People talk about “the IHM” as if it were one document. It isn’t — it’s three parts, each covering a different category of hazardous material, each with its own upkeep rhythm. Understanding which is which is the difference between an inventory that survives a survey and one that has quiet gaps. Here is what each part actually covers on a superyacht.
The quick version
| Part | Covers | Lives | Upkeep trigger |
|---|---|---|---|
| Part I | Hazardous materials built into the structure & equipment | Always — the core, certified document | Any material change (refit, replacement) |
| Part II | Operationally generated waste | Indexed during operations | Waste generated / disposed |
| Part III | Hazardous materials in stores on board | Maintained as stores change | New / superseded products |
Part I is the one a surveyor scrutinises most and the one that must be kept genuinely current. Parts II and III matter, but they behave differently.
Part I — hazardous materials in structure and equipment
This is the heart of the IHM: a material-by-material record of the hazardous substances that are built into the vessel — in the hull and structure, in machinery and equipment, in coatings, insulation, cabling, and gaskets.
The controlled substances come from the Convention’s annex tables — broadly, Table A materials (prohibited/restricted: asbestos, PCBs, certain ozone-depleting substances, organotin anti-foulings) and Table B materials (controlled above threshold: lead, mercury, cadmium, hexavalent chromium, and others). Part I records what is present, where, and in what quantity.
The defining feature of Part I is that it is a living document. It changes whenever a controlled material is added, removed, or changed — which in practice means at every refit and many equipment replacements. Each change should be logged when it happens and supported by Material Declarations and SDoC from the contractor. The renewal survey verifies that Part I has actually been maintained.
If you only get one part right, get Part I right.
Part II — operationally generated waste
Part II covers the hazardous waste streams the vessel generates while operating — oily waste, sewage where relevant, hazardous garbage, and air-pollution residues. It is structured around the relevant MARPOL annexes rather than the IHM substance tables.
In day-to-day operation, Part II behaves more like an index than a live inventory: entries cross-reference the records you already keep (Oil Record Book, Garbage Record Book, ODS Record Book) and the disposal receipts from shore facilities. The key discipline is not duplicating records — it’s referencing the existing MARPOL entries and keeping the disposal receipts filed against them (retain those for at least three years; that’s a MARPOL obligation independent of the IHM).
Many superyachts confirm with their flag or class exactly how much Part II detail applies to their operation.
Part III — hazardous materials in stores
Part III covers hazardous materials held on board as stores — the products in the lockers, from cleaning chemicals to paints to certain spare parts. Each entry is supported by a current Safety Data Sheet (SDS).
Part III lives or dies on SDS currency. Products get reformulated; suppliers issue new SDS versions. The upkeep job is simple but relentless: when a product changes or a new one comes aboard, file the current SDS and mark the old one superseded. An SDS more than a few years old is usually out of date. Spare parts containing controlled substances (lead-acid batteries, certain gaskets, refrigeration components) belong here too — and when one is installed, that’s a Part I change as well.
How the three fit together
The parts aren’t independent silos — they interact. A spare part in Part III that gets installed becomes a Part I change. A refrigerant serviced under Part I generates an ODS release recorded under Part II. The value of keeping all three in one place is that these cross-references stay intact instead of scattering across separate files and record books.
That’s the whole case for managing the IHM as one connected workspace rather than three disconnected documents — which is what MANTIS is built to do.
For the complete picture — scope, certificates, the survey cycle, and how to keep it all current — see our complete guide to IHM for superyachts. If you’d like a one-page reference for your vessel, there’s a printable superyacht IHM checklist.
MANTIS is IHM compliance management software for superyachts. It manages Part I/II/III records in one place with a clear change history, tracks certificate expiry and survey intervals, and generates survey-pack PDFs for class society review. Start free beta →