A valve assembly can automatically dispense aerosol content from an aerosol container at predetermined intervals without the use of electric power. A diaphragm at least partially defines an accumulation chamber that receives gas propellant from a portion of the can during an accumulation phase. Once the internal pressure of the accumulation chamber reaches a predetermined threshold, the diaphragm moves, carrying with it a seal so as to unseal an outlet channel, and thereby initiate a spray burst of the main active chemical. The diaphragm assumes its original position when the pressure within the accumulation chamber falls below a threshold pressure.