Abstract:
A personal protection system with a hood and a helmet that is worn under the hood. Internal to the helmet is a fan that draws air into the hood. The fan has blades that are curved along their longitudinal axes.

Description:
REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 12/834,566 filed 12 Jul. 2010 now U.S. Pat. No. 8,407,818. Application Ser. No. 12/834,566 is a divisional of U.S. patent application Ser. No. 11/277,424 filed 24 Mar. 2006 now U.S. Pat. No. 7,752,682. Application Ser. No. 11/277,424 claims the benefit of provisional application Ser. No. 60/664,900 filed 24 Mar. 2005. The contents of the above-listed applications are incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The subject invention generally relates to a personal protection system mountable to a user for distributing air to the user. The personal protection system is utilized in the medical profession during surgical procedures. The subject invention more specifically relates to a helmet assembly and gown for use in the personal protection system. 
       BACKGROUND OF THE INVENTION 
       [0003]    Personal Protection systems and helmet assemblies utilized in personal protection systems are known in the art. AS indicated above, personal protection systems are worn by users throughout the medical profession, such as surgeons, during medical procedures 
         [0004]    Conventional personal protection systems and helmet assemblies are deficient for one reason or another. For example, U.S. Pat. No. 6,990,691 to Klotz et al. (the &#39;691 patent) discloses a helmet assembly that draws air in with a fan assembly and distributes the air to front and rear air exits. However, when the helmet assembly is worn by the user, the air exit is disposed such that the air is vented near the middle of the back of the head of the user. Thus, the air cannot be directed toward the neck of the user, where most surgeons desire the air&#39;s cooling presence. 
         [0005]    Other deficiencies of prior art personal protection systems are with the fan assembly. For instance, the shape of the blades of the fan, which rotate to draw in air, do not provide for the most efficient and quietest flow of air possible. This causes excessive power consumption, which leads to premature drain of battery packs, and excessive noise, which can be distracting for a surgeon performing delicate operations. 
         [0006]    Furthermore, the prior art helmet assemblies tend to transfer vibrations caused by the rotation of the fan to the user, as well as being noisy in general. The vibrations, as well as the noise, can be distracting to the surgeon, who obviously needs to focus his efforts at the complex task at hand. 
         [0007]    Yet another deficiency of the &#39;691 patent concerns the multiple removable layers disposed on the face shield. The &#39;691 patent is silent as to sterility of the multiple removable layers. However, sterilization concerns are of an utmost importance for any product involved in the surgical process. 
         [0008]    For the above mentioned reasons, it is desirous to provide a personal protection system which provides more control over air flow to the neck of the user and which provides more efficient and quieter means for moving the flow of air. Furthermore, it is desirous to provide a personal protection system which noise and vibrations, which can be distracting to the surgeon, are kept to a minimum. Moreover, it is desirous to provide a face shield with removable layers that is sterilized in an efficient manner. 
       SUMMARY OF THE INVENTION AND ADVANTAGES 
       [0009]    In a first aspect of the invention, a personal protection unit is disclosed. The personal protection unit includes a support structure for suspending a hood over the head of an individual. A fan module is attached to the support structure, with the fan module receiving air and discharging air. A duct is connected to the support structure and has an opening positioned to receive the air discharged from the fan module. The duct is shaped to have a rear air exit. The duct is arranged relative to the fan module so that only a fraction of the air discharged from the fan module enters the duct. The duct extends from the support structure and the rear air exit is positioned so that air is discharged from the rear air exit directly onto the neck of the individual. By the duct extending from the support structure and discharging air directly on to the neck, the comfort of the individual (e.g., a surgeon) is increased, allowing the individual to focus on the task he or she is performing (e.g., surgery). 
         [0010]    In a second aspect of the invention, the personal protection unit includes the support structure for suspending the hood over the head of the individual. The personal protection unit includes a fan for circulating air. A motor is attached to the support structure and is connected to the fan for actuating the fan. An elastomeric, vibration dampening member holds the motor to the support structure. The vibration dampening member helps to reduce transmission of noise and/or vibrations generated by the fan and/or motor to the user. Reduction of noise and/or vibrations will decrease distractions to the individual. 
