Enclosed space entry is the most heavily regulated routine activity in the marine sector, and it keeps killing people at roughly the same rate it did fifteen years ago.
The scale is documented. Around 350 seafarers and shore workers are estimated to have died from asphyxiation in enclosed spaces aboard ships since 1996, and 70 of those deaths occurred in 43 separate accidents since 2022 alone. Counting all causes of death in these spaces, including falls, crush injuries and drowning, the total passes a thousand, splitting roughly seventy to thirty between crew and shore personnel, and averaging around forty deaths a year.
What makes that figure difficult to explain away is the regulatory history sitting alongside it. This is not a hazard anybody has ignored.
The Regulation Is Not the Missing Piece
Successive instruments have addressed this hazard directly, each one tightening what is required of operators and crews.
| Instrument | In force | What it required |
|---|---|---|
| Resolution A.1050(27) | 2011 | Revised recommendations for entering enclosed spaces aboard ships |
| SOLAS Reg. III/19.3.6 | 1 January 2015 | Enclosed space entry and rescue drills every two months, for all crew with entry or rescue duties |
| SOLAS Reg. XI-1/7 | 1 July 2016 | Portable atmosphere testing instruments for oxygen, flammable gases, hydrogen sulphide and carbon monoxide |
| Resolution MSC.581(110) | Adopted June 2025 | Replaces A.1050(27). The most substantial revision in more than a decade |
Between the 2011 recommendations and early 2025, the number of enclosed space accidents and fatalities did not fall. Accident investigations over the same period kept identifying the same causes. A decade of mandatory drills, carried out every two months on every vessel covered by the convention, has not changed the outcome, and any serious discussion of training in this sector has to start from that fact rather than from the assumption that more of the same will work.
What the 2025 Revision Changes
Resolution MSC.581(110) was adopted in June 2025 and endorsed by the IMO Assembly the following December. It is worth reading closely, because several provisions are effectively admissions about how people actually die in these spaces.
Single-person entry is now explicitly prohibited for the first time. Vessels must hold a ship-specific enclosed space emergency response plan, reviewed and updated after each drill, and maintain a register of every enclosed space aboard with its hazards assessed. Atmosphere testing must now include carbon dioxide capability, and the revision introduces the concepts of connected and adjacent spaces, which must be tested before entry because a space can be made lethal by what sits next to it.
Two further provisions matter for anyone running a shipyard or terminal. Before any contractor, stevedore or shore worker enters an enclosed space, a joint ship and shore risk assessment is required, a schematic plan showing which spaces are safe and unsafe must be posted at the gangway, and shore personnel must be briefed on hazards specific to that vessel. That is a direct response to the roughly thirty per cent of deaths that are shore workers rather than crew.
The provision that says most about the underlying problem concerns time. Operators are now required to allocate adequate time for enclosed space operations, on the explicit basis that time pressure has been a recurring causal factor in past casualties. Regulations rarely legislate against schedule pressure unless the pattern is unmistakable.
The recurring sequence is not one error. A crew member enters and collapses. A colleague sees it, goes in to help without equipment, and collapses as well. A third follows. The fatality count in a single incident is frequently two or three, and the second and third deaths are the rescue attempt.
This is also not a problem confined to junior or inexperienced personnel. Masters and Chief Officers are well represented among the dead. Whatever is failing, it is not knowledge of the rule.
What a Two-Monthly Drill Cannot Rehearse
If the rule is understood, the drills are happening and the deaths continue, the useful question is what the drill actually practises. Three things it cannot reach account for most of the gap.
It cannot create the hazard
The thing that kills in these spaces is invisible. Oxygen at 20.9 per cent is normal air. Below about 16 per cent judgement is already impaired. Below six per cent, death follows within minutes. There is no smell, no colour, no sound and no sensation to mark the difference, which is precisely why people walk into these spaces confidently.
A drill cannot reproduce that, because reproducing it would mean creating an atmosphere capable of killing the participants. So the drill rehearses the procedure in a safe space, and the one lesson that matters most, that a lethal atmosphere is indistinguishable from a safe one without a meter, is the lesson the drill can only describe.
It cannot rehearse the impulse
The behaviour that produces the second and third fatality is not a procedural error. It is a reflex to help a colleague who has just collapsed in front of you, and it operates faster than recall of a rule.
Practising the correct response requires being placed in that moment: someone you work with is motionless below you, going in is wrong, and raising the alarm and waiting for equipment feels unbearably passive. A scheduled drill with a volunteer lying down in a ventilated compartment does not produce that, and it is the only moment in the whole sequence where training changes an outcome.
