Spare Air: some thoughts

[Thalassamania]

Because your actual air consumption changes with depth (even when your SAC stays constant), not your gas supply.

 

[Atomic_Diver]

Heck, I went diving once with a instructor/guide on the spiegel grove, and we where exploring the inside when all of a sudden he decides its time to exit, and upon surfaceing he had only 50psi left, when I had about 1100psi....

 

[Blackwood]

Because your actual air consumption changes with depth (even when your SAC stays constant), not your gas supply.

To elaborate: air is delivered at ambient pressure, so when you take one breath at 100 feet, 4 times more comes out than the same breath taken at the surface.

You may also notice a slight increase in gas supply due to an increase in temperature, but it will be very minimal.

 

[idocsteve]

Because your actual air consumption changes with depth (even when your SAC stays constant), not your gas supply.

Gotchya.

Thanks for explaining that, I learned something new today.

 

[idocsteve]

Heck, I went diving once with a instructor/guide on the spiegel grove, and we where exploring the inside when all of a sudden he decides its time to exit, and upon surfaceing he had only 50psi left, when I had about 1100psi....

Sounds to me like a waste of 1050 psi worth of perfectly good breathing gas.

 

[JimmyboyAAA]

Pretty amusing thread. My only Spare Air incident happened in Cozumel Aug 2008 when i was insta-buddied with Ivan. About 30 minutes into the dive Ivan turned to me and gave me the out of air signal and pulled out a Spare Air and left me floating at 60 feet with a truly dumb/shocked look on my face. Ivan clearly did not understand the purpose of the Spare Air.

 

[themagni]

To elaborate: air is delivered at ambient pressure, so when you take one breath at 100 feet, 4 times more comes out than the same breath taken at the surface.

You may also notice a slight increase in gas supply due to an increase in temperature, but it will be very minimal.

That's because the gas laws work in Kelvin, so a difference of 277 K (thermocline temperature) to 303 K (hot tropical day) is only a 9% change in temperature.

Oh boy, now I get this thread in my email.

 

[Atomic_Diver]

Pretty amusing thread. My only Spare Air incident happened in Cozumel Aug 2008 when i was insta-buddied with Ivan. About 30 minutes into the dive Ivan turned to me and gave me the out of air signal and pulled out a Spare Air and left me floating at 60 feet with a truly dumb/shocked look on my face. Ivan clearly did not understand the purpose of the Spare Air.

 

[ianr33]

So now the question becomes: how did you suck your cylinder down to 30PSI at 140feet?

My ex girlfriend could give you some suggestions

 

[idocsteve]

My ex girlfriend could give you some suggestions

As her buddy it was your responsibility to make sure she never got down that low.