Enclosed space safety isn’t a paperwork problem. It’s a leadership problem. MSC.581(110) finally treats it that way. Most enclosed space deaths don’t happen to the person who entered first. They happen to the person who rushed in to save them. One victim becomes two. Then three. Not because the crew didn’t care, but because nobody stopped to test the atmosphere before the rescue attempt.
And here’s what makes this pattern even harder to accept: in almost every one of these incidents, the permit was signed. The drill was logged. The SMS procedure existed on paper. The paperwork was perfect. The outcome was fatal.
This is the gap that IMO Resolution MSC.581(110) was written to close.
What changed and why it matters now
In December 2025, the IMO’s 34th Assembly formally endorsed MSC.581(110), revoking the older Resolution A.1050(27) that had been in place for years. The revision was developed through the Sub- Committee on Carriage of Cargoes and Containers (CCC 10) and adopted by MSC 110 in June 2025, specifically because enclosed space fatalities were not declining despite existing guidance.
The IMO acknowledged something the industry already knew on the ground: many enclosed space accidents stem not from a lack of procedures, but from a failure to systematically identify hazards, assess risks, and implement entry protocols that actually match what happens on board.
MSC.581(110) is not a minor update. It is a structural shift in how enclosed space safety is expected to be managed from a documentation exercise to an operational competency requirement.
The key changes ship operators (marine surveyors and other affected parties) need to know
Here’s a breakdown of the most significant changes in the revised recommendations, and why each one matters operationally.
1. CO2 monitoring is now explicitly required
Under the previous resolution, CO₂ was not formally specified as a mandatory measurement before entry. MSC.581(110) changes that. Carbon dioxide must now be measured before and during enclosed space entry – in addition to O₂, CO, and any other gases identified in the risk assessment.
The science behind this is well- established: CO₂ can accumulate in spaces carrying or adjacent to organic cargoes, and its relationship with oxygen depletion is not always straightforward. The revised recommendations make CO₂ testing a non-negotiable part of the atmospheric assessment, with a threshold of less than 0.5% (5,000 ppm) before entry is permitted.
2. The enclosed space register must be ship-specific
Previously, many companies used generic fleet-wide templates for their enclosed space registers. MSC.581(110) removes the prescriptive example that was in A.1050(27) and instead requires each company to develop its own ship- specific register.
This register must list every enclosed space on board, identify connected and adjacent spaces, document specific hazards for each space, and include risk mitigations – such as the time needed to achieve required air changes, gas testing methods, and Lock-Out/Tag-Out procedures. The register and its associated risk assessments must be maintained both on board and ashore and must be updated whenever conditions change (for example, after loading certain cargoes, or if a ballast tank is temporarily used for treated sewage or grey water).
3. Entry procedures are tighter
The revised recommendations strengthen several procedural requirements that were previously implied or left to company discretion. Single-person entry is now explicitly prohibited. EEBDs (Emergency Escape Breathing Devices) are clarified as being for escape only – they cannot be used as a basis for entering an enclosed space.
The competent person carrying out the pre-entry risk assessment must have both adequate theoretical knowledge and practical experience. This is not a box-ticking exercise – the resolution expects that these individuals can make informed judgements about the spaces they are assessing.
4. Emergency response plans must be drill-tested and reviewed
MSC.581(110) requires that the enclosed space emergency response plan be directly linked to the Enclosed Space Register and its risk assessments. More importantly, the resolution recommends that the emergency response plan be reviewed after every drill to assess its effectiveness and make improvements where needed.
This is a meaningful shift. It moves emergency preparedness from a static document into a living process – one that evolves as the ship, its cargo, and its crew change.
5. Shore-side responsibilities are expanded
The revised recommendations place greater emphasis on the role of shore personnel -including the shipping company’s ISM responsibilities in ensuring enclosed space safety. The company must be actively involved in the development of the Enclosed Space Register, the risk assessment process, and the overall safety management framework for enclosed space entry.
Why SIRE 2.0 and RightShip make this urgent
Here’s what many operators haven’t fully grasped yet: the inspection landscape has shifted in a way that makes paper compliance insufficient.
SIRE 2.0 which is now the sole inspection framework for tanker operations under OCIMF no longer operates as a documentation review. Inspectors assess crew competency through direct observation and interview. They evaluate whether crew members understand the rationale behind safety-critical tasks, not just whether they can locate the procedure in the SMS manual.
