To shop owners or owners of spare air tanks

[Bob DBF]

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.

If they just fill the tank properly there would be no need to top off a tank. My LDS doesn't seem to have a problem hitting the service pressure of the tank on the first try.


Bob

 

[spectrum]

My LDS doesn't seem to have a problem hitting the service pressure of the tank on the first try.


Bob

You are living a charmed life my friend.

 

[BRT]

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.

Do you know of any incidents where people have died using their Spare Air to ascend?

 

[Eric Sedletzky]

Do you know of any incidents where people have died using their Spare Air to ascend?

No, because I don't know anybody silly enough to use one.
but math is math. Just like I know if you are driving down a busy two lane road at 55 mph and decide to turn the wheel to the left into oncoming traffic you might be severely injured or you could die. But I don't personally know anybody who has done that either.

 

[redacted]

Do you know of any incidents where people have died using their Spare Air to ascend?

No, because I don't know anybody silly enough to use one.

So, as far as we know, there have been no scuba deaths attributed to an OOA event where a "spare air" device was in use?

 

[Eric Sedletzky]

So, as far as we know, there have been no scuba deaths attributed to an OOA event where a "spare air" device was in use?

Don't know, It's possible, somewhere at sometime in some country, who knows? It would take some serious research to find out.
The point is, as small as spare airs are there is no mathematical way they hold enough gas to make a safe ascent from 100' when a diver has reached max NDL without injury or possible death. Anybody who thinks these units are a safe alternate gas supply at those depths has a false sense of security. Like I said, they are sufficient for very shallow water where the person is nowhere near their NDL and can make a fast direct ascent.

 

[Bob DBF]

So, as far as we know, there have been no scuba deaths attributed to an OOA event where a "spare air" device was in use?

Considering the large amount of accurate information available about SCUBA deaths, if a diver is found on the bottom with an empty tank we will probably never know if he died before or after the tank was emptied. I don't believe I've ever read in the accidents forum whether a diver even had a spare air during any accident. Lack of evidence is not proof, or in the words of Wylie coyote, there have been no scuba deaths attributed to an OOA event where an anvil was in use.

The limitation I found with the spare air had nothing to do with the volume of air. I found that sand would get into the reg and not allow the reg to completely close after a breath (worked fine in a clean environment) I spent more time cleaning it than I did using it. I suppose I could have just gone diving on good days, but that didn't cross my mind.

It's just another tool, you just have to know when to use a tack hammer and when you need a sledge hammer.



Bob
-----------------------------------
Always use the right tool for the job. A hammer is the right tool for any job. Anything can be used as a hammer.

"This is scuba board, where problems are imagined or overstated......and chests get thumped about what some would do about those "problems" "- PullMyFinger

 

[redacted]

Considering the large amount of accurate information available about SCUBA deaths, if a diver is found on the bottom with an empty tank we will probably never know if he died before or after the tank was emptied. I don't believe I've ever read in the accidents forum whether a diver even had a spare air during any accident. Lack of evidence is not proof, or in the words of Wylie coyote, there have been no scuba deaths attributed to an OOA event where an anvil was in use.

The limitation I found with the spare air had nothing to do with the volume of air. I found that sand would get into the reg and not allow the reg to completely close after a breath (worked fine in a clean environment) I spent more time cleaning it than I did using it. I suppose I could have just gone diving on good days, but that didn't cross my mind.

It's just another tool, you just have to know when to use a tack hammer and when you need a sledge hammer.



Bob
-----------------------------------
Always use the right tool for the job. A hammer is the right tool for any job. Anything can be used as a hammer.

"This is scuba board, where problems are imagined or overstated......and chests get thumped about what some would do about those "problems" "- PullMyFinger

It is not that I am a fan of spare air and I do recognize its limitations. But I still believe spare air is better than no air and see no basis for the name "spare death" that some try to associate with it.

Yes, it is just another tool which, if used properly, can be helpful.

 

[scagrotto]

spare air is better than no air

That would seem pretty obvious, but the same reasoning means that the original 1.6CF(?) spare air or even something substantially smaller is also better than nothing. At what point does that "better than nothing" become next to nothing?

It will provide quite a bit more than the expanding gas in an "empty" tank.

If that empty tank is an AL80 at 99' it's got 1.6CF of air, of which 1.2CF is theoretically available by the time you reach the surface. Based on breathing a tank dry in 3 or 4' of water I'm pretty sure my reg would let me use a good bit of that 1.2CF during the ascent, so I'm not sure it's accurate to say the spare air has substantially more, especially since they still offer a model that's only 1.7CF.

Others may feel differently, but in addition to the other advantages of a real pony bottle I'd prefer to avoid doing business with a company that
1. Markets a nitrox version. Is that anything but an attempt to reel in people stupid enough to think the additional N2 uptake is going to matter during an emergency ascent?
2. Claims that spare air is better than a pony. Again, I see that as disingenuous and self-serving attempt to market to, and at the expense of, the stupid.

Sure, it's better than nothing. It's equivalent to a whopping 115psi in an AL80.

And as far as how to get it filled, that last means that using 3000psi rental tank will leave you with only 2885 psi for your first dive. Just suck it up and shorten your dive by a couple of minutes. Of course if you figure the spare air is good enough as a safety device you can be back on the boat with 385 psi instead of 500.

 

[redacted]

That would seem pretty obvious, but the same reasoning means that the original 1.6CF(?) spare air or even something substantially smaller is also better than nothing. At what point does that "better than nothing" become next to nothing?

At the point where it is as hard to suck one more breath from your primary tank.

If that empty tank is an AL80 at 99' it's got 1.6CF of air, of which 1.2CF is theoretically available by the time you reach the surface. Based on breathing a tank dry in 3 or 4' of water I'm pretty sure my reg would let me use a good bit of that 1.2CF during the ascent, so I'm not sure it's accurate to say the spare air has substantially more, especially since they still offer a model that's only 1.7CF.

Others may feel differently, but in addition to the other advantages of a real pony bottle I'd prefer to avoid doing business with a company that
1. Markets a nitrox version. Is that anything but an attempt to reel in people stupid enough to think the additional N2 uptake is going to matter during an emergency ascent?
2. Claims that spare air is better than a pony. Again, I see that as disingenuous and self-serving attempt to market to, and at the expense of, the stupid.

Sure, it's better than nothing. It's equivalent to a whopping 115psi in an AL80.

And as far as how to get it filled, that last means that using 3000psi rental tank will leave you with only 2885 psi for your first dive. Just suck it up and shorten your dive by a couple of minutes. Of course if you figure the spare air is good enough as a safety device you can be back on the boat with 385 psi instead of 500.

The big difference is that 1.6 cu ft is what would be available when you reach the surface, while the 1.7 or 3.0 Cu ft in the spare air is available when you go for that first breath after the OOA/LOA.

Yes, the EAN version is rediculous. The only time a spare air might be better than a pony is when you try to pack it in your baggage. If a spare air (or pony) changes the management plan for your back gas, you are probably making a mistake.