The American Bureau of Shipping (ABS) has provided an overview of IMO Resolution MSC 581 (110) – Revised Recommendations for Entering Enclosed Spaces Aboard Ships.
These new recommendations supersede and revoke Resolution A.1050(27), replacing them with updated safety measures, definitions, and procedural requirements aimed at reducing fatalities during enclosed space entry.
The IMO recognizes that many enclosed space accidents stem from a failure to systematically identify hazards, assess risks, and implement appropriate entry procedures. Investigations further highlight that the complex structural arrangements of certain spaces can hinder ventilation, illumination, and safe movement.
Key points to consider
The hazards from lack of Oxygen (O2) and the build-up of gases such as carbon dioxide (CO2) and carbon monoxide (CO) are well known, but their relationships are not always fully understood. More recent studies show that, as well as oxygen levels, the levels of carbon dioxide and carbon monoxide should be checked before entry is made to any enclosed space or adjacent connected space. To emphasize this, CO2 is now 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 following points provide additional clarification on specific elements of the revised Recommendations and address common questions regarding atmospheric monitoring, cargo-related hazards and gas detection equipment.
- Risk Assessment. A risk assessment should be conducted by the competent person prior to opening an enclosed space. The competent person should be appropriately trained. The risk assessment should assess the likelihood of a dangerous atmosphere being present or subsequently developing within the space along with any other potential hazards in the space as identified in the vessel’s Enclosed Space Register, and the need to ventilate adjacent spaces.
- Cargo-related gas emission risks. There is no general published list of cargoes that may produce flammable, toxic, corrosive or asphyxiant gases (such as CO2). Instead, hazard information should be derived from: the shipper’s declaration; Safety Data Sheets (SDS); the IMDG Code; the IMSBC Code (including individual cargo schedules); the IBC Code; the IGC Code. The revised Recommendations highlight several cargoes that have caused fatalities due to fire, explosion or asphyxiation.
- Number of portable gas detectors. MSC.581(110) does not change existing SOLAS or IGC Code requirements regarding the quantity of portable gas detectors. However, Paragraph 7.3 reinforces that all ships must carry at least two sets of gas detection equipment as per SOLAS XI-1/7. Ships carrying cargoes capable of generating hazardous vapor and requiring regular entry must carry two additional sets. Moreover, detectors must be supplied with sufficient spares and calibration means and may use flexible hoses or fixed sampling lines to test remote areas safely.
- Gas detection capabilities of portable gas detectors. The requirements remain consistent with previous minimum requirements as detailed in MSC.1/Circ.1477. Paragraph 8.2 details that personal detectors should measure: oxygen (O2); any other gases identified in the risk assessment.
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