Steam rises from the surface of the boiling water leaving behind heavy metals, dissolved solids and other impurities, killing any bacteria, viruses, cryptosporidium and gardia. These remain in the boiling chamber as a residue which is easily removed by the cleaning crystals supplied.
The steam rises to the top of the boiling chamber, entering the fan-cooled stainless steel cooling duct. This turns the steam back into water, although now the water is now classified as pure. Your Steam Distiller includes a post-filtration filter (good for one month) as a final precaution to remove any residues of organic chemicals. The filter is needed to remove the final residue of chemicals such as chlorine, which may rise with the steam.