MARPOL Annex VI • SOx / Sulphur Compliance

Sulphur & SOx Compliance Study Recap

A detailed TST infographic covering Regulation 14, SOx/PM ECAs, upcoming ECA areas, sulphur-restricted waters, fuel changeover, BDN evidence, scrubbers and MCA oral exam traps.

Reg. 14 0.50% / 0.10% ECA readiness

Global limit

0.50%

ECA limit

0.10%

Key law

Annex VI

Exam level

Chief

What this module tests

Sulphur compliance is not only remembering the percentage limit. A strong MCA oral answer links the legal limit, the trading area, the fuel actually being used, the bunker evidence chain, the changeover plan and any local scrubber restrictions.

State the global and ECA sulphur limits accurately.
List current, new and upcoming SOx/PM ECAs.
Explain the BDN, MARPOL delivered sample and PSC evidence chain.
Describe safe changeover from HFO/VLSFO to ECA fuel without damaging fuel pumps.
Explain EGCS equivalency, washwater monitoring and local open-loop restrictions.

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Reg. 14Core limits ECA listCurrent & upcoming TimelineDates to know ChangeoverSafe operation EvidenceBDN & samples EGCSScrubbers Restricted areasLocal rules FaultsWhat can go wrong Oral answerModel structure

Regulation foundation

MARPOL Annex VI Regulation 14

0.50%

Global sulphur limit

Outside SOx/PM ECAs, fuel oil used on board must not exceed 0.50% m/m sulphur unless an approved equivalent achieves the required emissions reduction.

0.10%

ECA sulphur limit

Inside a SOx/PM ECA, fuel oil used on board must not exceed 0.10% m/m sulphur unless an approved equivalent is used and permitted.

Reg. 4

Equivalency route

Scrubbers / EGCS are approved as equivalent arrangements under Regulation 4, not because the fuel itself is compliant.

MCA oral focus

Use the wording “fuel oil used on board.” Do not limit your answer only to main engine fuel or bunkered fuel. Boilers, auxiliaries and any fuel-consuming equipment must be considered.

Current & upcoming sea areas

SOx / PM ECA List

Established

Baltic Sea

Established SOx/PM ECA. 0.10% sulphur fuel or approved equivalent required.

Established

North Sea

Established SOx/PM ECA. Changeover must be complete before crossing the boundary.

Established

North American

SOx, PM and NOx ECA around designated US and Canadian coastal waters.

Established

US Caribbean

Covers waters around Puerto Rico and the US Virgin Islands; includes SOx/PM and NOx controls.

Live now

Mediterranean Sea

SOx ECA limit of 0.10% became effective on 1 May 2025.

Phase-in

Canadian Arctic

Designated under MEPC.392(82). 0.10% SOx/PM fuel requirement applies from 1 March 2027.

Phase-in

Norwegian Sea

Designated under MEPC.392(82). 0.10% SOx/PM fuel requirement applies from 1 March 2027.

Upcoming

North-East Atlantic

Adopted by IMO; entry into force 1 September 2027, with requirements taking effect 12 months later in 2028.

Common exam trap: giving only the old four ECAs is now outdated. Add Mediterranean, Canadian Arctic, Norwegian Sea and the adopted North-East Atlantic ECA.

Dates & phase-in

SOx Compliance Timeline

1 Jan 2020Global sulphur limit reduced to 0.50% outside ECAs.

1 May 2025Mediterranean Sea SOx ECA becomes effective at 0.10%.

1 Mar 2026Canadian Arctic and Norwegian Sea ECA amendments enter force.

1 Mar 2027Canadian Arctic and Norwegian Sea SOx/PM 0.10% requirement applies.

1 Sep 2027North-East Atlantic ECA enters into force.

2028North-East Atlantic ECA requirements take effect 12 months later.

North-East Atlantic scope

The adopted North-East Atlantic ECA covers EEZs and territorial seas, up to 200 nautical miles from baselines, of Greenland, Iceland, the Faroes, Ireland, the mainlands of the UK, France, Spain and Portugal.

Engineering operation

Fuel Changeover Into an ECA

Before entry

Identify the ECA boundary and ETA from the voyage plan.
Confirm enough compliant fuel for entry, stay, manoeuvring and reserve.
Calculate system volume and dilution time.
Start changeover early enough for the engine to receive 0.10% fuel before crossing.
Record date, time, position, tanks and quantities.

Machinery risks

Thermal shock from hot HFO/VLSFO to cooler MGO.
Fuel pump seizure from low-viscosity hot MGO.
Filter blockage from incompatible fuel blends.
Waxing/cold-flow problems in low-temperature waters.
Incorrect cylinder oil BN or feed-rate strategy.

Key rule

Boundary discipline

Changeover must be complete before entering the ECA. You do not begin the changeover at the boundary; the engine must already be supplied with compliant fuel.

