chrpai
Contributor
With proper dive planning you should never run out of gas. Especially with a tank that freaking big. 
So what you should be planning for is redundancy. The first question is do you really need redundancy? A proper buddy, team skills and gas planning means your buddy is your redundancy.
But let's say you are doing something like overhead or solo diving and you need redundancy. The h valve can be used for a second first stage regulator. You can then move your octopus over to it. If your primary first stage fails or free flows you switch to your octopus and shutdown the valve for your primary regulator to preserve gas.
Whatever solution you pick, practice drills with it. The gear won't save your life if you can't instinctively use it in an emergency.
This is a far more capable solution then a spare air and costs less to boot.
So what you should be planning for is redundancy. The first question is do you really need redundancy? A proper buddy, team skills and gas planning means your buddy is your redundancy.
But let's say you are doing something like overhead or solo diving and you need redundancy. The h valve can be used for a second first stage regulator. You can then move your octopus over to it. If your primary first stage fails or free flows you switch to your octopus and shutdown the valve for your primary regulator to preserve gas.
Whatever solution you pick, practice drills with it. The gear won't save your life if you can't instinctively use it in an emergency.
This is a far more capable solution then a spare air and costs less to boot.
