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Thread: Spare Air tank through TSA to Bonaire?

  1. #11
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    It is not unreasonable to believe you will "bailout" to your spare gas, in an agitated state, where you will consume one cubic foot of gas in one minute based on surface consumption. For each 33 feet of depth the compression of gas will result in an additional cubic foot of gas consumed. So, two cft per minute consumed at 33 feet; three per minute at 66 feet and four cft at 99 feet. Since your training recommends you ascend at the rate of 30 feet per minute in order to avoid lung over expansion injuries, it will take a known amount of gas to safely surface from a known depth. Just do the math and then you will know how "safe" your spare air really is and how long it will last at each depth. When the manufacturer tells you how many breaths you will get from their product the number is always a function of this calculation. Less breaths from deep and more breaths from shallow and all depending on the volume of the canister. So if you have purchased the 3 cft model and you breathe it at 66 feet it will last for one minute. If you are in an emergency situation this is hardly enough gas to "slowly ascend" from your depth. From 99 feet you need 4cft to get to 66' and another 3cft to get to 33' and another 2cft to get to the surface for a total of 9cft with no safety stop. Most recreational divers who carry a redundant air source use a 13cft "pony bottle" which works much better than a relatively useless "Spare Air".

    (SPARE AIR is designed to get someone to the surface in the event of an emergency. The SPARE AIR family consists of three models all at a pressure of 3000 psi. The 170 model holds 1.7 cubic feet of air or approximately 30 breaths at the surface, the 300 model and the 300-N Nitrox model hold 3.0 cubic feet of air or approximately 57 breaths at the surface.)



  2. #12
    DSearle is offline Bonaire Lover Bonaire Talker
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    Pay attention to mpement. Three cubic feet of emergency air is really not enough. I ran the numbers based on my own surface breathing rate (0.45 cubic feet per minute) which is pretty normal. Using the safe ascent rate (30 ft per minute), your 3 cube bottle will not get you to the surface from below 75 feet. And that is assuming NO EFFECT from the anxiety of the situation. If you put in a stress factor of 2 (which is probably too low), the depth limit is reduced to 45 feet. To put it another way, in 90 feet of water under stress, you breathe about 3.5 cubic feet of air per minute. It's going to take 3 minutes to make a safe ascent. 3 cubic feet is not enough.

    On the other hand, my 13 cu. ft. pony bottle will get me up from a depth of 130 ft, INCLUDING a stress factor of 2. From 110 feet, I'll even have time for a safety stop. Starting at 90 feet with my pony bottle, I'm breathing 3.5 cubic feet per minute, which means I have 3.7 minutes of air in the bottle. When I get up to 30 feet, because of the lower pressure, I'm now only breathing 2.2 cubes per minute. And that means I now have 3.8 minutes of air left. When I get up to 15 feet, I actually have more than four minutes of air--plenty to make my safety stop, which is more important than usual because of my relatively rapid ascent. Understanding all this would likely keep my anxiety level down, which would help me keep my breathing under control. This is why "most recreational divers who carry a redundant air source use a 13 cu.ft. pony bottle." It turns out 13 cu. ft. is really the smallest amount of air that will get you back from any recreational depth.

  3. #13
    tholland is offline Bonaire Lover Bonaire Talker
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    Thanks for those vital statistics and calculations! Looks like I'll have to look into getting a 13 cu. ft. pony while living/diving on Bonaire! Great suggestion, thanks!

  4. #14
    tholland is offline Bonaire Lover Bonaire Talker
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    By the way, a 100 or so years ago, when I was first trained in scuba, in our 'advanced course', we were required to do an emergency ascent from about 25 feet. You went down to 25 feet with your instructor, and he turned off your air tank....when you couldn't pull any more breaths out of the tank, you were supposed to ascend quickly to the surface while blowing air out of your lungs at the same time. The instructor swam face to face with you to make sure you were blowing lots of air bubbles on the way up. I guess that 'emergency ascents' are no longer practiced....probably because they were foolishly dangerous for the student and the instructor both...but it was an interesting exercise to complete and survive....and to try and control your anxiety having no air to breathe from 25 feet up!

