Abstract: A method for the preparation of pharmaceutical products is provided that utilizes a machine having a containing liner, a dosing chamber for preparing at least one pharmaceutical product accommodated within the containing liner, and a pneumatic ventilation device for feeding two air flows through the dosing chamber and through the containing liner, respectively. Operation of the pneumatic ventilation device is selectively controlled so that the containing liner has inside a pressure lower than a pressure existing within the dosing chamber and than a pressure existing in the environment outside the containing liner itself.