Paintball tanks provide the pressure source to power a paintball marker (gun). There are two primary types of gas used: Carbon Dioxide (CO2) and compressed air. In the case of CO2 when Carbon Dioxide turns from a liquid state into a gas it expands and creates pressure. This pressure is what fires the paintball. Compressed air tanks are pressurized up to the tank’s rating of 3000 PSI or 4500 PSI (Pounds per Square Inch). The pressure is then regulated through the tank’s regulator down to a lower PSI (450-850) to fire the paintball.