Conversion of helium leak rate at laminar flow to leak rates of other gases
As can be seen from this table, the difference of leak rate of air is only 7.7% than helium, smaller than the accuracy of a helium-leakdetector. If we consider a leaktest with a helium/air mixture under laminar flow conditions, then the measured helium leakrate can be regarded as the same as the air leakrate. For example, in a test carried out with a 10% Helium / 90% Air mixture, the measured Helium leakrate is 10% of the total leakrate, which from the above table is:
(0.9 x 1.077) + (0.1 x 1) = 1.069
This shows an error of 6.9% taking the viscosity of air a 1.