What is the Inventory of Hazardous Materials (IHM)?

Definition: What is the IHM?

The Inventory of Hazardous Materials (IHM) is a vessel-specific register of hazardous substances present in a ship’s structure, equipment and operational systems. The concept was introduced by the IMO’s 2009 Hong Kong International Convention for the Safe and Environmentally Sound Recycling of Ships (HKC) and codified by IMO Resolution MEPC.379(80) (2023 IHM Guidelines) and subsequent amendments including MEPC.405(83) (2025).

An IHM has three parts:

• Part I — Materials in ship structure or equipment. Maintained throughout the operational life of the ship.
• Part II — Operationally generated wastes. Prepared before the final survey for recycling.
• Part III — Stores. Prepared before the final survey for recycling.

The hazardous materials covered include substances listed in Appendix 1 (asbestos, ozone-depleting substances, polychlorinated biphenyls, anti-fouling system biocides such as cybutryne, brominated flame retardants and lead-based paints) and Appendix 2 (cadmium, hexavalent chromium, mercury, lead and other heavy metals). The EU Ship Recycling Regulation adds further substances, notably PFOS and certain perfluorinated compounds.

Who needs an IHM?

Following Hong Kong Convention entry into force on 26 June 2025, an IHM is required for:

• All ships of 500 GT and above on international voyages, regardless of flag.
• EU/EEA-flagged ships of 500 GT and above (already required since 31 December 2020 under EU Ship Recycling Regulation 1257/2013).
• Non-EU ships calling at EU/EEA ports if they are of 500 GT and above.

For new ships built on or after 26 June 2025, a verified IHM Part I must be on board at delivery. For existing ships, the certificate must be obtained at the first harmonised renewal survey on or after entry into force, in any event no later than 26 June 2030. Cyprus-flagged existing ships have a specific HKC trigger date of 26 February 2026.

For a flag-by-flag breakdown, see our IHM Compliance by Flag State Hub.

How is the IHM developed?

IHM Part I is developed in three steps:

1. Document collection. Material Declarations (MDs) and Suppliers’ Declarations of Conformity (SDoC) are gathered from equipment makers, paint suppliers and material vendors.
2. Visual and sampling check on board. Trained IHM Experts (e.g. Varuna Sentinels BV, accepted by the Liberian Registry and approved by RINA) inspect the vessel and take samples of suspect materials — insulation, gaskets, paints, cables — for laboratory analysis.
3. Compilation and verification. The expert compiles a complete IHM Part I document covering all hazardous-material entries with location, approximate quantity and source. The flag state’s Recognised Organisation (typically an IACS classification society) then verifies the IHM and issues the International Certificate on Inventory of Hazardous Materials (ICIHM).

Material Declarations issued on or after 26 June 2025 must follow the MEPC.405(83) format with a cybutryne threshold of 200 mg/kg (reduced from 1,000 mg/kg).

What does IHM maintenance involve?

IHM Part I is not a one-time exercise. It must be maintained continuously throughout the operational life of the vessel. Every event that introduces, removes or substitutes a hazardous material triggers an update obligation:

• Structural modifications (welding repairs, retrofits, conversions).
• Equipment replacement (pumps, separators, generators, refrigeration plant).
• Coating renewals and antifouling reapplications.
• Installation of new fuel systems (LNG, methanol, ammonia retrofits trigger material IHM Part I additions).
• Receipt of new Material Declarations from suppliers.

This is why the Varuna Sentinels VSIMS platform handles continuous IHM maintenance as an ongoing workflow rather than a survey-cycle event — pulling supplier MDs into the IHM automatically, flagging missing data and producing audit-ready evidence packs for Port State Control.

To check your fleet’s next deadline, use our free IHM Renewal Deadline Calculator.

How does IHM interact with HKC and the EU SRR?

The Hong Kong Convention (HKC) and the EU Ship Recycling Regulation (EUSRR, Regulation 1257/2013) are two parallel regimes that both require an IHM:

• HKC: in force globally since 26 June 2025. Applies by flag — every IMO Member State that has acceded enforces the convention on its flagged ships.
• EU SRR: applies by EU/EEA flag and by EU/EEA port call. Has a broader substance list than HKC (including PFOS and brominated flame retardants).

EU Implementing Decision 2026/116 introduced a unified ICIHM format covering both regimes — a single certificate, dual compliance. Ships flagged in EU/EEA Member States therefore now hold one certificate satisfying both HKC and EU SRR substance lists.

Read our deeper guides: What is the Hong Kong Convention? and What is the EU Ship Recycling Regulation?

What about Port State Control and penalties?

Failure to carry a valid ICIHM is a detainable deficiency at Port State Control. Since HKC entry into force, PSC regimes (Paris MOU, Tokyo MOU, USCG and others) have intensified IHM checks. Inspectors now go beyond confirming the certificate exists — they check the underlying survey reports, evidence of continuous maintenance, and consistency between IHM Part I content and visible on-board hazardous materials.

EU Member States are also implementing Directive (EU) 2024/1203 by 21 May 2026, introducing criminal liability for serious environmental offences including ship recycling violations. This raises the stakes meaningfully: detentions and operational disruption are no longer the worst outcome for non-compliant operators.