         [0011]    A third aspect of the subject invention provides the personal protection system with the hood formed of flexible sterilizable material, a portion of which is filter material, and shaped to be worn over the head. A transparent face shield is attached to the hood. The personal protection system includes a support structure for suspending the hood over the head. A fan is attached to the support structure for circulating air through the hood. A plurality of individually removable layers of sterile transparent material are disposed over the face shield. 
         [0012]    A fourth aspect of the invention provides a method of assembling a sterilized hood assembly having a transparent face shield. The method includes the step of providing a hood formed from sterilizable flexible material, a portion of the material being filter material. A transparent face shield assembly is attached to the hood where the shield assembly includes a face shield. The method further includes the step of sterilizing the hood and face shield assembly using a sterilization process that does not adversely affect the filter material. The transparent shield assembly further includes a plurality of removable transparent layers disposed over the face shield. Sterilizing the face shield and removable layers together as a whole provides for a more effective assembly process by negating the possibility of introducing contaminants during subsequent assembly operations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0014]      FIG. 1  is a perspective view of a personal protection system embodied as a helmet assembly mounted on a head of a user; 
           [0015]      FIG. 2  is a cross-sectional view of the helmet assembly; 
           [0016]      FIG. 3  is an exploded perspective view of the helmet assembly; 
           [0017]      FIG. 4  is an exploded view of a preferred embodiment of a fan module of the present invention; 
           [0018]      FIG. 5  is a cross-sectional view of the preferred embodiment of the fan module; 
           [0019]      FIG. 6  is a cross-sectional view of an alternative embodiment of the fan module; 
           [0020]      FIG. 7  is a perspective view of a fan of the fan module showing fan blades having an airfoil shape; 
           [0021]      FIG. 8  is a top view of the fan showing the fan blades having air foil shapes; 
           [0022]      FIG. 9  is a elevational view of a nozzle assembly of the present invention; 
           [0023]      FIG. 10  is a perspective view of a nozzle tip of the nozzle assembly; 
           [0024]      FIG. 11  is a bottom view showing a port of a nozzle of the nozzle assembly; 
           [0025]      FIG. 12  is an exploded view of a first alternative nozzle of the present invention and a first adjustable air flow volume mechanism; 
           [0026]      FIG. 13  is an exploded view of a second alternative nozzle of the present invention and a second adjustable air flow volume mechanism; 
           [0027]      FIG. 14  is a perspective view a hood having an integrated face shield attached to the helmet assembly; and 
           [0028]      FIG. 15  is an elevational view of a removable face shield layer attached to the face shield. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a personal protection system or personal protection unit is generally shown at  20 . The personal protection system  20  is mountable to a user (i.e., an individual) for distributing air to the user. The personal protection system  20  of the present invention is adapted from the personal protection systems disclosed in U.S. Pat. Nos. 6,481,019 to Diaz et al. (the &#39;019 patent) and 6,973,677 to Diaz et al. (the &#39;677 patent), which are hereby incorporated by reference. 
         [0030]    In the preferred embodiment, as shown in  FIG. 1 , the personal protection system  20  is implemented as a helmet  22  or helmet assembly  22 . The personal protection system  20  filters air between a head  24  and body  26  of a user, e.g., a medical professional, and an environment external to the user. When in use, the preferred helmet assembly  22  of the personal protection system  20  is mounted to the head  24  of the user. The helmet assembly  22  distributes air about the head  24  of the user as will be described below. More specifically, in the preferred embodiment, the helmet assembly  22  distributes air toward both a front of the head  24 , i.e., a face of the user, and a back of the head  24 , i.e., a neck of the user. 
         [0031]    The personal protection system  20  of the subject invention may be described hereafter in terms of the helmet assembly  22  of the preferred embodiment. However, this should not be construed as limiting the personal protection system  20  to the helmet assembly embodiment. 
         [0032]    Referring to  FIG. 2 , the helmet assembly  22  includes a shell  28  providing structural support (i.e., a support structure  28 ). The shell  28  preferably includes an inner shell portion  30  facing the user and an outer shell portion  32  facing away from the user. In the preferred embodiment, the outer shell portion  32  is spaced apart from the inner shell portion  30  to define at least one air flow channel  34  between the inner and outer shell portions  30 ,  32 . It is to be understood that the present invention may include more than one discrete air flow channel  34 . However, the preferred embodiment includes a single unitary air flow channel  34  and the present invention will be described below in terms of this air flow channel  34 . The shell  28  is preferably formed of acrylonitrile butadiene styrene (ABS), but may be formed, in alternative embodiments, of glass-filled polypropylene or other suitable materials. 
