**Entry into Effect: 3 December 2025**

On 27 June 2025, the IMO adopted Resolution MSC.581(110), introducing Revised Recommendations for Entering Enclosed Spaces Aboard Ships. These recommendations were subsequently endorsed by the IMO Assembly and entered into effect on 3 December 2025, replacing and revoking Resolution A.1050(27).

The revised recommendations respond to the continued loss of life during enclosed space entry and place stronger emphasis on hazard identification, risk assessment, atmospheric testing, operational discipline, and emergency preparedness.

The objective of the revised recommendations is to reduce fatalities and serious injuries associated with enclosed space entry by promoting structured safety procedures and consistent operational discipline. Enclosed spaces continue to present some of the most hazardous working environments on board ships, often involving oxygen-deficient or oxygen-enriched atmospheres, as well as the presence of flammable or toxic gases.

Experience from casualty investigations has repeatedly shown that accidents in enclosed spaces are frequently linked to inadequate hazard identification, insufficient risk assessment, and poorly controlled entry procedures. In many cases, the physical configuration of shipboard spaces further complicates safe entry due to challenges with ventilation effectiveness, lighting, access, and internal movement.

The revised recommendations also recognize that safe enclosed space entry is not solely a procedural issue. Organizational leadership, both on board and ashore, plays a critical role in ensuring effective implementation by fostering a safety culture that empowers personnel to challenge unsafe conditions and suspend entry where risks are not adequately controlled.

In addition to prevention, MSC.581(110) places strong emphasis on prepared and ship-specific emergency response arrangements, ensuring that enclosed space rescue is planned, deliberate, and executed using appropriate equipment and trained personnel, rather than improvised or reactive actions that have historically led to secondary casualties.

Application

The Revised Recommendations for Entering Enclosed Spaces Aboard Ships are applicable to all ship types and are intended to be used by:

• Shipowners and operators

• Masters and crew

• Shore personnel and contractors involved in shipboard operations

Although the Recommendations do not introduce a new SOLAS regulation, they reinforce existing obligations under SOLAS Chapter XI-1, Regulation 7, which requires ships to carry appropriate portable atmosphere testing instruments, and are intended to be reflected in company procedures and onboard operating practices.

Key Changes and Operational Expectations

• SAFETY MANAGEMENT FOR ENTRY INTO ENCLOSED SPACES

The revised Recommendations reinforce that entry into enclosed spaces must be governed by a structured safety management approach. Enclosed space entry is to be treated as a high-risk operation requiring proper planning, supervision, and control. Company procedures should clearly define responsibilities, authority, and decision-making processes for enclosed space entry.

Leadership at both shipboard and shore-based levels is recognized as critical to effective implementation. Personnel must be supported and empowered to delay or cancel entry if conditions are unsafe or cannot be adequately verified.

• IDENTIFICATION OF THE HAZARDS AND ASSESSMENT OF RISK

Before entry, hazards associated with the space must be systematically identified and risks assessed. This includes consideration of oxygen-deficient or oxygen-enriched atmospheres, flammable gases, toxic substances, and the potential for rapid atmospheric change.

Risk assessments should be space-specific and task-specific, taking into account the space’s configuration, history of use, ventilation characteristics, and any connected or adjacent spaces that may influence conditions. Generic assessments are not sufficient for enclosed space entry.

• AUTHORIZATION OF ENTRY

Entry into an enclosed space should only be permitted following formal authorization, typically through an entry permit system. Authorization should confirm that hazards have been identified, risk controls are in place, and conditions are verified as safe.

Authorization should be limited in time and scope to the specific task being performed. Spaces should be secured to prevent unauthorized access, and single-person entry is not permitted.

• GENERAL PRECAUTIONS

General precautions include ensuring that personnel are properly trained, familiarized, and authorized for their roles, and that appropriate personal protective equipment is provided and used. Clear communication arrangements must be established before entry.

