Patent Publication Number: US-2007102280-A1

Title: Air supply apparatus

Description:
This is a continuation-in-part of U.S. application Ser. No. 11/268,936 to Charles Eric Hunter, filed Nov. 8,  2005 ; of Ser. No. 11/317,045 to Charles Eric Hunter filed Dec. 23, 2005; of the patent application Ser. No. 11/412,231 entitled “Air Supply Apparatus” filed Apr. 26, 2006, and of provisional patent application 60/796,368 entitled “Air Supply Apparatus” filed May 1, 2006. 
    
    
     FIELD OF THE INVENTION  
      The invention relates to an air supply system and applications of the air supply system to kill airborne organisms such as viruses, bacteria and fungi, also referred to as organic material, pathogens or biological contaminants using ultraviolet (UV) radiation. For purposes of this application the term “killing” also includes any DNA or RNA destruction.  
     BACKGROUND OF THE INVENTION  
      In order to provide an effective sterilization respirator based on UV sterilization the present application recognizes the need to take into account air consumption rates by the user. The present invention therefore takes into consideration the peak respiration of a typical person under certain working conditions and factors in a maximum flow through the respirator. By way of example, the present invention deals with the design of the respirator that focuses on providing a safe supply of air for persons working in a pandemic environment performing moderate exercise. Moderate or light exercise is defined by NIOSH as work not exceeding 50 watts. This level of activity equates to the average adult walking at a rate of three miles per hour. NIOSH sets the peak respiration at 85 SLM under these conditions where the air consumption in minute-liters is 25.  
      The embodiments discussed below target essential workers and their families that will be performing only moderate exercise, not first responders or members of our military that perform exercise at levels of 150 watts and greater. It will, however, be appreciated that the approach described is scalable to high-end applications or any other applications.  
      The specifications for the respirator apparatus targeting the essential worker and their families are:  
      Maximum Flow—220 SLM (this is through the filter to the mask)  
      Peak Respiration—90 SLM (1.5 liters per Second) {with S&lt;10 E−11} 
      Power Consumption—7 watts  
      Battery Charge—8 hours (based on a degraded 70 watt-hour battery pack)  
      Weight—2.5 lbs. (battery and UV chamber weight is 1.5 lbs.)  
      The most complete attempt to model the elimination of active airborne pathogens using UVC light is  Mathematical Modeling of Ultraviolet Germicidal Irradiation for Air Disinfection  by Kowalski et al, in the Journal: Quantitative Microbiology 2, 249-270, 2000. The paper outlines a classical approach to dealing with pathogen population decay defined by the equation S=e(−kIt). Where S is the fraction of the pathogen population that survives exposure, I is the intensity in microwatts per square cm, k is the standard rate constant for a particular pathogen expressed in square cm per micro joule and t is the exposure time in seconds.  
      As outlined by Kowalski et al, research with 8 known pathogens, including three viruses, has shown a secondary population that survives after the initial exposure. This population is dealt with using the classical approach by assigning a second rate constant k2 and adding the decay of this population to the first using the same equation S=e(−k2It). Information regarding the values for K2 is limited, only being available for 8 pathogens. Reasons for a secondary survival population can be ascribed to one or more of several possibilities, including 1) higher resistance to UVC 2) clustering of pathogens and 3) non-optimum chamber design where intensity (photon flux) is wildly uneven. (Intensity being high nearest to the lamp and much lower elsewhere). In the past, dose studies were typically performed by projecting UVC light onto pathogens on a surface. It is therefore likely that under these conditions reasons 1 and/or 2 are primarily responsible for the secondary survival population of pathogens.  
      The third reason, however, suggests that actual results in UVC systems to date have been poor; since all known systems have utilized a design where air flows past a round lamp having a photon flux that varies dramatically based on the lamp radius and the distance from the lamp. In fact, some literature, incorrectly teaches that intensity drops as a square from the distance to the lamp, not even considering the lamp radius {as the radius approaches zero the ratio of X1 (the intensity beside the lamp)/X2 (the intensity at some distance away from the lamp) goes to infinity}. More sophisticated attempts to model the intensity field (such as Kowalski et al) deal with more than 15 variables many of which are difficult to measure or predict, and even these models show a wide variation in intensity with current chamber designs.  
      Most importantly, prior art systems have not provided an evaluation or determination of the success of air sterilization systems and have made no attempts at measuring low pathogen concentrations. The fact that these systems have dramatic variations in effectiveness as shown both in demonstations and through the use of models means that secondary effects such as k2 that were measured on a planar surface have not been addressed in prior art systems.  
      The present invention seeks to address some of these issues by making use of a sterilization or kill chamber that includes a pump, a fan, or a blower in which the flow rate is contolled. In order to address the secondary survival of pathogens due to uneven UV intensity, the present invention further proposes providing a high intensity radiation zone.  
      The use of pumps, fans, and blowers to move fluids is known. For instance air in rooms is commonly circulated by making use of ceiling mounted or standing fans. These typically include a number of settings for manually adjusting the fan speed to suit the user&#39;s preferences. However, in the case of pumps, blowers or fans mounted in a housing or conduit in order to move air through the housing or conduit, no known system automatically adjusts power to the pump, blower or fan or adjust shutters or other mechanisms such as a butterfly valves in order to achieve constant flow or constant pressure as external factors vary and therefore seek to impact the flow rate or air pressure. The present invention proposes a system in which flow rate or air pressure in the system is controlled to keep flow rate or pressure substantially constant.  
      In the field of air purification much work has been done to filter out particles, e.g., filters in air duct systems found in many forced air home heating units. Filters are also used to filter out harmful particles in face masks as is discussed below. In the case of biological contaminants, considerable work has also been done in sterilizing water using mercury vapor lamps, and the use of vacuum UV sources to kill biological contaminants in air has also been considered. For instance, Brais, U.S. Pat. No. 5,833,740 discloses a chemical air purification and biological purification using UV sources, and making use of a turbulence generator mounted within the housing. Air purification by means of UV is also discussed in Kaura, U.S. Pat. No. 6,623,544B1. In this patent the air is treated with mechanical filters (including electrostatic filters), ionization of energetic ions, and UV light radiation. The PAPR made by 3M, on the other hand, comprises an air purifier making use of chemicals to kill biological pathogens.  
      Showdeen, et al., U.S. Pat. No. 5,446,289 also discusses the sterilization of articles by means of UV lamps mounted in a chamber.  
      However, the prior art systems making use of UV sources to kill biological contaminants in air do not consider controlling the flow rate past the UV radiation source in order to control the UV dosage to which the contaminants are exposed or controlling the pressure in a kill or sterilization chamber. More particularly, they do not consider moving the air past a UV source using a pump, fan or blower and adjusting the flow rate of the air by adjusting power to the pump, fan or blower. Thus the prior art also does not consider power saving, by automatically adjusting power to the pump, fan or blower in response to changing demands, which is particularly important in portable devices.  
      Furthermore, the prior art systems do not ensure that biological contaminants passing through a kill or sterilization chamber or through a sterilization zone, e.g., a UV radiation zone provided in an air duct system of a house, ship or aircraft, receive an adequate amount of radiation to render them harmless. Nor do they optimize power usage in portable devices, or consider the possible harmful byproducts of UV radiation, such as ozone and carbon monoxide.  
      Also there is no art that teaches actively destroying biological contaminants in a face mask assembly using ultraviolet radiation. When it comes to the field of face masks, masks with various types of filters are commonly known. Wadsworth, et al., U.S. patent application publication 2005/0079379 A1, for instance, describes an improvement on such a face mask using a two-layer or multi-ply barrier fabric having at least one barrier fabric layer which is impermeable to liquids but allows moisture vapor to pass through the micropores and in which the layers may contain an antimicrobial agent. Kirollos, et al., U.S. patent application publication 2004/0223876, in turn, describes exposure protection equipment such as a respiratory protection device, which includes a detector for indicating the presence of a target substance.  
      While Wen, U.S. patent application publication 2003/0111075 A1 describes a gas mask that kills bacteria, it does so using chemical agents. Wen makes use of a filtration apparatus containing an active stage and a passive stage, the active stage containing at least one chemical agent to kill ambient bacteria and viruses.  
      The present invention seeks to address these issues and seeks to provide not only sterile air to the user by means of a portable face-mask arrangement but also proposes sterilization of air exhaled by the user.  
     SUMMARY OF THE INVENTION  
      According to the invention there is provided an air sterilization system, comprising a UV light source for providing UV light of a predefined intensity, a blower having an input and an output, a filter, e.g., a HEPA filter mounted at the input or output of the blower, the air pressure or air flow rate of the air supply being automatically adjusted to account for changes in the demand the system further comprising means for radiating pathogens with high intensity UV light in a high intensity zone, wherein the high intensity light is of a higher intensity than the predefined intensity. The high intensity light may be created by a UV beam magnifier such as a UV lens or by a separate high power light source. It will be appreciated that providing a high intensity zone with high intensity light exposure is applicable to both user specific devices that make use of face masks, as well as to multi-user systems such as air duct sterilization systems.  
      Further, according to the invention there is provided an air sterilization system for providing a sterile air supply to a face mask, comprising a face mask having an air input and an air output, a kill chamber that includes a housing having an input for receiving air from the atmosphere and an output connected to the input of the face mask, a UV light source, a pump, fan or blower for generating an air stream, and a particle filter, e.g. a HEPA filter mounted on the housing, wherein air pressure or air flow rate of the air supply is automatically adjusted to account for changes in the demand, and wherein the system includes one or both of a UV beam magnifier and a second input to the housing connected to the output from the face mask. The system may measure the flow rate of the air stream or air pressure using a sensor and use the sensor signal to control the flow rate of said air stream or the air pressure in the air stream. The flow rate or pressure may be controlled by controlling power to the pump, fan or blower or may be controlled by adjusting a manually controlled or an electronically controlled valve mounted in the housing or conduit or mounted upstream or downstream of the housing or conduit, or by adjusting both the pump, fan or blower as well as such a valve. In particular, flow rate may be adjusted to provide for substantially constant flow, or pressure may be adjusted to provide a substantially constant pressure. The valve may include a hole to bleed air through the valve or may be adapted to always be at least partially open to ensure a slight positive pressure. The system may be a portable system in which power to the pump, fan or blower and any electronically controlled valve are powered by at least one battery. Changes in pressure caused by the inhaling and exhaling of the user may be adjusted for to provide a constant air flow rate or constant air pressure system. In particular, a pressure sensor mounted in the housing or conduit, or in the mask may be used to provide a pressure signal for use in adjusting power to the pump, fan or blower and/or to control an electronically controlled valve, in order to provide air to the user on demand, thereby providing a positive pressure in the mask while avoiding excessive pressure build-up during exhaling or low exertion by the user, while ensuring sufficient air flow during inhaling irrespective of the level of exertion of the user. Thus, in a constant pressure system of the invention, one embodiment provides for adjusting a valve to accommodate pressure changes due to inhaling and exhaling by a user (since the system of the invention seeks to maintain constant pressure). As the valve changes, flow rate changes, which impacts how hard the pump, fan or blower has to work (since the air has to be accelerated from zero on the upstream side of the pump, fan, or blower, to the particular flow rate needed on the downstream side of the pump, fan, or blower.) In cases where power to a blower or fan is adjusted, preferably a fan or blower designed to have low inertia is used e.g. through the use of graphite components and further providing means for quickly stopping the fan when air flow is not required. The stopping may be achieved through the use of an electrically activated micro brake. The fan or blower may make use of multiple motors of the same or different power that can be individually activated to optimize power consumption by powering only a chosen number of motors or a motor of the chosen power for a desired flow rate.  
