Technical Notice on Resolution MSC.581 (110) “REVISED
RECOMMENDATIONS FOR ENTERING ENCLOSED SPACES ABOARD
SHIPS” issued by IMO
1. Background
The 110th session of the International Maritime Organization's Maritime Safety Committee
adopted amendments to the REVISED RECOMMENDATIONS FOR ENTERING
ENCLOSED SPACES ABOARD SHIPS (Resolution MSC.581(110)) (hereinafter referred
to as the New Resolution) and recommended that the Assembly revoked the previous
Recommendations (Resolution A.1050(27)). The 34th session of the Assembly, held on
December 1 and 2, 2025, agreed with the Committee's recommendation to revoke
Resolution A.1050(27). The new recommendations further refine the safety management
requirements for entering enclosed spaces, detailing key aspects such as hazard
identification, assessment of risk, precautions, and emergency response procedures,
thereby providing comprehensive guidance for accessing enclosed spaces.
2. Amendment of Resolution
Resolution MSC.581(110) amended the original resolution as follows:
2.1. Key Amendment of Definition
The New Resolution redefines enclosed spaces, subdivides spaces around enclose
space into connected spaces and adjacent spaces, and defined trapped hazardous
atmosphere and Enclosed Space Register.
2.1.1 Enclosed space means a space which may contain a hazardous atmosphere or lack
of oxygen and has any of the following characteristics:
2.1.1.1 limited openings for entry and exit;
2.1.1.2 Inadequate ventilation; or
2.1.1.3 Not designed for continuous human occupancy.
This includes but is not limited to spaces that are diverse in their characteristics such as
cargo holds, bilge spaces, ballast and other tanks, pump-rooms, chain lockers and engine
crankcases.
2.1.2 Connected space means a space is connected, by either permanent or temporary
means (such as a door, including manual watertight door) to a source space that may
contain a hazardous atmosphere. A connected space should be treated as containing a
hazardous atmosphere until testing proves otherwise. The nature of the connection may
lead to a “trapped hazardous atmosphere”.
2.1.3 Adjacent space means a space sharing a common boundary with a compartment
that may contain a hazardous atmosphere and such a space has no openings, temporary
or permanent, into that hazardous compartment and is designed to be a contiguous
barrier. Such a space may only contain a hazardous atmosphere in the event of failure of
that barrier. Precautions should relate to the possibility of such a failure.
2.1.4 Trapped Hazardous Atmosphere means a hazardous atmosphere that may be
trapped in a connected space in a manner that causes that space’s atmosphere to fill
and/or to empty at a different rate to the source space. Such a space, while recognized as
containing the same atmosphere, should be treated independently to the source space,
and should be assumed to contain a hazardous atmosphere until proved otherwise by
testing. For example, a trapped atmosphere may remain even after the cargo in the
source space is discharged.
2.1.5 Enclosed Space Register means a ship-specific 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, and which forms a part of the safety management for enclosed spaces.
2.2 Amendment of Safety Management for Entry into Enclose Space
New Resolution amended the requirement of Safety Management for Entry into Enclose
Space, such as Enclosed Space Register, relevant information relating to the hazards of
the cargo, personnel training and drills, company support, etc.
2.2.1 An Enclosed Space Register should be prepared or updated by the company, in
consultation with the ship. The Enclosed Space Register should be produced on a
ship-by-ship basis to identify enclosed spaces, the hazards of those spaces, assessment
of risks under the differing condition likely to arise in the space and risk mitigation
measures required to be put into place prior to entry, etc. The Enclosed Space Register
should contain:
.1 physical layout of the space and access and egress points, including of connected
spaces, if any;
.2 physical hazards in the space, e.g. vertical ladders, unguarded openings, poor
lighting, wet or slippery conditions, excessive heat;
.3 connection to adjacent spaces;
.4 specific hazards within the space, for example, the effect of ballast water treatment
method on the atmosphere within ballast tanks;
.5 if used, information related to additional technology, helping to determine enclosed
space condition;
.6 information related to fixed and portable ventilation systems including equipment
and where the equipment is stored;
.7 estimated time taken to achieve the air changes for safe entry, using forced or
natural ventilation;
.8 lighting and means for temporary lighting including intrinsically safe lighting where
appropriate;
.9 means for atmosphere testing;
.10 any pertinent information that would assist the risk assessment process;
.11 locking and "Safe to enter"/"Unsafe to enter" signage arrangements; and
.12 the equipment necessary to facilitate emergency rescue from the space.
