Why is CO₂ now required in maritime gas detection systems?

CO₂ is now required in maritime gas detection systems because IMO Resolution MSC 581(110), endorsed in December 2025, made CO₂ monitoring a mandatory pre-entry testing parameter for enclosed spaces on board ships. This closes a long-standing gap: the older “4-in-1” detectors measuring O₂, LEL, CO, and H₂S are no longer sufficient on their own. Below, we answer the most common questions about what this means for your vessel and your gas detection setup.

Which regulations now mandate CO₂ detection on ships?

IMO Resolution MSC 581(110), titled the Revised Recommendations for Entering Enclosed Spaces on Board Ships, is the regulation that now mandates CO₂ detection. Endorsed on 3 December 2025, it supersedes the older Resolution A 1050(27) and sets a new compliance standard for confined space safety across the maritime industry. RightShip RiSQ version 3.2 has already integrated these requirements into its inspection scope.

While SOLAS Regulation XI-1/7 has long required ships to carry portable gas detectors, the industry previously operated under the non-binding recommendations of A 1050(27). MSC 581(110) changes that. It explicitly mandates the ability to test for four gases before any enclosed space entry: Oxygen (O₂), flammable gases (LEL), Carbon Monoxide (CO), and Carbon Dioxide (CO₂). Entry is only permitted when CO₂ levels are confirmed below 0.5%, which equals 5,000 parts per million (ppm).

This is not a routine administrative update. For shipowners and technical superintendents, MSC 581(110) is a high-priority safety mandate that requires immediate attention to onboard gas detection capabilities.

What are the risks of undetected CO₂ buildup in enclosed ship spaces?

Undetected CO₂ buildup in enclosed ship spaces is a direct asphyxiation risk. CO₂ is colorless and odorless, meaning crew members can lose consciousness without any warning. At concentrations above 5,000 ppm, exposure becomes dangerous within minutes. At higher levels, it is fatal. The risk is especially serious because CO₂ is heavier than air and accumulates in low-lying areas such as cargo holds, bilge spaces, and pump rooms.

One of the most important clarifications in MSC 581(110) is that a space does not need to contain inherently dangerous cargo to become lethal. Ordinary rusting – the oxidation of iron in a damp, confined environment – rapidly consumes oxygen and elevates CO₂ levels. A cargo of scrap metal or even the ship’s own bare steel structure, combined with moisture, can create a dangerous atmosphere within days.

The regulation also highlights that gas does not respect physical boundaries. Connected spaces (linked by doors, trunks, or manholes) and adjacent spaces (sharing a common bulkhead) must both be treated as potentially hazardous. Bulkhead corrosion, seal failure, or even a small gap around a manual watertight door can allow gas to migrate into spaces that appear safe. Every connection point must be independently ventilated and confirmed clear before entry.

It is also worth noting that more than half of enclosed space fatalities are would-be rescuers. Unplanned rescue attempts are now strictly prohibited under MSC 581(110), which is exactly why reliable, real-time CO₂ monitoring matters so much before anyone steps inside.

How does a CO₂ gas detection system work on a vessel?

A CO₂ gas detection system on a vessel works by continuously sampling the atmosphere in a defined space and measuring CO₂ concentration using a sensor that generates an alert when levels exceed a set threshold. For maritime compliance under MSC 581(110), the required measurement resolution is at the parts per million (ppm) level, which makes sensor technology selection critically important.

The current benchmark technology for compliant CO₂ detection is Non-Dispersive Infrared (NDIR) sensing. Here is why that matters:

Traditional electrochemical sensors are designed for percent-range measurements and lack the resolution to accurately detect CO₂ at the 5,000 ppm regulatory limit.
NDIR sensors use an infrared light source and a detector to measure how much CO₂ absorbs the light at a specific wavelength, providing stable, high-resolution ppm readings.
NDIR technology is not affected by oxygen depletion, making it reliable in exactly the kind of low-oxygen environments where enclosed space hazards occur.

On a vessel, CO₂ detectors are typically used as portable instruments during pre-entry testing, carried to each measurement point listed in the ship’s Enclosed Space Register. Fixed detection systems may also be installed in high-risk spaces such as cargo holds or refrigerated compartments. Either way, the readings must be officially recorded before an entry permit is issued. Under MSC 581(110), an unrecorded test is treated by Port State Control as a test that never happened.

What’s the difference between CO₂ detection and CO₂ suppression systems?

CO₂ detection and CO₂ suppression systems serve completely opposite purposes. CO₂ detection measures the concentration of carbon dioxide in the atmosphere to protect crew from dangerous exposure. CO₂ suppression systems deliberately release CO₂ in high concentrations to extinguish fires by displacing oxygen. Confusing the two is a serious safety risk.

