Ultraviolet germicidal apparatus and method

Abstract

A germicidal method and apparatus for destroying airborne pathogenic bacteria such as tuberculosis bacteria using ultraviolet light. Air is drawn through a filter and into a sterilization chamber that is irradiated with ultraviolet light, and out through an exhaust opening. Consideration for the characteristics of the room in which the apparatus is installed and the positioning of the installation allows effective prevention of transmission of disease through expectoration and inhalation of airborne microdroplets of bacteria-containing sputum. The filter is of the low-density type which traps large particulates, but not small particulates of the size of the microdroplets, so that the filter does not become a bacteria colonization site. Baffles on the air intake opening and air exhaust opening to prevent ultraviolet light from escaping into the environment. The sterilization chamber is constructed such that the air passes the ultraviolet light bulbs twice as it circulates therethrough.

What is claimed is:  
     
         1 . A method for destroying airborne tuberculosis bacteria in air in a room having a set of walls and a ceiling panel, comprising mounting a device behind a wall or ceiling panel of the room, filtering the air using a filter mounted on the device, drawing the air through a sterilization chamber in the device having at least one ultraviolet light bulb for irradiating the air with germicidal ultraviolet light such that the air passes the light bulb twice, and releasing the air including destroyed bacteria back into the room.  
     
     
         2 . The method of  claim 1 , wherein the filter traps substantially no particulates and droplets smaller than 10 microns in diameter.  
     
     
         3 . The method of  claim 1 , wherein the device includes an air intake opening for air to enter the device and wherein the filter is positioned between the air intake opening and the sterilization chamber whereby substantially all air that enters the sterilization chamber passes first through the filter.  
     
     
         4 . The method of  claim 3 , wherein the sterilization chamber includes an air intake baffle to prevent ultraviolet light from escaping from the sterilization chamber through the air intake opening and into the room.  
     
     
         5 . The method of  claim 4 , wherein the releasing of the air including the destroyed bacteria back into the room is through an air exhaust opening in the device, and wherein the sterilization chamber includes an air exhaust baffle to prevent ultraviolet light from escaping from the sterilization chamber through the air exhaust opening and into the room.  
     
     
         6 . The method of  claim 5 , wherein at least one of the intake channel and exhaust channel is coated with an ultraviolet light-absorptive coating to absorb ultraviolet light incident thereon.  
     
     
         7 . The method of  claim 1 , wherein the sterilization chamber has an upstream side where the air enters the sterilization chamber and downstream side opposite the upstream side, the upstream side and downstream side being configured such that air enters the sterilization chamber from the upstream side and passes the ultraviolet light bulb a first time, reflects off the downstream side and passes the ultraviolet light bulb a second time, and exits the sterilization chamber.  
     
     
         8 . The method of  claim 7 , wherein the device includes a housing having a top surface and wherein the ultraviolet light bulbs are positioned within the housing below the top surface, and the downstream side includes a downstream surface extending from the housing top surface downward and toward the ultraviolet light bulbs, wherein the downstream surface and housing top surface define a recess to receive air flowing through the sterilization chamber and to reflect the air back toward the ultraviolet light bulbs.  
     
     
         9 . The method of  claim 1 , wherein the air is drawn through the device at an air flow rate that is calculated to produce at least ten air exchanges per hour in the room.  
     
     
         10 . An apparatus for destroying airborne tuberculosis bacteria, comprising a housing; an air intake opening in the housing for air to pass into the housing; an air exhaust opening in the housing for air to pass from the housing; a sterilization chamber in the housing and-in communication with the air intake opening and air exhaust opening, the sterilization chamber including at least one ultraviolet light bulb for irradiating the sterilization chamber with germicidal ultraviolet light; the sterilization chamber being configured such that the air passes the ultraviolet light bulb twice; a blower in communication with the air exhaust opening to draw air into the air intake opening, through the sterilization chamber, and out the air exhaust opening.  
     
     
         11 . The apparatus of  claim 10 , further comprising an air intake baffle between the air intake opening and the sterilization chamber to prevent ultraviolet light from passing from the sterilization chamber and out the air intake opening.  
     
     
         12 . The apparatus of  claim 11 , further comprising an air exhaust baffle between the air exhaust opening and the sterilization chamber to prevent ultraviolet light from passing from the sterilization chamber and out the air exhaust opening.  
     
     
         13 . The apparatus of  claim 10 , wherein the housing has an upper side, a lower side, a front side and a back side, and the air intake opening and the air exhaust opening are on different said sides.  
     
     
         14 . The apparatus of  claim 10 , wherein the air intake opening and the air exhaust opening are on opposite sides.  
     
     
         15 . The apparatus of  claim 10 , further comprising a door in the housing to access the ultraviolet light bulb.  
     
     
         16 . The apparatus of  claim 10 , wherein the sterilization chamber includes an upstream side from which the air enters and a downstream side opposite the upstream side, the downstream side defining a recess to receive air flowing through the sterilization chamber and to reflect such air back toward the ultraviolet light bulb.  
     
     
         17 . The apparatus of  claim 16 , wherein the upstream side is positioned between the air intake opening and the sterilization chamber such that air flowing into the device flows around the upstream side and into the sterilization chamber.  
     
     
         18 . The apparatus of  claim 17 , wherein the upstream side includes a recess toward the air intake opening to receive air flowing into the device.  
     
     
         19 . The apparatus of  claim 10 , wherein the apparatus does not include any filter to trap particulates smaller than 10 microns in diameter.  
     
     
         20 . The apparatus of  claim 19 , wherein the apparatus includes filter between the air intake opening and the sterilization chamber to trap particulates larger than 10 microns in diameter.