To assess whether a gas detector still meets current standards, you need to check three things: whether the device holds a valid type approval from a recognised classification society, whether it has been calibrated within the required interval, and whether it still responds correctly during a functional test. If any of these three conditions fails, the detector is no longer compliant. For fleet engineers managing ageing installations, this assessment should be part of a structured routine rather than a reactive check when something goes wrong. The sections below walk through each aspect in practical detail.

What regulations govern gas detectors on ships?

Gas detectors on ships are governed primarily by SOLAS (the International Convention for the Safety of Life at Sea), supplemented by the requirements of classification societies such as Lloyd’s Register, DNV, Bureau Veritas, and others. These bodies set the technical standards for type approval, installation, and periodic testing of gas detection equipment. Flag state requirements may add further obligations on top of the baseline SOLAS rules.

In practice, this means a gas detector must carry a valid type approval certificate issued or recognised by the relevant classification society for the vessel. The detector must also be installed and maintained according to the manufacturer’s specifications and the class rules that apply to the ship’s trading area and flag. Regulations in this area do change, so it is worth verifying that the approval your detector holds is still current and accepted by your class surveyor. Our fire and gas detection specialists can advise on which approvals remain valid for specific equipment.

How do you know if a gas detector is still calibrated correctly?

A gas detector is calibrated correctly when it has been tested against a known concentration of reference gas within the manufacturer’s specified interval and the response falls within the accepted tolerance. Calibration records should document the date, the reference gas used, the measured response, and the technician’s sign-off. If this documentation is missing or out of date, the detector cannot be considered compliant regardless of how it appears physically.

Most manufacturers specify a calibration interval of six to twelve months, though this varies by sensor technology and the environment the detector operates in. Detectors in harsh conditions, such as engine rooms or cargo holds with high humidity or chemical exposure, may drift faster and require more frequent checks. A bump test, which briefly exposes the sensor to a small amount of target gas, is a quick way to confirm the sensor is responding, but it does not replace a full calibration. Only a proper calibration with traceable reference gas confirms the detector is reading accurately.

What are the signs that a gas detector no longer meets standards?

The clearest signs that a gas detector no longer meets standards are a lapsed calibration certificate, a failed response during a bump test or functional test, visible physical damage to the sensor head or housing, and the absence of a recognised type approval. Any one of these issues is sufficient to flag the unit as non-compliant.

Beyond documentation failures, there are operational warning signs worth watching for. These include:

• Slow or no response when exposed to the target gas during testing
• Frequent false alarms that cannot be traced to an actual gas source
• Sensor age beyond the manufacturer’s recommended service life, typically three to five years for electrochemical sensors
• Corrosion or contamination on the sensor membrane or housing
• Firmware or software versions that are no longer supported by the manufacturer

A detector showing any of these signs should be taken out of service and assessed before the next port call or inspection.

What is the difference between type approval and calibration compliance?

Type approval and calibration compliance are two separate requirements that both need to be satisfied. Type approval confirms that a detector model has been tested and certified by a classification society as suitable for maritime use. Calibration compliance confirms that a specific unit in service is still measuring accurately. A detector can hold full type approval but still be non-compliant if its calibration is out of date, and vice versa.

Think of type approval as the product-level certificate and calibration as the unit-level certificate. During a class survey, an inspector will check both: the type approval documentation for the model and the calibration records for the individual detectors installed on board. Failing either check can result in a deficiency notice. This is why it is important to maintain both sets of records and keep them accessible during inspections.

When should a gas detector be replaced rather than recalibrated?

A gas detector should be replaced rather than recalibrated when the sensor has reached the end of its service life, when spare parts or replacement sensors are no longer available, when the unit has failed calibration repeatedly, or when the type approval has been withdrawn or is no longer accepted by your classification society.

Recalibration is a cost-effective option when the detector is fundamentally sound and within its service life. But when the underlying sensor technology has degraded beyond recovery, recalibration will not restore reliable performance. The same applies when a model has been discontinued and the manufacturer no longer supports it. Continuing to rely on an unsupported detector creates compliance risk and operational risk simultaneously. In those cases, replacement is the more practical and safer path.

What options exist for replacing an obsolete gas detector?

When a gas detector becomes obsolete, you have three main replacement options: a like-for-like replacement with the same model if stock is still available, a compatible alternative from a different manufacturer that holds the same type approval and integrates with your existing panel, or a broader system upgrade if the panel itself is also approaching end of life.

The most important factor when selecting a replacement is compatibility with your existing gas detection panel and alarm system. A detector that works correctly as a standalone unit but does not communicate properly with the control panel creates a gap in your safety system. Before ordering a replacement, confirm the signal type, addressing protocol, and any panel-specific configuration requirements. Refurbished units from certified sources can also be a practical option for extending the life of an installation when a new equivalent is not available or is cost-prohibitive.

How Lavastica helps with gas detector compliance and replacement

We work with fleet engineers and technical superintendents every day on exactly these questions. Whether you need to verify compliance for an upcoming survey, source a replacement for a discontinued model, or find a compatible alternative that integrates with your existing system, we can help you move quickly and with confidence.

• Large stock of gas detectors and spare parts, including refurbished and hard-to-find obsolete items
• Technical advice on compatibility between replacement detectors and existing panels and zones
• Support with type approval documentation to confirm compliance with your classification society
• Fast worldwide delivery to minimise time in port
• Calibration and service support through our in-house workshop

We supply products from more than 100 brands, which means we can almost always find a solution that fits your installation rather than asking you to replace more than you need to. Visit our Lavastica International overview to see the full range of what we offer. For Fire & Gas equipment specifically, our team is ready to advise on the right replacement or compliance path for your vessel. Contact us to discuss how we can help you keep your fleet compliant and your ships moving.