A word about pipping and peeping. A chick can't peep if it hasn't pipped(internally). When it pips internally into the air sac is when its lungs expand and it starts to breath. Then and only then can it start to shut down the blood circulating in its membranes which have been supplying it with oxygen up to this point. It is as this point that it can "drown" if there is too much fluid in the egg. Then the yolk is triggered to be absorbed as the last step before hatching. When the oxygen in the egg is insufficient for the chick, it makes the external pip so that it can breathe while the last of the blood and the yolk are being drawn into the body.