It is expected that the hydrogen society as new fuel will be around in the near future. Many researchers have studied and developed feul cells using hydrogen which is not easy to deal with.
The most important thing is to ensure safety among any others.

Hydrogen is dangeous material because it detonates when included more than 4% in the atmosphere. Therefore, we have to study a fast response hydrogen sensor that can detect the hydrogen leakage of 4% or less as well as the development of hydrogen fuel.

Detection time of milliseconds hydrogen sensor has been developed. It uses a unique property of ultrasonic that the sound velocity in hydrogen is about 4 times faster than that in the air. Therefore, it is possible to measure hydrogen concentration by measuring the sound velocity variation when hydrogen is mixed in the air after the hydrogen leakage.