Let's consider a 10L tank full of air at a pressure of 200bar. That's 200x10=2000 litres. You'd need a BIG tank to hold 2000L. At depths we breath more air, so 2000-2400 is an average amount of air a diver would take down for an hour's recreational dive
It depends, using an average 12l tank (230 psi) if you are a heavy breather it will last for over an hour, and a light breather normally under 2 hours but you are recommended not to dive for over an hour
For your safety
The common Scott Air-Pak can vary from 10-14 lbs. for a tank with 30 minutes of air and made from carbon fiber. A tank with 60 minutes of air can weigh up to 17 lbs. and a tank made from Aluminum can weigh up to 22 lbs.
When an empty tank is filled with air, the air molecules move into the tank and exert pressure on the walls of the tank. This increases the air pressure inside the tank and causes the tank to become pressurized.
In general an air compressor is made up of three parts. They are the air pump, the motor and the tank that holds the compressed air.
Bottom of the air tank. Used to drain the water in the bottom off the tank
Use an air compressor with an adapter fitting that will allow you to push air in through a spicket on the tank. I made an adapter with a water pressure tester gauge (that is made to attach to a water (hose) spicket.) I then took off the gauge and installed a quick connect air fitting (standard on air equipment and air hoses).
Are you asking how do you swap and air tank on an air rifle, or swap for and air rifle? In most air rifles you put it on safe and swap out the tank by unscrewing it and replacing it.
What tank?
HPA tank stands for High Pressure Air and is a 3500 to 5000 psi canister for paintball made of steel or carbon fiber. It is an alternative to CO2 tanks, and is also called: Nitrogen tank, nitro or air tank.
You can use a scuba tank, but that is it.