectively negligible sulphur | Both, subject to their own handling rules |
The quality specification behind those grades is ISO 8217, whose seventh edition was published on 30 May 2024. A delivery note citing the 2017 edition is quoting a superseded standard, which matters when a fuel quality dispute turns on what was contractually promised.
Note that a VLSFO delivered at 0.49% leaves almost no margin. Blending variability is real, and the difference between a comfortable 0.42% and a marginal 0.49% is the difference between a routine inspection and an argument about test tolerances.
What happens when compliant fuel is not available
Regulation 18 anticipates that a ship may reach a port where compliant fuel cannot be obtained. In that case the ship notifies its flag state and the port of destination, and records the attempts made to obtain it. That record is commonly called a fuel oil non availability report.
It is not a waiver. It is evidence, and it is judged on whether the effort to obtain compliant fuel was genuine and documented at the time rather than reconstructed afterwards.
The limit has not moved since 2020, but the enforcement has
Five years on, the 0.50% figure is settled and the scrutiny has shifted to the evidence chain around it.
- Port state control increasingly checks the bunker delivery note, the retained sample and the changeover record together, not the fuel in isolation
- The same fuel data now feeds FuelEU Maritime and EU ETS, where an inconsistency is not a deficiency but a cost
- Fuel quality disputes and sulphur exceedances tend to surface weeks after delivery, when the ship is elsewhere and the documentation is all that survives
Regulation 14 sits inside a wider set of obligations that all draw on the same source: what was delivered, when, and who signed for it.
VesselChain records each delivery once, at the point of delivery, signed by the accredited verifier the regulation already requires. The sulphur figure a port state officer reads and the figure your compliance balance is built from become the same record instead of two reconstructions. What that means if you operate the vessel is here.
Frequently asked questions
What is the marine fuel sulphur limit?
0.50% by mass worldwide since 1 January 2020, and 0.10% by mass inside an Emission Control Area. Both are set by regulation 14 of MARPOL Annex VI.
What is regulation 14 of MARPOL Annex VI?
Regulation 14 limits sulphur oxides and particulate matter by capping the sulphur content of fuel oil used on board, and it allows compliance through an approved equivalent such as an exhaust gas cleaning system.
Why is the limit sometimes quoted as 0.53%?
Because in-use and on board samples are judged against the specification limit plus an allowance for test method reproducibility under ISO 4259. That produces 0.53% for a 0.50% limit. The MARPOL delivered sample carries no such allowance and is judged at 0.50%.
What is the difference between the delivered sample and an in-use sample?
The delivered sample is sealed at bunkering and signed by both parties, and tests what the supplier provided. The in-use sample is drawn from the fuel oil service system and tests what the ship is actually burning. They carry different thresholds.
Can I still burn high sulphur fuel oil?
Only with an approved equivalent such as an exhaust gas cleaning system, and only where the port state accepts that arrangement. Without one, fuel above the applicable limit may not be used.
What happens if compliant fuel is unavailable?
The ship notifies its flag state and the port of destination and records the attempts made to obtain compliant fuel. This is evidence of genuine effort, not an exemption, and it is judged on documentation made at the time.