It cannot let anyone fail
A drill is observed, scheduled and passed. Nobody skips the gas test in a drill, because everyone knows they are being watched and the meter is in someone's hand for that reason. Real incidents follow shortcuts taken under schedule pressure, and a training format in which the shortcut is never available and the consequence never arrives cannot inoculate anyone against taking it. Regulators noticing unsatisfactory drill execution during recent port state inspection campaigns suggests the gap between the drill on paper and the drill in practice is itself well established.
A compliant drill and a rehearsed response are not the same thing. Talk to RoT STUDIO about simulating enclosed space entry for your vessels or yard and see what a drill cycle cannot cover.
Three Marine Environments, One Hazard
The same physics applies across the sector, but the operational constraints differ enough that training has to be built differently for each.
Vessels in service
Cargo holds, ballast tanks, chain lockers, cofferdams, void spaces and pump rooms. The specific risk is that the atmosphere depends on what the ship is carrying, and several common cargoes consume oxygen or generate toxic gas without any external sign. Coal, timber and wood products including chips and pellets, seed cake, scrap metal, ferrous materials and metal sulphide concentrates have all produced fatalities this way. A space that was safe on the last voyage can be lethal on this one.
Shipyards, repair and machinery spaces
A yard adds hazards a vessel at sea does not carry. Hot work inside or adjacent to tanks introduces ignition and consumes oxygen. Coating and paint operations release solvent vapour into confined volumes. Purging and inerting change an atmosphere without anybody entering. Machinery spaces combine confinement with stored energy, so isolation and lockout have to hold while someone is inside a structure they cannot quickly leave.
Workforce composition compounds this. Yards run large subcontractor populations with high turnover, often multilingual, frequently working their first shift on a hull they have never seen. The new requirement for joint ship and shore risk assessment and gangway posting of safe and unsafe spaces exists because this interface is where a substantial share of deaths occurs.
Naval and defence
Warship compartmentalisation produces more enclosed spaces in a smaller volume than any commercial equivalent, with tighter accesses and denser routing. Damage control doctrine also cuts against enclosed space caution in a specific way: naval crews are trained to move toward casualties and compartment emergencies at speed, which is correct for firefighting and flooding and precisely wrong for an oxygen-deficient compartment.
Access is the other constraint. A vessel alongside for maintenance, or in a secure facility, is not readily available for repeated training, and external trainers cannot always be brought aboard. A United States naval shipyard has publicly documented building a virtual replica of a warship from around one hundred laser scans specifically to run workforce training without occupying the hull, noting that physical mockups can take hours or days to reset between runs. The constraint driving that decision is common across defence yards.
The two-monthly entry and rescue drill required under SOLAS is a physical exercise with real equipment, and nothing here replaces it. Crews must handle the actual meter they will use, the actual breathing apparatus and the actual recovery equipment, and calibration and maintenance competence cannot be learned in a headset.
Simulation covers what the physical drill cannot: the invisible atmosphere, the decision under pressure, the rescue impulse, and repeated exposure between drill dates. Any vendor presenting it as a substitute for the statutory drill is misrepresenting both the regulation and the technology.
What Simulation Adds Between Drill Dates
Positioned as a supplement, immersive simulation reaches the specific failures the drill cycle leaves open.
It can make the invisible visible on demand. A trainee can enter a space that reads as normal, watch a meter fall, and experience the consequence of having skipped the test, which is an experience no safe drill can deliver. It can run the rescue moment repeatedly, putting the same person in front of a collapsed colleague until raising the alarm rather than descending becomes the practised response rather than the remembered rule.
It also handles the parts of the new resolution that are cognitive rather than physical. Connected and adjacent spaces are a spatial reasoning problem, since the question is which neighbouring volume could contaminate this one, and a three-dimensional model of an actual vessel answers that far better than a diagram. The same applies to an enclosed space register, which becomes considerably more useful when crews have walked the spaces it lists.
The practical arguments follow from access. A yard inducting subcontractors weekly cannot run a statutory drill for each intake, and a vessel-specific environment can be delivered to a training room ashore before anyone boards. The approach mirrors what RoT STUDIO builds for occupational health and safety training in virtual reality in other high-hazard sectors, where the constraint is identical: the scenario that most needs rehearsing is the one that cannot safely be staged.
Frequently Asked Questions
These come up whenever a shipping operator, yard or naval training authority starts scoping simulation for this subject.
