Spare air or pony
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and then there is vital capacity.
sigh
I didn't breathe at all when it happened to me. Cause there was zip-o. I cursed instead of breathing. The curse words go off loudly in your head. And believe me, it was preceded with a "WHAT?" and a very stupid pause, where I struggled with how this had happened.
My guy who work on regs does say that they are junk and won't touch them.
hey..I bought one once at DEMA. There is no reason to be humiliated...it is a rite of passage. They are cute.
sigh
I didn't breathe at all when it happened to me. Cause there was zip-o. I cursed instead of breathing. The curse words go off loudly in your head. And believe me, it was preceded with a "WHAT?" and a very stupid pause, where I struggled with how this had happened.
My guy who work on regs does say that they are junk and won't touch them.
hey..I bought one once at DEMA. There is no reason to be humiliated...it is a rite of passage. They are cute.
Ah, thank you. Didnt know htat was all included in lung volume.
Well I would love to hear lol, so go for it.
The amount of air that you move in and out of your lungs while breathing normally is called TIDAL VOLUME. This amount of air provides enough oxygen for a person who is resting. It is possible to inhale and exhale more forcefully - the maximum amount of air moved in and out of the lungs is called the VITAL CAPACITY.
A good buzz!
And finaly, lung volume, the 6 litre figure is what would happen if you had full lungs then a steam roller drove over your chest making your lungs flat with no air, 6 liters is what would come out.
And finaly, lung volume, the 6 litre figure is what would happen if you had full lungs then a steam roller drove over your chest making your lungs flat with no air, 6 liters is what would come out.
Putting on my Nomex underware, I’m going to challenge many of the assumptions made in calculations here.
While total lung capacity can be in the neighborhood of 6 liters, I know very few people who can reach a vital capacity of 4.8 liters and according to my measurements over the past few months with friends, fellow divers, and students my vital capacity of 4.5 liters is higher than anyone else I’ve tested with my Voldyne inspiration exerciser. Most people are turning funny colors before they are able to inspire more than 3 to 3.5 liters. Typical predictive ranges run from a 58” tall 20 year old male at 2 liters to a 78” tall 20 year old male at 4 liters with it dropping considerably for females or older persons. Normal respiration is only about .5 liters per breath and I’ve calculated that a upping my respiration while diving to about 1 liter per breath with 11 to 12 breaths per minute yields a SAC of about .389 CFM, which is very close to the .42 to .45 CFM I typically see diving. Most people are shocked the first time they find out how big a breath 1 to 1.5 liters really is.
If we assume that typically the Spare Air only gets filled to 2750 psi and at 99’ we can’t use the last 100 psi, that leaves us with only 2.65 CF (75 liters) usable at depth and when adjusted to sea level equivalent that would be .66 CF (18.75 liters). That would translate into about 18 normal diving breaths or 30 normal surface type breaths or about 1 minute 20 seconds at depth, which converts back very close to the 5 minutes 30 seconds I got off a Spare Air at the surface last time I checked.
When a diver runs out of air at depth 2 things happen to compound the problem and increase their anxiety while looking for their buddy and comprehending what’s happened. The first is they are typically left with well under a normal lung fill of air, and if they’re a liter short of air in their lungs they’re caught 2.2 pounds heavier than normal with no way to get positively buoyant. Reality is that most vacation divers vary from 5’ to 15’ away from their buddies on dives, and with a normal vacation diver swim rate it will take 10 to 15 seconds for them to find and catch up with their buddy 15’ away after about 5 seconds to comprehend the problem. Deeply exhale and than don’t inhale for 20 seconds and you’ll see how quickly you start to feel CO2 buildup and how high your anxiety level goes. If a Spare Air only gives a diver 1 breath it’s enough to keep them neutrally buoyant and cut the amount of time they have to be out of air before they reach their buddy from 20 seconds or more to less than 10 seconds – which will greatly reduce the tendency to panic that can be the real killer in cases like this. It also reduces the stress of having to make a split second decision as to whether it is best to get to a buddy 20 seconds away or to make an OOA emergency ascent.
One complaint from many vacation divers is the weight of all the equipment they have to carry to the boat, walk to the water with, and climb back on the boat with and a Spare Air is typically 8-10 pounds lighter than even a 13CF pony and doesn’t require additional techniques for entry or exit from the water. The big complaint about Spare Air units in this thread is that they’re inadequate to make a solo ascent, but in the half dozen times I’ve seen them used over the years not one person made an ascent with it, but they did easily and calmly get to their buddy to ascend with them – and without the Spare Air they might have been forced to ascend without air on their own.
I won’t argue that a Spare Air is any substitute for an adequately sized pony bottle for the types of diving many people here do, but we’re doing a disservice to the larger diving community by claiming there is no useful purpose for them and that people are better off without one than using one for what meets their requirements – not the requirements of the minority of hardcore divers on this board. If our purpose here is to be elitist snobs that don’t want casual recreational vacation divers to participate in the sport than by all means we shouldn’t allow anyone to board a dive boat without a 40CF pony or doubles on a BP/W with an HID light. Otherwise we need to realize that there are plenty of competent divers that would find the sport losing much of it’s appeal if they had to lug a pony bottle around to feel comfortable (or accepted) – and for the application many use a Spare Air for it does add a significant safety margin for them.
http://en.wikipedia.org/wiki/Lung_volumes
While total lung capacity can be in the neighborhood of 6 liters, I know very few people who can reach a vital capacity of 4.8 liters and according to my measurements over the past few months with friends, fellow divers, and students my vital capacity of 4.5 liters is higher than anyone else I’ve tested with my Voldyne inspiration exerciser. Most people are turning funny colors before they are able to inspire more than 3 to 3.5 liters. Typical predictive ranges run from a 58” tall 20 year old male at 2 liters to a 78” tall 20 year old male at 4 liters with it dropping considerably for females or older persons. Normal respiration is only about .5 liters per breath and I’ve calculated that a upping my respiration while diving to about 1 liter per breath with 11 to 12 breaths per minute yields a SAC of about .389 CFM, which is very close to the .42 to .45 CFM I typically see diving. Most people are shocked the first time they find out how big a breath 1 to 1.5 liters really is.
