Abstract:
Fire resistant door, glazing, and mullion frames include intumescent material at least partially embedded in the frame adjacent the door or glazing. Trim materials are positioned over the intumescent material to prevent tampering with and damage to the intumescent material while improving the aesthetic appearance of the frame. The jamb trim has a thickness that allows heat to be transmitted to the intumescent material in the event of a fire so that the intumescent material will expand and fill a clearance space between the frame and the door or glazing. The expanded intumescent material retards the passage of heat and, by sealing the clearance space, inhibits the transmission of smoke, flames and gases from one side of the door or glazing to the other. After expanding, the intumescent material will char and solidify, which may provide an added benefit of structural support for the door or glazing.

Description:
RELATED APPLICATIONS 
     This application is a division of and claims the benefit under 35 U.S.C. §121 from U.S. patent application Ser. No. 11/381,464, filed May 3, 2006, which is a continuation of and claims the benefit under 35 U.S.C. §120 from U.S. patent application Ser. No. 10/374,927, filed Feb. 25, 2003, now U.S. Pat. No. 7,059,092, which claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 60/360,191, filed Feb. 26, 2002. Each of the foregoing applications is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     This disclosure relates to fire resistant door frames, relite frames, sidelite frames, transom frames, borrowed light frames, and mullions, and to such structures that withstand positive-pressure fire testing necessary for enhanced fire code ratings. 
     In the construction of buildings and, more particularly, the construction of institutional and commercial buildings, it is common and sometimes necessary to include interior room and space walls with door openings and interior windows called “lights” or glazing. The openings for doors and glazing are usually first roughly framed in with wall studs. Door frames and glazing frame assemblies are then attached to the studs and the assemblies are finished with wallboard, doors, and glazing. 
     In many commercial building interiors, wooden interior doors and door frames are preferred over metal doors and frames because exposed wood surfaces enhance the aesthetics of the interior spaces. Wood framing and mullions (including light-to-light mullions and door-to-light mullions) are also commonly used for interior glass panels including relites, sidelites (a.k.a. sidelights), borrowed lights, transom lights, vision lights, and any other light-transmitting panel installed in a wall or door (collectively, “glazed openings”). To reduce costs, wood assemblies for doors and door frames are often constructed with a shaved wood veneer adhered to the exterior of a manufactured fiber core material, such as medium density fiberboard (“MDF”). High-quality wood assemblies use similar core materials, but with a solid wood facing or trim that is precision-cut, not shaved. Typically, solid wood facing is slightly thicker than veneer, making it more durable, stronger, and longer lasting than veneer assemblies. However, solid wood surfaces typically provide more fuel for a fire than veneer, which reduces fire resistance of the assembly. 
     Modern fire codes and architectural practices require doors and door frames to be constructed in accordance with designs that have undergone fire testing performed by accredited testing facilities in accordance with established standard test procedures. One widely recognized test procedure is a 45-minute positive-pressure test performed by Intertek Testing Services (ITS/Warnock Hersey) of Boxborough, Mass., USA for rating in accordance with the following standards: NFPA 252, CAN4-S104, UBC 7-2 1997, ISO 3008, and BS476 Part 22. Positive-pressure testing requires doors, door frames, glazed openings, and their frames and mullions to be tested as an assembly. The interior side of the assembly (facing toward the door when opened) is subjected to a furnace flame with positive pressure applied to the burn zone at a predetermined height from the bottom of the door. The tests permit only a limited amount of smoke to escape around the door and glazed openings. 
     In an attempt to meet positive-pressure testing requirements, known prior-art designs have included intumescent materials in the doors and door frames. When exposed to heat generated in a fire, intumescent materials quickly foam and expand, then char and solidify to provide a strong, fire-resistant seal that also inhibits the penetration of smoke around doors. Intumescent materials typically activate at temperatures in excess of 400° F., but may activate at higher or lower temperatures depending on the type of intumescent material used. 
     One known door frame design calls for workers at the construction site to apply adhesive-backed strips of graphite intumescent material against a door jamb surface called the rabbet (where the frame is stepped to receive the door). Such designs are subject to failure due to improper installation, tampering, and damage to the exposed intumescent material. Moreover, the only frames of this type known to comply with 45-minute positive-pressure testing are hollow metal frames. 
