Abstract: An air purifier has an air flow cavity bounded by cavity walls and a source of ultraviolet light emitting ultraviolet light within the cavity. The cavity walls have an ultraviolet light reflective coating. A plurality of photocatalytic particles are associated with the reflective coating. The photocatalytic particles are of a type which leads to production of oxygen and hydroxyl free radicals when illuminated with ultraviolet light in the presence of water.

Abstract: A UV reflective cavity may be provided in a duct by attaching a plurality of tiles to the interior surface of the duct, each of the tiles having UV reflective surface.

Abstract: A photo-catalytic overcoat on a UV reflective paint layer is employed to maintain high reflectance for long periods of time by continuously removing organic films when exposed to UV light. Advantageously, nano-particles comprising the photo-catalytic overcoat are composed of a semiconductor material that lead to the production of oxygen and hydroxyl free radicals when illuminated with UV light in the presence of water vapor. Some of these free radicals oxidize organic surface films, converting the surface films into gaseous H2O and CO2. This reduces the amount of organic deposits on the surface of the reflective paint layer.

Abstract: An air purifier has an air flow path with a dielectric body interposed across the path. The dielectric body may be made of, for example, quartz or alumina fibers or silica granules or sponge so that it is porous to air and transmissive to ultraviolet (“UV”) light. A source of ultraviolet light emits UV1 and UV2 light into the airflow path upstream of the dielectric body and at least UV2 light into the dielectric body itself. The UV light forms ozone. The ozone, as well as water vapor in the air, naturally attaches to the dielectric body which concentrates these materials in the dielectric body. The UV light irradiating the ozone and water in the dielectric body causes the formation of highly reactive hydroxyl radicals which assist in sterilizing the incoming air.

Abstract: A photo-catalytic overcoat on a UV reflective paint layer is employed to maintain high reflectance for long periods of time by continuously removing organic films when exposed to UV light. Advantageously, nano-particles comprising the photo-catalytic overcoat are composed of a semiconductor material that lead to the production of oxygen and hydroxyl free radicals when illuminated with UV light in the presence of water vapor. Some of these free radicals oxidize organic surface films, converting the surface films into gaseous H2O and CO2. This reduces the amount of organic deposits on the surface of the reflective paint layer.

Abstract: An air purifier has an air flow path with a dielectric body interposed across the path. The dielectric body may be made of, for example, quartz or alumina fibers or silica granules or sponge so that it is porous to air and transmissive to ultraviolet (“UV”) light. A source of ultraviolet light emits UV1 and UV2 light into the airflow path upstream of the dielectric body and at least UV2 light into the dielectric body itself. The UV light forms ozone. The ozone, as well as water vapor in the air, naturally attaches to the dielectric body which concentrates these materials in the dielectric body. The UV light irradiating the ozone and water in the dielectric body causes the formation of highly reactive hydroxyl radicals which assist in sterilizing the incoming air.

Abstract: An air purifier has a perforated plate between UV lamps on the one hand and a porous air filter on the other. Biological material is trapped by the filter and eventually killed by the low dose of UV radiation which passes through the perforations in the plate. Filtered air passing through the plate is subjected to a high dose of UV radiation which sterilizes remaining biological material in the air. An electrostatic filter at the outlet may trap viruses which have been positively charged either by the action of the UV lamps or by positively charging the plate in order to strip electrons from the viruses. The UV lamps may be mercury lamps which are allowed to emit at both their ozone forming wavelength as well as the ozone breakdown wavelength. In such instance, a light filter surrounds the lamps which passes light only at the ozone breakdown wavelength. Air subjected to the unfiltered light is consequently subjected to ozone, which is a known biocide.