2.2.2 The company should ensure that all relevant information, which relating to the
hazards of the cargo, is provided to the ship’s crew and distributed to those on board who
may be exposed to these hazards. The information should contain information submitted
by the shipper in accordance with the applicable requirements of SOLAS Regulation VI/2,
the International Maritime Solid Bulk Cargoes Code (IMSBC Code), the International
Maritime Dangerous Goods Code (IMDG Code), the IBC Code and the International Gas
Carrier Code (IGC Code), Safety Data Sheets (SDS), the shipper's declaration, etc.
2.2.3 The company should elaborate a procedural implementation scheme, which
provides for comprehensive training in the maintenance, calibration and use of
atmospheric testing equipment in such spaces. This training should be recorded, and
individual crew members who have been deemed competent in the maintenance,
calibration and use of atmospheric testing equipment should be listed. Additionally, the
training and competencies required for competent person, responsible person, and
attendant have been clearly defined.
2.2.4 The company should identify and provide the necessary equipment such as
ventilation devices, atmosphere testing equipment, breathing apparatus and personnel
recovery apparatus to facilitate safe entry and rescue from an enclosed space. All
necessary equipment should always be on board in operational condition. Crew members
should be trained in the use of equipment necessary to facilitate rescue from an enclosed
space and a record of this training should be maintained.
2.2.5 The company shall ensure that rescue drills for enclosed spaces are conducted on
board in accordance with SOLAS Regulation III/19.3.6, and shall include at least the
followings:
.1 checking and use of personal protective equipment required for entry;
.2 checking and use of communication equipment and procedures;
.3 checking and use of instruments for measuring the atmosphere in enclosed
spaces;
.4 checking and use of rescue equipment and procedures; and
.5 instructions in first aid and resuscitation techniques.
2.2.6 The company should establish criteria to manage additional risks involved during
simultaneous operations (SIMOPS) where one of the operations includes an enclosed
space entry. The company should ensure that single person entry into an enclosed space
is not permitted.
2.3 Amendment of Assessment of Risk and Authorization of Entry
2.3.1 The company should ensure identify all enclosed spaces on board the ship and that
the identified enclosed spaces are recorded in the Enclosed Space Register, which
should be maintained on board the ship as well as ashore. This Enclosed Space Register
and risk assessment should be kept up to date as appropriate to ensure its continued
validity, particularly after loading and during the carriage of cargoes which may adversely
affect the safety of the atmosphere within a space. A reassessment should also be made
when the contents of the space change. The company should consider the use of
appropriate technology to assist in the hazard identification and mitigation.
2.3.2 The Enclosed Space Register and risk assessment should form the basis of the
development of the enclosed space emergency response plan. The appendix 1 of New
Resolution shows the example of enclosed space emergency response plan. It is
recommended that the enclosed space emergency response plan be reviewed after each
drill so that its effectiveness can be assessed and, if necessary, improvements made.
2.3.3 The risk assessment should determine the potential for the presence of an
oxygen-deficient, oxygen-enriched, flammable or toxic atmosphere, which includes
carbon monoxide (CO) and carbon dioxide (CO2) as well as other toxic or asphyxiant
gases.
2.3.4 The nature of the hazards that may be present should be fully understood by those
on board the ship, both crew and shore-based personnel, and those ashore managing the
ship.
