An Inventory of Hazardous Materials is not a certificate you obtain and file. Part I is a living record of what is physically in the ship, and it has to survive twenty years of repairs, retrofits and equipment swaps before anyone reaches a recycling yard.
What the Document Actually Is
The Hong Kong Convention entered into force on 26 June 2025, requiring ships of 500 gross tonnage and above to hold an approved Inventory of Hazardous Materials, with new ships covered at delivery and existing ships given until 25 June 2030 or their recycling date, whichever comes first. Those are the headline facts. What follows is the part that determines whether an operator actually complies.
The IHM has three parts, and confusing them is the commonest starting error. Part I lists hazardous materials contained in the ship’s structure and equipment, and it is developed at construction and maintained throughout the operational life. Parts II and III cover operationally generated wastes and stores respectively, and they are developed by the shipowner before recycling rather than carried from day one. Only Part I is a live obligation for a trading ship.
Part I is the only part that has to survive the ship’s whole life. It is also the only part that quietly stops being true the moment someone replaces a pump.
What Part I Contains, and What It Does Not
The current instrument is the 2023 Guidelines for the development of the Inventory of Hazardous Materials, adopted by IMO Resolution MEPC.379(80) on 7 July 2023, which superseded the 2015 Guidelines in MEPC.269(68) following the introduction of controls on cybutryne under the AFS Convention.
The Guidelines classify listed materials into tables. Tables A and B correspond to Part I; Table C corresponds to Parts II and III. Part I therefore captures what is built into the ship: asbestos, PCBs, ozone-depleting substances, anti-fouling compounds, heavy metals in coatings, cabling and gaskets, and similar materials fixed in structure and equipment.
Two concepts do most of the work. The homogeneous material is one that cannot be mechanically disjointed into different materials: a cable is not one material, since its sheath, intervention, insulator and conductor are each assessed separately. The threshold value is a concentration in that homogeneous material rather than in the component as a whole. This is why an IHM cannot be assembled from a parts list.
What Part I does not contain is loosely fitted equipment, which need not be listed there. Where such equipment remains aboard at recycling, it belongs in Part II instead. Getting this boundary wrong inflates Part I with items that will need maintaining for two decades and then have to be moved anyway.
How One Is Actually Built
Developing Part I proceeds in three steps, and the order can flex to suit a ship’s schedule.
1. Collect documentation. Material Declarations and Suppliers’ Declarations of Conformity are gathered from equipment makers and suppliers, along with drawings, specifications and certificates. For a newbuilding this is straightforward. For an existing ship it is frequently the hardest part, because suppliers have changed hands or disappeared.
2. Assess and plan. The documentation is assessed to identify where hazardous materials are known present, known absent, or unknown. The unknowns drive a visual and sampling check plan: what will be confirmed by eye, and what has to be sampled and analysed.
3. Survey, sample and compile. A trained expert conducts the onboard visual check and takes samples where the plan requires. Samples go to a laboratory for analysis against the threshold values. The results are compiled into Part I with the location and approximate quantity of each item.
Then certification. An initial survey verifies that Part I complies, and the flag Administration or a recognised organisation issues the International Certificate on Inventory of Hazardous Materials, valid for a period not exceeding five years.
The sampling step is where cost and credibility both sit. It is destructive, needs access to structure that may sit behind insulation or coatings, and depends on a competent laboratory. An IHM assembled from documentation alone, with no sampling where the documentation was silent, has recorded assumptions rather than findings.
The Part Operators Get Wrong
Here is the failure that will define the next decade. Part I must be kept up to date throughout the operational life of the ship. Every repair, every retrofit, every equipment replacement that introduces or removes a listed material changes the inventory, and the change has to be recorded. The Guidelines are explicit that where materials are added during maintenance, the applicable threshold values are applied and the addition recorded.
In practice a great many ships hold an IHM that was accurate on the day it was certified and untouched since. New pumps, replaced cabling, a coating changed at drydock, a retrofitted treatment system: each alters the document, and none alters it by itself.
An IHM that was true at delivery and never updated is not a compliant IHM. It is a historical record of a ship that no longer exists.
The pattern is familiar from firefighting maintenance plans and ballast water record books: the regulation creates a document, the document is produced once to obtain a certificate, and the discipline of maintaining it never gets built. Port State Control can verify certificate validity and the evidence beneath it, and failure is a detainable deficiency.
