Abstract: Movement of the cover relative to the housing spring loads and latches a piston carrier in the armed position. Inhalation causes a passageway door to open, releasing the carrier latch to permit the carrier to be moved toward the canister by the spring. The piston moves with the carrier, due to a fluid connection therebetween, applying a compression force on the spring loaded canister valve stem and causing it to dispense the inhalant through an opening in the piston which functions as a nozzle. After the inhalant is dispensed, the carrier fluid vents permitting the spring of the canister valve stem to move the piston relative to the carrier, and thus release the force applied to the valve stem by the piston. The sensitivity of the toggle linkage between the door and the carrier latch is adjustable. The linkage can be manually tripped for testing purposes.