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The log · Service & process guides · 25 May 2026 · By Sherif Awad, Owner, GeoMarineHub
MARPOL Annex VI Explained: Air Pollution Rules Every Operator Must Know
MARPOL Annex VI governs air emissions from ships — sulphur, nitrogen oxides, and now greenhouse gases. A concise guide to what it covers, the certificates involved, and 2026 obligations.
MARPOL Annex VI Explained: Air Pollution Rules Every Operator Must Know
MARPOL Annex VI governs air emissions from ships — sulphur,nitrogen oxides, and now greenhouse gases. A concise guideto what it covers, the certificates involved, and 2026obligations.
Geomarine Marine Team
If IMO 2020 was the headline, MARPOL Annex VI is the rulebook behind it. This is the international convention chapter that governs air pollution from ships — and in 2026 it reaches well beyond sulphur into nitrogen oxides and, increasingly, greenhouse gases. Every operator trading internationally needs to understand what it requires.
What MARPOL Annex VI Covers
Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL) sets limits on the main air pollutants from ship exhaust and machinery. Its scope breaks into a few pillars:
—Sulphur oxides (SOx) — the 0.50% global cap and 0.10% ECA limit on fuel sulphur.
—Nitrogen oxides (NOx) — tiered engine emission standards (Tier I, II and the strict Tier III inside NOx ECAs).
—Ozone-depleting substances — controls on certain refrigerants and fire-fighting agents.
—Volatile organic compounds (VOCs) — particularly for tankers.
—Energy efficiency & greenhouse gases — EEXI, the SEEMP, and the operational CII rating.
NOx Tiers in Plain English
Marine diesel engines must meet NOx limits based on when the ship was built and where it operates. Tier I and II apply globally by build date; Tier III applies to newer engines operating inside designated NOx Emission Control Areas and demands roughly an 80% reduction versus Tier I — usually achieved with selective catalytic reduction (SCR) or exhaust gas recirculation (EGR).
The Certificate That Proves Compliance
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