5 Methane gas detection Sensor Types and their working

Introduction : Methane (CH4) is a highly flammable gas widely used in energy, industrial, and domestic applications. While essential, methane leaks pose serious risks including explosions, fire hazards and environmental damage as a potent greenhouse gas. Detecting methane quickly and accurately is therefore critical for ensuring safety, protecting infrastructure, and meeting regulatory standards.

A variety of gas detection technologies are available today, each based on different sensing principles and suited to specific applications. This page explores the 5 most common types of methane gas detection sensors including catalytic bead, infrared NDIR, semiconductor MOS, laser and ultrasonic. We will understand how they work and highlights their advantages and disadvantages.

1. Catalytic Bead Gas Sensor

• Structure : This sensor consists of two heated beads viz. active and reference. Active bead is coated with a catalyst. Reference bead is inactive.
• Working : When methane comes in contact with active bead, it oxidizes and releases heat. As a result of this, resistance of the bead changes. Resistance difference between active and reference beads is measured.
• Advantages : Cheap in cost, Robust, wide detection range
• Disadvantages : oxygen is needed for its operation, susceptible to poisoning by silicons, lead and sulfur.

2. Infrared NDIR Gas Sensor

• Working : It works based on the fact that methane absorbs infrared (IR) light at a specific wavelength (~ 3.3 μm). An IR source emits light; part of which is absorbed by methane gas. The detector installed measures drop in absorption based on methane gas leakage around the pipeline. The absorption of IR light is proportional to the gas concentration.
• Advantages : Long lifetime, immune to poisoning, works without oxygen.
• Disadvantages : More expensive, sensitive to dust/water vapor contaminiation.

3. Semiconductor MOS Gas sensor

• Working : A thin film of tin dioxide (SnO2) changes its resistance when methane molecules react with absorbed oxygen ions on the surface at elevated temperature. In this sensor, resistance drop is used as indication of presence of methane gas.
• Advantages : Low cost, compact in size, fast in response
• Disadvantages : Higher power consumption, cross sensitive to other gases

4. Laser Methane Gas Sensor

• Working : It uses laser tuned to methane’s absorption wavelength. Measures absorption with high precision in ppm or even ppb range.
• Advantages : Very high sensitivity, selective and fast response
• Disadvantages : Expensive, used in specialized applications such as pipeline monitoring, leak detection etc.

5. Ultrasonic Gas Leak Detector

• Working : It detects the sound generated by gas leakage. This is based on the fact that when pressurized gas escapes from a pipe, valve or tank, it produces ultrasonic sound waves with frequencies greater than 20 KHz. These signals are independent of gas type, wind or dispersion.
• Advantages : Fast detection (within 1sec), works in windy conditions, cover large areas
• Disadvantages : May miss very small leaks, higher cost compared to MOS and catalytic type, sensitive to high background noise if not filtered properly.

6. Electrochemical sensor

• Working : Methane reacts at electrode which produces current proportional to gas concentration. It works like small fuel cell with electrolyte and electrodes.
• Advantages : Good sensitivty, Selective if designed properly
• Disadvantages : Limited life span (~1-3 years), can be affected by humidity & temperature.

Conclusion: While catalytic and MOS sensors offer cost-effective solutions for general monitoring, infrared and laser based systems provide higher precision and durability in demanding environments. Electrochemical sensors, on the other hand, are valued for their selectivity and sensitivity in specific applications. Choosing the right sensor depends on factors like required sensitivity, environmental conditions, cost and maintenance needs.