I know H2 is not a flammable liquid, but this shows how little it takes to set off a vapor or gas cloud.
Flammability range is 4% to 74%
Hydrogen has a VERY low ignition energy—as little as 0.017 millijoules (mJ) at 30% concentration, in contrast to 0.25 millijoules for other hydrocarbon fuels.
Walking across the carpet and getting shocked is ~20 mJ!!!!!!
ONLY 5% Oxygen is needed to have an explosive H2 atm!