How long can a person hold his or her breath?: Information from Answers.com Mobile

You usually don't have to think much about your breathing because your brain controls it automatically. When you have a lot of carbon dioxide-the waste gas produced by body processes-in your blood, your brain gets the message and tells your lungs to exhale and get rid of it. This action then causes you to inhale, drawing in air that eventually delivers oxygen to every cell in your body. This carefully regulated exhaling and inhaling takes place about 10 to 14 times each minute when you are breathing calmly.

When you need more oxygen than usual, your brain takes care of that, too. When you're exercising or working hard, your brain tells you to breathe more quickly, taking in 15 to 20 times more air. If that still doesn't deliver all the oxygen that your muscles need, you may "run out of breath," which forces you to rest. You will still breathe hard at that point-every second or so-until your muscles are able to work again.

So you can see that trying to stop the automatic way that your brain controls your breathing is nearly impossible. When you hold your breath, carbon dioxide builds up in your blood, unable to exit through your lungs. Not long after that-in less than a minute-your brain will force you to take a deep breath, as hard as you try not to. You may be able to hold your breath a little longer than a minute if you prepare your lungs first, taking several deep breaths to fill them with as much air as possible before you start. With a lot of practice and physical training, some people have been able to hold their breath for a few minutes. Be careful testing your breath-holding limits, because at some point the lack of oxygen could make you faint.

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