Semiconductor Gas Sensors Making Innovations in Safety Applications

Semiconductor gas sensors have excellent sensitivity to gases that allows them to detect extremely small amounts of gas, as little as ppm. Therefore, they can find gas leaks at early stages, which contributes greatly to the mitigation of risks of gas leak incidents in plants. However, monitoring at %LFL levels using other sensor technologies is more common. Why aren’t semiconductor sensors used even if they can detect at ppm levels? Because it is known as that environmental conditions can significantly affect their performance. Semiconductor sensors are described by IEC60079-29-2 as:

1. Not selective;

2. Vulnerable to environment changes including humidity/temperature/surrounding gases;

3. Having a wide variation in sensitivity between sensors of the same kind; and

4. More susceptible to poisoning compared with catalytic sensors.

However, in the recent years, semiconductor sensors have been significantly evolving. The weak points above have been reduced to problem-free levels. For example, there are now semiconductor sensors with selectivity to one particular gas type. The effects of temperature, humidity and poisoning have been minimized by improved sensor elements and new process technologies. Furthermore, their biggest feature—the capability to detect low concentrations of gas—has been improved, too: It is now possible to detect as low as 0-5 ppm of gas.

In Japan, semiconductor sensors are used in many places ranging from industrial to residential, like in plants and households. Specifically, portable pump-type gas leak detectors for gas piping/equipment maintenance can correctly identify gas leaks caused by worn-out equipment by making efficient use of sensors’ ability to detect small concentrations of gas. Most plants in Japan will soon exceed 50 years of operation. Semiconductor sensors are very useful when mitigating gas-related incidents in aging facilities.

Requirements for detectors with 20%LFL FS or lower have been added to the international standard for flammable gas detectors, IEC60079-29-1:2016. This move indicates that the importance of detection at low levels is recognized worldwide.

The innovations in semiconductor sensors make them useful not only in gas leak monitoring but also in quality control or environment monitoring. For example, it is now possible to digitally control food odors, perform equipment performance retention, and even working environments like printed factories, which were previously difficult to control. Furthermore, combining this with other sensor technologies enables predictive maintenance. Semiconductor sensors are a core technology that brings innovation in safety monitoring, and has a lot of potential in providing solutions to new challenges.

Keywords: Plant, Sensor technology, Gas detection, Safety