A machine for the preparation of pharmaceutical products has a containing liner (27), a dosing chamber (2) for preparing at least one pharmaceutical product accommodated within the containing liner (27) and a pneumatic ventilation device (31) for feeding two air flows through the dosing chamber (2)- and through the containing liner (27), respectively； the operation of the pneumatic ventilation device (31) being selectively controlled so that the containing liner (27) has inside a pressure lower than a' pressure existing within the dosing chamber (2) and than a pressure existing in the environment outside the containing liner (27) itself.
