Infrared (IR) gas sensors and non-dispersive infrared (NDIR) sensors have been used for gas detection for many decades. These tools come with many benefits, although there are also some dangers that users should be aware of when using infrared gas sensors.
Benefits of Infrared Gas Sensors
Infrared gas sensors were introduced as a way to account for some of the drawbacks of catalytic sensors. Initially developed for use in the mining industry, catalytic sensors have been used for over a century. Catalytic sensors measured a temperature difference between two beads – an inert one and one coated in a chemical catalyst. The temperature differential information could identify the gas concentrations of the hazardous gas being measured. Unfortunately, these sensors have limitations. They:
- Are prone to poisoning
- Require high amounts of power
- Have a limited life expectancy
- Can deliver faulty readings if calibrated to a single target gas
- Do not function in low-oxygen environments
Infrared sensors were developed to address these drawbacks. These sensors use infrared light to gauge the different wavelengths of hazardous gases. Properties of some gases absorb light in certain wavelength ranges or bands. However, that is not the case for the main components of air, such as nitrogen, oxygen, and argon.
Infrared light is absorbed as a target gas passes through an active filter. The infrared light that does not interact with the target gas molecules goes through a reference filter.
Essentially, two infrared beams of different wavelengths are guided into the measuring chamber to hit two detectors. These are the measuring and reference detectors. If the absorption of a gas weakens the measuring beam, the reduced intensity corresponds to the gas concentration. A signal processing mechanism determines the difference between the light intensities to report the gas concentration to the user.
Gases that can be detected by infrared include all heteroatomic gases such as carbon dioxide and hydrocarbon compounds. They are frequently used for sensing carbon dioxide, carbon monoxide, and methane and can do so reliably in many conditions. Additionally, unlike catalytic gas sensors, they are not susceptible to poisoning. They can detect combustible gases in low-oxygen environments. And they require less power to operate.
At the time of their introduction, infrared gas sensors represented a giant leap forward in technology. And they addressed many – but not all – of the key disadvantages of using catalytic gas sensors. Unfortunately, infrared gas sensors have many limitations, too. Some of which can be dangerous to the user if they are not aware of using this type of gas sensing technology.
The Dangers of Infrared Gas Sensors
Non-dispersive infrared sensors have many drawbacks, including the following:
- Hydrogen does not absorb infrared light. These sensors cannot detect hydrogen. This limitation is substantial because hydrogen is ubiquitous in the mining and petroleum processing industries. Allowing hydrogen to be undetected can present extremely hazardous working conditions. Workers may be entering an area where the air quality is unsustainable for human life without even knowing it. Furthermore, exposure to even low concentrations can cause physical symptoms such as nausea, headaches, tremors, and delirium.
- In addition to the failure to detect hydrogen, infrared gas sensors do not work well when multiple hydrocarbon-based gases are present. IR gas sensors are gas-specific. Each detectible gas has its unique gas curve and temperature compensation response. These gas detectors can provide false readings in this type of setting, resulting in unsafe working conditions.
- Infrared gas sensors are also unable to provide adequate environmental and temperature compensation. When moving across conditions with even moderate changes in temperature or humidity, the sensor’s signal processing function may freeze any output reading.
- These sensors also perform poorly in extreme environments. Humidity, fog, and ambient infrared radiation can impact their process functions and reduce their reliability.
- The IR sensor can be limited by the adsorption characteristics of the target gas and the bandwidth of the filter in the sensor. Many combustible gases are undetectable by low-power infrared LEL gas sensors. Examples of non-detectable gases include acetylene, acrylonitrile, aniline, and carbon disulfide.
The theme across many of these drawbacks is that infrared gas sensors can be unreliable across many different conditions. And any inconsistent reading can result in exposure to hazardous or deadly gases. That is a mistake that most companies cannot afford to make. It can result in tremendous property and financial losses. Worse yet, it can jeopardize employees’ lives in the vicinity if an explosion or fire were to occur.
Additionally, there are other limitations with this type of gas sensing technology. Due to their design, they require frequent calibration. And since they are proprietary technology, they tend to be very costly. The combination of high up-front costs and frequent calibration means they can be expensive to use over their lifetime.
Overcoming the Limitations of Infrared Gas Sensors
The reality is that infrared sensors and non-dispersive infrared sensors work well for some applications. But under many circumstances, these sensors have extreme limitations. Unfortunately, these limitations can result in unsafe conditions for anyone in the vicinity.
Combustible and hazardous gas detection shouldn’t be uncertain. It’s simply too risky to rely on methods that fall short of delivering an accurate output reading every time they are used. Fortunately, recent technological advances in gas detection have provided a new method. The Molecular Property Spectrometer™(MPS™) addresses the limitations of both infrared and catalytic gas sensors.
The MPS sensors remain reliable and accurate across nearly all environmental conditions. They provide for temperature compensations and are not impacted by pressure and humidity changes. They also require no calibration and are impervious to poisoning.
Due to these benefits, the MPS sensors often have a lower total cost of ownership than alternative gas sensing technologies. And they can detect over a dozen gases simultaneously, including hydrogen. This sensor overcomes the dangers of using infrared gas sensors to keep your workplace and employees safe. And there is nothing more important than that goal.