MARPOL Annex VI — Prevention of Air Pollution
The full map of Annex VI: the three NOx Tiers of Regulation 13, the SOx and particulate matter ECAs of Regulation 14 and the NOx ECAs that are a different thing, ODS, VOCs, incineration, fuel quality and energy efficiency (EEXI, CII, DCS) — updated to 2026.
Operational Explanation
MARPOL Annex VI governs the prevention of air pollution from ships: sulphur oxides (SOx) and fuel quality, nitrogen oxides (NOx), ozone-depleting substances (ODS), volatile organic compounds (VOCs), on-board incineration, and — from Chapter 4 — energy efficiency and greenhouse gas emissions (EEDI, EEXI, SEEMP, CII, IMO DCS).
This topic is the cross-cutting reference that the module's individual operational procedures (Fuel Oil Changeover, Incinerator Operations) point back to: the full regulatory picture is here, the step-by-step practical procedure is there.
NOx: Regulation 13 and the three Tiers
Regulation 13 applies to “each marine diesel engine with a power output of more than 130 kW installed on a ship” and to every engine above that threshold undergoing a major conversion on or after 1 January 2000. The limits are expressed as a total weighted cycle emission, in g/kWh of NO₂ equivalent, and depend on n, the rated engine speed (“rated engine speed, crankshaft revolutions per minute”). The figures below are those of the convention text, given in their original form:
| Tier | n < 130 rpm | 130 ≤ n < 2000 rpm | n ≥ 2000 rpm | Applies to |
|---|---|---|---|---|
| Tier I | 17.0 g/kWh | 45 · n(-0.2) g/kWh | 9.8 g/kWh | ships constructed on or after 1 January 2000 and prior to 1 January 2011 |
| Tier II | 14.4 g/kWh | 44 · n(-0.23) g/kWh | 7.7 g/kWh | ships constructed on or after 1 January 2011 — and it is the level that applies everywhere outside Tier III areas |
| Tier III | 3.4 g/kWh | 9 · n(-0.2) g/kWh | 2.0 g/kWh | only while the ship is operating inside a NOx Tier III emission control area, and only if constructed on or after that area's own date |
Tier III is not a level the ship carries with her: it is a geographical obligation. The same ship that must stay at 3.4 g/kWh inside the area answers to Tier II outside it. That is what makes the distinction in the next paragraph decisive.
Exclusions. Regulation 13 does not apply to engines intended solely for emergencies, nor to engines installed in lifeboats, nor to engines on ships engaged solely on voyages within waters under the sovereignty or jurisdiction of the flag State, provided the engine is subject to an alternative NOx control measure established by the Administration. Excluded from Tier III only are, in addition, recreational craft of less than 24 metres in length specifically designed and used solely for recreation, and ships with a combined nameplate propulsion power of less than 750 kW that demonstrate to the Administration that they cannot comply because of design or construction limitations. There is finally a regime of its own (Reg. 13.7) for engines with a power output of more than 5000 kW and a per-cylinder displacement at or above 90 litres installed on ships constructed on or after 1 January 1990 and prior to 1 January 2000: for those, where certified, an Approved Method applies.
“ECA” is not one single thing: Regulation 14 for SOx and particulate matter, Regulation 13 for NOx
This is the confusion that derails a voyage plan. Annex VI has two lists of areas, in two different Regulations, with different perimeters and different dates. Regulation 14 — whose full title is “Sulphur oxides (SOx) and particulate matter” — lists the areas where the 0.10% m/m sulphur limit applies. Regulation 13 separately lists the “NOx Tier III emission control area”. An area may sit in one list, in the other, or in both.
| Area | Regulation 14 — SOx and PM | Regulation 13 — Tier III |
|---|---|---|
| Baltic Sea | yes | yes, ships constructed on or after 1 January 2021 |
| North Sea | yes | yes, ships constructed on or after 1 January 2021 |
| North America | yes | yes, ships constructed on or after 1 January 2016 |
| United States Caribbean Sea | yes | yes, ships constructed on or after 1 January 2016 |
| Mediterranean Sea | yes — 0.10% limit from 1 May 2025 | no |
| Canadian Arctic | yes — limit from 1 March 2027 | yes, ships constructed on or after 1 January 2025 |
| Norwegian Sea | yes — limit from 1 March 2027 | yes, three-date criterion running from 1 March 2026 |
| North-East Atlantic | yes — limit from 1 September 2028 | yes, three-date criterion running from 1 January 2027 |
It is not correct to say that the Mediterranean is an ECA for sulphur only: the Regulation 2 definition knows three combinations, not four, and names them thus: “air pollution from NOx or SOx and particulate matter or all three types of emissions”. SOx and particulate matter travel together, always. Every Regulation 14 area is an ECA for sulphur AND for particulate matter, the Mediterranean included; the official name of the Mediterranean area is in fact “Mediterranean Sea Emission Control Area for Sulphur Oxides and Particulate Matter”. The real difference is another: the Mediterranean is the only area that sits on the Regulation 14 list and not on the Regulation 13 one.
