Out of the many hundreds of deep dives I have conducted as diver, guide or instructor, I would suggest the 30 metre mark is a good guideline. The standard recreational depth limit is rather arbitrary, in terms of where it originates historically, but in my experience it's a pretty good delimiter for narcosis.
Yes, in part it's physiological - and I don't think anybody knows 100% why it occurs (current theory involves nitrogen dissolving at high partial pressure into the protein that surrounds our nerve fibres, thus interfering with signal transmission) but also as others have rightly stated before me, it can be affected by factors such as cold and visibility and therefore seems to have physical and psychological causes also.
I think it happens to almost everybody, but many people don't actually realise it's happening, and therefore claim to have never been narced. That may well be true but again, I think if you've spent a few minutes at 30metres, you've probably been a bit narced. I've seen people at 40 metres who are fine, and I've seen others go positively loopy at about 24 metres (and panic with it)
Narcosis is, I think, a subject too easily glossed over - yes it's not a serious condition in itself, but it can lead to serious problems in much the same manner that a person who chooses to drive after drinking a few beers may feel perfectly fine until the pedestrian steps off the sidewalk.... a diver might not think they are narced until they have to deal with a rapidly changing situation where quick decisions might have to be made. The standard PADI literature suggests that people will see pink elephants and offer their regulators to fish (and these things really do happen) and har har yes that's all very comical but narcosis can lead to problems and I think divers need to understand that it does have an appreciable effect.
It's also possible to some extent to 'acclimatise' to narcosis - it seems that regular deep diving and training will decrease your susceptibility - again, a rather unpleasant analogy to use but - in the same way a person who drinks regularly will build up a tolerance to alcohol.
Hope that helps somewhat,
Happy diving,
C.
Yes, in part it's physiological - and I don't think anybody knows 100% why it occurs (current theory involves nitrogen dissolving at high partial pressure into the protein that surrounds our nerve fibres, thus interfering with signal transmission) but also as others have rightly stated before me, it can be affected by factors such as cold and visibility and therefore seems to have physical and psychological causes also.
I think it happens to almost everybody, but many people don't actually realise it's happening, and therefore claim to have never been narced. That may well be true but again, I think if you've spent a few minutes at 30metres, you've probably been a bit narced. I've seen people at 40 metres who are fine, and I've seen others go positively loopy at about 24 metres (and panic with it)
Narcosis is, I think, a subject too easily glossed over - yes it's not a serious condition in itself, but it can lead to serious problems in much the same manner that a person who chooses to drive after drinking a few beers may feel perfectly fine until the pedestrian steps off the sidewalk.... a diver might not think they are narced until they have to deal with a rapidly changing situation where quick decisions might have to be made. The standard PADI literature suggests that people will see pink elephants and offer their regulators to fish (and these things really do happen) and har har yes that's all very comical but narcosis can lead to problems and I think divers need to understand that it does have an appreciable effect.
It's also possible to some extent to 'acclimatise' to narcosis - it seems that regular deep diving and training will decrease your susceptibility - again, a rather unpleasant analogy to use but - in the same way a person who drinks regularly will build up a tolerance to alcohol.
Hope that helps somewhat,
Happy diving,
C.