a user - programmable monitoring and dispensing system for controlling the dispensing of water vapor and various other media into an hvac air stream in residential or commercial structures . the various media to be dispensed are preferably water - soluble , and mixed with the system water supply to be dispensed with the water vapor added to the hvac air stream . these materials may be fragrances or aromas , intended to produce an aesthetic effect , or they can be agents capable of pesticidal , bacteriacidal , fungicidal or sporacidal effect for use as acute or prophylactic treatment for infestation . the dispensing system central processor is pre - programmed with a default concentration algorithm for each media to be dispensed . the concentration of media in aqueous solution is initially controlled by this default algorithm at each of several concentration levels , from lowest to highest . after being exposed to the air containing the dispensed media at a medium concentration of the default algorithm for a default time period , the user may indicate , via a data entry / display , whether the perceived concentration is higher or lower than that desired . this input from the user to the central processor acts to replace the default concentration algorithm with a new , preferred algorithm wherein the scale of media concentration is shifted to correspond to the user &# 39 ; s preference .