         [0033]    The air flow channel  34  channels air about the head  24  of the user. The inner and outer shell portions  30 ,  32  may form the air flow channel  34  from a two-sheet thermoforming process which improves the structural strength of the shell  28 . More specifically, each of the inner and outer shell portions  30 ,  32  include an outer periphery, and in the two-sheet thermoforming process, the inner and outer shell portions  30 ,  32  are pinched together at their outer peripheries. The air flow channel  34  is subsequently thermoformed between the pinched outer peripheries. 
         [0034]    The helmet assembly  22  also includes a facial section  36  extending from the shell  28  to define a facial opening  38 . The facial section  36  of the helmet assembly  22  is a chin bar  40 . Preferably, the chin bar  40  is flexible and is formed of plastic. The chin bar  40  may also be formed of a polypropylene component. The flexibility of the chin bar  40  protects the user&#39;s face and also absorbs impact when the user contacts an external object with the helmet assembly  22 . 
         [0035]    Referring now to  FIG. 3 , the helmet assembly  22  includes a fan module  42  supported by the shell  28 . More specifically, the fan module  42  is mounted in a cavity  44  formed by the shell  28 . The fan module  42  operates to generate a flow of air which is fluidly communicated into the air flow channel  34 . As shown in  FIG. 4 , the fan module  42  includes a fan  46  and a motor  48  mounted to a scroll housing  50 . The motor  48  includes a drive shaft  52  operatively connected to the fan  46  to drive the fan  46  at a plurality of rotational speeds correlating to an amount, or a volume, of air flowing into the air flow channel  34 . As appreciated by those skilled in the art, the rotational speeds of the fan  46  can be measured in revolutions per minute (RPMs). 
         [0036]    Referring again to  FIG. 3 , a cover plate  54  is fixed to the shell  28  and the fan module  42  to hold in the fan module  42  in the cavity  44 . A fan module cushion  56  is disposed between the cover plate  54  and a base of the fan module  42 . The fan module cushion  56  reduces the transmission of noise from the motor  48  to the user. 
         [0037]    Referring to  FIGS. 4 and 5 , in the preferred embodiment, a motor cushion  58  is disposed between the motor  48  and a motor mount  60 . A plurality of motor mount cushions  62 , embodied as grommets, is placed between the motor mount  60  and the scroll housing  50  (although shown below the scroll housing  50  for clarity, the arrangement is best shown in  FIG. 5 ). The motor cushion  58  and motor mount cushions  62  work together as a vibration dampening member to reduce shock loads and vibrations. More specifically, the motor mount cushions  62  are the primary component for shock reduction between the helmet structure, e.g., shell  28 , and the motor  48 , thereby extending the bearing life of the motor  48  and providing low sound characteristics. The motor mount cushions  62  completely isolate the motor  48  from the rest of the helmet structure. By having two sets of cushioning, i.e., the motor cushion  58  between the motor  48  and motor mount  60  and the motor mount cushions  62  between the motor mount  60  and the scroll housing  50 , the transmission of energy between the helmet structure and the motor  48  can be fine tuned. The motor cushion  58  and the motor mount cushions  62  may be formed of foam and/or an elastomeric material. 
         [0038]    Referring to  FIG. 6 , in an alternative embodiment of the invention, the motor mount  60  for mounting the motor  48  to the scroll housing  50  is formed of elastomeric material. Preferably, the motor mount  60  is formed of silicone having a durometer of from 10 to 80 shore A. Much like the motor mount cushions  62  of the preferred embodiment, the elastomeric motor mount  60  reduces shock loads and vibrations. Moreover, the scroll housing  50  may be formed of glass-filled polypropylene to further reduce vibrations. 
         [0039]    Referring now to  FIG. 7 , the fan  46  includes a plurality of curved blades  64  and a hub portion  66 . The curved blades  64  of the fan  46  encourage air into the scroll housing  50 . The blades  64  are further defined as centrifugal fan blades having a foil cross-section, i.e., the blades  64  taper along their length. This configuration moves air more efficiently and more quietly than blades  64  with a constant thickness. The foil cross-section of each of the blades  64  preferably has an angle of attack of from 30 to 50 degrees. The fan  46  is preferably formed of glass-filled polypropylene, more preferably 30% glass-filled polypropylene. 
