It depends on the kind of diving you are going to do. I personally have a 30 cf pony and a spare air. Most airlines won't let you take a tank with you without proving it is empty first, then they may charge a per diem for shipping it, and when you get to your destination you have to have it inspected by the shop filling it. Seems like a lot of hassle to me. As a Public Safety Diver, a pony is a must; as a wreck diver, a pony is a must; Ice diving, pony. You get the picture.

Nobends makes a great point: redundant is better by far. Again think of the type of diving you intend on using your spare air for. Then decide if it's right for you.

[annoying whiney sarcastic voice on]

"But Mom! On TV, the Baywatch babes can rescue an entire submarine crew with just one Spare Air cylinder!!

[annoying voice off]

On a recent trip to Athens Scuba Park, some friends did an experiment with a spare air to see how long it would last. Both were accomplished divers and in good physical shape.

With a full Spare Air cylinder, they were able to get 30 breaths while kneeling on a submerged platform at 20 feet. Then after refilling, they were able to get less than that while swimming at a constant depth.

Their summary is that a Spare Air is best for getting you to the surface in an emergency but at risk of contrcating deco illness since you would be rushing your ascent and not taking a 3 minute safety stop. Spare Air's should never be thought of as a replacement for a "true" redudant air source (aka a pony bottle) that will help you get out of trouble at a deep depth and possible allow you a safety stop as well.

--TexasMike

I'm a rec. diver and dive with lots of different people on dive boats all over the globe. I've learned you can't trust a buddy to be there. Therefore you must have that redundant air supply. Spare Air is perfect for me. Easy to take on commercial flights. Easy to fill. When doing 3 or 4 dives a day, you are very seldom over 100 ft. and that's just on the first dive of the day. All my Spare Air has to do is get me to the surface "immediately". I've tried that and it does. By the way, Spare Air c/w refill yoke is now $193 US.

Has anyone considered the difference in using Nitrox version of SpareAir [say 26-32% vs. standard air, and how that would lessen possibility of DCS on an emergency ascent, presuming the entire dive profile was based on use of a particular Nitrox mix. At least to 100' I would think that the 3 minute safety stop could be omitted or only partially satisfied if necessary, and if a hookah rig was deployed, even that would not be a problem. Over 100' the advantages of the pony bottle would be more significant. All this presumes also that only an OOA situation is going on, and no other problems. Any comments?

In the event of an OOA ascent, I'm not sure the benefits of the enriched air would be such that you'd really gain much from it. The total time of your ascent would be minimal in comparrison to the amount of nitrogen absorbed into your system. This isn't to say it's not a good idea. After all, every little bit helps. But it isn't like you are breathing the gas for an extended period or even long enough to really give much benefit. The 40-60 breaths you breath using this on an ascent isn't going to change what is in your system already a significant amount.

That's kind of what I expected. Since I have never dived with standard air, even in early dive training, I always feel like I have an edge with Nitrox in avoiding DCS. It just seemed, in a low air or OOA situation, that ascending on a standard air mix, while preferable to none at all, would not be as beneficial as staying with the EAN mix already being used. I've come up to 45 ft with 200 psi of 36% while lobster diving, and had to surface without the safety stop. No particular adverse effects, but the spare air would have made it safer and easier to complete my dive. Since I'm not rated as a technical diver, and haven't dived much below 100 ft., lugging the extra weight and bulk of the pony bottle on regular OW dives just doesn't have the appeal to me, though I grant that more air is better in theory. But I agree with previous posters that relying on a stranger as a buddy is problematic, and some kind of redundant air is a good idea...