INFICON Sensistor ISH2000 Hydrogen Leak Detector - Manual (Page 10)

Sensistor ISH2000 Technical Reference Manual (TRM) EN- 10
A 600
A 401 About Hydrogen
When pure hydrogen gas is released in air its flammability range spans from 4%
to 75% of hydrogen in air. Below 4% there is insufficient chemical energy avail-
able for a flame to occur. Above 75% hydrogen there is not enough oxygen left
to support a flame. When, for example, a mixture of less than 5.5 % hydrogen
in nitrogen mixes with air there is not sufficient energy to support a flame, irre-
spective of the ratio of air-to-gas. When a mixture of more than 5.5 % hydro-
gen in nitrogen is released into air there is a region of ratios of air-to-gas where
the mixture is flammable. When, for example, a mixture of 10% hydrogen in
nitrogen mixes with air there is still very little energy available. Only in excep-
tional circumstances can a flame be self-supporting. However, such mixtures
cannot detonate.
Hydrogen can be stored and transported as either a gas a cryogenic liquid.
The tracer gas is standard welding gas of industry quality, easy to obtain at low
cost. The generic name is Forming Gas.