To shop owners or owners of spare air tanks

[Hickdive]

If people bring in a pony for filling (a 3 litre or smaller cylinder) at the same time as bringing in a 10 litre or larger for filling, then I fill the pony for free.

Generates a little goodwill and ensures that people actually keep their ponies filled. There's not a lot of air in them to start off with and divers, being generally as tight as a duck's arse in a following sea, have a habit of not refilling until they drop to around 150 bar or less in order to save a couple of quid if they normally get charged for pony fills.

 

[BRT]

Just fill it off of your first tank. You won't notice the difference and then it is available for the rest of your time until you need to empty it to fly. It is not enough air but it is better than nothing, so long as you understand the limits. You should switch to it some time and see how it breathes and how fast the pressure drops.

 

[Eric Sedletzky]

I can't comment on the filling part, but I Will comment on spare air's in general.
Next time you are out diving switch to your spare air at 60 to 80 feet and begin to head up at a normal rate. Have your regular supply ready and do this early in the dive so you don't have a lot of built up NDL.
Just see how long that spare air lasts and see if you can make it up to the top going at a normal rate.
If you don't make it and have to switch back to your main then what makes you think you'd be able to survive a real incident when you might be breathing three times as hard and all freaked out. Remember, this could happen when you are really deep and are right up to your NDL. This could lead to a severe injury or death. We've had many discussions about spare air's, and the overall concensus is that they are very limited in safe use and can give a false sense of security in anything but very shallow short dives. Many have nicknamed them "spare death" for those reasons.

 

[Bob DBF]

It's not the Spare Air's fault that it is small, it does a good job for what it was made for, but is was not designed to be a stage / pony bottle.

The fact that divers would think this is a lot of air, or an LDS would sell it to "make you safe" completely overlook the limitations of the device. Beware of anyone that wants to sell you gear on the basis of it being "life support equipment"

Before the SPG I made my share of emergency ascents, however once I had an SPG I got out of regular practice. When they became available I carried a spare air for awhile, years ago, on deep dives as grabbing a couple of breaths on an emergency ascent seemed to me to be better than none. When I got even older, and the surface seemed a bit further away, I switched to a 19 cuft pony to give a more leisurely emergency ascent. I have never actually needed to use either.

I don't see a problem with carrying a spare air as long as you understand its limits.


Bob
-------------------------
Has tried split fins too and is still alive.

 

[DavidFL]

^this by Bob DBF.
I practiced and taught emergency ascents from when I was first certified in 1967 until I stopped being an active YMCA/PADI instructor in the early '80s. Also did emergency ascents in Navy towers, and both 'Dilbert Dunkers' and helicopter underwater evacuation trainers. I have had a spare air for several years (enough to get it hydro'd once) that, for me, is an extra resource immediately available to give me a minute or so to help sort out a situation if I ever need it. I also subsequently switched to a 19 cu ft. pony for local dives; I continue to take the spare air with me when I'm travelling by air to dive. I have never used either alternate air underwater except for practicing deployment. As previously posted, I fill it from my tank once and make the mental note that I have 3 cu ft. less.

And I'm using my split fins in the pool to rehabilitate after a total hip replacement.

 

[tech_diver]

Customers think of a 'free top off' of their scuba tank as just 500 PSI more to top off the tank. However, there are LDS owners who have pointed out that it takes more compressor time and energy to get their banks charged up to the last 500 PSI. It's been said that they might give the first 1500 PSI free and charge for every PSI after that.

 

[HeatCker]

Just fill your "spare air" and go diving, as mentioned you will not notice the difference. Also as mentioned above, understand that it is an "ascent bottle", it is NOT a pony bottle. Use it, practice with it, get comfortable with it, and learn its limitations .. the air inside is limited. Most of my local diving is 30' - 60'. I dive deeper (st lawrence, tobermory, lake ontario, caribbean) but that depth, 30 to 60', represents my local go to dive holes. I have and dive with a spare air, 3 cuft, i've had it as part of my gear for a number of years. For most of my diving the spare air is more than adequate "as a backup ascent bottle". I have practiced with it and am comfortable with it. I can easily come up from 50' and include just under 2 minutes at safety stop depth, 15'. Most of the negative comments about the spare air come from divers that have never used one or ... come from divers that dive deeper and need the real benefits of a properly sized pony bottle. If you regularly dive shallow and practice with your spare air you should be fine. If you regularly dive deeper than consider something more appropriate, lots of good advice on this forum. The main thing is, pay attention while your diving and you should never need your back up bottle. I give you this info not to start a discussion about the benefits/draw back of the spare air. I give you this info because you already own a spare air and it is important to practice with it and learn its limitations.

 

[redacted]

I can't comment on the filling part, but I Will comment on spare air's in general.
Next time you are out diving switch to your spare air at 60 to 80 feet and begin to head up at a normal rate. Have your regular supply ready and do this early in the dive so you don't have a lot of built up NDL.
Just see how long that spare air lasts and see if you can make it up to the top going at a normal rate.
If you don't make it and have to switch back to your main then what makes you think you'd be able to survive a real incident when you might be breathing three times as hard and all freaked out. Remember, this could happen when you are really deep and are right up to your NDL. This could lead to a severe injury or death. We've had many discussions about spare air's, and the overall concensus is that they are very limited in safe use and can give a false sense of security in anything but very shallow short dives. Many have nicknamed them "spare death" for those reasons.

The biggest difference is that when you opt for a spare air for scuba backup, you also forget about normal ascent rates. While a properly sized bail-out bottle allows for a normal ascent, a spare air is more like a few breathes to get the diver through a CESA, It will provide quite a bit more than the expanding gas in an "empty" tank. The nice thing about a spare air option is that it travels quite nicely within current luggage weight restrictions.

If you are looking to have a shop fill your spare air, you should expect them to require a current hydro and VIS.

 

[Lorenzoid]

Just think of it as your Controlled Emergency Swimming Ascent Receptacle (CESAR), not a pony or bail-out bottle. It's not enough volume to do a "safe" ascent, but it may somewhat increase the odds that you won't die if you should find yourself having to do the kind of emergency ascent we learned in OW class to use as an absolute last resort.

 

[spectrum]

As said, it's a small hit on your first tank of the trip and when you come right down to it the air is still with you. That small hit on that first dive should amount to a dive planning rounding error. You can ask for the top-off but don't fret it.

I will reinforce that you be grounded in what that spare air really provides. It may not really meet your expectations.

Pete