The workable answer is procedural rather than technical. Make IHM update a required step in the purchase and modification workflow, so that a new item of equipment cannot be signed off without its Material Declaration. Assign the task to a named role. And review the inventory at each drydocking, when the largest changes happen and the evidence is easiest to gather.
The Recycling End
When a ship is destined for recycling, three things must come together. The owner completes the inventory by adding Parts II and III to Part I. The chosen recycling facility develops a ship-specific Ship Recycling Plan. And the facility itself must hold a valid Document of Authorisation for Ship Recycling from its own authority.
A final survey then verifies Parts I, II and III together, and successful completion produces the International Ready for Recycling Certificate, valid for a period not exceeding three months. That short validity is deliberate: it is a window for delivering the ship to the yard, not a certificate to hold. On completion of recycling, a Statement of Completion is compiled and reported.
The integrity and cost questions that precede this are covered in our piece on late-life and decommissioning realities, which stops where a ship leaves service. This is what happens after.
Where the EU Regulation Bites Harder
For many operators the European regime is the binding constraint rather than the Convention. Regulation (EU) No 1257/2013 on Ship Recycling entered into force in December 2013 and applies controls modelled on the Hong Kong Convention with additions of its own.
The substance difference is the one that catches people. An inventory built to Convention requirements alone may be silent on materials the EU list covers, so a ship that later needs a Statement of Compliance faces additional survey work rather than a paperwork exercise. Where a vessel’s trading pattern includes EU calls, or might, building to the wider list from the outset is considerably cheaper than retrofitting the inventory.
None of this is difficult once the document is understood correctly: not a certificate obtained at delivery, but a record of what is in the ship, maintained by the people who change what is in the ship, for as long as it trades.
Frequently Asked Questions
What is the difference between IHM Parts I, II and III?
Part I lists hazardous materials contained in the ship’s structure and equipment. It is developed at construction and must be kept up to date throughout the operational life. Parts II and III cover operationally generated wastes and stores respectively, and are developed by the shipowner before the ship is recycled rather than maintained continuously. Only Part I is a live obligation for a trading ship.
How is an IHM Part I actually developed?
In three steps under the 2023 Guidelines (MEPC.379(80)): collecting Material Declarations and Suppliers’ Declarations of Conformity with drawings and specifications; assessing that documentation to separate known-present, known-absent and unknown materials, which produces a visual and sampling check plan; then the onboard check and sampling, with laboratory analysis against threshold values. An initial survey supports issue of the International Certificate on Inventory of Hazardous Materials, valid up to five years.
Does an IHM need updating after it is certified?
Yes, and this is the most commonly missed obligation. Part I must be maintained throughout the ship’s operational life, so every repair, retrofit or equipment change that introduces or removes a listed material has to be recorded, applying the relevant threshold values. An inventory that was accurate at certification and never updated does not reflect the ship, and port State control can verify both certificate validity and the evidence behind it.
How does the EU Ship Recycling Regulation differ from the Convention?
It reaches further. Since 31 December 2020 non-EU flagged ships of 500 GT and above calling at EU ports must hold an IHM Part I with a Statement of Compliance. EU-flagged ships comply under Article 5 and others under Article 12, the substance list adds materials beyond the Convention including PFOS and brominated flame retardants, and EU-flagged ships must be recycled at facilities on the European List.
Sources: IMO Hong Kong International Convention for the Safe and Environmentally Sound Recycling of Ships, 2009, in force 26 June 2025 (Inventory of Hazardous Materials, initial and final surveys, International Certificate on Inventory of Hazardous Materials, International Ready for Recycling Certificate, Ship Recycling Plan, and Document of Authorisation for Ship Recycling) · IMO Resolution MEPC.379(80), 2023 Guidelines for the development of the Inventory of Hazardous Materials, adopted 7 July 2023, superseding Resolution MEPC.269(68) following the introduction of cybutryne controls under Resolution MEPC.331(76) · Regulation (EU) No 1257/2013 on ship recycling, Articles 5 and 12, the Statement of Compliance and the European List of approved ship recycling facilities · IMO Resolution MEPC.331(76), amendments to Annex 1 of the AFS Convention, in force 1 January 2023
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