A mist generator is used to deliver a high throughput extremely fine mist comprising a biocide. Flows of evaporating hot gas mix turbulently and enhance forced heat and mass transfer between the very fine droplets and the hot gas to form a well-mixed premixed evaporator, resulting in high humidity vapor formation well inside a tube. The high relative humidity vapor with elevated temperature is then condensed as it exits the tube and disperses into the volume to be decontaminated as a condensed vapor cloud, but neither as a mist nor as a pure vapor depending on temperature and humidity of room environment. The condensed vapor cloud may evaporate or settle on the volume surfaces and contents, whereby both dry vapor and condensed vapor are applied into the volume for the killing process.
