Every superyacht of 500 GT and above now carries the same obligation: a certified, maintained Inventory of Hazardous Materials. Since the Hong Kong Convention entered into force on 26 June 2025, that requirement is global, not just European. This guide explains what an IHM actually is, which vessels are in scope, and what "maintaining" one means in practice on a working yacht.
It is written for the people who carry the responsibility day to day — the Designated Person, the Captain, and the Chief Engineer — not for recycling yards. Where a point depends on your specific flag or class, we say so, and the right first call is named.
What an IHM is
An Inventory of Hazardous Materials (IHM) is a documented list of the hazardous materials present in a vessel's structure, equipment, operational waste, and stores. It exists so that, across a ship's whole life and ultimately at recycling, the hazardous materials on board are known and can be managed safely.
The controlled substances are defined in the Convention's annexes and include asbestos, polychlorinated biphenyls (PCBs), ozone-depleting substances, and anti-fouling compounds containing organotin (TBT), among others. The operative document for an operational yacht is the certificate confirming the inventory exists, is accurate, and is being kept up to date.
The current technical reference for how an IHM is developed and maintained is the 2023 IHM Guidelines, adopted by the IMO as resolution MEPC.379(80) (as subsequently amended). Your class society works to these guidelines when it surveys your inventory.
Which yachts need one
Two instruments drive scope, and they are scoped differently:
- The Hong Kong Convention (HKC) — applies to ships of 500 GT and above on international voyages, regardless of flag or build year, for States that are party to the Convention.
- The EU Ship Recycling Regulation (EU SRR, Regulation 1257/2013) — applies to EU-flagged vessels of 500 GT and above, and to non-EU-flagged vessels of that size calling at EU ports.
The gross-tonnage threshold is what matters, not waterline length — a beamy 45 m yacht can sit above 500 GT while a slender 55 m sits below it. Whether a vessel is private or commercial can also affect how the obligation is applied. Because the combinations are genuinely confusing, we built a short checker that walks through flag, tonnage, build year, and EU port calls: the IHM applicability & deadline checker. It is a starting point — your flag State administration or class society confirms the exact obligation for your vessel.
Related: IHM on older superyachts: when the builder's records don't exist — the in-scope question for legacy vessels.
The three parts of an IHM
An IHM has three parts, each with distinct obligations:
Part I — Hazardous materials in structure and equipment
The core of the inventory: a material-by-material record of hazardous substances built into the vessel. Part I is verified against physical survey and visual inspection, and it is the part that moves over a vessel's life — every time a controlled material is added, removed, or changed.
Part II — Operationally generated waste
Hazardous waste streams generated while the vessel operates. Entries are cross-referenced to the relevant MARPOL Annex and supported by disposal documentation.
Part III — Operationally generated stores
Hazardous materials held on board for maintenance and operation. Each entry is supported by a current Safety Data Sheet (SDS); when a product is superseded or reformulated, the SDS is updated.
Some yachts track only Part I in practice and confirm their Part II/III obligations with their flag or class. The structure above is what a complete inventory looks like. Each part explained in detail for yachts →
HKC and EU SRR — twin documents
Many yachts are in scope of both regimes. The good news is that they cover substantively the same inventory: a single, well-maintained Part I can support both the HKC certificate and the EU SRR statement. The EU SRR has applied to EU-flagged vessels of 500 GT and above since 31 December 2020 — it predates the global HKC — so EU-flagged yachts have lived with these obligations for several years already.
The distinction matters most when you are working out which certificate your vessel carries and who issues it. We cover the difference in detail here: the Hong Kong Convention is in force — what it means for your vessel.
The certificate and the survey cycle
For an operational yacht, the document a Port State Control officer asks for is the certificate confirming the inventory — under the HKC, the International Certificate on the Inventory of Hazardous Materials (ICIHM), issued by your flag State administration or an authorised Recognised Organisation. The survey cycle runs:
- Initial survey — before the certificate is first issued, confirming the inventory is complete, accurate, and documented.
- Renewal survey — at intervals not exceeding five years; the certificate is re-issued.
A practical transition date to know: existing ships have until their first renewal survey on or after 26 June 2025, and in any case by 26 June 2030, to hold the HKC certificate (what the 2030 deadline means for owners). The two dates most likely to cause problems at an inspection are certificate expiry and any open change record from the last refit. Write them down. Preparing for the renewal is its own task — here is a preparation checklist.
Why Part I is a living document
This is the single most misunderstood point about the IHM, and the one that separates a vessel that sails through inspection from one that does not. Part I is not a one-time survey done at delivery and filed away. It must be updated every time a controlled material is added, removed, or changed.
