Spare Air questions

[WIdiver_Paul]

If you really want a good answer for whether or not to use Spare Air's, we must first thoughtfully analyse why it is that this is to be needed. Everyone keeps inciting deep dive OOA as a reason to need one, and Spare Air has been tested and proven NOT to work on dives much deeper than about 50 feet due to the extremely low CF in that can. If you're going to do deep dives, you need to plan your dive FIRST, and then dive your plan. This is indeed part of the DIR mentality, but it doesn't mean you can't do it as well- You should know your RMV (Respiratory Minute Volume) and be able to know how much gas you will need for a given dive, and you should also know your buddy's RMV and gas requirements before you embark on any type of serious diving (for me that's anything that would be difficult to do an ESA from, about 50 feet from the surface). If you know your gas requirements for a dive, and then use the rule of thirds (one third to go down/in, one third to return, save one third for emergency), you can eliminate the need for having to carry that $300 piece of #@$%@ around with you (and you'll probably forget you have it in an emergency-- unless you drill with safety equipment, you're going to be just like every other panicked diver and flail around until you grab your buddie's reg out of his mouth!!); Every diver should be responsible for themselves and for their buddy- jumping in the water and breathing your tank down to 500 psi on a 130' dive with no planning is just irresponsible and an inconsiderate thing to do for everyone (including rescue personnel that may have to retrieve your body).

For more information on gas planning and RMV's, take a deep air course (not recommended), a cavern course (hard to justify around here), or see the following article on Divernet.com :