<p>In the present invention, an actuating mechanism for a hand held canister is provided in which a slider is moveable by finger pressure from a valve-disengaged position into a valve-engagable position and a concealed spring returns the slider to a valve-disengaged position when finger pressure is removed. The spring is preferably molded with the slider, projects through a slit in the over-cap of the canister and acts in a vertical plane against a stop depending from the over-cap. It is energised when the slider is moved into the valve engagable position. The slider is preferably releasably locked in the valve disengaged position.</p>
