OldNSalty
Contributor
So I have a question, years ago I use to dive with a friend/instructor and when he took groups of friends out on his boat we would always hang a bottle at 20 feet with a 40% O2 mix (might have been even higher-dont recall). He said it was there for us to use at our safety stop if we wanted to. Some of us would be diving NITROX some air but no one would necessarily be breathing the same % as the safety bottle.
I know zero about planning a dive when you use different mixes (if such things are even allowed). I asked him about O2 toxicity and how to calculate it seeing how I would be going from a 32% mix to a 40% mix at the end. He told me it wasnt an issue as long as you werent pushing the limit anyway (which you shouldnt). He said the extra O2 at 20 feet for 3 to 5 minutes was mathematically insignificant. He claimed the benefit was that you off gassed more nitrogen at the safety stop. (I can see this benefit as you would be breathing in less nitrogen so I suppose that is correct)
Of course, he wasnt suggesting that you change you dive plan; he said it just added an extra margin of safety and that personally, he always felt better when diving like this.
So the question is, was this a good idea or an accident waiting to happen? I like having the staged bottle but I am not sure I like having a different mix in it.
I know zero about planning a dive when you use different mixes (if such things are even allowed). I asked him about O2 toxicity and how to calculate it seeing how I would be going from a 32% mix to a 40% mix at the end. He told me it wasnt an issue as long as you werent pushing the limit anyway (which you shouldnt). He said the extra O2 at 20 feet for 3 to 5 minutes was mathematically insignificant. He claimed the benefit was that you off gassed more nitrogen at the safety stop. (I can see this benefit as you would be breathing in less nitrogen so I suppose that is correct)
Of course, he wasnt suggesting that you change you dive plan; he said it just added an extra margin of safety and that personally, he always felt better when diving like this.
So the question is, was this a good idea or an accident waiting to happen? I like having the staged bottle but I am not sure I like having a different mix in it.