Resolution MSC.581(110) – Revised Recommendations for Entering Enclosed Spaces Aboard Ships – was adopted by the International Maritime Organization (IMO) during the 110th session of the Maritime Safety Committee (MSC 110) in June 2025 and entered into force on 3 December 2025. The new resolution fully replaces the previous A.1050(27) resolution and introduces significant updates to safety standards for enclosed space entry on ships, with carbon dioxide (CO₂) monitoring now explicitly required as a mandatory measure.
I. Core Requirement: CO₂ Becomes a Mandatory Indicator
The most notable change in the new regulations is the inclusion of carbon dioxide (CO₂) as a mandatory pre-entry measurement, alongside oxygen, flammable gases, and toxic gases. Specific quantitative thresholds have been established:
| Parameter | Safe Entry Threshold | Remarks |
|---|---|---|
| Carbon Dioxide (CO₂) | < 0.5% by volume (5,000 ppm) | New mandatory measurement item |
| Oxygen (O₂) | 20.9% by volume | Near normal atmospheric level |
| Flammable gases/vapours | < 1% of lower flammable limit | — |
| Toxic gases/vapours | < 50% of occupational exposure limits | e.g., carbon monoxide (CO) |
II. Equipment and Configuration Requirements
The new regulations impose stricter requirements for gas detection equipment:
Equipment Capability: Ships must be equipped with portable gas detectors capable of simultaneously measuring oxygen, flammable gases, carbon monoxide, and carbon dioxide.
Quantity Requirements: Under the International Convention for the Safety of Life at Sea (SOLAS), every ship must carry at least two sets of gas detection equipment. Ships carrying cargoes that may generate hazardous atmospheres are required to carry two additional sets.
III. Enhanced Management Framework
Beyond measurement requirements, the new regulations systematically strengthen the management framework for enclosed space operations:
Connected Space Management: The concepts of “connected space” and “adjacent space” are introduced. Any space connected to a hazardous space through doors, openings, piping, or other means must be treated as a hazardous space and subjected to independent testing and ventilation; entry decisions cannot be based on prior experience alone.
Enclosed Space Register: Each ship must establish and maintain a dedicated Enclosed Space Register, listing all enclosed spaces on board and their associated hazards. The register must be kept on board and retained ashore.
Strict Permit-to-Work System: Entry into enclosed spaces requires a permit that is valid for no more than eight hours. The permit must be accompanied by a detailed risk assessment and signed by the master or a designated responsible officer.
Prohibition of Lone Entry: The new regulations explicitly prohibit lone entry into enclosed spaces. A dedicated attendant must be stationed outside during entry operations.
Emergency Response Plan: Each ship must develop a specific Enclosed Space Emergency Response Plan and conduct regular rescue drills.
IV. Important Considerations
The following points require particular attention during implementation of the new regulations:
EEBD for Escape Only: Emergency Escape Breathing Devices (EEBDs) are to be used solely for emergency escape and are strictly prohibited from being used as breathing apparatus for entry into enclosed spaces.
Cargo-Related Hazards: When carrying cargoes such as coal, wood products, grain, or scrap metal, the relevant spaces may generate hazardous concentrations of carbon dioxide or experience oxygen depletion due to cargo characteristics. A thorough risk assessment must be conducted prior to entry.
As a professional solution provider for gas environment safety monitoring, Henan Chicheng Electric Co., Ltd. (Stock Code: 834407) is well-positioned to assist the maritime industry in complying with the latest IMO regulations. Founded in 2004 and listed on the Beijing Stock Exchange in February 2023, Chicheng is a nationally recognized “Specialized and Sophisticated Little Giant” enterprise with over 20 years of experience in gas detection technology.
The company has established a comprehensive industrial chain covering gas sensors, intelligent instruments, and IoT cloud platforms, supported by a manufacturing base of over 60,000 square meters and a team of more than 300 employees. Chicheng holds over 300 patents and professional certifications, with its products widely applied in industries such as petrochemical, metallurgy, electric power, and shipbuilding.
Recommended Products for IMO Compliance
To meet the new requirements for simultaneous detection of oxygen (O₂), flammable gases, carbon monoxide (CO), and carbon dioxide (CO₂), Chicheng offers the following portable multi-gas detectors:
GC310 Multi-Function Gas Detector
Detection Capability: Supports up to 4 gas channels simultaneously, including CO₂, O₂, CO, and combustible gases
Key Features: Pre-calibrated sensors for plug-and-play operation, automatic LEL/VOL switching for combustible gas channels, LCD graphic display, and optional built-in pump for confined space sampling
Applications: Specifically suitable for shipbuilding, shipping, petrochemical, and confined space entry operations
Protection Rating: IP66, ensuring reliable operation in harsh marine environments
Why Choose Chicheng
Proven Expertise: Over two decades of specialization in gas detection technology
Quality Assurance: Full compliance with international standards, backed by ISO9001:2008 certification
Comprehensive Support: 24/7 after-sales service with rapid response capability
End-to-End Solutions: From sensor manufacturing to IoT-enabled monitoring systems, all under one roof
For more information on how Chicheng’s gas detection solutions can help your fleet achieve full compliance with IMO Resolution MSC.581(110), please visit the official website at https://www.ccesafety.com/