Paper trail & sampling

BDN, MARPOL Sample & PSC Evidence

Item	Purpose	Retention / trap
BDN	Supplier declaration of fuel grade, quantity, density and sulphur content.	Keep for at least 3 years after delivery.
MARPOL delivered sample	Official representative sample taken during bunkering at the receiving ship’s manifold.	Keep under ship control for at least 12 months or until substantially consumed, whichever is later.
Fuel analysis	Independent lab evidence of sulphur, water, cat fines and other off-spec risks.	Compare to BDN and do not burn off-spec fuel for non-compliant operation.
Changeover log	Proof of completion before ECA boundary.	Record date, time, position, tank and quantities.
IAPP Certificate	Top-level Annex VI compliance certificate.	Supplement records approved arrangements and equivalent methods.
EGCS records	Proof of scrubber operation and equivalency.	SO₂/CO₂ data, alarms, washwater records, residues and maintenance.

PSC answer structure

Evidence chain = certificates + BDN + MARPOL sample + lab analysis + changeover records + tank soundings + EGCS data if fitted.

Equivalent compliance

EGCS / Scrubber Compliance

Open-loop

Uses seawater alkalinity to neutralise SOx. Efficient at sea, but often restricted in ports, rivers, fjords or coastal waters due to washwater discharge rules.

Closed-loop

Recirculates fresh/technical water and doses alkali, usually sodium hydroxide. Produces residues and requires chemical safety management.

Hybrid

Can operate open-loop where permitted and closed-loop where discharge restrictions apply, provided the system is correctly managed and approved.

Proof of SOx equivalency

The key operational proof is the SO₂/CO₂ exhaust ratio, supported by alarms, monitoring data and approved EGCS documentation.

Washwater monitoring

Key parameters include pH, PAH and turbidity. Residues/sludge must be retained and disposed of to approved reception facilities.

Beyond IMO ECAs

Sulphur Restricted Areas & Local Rules

Why local rules matter

IMO ECAs are not the full compliance picture. Ports, coastal states and regional authorities may impose separate fuel-use or open-loop washwater discharge restrictions.

EU port / at-berth sulphur requirements.
California ocean-going vessel fuel rules.
China domestic emission control areas.
Singapore port-water scrubber discharge restrictions.
Norwegian fjord and local washwater restrictions.

Chief Engineer action

Check Flag and company circulars.
Check port authority and coastal-state notices.
Confirm charterer instructions do not conflict with law.
Confirm EGCS operating mode before arrival.
Record compliance actions and fuel/mode changes.

Do not say: “The ship has a scrubber, so it can always burn high-sulphur fuel.” Local open-loop discharge restrictions can force closed-loop operation or compliant fuel use.

Failure scenarios

Oral Exam Fault Traps

Scenario	Immediate risk	Correct response
Changeover late	Non-compliant fuel at engine inside ECA.	Take corrective action, notify internally, complete changeover safely, preserve records, follow reporting procedure.
MGO too hot	Low viscosity, loss of pump lubrication, pump seizure.	Use MGO cooler / temperature control and comply with maker viscosity limits.
Fuel incompatible	Sludge, filter blockage, loss of propulsion.	Segregate fuels, use spot test/lab data, manage changeover carefully.
EGCS failure	Loss of equivalent compliance while burning high-sulphur fuel.	Rectify, record, notify as required, and switch to compliant fuel if equivalency cannot be maintained.
Open-loop banned	Illegal washwater discharge.	Use closed-loop mode if available or burn compliant fuel before entering restricted waters.
Off-spec sulphur result	Potential MARPOL breach.	Segregate, do not burn for non-compliant operation, inform company/supplier, preserve evidence, plan disposal/de-bunkering.

Exam-ready structure

Model MCA Oral Answer

“How do you comply with sulphur limits?”

State MARPOL Annex VI Regulation 14.
State 0.50% global and 0.10% ECA limits.
Identify whether the voyage enters any current/upcoming ECAs.
Use compliant fuel or an approved EGCS equivalent.
Plan and complete changeover before the boundary.
Record date, time, position, tank and quantities.
Keep BDNs, samples, analysis and IAPP evidence.
Check local port/coastal-state sulphur and scrubber restrictions.

High-level answer points

Do not confuse Reg. 14 sulphur limits with Reg. 18 fuel quality/documentation.
Do not confuse SOx ECAs with NOx Tier III engine requirements.
Do not assume scrubber use is accepted in every port or coastal area.
Do not say changeover starts at the ECA boundary.
Do not forget the Mediterranean, Canadian Arctic, Norwegian Sea and North-East Atlantic updates.

Final one-line memory aid

Law → Area → Fuel/EGCS → Changeover → Evidence → Local restrictions → Machinery safety.

Reference basis

Accuracy & Source Notes

IMO Regulation 14 and Mediterranean SOx ECA update: global 0.50%, ECA 0.10%, Mediterranean effective 1 May 2025.
IMO MEPC update: North-East Atlantic ECA adopted, entry into force 1 September 2027, requirements in 2028.
Lloyd’s Register statutory update: Canadian Arctic and Norwegian Sea SOx ECAs require 0.10% from 1 March 2027.
Course content cross-checked against the TST Sulphur/SOx quiz and flashcard module.

Local scrubber/washwater restrictions change frequently. For live voyage planning, always check the latest Flag, port, coastal-state and company circulars before arrival.