Holding your breath question?

"Bruce W.1" <[email hidden]> wrote in message
news:2UElc.37898$NZ4.13152@lakeread05...

Quoted message said:

For survivability underwater, is it better to hold all the
air in your lungs or exhale a small amount to reduce CO2?

Sorry if I got carbon dioxide and monoxide mixed up.

Or to paraphrase, is the harm of CO2 in your lungs greater
than the lack of oxygen?

Thanks for your help.

It is the oxygen in your blood stream not your lungs which
will save you. Once you have breathed in and held your
breath for about ten to fifteen seconds there will be
little further gaseous exchange of oxygen in to your blood,
so it is irrelevant whether you keep holding or not - do
whatever feels most comfortable. The feeling of having to
breathe in is caused by the build up of CO2 in your blood
(& lungs to some extent), so it may help relieve the
feeling a bit if you trickle your breath out slowly, but it
won't actually affect your survivability other than making
you a bit more comfortable. Carbon monoxide (CO) is not
produced by the body, but is a by-product of the combustion
of hydrocarbons, so is found in car exhaust fumes and gas
boiler outlets etc. It is lethal and once in to your
bloodstream is stable and very hard to remove. So unless
you want to die a nasty death, or get brain damage, don't
mess around with carbon monoxide. For that matter Carbon
dioxide (CO2) will also kill you if you get enough of it,
so don't experiment with it.