      The pressure sensor may be located near or on the mask to limit errors due to pressure drops along the delivery tube. The sensor can provide a voltage or current output. Preferably the signal is a mixed signal device wherein a small voltage signal is digitized to ensure accuracy of the transmitted signal. Preferably multiple sensors are used that can be averaged or where high and low values are thrown out to ensure repeatability and stability of the signal. The sensors may be temperature controlled to avoid errors due to changes in ambient temperature. The system may also be used in conjunction with an ultraviolet (UV) light source to kill or destroy biological pathogens. The nature of the filter may be chosen to limit clusters or clumps of the particular biological pathogen(s) that the UV light source is intended to kill or destroy. Typically a filter capable of filtering 0.1 μm diameter or smaller pathogens is used. In order to address biological contaminants with a higher resistance to UV radiation (secondary survival rates of pathogens), a high intensity zone may be defined at the input or output to the housing or conduit or any other location in the housing or upstream or downstream of the housing and may include a small hole or passage e.g., a 0.3 cm 2  hole through which the air is passed and which defines a high intensity zone. The UV beam magnifier create the high intensity radiation by focusing the UV beam on the high intensity zone e.g. on the 0.3 cm 2  hole. Thus the means for radiating pathogens with high intensity UV light may comprise a beam magnifier, which typically includes a lens made of high transmissivity material such as silicon dioxide. The high intensity zone may include a highly reflective cylinder extending from the hole to define a channel to ensure sufficient exposure time to the air passing through the high intensity zone (or to ensure exposure to a pulse in the case of a flash lamp, discussed below). Instead of a UV mercury vapor lamp, a UV laser or a flash lamp (e.g., xenon or xenon-mercury flash lamp produced by Perkin Elmer such as the RSL3100) producing a high intensity burst of UV light or other energy source may be used. In such a case, the beam magnifier may in some embodiments be used with the UV laser or flash lamp. The system is typically a portable system and may be powered by one or more replaceable or rechargeable batteries, e.g., lithium ion batteries. Air exhaled by the user may be sterilized by channeling the exhaled air to the second input of the housing or may be sterilized by supplying the exhaled air to a separate kill chamber.  
      Still further, according to the invention, there is provided a method of reducing pathogens in an air stream, comprising exposing the air stream to a first intensity UV radiation for a first predefined period of time, and exposing the air stream to an elevated intensity of UV radiation that is higher than said first intensity. The elevated intensity may include a range of elevated intensities and exposure to the elevated intensity may be for a duration that is less than the first predefined period of time, and may include the time during which the air stream passes through a high intensity zone. UV radiation for a first predefined period of time may be defined by the time that it takes the air stream to pass through a certain region, e.g., through a housing. The elevated intensity may be provided by a beam magnifier, e.g., a UV lens. The high intensity zone may comprise a channel through which the air stream is forced to pass or may comprise part of the housing.  
      Still further, according to the invention, there is provided a method of providing protection against airborne pathogens, comprising (a) providing a face mask for channeling air to a user, and (b) sterilizing the air that is channeled to the user, using UV radiation. The method may include sterilizing the air exhaled by said user. The method may include controlling the flow rate or pressure of air channeled to the user. The peressure may be controlled to maintain substantially constant pressure during inhaling and exhaling by the user and during changes in exertion by the user. The air stream provided by the blower/fan/ pump or the pressure may be controlled by controlling at least one of a flapper valve and the blower, fan or pump. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a simplified representation of one embodiment of a portable sterilization apparatus of the invention;  
       FIG. 2  shows another embodiment of part of a sterilization apparatus of the invention;  
       FIG. 3  shows yet another embodiment of part of a sterilization apparatus of the invention;  
       FIG. 4  shows yet another embodiment of part of a sterilization apparatus of the invention;  
       FIG. 5  shows a user wearing yet another embodiment of a portable sterilization apparatus of the invention;  
       FIG. 6  shows a longitudinal section through part of another embodiment of a sterilization apparatus of the invention;  
       FIG. 7  is a top view of the embodiment of  FIG. 6 ;  
       FIG. 8  shows a cross section through the apparatus of  FIG. 6  along the line A-A;  
       FIG. 9  shows a side view of the apparatus of  FIG. 6  connected to a mask shown in three dimensions;  
       FIG. 10  is a three dimensional view of another embodiment of a mask assembly of the invention;  
       FIG. 11  is a three dimensional view of another embodiment of a mask assembly of the invention;  
       FIG. 12  shows a block diagram of one embodiment of the electronic circuitry of the invention;  
       FIG. 13  is a three dimensional view of another embodiment of a kill chamber of the invention;  
       FIG. 14  is section through part of the embodiment of  FIG. 13 ;  
       FIG. 15  is a section through another part of the embodiment of  FIG. 13 ;  
       FIG. 16  shows one embodiment of a kill chamber and power supply in duplicate, housed in a fanny pack,  
       FIG. 17  shows another embodiment of a kill chamber and power supply housed in a fanny pack,  
       FIG. 18  is a section through part of another embodiment of a kill chamber of the invention,  
       FIG. 19  is a section through part of yet another embodiment of a kill chamber of the invention,  
       FIG. 20  is a simplified cross section through one embodiment of a kill chamber of the invention,  
       FIG. 21  is a simplified cross section through another embodiment of a kill chamber of the invention,  
       FIG. 22  is a cross section through part of another embodiment of a kill chamber of the invention,  
       FIG. 23  is a simplified cross section through yet another embodiment of a kill chamber of the invention showing the use of a fan or blower,  
       FIG. 24  is a simplified cross section through part of yet another embodiment of a kill chamber of the invention showing the use of a fan or blower,  
       FIG. 25  is a simplified cross section through part of yet another embodiment of a kill chamber of the invention showing the use of a fan or blower,  
       FIG. 26 , shows a method of making a housing for a kill chamber,  
       FIG. 27  shows another method of making a housing for a kill chamber,  
       FIG. 28  shows an embodiment of a pair of gloves of the invention,  
       FIG. 29  shows another embodiment of a pair of gloves of the invention packaged in a sealed plastic bag,  
       FIG. 30  shows a pad for removing gloves used with the apparatus of the invention,  
       FIG. 31  shows a three dimensional view of a decontamination chamber of the invention,  
       FIG. 32  shows an embodiment of the side and back panels of the chamber of  FIG. 31 ,  
       FIG. 33  shows an embodiment of the upper and lower panels of the chamber of  FIG. 31 ,  
       FIG. 34  shows one embodiment of a support arrangement for supporting the apparatus and clothing items inside the chamber of  FIG. 31 ,  
       FIG. 35  shows a longitudinal section through part of yet another embodiment of a sterilization apparatus of the invention,  
       FIG. 36  shows a longitudinal section through part of yet another embodiment of a sterilization apparatus of the invention,  
       FIG. 37  shows a longitudinal section through part of yet another embodiment of a sterilization apparatus of the invention, and  
       FIGS. 38-44  show longitudinal sections through parts of three other embodiments of a sterilization apparatus of the invention 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As mentioned above, the present invention defines an air supply system providing an air stream, the system including a filter and a means for moving the air, e.g., a pump, fan, or blower, as well as means for controlling either the flow rate of the air stream or the air pressure. In contrast, prior art devices make use of constant high flow rates which prevents use of good HEPA filters due to the large pressure drop. Also, they produce a large positive pressure causing constant expulsion of air and are therefore typically used with visor-like masks that allow air to freely pass from the mask. Since they are not on-demand systems they will potentially expose the user to more contaminated air. The present invention, on the other hand, makes use of a controlled air flow system to avoid these drawbacks. The embodiments of the present application, further include means for killing or destroying organic contaminants in the air stream by radiating the air stream with UV radiation.  
      For ease of understanding some of the concepts and elements that will be discussed with respect to  FIGS. 37-40 , the present invention includes embodiments and description from earlier filed applications that the present application claims priority from. One such previously discussed embodiment of a portable air sterilization apparatus of the invention is shown in  FIG. 1 , which shows a face mask  100  connected to a kill chamber  110  by means of a flexible delivery tube  120 . The face mask  100  includes a one-way intake valve  122  and a one-way exhaust valve  124 . The face mask  100  fits over a person&#39;s nose and mouth with the exhaust valve  124  sending the exhaled air into the atmosphere. The intake valve  122  allows the person to inhale sterilized air. The one-way valves  122 ,  124  ensure that the person breathes sterilized air while eliminating the used air to the atmosphere. As will be discussed in greater detail below with respect to  FIGS. 37-40 , the embodiments of the present invention include the possibility of radiating the exhaled or used air with UV radiation instead of simply venting it to the atmosphere. Valves  122 ,  124  may be simple flapper valves, over center flapper valves, or electrically actuated valves. In one embodiment, the valve open area was chosen correspond approximately to the cross-section of a human trachea (about 3-5 cm 2 ). The delivery tube  120  which is preferably made of a flexible material is chosen to have a similar cross-section (3-5 cm 2 ). In a preferred embodiment, the mask  100 , valves  122 ,  124 , and delivery tube  120  are designed to be removable from the kill chamber or sterilizer chamber  110  to facilitate washing, and are preferably made of a dishwasher safe material. By providing for quick release connectors or otherwise providing connectors that allow the kill chamber, delivery tube or hose, and face mask to be readily separated from each other, the various parts allow for easy exchange of worn out parts or use of components from another apparatus. In one embodiment, the apparatus may include eye protection such as glasses or goggles, or a flip-down transparent visor as indicated by reference numeral  130 . The visor  130  of this embodiment includes a heads-up display and a receiver  190  for receiving external feed for displaying information on the display  130 . The receiver  190  may be a wireless receiver e.g. a WiFi receiver for receiving wireless Internet feed or cached content information feeds. In the embodiment shown, an air pump  170  is included in the chamber  110  to provide a positive pressure within the mask  100  thereby ensuring that the surrounding air is not inadvertently drawn into the mask  100  along its sides where it abuts the user&#39;s face. The pump  170  also serves to ease the inhaling process by providing an air flow toward the mask  100 . One such pump is a diaphragm pump, e.g. 7010/−2.2N DC 12V and 24V produced by Rietschle Thomas of Sheboygan, Wis. Instead of pushing air directly to the mask, the pump, in another embodiment my supply a supply tank which then feeds the face mask via an appropriate regulator at the mask or tank.  
      In this embodiment, the sterilizer or kill chamber  110  has an internal volume corresponding approximately to one human breath of an adult under moderate exertion. (The typical breath of a resting adult is about 0.5 liter and under moderate exertion volumes will typically increase to 1 and 1.5 liters for a typical adult.) However, as is discussed in greater detail below, flow rate through the chamber is monitored to ensure that larger breaths and rapid breathing may be taken into consideration. The invention is not, however, limited to such an arrangement. As is discussed below, in other embodiments the chamber volume is specifically chosen to be smaller than an average breath of a typical user of the apparatus. In the present embodiment the kill chamber  110  is tubular in shape with a diameter of approximately three inches (3″) and six to eight inches (6-8″) in length. A UV light source  140  is mounted in the chamber  110 . In one embodiment the UV light source is a mercury vapor lamp mounted by means of brackets (not shown) to extend substantially along the center of the chamber. In the embodiments using a mercury vapor lamp as the UV light source, the lamp is protected in a quartz sleeve to reduce the likelihood of breakage. Also, a sensor  172  is included to monitor the output of the mercury vapor lamp and close a valve  174  to the mask  100  if the lamp stops radiating. This will ensure that no noxious gases from the lamp, nor untreated air is passed into the user&#39;s lungs. Preferably multiple UV sensors are includes since they tend to degrade over time. Therefore multiple sensors to monitor the amount of UV radiation are beneficial in ensuring that the UV source produces sufficient UV. The sensor  172  can be a photodetector made from AlGaN, SiC, AlN, GaN, InGaN, AlInGaN, GaAs, Si, or AlN:SiC alloys. Preferably the photodetectors are filtered to cut out wavelengths that are not cut out by the earth&#39;s ozone layer (currently 280 nm and above), either by means of an on-chip deposited filter, e.g. doped SiO 2 , or by means of a separate filter such as those sold by the company Schott in Mainz, Germany. The filtering ensures avoiding incorrect readings caused by extraneous UV interference. Preferably additional photodetectors clipped at 400 nm are included that measure light above 400 nm (visible light) to ensure that there is no light leakage into the chamber. This ensures that there are no gaps in the chamber that would allow UV light to escape. In the case of a mercury vapor lamp as UV light source, instead of monitoring UV light using a photodetector, the sensor  172  can instead simply be a current sensor for monitoring current through the lamp.  
