Aerosol dispensing metering valve

A breath-actuated aerosol device including a container for pressurized material provided with a dispensing metering valve, the valve comprising a valve body with a single internal metering chamber, the metering chamber having a base provided with an aperture, outer and inner seals closing the respective outer and inner ends of the metering chamber, a valve member co-operating with the seals and movable within the aperture between an inoperative position in which the chamber is isolated from the atmosphere while the chamber communicates with the interior of the container, and an operative position in which the contents of the chamber can be discharged to the atmosphere while the chamber is isolated from the interior of the container, the valve member being provided with a lower valve stem portion adapted to slidably engage the inner seal when the valve is in the inoperative position, and at least two channels extending longitudinally on the lower valve stem portion for communicating between the metering chamber and the interior of the container,

• the aperture being of such size that immediately above the inner seal there is an annular space of width 0.1 to 2 mm between the valve member and the walls of the aperture, and the channels being between 0.2 and 1.5 mm deep, such that the sum of the width of the annular space and the depth of the channels is at least 1 mm and the exit air trapped in the metering chamber and the entry of pressurized material into the chamber is readily allowed when the valve is in the inoperative position.