         [0040]    Referring back to  FIG. 4 , the scroll housing  50  includes a base portion  68  and an outer wall  70  circumferentially extending around the base portion  68 . The outer wall  70  includes an upper edge  72 . The scroll housing  50  further includes at least one air inlet  74  and at least one air outlet  76 . In the preferred embodiment, the scroll housing  50  includes a plurality of air outlets  76 , i.e., at least two air outlets  76 . Other embodiments of the present invention (not shown) may also only include the fan module  42  without the scroll housing  50 . In such embodiments, the at least one air inlet  74  and the at least one air outlet  76  can be described as components of the fan module  42 . 
         [0041]    The scroll housing  50  of the preferred embodiment may include an inclined surface  78  (or cutoff) along the outer wall  70  at one or more of the air outlets  76 . The inclined surface  78  in the preferred embodiment is inclined relative to a rotational axis of the fan  46  and motor  48 . The inclined surface  78  moves air more efficiently through the air outlet  76 . In effect, a blade-pass frequency at each air outlet  76  employing the inclined surface  78  is altered such that at least two blades  64  pass the air outlet  76  simultaneously. The outer wall  70  is preferably wrapped outwardly away from the fan  46  at the outlet with the inclined surface  78  such that a flange portion  80  of the outer wall  70  defines the inclined surface  78 . Preferably, the outer wall  70  is rounded at the flange portion  80  to provide a smooth transition to the air outlet  76 . This reduces noise from the air flowing through the air outlet  76 . 
         [0042]    Referring again to  FIG. 2 , the helmet assembly  22  further includes an intake grid  82  mounted to the outer shell portion  32 . The intake grid  82  includes a top surface  84  spaced from the outer shell portion  32  of the helmet assembly  22 . The intake grid  82  is contoured to the outer shell portion  32  between the front and rear of the shell  28 . Air is drawn into the scroll housing  50  through the intake grid  82  by the fan  46 . The blades  64  of the fan  46  are dimensioned such that a top of each of the blades  64  is from about 0.14 to 0.20 inches below the upper edge  72  of the outer wall  70  of the scroll housing  50 . This provides clearance between the blades  64  and the outer shell portion  32  above, which results in low noise and high efficiency. 
         [0043]    The air inlet  74  of the scroll housing  50  is in direct communication with a hole  86  formed within the outer shell portion  32  of the shell  28  for drawing air into the scroll housing  50 . In alternative embodiments of the present invention, an external structure, not shown in the Figures, can be mounted external to the helmet assembly  22  to establish the air inlet  74  of the scroll housing  50  for drawing air into the scroll housing  50 . The hole  86  formed in the outer shell portion  32  may be circular in shape. The diameter of the hole  86  may be sized in relation to a diameter of the fan  46  such that only a portion of the fan  46  diameter is exposed when viewed through the air inlet  74  in the outer shell portion  32 . This ratio of air inlet  74  diameter to fan  46  diameter may be from 1:2 to 1:1, more preferably, from 1:1.5 to 1:1.1. 
         [0044]    Referring to  FIG. 4 , a support pedestal  88  protrudes from the motor mount  60 . Preferably, the support pedestal  88  is integrally formed as a part of the motor mount  60 , which is fixed to the base portion  68 . Alternatively, it is also to be understood that the support pedestal  88  can be a separate part. That is, the support pedestal  88  can be a separate part that is mounted or connected to the base portion  68  of the scroll housing  50  via connecting screws, snap-fit, and the like. The hub portion  66  of the fan  46  is rotatably mounted in the scroll housing  50  about the support pedestal  88 . The motor  48  of the fan module  42  is mounted within an underside of the support pedestal  88  for space-saving purposes in the helmet assembly  22 . As appreciated, the underside of the support pedestal  88  is essentially hollow. The motor  48  shaft protrudes through an opening in the support pedestal  88  to rotatably engage the fan  46 . The cover plate  54  operates as a motor  48  cover to close the fan module  42  at the inner shell portion  30 . The motor  48  has a pair of bearings, as will be appreciated by those skilled in the art. The fan  46  is configured with a center of gravity that is centered between the motor  48  bearings. This reduces force moments about the motor  48  bearings thus reducing stress to the motor  48  bearings. In essence, loads on the fan  46  are thus shared between the motor  48  bearings. 