  5. #15
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    wwguy is offline Bonaire Lover SUPPORTING MEMBER - Bonaire Talker
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    Interesting discussion. I've carried a Spare Air periodically in certain dive situations since my NAUI Course Director, a former special forces dive trainer, suggested it during my instructor training 19 years ago. I agree with Michael's observation that a Spare Air is an emergency solution only and that any time it's in your mouth you should be headed towards the surface. "Testing" it by breathing it until empty at depth doesn't accurately reflect its useful range for any particular diver.

    I'm curious what scenarios you pony bottle fans imagine might lead to running out of air at depth while diving on Bonaire at recreational depths? Most divers dive deepest during the early portion of the dive and much shallower on the return portion. Well-maintained modern scuba regulators and tank don't just spontaneously fail during a dive, and well-trained divers (especially those diving deep or solo) don't just forget to monitor their gas or depth. If you run out of gas and need to switch to a redundant bailout system at 80+' you've got other issues beyond just which bailout system to haul on vacation with you.

    I often carry a Spare Air when diving solo from shore on Bonaire. My typical solo dive profile is max depth of 70' to 80' early in the dive, with the return leg of the dive being no deeper than 45' and often much shallower. For the past 150 or so Bonaire dives my average bottom time varies from 70 to 75 minutes on an 80 cu ft tank and I always return to shore with 1000 to 1500 psi. My gas consumption rate is sufficient to safely get to the surface from 50' to 60' on 3 cu ft of gas if necessary.

    I can't imagine a scenario where I'd ever run out of gas period on a dive, much less during the deepest early portion of the dive where I have the most gas in my tank. But I still carry the Spare Air for peace of mind (mine and my wife's) as a preferable alternative to performing an emergency swimming ascent during an unexpected situation at any depth. At least once per trip, usually during one of the last dives, I practice ascending while breathing off of the Spare Air. It works just fine at normal ascent rates from the depths where I am during the latter half of my dives and would suffice as an emergency solution from deeper depths. While either would be bad , for me it's preferable to be bent and alive at the surface rather than drowned at depth. The Spare Air is an emergency contingency solution, not an alternate or supplement to my primary scuba unit.

    Unlike a pony bottle setup a Spare Air is relatively inexpensive, compact, lightweight, easy to travel with, easy to fill from a scuba tank, easy to carry, and easy to use. It's also easy to hand to another distressed diver without being tethered to them.

    I'm not knocking the use of pony bottles and certainly recognize their incremental value over Spare Air. I also recognize that Michael is a local resident, as well as an experienced technical and rebreather diver. If I met the same criteria I'd probably carry a pony bottle on Bonaire too. But as a visiting recreational diver I disagree with the apparent claims above that the Spare Air doesn't provide enough air and/or is useless. It may not be enough for you, but it's fine for me. It might be fine for others too.

  6. #16
    trtippins is offline Bonaire Lover Bonaire Talker
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    Cool Thanks !!! Best written and most helpful article on the Spare Air blog Debate.

    Thanks...My Dive Master Instructor said it would be a good idea if I carried a Spare Air also. Nice job with the Thread
    Quote Originally Posted by wwguy View Post
    Interesting discussion. I've carried a Spare Air periodically in certain dive situations since my NAUI Course Director, a former special forces dive trainer, suggested it during my instructor training 19 years ago. I agree with Michael's observation that a Spare Air is an emergency solution only and that any time it's in your mouth you should be headed towards the surface. "Testing" it by breathing it until empty at depth doesn't accurately reflect its useful range for any particular diver.

    I'm curious what scenarios you pony bottle fans imagine might lead to running out of air at depth while diving on Bonaire at recreational depths? Most divers dive deepest during the early portion of the dive and much shallower on the return portion. Well-maintained modern scuba regulators and tank don't just spontaneously fail during a dive, and well-trained divers (especially those diving deep or solo) don't just forget to monitor their gas or depth. If you run out of gas and need to switch to a redundant bailout system at 80+' you've got other issues beyond just which bailout system to haul on vacation with you.

    I often carry a Spare Air when diving solo from shore on Bonaire. My typical solo dive profile is max depth of 70' to 80' early in the dive, with the return leg of the dive being no deeper than 45' and often much shallower. For the past 150 or so Bonaire dives my average bottom time varies from 70 to 75 minutes on an 80 cu ft tank and I always return to shore with 1000 to 1500 psi. My gas consumption rate is sufficient to safely get to the surface from 50' to 60' on 3 cu ft of gas if necessary.