Does VR training satisfy the SOLAS drill requirement?
No. The regulation requires physical entry and rescue drills every two months for crew with those duties, and that obligation stands regardless of what else an operator provides. Simulation sits alongside it, covering hazard recognition, decision making and the rescue response between drill dates, and it should be documented as supplementary training rather than recorded against the statutory requirement.
Why have mandatory drills not reduced the fatality rate?
The most credible explanation is that drills rehearse procedure while incidents are caused by judgement under pressure. Investigations repeatedly find the same contributing factors, including time pressure, skipped atmosphere testing and unplanned rescue attempts. None of those is addressed by correctly performing a scheduled exercise in a space known to be safe.
What does MSC.581(110) require that the previous guidance did not?
The main additions are a prohibition on single-person entry, ship-specific emergency response plans reviewed after each drill, an enclosed space register with assessed hazards, carbon dioxide testing capability, testing of connected and adjacent spaces, joint ship and shore risk assessment before shore personnel enter, and an explicit obligation to allow adequate time for these operations.
Does this apply to shipyard workers and contractors, not just crew?
It does, and the revision strengthens exactly that interface. Shore personnel account for a substantial share of deaths in these spaces, and the new requirements for joint risk assessment, gangway posting of safe and unsafe spaces, and vessel-specific briefing for shore workers exist because of it. For yards running large subcontractor populations, induction quality is a direct safety control.
Can simulation be built for a specific vessel or class?
Yes, and for this subject it is usually worth it. Generic tank environments teach the principle, while a specific vessel teaches the actual access, the actual routing and the actual adjacent spaces. Where drawings or scan data exist the environment can be built from them, which is how naval and repair yards have generally approached it.
What should an operator measure?
Behaviour rather than completion. Whether the trainee tested before entry, whether they tested connected and adjacent spaces, how long entry preparation took under time pressure, and critically whether they descended toward a collapsed colleague or raised the alarm. That last figure is the one worth tracking across a fleet or a workforce, because it corresponds directly to how multiple-fatality incidents develop.
A Training Problem, Not an Awareness Problem
Everyone in this sector knows enclosed spaces are dangerous. Posters say so, inductions say so, and the rule has said so for over a decade. The people dying include Masters and Chief Officers who could recite the procedure accurately. Awareness is not the constraint.
What is missing is rehearsed behaviour under the conditions where the decision is actually made, with a schedule pressing, an atmosphere that gives no warning, and a colleague on the deck below. The 2025 revision moves the regulatory floor upward, and it will produce new plans, new registers and new checklists. Whether it moves the fatality figure depends on whether the training behind those documents reaches the moment the documents cannot describe.
How RoT STUDIO Approaches This
RoT STUDIO builds HSE simulation around the scenarios that cannot safely be staged, which is the category enclosed space entry sits in. Scenarios are constructed so that atmosphere behaves as it does in reality, invisibly and without warning, so that the consequence of skipping a step arrives inside the scenario rather than being described afterwards, and so that the rescue decision is faced repeatedly rather than discussed.
For marine work the environment normally has to be the client's own. Tank geometry, access arrangements, machinery layout and adjacent spaces are what make a space dangerous in a particular way, which places this work with Customized VR/XR Services rather than a catalogue module. Where a yard or operator wants to author and revise its own scenarios as vessels and procedures change, the RoT STUDIO License supports that without software development resources.
Performance data is recorded per trainee across attempts, which matters here because the behaviour worth evidencing is specific and countable. The wider health and safety training programme applies the same method across other high-hazard environments, and industrial VR training covers the machinery and isolation side that yard work brings with it.
RoT STUDIO will map your vessels, tanks and yard spaces against the 2025 requirements and show what a rehearsable version looks like for crews and contractors. Arrange a conversation with the RoT STUDIO team to scope it.
References
- IMO Resolution MSC.581(110), Revised Recommendations for Entering Enclosed Spaces Aboard Ships, adopted June 2025, superseding Resolution A.1050(27)
- SOLAS Regulation III/19.3.6, enclosed space entry and rescue drills, in force 1 January 2015
- SOLAS Regulation XI-1/7, portable atmosphere testing instruments, in force 1 July 2016
- Industry association safety statistics on enclosed space fatalities aboard ships, including crew and shore personnel breakdowns
- Marine insurer and classification society guidance on enclosed space entry, rescue procedures and oxygen-depleting cargoes
- Port state control campaign findings on enclosed space drill execution
- Published naval shipyard programmes using laser-scanned vessel replicas for workforce training
