Posted by MHK on September 13, 2000 at 12:13:42:
In Reply to: Secondary Air source question posted by JRM on September 13, 2000 at 08:38:06:
There are a couple of schools of thought on this subject so I'll give a brief overview of the most common and then I'll conclude on what I do..
First off you are correct about spare airs and teh related costs. To the extent you are going to invest in a redundant air supply the spare air is worthless. While for sure 3 CuFt. of air is better than none, if you are going to spend X # of dollars you mind as well get a real set up.
Many people use the standard 13 CuFt pony bottle mounted on the primary tank. This seems to be the most common and while I get pretty anal about my gear configuration for 99% of he diving that is done in our market this should be suuficient.
If I were to carry a redundant air source, I would mount it in the fashion of a stage bottle attached to a d-ring on the chest and a hip d-ring. The advantage of mounting it this way is that it is removable and you could hand it off to your buddy if necesary. But in all frankness, most divers use the pony to solve for the OOA scenario when solo so my recomendation isn't probably necessary for the solo diver. Since I no longer solo I think in terms of team diving -v- solo diving.
As for depth limit and such ( stipulating that OE is beyond the scope of the discussion ) I don't know that there is really a hard and fast rule inasmuch as if you blow and go you risk embolizing. Clearly an true independant air source can help slow the ascent by providing added time, so in that regard they are helpful. As may have noticed from some of my earlier posts I have tried to get divers to focus on the team concept so as to render a pony unnecessary. It seems to me that a buddy, in addition to additional air, can help provide for calmness, and additional set of eyes, lift source.
But we have beat the solo -v- buddy diving to death last week so let's stay focused on your question.
Bear in mind that if you do decide to penetrate an OE that my answers will change.
The other option to consider is isolated doubles.
Regards