Paintball markers used in playing the sport of paintball operate with liquid CO2 or compressed air. Liquid CO2 turns into a compressed gas when it runs through a paintball marker. Compressed air tanks are filled with nitrogen, which is just another name for compressed air.
Fill liquid CO2 tanks by first releasing all the pressure out of the tank. Screw an adaptor onto the end of the tank and release the pressure until the tank is empty.
Look at the size tank you are going to refill. Tanks are filled in ounces. For an example, let's use a 24-oz. tank.
Close the valve that released the pressure on the 24-oz. tank. Now hang the tank on a digital scale and zero it out.
Open the valve on the big supply tank of liquid CO2 that you are refilling from. Watch the digital scale as your tank is refilling. When liquid is going into your tank, it gets cold and heavier. Do not exceed the 24-oz. scale mark on this tank.
Cut the pressure off of the big supply tank. Release the pressure off of the line and unscrew the refill tank. The tank is now full.
Refill a high-pressure tank by knowing what you are dealing with. These tanks have expiration dates on them. If the refill tank is out of date, you must get it re-tested for safety before you are allowed to refill it. The high-pressure supply tanks start at 3000 psi and go up to 5000 psi, according to the type of tank you purchase.
Proceed to refill a high-pressure tank by looking at the gauge on it. They can be filled without emptying. Find the nipple which attaches to your refill tank. This is a quick disconnect feature. Connect the supply tank to your refill tank. The refill tank has two gauges on it. One tells you the pressure on the tank and the other gauge is the regulator gauge, telling you how much pressure is going into your tank as you refill your air tank for paintball.