Abstract: A method for disinfecting an airstream containing microorganisms by electrostatic precipitation by passing the airstream through the space between at least one grounded collection plate having at least one electrode spaced apart therefrom connected to a source of electrical potential, wherein the improvement comprises contacting the airstream with a photocatalyst having a predetermined band gap energy coated on the surface of each grounded collection plate and illuminated with photons having a wavelength corresponding to the band gap energy of the photocatalyst, so that at least a portion of the microorganisms that collect on the grounded collection plate are destroyed by photocatalytic oxidation. Devices embodying disinfecting methods are also disclosed.

Abstract: A method for disinfecting an air stream containing microorganisms including the steps of providing an air stream containing microorganisms having a relative humidity greater than about 40%; and contacting the air stream with a photocatalyst having a predetermined band gap energy in the presence of a source of photons having a wavelength corresponding to the band gap energy of the photocatalyst, so that at least a portion of the microorganisms in the air stream are destroyed by photocatalyfic oxidation. Devices embodying the method of the invention are disclosed, such as stand-alone devices and devices incorporated into the HVAC systems of buildings, including the air supply registers. Photocatalyst-coated filter media capable of trapping bioaerosols are also disclosed.

Abstract: A system to disinfect and detoxify indoor duct-transported air to improve the quality thereof. A reactor is provided across a duct or housing and consists of a coated surface along the airstream path on which a semiconductor catalyst such as TiO.sub.2 has been coated. Ultraviolet lamps are installed in the reactor such that the catalyst is exposed to UV rays as the air passes over it. As the photons of ultraviolet light are absorbed on the TiO.sub.2 catalyst in the presence of water molecules in the air, hydroxyl radicals are created, which, in turn, cause the destruction of chemical and microbiological contaminants in the air. A relative humidity of 50%, under specific conditions of residence time provides an efficient number of water molecules to cause inactivation of microorganisms. The catalyst may be fixed on the matrix or on the surface of the duct as long as the ultraviolet light is incident on the catalyst as the air moves across it.