Numerous advancements in gas detection technologies have been accomplished in recent years, particularly for the detection of hydrocarbon gases such as methane (CH4) and carbon dioxide (CO2).
The most recent, innovative technologies to detect these type of gases utilizes diodes that emit light (LEDs) along with infrared (IR) or non-dispersive infrared (NDIR) detection to give unrivaled trustworthiness and efficacy,1 where devices can also last for up to ten years.2
These devices are the most compatible for use in industrial and business applications in order to protect the health and safety of workers.
Early and Reliable Detection
Methane and carbon dioxide gases, to name a few, can lead to various risks when present in industrial sites and are commonly by-products of numerous chemical operations.
Two main risks can arise when hydrocarbon gases are present in industrial sites; the first of which is direct exposure. CO2 is defined as a ‘substance hazardous to health’ and if a worker comes into contact with the gas, there can be a variety of symptoms, from the minor such as headaches and confusion, through to fatal asphyxiation in more serious events.3
Methane and carbon dioxide do not only pose threats to the health and safety of workers; methane in particular is very flammable,4 and where found in higher concentrations, there can be a risk of the gas causing an explosion.
As such, it is incredibly important in industrial applications to be able to detect the presence of these gases to eliminate the risks detailed above. Further to this, it is essential to make sure the detection device is reliable, and that it can capture the presence of gases early in order to resolve the risk before it turns into a health and safety incident.
In the past, canary birds were utilized in this manner as an aid for mine-workers, as their sensitivity to airborne toxins, and their high need for oxygen, made it easier for them to suffocate. If canary birds had died or were showing signs of distress, this signaled to the workers that harmful gases were present.5
From Birds to Beads to LEDs
Catalytic bead technology was one of the next technologies to replace the use of canary birds as they were more trustworthy and humane. Within the catalytic bead, or Pellistor-type sensor, there are two platinum coils adjoined in a Wheatstone bridge type of circuit.
One of the wires is coated in active beads or a catalyst, whereas the other wire is coated with no catalyst and therefore acts as compensation within the circuit. When utilizing an electrical current, the beads are heated to great temperatures, and when a molecule from the target gas meets and reacts with an active bead, there is a resistance change, then a voltage change, that shows that the target gas is present.6
While instruments utilizing catalytic bead technology have been used in many applications, there are disadvantages of using these devices. While the devices hold a longer lifespan than using a canary bird, the catalytic beads within the sensors do degrade continually.
The degradation is due to the chemical reaction that provides the detection of the target gas, because the process also leaves the gas attached to the catalytic substrate, making it unable to detect any further gas molecules.7
This inherent effect within the device makes the sensor less sensitive over time, leading to a complete coil burnout in the end. Furthermore, continual checks and calibrations are necessary to make sure the device is accurately detecting the target gas, which only gets more intensive as the device is subjected to more gas in time.
Catalytic beads can also be poisoned where other chemical compounds are present, not only the flammable gases found in industry applications. This is specifically an issue in gas and oil applications, as the beads are very sensitive to poisoning by chemicals that are used frequently in these industries, such as silicone vapors, a variety of derivatives of hydrocarbons, hydrogen sulfide, and much more.7
Like the continual degradation caused by the target gases, this poisoning also reduces the lifetime of the sensor, increases the requirement for frequent checks and will ultimately render the detector useless.
If the devices are not monitored closely enough, this results in potentially hazardous situations to develop unnoticed. Other chemicals, like the flame arrestors that may be used in areas at high fire risk, have similar detrimental effects on the sensitivity of detectors.
Aside from the disadvantages mentioned above, catalytic bead devices also require a high power draw when the coils are heated, and as such, they are not able to be used in all applications.
