A scent cartridge housing 10 comprising: a body 12 for receiving a scent cartridge comprising a plurality of housing apertures 16 for allowing air to flow 74 through the housing； a first actuation device 60 for controlling the movement of a scent cartridge 24 from a first position, where a plurality of cartridge apertures 28 are not aligned with the plurality of housing apertures 16, to a second position in which at least some of the plurality of cartridge apertures 28 are aligned with at least some of the housing apertures 16； a second actuation device 38 for returning the scent cartridge to the first position from the second position. Another independent claim is for a scent cartridge 24 comprising: a plurality of apertures 28 for allowing air to flow through the scent cartridge and engagement means for engaging with a scent cartridge housing 10 when the scent cartridge is located in the housing. Another independent claim is for a system comprising a scent cartridge housing 10 and a scent cartridge 24 used in a vehicle or vehicle system.
