Which gas detection systems comply with current SOLAS requirements?

Gas detection systems on ships must comply with SOLAS Chapter II-2, which sets out fire protection, detection, and extinction requirements, and with IMO Resolution MSC 581(110), which governs enclosed space entry and atmospheric testing. To meet current standards, a system must be able to detect at least four gases: oxygen (O2), flammable gases (LEL), carbon monoxide (CO), and carbon dioxide (CO2). The sections below break down exactly which regulations apply, what equipment is required, and how to check whether your current setup still makes the grade.

What SOLAS regulations apply to gas detection on ships?

The main SOLAS framework for gas detection sits in Chapter II-2, covering fire protection and detection systems across all vessel types. Alongside this, IMO Resolution MSC 581(110) — the Revised Recommendations for Entering Enclosed Spaces on Board Ships — introduced significant updates to atmospheric monitoring requirements for confined space entry. Together, these two frameworks define what gas detection equipment ships must carry and how it must be used.

MSC 581(110) supersedes the older Resolution A.1050(27) and brings a more rigorous, science-based approach to confined space safety. One of its most important concepts is Closed-Loop Management: safety must be verifiable, continuously monitored, and backed by a documented rescue framework. This is not just a checklist exercise. Port State Control inspectors treat an unrecorded atmospheric test the same as a test that never happened.

The regulation also expands the definition of what counts as a risk area. Beyond the primary space being entered, ships must now assess connected spaces (such as cargo hold stairways, pipe tunnels, or any area linked via a door, manhole, or pipe) and adjacent spaces sharing a common bulkhead with a hazardous area. Structural corrosion, coating damage, or weld seepage can allow gas to migrate into nominally safe zones, so both types of space must be treated as hazardous until confirmed otherwise.

Classification societies including Lloyd’s Register, DNV, and Bureau Veritas translate these IMO requirements into their own rule sets, so the exact technical specifications for your vessel may also depend on the society under which it is classed.

Which types of gas detectors are required under SOLAS?

Under current SOLAS and MSC 581(110) requirements, ships must be able to test for four specific gases before enclosed space entry is permitted: oxygen (O2), flammable gases expressed as a percentage of the Lower Explosive Limit (LEL), carbon monoxide (CO), and carbon dioxide (CO2). Entry into an enclosed space is only permitted when CO2 levels are confirmed below 0.5% (5,000 parts per million).

This is where many existing setups fall short. The maritime industry has long relied on “4-in-1” portable detectors that monitor LEL, O2, CO, and hydrogen sulfide (H2S). These units are widely used and well understood, but most cannot detect CO2. Under MSC 581(110), that gap is no longer acceptable. Ships relying solely on legacy 4-in-1 units without a separate CO2 detection capability do not meet the current standard.

Beyond portable detectors for enclosed space entry, SOLAS Chapter II-2 also requires fixed fire and gas detection systems in machinery spaces, cargo pump rooms, and other defined areas depending on vessel type. These fixed systems typically use point detectors, open-path detectors, or catalytic bead sensors depending on the application and the gases present.

What certifications must a SOLAS-compliant gas detection system have?

A gas detection system used on a SOLAS-regulated vessel must carry type approval from a recognized classification society. This approval confirms that the equipment has been independently tested and meets the performance standards set out in the relevant IMO guidelines and IEC/EN standards for marine environments.

For portable gas detectors used in enclosed space entry, the relevant performance standard is generally IEC 60079 (for equipment used in explosive atmospheres) alongside ATEX or IECEx certification where applicable. Fixed detection systems are typically evaluated against IMO MSC/Circ.1432 and related fire detection standards.

Key certifications to look for include:

MED (Marine Equipment Directive) approval for vessels flagged in EU member states
Classification society type approval from DNV, Lloyd’s Register, Bureau Veritas, or another recognized organization
ATEX or IECEx certification for use in potentially explosive atmospheres
SIL (Safety Integrity Level) rating where required for safety-critical fixed systems

Always verify that the certification covers the specific gases the unit is intended to detect. A detector approved for LEL and O2 monitoring is not automatically approved for CO2 detection, even if a CO2 sensor is physically added to the unit.

Do older gas detection systems still meet current SOLAS standards?

Many older gas detection systems do not fully meet current requirements, particularly following the introduction of MSC 581(110). The most common gap is the absence of CO2 detection capability. Legacy 4-in-1 detectors that monitor LEL, O2, CO, and H2S were compliant under the previous framework, but the new resolution explicitly requires CO2 monitoring as a condition of enclosed space entry.

Beyond gas coverage, older systems may also fall short in other areas:

Data logging: MSC 581(110) requires atmospheric test results to be recorded and verified. Units that do not store or output test data create a compliance gap.
Calibration records: Port State Control inspectors look for documented calibration histories. Equipment without traceable calibration records is a liability during inspections.
Type approval status: Some older units may have held type approval under superseded standards. If the approving classification society has withdrawn or updated that approval, the unit may no longer be accepted.

That said, not every older system is automatically non-compliant. Fixed fire and gas detection panels with valid, current type approval may still meet requirements if they cover the correct detection zones and gas types. The key question is always whether the system’s approval certificate remains valid and whether it covers all gases now mandated by the applicable regulations. Our service and repair team can assess existing equipment and advise on whether recalibration, an upgrade, or replacement is the right path forward.

How do you verify a gas detection system is SOLAS compliant before installation?

Before installing any gas detection system on a SOLAS-regulated vessel, check three things: the equipment holds a valid type approval certificate from a recognized classification society, the approval covers the specific gases required for your vessel type and trading area, and the unit meets any additional flag state requirements that apply to your ship’s registration.

Here is a practical verification checklist:

Request the type approval certificate from the supplier and confirm it is issued by a recognized classification society (DNV, Lloyd’s Register, Bureau Veritas, ABS, etc.).
Check the approval scope — confirm which gases and concentration ranges are covered. CO2 detection must be explicitly included if the unit will be used for enclosed space entry.
Verify the certificate is current — type approvals have expiry dates and can be withdrawn or superseded when standards are updated.
Confirm MED compliance if the vessel is EU-flagged, as this is a separate requirement from classification society approval.
Check compatibility with existing systems — particularly for fixed systems, verify that new detectors or panels are compatible with the existing alarm panels and zone configurations already installed on board. Replacing a single detector with an incompatible unit can create integration problems across the whole system.
Review flag state requirements — some flag states impose additional or stricter requirements beyond the IMO baseline. Confirm with your flag administration or class surveyor before purchasing.

When in doubt, ask your supplier to provide written confirmation of compliance for your specific vessel type, flag, and class. A supplier who cannot provide this documentation clearly is not the right partner for safety-critical equipment.

How we help with SOLAS-compliant gas detection

At Lavastica, we work with fleet engineers and technical superintendents every day who need reliable answers fast, especially when a ship is in port and time is money. Here is what we offer:

Verified, type-approved equipment from more than 100 brands, including portable detectors with CO2 capability and fixed systems for all vessel types
Compatibility checks before supply, so new equipment integrates with your existing panels and zone configurations without surprises
Replacement advice for obsolete systems, including reconditioned equipment and custom-made solutions where standard products are no longer available
Technical support and commissioning to make sure the system works correctly from day one
Fast worldwide delivery from our Rotterdam warehouse, minimizing the time your vessel spends in port

Want to know whether your current gas detection setup meets the latest requirements? Learn more about our expertise or get in touch with our team directly. We are happy to review your situation and give you a straight answer.

Phone: +31 (0) 10 265 5070Email: [email protected]