CO2 Tank Weights

[John Marker]

The weight, volume, and space occupied is a static function across all gases - it's the noble gas law.

They sell you 20 oz of CO2 by weight and the volume and pressure are dictated by the size of the container it's in, which doesn't matter to me.


What I'm actually asking here is if people actually sell you 20 oz when they fill a tank and if they do, does the CO2 tank function to release gas for the entire 20 oz or does it fizzle out before the 20 oz mark.

Yes, if they fill the tank correctly, they are selling you 20oz of CO2. There are some shops out there that short fill them and tell their customers that they need to do that to allow for expansion, but that is a load of crap. The tanks are built to hold the amount of CO2 that is specified on the label and stamped into the neck of the tank.

When the tank is full and at normal room temperatures, the CO2 that is in the tank should be about 80% liquid and 20% gas. As the tank is emptied, the amount of liquid CO2 decreases as the liquid converts into a gas to maintain the pressure in the tank, which should be around 600-700 psi. When enough CO2 has been used that there is no longer liquid CO2 in the tank, the pressure will very rapidly drop and the tank is basically empty, although there is still CO2 in the tank but it is no longer pressurized enough to propel it out of he tank and not the atmosphere.

You will not be able to utilize all 20oz, but it should be close, I would think 19oz or so realized from a fill, especially for euthanizing rodents. In paintball you can bet on losing a few ounces of CO2 from each tank because of the lack of pressure when the CO2 levels become low, but you shouldn't have this problem when not trying to pressurize a paintball marker.

Hope this helps,

John