     Another known use of intumescent material is a door sold by VT Industries of Holstein, Iowa, USA that includes an intumescent strip embedded between a core of the door and a wood veneer along an edge of the door. However, to comply with 45-minute positive pressure testing, the VT Industries doors must be installed in a door frame that has been tested as an assembly with the VT Industries door. The only frames known to comply with 45-minute positive-pressure testing when used with the VT Industries door are metal frames to which intumescent material has been applied against the rabbet surface, as described above. Thus a need exists for a door frame assembly that complies with 45-minute positive-pressure test standards, which is more aesthetically pleasing and which does not expose the intumescent material to tampering and damage. 
     The present inventors have also recognized a need for an improved fire resistant sidelight frame. Summit Door, Inc., St. Paul, Minn., USA sells frames for sidelight openings that have successfully undergone 45-minute positive-pressure tests. This sidelite frame design uses intumescent strips inlaid against its top (header), bottom (sill), and sides (jambs) and between the glass panel and wooden stops that are fastened to the frame on both sides of the glass panel. This design requires the glass to be installed in the frame using metal glazing clips before the wooden stops are installed. The metal glazing clips are apparently necessary to provide support for the glass panel in the event of a fire. The metal glazing clips provide structural support for the glass panel, but add to the material cost as well as the time and cost involved in installing it. Thus there remains a need for aesthetically pleasing wood frames and mullions for glazed openings that will pass a 45-minute positive-pressure test without the need for expensive metal glazing clips. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, aspects, and advantages of the present invention are set forth in the following description, appended claims, and accompanying drawings wherein: 
         FIG. 1  is a front elevation view of an example doorway assembly configuration including framing assemblies in accordance with a preferred embodiment; 
         FIG. 2  is a enlarged broken sectional view of the doorway and light assembly of  FIG. 1  taken along line  2 - 2  of  FIG. 1 , including a sidelite frame and a door frame; 
         FIG. 3  is an enlarged cross section view showing detail of a right-side door jamb portion of the door frame of  FIG. 2 ; 
         FIG. 4  is a cross section view corresponding to  FIG. 3 , showing how an intumescent material of the right-side door jamb reacts to a fire to prevent the spread of smoke, flames, and heat between the door and the door frame; 
         FIG. 5  is an enlarged cross section view showing detail of a sidelite jamb portion of the sidelite frame of  FIG. 2 ; 
         FIG. 6  is an enlarged cross section view taken along line  6 - 6  of  FIG. 1 , showing detail of a transom mullion member of a glazing frame portion of the doorway and light assembly of  FIG. 1 ; and 
         FIG. 7  is a cross section view corresponding to  FIG. 5 , showing how an intumescent material insert of the sidelite jamb reacts to fire. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  is a front elevation view of a doorway and light assembly  10  installed in a wall  12  in an example configuration including framing assemblies in accordance with a preferred embodiment. With reference to  FIG. 1 , doorway and light assembly  10  includes a pair of doors  16  and  18  installed in a door frame  24  that includes a left side jamb  32 , a right side jamb  34 , and a head jamb  36 . Doorway and light assembly  10  also includes a sidelite  40  and a pair of transom lights  50  and  52  (collectively “glazed openings  56 ”). Glazed openings  56  are framed by glazing frame members including, for example, a sidelite sill  62 , a sidelite jamb  66 , a transom header  72 , and a transom mullion  76 . Persons skilled in the art will understand that glazed openings  56  can be arranged in a variety of configurations and sizes, and include other types of glazed openings, such as, for example, relites, doorlites, and any other glass panel installed in a wall or door. Each of these glazed openings includes glazing frame assemblies that can be constructed in accordance with the present invention, embodiments of which are described below in detail. 
       FIG. 2  is a enlarged broken sectional view of doorway and light assembly  10  taken along line  2 - 2  of  FIG. 1 . With reference to  FIG. 2 , doors  16  and  18  are supported on hinges (not shown), which are attached to respective left and right side door jambs  32  and  34  so that doors  16  and  18  open inwardly in the direction shown by arrows  82  and  84 . When closed, doors  16  and  18  are received in a rabbet  90  that extends along respective left and right door-side surfaces  92  and  94  of door jambs  32  and  34 , as well as along a downwardly facing door-side surface (not shown) of head jamb  36 . Rabbet  90  is bounded by a stop  100  against which doors  16  and  18  abut when closed. Stop  100  preferably includes left and right applied stops  102  and  104 , which are typically installed at the construction site by nailing or otherwise fastening to respective left and right side door jambs  32  and  34 . To facilitate installation, left and right applied stops  102  and  104  are preferably T-stops that include tongues  106  and  108  sized to fit in respective stop channels  112  and  114  formed in respective left and right door-side surfaces  92  and  94 . In alternative embodiments (not shown), the stops are formed integrally with the side jamb and head jamb members  32 ,  34 , and  36  or omitted altogether. 
