IACS Recommendation 202: New Safety Standards for Ammonia and Hydrogen Ships

For Logisticswall, I would position this as more than a technical safety announcement. The important development is that shipping's transition to ammonia and hydrogen is beginning to move from fuel selection towards the engineering standards needed to operate these fuels safely.

One important distinction: ammonia presents a serious toxicity risk, while hydrogen presents a major fire and explosion risk because of its wide flammability range and low ignition energy. Both require carefully designed containment, ventilation, detection and emergency-response systems.

The IACS announcement confirms that Recommendation 202 was published on 12 November 2026. The IMO had already approved interim safety guidelines for hydrogen and ammonia cargo used as fuel at MSC 111 in May 2026.

Beyond the Fuel: IACS Moves to Address the Invisible Risks of Future-Fuel Ships

MARITIME SAFETY | ALTERNATIVE FUELS | REGULATORY DEVELOPMENT

The shipping industry's transition towards cleaner fuels is bringing a new set of safety challenges. While ammonia and hydrogen are attracting attention as potential marine fuels, their accidental release could create serious risks for vessels, crew and surrounding operations.

Addressing this challenge, the International Association of Classification Societies (IACS) published Recommendation 202 (Rec. 202) on 12 November 2026, establishing a common technical approach to gas dispersion analysis for ships using ammonia and hydrogen as fuel.

Understanding the risk before it becomes an accident

A gas leak aboard a vessel is not simply a matter of detecting the release. The critical question is where the gas will travel, how quickly it will spread and whether it could enter machinery spaces, accommodation areas or air-intake systems.

The risks differ between the two fuels:

• Ammonia: Highly toxic. A release can expose crew to dangerous concentrations, even without ignition.

• Hydrogen: Highly flammable, with a low ignition energy. Accumulation in confined or poorly ventilated spaces can create fire and explosion hazards.

IACS Recommendation 202 establishes expectations for modelling both toxicity and flammability, including the selection of release scenarios, environmental conditions, model validation and the technical competence of specialists conducting the assessments.

What changes in ship design?

The findings of these studies can directly influence several engineering decisions:

• Vent mast positioning: Preventing released gas from reaching accommodation spaces and air intakes.

• Gas detection: Identifying appropriate locations for detectors.

• Ventilation: Ensuring potentially dangerous concentrations do not accumulate.

• Hazardous areas: Defining zones where special equipment and operational precautions are necessary.

• Emergency response: Identifying areas that may become unsafe under different release and weather conditions.

This makes gas dispersion analysis an important part of the ship-design process, rather than an assessment conducted only after the vessel is built.

The regulatory picture: IMO and IACS

The development comes as the IMO strengthens its safety framework for alternative marine fuels.

At its 111th Maritime Safety Committee session in May 2026, the IMO approved interim safety guidelines for hydrogen-fuelled ships and ships using ammonia cargo as fuel. These address fuel-specific safety requirements where existing regulations need further development.

The IGF Code remains the wider international framework for ships using gases and other low-flashpoint fuels. However, it does not yet contain detailed prescriptive requirements covering all the specific hazards associated with ammonia and hydrogen.

IACS Rec. 202 adds technical guidance to support this developing framework.

What this means for the shipping industry

The significance of Rec. 202 goes beyond another technical recommendation.

Shipowners, shipbuilders, equipment manufacturers, classification societies and flag administrations now have a more consistent basis for evaluating gas-release scenarios and their consequences.

It could also influence future newbuilding specifications, engineering costs, equipment selection and approval processes for alternative-fuel vessels.

Importantly, Rec. 202 is a technical recommendation, not a new mandatory IMO convention or an amendment to the IGF Code. Its value lies in harmonising the technical approach used in safety assessments.

A necessary step before alternative fuels scale

IACS established its Safe Decarbonisation Panel in 2022, bringing together expertise from across the maritime industry. According to IACS Secretary General Robert Ashdown, Rec. 202 is the first output of its collaborative framework involving flag States and industry organisations.

The industry's challenge is no longer simply identifying fuels that can reduce emissions. It must also demonstrate that those fuels can be stored, transferred and used safely at sea.

The success of alternative-fuel shipping will depend not only on the fuel's environmental performance, but also on the industry's ability to control the risks it introduces.