This tendency may create an incredibly hazardous working environment if a user believes that the sensor is operational when, actually, it’s failing to alert the user to the presence of dangerous gases. Even when the sensor has been poisoned, it will appear to be working normally.Poisoning can occur even when the sensor encounters common chemicals such as silicones, chlorine, lead, phosphates, and acidic gases. Once these sensors come into contact with high concentrations of flammable and combustible gases, the catalyst is burned up, and the sensor is deactivated. Unfortunately, similar to NDIR, pellistor/catalytic bead sensors have some severe limitations: The sensor provides a reading that corresponds to the concentration of the hazardous gases present in the vicinity. The presence of flammable gas causes the catalytic bead to heat more than the inert bead. A heater within the sensor raises the temperature and measures the difference in temperature between the two beads. These sensors contain two small beads, one of which is inert while the other is coated in a chemical catalyst. And they can detect hydrogen, methane, butane, propane, and carbon monoxide, as well as other gases. Among the advantages of Pellistor/catalytic bead gas sensors are that they’re relatively inexpensive and sensitive to nearly all flammable gases. 2): They have been used for gas-leak detection for nearly a century. Pellistor/catalytic bead sensors pre-date NDIR technology (Fig. Using Pellistor/Catalytic Bead Sensors to Detect Gas Leaks NDIR’s inability to detect hydrogen can lead to unsafe working environments and the sensitivity of the sensors make them ineffective in many environments. NDIR uses proprietary technology, making it an expensive option.ĭespite their widespread use in detecting gas leaks for the last several decades, the limitations of NDIR sensors have left the market desiring more reliability, which new technologies have addressed.Humidity, fog, and ambient infrared light may seep into the open chamber and cause interference.NDIR sensors can be tuned to accurately detect only a single gas, making them ineffective in mixed-gas environments.NDIR sensors are very sensitive to temperature and humidity changes, and moving through even moderate temperature transitions can freeze their output.Hydrogen is an incredibly dangerous gas in the mining and petroleum industries, and NDIR's inability to detect it can mean that a potentially hazardous work environment goes undetected. NDIR is unable to detect hydrogen as this gas doesn’t absorb infrared light.The sensor determines the difference between these two transmitted light intensities to develop a gas concentration.Īnd while NDIR was the height of gas-detection technology 40 years ago-and for several decades after-this technology does have some notable limitations: ![]() Infrared light is absorbed as a particular gas passes through an active filter, while infrared light that doesn’t interact with the target gas goes through a reference filter. These sensors consist of an infrared source, a detector, an optical filter, a gas cell, and signal-processing mechanisms. This technology works by using infrared light to detect different wavelengths absorbed by gases. Non-dispersive infrared sensors, or NDIR, were introduced in the 1960s and have been widely used for gas-leak detection since that time (Fig. After NDIR was introduced in the 1960s, the gas-detection industry experienced a prolonged era with little innovation, until recently. Pellistor/catalytic (CAT) bead sensors and non-dispersive infrared (NDIR) sensors have been the primary gas-detection methods for many decades. Results of testing among the three sensor types.How MPS sensors overcome the issues with pellistor and NDIR sensors.The benefits and disadvantages of NDIR sensors.The benefits and disadvantages of pellistor sensors.
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