Deeeep diving theory

[chrispete]

My wife and I decided to calculate the depth at which an average person would drain an 80cf tank in a single breath (this came out of a discussion about deep diving.) Our assumption was that the average person would use .5 liters per breath at the surface. Anyone want to do some math and see if we can match up answers?

Coincidentally, a study came out today that suggests that people who work puzzles and problems have less chance of getting dementia, so we're posting this as a public health service.

We'll post our answer in a bit.

edited to change the assumption from 5 to .5

 

[Rick Inman]

26 feet.



-Oh! You're not talking about my friend Big Bubba Bob. Never mind....

 

[daniel f aleman]

5 liters per breath at the surface, eh?

 

[chrispete]

OK, we're not respiratory techs, further Googling shows .5 liters tidal volume, so for this exercise let's go with .5

 

[LSDeep]

My wife and I decided to calculate the depth at which an average person would drain an 80cf tank in a single breath (this came out of a discussion about deep diving.) Our assumption was that the average person would use .5 liters per breath at the surface. Anyone want to do some math and see if we can match up answers?
.....
We'll post our answer in a bit.

edited to change the assumption from 5 to .5

interesting one, i nearly had a top of my head answer, til i remembered some basic physics! so its not that simple!!! just sheer interest, where did you get the .5 ltr from? isnt the average lungvolume a bit more?

 

[PfcAJ]

Ok, I'll stab at it. My resting SAC rate is .4cuft/min. We'll assume that my resting respiratory rate is 12/min. This means that every breath on the surface is about .033cuft. I get apporximately 2424 breaths from 80cuft @1 atmosphere.

Our goal in this is for one breath to equal 80cuft.

Unless I'm really behind on my math (I'm better at science stuff, like chemistry and biology than math), it would take 2424 atmopheres to drain an al80 (if it really had 80cuft in it...ok the dive shop messed up today and overfilled it) in one breath. .033cuft per breath at the surface, multiply that by 2442 atmosheres equals 79.99cuft.

2424 atmospheres absolute is something like 79,959ft.

 

[do it easy]

Don't do it- It's a trick question. The internal volume of an AL80 is larger than the tidal volume of human lungs. You couldn't suck all the air out in a single breathe!

OK, how many liters (water volume) in an AL80? or how many cf in a liter?

Edit: OK, I've heard of some of those divers with foreign rulers talk about 12L and 15L tanks. Let's use a 12L tank filled to 232 bar which is 2784 liters at the surface. To compress this into the volume of single .5 liter breathe- you would have to subject it to 5568 ATA, which corresponds to a depth of 183,744 fsw (or 55,680 meters).

Sorry for the metric calcs...

 

[chrispete]

interesting one, i nearly had a top of my head answer, til i remembered some basic physics! so its not that simple!!! just sheer interest, where did you get the .5 ltr from? isnt the average lungvolume a bit more?

"Tidal volume is the amount of air taken into the lungs in a single breath. In the average adult, tidal volume is about 0.5 liters" per http://hypertextbook.com/facts/2001/LaurenCalabrese.shtml

BTW average maximum lung volume is more (4-6 liters), in other words we can take a much bigger breath, but in normal breathing pattern you don't fill your lungs to max with each breath.

 

[LSDeep]

"Tidal volume is the amount of air taken into the lungs in a single breath. In the average adult, tidal volume is about 0.5 liters" per http://hypertextbook.com/facts/2001/LaurenCalabrese.shtml

BTW average maximum lung volume is more (4-6 liters), in other words we can take a much bigger breath, but in normal breathing pattern you don't fill your lungs to max with each breath.

ok you win, i believe it - never really thought about it that way

 

[LSDeep]

Don't do it- It's a trick question. The internal volume of an AL80 is larger than the tidal volume of human lungs. You couldn't suck all the air out in a single breathe!

OK, how many liters (water volume) in an AL80? or how many cf in a liter?

about 10 -11ltr in real water volume (or air on surface pressure for that matter).