A hand-held inhalation device for delivering a nebulised medically active aerosol for inhalation therapy therapy, the device comprising (a) a housing having a user-facing side; (b) an impingement-type nozzle for generating the nebulised aerosol by collision of at least two liquid jets, the nozzle being firmly affixed to the user-facing side of the housing such as to be immobile relative to the housing ; (c) a fluid reservoir arranged within the housing ; and (d) a pumping unit arranged within the housing , the pumping unit having - an upstream end that is fluidically connected to the fluid reservoir ; - a downstream end that is fluidically connected to the nozzle ; wherein the pumping unit is adapted for pumping fluid (F) from the fluid reservoir to the nozzle ; wherein the pumping unit further comprises (i) a riser pipe having an upstream end, wherein the riser pipe is - adapted to function as a piston in the pumping unit, and - firmly affixed to the user-facing side of the housing such as to be immobile relative to the housing ; (ii) a hollow cylinder located upstream of the riser pipe , wherein the upstream end of the riser pipe is inserted in the cylinder such that the cylinder is longitudinally movable on the riser pipe ; (iii) a lockable means for storing potential energy when locked and for releasing the stored energy when unlocked, the means being arranged outside of, and mechanically coupled to, the cylinder such that unlocking the means results in a propulsive longitudinal movement of the cylinder towards the downstream end of the pumping unit; and (iv) a locking device for locking the lockable means . (a) a housing having a user-facing side; (b) an impingement-type nozzle for generating the nebulised aerosol by collision of at least two liquid jets, the nozzle being firmly affixed to the user-facing side of the housing such as to be immobile relative to the housing ; (c) a fluid reservoir arranged within the housing ; and (d) a pumping unit arranged within the housing , the pumping unit having - an upstream end that is fluidically connected to the fluid reservoir ; - a downstream end that is fluidically connected to the nozzle ; - an upstream end that is fluidically connected to the fluid reservoir ; - a downstream end that is fluidically connected to the nozzle ; (i) a riser pipe having an upstream end, wherein the riser pipe is - adapted to function as a piston in the pumping unit, and - firmly affixed to the user-facing side of the housing such as to be immobile relative to the housing ; - adapted to function as a piston in the pumping unit, and - firmly affixed to the user-facing side of the housing such as to be immobile relative to the housing ; (ii) a hollow cylinder located upstream of the riser pipe , wherein the upstream end of the riser pipe is inserted in the cylinder such that the cylinder is longitudinally movable on the riser pipe ; (iii) a lockable means for storing potential energy when locked and for releasing the stored energy when unlocked, the means being arranged outside of, and mechanically coupled to, the cylinder such that unlocking the means results in a propulsive longitudinal movement of the cylinder towards the downstream end of the pumping unit; and (iv) a locking device for locking the lockable means . <EOS>