    I can't imagine a scenario where I'd ever run out of gas period on a dive, much less during the deepest early portion of the dive where I have the most gas in my tank. But I still carry the Spare Air for peace of mind (mine and my wife's) as a preferable alternative to performing an emergency swimming ascent during an unexpected situation at any depth. At least once per trip, usually during one of the last dives, I practice ascending while breathing off of the Spare Air. It works just fine at normal ascent rates from the depths where I am during the latter half of my dives and would suffice as an emergency solution from deeper depths. While either would be bad , for me it's preferable to be bent and alive at the surface rather than drowned at depth. The Spare Air is an emergency contingency solution, not an alternate or supplement to my primary scuba unit.

    Unlike a pony bottle setup a Spare Air is relatively inexpensive, compact, lightweight, easy to travel with, easy to fill from a scuba tank, easy to carry, and easy to use. It's also easy to hand to another distressed diver without being tethered to them.

    I'm not knocking the use of pony bottles and certainly recognize their incremental value over Spare Air. I also recognize that Michael is a local resident, as well as an experienced technical and rebreather diver. If I met the same criteria I'd probably carry a pony bottle on Bonaire too. But as a visiting recreational diver I disagree with the apparent claims above that the Spare Air doesn't provide enough air and/or is useless. It may not be enough for you, but it's fine for me. It might be fine for others too.

  7. #17
    tholland is offline Bonaire Lover Bonaire Talker
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    Good points, thanks! I got interested in spare air after doing a dive in Cozumel and seeing another diver's tank blow a main o-ring.... all of their air was gone in seconds! Made me think 'what if that happened to me'? With spare air, at least you have quick access to an emergency air source for immediate ascent (again, like you, I spend the bulk of my dive in less than 50 feet while in Bonaire and have very lengthy shallow endings. The one time I almost ran completely out of air diving was when I was in the Maldives and got sucked down out and away from the main dive site by some really nasty currents. Almost didn't make it back from that dive.... there was no swimming up against that current! Just put some air in my vest and hoped the currents would eventually 'let go' of me. Just in the nick of time.... I was suddenly whirled head over heals and spun around at some nexus of those three currents (like being inside a washing machine!)...then they just 'let go'....and I safely ascended to the surface with just a few breaths left in the tank! Phew!

  8. #18
    tholland is offline Bonaire Lover Bonaire Talker
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    So now I have a spare air and plan to bring it through TSA in my carry on. I have the top valve off and ready for visual inspection...but how do I best 'clean out any dust' etc. that gets into the bottle when the TSA start handling it and looking inside it (taking the dust cap off to see inside)? Can I just not worry about it or maybe I need to blow some air in from a tank to 'blow the dust out' before putting the regulator/valve back on the top and prepare to fill it?
    Spare Air experts...any advice on this one?
    thanks!
    Anthony

  9. #19
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    Quote Originally Posted by tholland View Post
    So now I have a spare air and plan to bring it through TSA in my carry on. I have the top valve off and ready for visual inspection...but how do I best 'clean out any dust' etc. that gets into the bottle when the TSA start handling it and looking inside it (taking the dust cap off to see inside)? Can I just not worry about it or maybe I need to blow some air in from a tank to 'blow the dust out' before putting the regulator/valve back on the top and prepare to fill it?
    Spare Air experts...any advice on this one?
    thanks!
    Anthony
    Spare Air offers an optional Travel Pack for $20. They sent me one with some warranty parts a few years ago but I never use it because I get better use of space in my carry on by separating the parts into smaller packages.

    I separate the regulator from the cylinder before I pack it at home. The regulator goes into a sealed ziploc baggie to prevent dirt contamination. I place another baggie over the open end of the cylinder and fix in place with a rubber band. This prevents contamination, makes it easy to see the cylinder is open to atmospheric pressure, and easily permits closer inspection if desired.

    I also have a lifelong collection of soft purple velvet Crown Royal whisky bags with drawstrings that I use to prevent hard items from rubbing together in my carryon. I put them over masks, computers, consoles, regulator 1st & 2nd stages, and my Spare Air regulator. The Spare Air cylinder with baggie on top goes into the holster that came with it.

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