      It will be appreciated that the dimensions of the chamber  110  may vary depending on the nature, size, and configuration of the UV light source. The inner surface of the chamber  110 , in this embodiment, is coated with a UV reflective coating, such as aluminum with a silicon dioxide protective coating so that radiation from the UV light source  140  will pass through the air in the chamber multiple times. Such reflective coatings have been found to produce 95% reflectivity of UV radiation. It will be appreciated that the UV source  140  may instead comprise a single or an array of UV light emitting semiconductor devices such as LEDs generating UV light. A wavelength of two hundred sixty to two hundred sixty-five nanometers (260-265 nm) has been found to be effective in killing or rendering harmless biological contaminants such as viruses, bacteria, and fungi.  
      The UV light source in this embodiment is powered by means of a power source which, in this embodiment, comprises a battery pack  142 . The power source  142  may include a DC to AC converter to facilitate the provision of 120 volts AC or more for powering a mercury vapor lamp from a battery such as a 10 volt DC battery. It will be appreciated that the power supply will include appropriate ballasting circuitry. In the case of LEDs being used as the UV source, the power source will provide the appropriate LED current by means of an appropriate DC voltage converter or through the use of optimized circuitry for LEDs as produced by MAXIM. The battery pack constituting the power supply  142  in this embodiment is packaged integrally with the chamber and includes a charger for the battery pack. However, it will be appreciated that the battery pack could also be separately housed and carried, for example, on a user&#39;s belt. It will be appreciated that not only the kill chamber with its sensors and battery pack could be carried separately, but any other elements that are not required to be on the mask  100  could also be carried separate from the mask, e.g., in a backpack, shoulder bag, etc. Thus, for example any cell phone, AM/FM radio, walkie-talkie, or visor information receiver or could be housed carried in a backpack with the kill chamber  110 .  
      The present invention seeks to conserve power while ensuring effective destruction of harmful organic material. In order to conserve power, rate of airflow through the chamber  110  is monitored by means of a flow meter  144 , which may be a mechanical flapper, pressure sensor across a venturi, an anemometer, or a mass flow meter. The mass flow meter element produced by MKS Instruments essentially comprises a wire loop that is heated by passing current through it and for which changes in current flow are monitored in order to maintain a substantially constant temperature wire loop. Thus, faster airflow, which will cause greater cooling will require greater current to maintain the temperature of the loop, thereby providing a simple way of measuring air flow rate. It will be appreciated that ambient temperature changes will affect the reading of the mass flow meter. The present embodiment therefore makes use of a second mass flow meter  145  that is exposed to the same ambient temperature but placed in a housing to avoid exposure to air flow, thereby acting as a control device. The differences in reading between the two flow meters will therefore represent a flow rate change. A controller in the form of a microprocessor  146  is connected to the sensor or flow meter  144  to monitor air turnover in the chamber  110  and adjust the UV dosage. The amount of UV radiation to which the air in the chamber  110  is exposed is adjusted by adjusting the radiation source. In one embodiment, a bank or matrix of UV LEDs was switched on and off according to a duty cycle as defined by the microprocessor  146 . In addition, in another embodiment, the microprocessor  146  controlled the intensity of some or all of the LEDs in a bank or array of LEDs. In yet another embodiment, the microprocessor  146  selected the number of LEDs that needed to be switch on in order to account for changes in flow rate. It will be appreciated that a combination of two or more such power changes to the LEDs can be implemented.  
       FIG. 1  also shows a filter  150  provided at the air intake  152  to the chamber  110 . The filter  150  reduces the absolute number of living microbes or pathogens that enter the chamber  110  and may have wicking properties or absorbing properties to help reduce the amount of water vapor in the air entering the kill chamber, thereby allowing the UV source to more effectively kill the pathogens in the air  
      The filter  150  also reduces microbes, dust, or mold entering the chamber  110 , thereby reducing contaminants from settling on the chamber&#39;s reflective inner surface and compromising its reflective qualities. Since UV light can increase the production of ozone (O 3 ) and carbon monoxide (CO), the present invention seeks to both monitor and limit the levels of ozone and carbon monoxide. Ozone production can be limited by optically filtering out one hundred eighty-five nanometer (185 nm) UV. Philips, for example, produces a mercury vapor lamp that provides such filtering by providing a titanium-doped glass (type 219 or 230) The carbon monoxide level can be reduced by providing a titanium dioxide layer for chemically reacting with carbon monoxide to produce carbon dioxide (CO 2 ). In order to avoid the carbon monoxide catalyst material from interfering with the reflective coating material in the chamber  110  the carbon monoxide catalyst is preferably provided in a separate section such as the delivery tube  120  or a portion of the chamber  110  near the outlet  154 .  
      Yet another portion of the chamber  110  may be coated with a catalyst layer such as titanium dioxide (TiO 2 ) which promotes the breakdown of carbon compounds in the presence of UV light, thereby enhancing the kill effectiveness of the apparatus.  
      The present invention further includes sensors  160 ,  162  for monitoring ozone levels and carbon monoxide levels, respectively, in the chamber  110 . The signals from the sensors  160 ,  162  may be sent to a visual display. Preferably, an auditory alarm is included for notifying the user if carbon monoxide or ozone levels exceed a predefined level. In one embodiment, a battery-charge monitor was also included to monitor the amount of battery charge left in the battery pack of power supply  142  and to notify the user both visually and by means of an audible alarm if power levels drop below a predefined minimum charge. As discussed above, this embodiment also includes a UV radiation sensor  172  to detect UV generation failure. The sensor  172  and possibly additional UV sensors also serve to monitor UV radiation and allow adjustment to meet an adequate dose without generating excessive undesirable byproducts. Since the effectiveness of the radiation source is effected by humidity conditions, the present embodiment includes a humidity sensor  192  connected to the controller  146  for controlling the amount of UV radiation pursuant to humidity changes.  
      As shown in  FIG. 1 , the mask  130  also includes a microphone  180  to facilitate communication. In order to allow the user to readily use a cellular phone, a cell phone speaker  182  is included in the mask  130  and is either connected to or connectable to a cell phone speaker/ear piece  184 . In this embodiment, the mask  100  also includes a walkie-talkie microphone  186  connected to a walkie-talkie speaker  188  to facilitate communication with other workers. The kill chamber  110  also includes an AM/FM radio to allow the user to listen to public announcements and entertainment channels.  
      Another embodiment of the invention is shown in  FIG. 2  in which the chamber  200 , instead of having a linear passageway has a wavy passageway to promote turbulent airflow between the inlet  202  and the outlet  204 . This ensures that air exposure to the surfaces of the chamber are increased, thereby increasing the effectiveness of the carbon monoxide catalyst. It will be appreciated that the wavy chamber configuration is particularly important in the section of the chamber that is provided with the carbon monoxide catalyst and may, in fact, be limited to this section only.  
       FIG. 3  shows yet another embodiment of the invention in which baffles  300  are provided in the kill chamber  302  thereby again providing turbulent airflow between the inlet  304  and the outlet  306 .  
      Yet another embodiment is shown in  FIG. 4 . Here the chamber is divided into narrow passageways  400 , each with ultraviolet LEDs  410 , thereby ensuring more uniform exposure of the air in the chamber to ultraviolet radiation.  
      An alternative configuration for the mask and kill chamber is shown in  FIG. 5 , in which the mask  500  is connected by a flexible delivery tube  502  to a helmet-mounted kill chamber mounted on or integrally formed. In this embodiment, the kill chamber is integrally formed into a helmet  504 . It will be appreciated that in another embodiment the chamber could-merely be attached to an outer surface of a helmet such as a bicycle helmet.  
      It will be appreciated that the battery pack, instead of being packaged into the helmet  504 , may be attached to the user&#39;s belt, or to the user&#39;s chest, or slung like a purse over the user&#39;s shoulder, or carried like a backpack on the user&#39;s back, or carried on the user&#39;s hips in a hip pouch (fanny pack) arrangement as discussed further below with respect to  FIG. 16-17 .  
      Part of yet another embodiment of the invention is shown in  FIG. 6 , which includes a UV housing or kill chamber  600  connected to a power supply  602  by means of flexible electrical connectors  604 . In this embodiment the power supply  602  comprises several batteries (not shown) housed in a housing  606 . Eight Lithium Ion batteries from Sanyo, producing 14.4 V and 64 W Hrs, and weighing 400 grams were used in this embodiment. In another embodiment twelve Nickel Metal Hydride (NiMH) batteries such as the HR-4/3 FAU 4500 were used in this embodiment. These produced 4500 mA hours each for a total of 54 W hours. Thus for approximately a 5W lamp, a 1 Watt air flow pump and some 0.2 W for supporting electronics, the power supply of this embodiment would provide about 8 hours of operation before requiring that the batteries be recharged. These batteries have an 18 mm diameter and are about 67.5 mm long, thus allowing them, in one embodiment, to be packaged into a housing  606  that is about 135 mm×36 mm×54 mm by placing three rows of two batteries on top of a second set of three rows of two batteries. It will be appreciated that other configurations and other types of batteries e.g., NiCd kRF 7000F batteries from Sanyo, or HR-4/3FAU4500 batteries could be used as the power supply  602 . In yet another embodiment, a plurality of 13-14 8.9 WHr, UR18650F cells made by Sanyo for providing a total of 115.7-124.6 WHrs were used to power a 9W mercury vapor lamp. It will, however be appreciated that other power sources, including power generators and rechargers could be used e.g., a 110-120 V or 220-240 V wall socket, a DC automobile socket, an AC or DC connection to an electrical supply on boats, ships, aircraft, or trains, a photovoltaic cell or array of cells, or a generator powered by wind, natural gas, propane, gasoline, diesel fuel, alcohol, steam or by man or animal power, e.g., making use of a bicycle or the peddling mechanism of a bicycle.  
      In the  FIG. 6  embodiment the housing of the kill chamber  600  is made of a 4.125 inch long, 2.5 inch inside diameter aluminum pipe or cylinder  608  with a wall thickness of 3 mm and, which is preferably polished on its inner surface to provide a highly UV reflective inner surface. The pipe  608  can even be exposed to a chemical vapor deposition (CVD) process to increase the reflectivity to about 95 percent for UV. Apart from its structural integrity, the aluminum also provides a good thermal conductor for heat generated by the UV lamp  670  and the electronics, which are discussed further below. The pipe  608  defines a housing by being provided with end plugs  610 ,  612 . The end plug  610  is fitted into the upper end of the pipe  608 . The pipe also receives a removable filter assembly  616 , which together with the end plug  610  will also be referred to as the end cap. The pipe  608  is provided with an outer thread on its upper, outer surface for complementarily engaging the filter assembly  616 . The filter assembly comprises a filter housing defined by a filter cap  618  having side walls  620  with an inner thread that engages the outer thread on the pipe  608 . The filter cap  618  houses a filter  622  and is closed off by a base plate  624 . The filter cap  618  has numerous small holes or air flow passages  626 , while the base plate  624  is provided with six 0.65 inch diameter holes  628 . In this embodiment the filter  622  is a 0.3 micron particle filter that is equivalent to the N95 3M NIOSH standard.  
