Hydrogen is actually the lightest element in the universe. The gas is 15 times lighter than air, and its viscosity is only half that of air and helium. Hydrogen spreads so easy throughout the test object, penetrates leaks more readily and it vents away significantly easier than any other trace gas. If you are concerned about background build-up, hydrogen trace gas is the gas to use. It is also the most inexpensive trace gas you can get.
Hydrogen gas has a number of unique properties which make it an excellent trace gas for use in leak detection and testing:
• The lightest of all molecules
• Lowest viscosity of all gases (easy to fill, evacuate and dissipate)
• Low background (0.5 ppm)
• Environmentally friendly and renewable - ISO 14001
• Inexpensive
• Non toxic - non corrosive
• Non flammable (when diluted 5% in Nitrogen) - ISO 10156
Pure hydrogen should never be used as trace gas. We recommend a standard industrial grade mix of 5% hydrogen in nitrogen. This mix is inexpensive, non- flammable, easily available, and still holds the important features needed for using hydrogen as trace gas.
Hydrogen is actually the lightest element in the universe. The gas is 15 times lighter than air, and its viscosity is only half that of air and helium. Hydrogen spreads so easy throughout the test object, penetrates leaks more readily and it vents away significantly easier than any other trace gas. If you are concerned about background build-up, hydrogen trace gas is the gas to use. It is also the most inexpensive trace gas you can get. 
