  Gas leakage is a serious hazard in a variety of sectors, including
industrial, domestic, and gas-powered vehicles. The installation of gas leak
detection systems has emerged as a critical preventative measure to solve this
problem. Traditional gas sensors, such as electrochemical, infrared point, and
Metal Oxide Semiconductor sensors, have been widely used for gas leak
detection. However, these sensors have limitations in terms of their adaptation
to various gases, as well as their high cost and difficulties in scaling. In
this paper, a novel non-contact gas detection technique based on a 40 kHz
ultrasonic signal is described. The proposed approach employs the reflections
of the emitted ultrasonic wave to detect the gas leaks and also able to
identify the exact gas in real-time. To confirm the method's effectiveness,
trials were carried out using Hydrogen, Helium, Argon, and Butane gas. The
system identified gas flow breaches in 0.01 seconds, whereas the gas
identification procedure took 0.8 seconds. An interesting extension of the
proposed approach is real-time visualisation of gas flow employing an array of
transducers.
