A cartridge assembly (2, 200) for use in an aerosol-generating system, the cartridge assembly (2, 200) comprising: a cartridge having an upstream end and a downstream end, the cartridge comprising: at least one compartment (12, 14) having an air inlet at the upstream end of the cartridge and an air outlet downstream of the air inlet; a removable first seal secured to the upstream end of the cartridge, wherein the removable first seal obstructs the air inlet of the at least one compartment (12, 14) and is configured to be removed by a user prior to use of the cartridge assembly (2, 200); and a cartridge actuation portion on an inner surface of a downstream end portion of the cartridge; a mouthpiece comprising: a mouthpiece body portion having an upstream end and a downstream end, the mouthpiece body portion having an air inlet at the upstream end of the mouthpiece body portion and an air outlet at the downstream end of the mouthpiece body portion; a second seal at the upstream end of the mouthpiece body portion; and a mouthpiece actuation portion on an outer surface of the mouthpiece body portion, wherein the mouthpiece actuation portion is engaged with the cartridge actuation portion and wherein the mouthpiece actuation portion and the cartridge actuation portion are configured so that the mouthpiece body portion is moveable with respect to the cartridge from a first position, in which first position the second seal abuts and obstructs the air outlet of the at least one compartment (12, 14), to a second position, in which second position the second seal is spaced apart from the air outlet of the at least one compartment (12, 14) and the air outlet of the at least one compartment (12, 14) is in fluid communication with the air inlet of the mouthpiece body portion. a cartridge having an upstream end and a downstream end, the cartridge comprising: at least one compartment (12, 14) having an air inlet at the upstream end of the cartridge and an air outlet downstream of the air inlet; a removable first seal secured to the upstream end of the cartridge, wherein the removable first seal obstructs the air inlet of the at least one compartment (12, 14) and is configured to be removed by a user prior to use of the cartridge assembly (2, 200); and a cartridge actuation portion on an inner surface of a downstream end portion of the cartridge; at least one compartment (12, 14) having an air inlet at the upstream end of the cartridge and an air outlet downstream of the air inlet; a removable first seal secured to the upstream end of the cartridge, wherein the removable first seal obstructs the air inlet of the at least one compartment (12, 14) and is configured to be removed by a user prior to use of the cartridge assembly (2, 200); and a cartridge actuation portion on an inner surface of a downstream end portion of the cartridge; a mouthpiece comprising: a mouthpiece body portion having an upstream end and a downstream end, the mouthpiece body portion having an air inlet at the upstream end of the mouthpiece body portion and an air outlet at the downstream end of the mouthpiece body portion; a second seal at the upstream end of the mouthpiece body portion; and a mouthpiece actuation portion on an outer surface of the mouthpiece body portion, a mouthpiece body portion having an upstream end and a downstream end, the mouthpiece body portion having an air inlet at the upstream end of the mouthpiece body portion and an air outlet at the downstream end of the mouthpiece body portion; a second seal at the upstream end of the mouthpiece body portion; and a mouthpiece actuation portion on an outer surface of the mouthpiece body portion, wherein the mouthpiece actuation portion is engaged with the cartridge actuation portion and wherein the mouthpiece actuation portion and the cartridge actuation portion are configured so that the mouthpiece body portion is moveable with respect to the cartridge from a first position, in which first position the second seal abuts and obstructs the air outlet of the at least one compartment (12, 14), to a second position, in which second position the second seal is spaced apart from the air outlet of the at least one compartment (12, 14) and the air outlet of the at least one compartment (12, 14) is in fluid communication with the air inlet of the mouthpiece body portion.