Infrared (IR) sensors detect gas by measuring how much infrared light a gas absorbs at a specific wavelength, while catalytic bead sensors detect gas by measuring the heat released when a flammable gas burns on a heated catalyst. These are two fundamentally different detection principles, and choosing the right one depends on the gases you need to monitor, the environment onboard, and your existing gas detection panel. The sections below walk through the key differences so you can make a well-informed decision for your vessel.

How does each sensor type actually detect gas?

Catalytic bead sensors work by exposing a small heated element, coated with a catalyst, to the surrounding air. When a flammable gas reaches the sensor, it oxidises on the catalyst surface and generates heat. That temperature rise changes the electrical resistance of the bead, and the detector converts that change into a gas concentration reading. It is a straightforward, proven method that has been used in maritime and industrial gas detection for decades.

Infrared sensors take a completely different approach. They shine an infrared light beam through a sample chamber. Because different gas molecules absorb infrared energy at specific wavelengths, the sensor can measure how much light reaches the detector on the other side. Less light arriving means more gas is present. This optical method requires no combustion, which is one of the reasons it performs well in environments where oxygen levels may vary.

Which gases can infrared and catalytic sensors detect?

Catalytic bead sensors can detect most flammable gases and vapours, including methane, propane, butane, hydrogen, and many hydrocarbon vapours. They are versatile across a broad range of combustible substances, which makes them a popular general-purpose choice for flammable gas monitoring on vessels.

Infrared sensors are also well suited for flammable hydrocarbon gases, but they have an additional advantage: they can detect certain non-flammable gases such as carbon dioxide (CO2). However, IR sensors cannot detect hydrogen because hydrogen does not absorb infrared light in a way that standard IR sensors can measure. If your application involves hydrogen monitoring, a catalytic sensor is the right tool.

For a broader overview of gas and fire detection systems used in maritime applications, it helps to understand the full range of detection technologies available before committing to a specific sensor type.

What are the main limitations of catalytic bead sensors?

Catalytic bead sensors have two important limitations worth understanding. First, they require oxygen to function. The catalytic oxidation process only works when there is enough oxygen in the atmosphere. In oxygen-depleted environments, such as enclosed cargo spaces or inert gas atmospheres, a catalytic sensor can give a falsely low or zero reading even when dangerous gas concentrations are present.

Second, catalytic sensors are vulnerable to sensor poisoning. Certain substances, including silicones, lead compounds, and some chlorinated solvents, can permanently damage the catalytic bead and reduce its sensitivity. Once poisoned, the sensor may fail to detect gas at all, which is a serious safety risk in maritime environments where maintenance windows are limited.

Why do infrared sensors perform better in harsh environments?

Infrared sensors do not rely on combustion or chemical reactions, so they are not affected by oxygen deficiency or catalytic poisoning. This makes them significantly more reliable in confined spaces, inert atmospheres, and areas with potential chemical contamination. Onboard vessels, where cargo holds, engine rooms, and pump rooms can present exactly these conditions, that reliability matters.

IR sensors also tend to have a longer operational lifespan with fewer false readings caused by environmental interference. They are less sensitive to humidity and temperature extremes, which are common challenges in the maritime sector. For continuous monitoring in demanding locations, infrared technology generally delivers more consistent performance over time.

When should you choose a catalytic sensor over an infrared one?

Catalytic bead sensors are a practical choice when you need to detect hydrogen, or when you are working with a wide range of flammable gases and need a cost-effective solution. They are also the right option when the monitoring location has a stable, sufficient oxygen supply and is unlikely to expose the sensor to poisoning agents.

In applications where budget is a consideration and the environment is relatively clean and well-ventilated, catalytic sensors offer reliable performance at a lower upfront cost than infrared alternatives. Many vessels use a combination of both technologies, placing IR sensors in the most demanding locations and catalytic sensors where conditions are more controlled.

Are infrared and catalytic sensors compatible with the same gas detection panels?

In most cases, yes, but compatibility depends on the specific panel and how it is configured. Many modern gas detection panels support both sensor types through different input modules or signal conditioning cards. However, older panels may have been designed for one technology only, and retrofitting the other type can require additional hardware or firmware updates.

Before replacing or upgrading sensors onboard, it is important to check the panel manufacturer’s specifications and confirm which sensor outputs the system accepts. Swapping sensor technology without verifying panel compatibility is one of the most common sources of integration problems during retrofits. If you are working with an older installation, consulting a specialist familiar with maritime technical equipment can save significant time and prevent costly mismatches.

How we help you choose the right gas detector

Selecting the right sensor technology is not always straightforward, especially when you are managing an existing installation, working under time pressure in port, or dealing with a panel that is no longer in production. We help fleet engineers and technical superintendents navigate exactly these situations. Here is what we offer:

• Expert advice on sensor compatibility with your existing gas detection panels and systems
• Supply of both IR and catalytic gas detectors from more than 100 brands, including hard-to-find and obsolete parts
• Replacement and retrofit support for older installations that need to meet current requirements
• Fast worldwide delivery to minimise your vessel’s time in port
• Technical support on system integration, calibration, and regulatory compliance

Contact us to discuss how we can help you. Visit our Fire & Gas page to explore our full range, or go to our Contact page to speak directly with one of our specialists.