A delivery system for dispensing a medicament comprising: a housing (55, 155); a first chamber (10, 110) for storing a supply of the medicament, the first chamber (10, 110); being coupled within the housing (55, 155); a second chamber (20, 120) coupled within the housing (55, 155); the second chamber (20, 120) being in fluid communication with the first chamber; a dosing tube (35, 40) connecting the first chamber (10, 110) and the second chamber (20, 120), the dosing tube providing fluid communication between the first chamber (10, 110) and the second chamber (20, 120); and an outlet port for dispensing the medicament outside the housing (55, 155), the outlet port being coupled to the housing (55, 155) and in fluid communication with one of said first and second chambers (10, 20); characterized in that: the system further comprises a plunger (16,116) movably disposed with respect to the second chamber (20, 120); wherein the system is adapted to draw air from an environment exterior to the housing (55, 155) into one of the first or second chambers (10, 20) upon withdrawal of the plunger (16,116) with respect to the second chamber (20, 120) to set a desired dose; and wherein the system is adapted to communicate air from the second chamber (20, 120) to the first chamber (10, 110), the air causing displacement of the medicament from the first chamber (10, 110) to the outlet port. a housing (55, 155); a first chamber (10, 110) for storing a supply of the medicament, the first chamber (10, 110); being coupled within the housing (55, 155); a second chamber (20, 120) coupled within the housing (55, 155); the second chamber (20, 120) being in fluid communication with the first chamber; a dosing tube (35, 40) connecting the first chamber (10, 110) and the second chamber (20, 120), the dosing tube providing fluid communication between the first chamber (10, 110) and the second chamber (20, 120); and an outlet port for dispensing the medicament outside the housing (55, 155), the outlet port being coupled to the housing (55, 155) and in fluid communication with one of said first and second chambers (10, 20); characterized in that: the system further comprises a plunger (16,116) movably disposed with respect to the second chamber (20, 120); wherein the system is adapted to draw air from an environment exterior to the housing (55, 155) into one of the first or second chambers (10, 20) upon withdrawal of the plunger (16,116) with respect to the second chamber (20, 120) to set a desired dose; and wherein the system is adapted to communicate air from the second chamber (20, 120) to the first chamber (10, 110), the air causing displacement of the medicament from the first chamber (10, 110) to the outlet port. the system further comprises a plunger (16,116) movably disposed with respect to the second chamber (20, 120); wherein the system is adapted to draw air from an environment exterior to the housing (55, 155) into one of the first or second chambers (10, 20) upon withdrawal of the plunger (16,116) with respect to the second chamber (20, 120) to set a desired dose; and wherein the system is adapted to communicate air from the second chamber (20, 120) to the first chamber (10, 110), the air causing displacement of the medicament from the first chamber (10, 110) to the outlet port.