A vapor delivery device having a reservoir for containing an amount of fluid. An ejector receives the fluid, and a controller fires the ejector to express a given dosage of the fluid through a number of nozzles in the ejector into an airstream at a firing frequency and for a firing duration. As the amount of the fluid within the reservoir decreases, the controller also at least one of reduces the firing frequency of the ejector, increases the number of nozzles, and increases the firing duration.