      The upper end plug  610  is best understood with respect to the top view of the kill chamber shown in  FIG. 7 . The plug  610  is made of UV resistant material (e.g., Xylex materials X8210 or X7110 made by General Electric). It defines radial flow passages  630  joining at a central hole  632 . The hole  632  and passages  630  allow mercury vapor from the mercury vapor lamp  670  to be vented out of the kill chamber in case the lamp  670  breaks. As discussed further below and as shown in  FIG. 6 , the kill chamber includes a UV light source in the form of a mercury vapor lamp  670  and a fused quartz sleeve  678  that protects the lamp  670 . The sleeve  678  is held in position by the upper plug  610  by fitting into the central hole  632 , which, as shown in  FIG. 6  extends only partially through the plug  610 . The plug  610  is, however, provided with six 0.65 inch diameter holes  642 , which pass all the way through the plug and align with holes  628  in the base plate  624  for air flow into the kill chamber surrounding the sleeve  678 . The bottom end plug  612  supports the electronics of the air sterilization apparatus, which include a controller or processor, a voltage regulator, and sensor electronics, collectively indicated by reference numeral  650 . In this embodiment the plug  612  includes a printed circuit board (PCB) on which the electronics are mounted. The PCB also supports photodetectors  662  for detecting the presence of light with a wavelength greater than 400 nm (visible light), thereby indicating that outside light is penetrating the kill chamber and that the chamber is open to UV radiation leakage. Audible alarms  664  are also provided to produce auditory feedback on various sensor conditions, as is discussed in greater detail below. An electrical connector plug  668  with pins  669  is mounted into the end plug  612  for connecting the flexible electrical connectors  604 . As shown in  FIG. 6 , a UV lamp  670  mounted substantially along the longitudinal axis of the pipe  608  is electrically connected to the pins  669  of the connector plug  668  by means of electrical leads  672 .  
      The lamp  670  should provide about 8 W output and a 253.7 nm wavelength. In this case a G23-2 Pin lamp (PL-S5W/TUV) from Philips, which is a 5W lamp with a 1W output, is mounted on a UV resistant plastic plate  674 . The lamp  670  is provided with a ballast  676 . Wires  678  extend from a power controller to the ballast  676 . The plate  674 , which is cemented into the pipe  608  includes a plurality of holes  676  to provide air flow passages as shown more clearly in the sectional view  FIG. 8  through the apparatus along line A-A of  FIG. 6 . The lamp  670  is protected by a UV transparent tube, which in this case is a fused quartz sleeve  678 , which surrounds the lamp  670  and is secured between between the plug  610  and an annular groove  672  in the plastic plate  674  to define a lamp housing separate from the air flow region surrounding the sleeve  678 . The sleeve  678  of this embodiment has a 3 mm wall thickness, and in this embodiment both the lamp  670  and the sleeve  678  are made of 219 or 230 type, thus including titianium to eliminate the 185 nm line, which produces ozone. Other embodiments simply make use of the 219 or 230 type in either the mercury vapor lamp or the quartz sleeve. In order to ensure that there are no spots or regions in the mercury vapor lamp or quartz sleeve that remain untreated with titanium, the invention proposes that one or both of the lamp and quartz sleeve be supplemented with titanium. This may be done by adding a layer of titanium on the vapor lamp or quartz sleeve or both, by CVD or by implanting titanium e.g. by ion implantation into the vapor lamp or quartz sleeve or both.  
      As shown in  FIG. 6 , the kill chamber  600  also includes baffles  679  that are provided as annular plastic disks to promote turbulent air flowing for air flowing through the kill chamber. The annular plastic disks  679  are 0.7 inches thick and have a 1.75 inch diameter central hole.  
      In order to connect the kill chamber  600  with a face mask (discussed further with respect to  FIG. 9 ) the aluminum tube  608  has a hole in its wall with an outwardly extending flange  682  acting as a hose connector for connecting the hose that leads to the face mask. During use, air is drawn into the housing or chamber  600  surrounding the quartz sleeve  678  through the openings or holes  626  in the filter cap  618 , through the filter  622 , through the channels  628  in the base plate  624 , and through the holes  642  in the top plug  610 . The air is then irradiated by UV light from the lamp  670 , and passes out of the chamber through the hose connector  682  to the user&#39;s face mask. The hose connector  682  includes a quick disconnect for readily disconnecting the hose from the chamber by depressing two tabs or buttons (not shown) on opposite side of the connector for releasing the hose.  
      As shown in  FIG. 6 , various sensors are mounted on the inner wall of the tube  608 . These include UV sensors in the form of photo detectors  684  for sensing whether and how much UV is being put out by the lamp  670 ; thermistors  686  acting as hot wire air flow sensors; ozone sensors  688 ; CO sensors  690 ; accelerometers  692  for measuring any unwanted jarring or dropping of the apparatus which may have damaged the apparatus. The various sensors are electrically connected to the controller or processor  650  for monitoring the conditions and providing auditory feedback by means of the audible alarms  664  if predefined conditions are not met. For instance, a look-up table can pre-define suitable operating ranges and the controller or processor, which can be a microcontroller, can monitor the sensors and compare the sensor signals to the predefined values or ranges for signaling an alarm if the predefined values or ranges are not met. The audible alarms  664  can, for example, include an audible output generator such as a beeper or voice generator. In addition to the audible alarms, visual alarms, e.g., in the form of LEDs may be attached to an outer container or housing in which the kill chamber is carried.  
      A block diagram of one embodiment of the electronics is shown in  FIG. 12 , including the microcontroller, the sensors and the power supply control circuitry for the microcontroller, an air pump (as is discussed in greater detail with respect to  FIG. 8 ) and a mercury vapor lamp as used in the  FIG. 6  embodiment. As shown in  FIG. 12 , this embodiment includes a battery monitor and charge controller chip to avoid overcharging of the batteries in the battery pack that serve as the power supply for the apparatus.  
       FIG. 9  shows the apparatus  600  with its power supply  602  connected to a mask  900  by means of a flexible pipe or tube  902 , which in this embodiment is a ⅝ inch diameter plastic pipe. However, tube diameter and length are preferably adjusted to accommodate size differences and breath volume and breath frequency differences found in children, women and men. The mask  900  covers only the user&#39;s nose and mouth and includes a flapper valve  910  for allowing exhaled air to be vented to the atmosphere. The connector or flange on the mask  900  for connecting the hose, or tube  902  includes a quick disconnect requiring two tabs or buttons (not shown) to be depressed on opposite side of the connector for releasing the hose  902 . The connector also includes a flapper valve  912  that is spring loaded to bias the valve  912  to a closed position so that the valve  912  is closed when the user exhales to ensure that carbon dioxide rich air is vented to the atmosphere rather than back into the apparatus  600 . As shown in  FIG. 8 , the apparatus  600  also includes an air pump  920 , which in this case is a microdiaphragm air pump providing 4-6 standard liters per minute (SLM) at one atmosphere pressure (14.7 pounds per square inch). The pump  920  has an input tube  922  entering the hose connector or flange  682  of the aluminum tube  608  through a hole in the wall of the flange  682 . The output from the pump  920  is connected by means of a pipe  924  to the mask  900  by passing through the wall of the flange or hose connector  682  and extending along the inner surface of the tube  902 , through the valve  912 , and into the face mask  900 . In another embodiment, to avoid interfering with the valve  912 , the hose  924  may pass out of the pipe  902  near the top of the tube  902  and into the mask In this embodiment the pump  920  is a low pressure pump (e.g. 0.5 to 1.0 inches of water) serving merely to assist the user in breathing and being insufficient to open the valve  912  to the mask  900 . In another embodiment the pump  920  is a higher pressure pump (e.g., 1 to 2 inches of water) that not only assists in the breathing process but also forces the valve  914  open and creates a positive pressure in the mask  900  to provide an extra precaution against the ingress of untreated air into the mask  900  along the mask periphery. The higher flow pump also ensures consistent flow rate through the kill chamber. It will be appreciated that by appropriately choosing the tube  902  diameter and length the diaphragm pump  820  can optionally be eliminated altogether, thereby limiting cost and power consumption. It will also be appreciated that by connecting the pump as shown in  FIG. 9 , natural air flow is not restricted should the pump ever fail.  
      The invention also proposes including a port or connector to the kill chamber, mask or connecting hose or tube for introducing external substances, e.g. inhalants, nebulizers or atomized medicinal substances. One type of connector would be a pump canister receptor as is commonly known for pump action dispensers. A pump canister connector  950  is, for instance, shown in  FIG. 9 .  
      In order to provide an apparatus usable in rural areas or areas where power supplies or charging facilities are not readily available, one embodiment includes a manually operated power source e.g. a hand cranked generator that either charges a set of batteries or directly powers the UV source and other electronics. Such hand cranked generators are currently being used in devices such as portable radios and flashlights.  
      In the  FIG. 9  embodiment, in which the mask  900  covers only the nose and mouth, the user will typically wear safety glasses or goggles to protect the eyes. In another embodiment, shown in  FIG. 10 , the mask assembly  1000  includes goggles  1002  having scratch resistant plastic lenses and provided with a UV coating, thereby allowing the user to enter a UV decontamination chamber without fear of damaging his or her eyes. In order to avoid subsequent contamination of the user after use of the apparatus, some or all of the face mask and goggles may be made to be disposable or may be made from a UV resistant material or covered by a UV resistant coating to permit decontamination of the face mask and goggles in a UV decontamination chamber. Instead, if the face mask and goggles are intended for decontamination by means of a chemical agent such as bleach (e.g., Clorox), the mask and goggles may be made of a material resistant to such chemical agent.  
      In yet another embodiment, shown in  FIG. 11  the mask  1100  again covers only the mouth and nose, but in this embodiment the system includes goggles  1110  that seal to the user&#39;s face and are provided with a separate air tube  1112  that is fed by an air pump such as the diaphragm pump  920  or by a separate air pump that pumps UV treated air.  
      While the embodiment of  FIG. 6  makes use of a mercury vapor lamp  670 , the UV source could also be provided by LEDs as shown in  FIGS. 13-15 . For instance, InAlGaN LEDs with a dominant wavelength of 265 nm were used in one embodiment. Sources vary somewhat in calculating the exact amount of radiation required in order to kill avian flu, for instance. One approach is based on energy per unit area required to destroy DNA or RNA. Using this approach, 6600 uWsec/cm 2  is required to achieve the desired destruction of DNA or RNA. Typically an adult at rest will take 10 breaths/minute, thus providing a 6 second chamber time for each breath (assuming flow is not controlled by an air flow pump). A tubular light source providing 1.0 watt of UV radiation located concentrically in an 8 cm diameter tube that is 16 cm long will provide a radiation intensity at the cylindrical wall surface of 1/804=1243 uW/cm 2  since the wall has a surface area of 804 cm 2 . This intensity over six seconds will provide a radiation dosage at the wall of 7458 uWsec/cm 2  for each breath. Thus a 1.0 W output source will provide a safety factor for kill of about 7460/6600=1.13. This calculation underestimates the average dosage level. The average dosage will be higher due to greater radiation intensities closer to the bulb and reflection of radiation from the wall. For example, if 95% of the radiation is reflected from the wall, then average dosage at the wall will be at least 7458*1.95 or 14543 uWsec/cm 2  or a safety factor of at least 2.2. An LED will produce about 1 mW output. Thus the source would need about 1000 LEDs to provide the 1.0 W output considered above if the LEDs are arranged in a cylindrical array. If a safety factor of approximately 1.0 were considered sufficient, or if linear arrays were used such that the LEDs illuminate a long, reflective light path then many fewer LEDs would suffice. At 40 mA per LED, 1000 LEDs would draw 40 A of current and at 6V would require approximately 240 W of power. It will, also, be appreciated that the need for an accelerometer to monitor shocks that might damage a non-LED UV light source such as a mercury vapor lamp will be less critical when UV LEDs are used. In this embodiment the bank of LEDs  1400  is mounted along one or more of the inner walls of a rectangular housing  1300  as shown in  FIG. 13 . The two main sides  1310  of the rectangular housing  1300  are made of double sheets of aluminum  1410  shown in  FIGS. 14 and 15 , which fit into slots in UV resistant plastic panels  1320  forming the narrow sides of the housing. The ends  1330  of the housing are also made of UV resistant plastic and also receive the aluminum plates  1410  in slots. As shown in  FIGS. 14 and 15 , the UV LEDs  1400  are mounted in cups  1420  between the outer aluminum plate  1410  and the inner aluminum plate  1412 , which is polished, is provided with holes to expose the cups  1420 .  