One fact surprises anyone looking for a number: Annex VI sets no numerical limit for particulate matter. PM appears in the title of Regulation 14, in the Regulation 2 definition and in the designation criteria, but it has neither g/kWh nor mg/m³. It is controlled indirectly, through the sulphur content of the fuel or an equivalent means approved under Regulation 4. The contrast with NOx is sharp: there the numbers exist, and they are those in the table above.
Main developments 2025–2027: Mediterranean SECA — amendments in force since 1 May 2024, the 0.10% limit applicable from 1 May 2025 (Resolution MEPC.361(79)); new BDN/IMO DCS granularity rules from 1 August 2025 (Resolution MEPC.385(81)); revised SEEMP Part II for the new granularity and its own Confirmation of Compliance (Reg. 5.4.5) on board from 1 January 2026; new Canadian Arctic and Norwegian Sea ECAs from 1 March 2026 (Resolution MEPC.392(82)); the IMO Net-Zero Framework, whose draft amendments were approved at MEPC 83 (April 2025) and circulated for adoption, but not adopted: the extraordinary session of October 2025 adjourned the decision by twelve months, and the resumed extraordinary session is scheduled for 4 December 2026, immediately after MEPC 85 (30 November–3 December 2026). Until adoption there is no entry-into-force date: under MARPOL tacit acceptance, entry into force would in any case follow adoption by roughly sixteen months, the same arithmetic applied to the ECAs above.
Regulatory Reference
MARPOL Annex VI — main structure: Reg. 1-3 (application), Reg. 2 (definitions), Reg. 5-11 (survey and certification, IAPP/EIAPP), Reg. 12 (ODS), Reg. 13 (NOx: Tier I, II and III, the NOx Technical Code 2008 made mandatory by the Regulation itself, and the list of NOx Tier III emission control areas at par. 6), Reg. 14 (SOx and particulate matter, fuel quality, list of ECAs at par. 3; since 1 March 2020, under Res. MEPC.305(73), the global 0.50% m/m limit applies to fuel oil “used or carried for use on board”, hence also to fuel merely held on board for use; the 0.10% ECA limit of Reg. 14.4 remains framed on fuel “used on board” only), Reg. 15 (VOCs), Reg. 16 (incineration), Reg. 18 (fuel quality and Bunker Delivery Note), Chapter 4 (EEDI, EEXI, SEEMP, CII, IMO DCS).
Scope of Application
Applies to all ships subject to MARPOL, with requirements differentiated by tonnage/type (e.g. EEXI for ships of 400 GT and above of the EEDI ship types (Reg. 25) and CII for ships of 5,000 GT and above (Reg. 28) — two different thresholds, not one; IAPP certification for ships of 400 GT and above on international voyages).
Procedure / How to Complete It
- Verify the certificate class required (IAPP for the ship, EIAPP for each diesel engine subject to Reg. 13) and its survey validity/expiry.
- Check the planned navigation area against the Regulation 14 ECAs where the fuel limits already apply (North America, US Caribbean, Baltic, North Sea, Mediterranean from 1 May 2025) and arrange compliant fuel/EGCS. The Canadian Arctic and the Norwegian Sea are designated from 1 March 2026, but the SOx/PM limits apply there from 1 March 2027. Check the tanks as well: since 1 March 2020 (Res. MEPC.305(73)) the global 0.50% m/m limit applies to fuel oil “used or carried for use on board”, so not burning it is not enough — fuel above 0.50% cannot be held on board for use.
- Run a second, separate check on the NOx Tier III emission control areas of Regulation 13: the list does not coincide with the Regulation 14 one and the relevant construction dates differ area by area. If the ship falls outside the area's construction date she stays at Tier II inside that area and need do nothing more; if she falls within it, Tier III must be met for the whole time she operates there.
- Verify the Bunker Delivery Note for every bunkering operation and retain it together with the MARPOL sample for the required period.
- Verify that the revised SEEMP Part II and its own Confirmation of Compliance (Reg. 5.4.5) are on board from 1 January 2026 and align IMO DCS data with the new granularity.
