In today’s increasingly complex industrial production and daily life, safety hazards caused by combustible gas leaks have become a global concern. Combustible gas sensors, as core tools for preventing explosions and fires, help users respond to risks in a timely manner by monitoring gas concentration in real time. With years of technical accumulation, Nexisense has developed a range of sensor products suitable for different scenarios. This article systematically reviews the main types of combustible gas sensors, including their working principles, characteristics, and practical applications, helping readers gain a deeper understanding and choose appropriate solutions. With this knowledge, you can better evaluate sensor performance and enhance safety in real deployments.

Catalytic Combustion Sensors

Catalytic combustion sensors are among the most widely used technologies in industrial fields. Their design is based on the clever use of gas oxidation reactions. The core component inside the sensor is a platinum wire coil coated with a noble metal catalyst (such as platinum or palladium). When combustible gases such as methane or propane enter the sensor, they undergo flameless combustion with oxygen in the air on the catalyst surface. This combustion releases heat, causing the platinum wire temperature to rise and its resistance to change. By measuring this resistance difference through a Wheatstone bridge circuit, the sensor outputs a signal proportional to the gas concentration, usually expressed as %LEL (percentage of the lower explosive limit).

The advantages of this type of sensor include excellent linear output, high accuracy, and fast response time, typically detecting changes within a few seconds. It has high sensitivity to common hydrocarbon gases and reliability proven by long-term industrial use. However, limitations should be noted: it cannot operate properly in oxygen-deficient environments because combustion depends on oxygen; in addition, exposure to contaminants such as silicon compounds or sulfides may poison the catalyst and reduce sensitivity. Regular calibration and maintenance are key to ensuring performance.

Nexisense catalytic combustion sensors perform outstandingly in petrochemical plants, natural gas pipelines, and coal mine methane monitoring. For example, in chemical plant leak detection systems, they can monitor concentrations in real time and trigger automatic ventilation or valve shutoff, significantly reducing accident risks. Products such as the ZR07 bead-type and ZC25 series optimize catalyst formulations, improve anti-poisoning capability, and offer service lives of several years.

Infrared Sensors

Infrared sensors represent a modern direction in gas detection technology, mainly based on the NDIR (Non-Dispersive Infrared) principle. Combustible gas molecules have unique absorption characteristics for specific infrared wavelengths; for example, methane strongly absorbs infrared light around 3.3 micrometers. The sensor emits an infrared beam and measures the attenuation of light after it passes through the gas, thereby calculating the concentration. This method does not involve chemical reactions and is therefore not affected by oxygen concentration.

Its core advantages include an extremely long service life (often exceeding 10 years), strong resistance to poisoning, and high selectivity. Even in high-humidity or corrosive environments, it can operate stably with minimal interference. The main disadvantage is higher cost, due to precision optical components and signal processing circuits. However, with technological advances, this gap is gradually narrowing.

In practical applications, infrared sensors are particularly suitable for high-risk or oxygen-deficient scenarios, such as underground utility tunnels, offshore oil platforms, or sealed storage tanks. Nexisense TX721 series infrared sensors support multi-gas detection and integrate digital interfaces, making them easy to connect with IoT systems. In a typical case, they were used in natural gas transmission pipeline monitoring, helping operators remotely track trace leaks and avoid potential explosions.

Semiconductor Sensors

Semiconductor sensors occupy a place in the civilian market due to their simple and efficient design. Their principle relies on changes in conductivity of metal oxide semiconductor materials (such as tin oxide) when heated. When combustible gases contact the heated semiconductor surface, adsorption reactions occur, causing the material’s conductivity to increase sharply. By monitoring this change through circuitry, the sensor outputs a corresponding signal.

The advantages are clear: compact size, low cost, and high sensitivity, making them suitable for mass production and portable devices. They have short response times and can quickly capture gas fluctuations. However, poor selectivity is their main drawback—they are easily affected by temperature, humidity, or other gases, resulting in higher false alarm rates. In design, filter layers are often added to mitigate this issue.

Nexisense semiconductor sensors are mainly aimed at household gas alarms and portable detectors, such as the MQ-K series products. These sensors are easy to integrate, have low power consumption, and are suitable for daily scenarios like kitchens or garages. In smart home systems, they can link with apps to push real-time alerts, helping users prevent gas leaks.