2.3.5 Where the assessment indicates minimal risk to health or life or potential for a risk to
arise during the course of work in the space, the precautions described in sections 5 to 8
and 10 should be followed, as appropriate. The New Resolution added section 10 which is
Hazards Related to Specific Types of Ships or Cargo.
2.3.6 The validity of the entry into enclosed space permit should be specified based on the
risk assessment and should never be longer than 8 hours. For high risk activity, additional
permits may be required. These permits include energy isolation permits, electrical
isolation permit, hot work permit, working at height permit, etc.
2.3.7 Shore personnel should be provided with information on the hazards associated with
enclosed spaces that may be present aboard the ship.
2.4 General Precautions
2.4.1 Access to enclosed spaces should be carefully managed on ships where shore
personnel regularly enter cargo spaces to load and discharge cargoes. It is recommended
that a basic schematic plan of the ship’s spaces should be placed at the gangway or at
other access points of the ship clearly indicating which spaces are safe to enter, and
which spaces are not. The plan should outline the enclosed space entry procedures that
should be complied with by both ship and shore personnel before any entry is permitted.
The use of simple safe to enter and unsafe to enter symbols is recommended.
2.4.2 The item 6.5 in New Resolution amended 10 safety measures for entry to enclose
space. One of the safety measures specifying that gas detection instruments must be
certified and calibrated. If the testing indicates that the level of oxygen is less than 20.9%,
or indicates the presence of even low levels of flammable or toxic gases, then the space
should be treated as one where the atmosphere is known or suspected to be unsafe.
Entering into this enclose space should take additional precautions as described in New
Resolution section 9. The responsible person authorizing entry should determine whether
personal gas detectors, an attendant and the positioning of rescue equipment at the
entrance to the space are necessary. Personal gas detection instrument or instruments
should be calibrated, tested and 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.
2.4.3 The item 6.7 in New Resolution specifies the attendants and rescue teams should
be trained as 12 items.
2.4.4 As far as practicable, enclosed space entry should be carried out during hours of
daylight or normal working hours of the ship to ensure ready availability of reserve
personnel in the event of an emergency.
2.5 Amendment of Testing the Atmosphere
2.5.1 New Resolution item 7.1, 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. The gas detection
equipment, including devices for testing CO2, should be capable of operating correctly
even in oxygen-depleted atmosphere.
2.5.2 New Resolution item 7.3 specifies the number requirement of gas detection
equipment. All ships should carry at least two sets of gas detection equipment as required
by SOLAS regulation XI-1/7. Any ship which may carry a cargo capable of generating
hazardous vapours and which requires regular entry into the cargo space for cleaning or
inspection should carry two sets of gas detection equipment in addition to those required
by SOLAS regulation XI-1/7 for assessing the risk to personnel entering the space.
2.5.3 New Resolution item 7.3 amended the requirement gas concentration of enclosed
space atmosphere, added the requirement of carbon dioxide (CO2), detail as follows:
.1 20.9% oxygen by volume;
.2 the level of carbon dioxide has been checked and is less than 0.5% by volume
(5,000 ppm);
.3 less than 1% of lower flammable limit (LFL) on a suitably sensitive combustible gas
indicator; and
.4 less than 50% of the occupational exposure limit (OEL) of any toxic vapours and
gases.
2.6 Amendment of Additional Precautions for Entry into A Space where The Atmosphere
is Known or Suspected to be Unsafe
2.6.1 New Resolution item 9.2, when the planned work activity within an enclosed space
where the atmosphere is known or suspected to be unsafe, suitably designed and
constructed breathing apparatus of positive pressure type should always be worn, and
only personnel trained in its use should be allowed to enter the space. Emergency Escape
Breathing Devices (EEBDs) are not suitable to use for entry into enclosed spaces.
2.6.2 New Resolution item 9.3, persons entering enclosed spaces that may contain a
suspected atmospheric hazard should be provided with calibrated and tested personal
gas detector suitable for the gas or gases assessed as likely to occur in the space.
