Development of a General Purpose Hydrogen Sensor

In air, concentrations of hydrogen exceeding 4% are easily ignitable and highly flammable. In coal mines, hydrogen concentrations in the range 1-200 ppm indicate the level of mine "heat up" (spontaneous combustion of the coal face), while hydrogen concentrations at percentage levels may occur after mine fires, thus increasing the risk of secondary explosion. Accurate monitoring of hydrogen concentrations is thus a necessary concern for the coal industry.

Despite such a pressing need for hydrogen monitoring, no practical sensor exists which is capable of monitoring hydrogen at percentage levels (ie. near the explosive limit) in coal mines. With the help of ACARP funding (and funding from the University of NSW and the Australian Research Council) we established a research program with the aim of developing a sensitive and practical hydrogen sensor to in-situ monitor hydrogen at the percentage levels.

All of our goals have been achieved. We have invented a new method of optoelectronic hydrogen sensing based on the detection of the changes caused by hydrogen on the optical properties of certain materials. We have used this concept to develop a hand held, battery operated prototype hydrogen detector, and have tested several versions of this device. Our device have the following properties:

• excellent signal to noise ratio near the explosive limit (0.1-20% hydrogen),
• no cross-sensitivity to any of the tested gases (N₂, 02, CO, CO₂, CH₄, H2O, Ar, He),
• response time of the sensor element is less than 30 seconds,
• not effected by oxygen depleted environments (unlike catalytic devices).

The necessary steps have been taken (by the University of NSW) to obtain patent protection for our device.