     A flexible smoke seal strip  120  is applied to and extends along stop  100 . Smoke seal strip  120  compresses when doors  16  and  18  are closed against it, to inhibit smoke from passing between doors  16  and  18  and door frame  24  in the early stages of a fire. A preferred smoke seal material is an edge sealing system sold under the trademark S88™ by Pemko Manufacturing Company of Ventura, Calif., USA. Persons skilled in the art will understand that many other smoke seal products exist and would be suitable for use with embodiments of the invention. 
     Continuing with reference to  FIG. 2 , sidelite  40  includes a sidelite glass  130  supported by sidelite jamb  66  and left side door jamb  32 . Left side jamb  32  in this example is also considered a mullion because it divides a door and a sidelite, rather than being mounted to a wall. Grouped together, sidelite jamb  66 , left side jamb/mullion  32 , sidelite sill  62 , and a sidelite head  64  ( FIG. 1 ) are considered a glazing frame  134 . Sidelite glass  130  is secured to glazing frame  134  by glazing stops  138  that are attached to jamb side surfaces  142  of glazing frame  134  during installation of sidelite glass  130 , to thereby grasp or snugly pinch sidelite glass  130  between adjacent pairs of glazing stops  138 . 
     Sidelite jamb  66  and right side door jamb  34  include drywall grooves  148  sized to receive edges of drywall panels. For clarity, drywall panels and wall studs are omitted in  FIG. 2 , but shown in  FIGS. 3 and 4 . Skilled persons will understand that many other methods and means can be used for attaching jambs  66  and  34  to walls, studs, and drywall panels for a quality appearance. For example, in one alternative embodiment (not shown) drywall grooves  148  are moved to the edges of jambs  66  and  34  to create a T-shape that fits flush with drywall panels. In another alternative embodiment (not shown), drywall grooves  148  are omitted entirely for a flush mounted jamb called a “flatjamb.” In each alternative embodiment, applied trim can be used to cover the seams between the jamb and the drywall panels. 
       FIG. 3  is an enlarged cross-sectional view showing detail of right side door jamb  34  and wall  12 . With reference to  FIG. 3 , wall  12  includes a metal C-shaped wall stud  152  that extends vertically to support a pair of drywall panels  156  and  158 . Door jamb  34  includes a fire resistant core  166  of material such as a fire resistant medium density fiberboard (“MFMDF”) having a “Class 1” Underwriters Laboratory rating. In a preferred embodiment, core  166  is made of a solid piece of MFMDF material having a grain structure aligned with the long dimension of jamb  34  so that the fibers extend generally perpendicular to the section plane of  FIG. 3 . Orienting the fibers of core  166  in this direction increases the holding power of screws  170  that are used to attach jamb  34  to wall stud  152  and screws used to attach a hinge (not shown) to jamb  34 . 
     The term “core” as used herein is not limited to solid cores, however, and is used herein to denote any structural member over which other materials are applied, regardless of whether solid, hollow, or having other materials mixed throughout, inserted within, or surrounded by core  166 . Persons skilled in the art will also understand that materials other than MFMDF may also be suitable for use in core  166 . The primary design criteria for core  166  are structural support, dimensional stability, fire resistance, holding power for screws and other fasteners, low cost, and ability to be cut into various shapes and sizes. 
