The CO 2 is injected into the mixture near the end of the barrel 4004 , 4004', after a seal 4006 , 4006' and just before the nozzle 4007 , 4007'.
A pumping mechanism 4009 , 4009' such as a stepping pump, which are widely used in the industry, is used to increase the pressure in barrel 4004 , 4004'.