Lighting, access, means of escape, and internal movement within the space should be considered during planning. Entry should only proceed when conditions allow safe working and effective supervision.

• TESTING THE ATMOSPHERE

Atmospheric testing must be carried out prior to entry using appropriate, calibrated portable atmosphere testing instruments. Testing should address oxygen content, flammable gases, and toxic substances relevant to the space, including carbon dioxide where applicable.

Testing should extend to connected spaces where hazardous atmospheres may migrate. Where conditions may change, testing should be repeated or continuously monitored throughout the entry.

• PRECAUTIONS DURING ENTRY

During entry, conditions within the space should be continuously assessed. Ventilation arrangements should be maintained as required, and communication between personnel inside and outside the space must remain effective at all times.

Entry should be immediately suspended if atmospheric conditions deteriorate, communication is lost, or any unsafe condition develops.

• ADDITIONAL PRECAUTIONS FOR ENTRY INTO A SPACE WHERE THE ATMOSPHERE IS KNOWN OR SUSPECTED TO BE UNSAFE

Where the atmosphere is known or suspected to be unsafe, entry should be avoided unless absolutely necessary. In such cases, enhanced controls are required, including the use of suitable breathing apparatus, additional supervision, and clearly defined emergency arrangements.

Emergency Escape Breathing Devices (EEBDs) are intended for escape only and must not be relied upon for entry or rescue. Any entry under such conditions must be carefully planned and authorized.

• HAZARDS RELATED TO SPECIFIC TYPES OF SHIPS OR CARGO

The Recommendations highlight that certain ship types and cargoes present specific enclosed space hazards, including those associated with bulk cargoes, tank atmospheres, refrigerated spaces, and CO₂-based systems.

Operators should ensure that risk assessments and procedures account for cargo-specific and ship-specific hazards and that personnel are aware of these risks before entry.

• ACTION TO BE TAKEN IN THE EVENT OF AN EMERGENCY

Emergency response to incidents in enclosed spaces must be planned, deliberate, and ship-specific. Rescue arrangements should be established in advance and supported by appropriate equipment and trained personnel.

Unplanned or improvised rescue attempts are to be avoided, as they have historically resulted in secondary casualties. Emergency drills should be conducted to verify readiness and effectiveness of response arrangements.

Implications to SMS Procedures

The revised Recommendations introduce operational expectations that align directly with established Safety Management System (SMS) processes and onboard practices. Effective management of enclosed space entry should be reflected through documented arrangements addressing:

• Hazard identification and risk assessment

• Entry authorization and permit-to-work controls

• Crew training, competency, and familiarization

• Maintenance, testing, and calibration of equipment

• Emergency preparedness, response planning, and drills

Companies should review existing enclosed space entry procedures to ensure they remain aligned with the revised IMO guidance and current industry best practice, and that responsibilities and controls are clearly defined and consistently applied both onboard and ashore.

How Marinetegrity Can Assist

Marinetegrity Maritime Consultants supports shipowners and operators in reviewing and aligning enclosed space entry arrangements with the revised IMO Recommendations under MSC.581(110). Our support can include:

• Review of enclosed space entry procedures and permits

• Alignment of SMS documentation with current IMO guidance and operational practice

• Risk assessment and procedure gap analysis

• Crew-focused guidance on enclosed space entry and emergency response expectations

• Support ahead of Flag State, Class, or Port State Control inspections

Our approach focuses on practical compliance, ensuring that procedures are not only compliant on paper but effectively implemented onboard.

References

• IMO Resolution MSC.581(110) – Revised Recommendations for Entering Enclosed Spaces Aboard Ships

• SOLAS Chapter XI-1, Regulation 7 – Atmosphere Testing Instrument for Enclosed Spaces

• MSC.1/Circ.1477 – Guidelines to facilitate the selection of portable atmosphere testing instruments for enclosed spaces as required by SOLAS regulation XI-1/7