A method of controlling operation of a diffusion appliance to treat the atmosphere within an enclosed space. The method may include programming the operation of the appliance according to a control scheme specifying a flow rate of liquid to a diffusion means and a periodic operation of the diffusion means. Control schemes may be associated with different volumes of spaces to be treated by the appliance, the rate of decay of the liquid within the space to be treated and the level of concentration of the liquid desired within the space.