Catalytic vs NDIR Methane Sensors: Which Is Better?

Continuous methane monitoring is required in applications where gas release may occur during normal operation or as a result of equipment failure, including:

• Oil and gas production, transportation, and processing facilities;
• Chemical plants and refineries;
• Underground mining and drilling operations;
• Biogas, landfill, and wastewater treatment systems;
• Building safety systems, including HVAC and gas leak detection in residential and commercial premises.

In these applications, methane sensors are used to provide early leak detection, support automated safety responses, and enable compliance with explosion protection and functional safety requirements. Depending on the installation type, applicable regulations typically include ATEX and IECEx schemes for explosive atmospheres, as well as regional certification frameworks for industrial gas detection equipment.

Methane sensors measure gas concentration using either chemical or optical detection principles. The two most widely used technologies are catalytic (pellistor) sensors and non-dispersive infrared (NDIR) sensors, which are based on fundamentally different physical mechanisms.

Catalytic sensors detect methane through controlled oxidation on a heated catalytic element.NDIR sensors determine methane concentration by measuring infrared light absorption at characteristic wavelengths.

The choice between these technologies is driven by the required measurement range, environmental conditions, and acceptable maintenance level.

Catalytic sensors measure methane concentration through controlled oxidation on a catalyst-coated heated element. When methane is present, oxidation increases the temperature of the sensing bead, causing a change in electrical resistance that is converted into a gas concentration signal, typically expressed as %LEL.

Main features:

• Measurement range: typically 0–100% LEL
• Response time: fast under diffusion conditions (commonly 5–15 s T90 in practical installations)
• Oxygen requirement: required to sustain the oxidation process

• Long-established and well-understood technology
• Effective for LEL-based explosion protection systems
• Relatively low initial sensor cost

• Requires regular calibration to compensate for catalyst aging
• Susceptible to catalyst poisoning (e.g. silicones, sulfur- and lead-containing compounds)
• Limited operational lifetime, typically 2–5 years

NDIR (Non-Dispersive Infrared) sensors measure methane concentration by detecting absorption of infrared radiation at characteristic wavelengths around 3.3 µm, corresponding to CH₄ molecular vibration bands. The gas concentration is calculated from the attenuation of the infrared signal passing through the measurement path.

Main features:

• Measurement range: from ppm levels up to percent or full-volume ranges, depending on optical configuration
• Oxygen requirement: not required
• Response time: typically 10–30 s T90 in practical diffusion-based designs

Advantages:

• High long-term stability due to non-consumptive measurement principle
• Independent of oxygen concentration
• Immune to chemical poisoning affecting catalytic sensors
• Low maintenance requirements
• Long operational lifetime, typically exceeding 10 years

Limitations:

• Higher initial cost compared to catalytic sensors
• Sensitivity to optical contamination if diffusion openings or optical surfaces are not properly protected

Typical applications:
Continuous methane monitoring in industrial automation systems, HVAC and building safety installations, biogas and wastewater facilities, and low-power or networked (IoT) gas detection devices.

Catalytic sensors are appropriate when:

• Detection is focused on concentrations near the Lower Explosive Limit (LEL);
• The system is designed around LEL-based safety logic;
• Regular calibration and sensor replacement are acceptable operationally.

• Continuous measurement and long-term stability are required;
• Operation in oxygen-deficient or variable atmospheres is expected;
• Low power consumption and digital interfaces are needed;
• Maintenance access is limited and long service life is critical.

• Catalytic sensors: improved resistance to catalyst poisoning, enhanced self-diagnostic functions, and more compact sensor designs.
• NDIR sensors: reduced power consumption through solid-state and MEMS-based infrared sources, increased integration of digital interfaces, and support for multi-gas measurement within a single optical platform.

Methane sensors used in industrial safety applications are subject to international regulations governing operation in explosive and hazardous environments.

• ATEX and IECEx — certification schemes for equipment intended for use in explosive atmospheres in industrial facilities.
• IEC / EN 60079 series — standards defining requirements for intrinsic safety (Ex ia), flameproof protection (Ex d), and optical radiation safety for gas detection equipment.
• UL and CSA standards — North American certification frameworks for hazardous location equipment used in industrial safety systems.

Catalytic and NDIR methane sensors are both established technologies in industrial gas detection, each addressing different operational requirements.

Catalytic sensors remain appropriate for LEL-based explosion protection systems where oxygen is present and regular calibration and maintenance are part of normal operation.

NDIR sensors are well suited for continuous industrial monitoring, particularly in applications requiring long-term stability, low maintenance, and reliable operation in oxygen-deficient or chemically aggressive environments.

In industrial safety practice, the choice between catalytic and NDIR technologies should be based on system architecture, maintenance strategy, environmental conditions, and lifecycle cost, rather than on the sensing principle alone.