Here is a clear comparison:

CO₂ detection: Monitors ambient CO₂ levels, alerts crew when concentrations approach dangerous thresholds, and is used to confirm a space is safe to enter. Operates continuously or during pre-entry testing.
CO₂ suppression: A fixed firefighting system that floods an enclosed space (such as an engine room or cargo hold) with CO₂ to extinguish fire. The space becomes immediately lethal to anyone inside.

This distinction matters practically: a space protected by a CO₂ suppression system requires its own specific pre-entry procedures and must be listed in the ship’s Enclosed Space Register with its hazard source clearly identified. After a suppression system has been activated, CO₂ detection equipment is needed to confirm the atmosphere has been fully ventilated before any crew member can safely re-enter.

Which CO₂ detectors are compatible with existing shipboard gas detection panels?

Whether a CO₂ detector is compatible with an existing shipboard gas detection panel depends on the panel’s communication protocol, power supply requirements, and sensor interface type. Most modern gas detection panels support 4-20 mA analog output or digital protocols such as Modbus, and NDIR-based CO₂ sensors are available in both formats, making integration with existing systems achievable in most cases.

For portable gas monitors, the situation is more straightforward: many current multi-gas instruments can be upgraded with an NDIR CO₂ sensor module, replacing or supplementing the standard H₂S sensor slot. However, not all legacy 4-in-1 instruments support this upgrade, and it is important to verify with the manufacturer or a specialist supplier whether your specific model can be retrofitted.

For fixed detection systems, compatibility depends on the panel brand and generation. Older panels may require a signal converter or a dedicated CO₂ transmitter with an analog output that the panel already supports. Our service and repair team regularly assesses existing installations to identify the most practical integration path, avoiding unnecessary full-system replacements where a targeted upgrade is sufficient.

When evaluating compatibility, check for these key specifications:

Output signal type (4-20 mA, 0-10 V, or digital protocol)
Power supply voltage (typically 12 V or 24 V DC)
Measurement range (must cover 0 to at least 5,000 ppm for MSC 581(110) compliance)
ATEX or IECEx certification if the detector is installed in a potentially explosive atmosphere
MED (Marine Equipment Directive) or classification society type approval

When should a ship’s CO₂ detection system be upgraded or replaced?

A ship’s CO₂ detection system should be upgraded or replaced when it can no longer measure CO₂ at the ppm level required by MSC 581(110), when sensors are beyond their calibration life, or when the system is no longer supported by the manufacturer. With the 2025 regulation now in force, any vessel still relying solely on a standard 4-in-1 detector without CO₂ capability is already out of compliance.

Beyond regulatory compliance, consider an upgrade or replacement in the following situations:

The existing portable gas monitor does not support an NDIR CO₂ sensor module and cannot be retrofitted
Fixed detection panels are end-of-life and spare parts or firmware updates are no longer available
Sensors are past their recommended replacement interval (typically 2 to 3 years for electrochemical cells, longer for NDIR)
The system has failed calibration checks or shows drift that cannot be corrected
A Port State Control inspection has flagged the detection setup as non-compliant
The ship’s cargo profile or trading pattern has changed, increasing exposure to oxygen-depleting environments

Replacement does not always mean a full system overhaul. In many cases, a targeted sensor upgrade or the addition of a dedicated CO₂ transmitter is enough to bring an existing installation into compliance. The key is to assess the current system against the specific requirements of MSC 581(110) before deciding on the scope of work.

How Lavastica helps with CO₂ gas detection compliance

We work with fleet engineers and technical superintendents who need practical solutions fast, not lengthy procurement processes. Whether you need a single portable CO₂ detector, a retrofit sensor for an existing panel, or a complete gas detection system upgrade, we can help you find what works with your current onboard installation.

Large stock in Rotterdam: We hold a wide range of gas detection equipment, including NDIR-based CO₂ detectors and multi-gas monitors, ready for fast worldwide delivery
Compatibility assessment: We advise on which detectors and transmitters integrate with your existing panels and systems, minimizing unnecessary replacements
Obsolete equipment: We specialize in sourcing and managing end-of-life products, including refurbished equipment and suitable alternatives for discontinued models
Technical support: Our team has direct knowledge of maritime regulations and can advise on MSC 581(110) compliance requirements for your specific vessel type
Emergency service: When a ship is in port and time is short, we prioritize fast response and delivery to minimize idle days

Want to know which CO₂ detection solution fits your current setup? Learn more about us or get in touch with our team directly. We are happy to think along with you.

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