4.4 Paintball: What's the difference between C02, Nitrogen, and HPA?
Description
This article is from the Paintball FAQ, by Paul "Stryder" Kloehn pkloehn@frymulti.com.
4.4 Paintball: What's the difference between C02, Nitrogen, and HPA?
There are two main power sources used to propel a paintball out of a
paintball gun - Carbon Dioxide (CO2) and Nitrogen/High Pressure Air
(N2/HPA). Both are very common and each has its pros and cons.
Carbon Dioxide, more commonly know as CO2, is the most commonly used
propellant due mainly to the fact it is fairly inexpensive and has been
around since the beginning of the sport. Its main disadvantage is its
sensitivity to temperature. As a CO2 tank warms up or cools down the
available pressure either rises or falls. For a paint gun, differences
in pressure mean inconsistent velocities.
This sensitivity to temperature is due to the fact that CO2 is stored as
a liquid. The gaseous form of CO2 used by the paint gun is formed when
some it "boils off". The tank containing the gas is a fixed volume.
Since there is a direct relationship between temperature and pressure,
an increase in temperature causes a corresponding increase in pressure:
The pressure increases because no more liquid can turn into a gas and a
higher velocity results.
CO2 can also enter the gun in its liquid state under certain conditions
like sustained rapid firing. On some guns, the sub-zero temperature of
the liquid CO2 causes O-rings and air seals to freeze which disrupts
normal operation. Equipment such as expansion chambers, anti-siphon
tanks, and remotes help negate this effect.
Nitrogen and High Pressure Air systems, commonly called Nitro and HPA,
are the most prevalent alternatives to CO2. While any inert gas (like
Argon) will work, Nitrogen and HPA are the cheapest and most readily
available. Since Nitrogen and HPA are stored in their natural gaseous
state and not liquid, they are not susceptible to the thermal problems
described above. A Nitrogen/HPA equipped paintball gun will perform
consistently regardless of temperature and weather conditions.
Nitrogen/HPA has almost completely eliminated velocity fluctuations. The
only drawback is that Nitrogen systems costs more and some fields do not
have the capability to refill the tanks.
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