Disclosed are automated aerosol dispensers for delivering chemicals (e.g. cleaners, fragrances, insect control agents) from the dispenser to selected locations (e.g. the air; a toilet bowl; a shower enclosure). There is an actuator (e.g. a push button or a foot pedal) for initiating dispensing, and a holder for an aerosol container. The aerosol container stores the chemical before use. There is a switch associated with the holder that recognizes when the aerosol container has been mounted to the holder, and when thereafter that aerosol container has been dismounted from the holder. A controller controls dispensing of the chemical from the aerosol container in response to actuation. The controller has a timer that determines the amount of time that chemical is to be delivered from the aerosol container upon the dispenser being actuated by the actuator. A database is provided for assisting the controller in varying the time that the timer permits dispensing in response to activation. The system thus can correct for pressure drop off in the can as the can nears empty.