Airborne bacteria or other microorganisms permeate the air we breath and the water we drink. Some of these microorganisms with which we share our environment cause disease. Medical environments, such as hospitals, have a high degree of pathogens in the air and water and highly susceptible, weakened patients. The existence of biological weapons of mass destruction require protection of command centers, barracks, ships, and other closed environments against biological agents. Today""s modern sealed high-rise structures with central air conditioning and heating, through duct systems, need protection from the spread of disease among its occupants and from colonies of microorganisms which may live in the duct and water system. Today, biologic protection is necessary on the battlefield and in the workplace, the hospital and the home.
Much effort has gone into trying to destroy atmospheric pathogens with only limited success. It has long been recognized that pathogens can be destroyed in the air if they are irradiated with ultraviolet (UV) light at a wavelength of 253.7 nanometers (Germicidal Wavelength). In order for the UV light to kill microorganisms, the UV rays must directly strike the microorganisms for a sufficient time. Because of the absolute necessity for antiseptic surroundings, UV lamps of the required Germicidal Wavelength are often used in operating rooms, wards, and nurseries of hospitals.
The exposure to UV light necessary to kill microorganisms is a product of time and intensity. However, due to the dangers to humans of irradiation from wide-spread use of UV lamps, exposure to UV light has been limited by government regulations. The current occupant exposure limit (ACGIH, NIOSH standard) for 254 m ultraviolet germicidal wavelength ceiling fixtures is 6000 xcexcwatts seconds/cm2 in one eight hour day. Thus, the maximum allowed intensity per second is 0.2 xcexcW/cm2. At this intensity, eight hours at the allowed exposure level is required to gain a 90% kill of Mycobacterium tuberculosis (90% kill-value=6200 xcexcwatts/cm2) at head height. For 100% kill using the same standard, the value is 10,000 xcexcwatts/cm2, requiring 13.89 hours of exposure. The required low intensity, and resulting long exposure times, permit migration of microorganisms out of range of the UV lamp and result in accumulation of microorganisms which survive the UV lamp in the room. Increasing air circulation does not increase exposure of microorganisms. It only moves organisms past the UV lamp without sufficient exposure.
To overcome these problems there have been various attempts to circulate air passed UV sources in enclosures which acts to shield the UV irradiation from the room""s occupant. Usually, such systems are free-standing, or wall or ceiling mounted devices which circulate the air in a single room through the enclosure and, accordingly, whose protection is confined to that room. See, for example, U.S. Pat. No. 5,330,722 to Pick, which discloses a germicidal air purifier which draws air through a chamber in which there is mounted an ultraviolet source which acts to kill microorganisms caught in the filter structure. Similarly, U.S. Pat. No. 5,612,001 to Arthur L. Matschke, discloses a germicidal air cleansing enclosure having an internal ellipsoid chamber which contains UV lamps along the major axis of the ellipsoid. The unit is free-standing and treats air in a single room.
While a system such as that disclosed in U.S. Pat. No. 5,612,001 to Arthur L. Matschke, may be highly effective to cleans the contents of a single room, normal air conditioning and heating ducts would continue to allow circulation of untreated air into and out of a room. This allows untreated air containing pathogens from another room, or in the duct system, to enter the room and come into contact with humans before being treated and allow a certain amount of pathogens in a room to enter the duct system prior to being treated by the free-standing unit.
Various attempts have been made to place ultraviolet light sources in duct systems to germicidally cleans fluids such as air as they pass through the duct system. See, for example, U.S. Pat. No. 5,635,133 to Glazman, U.S. Pat. No. 5,200,156 to Wedekamp and U.S. Pat. No. 5,107,687 to Candelares. Each of these patents disclose an ultraviolet irradiation source in a duct to cleanse a fluid traveling through a duct of uniform diameter. The UV source is at right angles to the duct walls and UV energy is directed at least in part along the path of fluid flow. Thus, the level of ultraviolet energy varies along the flow path. As a result, the air circulated past the UV lamps in the prior art receive an uneven distribution of ultraviolet energy and a rapid diminution of energy levels outside the immediate area of the UV source. The grandparent of the present patent application, now U.S. Pat. No. 6,022,511, to Matschke, discloses an ellipsoidal, ultraviolet reflective chamber mounted in a duct system which exposes the air passing through the chamber to sufficient UV energy to germicidally cleanse all of such air. However, it does not provide the means for treating water in the same closed environment.
Bacteria or other microorganisms not only permeate the air we breath but also the water we drink. Much effort has gone into trying to limit or destroy water-borne pathogens. It has long been recognized that pathogens can also be destroyed in water if they are irradiated with ultraviolet (UV) light of a wavelength of 253.7 nanometers. In order for the UV light to kill microorganisms, and particularly pathogens, the rays must directly strike them. U.S. Pat. No. 5,874,741 to Matschke discloses an ellipsoid, ultraviolet reflective chamber to expose water passing through the chamber to sufficient UV energy to germicidally cleanse all of such water.
Conventional UV lamps for germicidal applications are normally in the form of elongated straight tubes similar in appearance to conventional florescent lights. Such lamps are not optimal for use in ellipsoidal chamber as they do not maximize the energy efficiency of the system as a whole.
It is an object of the present invention to use as a source of ultra violet radiation in an ellipsoid UV chamber, a lamp in the form of a helix whereby the UV source is concentrated in the center of the chamber so as to lengthen the path to initial reflection in a chamber, thereby increasing system efficiency.
The present invention is a germicidal chamber which uniformly irradiates all of the air passing through a duct system in which it is mounted, such as a central air system. The chamber replaces one or more sections of the duct and, in essence, becomes part of the duct work. The chamber has running along the chamber""s longitudinal axis an ultraviolet transparent pipe through which water or other fluids may pass. The ultraviolet transparent pipe is attached at or near both ends of the ultraviolet chamber to conventional pipes which passes through the wall either of the duct or the chamber and form part of the fluid circulatory system, such as a buildings water supply.
Each chamber is in the form of one or more ellipsoid sections which focus the energy uniformly throughout the chamber. A sphere is a form of ellipsoid and can be used in carrying forward the present operation. The chamber is connected to the duct so that all air drawn into the duct system must pass through the chamber. To accomplish this, each chamber is integral with the duct forcing all of the air in the duct on the upstream side to pass through the chamber. In order to eliminate back pressure which might arise from any impediment to the flow of air through the chamber while allowing reflection of all of the ultraviolet radiation back into the chamber, a grille formed from concentrical ellipsoid sections is positioned at each end of the chamber so that substantially all of the ultraviolet radiation is reflected back into the chamber while allowing relatively unimpeded flow of the air through the chamber.
The dispersion of ultraviolet light in the chamber and its energy efficiency can be improved by the use of a helically wound ultraviolet light source positioned around the major axis of the chamber in the center of the chamber. The helically wound ultraviolet light source may be positioned around the ultraviolet transmission pipe carrying a fluid to be treated. The geometric center point of the chamber is the point within the chamber from which light will travel the greatest distance before a first reflection, incident with the wall and, thus, the first absorption of energy. Thus, the efficiency of the light source decreases as the point of origin of the light source moves away from the center of the axis of the ellipsoid chamber as a product of the energy absorption and the subsequent infinite reflections through the enclosure. In the present invention, the helical light source is concentrated towards the center of the chamber to increase the efficiency in the even distribution of ultraviolet light throughout the chamber.