HEV working?

[RollieVerde]

Originally Posted by S52

I wore my 16710 in an altitude chamber ride during my Air Force training where we simulated a rapid decompression... from sea level to about 25,000 feet in a couple seconds... absolutely zero effect on my watch.

I've also been in a simulation in an altitude chamber, where we got to experience hypoxia and decompression amongst other things. It wasn't done as rapidly as the scenario I gave above, though. And as I recall we all took off watches before we entered the chamber. I think. it was a long time ago. If memory serves there was the possibility of the crystals fogging up, not necessarily popping off. In fact, the chamber got foggy when decompression took place.

And vman, the valve would respond to the pressure differential, regardless of the type of gas. Helium is a problem because the molecules are so tiny they can infiltrate the case as they're even smaller than water molecules, so the case can be waterproof yet He can still get inside. Some manufacturers state that their cases are so tight even helium can't get in. I am skeptical, because (I've heard) helium doesn't get past seals; it gets throughout the stainless steel case itself. Then as the pressure rises they can't get out the same way they got in, or at least not as quickly. It's why when you use lift bags underwater you have to be careful as you come to the survive they don't run away from you as the air inside them expands. Most purpose built lift bags have purge valves so you can purge off the excess as you ascend.

Very interesting topic, this. A lot is involved.