         [0045]    In operation, the motor  48  rotates the fan  46  to draw air into the air inlet  74  of the scroll housing  50  through the intake grid  82  and the air inlet  74  in the outer shell portion  32  and distributes air out of the scroll housing  50  through the air outlet  76  or outlets and into the air flow channel  34  where the air is distributed about the head  24  of the user. Cutoffs (in some embodiments, inclined cutoffs as previously described) cut the air as the fan  46  moves the air within the scroll housing  50 . More specifically, as shown in the Figures, the present invention incorporates several air flow cutoffs in the scroll housing  50  to cut the air. A power supply is incorporated in the present invention to power the motor  48  to rotate the fan  46  via the motor  48  shaft. Preferably, the power supply is a rechargeable DC battery. Also preferred, the power supply is disposed within, i.e., integrated into, the helmet assembly  22 . In such a case, the power supply is referred to as an integral power supply. Alternatively, the power supply can be mounted to the body  26  of the user (not shown). The power supply powers the motor  48  through pulse width modulation (PWM) which will be discussed further below. The design of the scroll housing  50  provides more efficient movement of air with less power being required from the power supply overall. Furthermore, in addition to such reduced power requirements, the scroll housing  50  provides that sufficient air flow can be maintained with overall less air velocity. This results in a quieter helmet assembly  22 . 
         [0046]    With respect to the at least two air outlets  76 , the outer wall  70  of the scroll housing  50  is partitioned to define the air outlets  76 . In the preferred embodiment of the present invention having the at least two air outlets  76 , it is to be understood that the present invention is not limited to at least two air outlets  76 . That is, the present invention may include, for example, three or four air outlets  76 . The air outlets  76  provide a complete balance of air as the air is distributed from the scroll housing  50  about the head  24  of the user. To accomplish this, the helmet assembly  22  includes at least two helmet air exits  90 ,  92  in fluid communication with the air flow channel  34 . The air outlets  76  are in fluid communication with the at least two helmet air exits  90 ,  92  to distribute the air from the air outlets  76 , which is in the air flow channel  34 , toward the head  24  of the user. In the preferred embodiment of the present invention where the helmet assembly  22  includes the at least two helmet air exits  90 ,  92  it is not critical that the scroll housing  50  include at least two air outlets  76 . To the contrary, the scroll housing  50 , in these embodiments, may only have at least one air outlet  76 . Furthermore, the helmet assembly  22  may also have only one air exit. 
         [0047]    In an alternative embodiment, at least one air bleed valve (not shown) may be incorporated in the scroll housing  50  to influence the amount, or the volume, of air flowing into the air flow channel  34  from each of the air outlets  76 . This is shown in the &#39;019 patent to Diaz et al., which is hereby incorporated by reference. 
         [0048]    In the preferred embodiment, as best shown in  FIG. 2 , the air exits  90 ,  92  are a front air exit  90  and a rear air exit  92  in that they are disposed at a front section  94  and a rear section  96  of the helmet assembly  22 , respectively, to effectively distribute air toward both the face and neck of the user. However, in alternative embodiments, the air exits  90 ,  92  can be disposed in alternate locations to distribute air toward any portion of the user&#39;s head  24 . For instance, the air exits  90 ,  92  can be side air exits  90 ,  92  such that air is distributed toward the side of the user&#39;s head  24 . For descriptive purposes only, the present invention will be described below only in terms of front and rear air exits  90 ,  92  and will be numbered accordingly. More specifically, the front air exits  90  are disposed at the front section  94  for distributing air from the air flow channel  34  toward the front of the head  24  of the user, and the rear air exits  92  are disposed at the rear section  96  for distributing air from the air flow channel  34  toward the back of the head  24  of the user. 
         [0049]    Still referring to  FIG. 2 , the air flow channel  34  defined between the inner and outer shell portions  30 ,  32  terminates at the front section  94  with the front air exits  90 . More specifically, the inner and outer shell portions  30 ,  32  converge toward the front section  94  to define the front air exits  90 . The front air exits  90  may have an air deflector (not shown) defined between the outer shell portion  32  and the inner shell portion  30  wherein the outer shell portion  32  angles toward the inner shell portion  30  at the front air exits  90  for proper deflection of air toward the front of the head  24  of the user. Such an air deflector is best shown in the &#39;019 patent to Diaz et al., hereby incorporated by reference. The air flow channel  34  diverges upon approaching the front air exits  90 . The convergence and divergence of the air flow channel  34  maintains a balanced flow of air about the user&#39;s head  24 . Ultimately, this also has the effect of minimizing or even completely eliminating noise within the helmet assembly  22  due to the air flow. 
