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Q & A: snorkeling limits

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Most recent answer: 10/22/2007
Q:
How deep can one swim underwater with just a snorkel or long tube knowing that the lungs can operate against a pressure differential of less than 0.05atm.?
- julie
A:
The pressure underwater goes up about 1 atm for every 10 m deeper that you go. If what you say is right, your lungs would have trouble expanding enough to inhale at a depth of only about 0.5 m. That sounds a little small- are you sure that lungs can't work against a bit higher pressure, at least for a while?

Mike W.

Most snorkel tubes are very very short -- they're designed for face-in-the-water viewing of fish and coral reefs. That's not to say you can't take a deep breath and dive down as far as you can go, holding your breath. The water pressure gets pretty high pretty fast, and this compresses the air in your lungs. So long as you don't try to exchange air with a reservoir at a much different pressure, you're okay (the pressure inside your lungs isn't all that different from the pressure of your surrounding organs which is close to the surrounding water pressure).

If you had a long tube extending to the surface and tried to breathe through it from a depth of 10 meters or so, you'd have a pressure differential of one atmosphere to worry about. It'd be kinda like sucking on a perfect vacuum. You will be able to exhale, but not inhale. Talk about getting the wind knocked out of you. 0.05 atmospheres does sound rather paltry, though.

Tom

(published on 10/22/2007)

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