      As discussed above, the kill chamber and power supply can be carried in a fanny pack or hip pouch. Two embodiments of such a fanny pack arrangement are shown in  FIG. 16-17 .  FIG. 16  shows dual battery packs  1600  constituting the power supply, and dual kill chambers  1602  housed in a fanny pack  1604 . The dual nature of the kill chambers and battery packs provides for redundancy in case of failure of one or other of the components. In addition, both the battery packs  1600  and kill chambers  1602  are protected by annular foam disks  1610 . The foam discs  1610  also serve to space the battery packs  1600  and kill chambers  1602  from the wall of the fanny pack for better air flow past the battery packs and kill chambers. The battery packs and kill chambers are secured relative to the fanny pack walls by means of elastic bands  1670  attached to the inner walls of the fanny pack. The kill chambers  1602  have their air inputs in flow communication with the outside by providing holes on opposite sides of the fanny pack  1604  and mounting the chambers  1602  by means of brackets  1630 . In this embodiment, the battery packs  1600  are cooled by cooling exhaust feed lines from two micromotors with fans  1640 , which are mounted between two plastic supports  1662  that are 2 inches in diameter. The embodiment of  FIG. 16  also includes shut-off valves  1650  controlled by the controller of the kill chamber electronics. The valves  1650  close the tubes  1652  leading to the mask (not shown) in the event that a mercury vapor lamp breaks, i.e., if the UV detectors detect no UV radiation from a particular UV lamp. Also, if failure or inadequate UV radiation is detected, e.g., if the UV photodetectors detect no UV radiation within one or both of the kill chambers or the radiation level falls below a predefined level, alarms can be activated. As mentioned above, alarm conditions can be both visually and audibly identified. In this embodiment, LEDs  1660  are mounted on the fanny pack to provide the user with visual alarm information. Here several LEDs are provided, with different colors to provide different types of information. For instance, a green, amber and red LED can be provided for the kill chamber to indicate that the unit is good to use, or that the pump is down, or that no UV is being generated, respectively. Similarly, a green, amber and red LED can be provided for the battery pack to indicate, for example, that the battery pack is adequately charged (more than ½ hour left), or has less than ½ hour left, or has less than 5 minutes left, respectively. Regarding the shut-off valve, it will be appreciated that the shut-off valve  1650  is not necessary where the UV light source is provided by a bank of UV LEDs. Also, by providing the connection between the tube  1652  and the face mask as a separable connection and providing the connection with a quick release connector, e.g. oppositely positioned depressable tabs on the connector, the tube can readily be removed in the event that the shut-off valve  1650  is closed. In one embodiment the fanny pack includes a pouch or Velcro patch for holding a snap-on particle filter that is attachable to the face mask using a similar quick-release connector, once the tube  1652  is removed. One feature of the invention is to provide quick release connectors such as the depressable tab or depressable button connectors described above or other connectors that allow the kill chamber, delivery tube, face mask, and filter to be readily separated, thereby defining a modular apparatus that allows parts to be exchanged or replaced. In the  FIG. 16  embodiment the fanny pack  1604  is made from waterproof material on its top and sides for helping to contain any mercury vapor in the event of a mercury vapor lamp breakage. The fanny pack  1604 , however, is provided with a mesh bottom portion to help with air circulation and cooling of the battery packs  1600  and kill chambers  1602  and to provide visible light to the kill chamber, thereby allowing the photodetector  662  ( FIG. 6 ) to monitor visible light entering the chamber, which would indicate a leak constituting a UV radiation hazard.  
      Another embodiment of the fanny pack arrangement is shown in  FIG. 17 . In this embodiment there is no redundancy shown, but the power supplies  1700  and kill chambers  1702  are again mounted in parallel. The battery pack  1700  and kill chamber  1702  are protected by annular foam disks  1710 . The foam discs  1710  also serve to space the battery pack  1700  and kill chamber  1702  from the wall of the fanny pack for better air flow past the battery packs and kill chambers. The battery packs and kill chambers are secured relative to the fanny pack walls by means of elastic bands  1770  attached to the inner walls of the fanny pack. The kill chambers  1702  have their air inputs in flow communication with the outside by providing holes on opposite sides of the fanny pack and mounting the chambers  1702  by means of brackets  1730 . In this embodiment, the battery pack  1700  is cooled by cooling exhaust feed lines from micromotor with fan  1740 , which is mounted next to a plastic support  1762  that is 2 inches in diameter and acts as a spacer between the power supply and the fanny pack. The embodiment of  FIG. 17  also includes shut-off valves  1750  controlled by the controller of the kill chamber electronics. The valves  1750  close the tubes  1752  leading to the mask (not shown) in the event that a mercury vapor lamp breaks, i.e., if the UV detectors detect no UV radiation from a particular UV lamp. Also, if failure or inadequate UV radiation is detected, e.g., if the UV photodetectors detect no UV radiation within one or both of the kill chambers or the radiation level falls below a predefined level, alarms can be activated. As mentioned above, alarm conditions can be both visually and audibly identified. In one embodiment, the battery backpack  1700  was made detachable from the rest of the apparatus to permit replacement with a new battery pack. In another embodiment, the batteries in the backpack were arranged for easy access and sliding contacts mounted in the backpack for easy removal and replacement of the batteries in the backpack of the battery backpack  1700 . In addition, in one embodiment, an electrical access cable to the batteries was provided for charging of the batteries at any suitable electrical outlet when the user was not moving around.  
      While the flexible connector hose  902  of  FIG. 9  was a circular cross-section hose, other embodiments are also proposed by the present invention. For instance, a low profile rectangular, non-collapsible, yet flexible airline could be used instead. This could be worn beneath clothing and connect to the side of the mask to reduce snagging.  
      In order to protect UV LEDs against back reflection of UV light, one embodiment of the invention, shown in  FIG. 18  includes polarized glass lenses  1800  covering the LEDs  1802  that are attached to the kill chamber housing wall  1804 . As in the  FIG. 14  embodiment, the LEDs  1802  are housed in cups  1806  mounted in holes in an inner aluminum wall  1808 . In this embodiment, in addition to a highly reflective coating  1810  (which will be discussed in greater detail below) the inner aluminum wall is provided with a coating  1812  that is transparent to UV hand has a high refractive index. This has the effect of bending the incident UV light away from the normal to the surface and thus increases the reflective effect by reflecting the light at a greater angle than the angle at which it came in.  
      Another embodiment for protecting the LEDs against UV light is shown in  FIG. 19  in which the LEDs  1900  mounted on the aluminum housing wall  1902  are separated from the air flow chamber  1904  by a polarized, UV transparent tube  1910  (in this case a glass tube).  
      Since light power density diminishes by the square of the distance from a point source of light and by 1/d for an array form of light emitter such as a linear cylindrical tube, it is desirable for maximum killing capacity, to have air flow within the kill chamber pass as close to the UV light source as possible to ensure that biological contaminants are exposed to sufficient light power. One embodiment for a housing for achieving this purpose in the case of a kill chamber with a central mercury vapor lamp is shown in  FIG. 20 , which shows the housing in non-cylindrical form. Along the length of the mercury vapor lamp  2000  the housing  2002  has a narrowed or constricted portion  2004  to ensure air flow close to the mercury vapor lamp  2000 .  
      In another embodiment, shown in  FIG. 21 , a cylindrical housing  2100  is adapted to provide the constriction by including an annular baffle  2102  that surrounds the UV light bulb  2104 .  
      In the case of a kill chamber that makes use of UV LEDs as the light source, such as the embodiment shown in  FIG. 19 , air flow close to the light source is ensured by including a central baffle  2200  as shown in  FIG. 22 .  
      While the above embodiments of the kill chamber of the invention have discussed the use of a pump to provide or supplement air flow to the face mask, air flow may instead be provided by making use of a fan or blower as shown in  FIG. 23 . In one embodiment a centrifugal blower was used, in particular a GB1205PKV1-8AY by Sunon (www.sunon.com) available from Jameco. In  FIG. 23  the kill chamber is shown in simplified form and depicted generally by reference numeral  2300 . While the mercury light bulb  2302  and baffle  2304  are shown the filter cap detail and light bulb connector are left out for simplicity. In this embodiment a fan or blower  2310  is provided in a housing  2312 , which is in flow communication with the inside of the kill chamber  2300  and a hose  2320  that leads to the face mask (not shown). In accordance with the definition provided above, the fan may be mounted directly in the housing  2312  or may include its own housing, thereby defining a blower that is mounted in the housing  2312 .  
      The blower or fan  2310  in this embodiment is implemented as a constant flow arrangement in which the flow rate remains substantially constant whether the user inhales or exhales. The constant flow arrangement includes a control valve, which may simply be a mechanically adjustable valve to achieve the desired flow e.g. manual butterfly or gate valve, but in this embodiment is an electrically controllable valve  2320  that is controlled by a signal obtained from a flow transducer (eg., based on a Venturi pipe).  
      As shown in  FIG. 24 , the blower or fan  2400  may instead be implemented as a constant pressure arrangement in which the flow rate varies as the user inhales or exhales, but pressure is adjusted to maintain substantially constant pressure. This may be achieved by measuring the pressure behind a one-way valve e.g., by measuring pressure behind a flapper valve  2402  electronically using a solid state pressure transducers  2404  and varying the flow of air provided by the fan or blower by varying current to the fan or blower  2400 . This constant pressure arrangement may be used not only to control a fan or blower but may also be used for controlling air flow provided by a pump (which typically uses about 11 W to produce 20 standard liters per minute (SLM)). In contrast a fan or blower uses only about 1-2W to produce 80 (SLM).  
      Instead of controlling current to the fan or blower or to the pump, the flow rate can be adjusted for constant pressure by varying the position of an electrically-controlled valve or shuttering mechanism, referred to herein as a control valve, such as a butterfly valve, or gate valve etc., that is located in the delivery tube or at the output side of the fan, blower, or pump or at the inlet to the face mask. Such a valve mounted at the output of the kill chamber is shown in  FIG. 24  and depicted by reference numeral  2410 . In another embodiment the valve was mounted in the delivery tube itself. The valve may include a latch, e.g., a magnetic latch to reduce electric power consumption by the valve. Nevertheless, it will be appreciated that if constant pressure is maintained using only an electrically actuated valve such as the valve  2410 , the blower, fan or pump may be wasting energy by blowing or pumping more than required, and may create excessive pressure of the inlet air. Thus control of the blower, fan or pump current is advisable. As part of the modular nature of the preferred embodiment, the pressure sensor is preferable releasably connected. For simplicity, in another embodiment instead of electronically controlling the shuttering mechanism or control valve  2402 , the invention may be implemented by using a mechanical shuttering mechanism or control valve  2500  as shown in  FIG. 25 , e.g., a spring loaded valve that opens up at defined pressure. Preferably a controlled leak is provided into the mask to ensure positive pressure e.g. 0.5 SLM. The controlled leak may be implemented by forming a hole  2412  or  2502  in the valve  2402  or  2500 , respectively. One advantage of a constant pressure implementation is that during low flow rates (e.g. during exhaling or lower user activity) any biohazards such as viruses entering the chamber continue to be radiated for longer periods of time. It will be appreciated that in embodiments where the control valve also acts as shut-off valve in the event of UV lamp breakage, the control valve does not have a hole  2412 ,  2502 . Instead, the control valve is simply controlled to remain slightly open at all times except when UV lamp breakage is detected.  
      Another embodiment of a kill chamber according to the invention is shown in  FIG. 35 . The kill chamber  3500  includes an aluminum housing  3501  made of two halves  3502  with outwardly extending flanges  3504 . In this embodiment, the aluminum halves are made using 0.1 inch thick aluminum sheets with a UV reflective coating comprising 0.5-1 μm thick sputtered Al and 0.5 μm thick SiO 2  using a rocker during sputtering. The aluminum sheets were pressed into shape using a polished steel tool and die. The flanges, in this embodiment, are provided with internally threaded holes  3506  for receiving complementarily threaded screws. It will be appreciated that the holes could instead have a smooth inner surface, in which case the two halves could be held together by bolts and nuts. In addition, a high temperature vacuum sealant or glue is provided between the opposing flanges to ensure an air-tight seal. The top of the housing is partially closed by a disk  3510 , which in this embodiment is formed from a Pyrex dielectric stack with a 250-270 nm wavelength high reflectivity coating. The disk  3510  includes a central hole  3514  defining an air inlet to the chamber  3500 . The disk  3510 , in this embodiment is held in place by a UV resistant plastic ring  3512  made by General Electric (GE), which extends by about 0.125 inches above the rim of the aluminum chamber housing to define an air space as is discussed in greater detail below. The ring  3512  is provided with outer threads along its upper surface for receiving a filter cartridge discussed in greater detail below. The plastic of the ring  3512  has the advantage that it is UV resistant and does not absorb water.  
