To properly fill a CO2 tank, first you need to make sure you have specialized fitting & other equipment compared to Compressed Air, which is a one-time install of the tanks, fittings and compressor. In addition to that, you need a trained employee who can fill a CO2 tank safely. This consists of draining any old CO2 still in the tank, then slowly filling a tank to the proper weight, and re-draining the lines to prevent any freezing. Of course, you have to tank the tank off the marker first too – another time consuming endeavor if there is still residual pressure in the tank or t he threads become damaged. This process can take a few minutes from start to finish. Doesn’t sound like much, but then imagine having to do 100 fills for players…several times a day!