Evolution of Gas Detector Sensing Technology: How Infrared Technology is Gradually Replacing Catalytic Combustion Sensors

I. Comparison of the principles of the two technologies

1.1 Catalytic Combustion Sensor: Relying on the "Thermal Effect" of Chemical Reactions

The core components of a catalytic combustion sensor are two platinum wire coils coated with catalyst—one is the catalytically active element (detection element), and the other is a passivated reference element (compensation element).

Working principle :

• When combustible gases (such as methane and propane) diffuse to the surface of the detection element, flameless combustion occurs under the action of a catalyst , generating heat.
• Heat causes the resistance of the platinum wire coil to increase.
• The gas concentration is calculated by measuring the resistance difference between the two components using a Wheatstone bridge.

Catalytic combustion sensors are essentially stoichiometric sensors whose output signal is linearly related to gas concentration, making them suitable for detecting most combustible gases (especially alkanes).

1.2 Non-dispersive infrared sensors: "spectral fingerprints" relying on physical absorption

Infrared sensors are based on the Lambert-Beer law —different gas molecules have unique absorption characteristics for specific wavelengths of infrared light.

Working principle :

• An infrared light source emits infrared light of a specific wavelength, which passes through the gas sample.
• The gas being measured (such as methane) exhibits strong absorption at specific wavelengths such as 3.3 μm or 7.6 μm.
• The detector measures the intensity of transmitted light, and the degree of absorption is proportional to the gas concentration.
• Built-in reference channel eliminates the effects of light source attenuation and environmental pollution.

Infrared sensors are a type of physical optical sensor that does not rely on chemical reactions, thus possessing natural advantages in terms of anti-interference and anti-poisoning.

II. Core Advantages of Infrared Technology

2.1 Resistance to poisoning: A fatal flaw in catalytic combustion

The biggest weakness of catalytic combustion sensors is catalyst poisoning .

Poisoning mechanism :

• Silicon-containing compounds (silicone oil, silicone grease, volatiles from silicone rubber)
• Sulfur-containing compounds (hydrogen sulfide, carbon disulfide)
• Lead compounds (leaded gasoline)
• Phosphorus-containing compounds (flame retardants, pesticides)

Even at concentrations in the ppm range, these substances can irreversibly adhere to the catalyst surface, causing a sharp decrease in sensor sensitivity or even complete failure. In complex chemical environments such as chemical plants, oil refineries, and coating plants, the lifespan of catalytic combustion sensors can be shortened to months or even weeks.

Advantages of infrared sensors :

• Based on the principle of physical absorption, without the participation of a catalyst.
• Complete immunity to substances such as silicon, sulfur, lead, and phosphorus
• It can operate stably for a long time in environments containing pollutants or toxic gases.

2.2 No oxygen required: Suitable for oxygen-deficient environments

Catalytic combustion sensors rely on oxygen for the combustion reaction, and their normal operation requires an ambient oxygen concentration of at least 10% Vol . This leads to the complete failure of catalytic combustion sensors in the following scenarios :

• Confined space operations (storage tanks, reactors, cellars)
• Inert gas environmental protection (nitrogen and carbon dioxide purging)
• Oxygen-deficient areas (such as deep mines)

Advantages of infrared sensors :

• The principle of optical absorption does not depend on oxygen.
• It can work normally in oxygen-free environments such as pure nitrogen and argon.
• Suitable for all situations where there is a risk of hypoxia.
• Silicon-containing compounds (silicone oil, silicone grease, volatiles from silicone rubber)
• Sulfur-containing compounds (hydrogen sulfide, carbon disulfide)
• Lead compounds (leaded gasoline)
• Phosphorus-containing compounds (flame retardants, pesticides)

Even at concentrations in the ppm range, these substances can irreversibly adhere to the catalyst surface, causing a sharp decrease in sensor sensitivity or even complete failure. In complex chemical environments such as chemical plants, oil refineries, and coating plants, the lifespan of catalytic combustion sensors can be shortened to months or even weeks.

Advantages of infrared sensors :

• Based on the principle of physical absorption, no catalyst is involved.
• Completely immune to substances such as silicon, sulfur, lead, and phosphorus .
• Can operate stably for extended periods in environments containing pollutants or toxic gases .

2.2 No oxygen required: Suitable for oxygen-deficient environments

Catalytic combustion sensors rely on oxygen for the combustion reaction, and their normal operation requires an ambient oxygen concentration of at least 10% Vol . This leads to the complete failure of catalytic combustion sensors in the following scenarios :

• Operations in confined spaces (storage tanks, reaction vessels, cellars)
• Inert gas protection for the environment (nitrogen and carbon dioxide purging)
• Oxygen-deficient areas (such as deep mines)

Advantages of infrared sensors :

• The principle of optical absorption does not depend on oxygen.
• Can operate normally in oxygen-free environments such as pure nitrogen and argon.
• Suitable for all situations where there is a risk of hypoxia.

2.3 Lifespan and Stability

Performance indicators	Catalytic combustion sensor	Infrared sensor
Typical lifespan	2-5 years	5-10 years
Zero Drift	Significant changes with the environment	Long-term stability
Maintenance frequency	Monthly zero-point calibration	Calibrate every six months to one year.
Failure Mode	Sensitivity attenuation, poisoning failure	Light source attenuation (slow, predictable)

The light source decay of infrared sensors is gradual and predictable, making it easy to develop preventative maintenance plans; while the poisoning failure of catalytic combustion sensors is often sudden and lacks early warning.

