Their new campaign says the membrane is used as a heat exchange for the lo2 (phase change). Im guessing the pump or whatever is for metering, but have no idea. It's possible to use an orifice if you have the heat exchange rate approximately correct.
The volume required is not going to be a constant. It will vary between individuals and depending in activity.
True, if they have no metering the dive time would go way down and they would have a problem. However, they've said there s a pump in the device, I think it's for metering but don't know. Also their "demo" videos gives the impression of metering.
The sites I was reading, if i'm understating them correctly, say you can breath 100% o2 at sea level (1.0 ppo2) for 12-16 hours before toxic effects start. Apparently diving standard is 1.4 ppo2 for regular usage and 1.6 for special or emergency usage. The allowable time decreases.
It's true that under very specialized circunstances you can get away with breathing 100% O2 for short periods but it requires pretty tightly controlled parameters for pressure, etc to avoid toxicity. (I added that caveat to my post above). Higher pressures as needed to inflate the lungs underwater = more toxicity. I'm no expert on dive medicine but I believe Navy Seal rebreathers use high O2 concentrations. I'm sure if it was possible to use such a James Bond like miniature device as this the would be doing that..
I accounted for the change of partial pressure (for 15 feet depth) in the calculations using the diving guidelines. It came out to 1.45 ppo2, which is still the allowable range.
The military units are much larger because they have mechanisms to maintain the allowable partial pressure across varying dive depths and probably other gas mixing stuff to prevent decompression problems. Their closed loop, so they have to scrub the co2 as well.
Even if they could solve the technical issues of using LOX at normal temperatures and then using it to provide the correct on demand volume of gas required for ventilation ( very unlikely IMO),
I dont have confidence in them at all. There are other LOX scuba equipment on the market and history (soviet), so it's not impossible to do..... but it's these guys no.
do they really think they're going to get away selling a device that lets someone mess around breathing 100% O2 underwater?
Ive been thinking about this as well. The liabilities are huge.
It might be possible to build a device using LOX, but that device wouldn't use shippable prefilled cylinders. You would have to fill on site, from a proper cryogenic storage system. Liquid oxygen is incredibly dangerous, and not easily available to your average consumer. The easiest way to get it is to accidentally condense it when working with LN2, which can lead to spontaneous fires/explosions.
There was a team working on an amateur-built LOX-rubber hybrid rocket motor. They had issues initially with the LOX spontaneously combusting when contacting residual organics in their fill system, though they clued up and got oxygen-safe parts pretty quickly.
This isn't the sort of thing you're going to haul down to your local gas station to fill like you would a propane tank.
I wonder if its possible they are using some other liquid, and depending on a chemical reaction to produce O2. Chemical oxygen generators are pretty old tech, and they get very hot, possibly requiring a heat exchanger. If you remember the big ValueJet crash in 1996, that was caused by an accidental initiation of an improperly stored oxygen generator, which started a fire (and then fed it with oxygen). Maybe the whole heat exchanger thing is more BS, to explain away why it gets hot without revealing how it works.