helium

Because it binds with receptors normally used for oxygen thus depriving the brain and it could kill you. Aside from that, nothing.

Breathing helium with insufficient oxygen leads to suffocation. Without carbon dioxide, your body doesn't get the signal that something is wrong. If you breath straight helium, don't hold your breath, and don't do it for too long. Seriously.

Not sure about that, Nick. A helium/oxygen mixture is used instead of the normal oxygen/nitrogen mix to avoid becoming bent.

Helium does not "bind" to anything*. Neutral helium at standard conditions is non-toxic, plays no biological role and is found in trace amounts in human blood. The danger, that of asphyxiation, arises simply because it displaces oxygen needed for normal respiration. Also, if helium is inhaled directly from pressurized cylinders the high flow rate can fatally rupture lung tissue (barotrauma).

* Probably thinking of carbon monoxide.

You mean, seals respond directly to insufficient oxygen? If so, I didn't know that.

Squid don't use the standard bouyancy compensation of fishes, so they can change depth (however they do it) without rupturing the bladder.

Well, depending on the circumstances,
it might cause u to float away, Nick. That has happened.
That might not be Fun.





David