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The IGC Code and what SIGTTO does

The IGC Code is the International Maritime Organization's mandatory code for ships carrying liquefied gases in bulk, and SIGTTO is the industry association whose operational guidance is treated as the practical standard alongside it.

Two different kinds of authority govern how an LNG carrier is built and run, and they work together rather than overlapping. One is law. The other is an industry standing on its own credibility.

The IGC Code: mandatory design rules

The International Gas Carrier Code is adopted under the SOLAS convention, which makes it binding on ships flying the flag of any country that has ratified it — in practice, essentially the whole world’s merchant fleet.

It governs the physical ship: containment system design and testing, hull material requirements at cryogenic temperature, the extent and performance of secondary barriers, cargo piping and valve arrangements, venting and pressure relief, gas detection, fire protection, and the separation of cargo systems from accommodation and machinery spaces.

Requirements scale with hazard. Ships are assigned a type based on the cargo they carry, and LNG — flammable, low flashpoint, carried at very low temperature — sits in the category demanding the most stringent containment and the greatest separation from other spaces on board. A ship built to carry a less hazardous cargo is permitted a simpler design; an LNG carrier is not.

Classification societies verify compliance during design and construction, and flag and port state authorities enforce it afterward through survey and inspection. It is, in the ordinary sense, law: a ship that does not meet it does not get a certificate, and a ship without a certificate does not trade.

What the Code does not cover

Design and construction, thoroughly. Day-to-day operation, only in outline.

The Code says a ship must have an emergency shutdown system; it says comparatively little about how two different ships and a terminal, each built to their own specifications, actually confirm they are compatible before connecting. It says a ship must be gas-free before certain work; it says less about the practical sequence and checks for getting there safely each time.

That gap is real, and it is filled by an organisation with no regulatory power at all.

SIGTTO: guidance that functions as law

The Society of International Gas Tanker and Terminal Operators is an association of the companies that actually run gas ships and terminals. It has no statutory authority and cannot fine anyone or withhold a certificate.

What it produces is detailed operational guidance, built from the collective experience of its members: how to plan a ship–shore compatibility study, how to conduct ship-to-ship transfer safely, how to manage cooldown and gassing up, how emergency response should be organised between a ship and a terminal that have never worked together before.

It functions as law in practice because the industry has made it so. Terminals require SIGTTO-compliant procedures as a condition of berthing. Charterers require it as a condition of hire. Insurers price risk against it. A ship or terminal that ignores SIGTTO guidance can be perfectly legal under the IGC Code and still unable to trade, because nobody in the industry will deal with it.

Why the split makes sense

The IGC Code changes slowly, deliberately, through an international treaty process, because it sets minimum design standards that every flag state must be able to enforce uniformly. That process is not built for updating operational best practice as experience accumulates.

SIGTTO can move faster because it answers to its own membership rather than to a treaty process, and because it is guidance rather than law it can be detailed and specific in a way a legal code generally cannot. The two together give the industry both a durable legal floor and a living operational standard, and neither one would work well doing the other’s job.

What this means for reading a vessel or terminal

Every ship in the carrier directory that has ever loaded a commercial cargo has been through IGC Code certification; that is a precondition of trading, not something this site can meaningfully add texture to. SIGTTO compliance is not something tracked in a public dataset at all — it is closer to trade credentialing than to a certificate, verified anew in every commercial relationship rather than recorded once. Neither appears as a field here, and neither should be assumed absent simply because it is not shown.

Common questions

Each answer stands on its own.

What is the IGC Code?
The International Gas Carrier Code, the International Maritime Organization's mandatory code for the design and construction of ships carrying liquefied gases in bulk, covering containment, materials, venting, cargo systems and crew protection.
Is the IGC Code the same for every ship?
No. Requirements are graded by cargo hazard, so an LNG carrier's flammable, low-flashpoint cargo puts it in the most stringent ship type category, with correspondingly higher standards for containment and secondary barriers.
What is SIGTTO?
The Society of International Gas Tanker and Terminal Operators, an industry association whose guidance on ship and terminal operations — mooring, cargo transfer, compatibility, emergency response — is followed as the practical standard even though it is not law.
Why does an industry body's guidance matter if it isn't mandatory?
Because the IGC Code sets design requirements but says little about day-to-day operations, and SIGTTO's guidance fills that gap. Terminals, charterers and insurers routinely require compliance with it as a condition of doing business.
Do all countries enforce the IGC Code the same way?
The Code itself is uniform under IMO conventions, but enforcement runs through each flag state and port state, so consistency in practice depends on how rigorously individual administrations apply it.

Last reviewed 2026-09-09.