A system for delivery of aerosol therapy to spontaneously breathing patients comprises a housing 1 which defines a chamber 2. The housing has a base 3, a top 4 and a main body 5 extending between the base 3 and the top 4. An ambient air inlet 6 is located adjacent to the base 3 and is normally closed by an inlet valve 7. The housing also has a patient port 10 for receiving a mouthpiece 11 or a face mask 12. The mouthpiece 11 has an exhaust outlet 14 closed by an exhaust valve 15. Similarly, the face mask 12 has an exhaust outlet closed by an exhaust valve 16. Exhaled air is exhausted through the valves 15 and 16 to prevent recirculation through the chamber 2 which would adversely affect dose efficiencies. The housing also has an aerosol port 20 for receiving a vibrating mesh aerosol generating device 25. The aerosol port 20 is located in a side of the main body of the housing 1 for delivery of aerosol into the chamber 2 between the inlet valve 7 and the patient port 10, generally perpendicular to the flow of air through the chamber 2. A boss 30 extends upwardly from the base 3 and is spaced-apart inwardly of the main body 5 of the housing 1 to define a reception space or well 31. This facilitates collection of any rain-out within the chamber 2.
