If you’ve been playing paintball for long time then you ‘re quite familiar with CO2 Tanks as mostly Paintball Guns are operated with Compressed Air or CO2. In fact, Carbon Dioxide or CO2 is fairly responsible for the velocity required for the shooting.
The force behind the paintballs comes from the Paintball Tank. Your gun starts losing pressure whenever the air-tank runs out of CO2 and you need to re-fill your Air Tank to maintain the shooting power of your marker.
Basically, CO2 used in the paintball tank is in compressed liquid form and you always need appropriate equipment and tools to your Paintball Tanks. For sure, the key of filling the paintball tank is through larger tanks.
Infographic Source: https://paintballgod.com/co2-filling-in-tanks-paintball-guns/