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post #28 of Old 07-20-2013
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Re: Need answer to something I've always Wondered About

Originally Posted by rcontrera View Post
Not a problem. I sell an Oxygen analyzer to scuba shops as part of some of my compressor stuff. One of my dive shop customers did a check to see how much oxygen was left in an exhaled breath. Normal air has approximately 21% O2. Our exhaled breath came in at about 19% which makes a lot of sense. After all, we blow our exhaled breath into the lungs of others when doing mouth to mouth!

This whole thing has nothing to do with the resistance of air flow in a long snorkel or breathing your exhaled breath. It is all about the difference in pressure on the lungs. You just can't breathe in when water pressure is squeezing your body.
Hmm well you should look up hypercapnia [excess CO2] which is a known problem with long snorkels.

Additional sources of carbon dioxide in diving[edit]

There is a variety of reasons for carbon dioxide not being expelled completely when the diver exhales:
The diver is exhaling into a vessel that does not allow all the CO2 to escape to the environment, such as a long snorkel
Hypercapnia normally triggers a reflex which increases breathing and access to oxygen, such as arousal and turning the head during sleep. A failure of this reflex can be fatal, as in sudden infant death syndrome
Please note the word FATAL.
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