| abstract |
An inhaler comprising a reservoir (5) of inhalable composition, an outlet valve (7) to control the flow of composition from the reservoir, the valve outlet orifice (32) having a maximum dimension h, measured in the direction of opening when fully opened; an expansion chamber (33) downstream of the valve having a length L and diameter D measured half way along the expansion chamber; and an exit orifice (31) at the downstream end of the expansion chamber, the orifice having a length 1 and a diameter d; wherein 0.1 < h/d < 1.0; 0.05 < h/D < 0.25; 1 < D/d < 10; 5 < L/D < 15; 0.1 < 1/d < 5. |