A cartridge assembly for use in an aerosol-generating system, the cartridge assembly comprising: a cartridge comprising: a first compartment having a first air inlet and a first air outlet; and a second compartment having a second air inlet and a second air outlet; a housing enclosing the cartridge, the housing comprising: an upstream housing end wall comprising a third air inlet and a fourth air inlet; and a downstream housing end wall comprising a third air outlet, a fourth air outlet, and at least one guide slot (26, 28); a mouthpiece comprising an upstream mouthpiece end wall and a mouthpiece air inlet in the upstream mouthpiece end wall, the mouthpiece air inlet in fluid communication with the third air outlet and the fourth air outlet; and at least one linkage extending through the at least one guide slot (26, 28) and connected to the cartridge and the upstream mouthpiece end wall; wherein the mouthpiece and the cartridge are rotatable with respect to the housing from a first position to a second position; wherein, when the cartridge is in the first position, the upstream housing end wall obstructs the first air inlet and the second air inlet, and the downstream housing end wall obstructs the first air outlet and the second air outlet; and wherein, when the cartridge is in the second position, the third air inlet is in fluid communication with the first air inlet, the third air outlet is in fluid communication with the first air outlet, the fourth air inlet is in fluid communication with the second air inlet, and the fourth air outlet is in fluid communication with the second air outlet. a cartridge comprising: a first compartment having a first air inlet and a first air outlet; and a second compartment having a second air inlet and a second air outlet; a first compartment having a first air inlet and a first air outlet; and a second compartment having a second air inlet and a second air outlet; a housing enclosing the cartridge, the housing comprising: an upstream housing end wall comprising a third air inlet and a fourth air inlet; and a downstream housing end wall comprising a third air outlet, a fourth air outlet, and at least one guide slot (26, 28); an upstream housing end wall comprising a third air inlet and a fourth air inlet; and a downstream housing end wall comprising a third air outlet, a fourth air outlet, and at least one guide slot (26, 28); a mouthpiece comprising an upstream mouthpiece end wall and a mouthpiece air inlet in the upstream mouthpiece end wall, the mouthpiece air inlet in fluid communication with the third air outlet and the fourth air outlet; and at least one linkage extending through the at least one guide slot (26, 28) and connected to the cartridge and the upstream mouthpiece end wall; wherein the mouthpiece and the cartridge are rotatable with respect to the housing from a first position to a second position; wherein, when the cartridge is in the first position, the upstream housing end wall obstructs the first air inlet and the second air inlet, and the downstream housing end wall obstructs the first air outlet and the second air outlet; and wherein, when the cartridge is in the second position, the third air inlet is in fluid communication with the first air inlet, the third air outlet is in fluid communication with the first air outlet, the fourth air inlet is in fluid communication with the second air inlet, and the fourth air outlet is in fluid communication with the second air outlet.