Reply #19: Because the nitrogen inhaled was not under pressure...

[hootinholler]

Free divers have no fear of bends because they breath air at surface pressure and then descend. If the air you inhale is pressurized then nitrogen can be absorbed into the blood stream and boils off as the pressure on the body is released. As a poor analogy, but I can't think of another one: Fill a balloon at the surface and take it down in the water, the balloon gets smaller due to compression but will not pop when brought back to the surface. Inflate a balloon at depth with compressed air and it will pop as it ascends.

It also takes time for the nitrogen to be absorbed, thus the concept of 'bottom time' in diving. Bottom time and depth determine the length and depth of decompression stops during an ascent.

-Hoot