Filter apparatus

Claim 1

Filter apparatus for removing contaminants from air, comprising: a housing wall that is generally annular in section and has first and second opposite ends, said housing wall bounding a filter chamber and being formed with an inlet opening at said first end thereof, a cover attached to the housing wall at said second end thereof and formed with an outlet opening, impeller means for maintaining a flow of air through the filter chamber from the inlet opening to the outlet opening, a generally circular porous filter pad located inside the filter chamber so that air flowing along the axis of the housing wall from said one end of the housing wall to said opposite end thereof passes through the filter pad, whereby particles greater than a predetermined size are removed from air entering the filter chamber by way of the inlet opening, the filter pad being made of electrically insulating material such that when air passes through the pad, friction between the air and the insulating material generates a strong electrostatic charge that attracts and retains airborne particles, a drum filter support plate mounted in the filter chamber between the porous filter pad and the cover, a drum filter mounted in the filter chamber coaxially therewith and engaging the cover and the drum filter support plate, an annular space being defined between the drum filter and the internal surface of the housing wall and the drum filter defining a second chamber that is in communication with the outlet opening so that air flowing from the inlet opening to the outlet opening passes through the porous filter pad to said annular space and passes from said annular space to said second chamber through the drum filter, the drum filter comprising first, second and third porous webs through which air flowing from the inlet opening to the outlet opening passes sequentially, the first and third webs being impregnated with activated charcoal and the second web being impregnated with molecular sieve material, whereby the drum filter removes selected molecular species from air that has passed through the porous filter pad in the direction from the inlet opening to the outlet opening, a lamp located in said second chamber, said lamp, when energized, emitting light at a wavelength within the range from about 253 nm to about 257 nm, whereby air in said second chamber is irradiated with ultraviolet light, and a power supply circuit for energizing the lamp.