      The filter in this embodiment comprises an annular or doughnut-shaped N100 filter cartridge which includes a plastic cap  3522  made from GE ultraviolet resistant plastic. The cap  3522  supports a central annular filter element  3520 . The central portion of the annular filter element  3520  is, in turn, closed off by a central circular plastic disc  3524  having a MgF 2  or other reflective coating  3525  on its lower surface.  
      The cap  3522  includes side walls  3526  with inner threads allowing it to be screwed onto the top of the chamber housing by engaging complementary threads on the outer surface of the chamber housing  3501 . The plastic ring  3512  also has grooves on its outer upper surface for engaging the threads on the side walls  3526  of the cap  3522 . Once attached, the cap  3522  defines a gap or space between itself and the disk  3510  due to the ring  3512  which extends above the rim of the aluminum housing. Air passing through the filter  3520  therefore passes through this gap to the air inlet  3514 .  
      The air then passes into the chamber, which in this embodiment has a volume of 0.86 liters and a 380 cm 2  surface with average reflectivity for UV of 90%. The mercury vapor lamp  3530  in this embodiment is either a 5W or 9W single connector UVC bulb with 185 nm line suppressed. The lamp  3530  is surrounded at its lower end by a 1.25 inch diameter SiO 2  sleeve or tube  3532  that is 1-5 nm thick, has an aluminum coating that is 500-3000 Angstrom thick. The tube  3532 , which can also be made of other reflective material e.g., polished aluminum to channel the UV rays, is supported in a groove formed in a UV resistant plastic disk  3535  which supports an aluminum disk  3534 . The sleeve  3532  is secured in the groove by means of a high temperature sealant.  
      The lower end of the aluminum housing  3501  is closed off by means of a plastic cap  3540  made of GE UV resistant plastic with 0% water absorption, and which has a central hole for receiving the lamp  3530 . Vertically extending holes  3548  are also formed the plastic cap  3540  and aluminum disk  3534  to channel air from the chamber to horizontally extending holes  3550  formed in the plastic cap  3540  and in the walls of the housing  3501 .  
      Yet another embodiment of a kill chamber of the invention is shown in  FIG. 36 , which makes use of a housing  3600  in which both the air inlet and outlet are formed at the same end  3602 . As in the previous embodiment, the kill chamber in this embodiment is made in two sections from 0.1 inch pressed aluminum that are formed into cylinder halves using tool and die. For ease of description, the flanges are not shown in this embodiment. The kill chamber in this embodiment, however, is divided into concentric channels by means of a quartz tube  3604  that surrounds the double connector 6W LVC bulb  3610 . The air enters the air inlet opening  3606  via a filter cap (not shown) that attaches over the air inlet opening  3606 . The air then passes up the outer channel  3620 , over the top of the tube  3604  and down the inner channel  3622 , allowing it to pass very closely to the UV lamp  3610 . As shown in  FIG. 36 , the outer channel is covered at the lower end of the housing by an annular aluminum disk  3640  which is held in place by an annular plastic cap  3642 . This allows air coming down the inner channel  3622  to pass into an outlet chamber  3650  defined by a plastic cap  3652 . A hole  3654  in the cap  3652  receives a blower (not shown) for moving the air through the kill chamber and along the delivery tube (not shown) to the face mask (not shown). The upper end of the housing  3600 , on the other hand, is closed off by an annular plastic cap  3660  that attaches to the aluminum wall of the housing and is provided with secondary inner wall  3662  for supporting the quartz tube  3604  while maintaining an air channel  3663  between the outer wall of the cap and the inner wall  3662 . The inner wall  3662  is provided with a UV reflective aluminum disk  3664  on its lower surface for reflecting UV light from the lamp  3610 . In order to allow the air to flow from the outer channel  3620  to the channel  3663 , the inner wall  3662  and aluminum disk  3664  are provided with holes  3667 . The air then passes from the channel  3663  to the inner channel  3622  through holes  3669  formed in the inner wall  3662 .  
      Yet another embodiment of the invention is shown in  FIG. 37 . The housing in this embodiment comprises a frusto-conical section  3702  made of polished aluminum and housing a mercury vapor lamp  3710 . The housing further includes a cylindrical section  3704  also made of polished aluminum. The lamp  3710  is secured by means of a plastic ring joint  3712  made of UV resistant plastic. A second ring joint  3714  connects the sections  3702 ,  3704  and supports a SiO 2  lens  3720  which focuses the UV beam from the lamp  3710  toward a high intensity zone  3730 . The focused beam is indicated by reference numeral  3732 , and the zone comprises a hole or channel  3740  formed in a UV resistant plastic plug  3742 . The depth of the hole  3740  is chosen to provide sufficient exposure to the pathogens by the focused UV beam as the air stream with the pathogens flows through the hole  3740  into the chamber  3700 . In this embodiment the hole  3740  has a diameter of 1 cm. The top of the chamber is closed off by a filter cap assembly  3750  comprising a filter  3752  held in a plastic cap  3754 . The cap  3754  is threaded to engage complementary threads on the outer surface of the plug  3742 . In order to reflect the UV light back, a polished aluminum disk  3756  is mounted between the filter assembly  3750  and the plug  3742 . Holes are formed along the outer periphery of the aluminum disk  3756  to allow air to pass from the filter into the hole  3740 . The air then passes down the section  3704  of the kill chamber and through a hole  3760  in the lens  3720 . The air passes down the section  3702  and out of the kill chamber via a hole  3780  formed in the wall of the section  3702 . To ensure good reflection, this embodiment also has a polished aluminum disk  3790  attached to the lower surface of the plug  3742 . The nature of the filter may be chosen to limit clusters or clumps of the particular biological pathogen(s) that the UV light source is intended to kill or destroy. Typically a filter capable of filtering 0.1 μm diameter or smaller pathogens is used. The purpose of the high intensity zone  3730  is to address biological contaminants with a higher resistance to UV radiation. While in this embodiment the high intensity zone is defined at the input, it could also be defined at the output to the housing or any other location in the housing or upstream or downstream of the housing. As described above, the lens  3720  acts as a UV beam magnifier to focus the beam onto the high intensity zone. The beam magnifier typically includes a lens made of high transmissivity material, in this case silicon dioxide. Instead of a UV mercury vapor lamp, a UV laser or a flash lamp (e.g., xenon or xenon-mercury flash lamp produced by Perkin Elmer such as the RSL3100) producing a high intensity burst of UV light or other energy source may be used. In such a case, the beam magnifier may still be used with the UV laser or flash lamp. In the case of a flash lamp the hole depth is chosen to ensure that no air passes all the way through the hole without being exposed to at least one pulse. The systems described above for supplying air may be portable and may be powered by one or more replaceable or rechargeable batteries, e.g., lithium ion batteries.  
      Further embodiments of the invention are shown in  FIGS. 38-44 . The embodiments of  FIGS. 37-44  deal with portable devices for use with a face mask. Thus they each device is intended to provide sterilized air to a specific user. However, the concepts of providing a high intensity zone in which higher intensity radiation is provided to a certain region, in accordance with the invention, is applicable also to other air sterilization systems such as UV sterilizers in air ducts of buildings, airplanes, ships, trains, etc.  
      The embodiment of  FIG. 38  specifically provides for sterilization not only of air from the atmosphere that is to be supplied to a specific user via a face mask (not shown) but also of air exhaled by the user. The kill chamber  3800  includes an SiO 2  lens  3802  that acts as a beam magnifier to focus 0.8 Watts from a 5 Watt (input power) Philips LWC lamp  3804  onto an incoming air stream that flows into the chamber  3800  through a 7 mm diameter hole  3806 . The hole  3806  is formed in an SiO 2  disk  3808  with an aluminum deposition on the side facing the lamp  3804 , and defines a first input to the kill chamber. The hole  3806  confines air flow to a narrow input region that coincides with the focal point of the lens  3802  and thus defines a high intensity zone in which pathogens are exposed to high intensity radiation. The 253.7 nm UVC is reflected by a polished aluminum disk  3810  (90% reflectivity) resulting in an intensity of 4.0 million microjoules of 253.7 mn UVC energy per cm 2  in the incoming air. This high intensity exposure is followed by a dose of 12 479 microjoules (combined direct or front radiation and reflected or back radiation) at a flow rate of 1.5 standard liters per second (90 SLM). It will be appreciated that, in this embodiment, since the UV light from the lamp  3804  is essentially funneled by the lens  3802  and the air stream that passes through the HEPA filter  3820  is funneled by the hole  3806  and a 1.5 inch diameter hole in a second disk  3821 , the high intensity radiation is, in fact, a range of radiation intensities that gradually decreases from its highest value at the focal point to its lowest value at the lens surface, before passing out of the housing via holes  3860 . Air flow from through the HEPA filter  3820 , into the housing of the kill chamber  3800  and out of the hoes  3860  to the face mask is generated by a blower (not shown) connected to the outer surface of the kill chamber housing.  
      In this embodiment a separate lamp housing  3830  is defined by a frusto-conical aluminum reflector  3832 . The lamp housing  3830  is temperature controlled by averaging the closest 2 or 3 temperature sensors  3818  to sweep the temperature range between 35 C and 45 C, and creating a cooling air flow using an in-line cooling fan (not shown) to fix the temperature at the level where the UVC output (measured by averaging the closest 2 of 3 UVC photodetectors  3822 ) is a maximum. In addition to the air from the atmosphere, which passes the HEPA filter  3820  being sterilized, exhaled air from the user&#39;s face mask is pulled through an outer annular region  3840  that is defined between the aluminum housing wall  3842  and an inner sleeve. The housing wall in this embodiment, is made from a 3 inch diameter aluminum tube with 0.1 inch wall thickness and polished inner surface. The inner sleeve is made from a fuse quartz tube  3844  with 2 inch inner diameter and 3 mm wall thickness. The lower portion of the inner sleeve is defined by a GE UV plastic tube that supports the tube  3844 . The exhaled air is pulled through the annular region  3840  by a small continuous exhale blower (not shown) through a one-way valve in the user&#39;s face mask (not shown) and enters the outer annular region  3840  through an opening  3848  in a lower GE UV plastic end cap  3850 , and is expelled from the kill chamber  3800  through an opening  3858  in an upper GE UV plastic end cap  3860 . The exhaled air, in this embodiment, is exposed to a dose of more than 8000 microjoules of UV radiation.  