     A process of making jamb  34  includes applying an inside face trim  180  against an inside face surface  182  of core  166 . An outside face trim  184  is similarly applied to an outside face surface  186  of core  166 . Inside and outside face trim  180  and  184  are preferably made of solid cut hardwood panels that are glued or otherwise adhered to respective inside and outside face surfaces  182  and  186 . However, skilled persons will understand that other materials such as, for example, soft woods and veneers may also be used, as well as non-wood materials such as metal or plastic. Attachment methods other than gluing may also be used to attach face trim  180  and  184  to core  166 . Once inside and outside face trim  180  and  184  have been securely adhered to core  166 , a dado  192  is then cut or otherwise formed in a jamb side surface  194  of core  166  proximal of rabbet  90 . Dado  192  is formed longitudinally in core  166  so that it runs the entire length of jamb  34  and rabbet  90 . A strip of intumescent material  200  is then positioned in dado  192  and preferably glued or adhered to snugly fit and fill dado  192 . Dado  192  and intumescent material  200  may be made between approximately 0.625 inch (⅝″) and 1.750 inches wide and approximately 0.0625 inch ( 1/16″) and 0.1875 inch ( 3/16″) deep/thick, and are preferably approximately 1.5000 inch wide and 0.125 inch (⅛″) deep/thick, but may be of other thicknesses and widths, as necessary to fit the application and the door size. To simplify assembly and manufacture, intumescent material  200  preferably includes a preapplied adhesive that is protected by a removable backing paper, which is removed before application of intumescent material  200  within dado  192 . According to one embodiment, the intumescent material  200  is raw intumescent material, not plastic wrapped or otherwise encapsulated by a plastic sleeve. 
     After intumescent material  200  has been fitted in dado  192 , the partly assembled jamb undergoes a sanding operation. Sanding is performed by cross sanding against jamb side surface  194  and ends  204  and  206  of respective inside and outside face trim  180  and  184  in the direction shown by arrows  210 . In a preferred embodiment, a 24-grit sandpaper is used to cross-sand at a 45-degree angle to and across the longitudinal axis of jamb  34 . The sanding operation ensures a flush surface at the junction between jamb side surface  194  of core  166 , an outer surface  212  of intumescent material  200 , and ends  204  and  206  of face trim  180  and  184 . A flush and planar surface facilitates adhesion of a jamb trim layer  216 , which is applied after the sanding operation. As with face trim  180  and  184 , jamb trim  216  is preferably made of cut hardwood and adhered or glued to core  166 , intumescent material  200 , and face trim  180  and  184 , but may also be made of other materials and attached in other ways within the scope of the present invention. The sanding operation described above should cause little or no abrasion of outer surface  212  of intumescent material  200 . Abrasion of intumescent material  200  is undesirable because of a coating on outer surface  212  of intumescent material  200  that inhibits absorption of water and other elements that may degrade intumescent material  200  over time. Consequently, it is desirable for dado  192  to be cut slightly deeper than the thickness of intumescent material  200  so that the sanding operation will primarily affect the other components of jamb  34 . 
     A preferred intumescent material  200  is sold by BASF Aktiengesellschaft of Ludwigshafen, Germany under the trademark PALUSOL-104®. PALUSOL-104 includes a protective coating of the type described above. Intumescent materials other than PALUSOL-104, whether coated or uncoated, may also be suitable for use in embodiments of the invention, for example, Graphite Intumescent Seal (GIS) sold by 3M Company of St. Paul, Minn., USA and HSS2000 Hot Smoke Seal sold by Pemko Manufacturing Company of Ventura, Calif., USA. Preferably, intumescent material  200  should be of the “hard puff” variety to ensure that door frame  24  is quickly sealed in the event of a fire. If an intumescent material that does not include a protective coating is used, it may be desirable to abrade outer surface  212  to encourage adhesion and close contact between jamb trim  216  and outer surface  212  of intumescent material  200 . 
     To complete construction of jamb  34 , a backing trim  224  is applied to back surfaces  226  of core  166 . Stop channel  114  may also be formed centrally and longitudinally along the door side of jamb  34 . As described above, applied stop  104  is preferably installed at the construction site and typically by nailing applied stop  104  to core  166 . After installation of applied stop  104 , smoke seal strips  120  may be installed adjacent stop  104 , as described above with reference to  FIG. 2 . 
       FIG. 4  shows how intumescent material  200  reacts to a fire burning inside of doorframe  24 . At an activation temperature, intumescent material  200  begins to build pressure within dado  192 . With sufficient pressure, intumescent material  200  expands and bursts through jamb trim  216  along rabbet  90  and through a seam  230  ( FIG. 3 ) between jamb trim  216  and inside face trim  180 . To facilitate acceptable timing, placement, and direction of expansion of intumescent material  200 , the thicknesses of face trim  180  and jamb trim  216  are carefully selected, as is the location of dado  192  in relation to an inside face surface  234  of inside face trim  180 . 