For enclosed space entry specifically, SIRE 2.0 inspectors review entry procedures and interview crew members including ratings to assess their genuine familiarity with the protocols. Inspectors assign competency ratings ranging from “Not as expected” to “Exceeds expectation,” and any substandard rating must be supported by a Performance Influencing Factor (PIF) analysis.
RightShip’s RISQ framework follows a similar trajectory, using behavioural data alongside technical compliance to assess vessel safety.
The convergence of MSC.581(110) with SIRE 2.0 and RightShip means that having an updated SMS on paper is no longer sufficient. Your crew must be able to demonstrate under questioning, under observation, in real-time that they understand why CO₂ is tested, why the register is ship-specific, why EEBDs aren’t for entry, and what their exact role is in an emergency.
Where most fleets have gaps right now
Based on what I’ve seen across the industry, here are the areas where the majority of vessels are not yet aligned with MSC.581(110):
The Enclosed Space Register. Most vessels still have a generic fleet template. The resolution requires a ship-specific register with space-by- space hazard identification and risk mitigation. This is the single largest compliance gap I see across fleets right now.
CO₂ testing protocols. Many vessels test for O₂ and combustible gases, but do not routinely measure CO₂ before entry. MSC.581(110) makes this mandatory, and inspectors will ask about it.
Crew competency on the “why.” Crews can often describe what the procedure says. Fewer can explain why each step exists. SIRE 2.0 inspectors are trained to probe for this deeper understanding particularly with junior officers and ratings.
Emergency response plan linkage. The emergency plan often exists as a separate document that doesn’t reference the specific hazards identified in the Enclosed Space Register. MSC.581(110) expects these to be directly connected.
Post-drill review process. Many vessels conduct drills and log them. Fewer have a structured process for reviewing the drill outcome, identifying weaknesses, and updating the emergency response plan accordingly.
What you should do now
If your SMS and enclosed space procedures haven’t been updated since A.1050(27), this is the starting point.
First, conduct a gap analysis against MSC.581(110). Review each of the nine major areas from the Enclosed Space Register to emergency response planning and assess your current state against what the resolution now expects.
While the list of spaces is not limited to a set number, the following nine categories represent major areas most typically included in the register and on ships:
- Cargo Spaces: Includes cargo holds (loaded or empty), cargo tanks (oil or chemical), and interbarrier spaces.
- Ballast Tanks: Includes water ballast tanks, peak tanks (fore and aft), and double bottom tanks.
- Fuel and Luboil Tanks: Bunker tanks, fuel oil tanks, and lubricating oil tanks.
- Pump Rooms and Compressor Rooms: Cargo pump-rooms, fuel pump rooms, and compressor rooms.
- Cofferdams and Void Spaces: Empty spaces between bulkheads or decks designed to prevent leakage or contamination.
- Duct Keels and Pipe Tunnels: Tunnels and spaces used to run cables or pipes throughout the ship.
- Machinery Spaces: Boiler furnaces, engine crankcases, and engine scavenge air receivers.
- Lockers and Storage Rooms: Paint lockers, CO2 rooms (fire suppression), battery lockers, and hazardous material storage.
- Sewage and Water Tanks: Sewage tanks, grey water tanks, and potable water tanks.
Second, update your Enclosed Space Register to be ship-specific. This is not optional, and it cannot be a template exercise. Each space needs its own hazard profile, risk assessment, and mitigation plan.
Third, integrate CO₂ testing into your standard atmospheric assessment procedure. Ensure your gas detection equipment is calibrated for CO₂ and that crew understand the 0.5% threshold and why it matters.
Fourth, train the crew, especially junior officers and ratings, not just on what the procedure says, but on the reasoning behind each step. This is what SIRE 2.0 inspectors will assess.
Fifth, review your emergency response plan and link it directly to your Enclosed Space Register. Run a drill, review it critically, and update the plan based on what you learn.
And finally – A resource to help
To support operators working through this transition, Capt. Kalra has developed an MSC.581(110) Compliance Gap-Analysis Checklist that covers all nine inspection areas with HIGH, MEDIUM, and LOW priority ratings for SIRE 2.0, RightShip RISQ 3.2, and PSC readiness.
It’s a practical tool, not a theoretical overview. Designed for ship operators, HSQE managers, and maritime safety officers who
need to move from A.1050(27) to MSC.581(110) systematically.
You can download the checklist at https://bit.ly/enclosed-space-safety
For more information: https://synergeticshippingsolutions.com
This article was first shared on LinkedIn.
It has been lightly edited and is republished here with our thanks.
By Capt. Arjun Singh Kalra, Director at Synergetic Shipping Technologies Pvt Ltd