Breathing the gas from your BCD

[tursiops]

Only in 2017? My OW instructor taught that in 1996.

Lots of us taught it prior to 2013. That's when it became mandatory. My post above had a typo; it should have been 2013, not 2017.

 

[LI-er]

Somewhere around the 3rd breath the % inspired CO2 would be so ridiculous you'd lose consciousness.

According to the article cited in this thread, a study was done that confirmed 13 breaths can be recycled via a BCD and the amount of oxygen will be usable.

 

[LI-er]

Tanks falling out of BC's on openwater/tourist dives is probably one of the most common emergencies a DM will see.

That's hardly an emergency.

 

[LI-er]

In other words, the only conceivable occasion is when you are fully OOA in an overhead but within, say, 50 feet of an exit.

That's the only one I can think of. Although without the arbitrary 50' limitation. I wouldn't think "oh that exit is 60' away no point in even trying".

 

[rjack321]

According to the article cited in this thread, a study was done that confirmed 13 breaths can be recycled via a BCD and the amount of oxygen will be usable.

The oxygen isn't the most immediate problem. Your exhaled breath is 4+% CO2, just a couple "rebreaths" and you're going to be narced out of your mind, breathing incredibly rapidly, and confused to near unconsciousness before you ran out of oxygen.

 

[johndiver999]

That's hardly an emergency.

For whom? It really can be a bad problem if they go to the surface in rough water. A 40 lb cylinder bouncing off the back of your head is pretty much the definition of an emergency. Even underwater in calm conditions, it can cause serious stress, especially if the divers hands are full and they can not get a buddy to take care of it.

 

[johndiver999]

The oxygen isn't the most immediate problem. Your exhaled breath is 4+% CO2, just a couple "rebreaths" and you're going to be narced out of your mind, breathing incredibly rapidly, and confused to near unconsciousness before you ran out of oxygen.

Ok I'm going to breath in and out into a shopping bag at my desk.
For some reason, I think I am going to get more than 3 cycles.

 

[rjack321]

Ok I'm going to breath in and out into a shopping bag at my desk.
For some reason, I think I am going to get more than 3 cycles.

the pCO2 matters A LOT
Please don't try your broscience at 4 ATA

 

[LI-er]

The oxygen isn't the most immediate problem. Your exhaled breath is 4+% CO2, just a couple "rebreaths" and you're going to be narced out of your mind, breathing incredibly rapidly, and confused to near unconsciousness

The study addressed all of that when it was concluded that 13 breaths can be recycled.

Not "a couple".

 

[clownfishsydney]

Never heard of this method, simply dumping all the air and squeezing BCD before you backward roll works. Personally I would never want to breath the air in my BCD and I look after it pretty good.