     More particularly, jamb trim  216  has thickness that is preferably in range of approximately 0.03125 inch ( 1/32″) to 0.09375 inch ( 3/32″), and more preferably approximately 0.125 inch (⅛″). The thickness of jamb trim  216  is selected so that jamb trim  216  will bulge or fracture when intumescent material  200  expands, thereby allowing intumescent material  200  to fill and seal a clearance gap  240  ( FIG. 2 ) when intumescent material  200  expands. The location and direction of expansion of intumescent material  200  prevent smoke, flames, and heat from passing between door  18  and jamb  34 . Additionally, expansion of intumescent material  200  forms a protective insulating plug  244  that further fills and protects the junction between door  18  and door frame  24 . 
     As noted above, dado  192  is preferably positioned in proximity to face surface  234  to increase heat transmission through inside face trim  180  and heat absorption by intumescent material  200 . Preferably, dado  192  extends to within between approximately 0.0625 inch ( 1/16″) and 0.1875 inch ( 3/16″) of face surface  234  of inside face trim  180 . It is also desirable that dado  192  extend into face trim  180 , rather than being cut entirely into core  166 . Extending dado  192  into inside face trim  180  facilitates timing and direction of expansion of intumescent material  200  because inside face trim  180  is consumed during early stages of a fire, whereas the fire-resistant core  166  would be likely to insulate and inhibit expansion of intumescent material  200  in a direction perpendicular to face  234 . To remain structurally sound during the manufacturing process, inside face trim  180  is preferably selected to have a thickness in the range of 0.125 inch (⅛″) and 0.250 inch (¼″). Thinner face trim  180  can shatter during manufacturing when dado  192  is being cut, whereas thicker face trim  180  is more expensive and provides more fuel to burn during a fire. Furthermore, thicker face trim impedes the ability to engage a screw in core  166 , thereby reducing the holding power of screws in face  234  of jamb  34  in the event of a fire that consumes inside face trim  180 . A similar issue with respect to the holding power of screws arises in the context of a hinge plate (not shown) attached to jamb  34  at rabbet  90 . When attaching a hinge plate, screws should be selected with a length that will penetrate fully through intumescent material  200  and into core  166  so that the screws will hold in the event of a fire, even when jamb trim  216  is consumed and intumescent material  200  expands. Accordingly, it is desirable to minimize the thickness of jamb trim  216  and intumescent material  200  as much as possible without affecting the sealing function performed by intumescent material  200  during a fire. 
       FIG. 5  is an enlarged cross section view of sidelite jamb  66  of glazing frame  134  of  FIG. 2  showing detail of wall  12 . Sidelite jamb  66  is attached to a second wall stud  250  with a screw  254  and fitted to inside and outside drywall panels  156  and  158  in a manner similar to right side jamb  34  ( FIG. 3  and alternative flatjamb embodiments described above). A core  260 , a glass-side trim  262 , a backing trim  264  and inside and outside face trim  266  and  268  are assembled in the same manner as door jamb  34 , but without the laminated and concealed strip of intumescent material  200 . To minimize parts and inventories required in a manufacturing operation, sidelite jamb  66  and door jamb  34  may be made to have the same general shape, size, trim thicknesses, and materials. A glazing dado  284  is cut into a glass-side  288  of sidelite jamb  66 . Glazing dado  284  is formed along the length of sidelite jamb  66  and is sized to fit a strip of intumescent material  300  (hereinafter “glass end intumescent  300 ”), which is adhesively secured in glazing dado  284  before sidelite glass  130  is installed. Glass-end intumescent  300  is preferably an adhesive backed strip of PALUSOL-104 ranging between approximately 0.500 inch and 1.5 inch wide and between approximately 0.0625 inch ( 1/16″) and 0.1875 inch ( 3/16″) thick, and are preferably 0.750 inch (¾″) wide and 0.125 inch (⅛″) thick. Other types of intumescent material may be used as an alternative to PALUSOL-104. 
