Technical Circular No: 002/2026
1. The IMO vide Resolution MSC. 581 (110) adopted the Revised recommendations for entering enclosed spaces aboard ships superseding Resolution A.1050(27).
2. The objective of these recommendations is to encourage the adoption of safety procedures and the development of sound practices aimed at preventing casualties to, and enhancing the safety of, personnel entering or working in enclosed spaces where there may be an oxygen-deficient, oxygen-enriched, flammable and/or toxic atmosphere.
3. These recommendations may be applied to all types of ships and provide guidance to ship operators, seafarers and shore personnel to work on board ships.
4. An overview of the key highlights of the Resolution MSC. 581 (110) includes:
a. New Definitions and Hazards:
The resolution introduces critical new terminology to enhance hazard identification:
● Connected Space: A newly defined term, a connected space (e.g., separated by a manual door) must be treated as containing a hazardous atmosphere until testing proves otherwise.
● Adjacent Space: The definition is clarified, with the implication that almost every space other than the accommodation block may be considered an adjacent space.
● Trapped Hazardous Atmosphere: A new definition and requirement, addressing a hazardous atmosphere that may be contained in a connected space even after the source space is discharged.
b. Ship Owners/ Managers have been advised to incorporate the following into their SMS in accordance with MSC.581(110):
● Enclosed space entry procedures. MSC.581(110) mandates that the company must ensure that single person entry into an enclosed space is not permitted.
● Risk assessment processes
● Permit-to-work systems
● Emergency response plans and Enclosed Space Register
● Training, drills, and authorization
c. Every ship should have a ship specific Enclosed Space Register which lists all enclosed spaces on board the ship, along with their connected spaces and adjacent spaces, their hazards, associated risk mitigations if applicable, and how the atmosphere in these spaces may change depending upon the nature of cargo carried or the content of the space.
The register should be managed as part of the SMS and reviewed periodically.
d. Emergency Response and Training:
● A ship-specific enclosed space emergency response plan should be established and incorporated into the SMS.
● Rescue equipment should be readily available and maintained in usable condition.
● Regular training and drills for enclosed space entry and rescue should be conducted.
e. Testing The Atmosphere:
The gas detection equipment should be appropriate for the cargo that the ship has carried and is carrying considering information provided in the shipper's declaration, the Safety Data Sheets (SDS), the IMDG Code, the IMSBC Code, International Bulk Chemical Code (IBC Code) and the IGC Code.
On ships carrying solid bulk cargoes, dangerous atmospheres may develop within cargo spaces, connected and adjacent spaces. The hazards may include flammability, toxicity, oxygen depletion, carbon dioxide and/or carbon monoxide generation, or self-heating, as identified in the shipper's declaration and/or in the individual schedules in appendix 1 of the IMSBC Code.
Hazards associated with CO2 is explicitly included in the revised recommendation. CO2 is a potent asphyxiant and can cause rapid loss of consciousness and death. Its behavior in cargo spaces justifies CO2 monitoring before and during enclosed space entry, in addition to CO and other toxic gases.
The gas detection equipment, including devices for testing CO2, should be capable of operating correctly even in oxygen-depleted atmosphere.
f. Number of gas detection equipment:
● All ships should carry at least two sets of gas detection equipment as required by SOLAS regulation XI-1/7, taking into account the Guidelines to facilitate the selection of portable atmosphere testing instruments for enclosed spaces as required by SOLAS regulation XI-1/7 (MSC.1/Circ.1477).
● Ships carrying cargoes capable of generating hazardous vapor and requiring regular entry must carry two additional sets.
● Detectors must be supplied with sufficient spares and calibration means and may use flexible hoses or fixed sampling lines to test remote areas safely.
g. Gas detection capabilities of portable gas detectors:
Persons entering enclosed spaces should be provided with calibrated and tested personal gas detection instrument or instruments that monitor the levels of:
● Oxygen,
● Carbon dioxide,
● Flammable gases or vapours,
● Toxic gases (including carbon monoxide), and
● Any other gases identified in the risk assessment.
h. Entry into an enclosed space should be allowed only after the atmosphere is demonstrated as being safe. Safe limits for entry are:
● 20.9% oxygen by volume;
● The level of carbon dioxide has been checked and is less than 0.5% by volume (5,000 ppm);
Note: National requirements may differ when determining the safe atmosphere range for gases stated above.
● Less than 1% of lower flammable limit (LFL) on a suitably sensitive combustible gas indicator, where the assessment has determined that there is potential for flammable gases or vapours; and
● Less than 50% of the occupational exposure limit (OEL) of any toxic vapours and gases.
● If these conditions cannot be met, additional ventilation should be applied to the space and retesting should be conducted after a suitable interval. Entry should be allowed only after all the above conditions are met
i. Enclosed Space Entry Permit:
● Entry should be conducted under an Enclosed Space Entry Permit.
● The validity of the permit should not exceed 8 hours.
5. Ship Owners and Managers are to take note of the above and are advised as follows:
a. Bring the new requirements to the notice of Master and ship’s crew.
b. Instruct the Masters to conduct a training session for the ship’s crew with respect to the requirements as mentioned in MSC. 581 (110) and maintain record of the training.
c. Review their Safety Management System (SMS) and revise it to align with the new requirements as per MSC. 581 (110). Any flag-specific requirements, if applicable, are to be complied with.
d. Ensure that a ship specific Enclosed Space Register is prepared and made available onboard.
e. Ensure ship is in possession of appropriate gas detection equipment mentioned under para 4f & 4g. Gas detectors are calibrated and alarms are set. Further, ensure that span gas for calibration and regular bump testing of portable gas meters also includes the calibration/ testing for CO2 meter.
f. Ensure that regular training and drills for enclosed space entry and rescue are conducted as per the SMS and records maintained.
Enclosure:
This Technical Circular and the material contained in it is provided only for the purpose of supplying current information to the reader and not as an advice to be relied upon by any person. While we have taken utmost care to be as factual as possible, readers/ users are advised to verify the exact text and content of the Regulation from the original source/ issuing Authority.