A stable-foam inhalation device for dispensing a stable foam to be inhaled by a user, the inhalation device comprising a carrier (72; 272) and a cartridge: wherein the cartridge comprises: a foam-generating-component receiving portion; stable-foam-generating components (26, 28) for generating the stable foam, said components (26, 28) received at or in the component receiving portion, at least one of said components being segregated from another of said components by an openable barrier; and a cartridge outlet for dispensing the stable foam; a cartridge conduit which fluidly communicates the foam-generating-component receiving portion with the cartridge outlet so that when the barrier is opened the components (26, 28) interact to generate the stable foam which flows to the cartridge outlet via the cartridge conduit; and wherein the carrier comprises: a carrier body (76; 276); a receiving portion (78; 278) for receiving the cartridge at or in the carrier body (76; 276); a carrier inlet (80; 280) for fluid communication with the outlet of the cartridge when the carrier (72; 272) is received in or at the receiving portion (78; 278); a carrier outlet (82; 282) for dispensing a stable foam to a user; a carrier conduit between the carrier inlet (80; 280) and the carrier outlet (82; 282) through the carrier body (76; 276); and a one-way valve in the carrier conduit for permitting movement of foam from the carrier inlet (80; 280) to the carrier outlet (82; 282) and preventing or limiting movement of fluid from the carrier outlet (82; 282) to the carrier inlet (80; 280). wherein the cartridge comprises: a foam-generating-component receiving portion; stable-foam-generating components (26, 28) for generating the stable foam, said components (26, 28) received at or in the component receiving portion, at least one of said components being segregated from another of said components by an openable barrier; and a cartridge outlet for dispensing the stable foam; a cartridge conduit which fluidly communicates the foam-generating-component receiving portion with the cartridge outlet so that when the barrier is opened the components (26, 28) interact to generate the stable foam which flows to the cartridge outlet via the cartridge conduit; a foam-generating-component receiving portion; stable-foam-generating components (26, 28) for generating the stable foam, said components (26, 28) received at or in the component receiving portion, at least one of said components being segregated from another of said components by an openable barrier; and a cartridge outlet for dispensing the stable foam; a cartridge conduit which fluidly communicates the foam-generating-component receiving portion with the cartridge outlet so that when the barrier is opened the components (26, 28) interact to generate the stable foam which flows to the cartridge outlet via the cartridge conduit; and wherein the carrier comprises: a carrier body (76; 276); a receiving portion (78; 278) for receiving the cartridge at or in the carrier body (76; 276); a carrier inlet (80; 280) for fluid communication with the outlet of the cartridge when the carrier (72; 272) is received in or at the receiving portion (78; 278); a carrier outlet (82; 282) for dispensing a stable foam to a user; a carrier conduit between the carrier inlet (80; 280) and the carrier outlet (82; 282) through the carrier body (76; 276); and a one-way valve in the carrier conduit for permitting movement of foam from the carrier inlet (80; 280) to the carrier outlet (82; 282) and preventing or limiting movement of fluid from the carrier outlet (82; 282) to the carrier inlet (80; 280). a carrier body (76; 276); a receiving portion (78; 278) for receiving the cartridge at or in the carrier body (76; 276); a carrier inlet (80; 280) for fluid communication with the outlet of the cartridge when the carrier (72; 272) is received in or at the receiving portion (78; 278); a carrier outlet (82; 282) for dispensing a stable foam to a user; a carrier conduit between the carrier inlet (80; 280) and the carrier outlet (82; 282) through the carrier body (76; 276); and a one-way valve in the carrier conduit for permitting movement of foam from the carrier inlet (80; 280) to the carrier outlet (82; 282) and preventing or limiting movement of fluid from the carrier outlet (82; 282) to the carrier inlet (80; 280).