A method of maintaining a desired level of a dispersed liquid within an occupiable semi-enclosed space is provided. The method includes: providing a liquid diffusion appliance including a liquid to be dispersed; operating the liquid diffusion appliance to disperse the liquid into the occupiable semi-enclosed space throughout a treatment period in which the occupiable space is subjected to entry and exit of occupants to and from the occupiable semi-enclosed space; sensing the concentration of one or more chemical components of the dispersed liquid within the occupiable semi-enclosed space; and modifying the operation of the liquid diffusion appliance based on the concentration of the one or more chemical components of the dispersed liquid within the occupiable semi-enclosed space to achieve a desired concentration.