It can often be beneficial to place gas sensors in environments that have a low amount of oxygen, or even in inert spaces with no air, however, these conditions can reduce the sensitivity of these detectors, where inert areas make them fully unable to detect gas.8
Optical Alternatives with MIPEX
In light of the disadvantages of past technologies, there are now alternative solutions for trustworthy flammable gas detection that also provide longevity for the user. MIPEX’s recently developed LED-based gas sensors provide solutions for the majority of the issues described around catalytic bead technology.9
These devices utilize an LED as a continual infrared source alongside an appropriate detector. When the CO2 or hydrocarbon gas travels through the area between the source and the detector, they absorb the radiation emitted by the infrared at wavelengths that can be characterized.
As the wavelengths can be characterized and the detector calibrated to these wavelengths, the absorption of the radiation can be used to monitor the concentration of gas.10 As these devices do not rely on chemical reactions, they are not subjected to the same level of wear-and-tear over time as catalytic bead devices are.
The devices only need calibration around every 30 months, and can last up to ten years.11 Suitable to be used in even the harshest of conditions due to their resistance against moisture and high operational temperatures, sensors such as the MIPEX-02 operate with minimal variation in sensitivity and baseline measurements over time.12
Each MIPEX miniature sensor comes with extremely small power draws. The MIPEX-04, in particular, is 1,000 times more efficient when using energy than any other methane detector on the market.13
A further benefit of using infrared based devices instead of catalytic bead sensors is that they are able to operate in conditions where 100% methane is present. They also have an exceptional level of sensitivity from 1% LEL for methane.11
The reduced power consumption of the MIPEX LED devices is not just energy-saving, it also means that they are suitable for wireless or portable devices and can be incorporated as part of connected gas safety strategies.14
Due to the robust and efficient response of the MIPEX LED-based sensors to even the lowest concentrations of gas, and its small power draw, the MIPEX LED-based devices offer a beneficial and easy to use solution instead of traditional catalytic beads to make sure the highest safety standards are upheld in industrial applications.
References and Further Reading
- X. Liu, S. Cheng, H. Liu, S. Hu, D. Zhang and H. Ning, Sensors, 2012, 12, 9635–9665
- MIPEX TECNOLOGY, https://mipex-tech.com/tech/optical-sensors-for-methane-and-hydrocarbon-detection-with-ultra-low-power-consumption/, (accessed February 2019)
- HSE on CO2, http://www.hse.gov.uk/carboncapture/carbondioxide.htm, (accessed February 2019)
- Gas Flammability, http://trimeric.com/assets/flammability-of-mixtures-of-co2-and-hydrocarbons.pdf, (accessed February 2019)
- History of Gas Detection, https://www.ehstoday.com/industrial_hygiene/instrumentation/gas-detection-ages-0501, (accessed February 2019)
- Z. Yunusa, M. N. Hamidon, A. Kaiser and Z. Awang, Sensors and Transducers, 2014, 168, 61–75.
- Sensor Lifetimes, http://www.hazardexonthenet.net/article/128977/Understanding-gas-sensor-lifespan.aspx, (accessed February 2019)
- Oxygen and Catalytic Beads, https://ohsonline.com/articles/2018/08/01/why-do-you-need-vol-oxygen.aspx, (accessed February 2019)
- MIPEX LED Breakthrough, https://www.envirotech-online.com/news/gas-detection/8/mipex-technology/breakthrough-in-low-power-ndir-gas-sensor-technology/42125, (accessed February 2019)
- T. V. Dinh, I. Y. Choi, Y. S. Son and J. C. Kim, Sensors Actuators, B Chem., 2016, 231, 529–538
- MIPEX Catalog, https://mipex-tech.com/catalog/, (accessed February 2019)
- MIPEX-02, https://mipex-tech.com/catalog/mipex-02/, (accessed February 2019)
- MIPEX-04, https://mipex-tech.com/catalog/mipex-04/, (accessed February 2019)
- Connected Gas Safety, https://www.blacklinesafety.com/g7-connected-safety-moves-beyond-gas-detection/, (accessed February 2019)
This information has been sourced, reviewed and adapted from materials provided by MIPEX.
For more information on this source, please visit MIPEX.