       FIG. 39  shows another embodiment of the invention that is similar to the  FIG. 38  embodiment However, in this embodiment there is no separate air inlet for exhaled air that is exhaled by the user. Instead, a separate kill chamber would be used to sterilize the exhaled air in this embodiment. Also, in this embodiment the air outlet is defined by 4 holes  3960  formed in the inner sleeve  3962 . The air then passes out of the aluminum housing  3964  through a 3 inch diameter hole  3966 . Thus, unlike the  FIG. 38  embodiment, the air first passes up the outer chamber  3962  before leaving the housing  3964 . This allows the air to be exposed to further UV radiation, as discussed in greater detail below. As in the previous embodiment, the chamber includes an SiO 2  lens having more than 99% transmissivity that is used to focus 0.8 W from a 5 W (input power) Philips UVC lamp on an incoming air stream flowing through a 7 mm diameter hole. In other embodiments hole diameters of 0.5 to 1 cm were used. In contrast to the  FIG. 38  embodiment, the 253.7 nm UVC light in this embodiment is reflected by an Edmund Scientific SiO2 lens  3970  with a 1 μm Al deposition on the lower (collection) side. The projection of the UVC beam and its back reflection results in an intensity of 4 million micorojoules/cm 2  of UVC light being projected on the incoming air. This includes 800,000 microjoules/cm 2  incident radiation and 92% reflection (or 736,000 microjoules/cm 2 ) for a total of 1,536,000 microjoules/cm 2 . Over 0.7 cm diameter hole, the total exposure of air passing through the hole is 4000,000 Joules. The high intensity radiation is effective in destroying pathogens described in the multi-hit model where clusters form and require a higher than expected number of hits to destroy the pathogens. As the intensity I→∞, the time t→0, thus allowing a relatively short exposure time to a high intensity radiation to destroy the pathogens that would not be destroyed by the dose described in the classical model S=e −kIt  where S is the remaining pathogens and k is the constant for a specific pathogen response to UVC light. The high intensity radiation is followed by a dose of 12479 microjoules/cm 2 at a flow rate of 1.5 standard liters of air per second (90 SLM). This does not include any value for photon transmission back into the quartz chamber  3972  due to reflection off the polished aluminum inner surface of the housing tube  3964 . Nevertheless, this dose is well above the 6600 microjoules/cm 2  required to destroy the influenza A subtypes and yields a remaining pathogen population below 8×10−7 using S=e−kIt for influenza A because of the average 1&gt;80 000/cm 2 . In this embodiment, it receives a further UVC dose in the outer 0.32 liter chamber  3962 . The outer chamber  3962  adds effective volume providing much higher doses at more typical respiration rates of 30-40 SLM.  
      In another embodiment, instead of making use of a beam magnifier, a high intensity zone was created by providing a flash lamp or high power mercury vapor lamp in addition to a low power UV lamp such as the lamp  3804 .  
      In  FIG. 40 , like the embodiments of  FIGS. 37-39  also shows a design that defines a high intensity zone. It exposes all incoming air to a highly uniform, extremely high intensity flux of UVC light. Kowalski explains that the time t to destroy the secondary survival populations may approach zero at high intensities. This is demonstrated in the survival curves shown for aspergillus niger (a difficult pathogen to kill with UVC light) {Kowalski et al, 2000} where the surviving population drops from nearly 1 to 0.001 as the intensity increases from  200  micro joules per cm sq. to 1800 micro joules/cm 2 . The time to achieve this kill factor moves from nearly infinity to 1500 seconds in Kowalski&#39;s example. Based on the slope of change, using an appropriately high intensity level, t can be made to approach zero and leaving the surviving population orders of magnitude lower.  
      The chamber design shown in  FIG. 40  uses a silicon dioxide lense to expose incoming air to an intensity of 4,000,000 micro joules per cm. sq. At a flow rate of 1.5 liters per second (90 SLM) the UVC light in the chamber (using the k for influenza A of 0.001187 and averaging k2 for the three viruses with measured values for k2 of 2.66 e −3 ) leaves a total surviving population of 8.8 e −12 .  
      Utilizing the multihit model where S=1−(1−e −kIt )n for an n of 1.18, where all other variables are the same at a flow rate of 90 SLM, the surviving population S is 9.0 e −14  A one inch diameter SiO 2  lens 4000 having a focal length of 248 mm (&gt;99% transmissivity) is utilized to focus 0.8 watts from a 5 watt (input power) Philips UVC lamp  4002  on an incoming air stream flowing through a 7 mm diameter hole  4004  formed in a SiO2 disk  4006  with an aluminum deposition on its back (lower) side. The 253.7 nm UVC light reflected by an Edmund Scientific SiO 2  lens  4008  with a 0.1 cm Al deposition on the collection (lower) side. The projection of the UVC beam and its back reflection results in an intensity of 4.0 million microjoules/cm 2  of UVC light being projected on the incoming air.  
      The lamp region  4010 , which is defined by an aluminum reflector  4012 , is temperature controlled by averaging the closest 2 of 3 temp sensors  4020  to sweep the temperature range between 35C and 45C and controlling cooling using an in-line cooling fan) to fix the temperature at the level where the UVC output (measured by averaging the closest 2 of 3 UVC photo detectors  4022 ) is a maximum.  
      Even though the chamber is designed to sterilize air at a flow rate of 90 SLM the blower will need to be capable of providing 170 SLM. This extra capacity is required because of the wide variation of peak airflow requirements among adults performing light work. In studies performed by a NIOSH contractor, subjects measured blood oxygen saturation levels dropped as low as 92% when positive air pressure respirators (PAPR) systems could not meet peak inhalation demands in higher work/stress studies. While, this is not a catastrophic level for blood oxygen levels, it is good practice for inhalation requirements to be met, and is probably why NIOSH set the minimum at 170 SLM.  
      Yet another embodiment of the invention is shown in  FIG. 41 . In this embodiment the housing  4100  of the kill chamber  102  comprises a glass tube with a reflective coating on its inner surface. In this embodiment the tube has a 2 inch inside diameter but in other embodiments 2.5 inch inside diameter and 3 inch inside diameter tubes were used. The tube  4100  is closed off at its lower end by a titanium doped quartz disk  4104  held in place by means of a GE UV plastic ring or joint  4106 . At its upper end, the  4100  is provided with a plastic end cap  4110  having a threaded upper portion that engages complementary threads on a filter cap  4112 . The filter cap  4112  includes a HEPA filter  4114  for filtering particles from incoming air. In this embodiment, the UV lamp  4120  is arranged perpendicularly to the longitudinal axis of the housing  4100  and is housed in a reflective housing  4130  for reflecting light upward toward the upper end of the housing. The upper end of the housing, in turn, is provided with a parabolic glass mirror  4140  having an Al/SiO coating on its lower, curved surface. The mirror  4140  is held in place by means of a plastic mirror support  4142  that takes the form of an annular shaped plastic disk with holes  4144  for allowing air to pass from the filter  4114  into the housing  4100 . The air moves through the kill chamber  4102 , which in this embodiment has a volume of 0.35 liter, and passes out of the housing  4100  through a hole  4150 . The hole  4150  leads to a blower which moves the air to a face mask (not shown).  
      Another embodiment of the invention is shown in  FIG. 42  which is similar to that of  FIG. 41 . However, in this embodiment, the air entering the air flow housing or chamber  4200  is constrained to a small opening  4202  by a quartz disk  4204  with a reflective lower surface  4206 . The upper reflector  4210 , is correspondingly smaller than that of  FIG. 41 . The reflector  4210  comprises a glass mirror with reflective coating e.g., aluminum deposition with MgF 2  overcoat. The other elements are substantially the same as in  FIG. 41  and are therefore not described again.  
      Yet another embodiment is shown in  FIG. 43 , which is similar to the embodiment of  FIG. 42  but in addition to the lamp housing  4300 , it includes a further, outer housing  4302  for the UV lamp  4310 . The outer housing  4302  has a cooling air input  4320  and an output  4322  to cool the lamp  4310 .  
       FIG. 44  shows yet another embodiment, which is similar to the embodiment of  FIG. 41 . Therefore similar elements are not discussed here again. However, this embodiment differs in that an inner hour-glass shaped wall  4400  is provided to constrain the air flow path to a narrow region near the middle of the housing  4402 . The UV lens  4104  in this embodiment has its focal point coinciding with the narrow portion  4106  of the hour-glass shaped wall  4400 .  
      The lamp housing in the embodiments of  FIGS. 37-44 , e.g the housing defined by tube  3702 , by  3832 , by  4012 , by  4130 , inner housing  4300 , and housing  4410  is kept at a slight negative pressure e.g., 500 torr of dry N 2 . This helps protect the user against leakage in the event of UV lamp failure.  
      What is important in all of the portable devices that feed a face mask, is that energy needs to be conserved to facilitate the use of a portable power supply. Hence the use of a fan or blower rather than a pump to suck the air into the kill chamber and through to the face mask, is preferred. In order to avoid simply having to use a high power blower to provide a large positive pressure in the face mask, the present invention proposes using minimal size blowers while still providing a positive pressure in the mask. Since conventional size HEPA filters used in masks (especially high quality filters such as N100 which are certified to filter out 300 nm particles to 99.97%) have relatively small diameter and produce a large pressure differential, they are not suitable for use with low power blowers. The present invention addresses this issue by providing for larger diameter HEPA filters to be used. In addition power management is achieved by providing constant pressure or constant flow rate. In a preferred embodiment, pressure in the mask is sought to be maintained constant as user inhales and exhales or changes his/her exertion. This means that the blower power is adjusted as needed e.g. by controlling its current based on one or more pressure sensors. In some of the embodiments three pressure sensors were used and the average taken of the two closest values. As discussed above, instead of adjusting power to the blower, the flow can be varied using a valve in the connection between the kill chamber and the mask. To further reduce power consumption, positive pressure in the mask is kept to a very low value, preferably 0.5 to 1 inch of water pressure over ambient pressure. This arrangement allows the use of a few masks that are not necessarily fitted masks but loosely fit the contours of a limited number of generic human faces. In one embodiment, several different generic sizes, e.g., extra small, small, medium, large, extra large masks were provided for attachment to the kill chamber in order to accommodate different users and provide them all with a relatively good fit. For purposes of this invention, the term “loosely fitting” will be used to describe such a mask fit.  
      The invention further contemplates not only allowing different face masks to be used with a kill chamber by having the face mask and kill chamber connected by a releasable connection, it also contemplates a modular arrangement for the other elements. As such, the invention provides for a separate housing or chamber for the UV lamp and for the air supply. For instance in  FIG. 41 , the lamp  4120  is mounted in its own chamber defined by reflector  4130 . The air supply, in turn is constrained to an air flow housing  4100  which has its air flow inlet at the filter  4114  and air flow outlet at hole  4150  leading to the blower. According to the invention, the air flow housing  4100  and lamp housing  4130  are separably connected. Furthermore, the lamp  4120  the blower or fan that helps move the air through the air chamber, are provided with their own power supplies and electronics to allow the air chamber to work independently of the UV lamp. This allows the system to be used with or without UV sterilization. Also, the modularity of the system allows for the various elements to be separably sold and replaced and facilitates interchangeability of elements by different suppliers, provided common connectors are used. In one embodiment the air flow housing and lamp housing is provided with a charger arranged for simultaneous charging of the batteries for the blower and the batteries for the UV lamp. In particular, the charger plug is provided with two pairs of pins for simultaneous charging of the blower and UV lamp, and provide for the ability to use the same charger if only the blower without the UV lamp is used. In such a case only one of the pairs of pins is engaged for charging the batteries for the blower.  
      As another feature of the invention, the present embodiment provides for safeguards against ozone production. In order to minimize the production of ozone, a ZrO 2 . layer is provided on the quartz plate or the bulb. This reduces the peaks between the wavelengths 185-250 nm. In addition in some embodiments HFlO 2  was also, or instead, sputtered onto the reflective surfaces. Also a titanium sponge was placed in the air flow path in the chamber in some embodiments.  
      As discussed above, it is desirable to provide a highly reflective coating on the inner surface of the housing of the kill chamber in order to ensure multiple reflections of the UV light and thereby increase the effectiveness of the light in destroying the DNA or RNA of any biological contaminants entering the kill chamber. Various materials and coatings may be used as discussed below. However, some processes for applying coatings are best performed prior to forming the housing since the coating may be such that it is prone to peeling off if the surface on which it is formed is subsequently deformed or bent.  
      The housing of the kill chamber, in one embodiment, comprises an aluminum pipe in which the inner surface is polished and is then exposed to a chemical vapor deposition (CVD) process to increase its UV reflectivity. This may involve organo-metallic CVD (OMCVD), or plasma enhanced CVD (PECVD).  
      In another embodiment, instead of CVD, a reflective coating was applied to the inner surface by sputtering on a reflective coating e.g., Al sputtered onto a highly polished surface e.g., several 100 nm thick—preferably 300 nm thick or more.  
