at a certain set pressure level p the pressure in buffer volume 80 p bv must always be at least equal to the set pressure i e p bv or gt p however to compensate for some pressure drop in the line leading from buffer volume 80 to application tool 100 the pressure in the buffer volume p bv cannot drop below a minimum required pressure p min which is greater than the pressure required by the application tool i e p bv or gt p min or gt p the average flow rate f avg of high pressure carbon dioxide feed stream 75 f i delivered to buffer volume 80 must be equal or higher than the average flow rate s avg of high pressure carbon dioxide supply stream 85 s i delivered to application tool 100 thus when f i is greater than s i the pressure in buffer volume 80 increases conversely when s i is greater than f i the pressure in buffer volume 80 will decrease accordingly over the course of the processing cycle when the flow rate to application tool 100 is greater than flow rate of high pressure carbon dioxide feed stream 75 the additional carbon dioxide required by application tool 100 must be delivered from the carbon dioxide stored in buffer volume 80 in accordance with the present invention applicants have found that properly sizing buffer volume 80 without replacing.