Quote: (Originally Posted by Alan Mackenzie)
What's the principle behind it?
The idea is that oxygen is a vasoconstrictor and it means that breathing it for prolonged time means that your gas exchange gets impaired. By how much nobody knows but it seems to be a goood idea to let your body rest for a while after breathing pure O2 for some time.
Quote: (Originally Posted by Alan Mackenzie)
Does the air break time count as part of your deco stops or is it additional time tacked onto the deco?
Some deco programs do support it and calculate your gas loading accordingly, but I think majority of divers just won't be bothered and count them as part of the deco. I think the general consensus is that you should think of back gas breaks after some 20-30mins at 6m on O2.
Best Regards