         [0050]    The rear air exits  92  are incorporated in a nozzle assembly  98  (also referred to as a duct  98  or a duct assembly  98 ). Referring to  FIG. 9 , the nozzle assembly  98  includes a nozzle  100  with rotatably adjustable nozzle tips  102 . The nozzle  100  is mounted to the scroll housing  50  such that a wall  104  of the nozzle  100  is disposed in the air flow channel  34  and diverts air from at least one of the air outlets  76  into at least one port  106 , preferably two. The ports  106  may be referred to herein as conduit-defining discharge members  106 , or simply discharge members  106 . The ports  106  feed air to the rotatably adjustable nozzle tips  102  and the rear air exits  92  are defined in the nozzle tips  102 . As shown in  FIG. 2 , the nozzle tips  102  and rear air exits  92  extend below the front air exits  90  and direct air against the neck of the user, when the personal protection system is mounted to the user. As described below, the rear air exits  92  also extend below a head support assembly  108  of the helmet assembly  22 . 
         [0051]    Referring to  FIG. 10 , each of the nozzle tips  102  includes a nozzle head  110  defining the rear air exits  92  of the nozzle tip  102 . Each of the nozzle tips  102  also includes a pair of snap-locking fingers  112  for rotatably locking the nozzle tip  102  to the nozzle  100 . Referring to  FIG. 11  along with  FIG. 10 , the nozzle  100  includes a inner flange  114  disposed in each of the ports  106  and the snap-locking fingers  112  are axially retained by the inner flange  114  once snap-locked to the nozzle  100 . The nozzle tip  102  includes an outer flange  116  that abuts a distal end of the nozzle  100  to further axially retain the nozzle tip  102 , while a cylindrical shoulder  118  of the outer flange  116  fits inside the port  106  to rotatably support the nozzle tip  102  therein. The snap-locking fingers  112  extend from the shoulder. In addition, a plurality of detent fingers  120  extend from shoulder to ride along a plurality of corrugations  122  defined in an inwardly protruding surface of the inner flange  114 . This allows the nozzle tips  102  to rotate in the nozzle  100  in a stepped and controlled manner to prevent incidental rotation of the nozzle tips  102 . The nozzle tips  102  can be adjusted to change the direction of airflow toward or away from the neck of the user, based on the user&#39;s preference. In alternative embodiments, an adjustable deflector (not shown) could be incorporated in the nozzle tips  102  to further vary the location on the user&#39;s neck at which the air is directed from the rear air exits  92 . 
         [0052]    The nozzle  100  is preferably formed of ABS, while the nozzle tips  102  are preferably formed of LEXAN® polycarbonate. Of course, the nozzle  100  and nozzle tips  102  may be formed of other suitable materials known to those skilled in the art. 
         [0053]    Referring to  FIGS. 12 and 13 , alternative nozzles  100  and adjustable air flow volume mechanisms for use therewith are shown. Referring first to  FIG. 12 , a first alternative nozzle  100  is shown as including an aperture  124 . The aperture  124  is adapted to slidably receive an arm  126  of an airflow closer  128  disposed in the air flow channel  34 . A user of the helmet assembly  22  may adjust the air flow volume out through the ports  106 , and subsequently through the rear air exits  92  by varying the position of the airflow closer  128 . By sliding the arm  126  in the aperture  124 , the user can adjust a position of a baffle  130  of the air flow closer. As the baffle  130  is adjusted toward the air outlet  76  of the scroll housing  50 , the air flow through the air outlet  76  to the nozzle  100  is reduced, and vice versa. The airflow closer  128  may be positioned at a fully open position, a fully closed position, or at any number of intermediate positions therebetween. 
         [0054]    Referring to  FIG. 13 , the nozzle  100  includes a nozzle vent  132  and the adjustable air flow volume mechanism is in the form of a slider  134 . The slider  134  is movable between a plurality of positions. In a wide open position, a slider vent  136  in the slider  134  is lined-up with the nozzle vent  132  in the nozzle  100 . As a result, a large air flow volume from the air outlet  76  of the scroll housing  50  is released from the nozzle  100  before reaching the ports  106 . This significantly reduces the air flow volume through the rear air exits  92 . In a fully closed position, the nozzle vent  132  is closed by a panel  138  of the slider  134  and the full air flow volume from the air outlet  76  in the scroll housing  50  is directed to the rear air exits  92 . A knob  140  is attached to the slider  134  through a slot in the nozzle  100  and is used by the user to vary the position of the slider  134  and control the air flow volume. 
