An aerosol generator comprising: a mouthpiece having an outlet through which aerosol can be supplied to a user of the aerosol generator; an air passage through which air can be supplied to an interior of the mouthpiece; a sensor for detecting a pressure drop in the interior of the mouthpiece; and a housing, charaterised by comprising: a capillary passage disposed within the housing; a heater disposed within the housing; a reservoir disposed within the housing; a metering chamber disposed within the housing, wherein the metering chamber can be supplied fluid from the reservoir by a first flow passage and the capillary passage can be supplied fluid from the metering chamber by a second flow passage; a power source adapted to supply electrical power to the heater; a first valve adapted to open and close the first flow passage; a second valve adapted to open and close the second flow passage; a third valve adapted to open and close the air passage; and a motor and a camshaft, the camshaft including a plurality of camshaft lobes (132b,d,e) operatively associated with the first, second and third valves, the camshaft lobes being operable to close the first valve and open the second and third valves during an aerosol delivery cycle in which fluid is supplied to the capillary passage. a mouthpiece having an outlet through which aerosol can be supplied to a user of the aerosol generator; an air passage through which air can be supplied to an interior of the mouthpiece; a sensor for detecting a pressure drop in the interior of the mouthpiece; and a housing, charaterised by comprising: a capillary passage disposed within the housing; a heater disposed within the housing; a reservoir disposed within the housing; a metering chamber disposed within the housing, wherein the metering chamber can be supplied fluid from the reservoir by a first flow passage and the capillary passage can be supplied fluid from the metering chamber by a second flow passage; a power source adapted to supply electrical power to the heater; a first valve adapted to open and close the first flow passage; a second valve adapted to open and close the second flow passage; a third valve adapted to open and close the air passage; and a motor and a camshaft, the camshaft including a plurality of camshaft lobes (132b,d,e) operatively associated with the first, second and third valves, the camshaft lobes being operable to close the first valve and open the second and third valves during an aerosol delivery cycle in which fluid is supplied to the capillary passage. a capillary passage disposed within the housing; a heater disposed within the housing; a reservoir disposed within the housing; a metering chamber disposed within the housing, wherein the metering chamber can be supplied fluid from the reservoir by a first flow passage and the capillary passage can be supplied fluid from the metering chamber by a second flow passage; a power source adapted to supply electrical power to the heater; a first valve adapted to open and close the first flow passage; a second valve adapted to open and close the second flow passage; a third valve adapted to open and close the air passage; and a motor and a camshaft, the camshaft including a plurality of camshaft lobes (132b,d,e) operatively associated with the first, second and third valves, the camshaft lobes being operable to close the first valve and open the second and third valves during an aerosol delivery cycle in which fluid is supplied to the capillary passage.