Electrochemical Sensors

Electrochemical sensors are mainly used for toxic gas detection, but they perform excellently for certain gases that are both combustible and toxic, such as carbon monoxide (CO). Their principle is based on electrochemical reactions: when a voltage is applied between electrodes, the target gas undergoes oxidation or reduction in the electrolyte, generating an electrical current. The magnitude of this current is directly proportional to the gas concentration.

Advantages include high accuracy, good selectivity, and low power consumption, especially suitable for low-concentration detection. The sensor has good linear response and is easy to calibrate. Disadvantages include relatively short service life (typically 2–3 years) and greater sensitivity to temperature, requiring compensation circuits.

Nexisense electrochemical CO sensors are widely used in household alarms and industrial protection. For example, in boiler rooms or garages, they can accurately monitor CO levels and prevent poisoning accidents. Product designs emphasize stability and support 4–20 mA output for easy integration into control systems.

Comparison and Selection Guide for Different Sensor Types

After understanding the differences among various sensors, selection should be based on specific needs. Catalytic combustion sensors are suitable for industrial environments with high accuracy requirements, provided sufficient oxygen is available; infrared sensors are preferred in oxygen-deficient or high-reliability scenarios; semiconductor sensors are economical and suitable for civilian use; electrochemical sensors target specific toxic combustible gases.

For industrial safety monitoring, catalytic combustion or infrared sensors are recommended due to complete explosion-proof certifications and high reliability, capable of handling complex gas mixtures. For high-risk or oxygen-deficient environments, infrared sensors are the first choice, as their maintenance-free characteristics reduce long-term costs. Household gas alarms are suitable for semiconductor sensors, meeting basic needs with budget-friendly solutions. Carbon monoxide detection should use electrochemical sensors to ensure targeted accuracy.

Nexisense recommends users evaluate environmental factors such as temperature range, gas type, and budget. Practical cases show that combining multiple sensor types (such as catalytic and infrared hybrid systems) can improve overall performance. In the future, with advances in MEMS technology, these sensors will become more miniaturized and intelligent, supporting wireless transmission and AI analysis.

Frequently Asked Questions (FAQ)

1. What is %LEL? %LEL represents the percentage of the lower explosive limit, referring to the minimum gas concentration in air that can cause an explosion. Sensors commonly use this unit to assess risk.

2. How do catalytic combustion sensors avoid poisoning? By optimizing catalyst formulations and adding protective filter layers, Nexisense products improve resistance to silicon compounds and sulfides. Regular cleaning can also extend service life.

3. Which gases are suitable for infrared sensors? Mainly methane, propane, carbon dioxide, and other hydrocarbons and greenhouse gases, offering strong selectivity and no dependence on oxygen.

4. Why are semiconductor sensors easily affected by interference? Their materials are sensitive to environmental conditions; for example, humidity changes can cause conductivity fluctuations, requiring compensation mechanisms in design.

5. What is the service life of electrochemical sensors? Typically 2–3 years, depending on the operating environment. Nexisense emphasizes regular replacement to maintain accuracy.

6. How are combustible gas sensors calibrated? Standard gas mixtures are introduced into the sensor, and the output is adjusted to match known concentrations. Calibration is recommended every 6–12 months.

7. Which sensor should be used in oxygen-deficient environments? Infrared sensors are the best choice because they do not rely on oxygen participation and are suitable for sealed or underground spaces.

8. Which type is commonly used in household alarms? Semiconductor sensors, due to low cost and small size, meeting daily gas monitoring needs.

9. Do Nexisense sensors support system integration? Yes, they support interfaces such as 4–20 mA and RS485, making them easy to integrate into PLC or IoT systems.

10. What are future trends? Development toward miniaturization, multi-gas detection, and intelligent analysis, combined with AI to improve predictive accuracy.

Conclusion

Combustible gas sensors come in various types, each with its own strengths—from the reliable industrial applications of catalytic combustion sensors, to the maintenance-free advantages of infrared sensors, and the targeted solutions of semiconductor and electrochemical sensors—all safeguarding safety. Nexisense is committed to providing highly adaptable products to help users address diverse challenges. Through this detailed explanation, you can confidently choose appropriate technologies and achieve efficient monitoring. In an era where safety comes first, investing in high-quality sensors is not only risk prevention, but also a key to sustainable development.