The tank holds compressed gas, which is used to propel the paintballs through the marker barrel. The tank is usually filled with
carbon dioxide or compressed air. High Pressure Air (HPA) is also known as "nitrogen", as air is 78% nitrogen, or because these systems can be filled with industrial nitrogen. Due to the instabilities of carbon dioxide, HPA tanks are required for consistent velocity. Other propulsion methods include the combustion of small quantities of
propane or electromechanically operated
spring plunger combinations similar to that used in an
airsoft gun.
Carbon dioxide Carbon dioxide (CO2) is a propellant used in paintball, especially in inexpensive markers. It is usually available in a 12 gram
powerlet, mainly used in stock paintball and in paintball pistols, or a tank. The capacity of a carbon dioxide tank is measured in ounces of liquid and it is filled with liquid CO2, at room temperatures the vapour pressure is about . The CO2 liquid must vaporize into a gas before it can be used. This causes problems such as inconsistent velocity. Cold weather can cause problems with this system, reducing the vapour pressure and increasing the chance for liquefied gas to be drawn into the marker. The low-temperature liquid can damage the internal mechanisms. Anti-siphon tanks have a tube inside the cylinder, which is bent to prevent liquid carbon dioxide from being drawn into the gun. On the other hand, a number of paintguns were designed with specific valves to operate on liquid CO2, including some early
Tippmann models and the Mega-Z from Montneel – thus solving the problem caused by phase changes. Siphon equipped CO2 tanks are easily identified by the clunking sound their weight makes when the tank is tipped. After many years of use,
Carbon dioxide has almost been universally replaced with High Pressure Air systems (see below)
High-pressure air High-pressure air, compressed air or
nitrogen, is stored in the tank at a very high pressure, typically . Output is controlled with an attached regulator, regulating the pressure between and , depending on the type of tank. The advantage of using regulated HPA over carbon dioxide (CO2) is pressure consistency and temperature stability where CO2 reacts to temperature changes causing inaccuracy and freezing during heavy use. The most popular tank size is at providing 800–1100 shots. HPA tanks are more expensive because they must accommodate very high pressures. They are manufactured as steel, aluminium or wrapped
carbon fiber tanks, the latter being the most expensive and most lightweight. Most players with electronic markers use HPA because if CO2 is used, the marker's electronic
Solenoid valve can be damaged if liquid CO2 enters it. Users are warned not put any type of lubricant in the 'fill nipple' port of a HPA tank, as petroleum may burn when subjected to highly compressed air, causing an explosion, like in a
diesel engine.
Propane A far less common propellant is
propane, featured only in the
Tippmann C3. Rather than simply releasing gas as in high-pressure air and CO2 markers, the propane is ignited in a combustion chamber, increasing pressure and opening a valve that lets the expanding gas propel the paintball. There are a number of advantages, mainly shots per tank, ranging from 30,000 to 50,000 shots (depending on the size of the tank) as opposed to the typical 1000 to 2000 shots that are standard with High Pressure Air or CO2 tanks. Another advantage includes availability, as propane is readily available in many stores, whereas CO2 and High Pressure Air are most commonly filled from compressors or pre-filled tanks, which are less common. It can also be considered safer too, because a typical high-pressure air tank holds air at , and a CO2 tank at , but propane is stored at . However, propane produces heat, which (when firing for an extended period at high rates of fire) can cause burns if improperly handled. It can also be a fire hazard: the Tippmann C3 releases small amounts of flames from the vents in the combustion chamber and out of the barrel when firing. If a marker develops a leak from improper maintenance, it could cause a fire.
Gas regulation Marker systems have a variety of regulator configurations, ranging from completely unregulated to high-end systems using four regulators, some with multiple stages. The regulator system affects both the accuracy and the firing velocity. Carbon dioxide regulators must also prevent liquid gas from entering the marker and expanding, causing a dangerous surge in velocity. Regulators used with carbon dioxide often sacrifice throughput and accuracy to ensure the marker operates safely. HPA-only regulators tend to have an extremely high throughput and are designed to ensure uniform pressure between shots to ensure marker accuracy at high rates of fire. Tournament markers usually are equipped with two regulators, and another on the tank, each with a specific function. The tank regulator decreases the pressure of air from to . A second regulator is used to further reduce this pressure to near the firing pressure. This reduction allows for greater consistency. The air is then supplied to a regulator on the marker body, where the final output pressure is selected. This can be between for entirely unregulated carbon dioxide markers to approximately for extremely low pressure markers. After the firing pressure is decided, tournament-oriented markers use another regulator to supply gas to a separate pneumatic system, to power any other functions, such as bolt movement. This is an extremely low volume, extremely low pressure regulator, usually under . ==Barrels==