Q.What is a condition called 'Nitrogen narcosis' ?

Nitrogen narcosis is an anaesthetic-like state caused by excess dissolved nitrogen acting on the nervous system when a diver breathes compressed air at great depth.

Air is normally about 78% nitrogen, a gas that is physiologically inert at normal atmospheric pressure and is simply breathed in and out without producing any noticeable effect. However, when a diver descends to significant depths underwater while breathing compressed air from a cylinder, the surrounding water pressure (and hence the pressure of the air being breathed) increases greatly with depth. At these elevated pressures, much larger amounts of nitrogen than normal dissolve into the diver's blood and, from there, into fatty/nervous tissues, including the brain. This excess dissolved nitrogen begins to exert a narcotic (anaesthetic) effect on the nervous system, producing symptoms similar to alcohol intoxication — such as euphoria, overconfidence, impaired judgement, slowed reaction time, drowsiness, and reduced coordination. This condition is called nitrogen narcosis (informally 'rapture of the deep' or the 'martini effect'), and it typically starts to become noticeable at depths beyond roughly 30 metres, worsening as depth …