2.4 High concentration tolerance and recovery

Catalytic combustion sensors react when encountering gases with a concentration exceeding 100% LEL :

• Oversaturation may occur, leading to zero-point drift.
• In severe cases, it can cause permanent damage.
• Requires prolonged exposure to clean air for recovery.

Advantages of infrared sensors :

• It will not saturate or be damaged at high concentrations.
• Measuring the full range of 0-100% Vol
• Recovers immediately after exposure , no recalibration required.

III. Limitations of Infrared Technology

Despite their clear advantages, infrared sensors still have limitations in certain scenarios, which is why catalytic combustion sensors continue to exist in some fields:

3.1 High initial cost

• Infrared sensor: The cost of a single channel is approximately 2-4 times that of catalytic combustion.
• Composite detectors: Integrating multiple infrared channels is more expensive.

However , when considering the total lifecycle cost (including maintenance, calibration, and replacement), infrared sensors offer a greater long-term economic advantage .

3.2 Limited gas detection range

Infrared sensors are sensitive to gases with asymmetric molecular structures :

• Applicable to : methane, propane, butane, carbon dioxide, sulfur hexafluoride, refrigerants, etc.
• Not applicable : Gases with symmetrical molecules or weak infrared absorption , such as hydrogen, acetylene, carbon monoxide, and ammonia.
• Catalytic combustion sensors still have irreplaceable detection capabilities for the above-mentioned gases.

IV. Market Application: A Substitution Trend Has Been Formed

4.1 Petrochemical Industry

Oil refineries and chemical plants commonly contain catalyst poisons such as sulfides and silicides, and some facilities involve nitrogen purging and oxygen-deficient environments. In recent years, leading companies such as Sinopec and PetroChina have gradually made infrared Combustible Gas Detectors their first choice in new and expanded projects.

4.2 Gas Transmission and Distribution and Municipal Engineering

Urban gas pipeline networks, pressure regulating stations, and gas storage facilities place high demands on the reliability and long lifespan of methane monitoring. Infrared sensors, with their advantages of no risk of poisoning and no need for frequent calibration, significantly reduce operation and maintenance costs. The new national standards GB 15322 series, released in 2026, strengthen anti-interference requirements, further promoting the application of infrared technology.

4.3 Operations in confined spaces

Oxygen deficiency is a common risk in confined space environments such as sewage wells, cellars, and storage tanks, rendering catalytic combustion sensors ineffective. Pump-type portable detectors equipped with infrared sensors have become standard equipment for operations in confined spaces.

4.4 Electricity and New Energy

Infrared technology is widely used in scenarios such as substations (sulfur hexafluoride leakage monitoring) and hydrogen energy facilities (infrared technology is not suitable for hydrogen, but it can be used for environmental methane monitoring). Due to its high precision and long lifespan, infrared technology is widely used.

V. Industry Dynamics Confirm Technological Transformation

Honeywell releases next-generation NDIR sensor (March 2026)

• Specifically designed for detecting methane, propane, and butane.
• Emphasizing anti-poisoning, low power consumption, and anti-condensation design
• Target applications: Mining, oil and gas, petrochemicals, plastics manufacturing
• Added stringent testing items such as salt spray and environmental corrosion tests.
• This forces sensor technology to upgrade towards higher reliability.
• The durability advantages of infrared sensors are recognized at the standards level.

Domestic infrared imaging technology makes its debut

Raythink introduces the RG630 series handheld infrared gas imager.

• Transform invisible gas leaks into visual images
• Represents the deep application of infrared technology in the field of gas detection

VI. Trend Outlook: Not "Replacement," but "Division of Labor"

From the perspective of technological development, infrared sensors will not completely replace catalytic combustion sensors, but rather form a scenario-based division of labor :

Application scenarios	Recommendation technology	reason
Routine alkane monitoring, oxygen-deficient environment, chemical corrosion environment	Infrared priority	Resistant to poisoning, requires no oxygen, and has a long lifespan.
Special gases such as hydrogen, acetylene, and ammonia	Catalytic combustion/electrochemistry/thermal conductivity	Infrared is not applicable
Portable inspection, personal protective equipment	Infrared + catalytic combustion combination	Balancing versatility and coverage
Low-concentration trace leakage detection	Infrared + Laser	Higher sensitivity

In the foreseeable future, infrared sensors will continue to expand their market share in the monitoring of alkane combustible gases , while catalytic combustion sensors will continue to play a role in the monitoring of specialty gases and cost-sensitive applications . The two technologies will complement each other, forming a complementary and symbiotic technological matrix for gas detection.

VII. Conclusion

From catalytic combustion to infrared sensing, the evolution of gas detection technology reflects the upgrading of industrial safety requirements—no longer satisfied with simply "being able to detect," but pursuing "more reliable, more durable, and more intelligent." Infrared sensors, with their inherent advantages of resistance to poisoning, oxygen-free operation, and long lifespan, are redefining the reliability standards for combustible gas detection.

For users, this technological transformation means:

• Higher initial investment , but lower total lifecycle cost.
• Longer maintenance-free periods , but require establishing new habits for optical cleaning .
• Wider range of applicable scenarios , but the limitations of its gas selectivity still need to be acknowledged.

Technological advancements are never instantaneous, but as safety standards become increasingly stringent, industrial environments become more complex, and maintenance costs become a major concern, infrared sensing technology, with its inherent advantages, will inevitably occupy an increasingly important position in the landscape of gas detection.