2.7 Amendment of Hazards Related to Specific Types of Ships or Cargo
2.7.1 For solid bulk cargo, paid particular attention to enclosed hold access trunks, for
example enclosed Australian Ladder. The enclosed Australian ladder access should not
be used until it has been fully ventilated, tested and confirmed to be safe. When a cargo
which may generate a hazardous atmosphere is loaded, the access door/hatch should be
locked with a dedicated and unique locking arrangement, distinct from all other such
arrangements, from the commencement of loading until the space is certified safe for
entry by testing after completion of discharge. Additionally, Entry of personnel into a cargo
hold using a hold vertical ladder should only be permitted when:
.1 the atmosphere in the hold has been tested and found to be safe;
.2 wearing a personal gas detector;
.3 wearing a safety harness; and
.4 an emergency response plan is in place.
2.7.2 New Resolution item 10.4 to 10.6 added information for hazards related to steel,
specific dangers associated with carbon dioxide, and information on acceptable and
unacceptable levels of gases.
2.8 New added Action to Be Taken in The Event of An Emergency
New Resolution added section 11, provide the guideline for action to be taken in the event
of an emergency.
2.8.1 In the event of an emergency in an enclosed space the ship’s crew should follow the
ship-specific enclosed space emergency response plan. In an emergency the ship’s crew,
or any shore personnel, should NEVER perform rescue entering an enclosed space
independently, but should always follow the agreed rescue plan.
2.8.2 The ship has an enclosed space emergency response plan, which is easily
understood, regularly practiced, verified as effective and followed precisely. The
emergency response plan should form a part of the company safety management system
(SMS).
2.8.3 Equipment should be provided for the ship’s crew to utilize in the event of an
enclosed space accident. Such equipment should fall into three main categories:
.1 Equipment to test and verify the enclosed space atmospheric conditions and
determine the hazards to life and the mitigations necessary prior to entry;
.2 Equipment to ensure the safety of the rescue party such as self-contained
breathing apparatus (SCBA), lifelines, harness, etc.; and
.3 Equipment to facilitate the safe recovery of a casualty, such as recovery hoist,
stretchers and resuscitation equipment.
3. Action Recommendations
Considering the New Resolution has given comprehensive revision to requirement for
entry into enclose spaces on board ships, we suggest ship-owners, management
companies, crew members, and personnel conducting shipboard operations prioritize and
implement the following requirements:
1. Company shall establish or enhance SMS in accordance with the New Resolution,
including creating an Enclosed Spaces Register and developing emergency response
plan. This includes updating procedures for hazard identification, risk assessment,
authorized entry, precautions, gas detection, and training/drills.
2. Company should ensure shore-based support by providing all necessary equipment
and instruments for enclosed space entry onboard, particularly gas detection equipment
and personal gas detector compliant with the New Resolution. They must also ensure all
relevant information regarding enclosed space entry is provided to the ship and necessary
technical support is available.
3. The company shall enhance crew member training to ensure all personnel, especially
competent persons, responsible persons, attendants, and crew members with enclosed
space entry or rescue duties, undergo necessary training to achieve competency for their
responsibilities.
4. Crew members shall strictly implement the relevant requirements of SMS concerning
enclosed space entry, particularly mastering the requirements revised in accordance with
the New Resolution and applying them during operations.
5. Ship should enhance enclosed space rescue and emergency drills to enable proactive
response measures during emergencies.
6. Personnel boarding ship for operations should understand and comply with requirement
concerning enclosed space entry onboard ship to ensure operational safety.
Simultaneously, revoke the Technical Information issued by our Society, REVISED
RECOMMENDATIONS FOR ENTERING ENCLOSED SPACES ABOARD SHIPS - IMO
Resolution A.1050(27)” (2012 Technical Information No.11 Total No.11)

above from: CCS