Originally Posted By: djb
I don't think that this table of seal leak rates applies to gas diffusion through rubber.
The hydrogen number is a good example -- it's only 2x that of nitrogen. Hydrogen is very good at diffusion through "impermeable" barriers, sometimes many orders of faster than other gases.
I would agree. Compare a helium filled balloon to one filled with air, and see which runs out first. The chart shows them as very close, but in a balloon, the helium filled one will deflate much more rapidly.
It appears this company makes metal seals. Ordinarily, helium's diffusion rate (being monatomic) is about three times that of normal air. Hydrogen will penetrate even faster.