HYDROGEN AS TRACER GAS FOR LEAK DETECTION
Sensistor Technologies, Muehlheim, Germany
When it comes to leak detection, Helium has been the most common tracer gas of all. There are, however, a
number of limitations preventing the use of Helium tracer gas in many industrial applications. Hydrogen
molecules weights only half of a Helium atom and has a much higher molecular velocity, hence Hydrogen
spreads quickly inside test objects, and dissipates very much quicker than Helium. Besides the low cost,
these properties make Hydrogen a very attractive alternative to Helium for leak detection.
There are essentially only two reasons why Hydrogen hasnít become a more common tracer gas than
Helium long ago; a) the perception that Hydrogen would be too dangerous and b) the availability of suitable
The flammability problem is easily overcome by using a readily available standard mix of 5% Hydrogen in
nitrogen, which is classified as non-flammable.
The other obstacle was solved by the advent of a new type of Hydrogen detectors, based on microelectronic
Hydrogen sensors. These detectors have a high sensitivity and high selectivity to Hydrogen. At the same
time they are robust and cost-effective for industrial use, allowing leaks down to 5x10-7 atm cc/s to be
detected using the 5% Hydrogen mix. The use of Hydrogen as a tracer gas is now increasing rapidly in a
number of industries, such as in automotive, chemical, power generation, aerospace and even telecom.