If we assume that typically the Spare Air only gets filled to 2750 psi and at 99’ we can’t use the last 100 psi, that leaves us with only 2.65 CF (75 liters) usable at depth and when adjusted to sea level equivalent that would be .66 CF (18.75 liters). That would translate into about 18 normal diving breaths or 30 normal surface type breaths or about 1 minute 20 seconds at depth, which converts back very close to the 5 minutes 30 seconds I got off a Spare Air at the surface last time I checked.
When a diver runs out of air at depth 2 things happen to compound the problem and increase their anxiety while looking for their buddy and comprehending what’s happened. The first is they are typically left with well under a normal lung fill of air, and if they’re a liter short of air in their lungs they’re caught 2.2 pounds heavier than normal with no way to get positively buoyant. Reality is that most vacation divers vary from 5’ to 15’ away from their buddies on dives, and with a normal vacation diver swim rate it will take 10 to 15 seconds for them to find and catch up with their buddy 15’ away after about 5 seconds to comprehend the problem. Deeply exhale and than don’t inhale for 20 seconds and you’ll see how quickly you start to feel CO2 buildup and how high your anxiety level goes. If a Spare Air only gives a diver 1 breath it’s enough to keep them neutrally buoyant and cut the amount of time they have to be out of air before they reach their buddy from 20 seconds or more to less than 10 seconds – which will greatly reduce the tendency to panic that can be the real killer in cases like this. It also reduces the stress of having to make a split second decision as to whether it is best to get to a buddy 20 seconds away or to make an OOA emergency ascent.
One complaint from many vacation divers is the weight of all the equipment they have to carry to the boat, walk to the water with, and climb back on the boat with and a Spare Air is typically 8-10 pounds lighter than even a 13CF pony and doesn’t require additional techniques for entry or exit from the water. The big complaint about Spare Air units in this thread is that they’re inadequate to make a solo ascent, but in the half dozen times I’ve seen them used over the years not one person made an ascent with it, but they did easily and calmly get to their buddy to ascend with them – and without the Spare Air they might have been forced to ascend without air on their own.
I won’t argue that a Spare Air is any substitute for an adequately sized pony bottle for the types of diving many people here do, but we’re doing a disservice to the larger diving community by claiming there is no useful purpose for them and that people are better off without one than using one for what meets their requirements – not the requirements of the minority of hardcore divers on this board. If our purpose here is to be elitist snobs that don’t want casual recreational vacation divers to participate in the sport than by all means we shouldn’t allow anyone to board a dive boat without a 40CF pony or doubles on a BP/W with an HID light. Otherwise we need to realize that there are plenty of competent divers that would find the sport losing much of it’s appeal if they had to lug a pony bottle around to feel comfortable (or accepted) – and for the application many use a Spare Air for it does add a significant safety margin for them.
http://en.wikipedia.org/wiki/Lung_volumes
I may be too late in posting this, but here are some personal experiences with pony bottles (and btw, I have three of them and rarely dive without one.) My first choice is my 13 cf pony, but I also like my 20 cf pony bottle for deep dives. If you do the math we've all been taught it helps in understanding all this. Remember, compared to breathing out of a tank at the surface we get half as many breaths at 33 ft, and a third as many at 66 ft.
I have tested my 13 cf pony bottle from 60 fsw, and it was very easy not only to breath off of it while making a slow ascent (probably 30ft per minute) to a depth of 15 feet, but also to perform a 3 minute safety stop there. After surfacing I actually had air to spare! I tested the same ascent and safety stop from 100 fsw, using my 20 cf pony bottle, again with air to spare. There would be variations in this according to a diver's stress level, physical makeup and diving environment, but when used under calm conditions these were my personal results.
I have a 30 cf pony bottle I use for topping off the tires on three vehicles here at home, and I've been working off one air fill for nearly two years now!
Pony bottles are great! They only add a little more weight and bulk, but I feel they are well worth the added safety margin they offer.
I have tested my 13 cf pony bottle from 60 fsw, and it was very easy not only to breath off of it while making a slow ascent (probably 30ft per minute) to a depth of 15 feet, but also to perform a 3 minute safety stop there. After surfacing I actually had air to spare! I tested the same ascent and safety stop from 100 fsw, using my 20 cf pony bottle, again with air to spare. There would be variations in this according to a diver's stress level, physical makeup and diving environment, but when used under calm conditions these were my personal results.
I have a 30 cf pony bottle I use for topping off the tires on three vehicles here at home, and I've been working off one air fill for nearly two years now!
Pony bottles are great! They only add a little more weight and bulk, but I feel they are well worth the added safety margin they offer.
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