Whether you are a large ship owner or a small one, the term Inventory of Hazardous Materials (IHM) will be frequently used. And oftentimes too, they keep running into questions about what an IHM really involves. “Does my vessel need one at all?” That uncertainty carries heavier costs. The Hong Kong Convention, which entered in June 2025, requires certain ships to carry and maintain the IHM for their specific ship. This guide will explain IHM compliance simply: the meaning, who it’s for, how to obtain the certificate, and common mistakes.
What is an Inventory of Hazardous Materials (IHM)?
An Inventory of Hazardous Materials is a document that lists the type, amount and location of dangerous substances on the ship. For example, Asbestos sits in old insulation, PCBs run through wiring, heavy metals hide in paint. The IHM notes all these factors.
The International Maritime Organization’s (IMO) Hong Kong Convention supplies the rules. According to it, the inventory consists of three sections. Part I covers the hazardous materials in the ship’s structure and equipment. This is the part that every trading vessel must keep up to date. Part II deals with the hazardous waste from operations. And finally Part III handles hazardous materials in stores. Fortunately, parts II and III are only for vessels heading for scrapping.
As of now most owners focus on Part I. It has to stay accurate. Repairs or refits that change materials on board must cause an update in the inventory.
What is an IHM Certificate? What Does it Cover?
Unlike its name suggests, the IHM Certificate isn’t just one standard document for every ship. It takes different forms based on the flag state and the stage of life the vessel is in.
- Statement of Compliance (SoC): This is issued to ships under flags that have not been officially approved by the Hong Kong Convention, and it meets Part I’s requirements
- International Certificate on Inventory of Hazardous Materials (ICIHM): This applies to ships of states that have been approved by the convention.
- International Ready for Recycling Certificate (IRRC): This appears only when a ship heads for recycling after the final survey confirms all three parts of the IHM
Survey work for the ships are usually carried out by the Classification societies for the flag states (DNV, ABS, ClassNK) and issue the certificate once the appropriate conditions are met.
Which Vessels Need an IHM?
Simple answer? Most ships over 500 gross tonnage need one. This covers:
- Existing ships already in service
- New ship builds, which need Part I completed during constructed
- Ships calling at an EU port, regardless of flag. This is due to the EU Ship Recycling Regulation
- Ships flagged to a country that has approved the Hong Kong Convention
The EU regulation has applied since 2020. Since the Hong Kong Convention took effect, ships in international trade cannot avoid IHM simply by choosing an unendorsed flag. Checking the requirement against flag and trading routes comes first before certification begins.
Why is IHM Compliance Important?
An IHM compliance may be a regulatory requirement, but it also has a practical benefit throughout the ship’s lifecycle. If a ship maintains good IHM, technical managers can better understand the hazardous materials present onboard before any repairs, conversions and recycling happen. This reduces uncertainty, supports safer working conditions, and helps avoid unnecessary delays during surveys or inspections.
The IHM Compliance Process
Although every vessel differs in some way, the process generally stays the same throughout.
- Check if your ship needs an IHM: by checking tonnage, flags and trading routes
- Hire a credited IHM surveyor: They will help review the ships documents and identify the materials that need testing (if any)
- Test Suspected hazardous materials: Paint, Insulations, Gasket. All should be done through an accredited laboratory.
- Prepare Part I of the IHM: List the type, location and quantity of the hazardous materials found onboard.
- Submit the inventory for verification: The classification society attached to your flag will review it and carry out the survey.
- Receive your SoC or ICIHM
- Keep the IHM up top date: Remember to record down any repairs, replacements and new oncoming equipment that might introduce hazardous materials.
IHM Challenges Ship Owners Face
Many owners believe preparing an IHM is simpler than it is.
One of the biggest challenges is to get a complete picture for older vessels where the original construction records or supplier documentation might no longer be available. Another common misconception is that inventory preparation should be done only shortly before a vessel is recycled. In fact, a proper IHM throughout the vessel’s operational life greatly simplifies future inspections and compliance activities.
Another area sometimes overlooked is keeping up with inventory after repairs and equipment replacements. Even relatively small changes may require updates to keep the inventory accurate.
How Synergy MariServ Supports Ship Owners with IHM Compliance
Going from “we might need one of these” to a valid, maintained IHM requires coordination between your technical team, an accredited surveyor and your classification society. Synergy MariServ works with ship owners through every step of that process.
Our IHM Maintenance Solution includes gap assessments on existing fleets, document preparation, liaison with surveyors and ongoing updates to keep your inventory up to date as the ship operates. That means fewer surprises at survey time and a smoother path if the vessel is ever headed for recycling. Whether you need help developing your first IHM checklist, or renewing an existing IHM certificate, our team manages the coordination, so your fleet is always ready for survey.
Final Takeaway
IHM Compliance isn’t difficult once you understand the basics. Make sure your ship is in scope, keep part I regularly updated and don’t keep part II and left till the very last minute. Once you start treating this process as ongoing maintenance rather than one and done certificate, you’ll start avoiding delays at survey and the recycling yard.
FAQs
Q: What is IHM?
A: IHM stands for Inventory of Hazardous Materials. It is a document that lists the hazardous materials on a ship along with their type, quantity, and location on board. It’s used to keep the crew safe during the vessel’s working life and to guide safe, environmentally sound recycling once the ship is scrapped.
Q: What is IHM Compliance
A: IHM compliance means a ship carries an Inventory of Hazardous Materials that identifies what’s on board and meets the requirements of the Hong Kong Convention and the EU Ship Recycling Regulation.
Q: Which ships need an IHM
A: Most ships of 500 gross tonnage (GT) or more on international voyages need an IHM, though the exact requirements can shift depending on flag and trading area.
Q: How long does it take to complete an IHM
A: Timing depends on the size and complexity of the vessel. Expect document review, an onboard inspection, lab testing of samples, and then verification by the classification society once the inventory is prepared.
Q: What happens in my ship doesn’t have an IHM
A: Without a compliant IHM, a ship can run into port state control issues, delays, detention, or trouble getting the certification it needs for international trade.
Q: How often should an IHM be updated
A: Part I of the IHM needs updating whenever repairs, modifications, or new equipment add or remove hazardous materials on the vessel.
Q: Who can prepare an IHM?
A: Make sure only qualified professionals prepare an IHM, working with authorized surveyors and laboratories.
