A process and a metered dose inhaler, comprising: an air actuator comprising at least one inlet of liquefied gas (LG), at least one air outlet, at least one first LG-expanding volume and at least one second air-containing volume, the first and second volumes are effectively separated by means of a LG-blocking member; a container with an LG source; said container is in a fluid connection with said LG-expanding volume via the at least one LG inlet; The air actuator is facilitating a metered dose airflow by allowing the expansion of said LG in said at least one LG-expanding volume from its condensed liquid phase to its expanded gas phase. The expansion of said LG facilitates the compression of the air within said at least one air-containing volume, such that a metered dose LG-free air flow is inhalable via at least one air outlet.