Codyjp
Contributor
It seems that the general rule for recreational diving is to return to the surface with no less than 500psi remaining in your tank. Now, here is my question. If you are diving with a low pressure tank at 500psi you are returning with a whole lot more air then if you are returning with 500psi in a HP tank.
Examples: All considering 80cf tanks
@2640 500psi=19% air remaining
@ 3000psi 500psi=16.6% air remaining
@ 3442 500psi=14.5% air remaining -- oops, that’s about 25% less than on a LP tank!
Now, assuming a dive with a 3442 tank you were able to dive for 40 minutes until you are down to 500psi. With that 500psi remaining you will be able to continue diving for another 6.8 minutes under the same conditions. 6.8-3 minutes for deco stop leaves you with 3.8 minutes to dive. Better not have any problems!
With a 2640psi tank with the same scenario you would be left with 9.3 minutes or 6.3 after the deco stop. Nearly double the time from the above scenario.
Another factor that will be of benefit to you is that as you ascend you will use air at a slower rate, but that is too difficult for me to calculate!
So my question is; wouldn’t a diver be safer if he/she were to calculate their surfacing pressure as a percentage of their total air available? There are many other factors that will affect this as well (that should satisfy the cave/tech/deep divers). I understand that the cave diver standard is 1/3 of your pressure remaining when back at the surface. Maybe the rec diver should consider something similar to this? When diving a reef at 30’ maybe 33% of your air remaining is a bit excessive, but under many circumstances 500psi is not an acceptable rule of thumb either!
What do you think?
Examples: All considering 80cf tanks
@2640 500psi=19% air remaining
@ 3000psi 500psi=16.6% air remaining
@ 3442 500psi=14.5% air remaining -- oops, that’s about 25% less than on a LP tank!
Now, assuming a dive with a 3442 tank you were able to dive for 40 minutes until you are down to 500psi. With that 500psi remaining you will be able to continue diving for another 6.8 minutes under the same conditions. 6.8-3 minutes for deco stop leaves you with 3.8 minutes to dive. Better not have any problems!
With a 2640psi tank with the same scenario you would be left with 9.3 minutes or 6.3 after the deco stop. Nearly double the time from the above scenario.
Another factor that will be of benefit to you is that as you ascend you will use air at a slower rate, but that is too difficult for me to calculate!
So my question is; wouldn’t a diver be safer if he/she were to calculate their surfacing pressure as a percentage of their total air available? There are many other factors that will affect this as well (that should satisfy the cave/tech/deep divers). I understand that the cave diver standard is 1/3 of your pressure remaining when back at the surface. Maybe the rec diver should consider something similar to this? When diving a reef at 30’ maybe 33% of your air remaining is a bit excessive, but under many circumstances 500psi is not an acceptable rule of thumb either!
What do you think?