      In yet another method of applying a highly reflective surface the housing material, e.g. in the case of an Al housing material the Al material was placed in a chemical bath and the chemical reacted with the Al in an electroplating process. The aluminum could be electrically connected to act as the anode or the cathode.  
      In yet another approach to applying the highly reflective coating an electro-chemical deposition was performed, similar to a corrosion process. In this way an oxide layer was formed on the metal surface of the housing material, which in this embodiment was Al, thereby providing an aluminum oxide layer on the Al.  
      In yet another approach to applying a highly reflective coating molecular beam epitaxy was performed, involving the use of a high vacuum environment and creating a beam of material to form a layer on the substrate material (in this case on the housing material).  
      In yet another approach to applying a highly reflective coating ion beam implantation was used to implant highly reflective materials. The formation of a highly reflective coating may be followed by steps for adding additional chemicals by ion beam implantation. Additional chemicals may also be added by ion beam implantation where a highly reflective coating has already been applied. For instance, if Al is first sputtered on, additional material for better reflectivity may thereafter be added by ion beam implantation.  
      As suggested above, instead of first completing the forming of the housing of the kill chamber or using a tube or pipe, and then adding a reflective coating, the housing may be formed from a flat or open piece of metal that is treated with a reflective coating and preferably also a coating with a high refractive index, prior to being formed (e.g., by bending or folding) into a tube or cylinder (e.g. square or round cylinder) as shown in  FIG. 26 . The housing may, instead be made from two or more pieces that fit together and may be of any shape that is suitable for forming a housing when the pieces are fitted together, one embodiment of which is shown in  FIG. 27 . The bent or folded or fitted together pieces may be joined where the edges meet (referred to herein as the joint for convenience) by sealing the joint e.g. by thermal seal such as a thermal weld or using a thermal adhesive or any other suitable technique.  
      One or more of several materials may be chosen to provide the highly reflective coating. The materials are chosen to preferably have high reflectivity for UVC particularly for UV in range 253-268 nm, e.g., Al alloy e.g. aluminum oxide. Other oxides may also be used e.g. magnesium oxide. The oxides may be applied on their own or after first applying a layer of Al if the chamber material is not itself made of aluminum.  
      Other compounds such as barium sulphate or alloys (e.g Al alloys or Ag alloys) may be used instead to provide for a highly reflective chamber surface. In yet other embodiments compounds that may chosen from CaF2, MgF2, SrF2, BaF2, LiF, KTiOPO4 (potassium titanyl phosphate or KTP), CaCO3 (calcite), BaB2O4 (beta barium borate or BBB), and HFlO 2 , TiO2 were used as highly reflective coatings. In fact multilayers of two or more of these compounds (known as “dielectric stacks”), were used in some embodiments, and in some they were arranged as pairs of layer, e.g. 10 pairs of layers, e.g., pairs such as CaF2 and MgF2 and thicknesses of the various layers adjusted depending on the refractive indices of the materials used. Preferably alternating layers of high- and low-refractive index material are used (where the indices of refraction are at the wavelength for which high reflection is desired). In particular, each layer should be an odd multiple of one-quarter of the wavelength of the light in the medium, i.e. an odd multiple of one-quarter of the vacuum wavelength divided by the index of refraction. Thus, if the indices of refraction of the two materials are 1.433 and 1.762 and the vacuum wavelength is 265 nm, you would want alternating layers with a thickness of 46 nm (or 139 nm, or 231 nm, or other odd multiples) for the low-index material and with a thickness of 38 nm (or 113 nm, or 188 nm, or other odd multiples) for the high-index material.  
      In yet another embodiment a polymer, in this case Teflon, was sprayed on. Instead the Teflon or other polymer could be applied by dipping the housing material into a Teflon bath before or after forming the housing.  
      In the case where the housing is cylindrical to start with or in two parts that don&#39;t need subsequent bending, one alternative was to provide barium sulphate particles in suspension with UV resistant polymer, which was then sprayed on. Instead it could be applied by dipping.  
      In one embodiment instead of applying a highly reflective coating, the housing itself was made from a UV resistant polymer containing barium sulphate particles.  
      In order to protect the user not only while he or she is wearing the apparatus of the invention, but also in the process of taking the apparatus and clothing items off, and to ensure that the apparatus and clothing items are themselves decontaminated after use, the present invention also proposes a methods and means for assisting in removing gloves and decontaminating the various items.  
       FIG. 28  shows a pair of gloves  2800  with tabs or strips  2802  that allow the user to easily remove the gloves. As an added protection, the tabs  2802  in this embodiment are provided with a biocide coating.  
      Typically the gloves will be sealed in an air proof package or bag as shown in the embodiment of  FIG. 29 . To avoid the biocide, which commonly has a crystalline structure, from absorbing moisture prior to removal of the gloves  2900  from their package  2902  the gloves  2900  are stored in the package  2902  with a desiccant  2904 . Instead of tabs, the gloves  2900  of this embodiment are made from a woven material impregnated with a biocide. In another embodiment, instead of a woven material or tabs, the entire glove was treated with a biocide coating.  
      As part of another aspect of the invention, instead of treating the gloves to facilitate removal without contamination, a sticky board  3000  is provided as shown in  FIG. 30 . The board  3000  is attachable to a wall or other secure surface, and removal of the user&#39;s gloves  3002  is achieved by the user touching the board and slipping the hands out of the gloves as the gloves  3002  are retained by the sticky board.  
      As a further aspect of the invention, there is provided a decontamination chamber and a method of de-contaminating the apparatus of the invention, namely the kill chamber and face mask with goggles, as well as clothing items worn by the user. One embodiment of a decontamination chamber of the invention is shown in  FIGS. 31-33 . The decontamination chamber  3100  comprises a polished Al chamber, which in this embodiment is coated on the inner wall with paint that contains barium sulphate for greater reflectivity. The decontamination chamber may instead be made of plastic coated with a UV reflective coating, e.g. by sputtering on a highly reflective coating, and can be made in two halves that are then joined, e.g. by a thermal seal or by using adhesive (e.g., a thermal adhesive). Thus the entire discussion of the formation, coatings and materials for the kill chamber apply equally to the formation of the decontamination chamber and are not repeated here for convenience but are understood as applying to the decontamination chamber as well.  
      The chamber  3100  of this embodiment has a door  3102  with a view port  3104  and handle  3106 .  
      A timer  3107  is also included allowing the decontamination time to be set. The timer may be coupled to a visual or audible indicator such as a buzzer to advise the user of the decontamination chamber when the decontamination time is up. In addition the timer may be connected to the UV light sources to switch the lights off when the defined time is reached. In another embodiment, a timer and locking mechanism may be included in the door (similar to a front loading washing machine) to automatically lock the door for a defined time. In yet another embodiment, where subsequent access to chamber may be desired for further additional loading of material, a preset timer may be included in which the time is simply reset to start over whenever the door is opened.  
      An electrical access point  3108  extends to an electrical outlet mounted on the inside of the chamber as is discussed in greater detail below.  
       FIG. 32  shows the inner side of the side panels and back panel  3110  of the chamber  3100  and  FIG. 33  shows the upper and lower panels or walls of the chamber  3100 . Each panel or wall  3110 ,  3120  is provided with a UV light source. As shown in  FIGS. 32 and 33 , the light source on the panels  3110  comprises a mercury vapor lamp  3200 , while in the case of the panels  3120  the light source comprises two mercury vapor lamps  3300 . In a preferred embodiment the chamber door  3102  is provided with a switch (not shown) that turns off the UV light source when the door opens. This may be a mechanical switch or a UV photo detector with an electric switch. In addition a photodetector is preferably provided for each UV light bulb or, in the case of a UV LED light source, banks of LEDs may be provided with photodetectors to indicate when to change the bulbs or LEDs.  
      In the case of the panels  3110 , the back panel also includes an electrical outlet  3210 , which is shown in  FIG. 32  and which receives power via the access point  3108  discussed above with respect to  FIG. 31 . It will be appreciated that while the side panels  3110  may also be provided with electrical outlets, typically the chamber  3100  need only have one electrical outlet for plugging in a battery pack of the kill chamber. It will also be appreciated that the battery pack of the kill chamber may be implemented to be chargeable by magnetic coupling similar to an electric toothbrush, in which case the chamber  3100  may be provided with a complementary charging socket.  
       FIG. 33  shows that both panels  3120  are in turn provided with recesses  3302  for receiving a rotational assembly, which is illustrated in  FIG. 34 .  
      The rotational assembly  3400  of this embodiment includes a support post  3402  mounted on a platform  3404  and has a bearing  3406  mounted on its lower surface, which is receivable in the recess  3302  of the lower panel  3102 . Shoe holders or racks  3310  are also mounted to the platform  3404  for supporting the user&#39;s shoes. In order to ensure UV radiation from the inside as well, a mercury vapor lamp  3420  is mounted on the support post  3402 . In one embodiment a support platform  3430  made of UV transparent material, e.g., quartz, is secured to the support post  3402  by means of arms  3432 . The support platform  3430  may be used for supporting items such as the kill chamber assembly and face mask used by the user. In another embodiment a rack  3450  may in addition to the platform  3430  or as an alternative to the platform  3430 , be mounted by means of a bearing  3452  to the recess  3302  of the upper panel  3120 . As shown in  FIG. 34 , the rack  3450  is suspended from a rotational platform  3454 . In the embodiment shown in  FIG. 34 , the rack  3450  includes hooks  3460  for the backpack respirator and face mask. It also includes a pants hanger  3462  and jacket hanger  3464 . The entire rotational assembly is rotated for maximum exposure to UV radiation from the UV light sources mounted on the side, back, upper and lower panels of the decontamination chamber. In this embodiment a drive motor (not shown) is connected to the platform  3404  and a second drive motor is connected to the platform  3454 . It will be appreciated that in other embodiments the rack  3450  could be connected to the mercury vapor lamp  3420  or the support post  3402  by means of brackets, thereby avoiding the need for two drive motors. It will also be appreciated that the mercury vapor lamp  3420  could be replaced with a UV LED or a bank of UV LEDs.  
      While specific embodiments were discussed above, it will be appreciated that these were included by way of example only and that the present invention is not limited to the embodiments discussed, but includes other embodiments as defined by the scope of the claims. Furthermore, while the above embodiments discussed with respect to  FIGS. 1-17 ,  35  and  36  dealt specifically with a portable sterilization apparatus, the present invention relating to the protection of UV LED light sources through polarized coatings or lenses, the supplementation of mercury vapor lamps and/or protective quartz sleeves around the lamps with titanium by deposition or implantation, and the types of materials and methods of providing a highly UV reflective inner surface to the housing of the chamber, are equally applicable to a non-portable sterilization apparatus for sterilizing not only air but also objects placed in the housing of the apparatus, such as the decontamination of clothing and portable air sterilization apparatus in a decontamination chamber as described with respect to  FIGS. 31-34 . Similarly, the shaping of the housing for channeling air or inclusion of baffles to channel air close to the UV light source is equally applicable to a non-portable air sterilization apparatus. The claims are accordingly defined to cover all such sterilization apparatus. The relevance of the proposals in the present invention to bring the air into close proximity with the UV source and use highly reflective housing surfaces and hopefully eliminate some of the water vapor in the air through the use of the filtering at the air intake, is borne out by academic studies and models such as that described in the article “Mathematical Modeling of Ultraviolet Germicidal irradiation for Air Disinfection” by W. J. KOWALSKI, W. P. BAHNFLETH, D. L. WITHAM, B. F. SEVERIN, and T. S. WHITTAM (Quantitative Microbiology 2, 24-9270, 2000 # 2002 Kluwer Academic Publishers.  
      As mentioned above, the use of lenses or other means to create high intensity radiation in order to reduce secondary survival populations of pathogens is applicable also to systems that are not specifically geared to supply individual users with sterilized air. The approach discussed above of dealing with secondary survival rates is applicable also to air sterilizers that serve large groups of people, e.g., air sterilizers used in heating duct systems. It will also be appreciated that all of the embodiments above are given by way of example only and are not intended to limit the invention as defined by the claims.