Inspections

Port state control and detentions

Published 20 August 2026 · updated 22 September 2026

A ship that is detained is a ship that cannot perform. She is not off hire in a tidy way, she is alongside, not sailing, with a laycan running down. Port state control is the only routine, public, worldwide record of how a hull is actually kept, which makes it the cheapest signal a broker has about tonnage they have never seen.

What port state control is

Responsibility for a ship’s condition sits with her flag state. Flag states differ enormously in how seriously they take that, and some of them have no inspectorate worth the name. Port state control is the backstop: the coastal state inspects foreign ships calling at its ports against the international conventions the ship is certified under, SOLAS, MARPOL, Load Lines, STCW, the Maritime Labour Convention, and checks that the certificates on the bridge describe the ship the inspector is standing on.

It is not a survey and it is not class. A PSC officer is looking for evidence that the safety management system is real: whether the fire dampers close, whether the lifeboat engine starts, whether the oil record book matches the equipment, whether the crew can find the muster list and read it. Most of what they find is small. A little of it stops the ship.

The regional MoUs

Port state control is organised into regional Memoranda of Understanding, each covering a group of coastal states that agree a common inspection regime and share results:

• Paris MoU, Europe and the North Atlantic.
• Tokyo MoU, Asia and the Pacific.
• Indian Ocean MoU, Mediterranean MoU, Black Sea MoU, Riyadh MoU for the Gulf states.
• Viña del Mar Agreement for Latin America, Abuja MoU for West and Central Africa, Caribbean MoU.

The United States sits outside all of them and runs its own programme through the Coast Guard. That matters when you compare numbers, and it is the first reason not to read the table below as a ranking.

The commercially important point is that the regions are not sealed. A detention in one region is visible in the others, it feeds the flag state’s and the class society’s published performance, and under the Paris MoU a pattern of detentions can end in refusal of access to the whole region. A bad inspection in Rotterdam does not stay in Rotterdam, and an owner who tells you otherwise is describing a world that stopped existing decades ago.

What an inspection produces

An inspection produces a report listing deficiencies. Each one carries a code for the defect, grouped by area: fire safety, life-saving appliances, structural condition, pollution prevention, certificates and documentation, ISM, working and living conditions. Each also carries an action code, from rectify at the next port, through rectify before departure, up to detainable.

Detention is the serious outcome and it means what it says: the ship does not sail until the deficiencies are put right and, usually, re-inspected. A detention can last a day or several weeks depending on whether the fix needs a part, a class attendance or a shipyard. Zero deficiencies is common and unremarkable. A handful of minor deficiencies is the normal condition of a working ship and says almost nothing on its own.

What the record actually looks like

Neptune Atlas holds a vendor-sourced inspection history of 364,256 inspections across 44,764 hulls, from 22 March 2017 to 21 August 2026. Across that whole set:

By authority, and how not to read it

These are the twelve authorities with the most inspections on file, with what each of them recorded.

This is not a league table of rigour. It is what each authority recorded and what reached this dataset, and at least three things move a row before strictness does. The first is traffic mix: a port that mostly sees young, well-run, first-class tonnage will detain less than one that sees forty-year-old coasters, whatever its inspectors are like. The second is targeting: an authority that inspects selectively, going after the hulls its risk model flags, will show a higher rate than one that inspects broadly, because the denominator is different. The third is reporting practice: what counts as a detention, what gets filed, and what is published all vary.

The narrowness of the spread is itself the finding. Every authority above sits between roughly two and four per cent, which is far too tight to be measuring twelve different inspection cultures. An earlier extract of the same dataset had the same authorities ranging from under one per cent to over six, and the vendor has since restated them. Neither version is a measurement of strictness. Both are a measurement of what a commercial data supplier could collect and normalise, and the fact that the answer moved this much between two pulls is the strongest possible argument for not reading a league table into it.

Use the table to understand the shape of the data you are holding. Do not use it to decide that a call in one country is riskier than a call in another.

Targeting: why some ships get inspected constantly

Nobody inspects every ship at every call. The major regimes score each hull into a risk profile and let that profile set how often and how hard she is looked at. The inputs are broadly consistent across MoUs:

• Age and type. Older tonnage and higher-risk types are targeted more.
• Flag. The flag state’s own detention performance, published as a list, feeds straight into the profile of every ship flying it.
• Recognised organisation. The class society’s performance does the same.
• Company. The performance of the ISM manager across their whole fleet, which is one of several reasons the technical manager is worth identifying.
• Her own history. Deficiencies and detentions over a rolling recent window.

The consequence is a feedback loop that works in both directions. A clean record lowers the profile, which means fewer inspections at longer intervals, which means fewer opportunities to find something. A detention raises it, and the ship is then looked at harder for years. So the record is partly a measurement of the ship and partly a measurement of the attention she has been under, and a hull with many inspections is not automatically a worse hull.

How to read a history

Pattern over incident. One detention is an event. A detention every couple of years, in different regions, under different inspectors, is a way of operating. Do not condemn a ship for a single bad day and do not excuse a run of them as bad luck.

Recency over volume. Ships change hands, change managers and change crews. A detention from eight years ago, under a manager who no longer holds the DOC, describes a company that is no longer running her. What happened since the last change of manager is the part that predicts anything.

Repetition of kind. The most useful signal is the same category coming back: fire safety at three consecutive calls, or ISM findings that keep recurring after they were supposedly closed out. One recurring deficiency category says the safety management system is not correcting itself, and that is a maintenance culture, not an accident.

Read the deficiencies, not only the detentions. Detention is rare enough that most hulls have none, and 4.51 deficiencies on an average inspection means the detail sits in the list rather than in the headline.

That last point is the one that quietly breaks most attempts at this. The IMO number is permanent and the name is not, so a PSC record is only trustworthy when it is keyed on the IMO. A ship with a poor record, a new name and a new flag looks brand new in any system that matched on the name, and looking brand new is often the entire purpose of the exercise.

References

• IMO, Port State Control. The regional Memoranda of Understanding and the United States programme. imo.org
• Paris MoU, Annual Report 2025. parismou.org
• Paris MoU, Performance Lists, the white, grey and black list. parismou.org
• Paris MoU, Current Banning. Ships refused access to the whole region. parismou.org
• Tokyo MoU, New Inspection Regime. The ship risk profile and how targeting is calculated. tokyo-mou.org
• Tokyo MoU, Annual Report on Port State Control in the Asia-Pacific Region 2024. tokyo-mou.org

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