Testing a Spare Air

[johndiver999]

Hi Johndiver999,

I like your response better than mine!

You wrote: "If needed, I can use my BC and fins to ascend a lot faster than I can swim horizontally in a pool in a bathing suit, but that is not my planned solution to a potential out of air emergency."

How will you use your BCD in an OOA situation without a pony? Even with a pony, you will need to manually inflate your BC.

Did I miss something? I think you mean ascending with no pony faster than you can swim horizontally by using your BC.

What is your planned solution to OOA?

thanks,
markm

My line of thinking is as follows: I could get from 100 feet to the surface with 3 cu-ft. I could/might need to swim up fast and/or use air in the BC to get there fast enough to allow the 3 cu-ft to be sufficient to prevent me from inhaling water. However, this is too little air for MY comfort level. 3 cu-ft might require an ascent that is too fast for ME. Obviously it is better than nothing.

My primary point was to encourage people to specifically plan the ascent and specify all the relevant parameters (which was exactly what a subsequent person did). Once you make those assumptions and do the math, then we have an objective means to discuss what is "enough" reserve air.

We can still have a lot of fun disagreeing over the assumptions themselves, but at least we are making objective comparisons rather than talking about "fitness levels" and the ability to swim fast or some other parameters that are somewhat nebulous. For example, even a very "fit" person who is out of breath (or panicked) is going to need a lot of air to make a 100 ft ascent.

And another relevant point is that in a true emergency, if a diver KNOWS he has adequate redundant capacity, he is going to be a lot calmer and probably use less air than a diver who has taken a gamble with a tiny spare air and knows immediately that this ascent needs to be fast and perfect or there will be nothing to breath. Which of those two theoretical divers is more likely to ascend at a safe rate?

I think it is great that the OP is testing his equipment and is demonstrating what will actually work for him. I bet this knowledge would be hugely beneficial in a true emergency.

 

[scubadada]

It's a personal decision, have more than enough gas, just enough gas, or no gas. The calculations are certainly very simple

 

[Jiminy]

I was recently at my LDS enquiring about a pony bottle, explaining that I was planning to do more buddy-less diving to have time for leisurely photography. They suggested trying a Spare Air instead. To be clear, this is as a safety backstop for recreational dives no deeper that 20 m, and well within NDL. I have read the many negative comments on this forum about Spare Airs, and particularly the calculations showing that they would be useless in case one really runs out of air during a dive.
So I decided to actually see what happens when breathing from a Spare Air. No one would mistake this for even a cheapo reg, it takes some effort to suck air out of it, but it works. First test was at 4 m depth, finning vigorously to get back to my entry point. The air lasted for a little over 4 min, which my buddy found surprising given the small size of the bottle. Second test was switching air sources at 22 m depth and performing a standard ascent at about 10 m/min. Easily made it to 3.5 m depth (took 2 min), and had enough air left for about 1 min safety stop. I could have done a CESA from there if needed.
So from my POV this thing does what I expected it to do. If I should have an equipment failure or an OOA at 20 m or less, I can make it to the surface unharmed. I agree that if I should be panicking it may not last as long, but with >1000 dives under my belt I don't see this as a very likely scenario. I can clip it to by BCD where it is out of the way but easily grabbed, and under most OOA scenarios at <20 m depth it will allow me to get back to the surface. I hope that this will not trigger a flame war, thought I would share the experience.

This thread is very interesting. One question keeps coming to mind i see you mention OOA several times. What is your main concern, OOA or equipment failure?

Ive read lots of stories of photogs getting distracted and forgetting to check their spg

 

[scubadada]

This thread is very interesting. One question keeps coming to mind i see you mention OOA several times. What is your main concern, OOA or equipment failure?

Ive read lots of stories of photogs getting distracted and forgetting to check their spg

Sorry, but you should never run out of gas, my assumption is equipment failure. Even then, even with a low pressure hose loss, you should have some gas available, at least to start your ascent.

 

[markmud]

This thread is very interesting. One question keeps coming to mind i see you mention OOA several times. What is your main concern, OOA or equipment failure?

Ive read lots of stories of photogs getting distracted and forgetting to check their spg

Hi Jimmy,

I hope you don't mind me butting-in and answering your question.

I know a photographer who dives with a 13cf pony. She tells you, when asked, that she has been so enthralled with taking pictures that she has sucked her primary dry. She is a great diver--she is a British Columbia diver. A real diver, unlike me-- a California diver.

My instructor tells a story that he witnessed. A photographer had a habit of running out of gas. So he fixed the problem by packing a pony. He ran out of gas, switched to his pony, and tried kicking his way to the surface. He was negative. He did not let go of his beloved camera nor did he manually inflate his BCD. My instructor got there in time to recover the body. My instructor broke the camera free of the diver's death grip and got his corpse to the surface. Rick is no bull-sheet artist--I believe him.

Personally, I have never witnessed such events.

markm

 

[Coztick]

My instructor tells a story that he witnessed. A photographer had a habit of running out of gas. So he fixed the problem by packing a pony. He ran out of gas, switched to his pony, and tried kicking his way to the surface. He was negative. He did not let go of his beloved camera nor did he manually inflate his BCD. My instructor got there in time to recover the body. My instructor broke the camera free of the diver's death grip and got his corpse to the surface

On my last trip, I decided to manually inflate on every dive. Something I wasn't practicing until then and a necessary skill if packing a pony or independent doubles.

 

[Jiminy]

Sorry, but you should never run out of gas, my assumption is equipment failure. Even then, even with a low pressure hose loss, you should have some gas available, at least to start your ascent.

I certainly agree with you about running out of gas but the OP does mention OOA twice and the DAN reports are full of people OOA. Behind medical issues its the number 2 cause of scuba accidents. I hope he is disciplined and manages his air well and always surfaces with some in reserve. But I dont know that he is disciplined all I know is he is human and can have a bad day and screw up.

The really interesting thing is this conversation is not really about spare air its about mitigating risk. OP is diving alone photographing and recognizes he is taking additional risk.

Spare air is a way to mitigate that risk but is it a good way?

Are there better ways for this diver to mitigate the risk of diving alone and being distracted? Yes i think so

 

[markmud]

On my last trip, I decided to manually inflate on every dive. Something I wasn't practicing until then and a necessary skill if packing a pony or independent doubles.

And I bet it is second nature after practicing. Yes, no?
markm

 

[scubadada]

There is no good excuse for running out of gas, maybe entanglement if you don't have the right cutting tools, also, not a good excuse, Trilobyte and a good titanium knife.

 

[JackD342]

My instructor tells a story that he witnessed. A photographer had a habit of running out of gas. So he fixed the problem by packing a pony. He ran out of gas, switched to his pony, and tried kicking his way to the surface. He was negative. He did not let go of his beloved camera nor did he manually inflate his BCD. My instructor got there in time to recover the body. My instructor broke the camera free of the diver's death grip and got his corpse to the surface. Rick is no bull-sheet artist--I believe him.

Overly focused UW photographers are my number one example of why a recreational/vacation diver would want to consider taking a Self Reliant (Solo) Diver course, and adding a fully redundant air supply.