Methane gas is an odorless, colorless gas that can become highly flammable or combustible at what is known as 100 %LEL concentrations. For many manufacturers around the world, detecting hazardous levels of methane gas with a methane gas sensor is an extremely important daily operation.
For nearly a hundred years, coal, oil, and gas industries have been using sensors to detect flammable compounds in the atmosphere. As time goes on, new technology has increased the sophistication of flammable gas sensors. Currently, two primary technologies – pellistor and NDIR – for methane gas sensing are available, while NevadaNano’s new MPS Flammable Gas sensor brings new advances to improve safety, reliability, and cost of ownership.
Pellistor sensors, which utilize catalytic bead sensing, burn small amounts of gas to produce heat proportional to the presence of flammable gas which is measured by a resistance element. These sensors are very common and react to most combustible gases, including methane.
Unfortunately, catalytic bead sensors aren’t without their drawbacks.
Pellistor sensors are only accurate for the gas the sensor is calibrated or adjusted to with a k-factor. In situations where it’s not known whether the gas present will be methane or another combustible gas, the sensor will provide unreliable readings if the combustible gas is other than methane.
One of the major disadvantages of pellistor sensors is their susceptibility to “poisoning”. Over time, the catalytic elements in pellistor sensors can be poisoned by compounds such as silicon and sulfur, which reduces their lifespan and accuracy. The more highly concentrated the compound or gas, the quicker the sensor burns out.
Lastly, catalytic elements lose effectiveness with exposure to common atmospheric chemicals and require frequent characterization to ensure accurate, safe measurement of methane concentrations.
Non-Dispersive Infrared Sensors are the second type of methane gas sensor in widespread use. NDIR sensors use infrared lamps to measure the concentration of methane and some other potentially combustible gases.
Unlike pellistor sensors, NDIR sensors aren’t prone to poisoning, enabling longer calibration intervals. In addition, NDIR sensors have high selectivity and can accurately measure methane concentrations in a mixed gas background.
While NDIR sensors offer some advantages over pellistor sensors, they do have some downfalls of their own.
NDIR sensors measure gas through the absorbance of infrared light at unique wavelengths.
But some gases, like hydrogen, do not absorb infrared light and thus can’t be measured. In addition, NDIR sensors are typically finely tuned to accurately detect only methane. In an environment where multiple hydrocarbons may be released, NDIR sensors are likely to provide false readings.
Mixed compounds are also a challenge for NDIR sensors, making NDIR sensors not suitable for environments with multiple gases.
NevadaNano’s MPS Flammable Gas Sensor brings new advances to hazardous and combustible gas safety. The MPS Flammable Gas Sensor combines the best features of both catalytic bead sensors and NDIR sensors.