         [0055]    A method of maintaining a constant volume of air flowing into the helmet assembly  22  during or throughout the entire use of the personal protection system  20  by the user is provided by the present invention. The method includes the step of selectively activating and deactivating the power supply as detailed in the &#39;677 patent, which is hereby incorporated by reference. 
         [0056]    Referring again to  FIG. 3 , an adjustable head support assembly  108  assists in minimizing the strain on the head  24  and the neck of the user. Strain and torque on the head  24  and neck of the user is minimized by maintaining the weight of the fan module  42  over the neck of the user even upon adjustment of the helmet assembly  22  to fit various sized heads  24 . The head support assembly  108  includes a rear support  142  that rigidly extends from the shell  28  and is connected to the rear section  96 . It is to be understood that the rear support  142  can be a separate part that is connected to the helmet assembly  22  or can be an integral part of the helmet assembly  22 . In the preferred embodiment, the rear support  142  is connected to and extends from the rear section  96  of the inner shell portion  30 . However, it is to be understood that the rear support  142  can connect to and extend from any portion of the shell  28 . 
         [0057]    Viscoelastic foam pads (not shown) may be applied to the helmet assembly  22  at various locations to provide a comfortable barrier between the user and the helmet assembly  22 . In the preferred embodiment, the materials used to form the helmet assembly  22 , particularly the materials used to form the shell  28 , scroll housing  50 , and the fan  46 , were selected based on their sound-dampening characteristics. The stiffness of these materials was selected to reduce vibration and change the frequency of transmitted sound to more appeasing frequencies. 
         [0058]    Referring back to  FIG. 1 , the personal protection system  20  includes a hood  144  for covering the helmet assembly  22 , which houses the head  24  of the user. The hood  144  operates as a filter medium to filter air between the user and the external environment as described in the &#39;019 patent, which is incorporated by reference. 
         [0059]    Referring now to  FIG. 14 , the present invention also includes a face shield  146  that permits the user to view through the hood  144  and the facial opening  38  of the helmet assembly  22 . The face shield  146  may include anti-reflective and/or anti-refractive coatings to enhance vision through the face shield  146 . The face shield  146  is mounted to the hood  144  such that the face shield  146  covers the facial section  36  and the facial opening  38  of the helmet assembly  22  once the user dresses into the personal protection system  20 . More specifically, the face shield  146  is attached to the hood  144  to maintain a complete barrier between the user and the external environment. The facial opening  38  of the helmet assembly  22  essentially receives the face shield  146 . Preferably, the facial section  36  of the helmet assembly  22  includes a hook-and-loop fastener to further facilitate attachment of the face shield  146  to the facial section  36  for covering the facial opening  38 . 
         [0060]    Referring to  FIG. 15 , the face shield  146  incorporated into the hood  144  or gown preferably includes at least one removable or peelable layer  150  that provides an easier and effective manner of removing debris accumulated on the face shield  146  during use. This will eliminate the need to wipe the face shield  146  of the accumulated debris during use. In the most preferred embodiment, multiple removable layers  150  are used. These removable layers  150  would be delivered to the user in a sterile fashion with the face shield  146  being sterilized between the removable layers  150  so that no contaminates are present or exposed after removing the removable layers  150  away from the face shield  146 . The removable layers  150  are transparent and preferably flexible. In one embodiment, the removable layers  150  are thin, flexible, and conform to the shape of the face shield  146 . Furthermore, air gaps between the removable layers  150  are minimized to reduce multiple reflected/refracted images. Preferably, the removable layers  150  are sterilized using gamma radiation. In the preferred embodiment, the face shield  146  and removable layers  150  are assembled. The face shield  146  and removable layers  150  are then sterilized with gamma radiation. The sterilized face shields  146  with removable layers  150  are then attached to the hood  144  in a clean room environment. The hood  144  or gown with the attached face shields  146  are then individually packaged and sterilized with ethylene oxide. 