     Sidelite glass  130  and any other glazing of doorway and light assembly  10  may be made of any of a variety of types of glass, including tempered glass, security glass, insulated glass, double pane glass, and others. Special temperature rise glass may be used for sidelite glass  130  and other glazing members to increase fire resistance and enhance positive-pressure test performance. A suitable temperature rise glass is made by Pilkington plc of St. Helens, United Kingdom under the name PYROSTOP™ and sold in the United States by Technical Glass Products of Kirkland, Wash. 
     A pair of adjacent glazing stops  138   a  and  138   b  are nailed into sidelite jamb  66  using finishing nails  310  to support sidelite glass  130  in glazing frame  134  ( FIG. 2 ). Glazing stops  138   a  and  138   b  are preferably made of hardwood and may optionally be treated with a fire-retardant coating. However, other materials such as plastic or metal may also be suitable. Glazing stops  138   a  and  138   b  may be made with an angled face, as shown, or with a square or rectangular cross section. Inside and outside glazing stop strips of intumescent material  320  and  322  (hereinafter “inside IM strip  320 ” and “outside IM strip  322 ”) are adhered to stop faces  326   a  and  326   b  of respective inside and outside glazing stops  138   a  and  138   b  and interposed between respective glazing stops  138   a  and  138   b  and sidelite glass  130 . Inside and outside IM strips  320  and  322  extend adjacent to sidelite glass  130  preferably slightly beyond distal edges  336  of glazing stops  138   a  and  138   b  to reduce a shielding and insulating effect of glazing stops  138   a  and  138   b , thereby allowing IM strips  320  and  322  to more quickly activate in the event of a fire. IM strips  320  and  322  are preferably made of PALUSOL-104 that is wrapped in plastic sleeves  340  and  342  to enhance aesthetic appearance and discourage tampering where IM strips  320  and  322  extend from glazing stops  138   a  and  138   b.    
     Pre-assembly during manufacturing of glass-end intumescent  300  and inside and outside IM strips  320  and  322  to components of glazing frame  134  reduces installation errors at construction sites, ensures proper placement of intumescent material for optimal performance, and prevents breakage of intumescent strips that can otherwise occur if shipped separately from glazing frame components. 
       FIG. 6  is an enlarged cross sectional view taken along line  6 - 6  of  FIG. 1 , showing detail of a transom mullion member  76  of glazing frame  134 . With reference to  FIG. 6 , transom mullion  76  (hereinafter “mullion”) includes two sets of glazing stops  360   a / 360   b  and  362   a / 362   b , two strips of glass end intumescent  368  and  370 , and two sets of inside and outside IM strips  372   a / 372   b  and  374   a / 374   b , for securing right and left transom glass panels  378  and  380 , respectively. Other than the absence of features for attachment to a wall  12 , mullion  76  is similar to sidelite jamb  66  in its arrangement and assembly at the interface with glazing  378  and  380  (as at the interface between sidelite jamb  66  and sidelite glass  130 ), but functions to divide two adjacent panes of glass  378  and  380  where sidelite jamb  66  does not. 
       FIG. 7  is a cross sectional view corresponding to  FIG. 5  showing how glass end intumescent  300  and inside and outside IM strips  320  and  322  ( FIG. 5 ) of sidelite jamb  66  react to fire to expand along sidelite glass  130 . Due to their proximity, glass end intumescent  300  bonds with expanded IM strips  320  and  322 , which then char to form a strong, unitary, fire-resistant U-shaped clip  400  that holds sidelite glass  130  in place. This clip-forming effect eliminates the need for costly metal glazing clips used in prior art glazing frames, which are time consuming and, therefore, expensive to install. Mullion  76  benefits from the same shielding and bonding effects as sidelite jamb  66  due to their similar designs. 
     Door frame assemblies made in accordance with the preferred embodiments described herein have been tested and certified by Underwriters Laboratories Inc. to meet 20-minute and 45-minute positive pressure test requirements under UL 10C (1st Edition) and UBC 7-2 (1997) Parts I and II. Glazing frame assemblies made in accordance with the preferred embodiments described herein have been tested and certified by Underwriters Laboratories Inc. to meet 45-minute and 60-minute positive pressure test requirements under ANSI/UL 263 (13th Edition). 
     Persons skilled in the art will understand that the principles of the above-described embodiments of the invention are readily applied to door frames and glazing frames of a variety of shapes, sizes, configurations, and materials. It will also be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. The scope of the present invention should, therefore, be determined only by the following claims.