A refrigerant recharge can touch it. A refit that strips and replaces insulation certainly does. A replacement component that contains no controlled material needs no entry. The obligation is continuous, and the renewal survey verifies that the updates were actually made. Two areas generate most of the work:
- Refits and material changes. When materials change, you need the documentation chain — Material Declarations (MD) and Supplier's Declarations of Conformity (SDoC) — from the contractors who did the work. Our refit briefing for DPs and Chief Engineers walks through it, and the refrigerants / ODS article covers the most common recurring change.
- Stores and SDS currency. Part III lives or dies on whether your Safety Data Sheets match what is actually in the lockers.
This is precisely where keeping records in a structured workspace beats a consultant's one-off PDF: the document only stays valid if someone keeps it moving with the vessel — which is why the role works best when it's owned by a named IHM Designated Person. More on building the documentation chain →
Older yachts and missing builder records
The Convention applies regardless of build year, which raises an obvious problem for older yachts: the original builder's documentation may be incomplete or gone. There is a recognised pathway. Where build records are missing, the initial inventory is established through document review combined with a visual and sampling check by a competent person — not by guessing, and not by assuming the worst. We cover how the initial survey works for legacy vessels here.
Survey and Port State Control readiness
At an inspection in a Convention port, an officer may ask to see the certificate and its validity dates, the inventory itself (particularly that Part I is populated rather than blank), the change records since the last survey, the MD/SDoC documentation behind any material change, and current Part III SDS for stores on board.
The findings that come up most often are an expired certificate, a known refit with no corresponding change entry, missing contractor documentation, and out-of-date safety data sheets. None of these require a fresh survey to avoid — they require documentation discipline: knowing the records exist, where they are, and that they cover what will be asked about. A full walk-through of what surveyors look for is in the renewal-survey preparation checklist.
How software helps
An IHM is fundamentally a records problem that stays alive for the life of the vessel. The work is not hard; it is relentless — small, frequent, easy to defer, and unforgiving at survey time (our free printable superyacht IHM checklist covers the recurring upkeep). That is the gap purpose-built software fills:
- Part I / II / III records kept in one place, with a clear change history.
- Certificate expiry and survey intervals tracked, so renewal dates do not surprise you.
- MD and SDoC documentation stored against the change it supports, not scattered across email.
- A survey pack assembled in one click from records you have kept current — organised the way surveyors expect to read it.
Most IHM tools are built for commercial fleets — bulk carriers and tankers. MANTIS is built for the superyacht reality: small crews, owner-driven procurement, and a class-agnostic vessel that might be flagged anywhere. See how MANTIS compares to the alternatives →
Frequently asked questions
Does my superyacht need an IHM?
Under the Hong Kong Convention, ships of 500 GT and above on international voyages are in scope, regardless of flag or build year. The EU Ship Recycling Regulation applies to EU-flagged vessels of 500 GT and above and to non-EU-flagged vessels of that size calling at EU ports. Confirm your vessel's exact obligations with your flag State administration or class society.
What is the difference between the HKC ICIHM and the EU SRR Statement of Compliance?
They are twin documents covering substantively the same Inventory of Hazardous Materials. The HKC route produces an International Certificate on the Inventory of Hazardous Materials (ICIHM); the EU SRR route produces an Inventory Certificate / Statement of Compliance. A vessel maintaining a single Part I inventory can support both. Your class society can advise which certification pathway applies to your flag.
Is an IHM a one-time survey?
No. Part I is a living document. It must be updated whenever a material listed in the Convention's controlled-substance annex is added, removed, or changed — for example during a refit or an equipment replacement. The renewal survey, at intervals not exceeding five years, verifies that Part I has been kept current.
My yacht is older and the builder's records are missing — can we still build an IHM?
Yes. Where original build documentation is incomplete, the initial inventory is built through document review combined with a visual and sampling check carried out by a competent person. This is a recognised pathway under the IHM Guidelines for existing ships.
Does MANTIS certify my IHM?
No. MANTIS is a workspace for keeping your IHM records, certificates, and supporting documentation current and organised. Certification is issued by your flag State administration or an authorised Recognised Organisation (typically your class society) after their survey. MANTIS helps you have the records ready for that review.
MANTIS is IHM compliance management software for superyachts. It manages Part I/II/III records, tracks certificate expiry and survey intervals, stores MD/SDoC documentation, and generates survey-pack PDFs for class society review. Start free beta →