Dangers of Overfilling CO2 Paintball Cylinders

Overfilling a CO₂ cylinder, be it an attempt to get longer service out of one charge of a cylinder or be it accidental,  can have unexpected and even catastrophic consequences due to the expansion characteristics of the CO₂ charge.

We at Catalina Cylinders have heard  many times that it is not fair that a CO₂ cylinder is deemed full at only 68%  of its water capacity, that there appears to be 32% of its water capacity that is not being used,  or wasted, and that this capacity not being used could be used for extended service life  of one CO₂ charge. This 32% is not spare, or wasted, capacity. Following are three  situations that identify why this 32% of the total water capacity of a CO₂ cylinder is not spare, or wasted, capacity.

1. A 20-ounce CO₂ paintball cylinder with a full charge (68% of its water capacity) When a fully charged, 68% full by water capacity, 20-ounce CO₂ cylinder warms up to room temperature (70 ^oF), the pressure  inside the cylinder is 837 psi. When the cylinder reaches 87.9 ^oF the entire  charge becomes a gas no matter what the pressure. A fully charged CO₂ cylinder at 87.9 ^oF will have an internal  pressure of approximately 1100 psi. At 120 ^oF a fully charged CO₂ cylinder will have an internal pressure of nearly 2000 psi, this is greater  than the designed service pressure of 1800 psi of the cylinder. Remember that this cylinder  at 120 ^oF has an internal pressure greater than the marked service pressure  of the cylinder and is properly filled, not overfilled. Also note that 120 ^oF is not an excess  temperature and can quite easily  be reached in many different environments (i.e. in a shed or a vehicle on a hot day or in a kitchen).
2. A 20-ounce CO₂ paintball cylinder with a 5-ounce overfill (85% of its water capacity)
   The following would occur if a 20-ounce CO₂ cylinder were slightly overfilled with 25 ounces of CO₂ charge to increase its service life between fills.  When the cylinder and charge warm to room temperature the internal pressure  of the cylinder would be 1430 psi. If the cylinder were warmed to 103 ^oF  the cylinder would vent through the safety device of the valve. This venting would most likely  be unexpected since it would not be known when the cylinder would warm to 103 ^oF.  Unexpected venting through the safety device of a valve has caused property damage and personal injury.
3. A 20-ounce CO₂ paintball cylinder greatly overfilled (95% of its water capacity)
   A 20-ounce CO₂ cylinder filled to 95% of it’s capacity,  not quite liquid full would vent through its safety prior to the cylinder reaching room temperature,  70 ^oF. If the safety disc has been altered and reinforced and would  not actuate, the cylinder would rupture between 85 ^o – 95 ^oF. Rupturing cylinders  have caused  severe property damage and serious personal injury, even loss of life.

Accidental overfilling or  overfilling due to inaccurate equipment (i.e. the scale being used in the filling process not being  calibrated or not being able to measure in small enough units of measure to accurately fill  small cylinders) will have the same results as purposely overfilling a cylinder. The affects of accidental overfilling of a small CO₂ cylinder can have catastrophic affects as described below.

A 7-ounce CO₂ paintball cylinder filled accidentally with 2.8 extra ounces of CO₂ will be filled to 95% of its capacity. As stated above, a cylinder  filled to 95% of its water capacity would vent through its safety device before the cylinder warms to room temperature.

In summary, never overfill a CO₂ cylinder, on purpose or accidentally. The affects  of overfilling coupled with the affects of increasing temperature on the CO₂ charge, will greatly increase the probability  that something catastrophic could happen to property or personnel. Do not take the risk, do not overfill a CO₂ cylinder.