         [0061]    However, in an alternative embodiment, the removable layers  150  may be sterilized with Ethylene Oxide (EtO) gas. In this embodiment, the removable layers  150  must be breathable for effective EtO gas sterilization. 
         [0062]    In one embodiment, the removable layers  150  are attached directly to the face shield  146  using a self-adhering method of attachment such as static forces, transparent adhesive, and the like. As shown, the removable layers  150  may include peel tabs  152  that the user or an assistant can grab to peel-away the removable layers  150  from the face shield  146 . The tabs  152  can be positioned at any portion of the removable layers  150  such as at the top for “peel down” removal, at the bottom for “peel up” removal, or at the side for “peel across” removal. Furthermore, each of the removable layers  150  may have multiple tabs  152 . The removable layers  150  preferably include anti-reflective and/or anti-refractive coatings to improve vision by reducing multiple images. 
         [0063]    In one embodiment, the removable layers  150  are formed from a 1 to 5 mil clear urethane film. In further embodiments, the removable layers  150  are formed of polyester, e.g., Mylar®, or other gamma radiation stable materials to reduce or eliminate air layers  150  between adjacent removable layers  150 . 
         [0064]    In an alternative embodiment, the removable layers  150  are thin and semi-rigid or rigid and conform to the shape of the face shield  146 , while still minimizing the air gap between adjacent removable layers  150 . The removable layers  150  may be formed as a semi-rigid or rigid film. In this embodiment, the removable layers  150  may be attached at a periphery of the face shield  146  in a non-continuous manner such as by adhesive, tape, spot-welding, static cling attachment, or other conventional methods of attachment. This allows EtO gas to penetrate the periphery for terminal sterilization between the removable layers  150 . In this embodiment, the removable layers  150  may be manufactured in a flat configuration and then wrapped to conform to the curvature of the face shield  146 , which minimizes the air gaps between the removable layers  150  to reduce unwanted images when looking through the face shield  146  and the removable layers  150 . The removable layers  150  in this embodiment may also include anti-reflective and/or anti-refractive coatings to improve vision and may also include tabs  152  to remove the removable layers  150 . 
         [0065]    In further embodiments, the removable layers  150 , whether thin and flexible or thin and semi-rigid or rigid, may be polarized using a polarized coating. The removable layers  150  may also include magnification coatings to improve the user&#39;s view. Magnification may be carried out solely by the removable layers  150 , or in alternative embodiments, magnification may be carried out by a combination of the removable layers  150  and the face shield  146 . In even further embodiments, magnification is carried out solely by the face shield  146 . In addition, the removable layers  150  may provide UV protection by using UV inhibiting films or adhesives. 
         [0066]    The face shield  146  may be packaged with multiple removable layers  150  ready for removal from the face shield  146  during use. However, in some instances it may be beneficial to provide a user with greater flexibility in selecting the types of removable layers  150  to be used, e.g., thin and flexible or thin and semi-rigid or rigid, or to provide the user the option of selecting whether the removable layers  150  will be used at all. To this end, each removable layer  150  (flexible, semi-rigid, or rigid) is packaged separately from the face shield  146  incorporated into the hood  144  or gown. As a result, the user can choose, which, and how many, of the removable layers  150  to attach to the face shield  146  prior to use. Alternatively, a removable layer  150  (flexible, semi-rigid, or rigid) may be separately packaged and formed with anti-reflective, anti-refractive, and/or magnification coatings to improve image quality for the user. In this instance, the coatings may work with complementary coatings on the face shield  146  to improve the image quality for the user, or the removable layer  150  may be the sole source of these coatings. 
         [0067]    In the event that the removable layers  150  are separately packaged, they will also be separately sterilized using either EtO gas sterilization, or preferably gamma radiation sterilization. When gamma radiation sterilization is used, the air layers  150  between adjacent removable layers  150  can be reduced or eliminated, which improves image quality through the removable layers  150 . The use of gamma stable materials to form the removable layers  150  also improves optical clarity. 
         [0068]    The present invention preferably includes a positioning and supporting system for assisting a single user in self-gowning as the user maintains sterility. This system is fully described in the &#39;019 patent to Diaz et al., hereby incorporated by reference. The present invention may also include a visual positioning system as disclosed in the &#39;019 patent to Diaz et al., hereby incorporated by reference. 
         [0069]    Obviously, many modifications and variations of the present invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims. In addition, the reference numerals in the claims are merely for convenience and are not to be read in any way as limiting.