- Monitor the evolution of the IMO Net-Zero Framework (resumed extraordinary session on 4 December 2026, after MEPC 85) for medium-term CII/EEXI planning, without assuming any entry-into-force date before adoption.
Practical Example
The two SECAs do not touch. The Mediterranean ends at the western entrance to the Strait of Gibraltar, on a line joining Cape Trafalgar and Cape Spartel. The North Sea begins, to the west, only at “the English Channel and its approaches eastwards of longitude 5° W and northwards of latitude 48°30' N”. In between lie the Gulf of Cadiz, the Iberian Atlantic coast and the Bay of Biscay: waters where the global 0.50% m/m limit applies today, not 0.10%.
So the route has two transitions, not one: out of the SECA at Gibraltar and back into a SECA at the western approaches to the English Channel. Plan it as if it were all ECA and you buy low-sulphur fuel for a leg that does not require it; plan it as if it were all outside and you reach the Channel without any. Correct planning provides for two changeovers and counts the miles of each leg.
The picture will change, but not yet: the North-East Atlantic ECA (Res. MEPC.407(84)) enters into force on 1 September 2027 and its SOx limits apply from 1 September 2028. From that date the corridor closes and the route really does become continuous at 0.10%. In the window between the two dates the area is an ECA in full for NOx Tier III, but for sulphur the two transitions remain.
What Typically Goes Wrong
Common Mistakes Mistake Library
| Mistake | Consequence | How to avoid it |
|---|---|---|
| Voyage planning not updated with the ECA designation date used as the fuel obligation date (Canadian Arctic and Norwegian Sea: designated 1 March 2026, SOx/PM limits 1 March 2027) | Use of non-compliant fuel in an area now regulated as a SECA | Update charts and voyage planning procedures with every new MEPC resolution entering into force |
| Expired IAPP certificate or missing EIAPP for a modified engine | PSC deficiency, possible detention | Track survey deadlines in a dedicated register and coordinate Annex VI surveys with other statutory surveys |
| SEEMP Part II not updated or incomplete IMO DCS data against the new required granularity | Non-compliance in data collection and possible knock-on effects on CII rating | SEEMP Part II has no expiry the way a certificate does, but its revision for the new granularity does have a date: the Part II Confirmation of Compliance (Reg. 5.4.5) is to be kept on board from 1 January 2026 |
| The Regulation 14 ECA list also used to decide where NOx Tier III applies | Tier III assumed where it is not due (Mediterranean) or not arranged where it is | Keep two separate lists in passage planning: the Regulation 14 SOx/PM ECAs and the Regulation 13 NOx Tier III emission control areas |
| Mediterranean → Northern Europe route planned as if it were entirely a SECA | Low-sulphur fuel burned needlessly on the Atlantic leg, or missing on entering the English Channel | Count the two transitions: out of the SECA at Gibraltar, back in at 5° W / 48°30' N. The leg in between will be an ECA only from 1 September 2028 |
What the PSCO Checks
Operational Tips
- Keep two tables, not one: the Regulation 14 ECAs for SOx and particulate matter and the Regulation 13 NOx Tier III emission control areas, each with its own dates. The lists do not coincide.
- On each engine's EIAPP check which Tier it is certified to: Tier III is owed only inside the area and only if the ship falls within that area's construction date.
- Coordinate Annex VI certificate deadlines (IAPP/EIAPP) with the ship's general survey calendar.
- Follow regulatory updates (Regulatory Updates section) to avoid being caught unprepared by new MEPC resolutions, including the evolving IMO Net-Zero framework.
Preparation checklist
Educational checklist. This summary supports learning and preparation only. It does not replace the vessel’s approved procedures, manuals, statutory documents, company SMS, or applicable official requirements. Completing it demonstrates neither compliance nor readiness for an inspection: it shows that a list has been read, not that the ship is in order. Always verify the current documents carried on board.
- IAPP certificate valid and consistent with the ship's current configuration
- EIAPP certificates present for all engines subject to Reg. 13
- Regulation 14 ECAs on the planned route identified and compliant fuel/EGCS arranged
- NOx Tier III emission control areas on the route checked separately, each against its own construction date
- No fuel oil above 0.50% m/m sulphur held on board for use (Reg. 14.1 carriage ban, since 1 March 2020)
- Bunker Delivery Notes and MARPOL samples correctly filed
- SEEMP Part II updated and IMO DCS data aligned with current requirements
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Last substantive revision of this page: 19 August 2026 · page fingerprint 87f22dffb392