There is provided an aerosol generating system (101) for heating an aerosol-forming substrate. The aerosol generating system comprises an aerosol generating device (105) and a cartridge (103). The aerosol generating system comprises a vaporizer for heating the aerosol- forming substrate to form an aerosol, at least one air inlet (123) and at least one air outlet (125). The air inlet (123) and the air outlet (125) are arranged so as to define an air flow route between the air inlet and the air outlet. The aerosol generating system further comprises flow control means for adjusting the size of the at least one air inlet (123), so as to control the air flow speed in the air flow route.
