Forcible Entry Demonstrations
Air-blast Resistant Window Systems
Appendix A Terminology
out of the frame. This is primarily due to the glass shards being retained by the film, (few
shards available to cause lacerations and penetrating injuries) and the glass/film
combination has greater mass and will therefore not penetrate as far into the occupied
space. A benefit of this solution is that it does not increase the load transmitted to the
mullions and frame.
Dry glazing refers to window bites which rely on the depth of overlap between the glass
and the window frame to keep the glass in place, rather than a structural silicone sealant.
Filmed glass is untreated glass which has a layer of security film installed at the interior
surface of the glass.
Heat Strengthened Glass (HS)
Heat strengthened glass is produced by heating annealed glass to temperatures of
approximately 1150 degrees Fahrenheit then rapidly cooling both top and bottom
surfaces simultaneously. This locks the surfaces of the glass in a state of high
compression and the central core in compensating tension, with neutral layers separating.
Heat strengthened glass lies mid-range between annealed glass and thermally tempered
glass both in overall strength and in breakage patterns.
The break patterns for heat strengthened glass very widely depending on the surface
compression and surface quality. On the low end of the range the breakage is similar to
annealed without the points; on the high end of the range the breakage is difficult to
distinguish from thermally tempered glass. Because of this, firefighters may not
recognize glass as heat strengthened even after breaking it.
Due to its increased strength, heat strengthened glass may be found in larger window
panes or in windows of buildings in high wind areas.
Insulating glass unit (IGU)
IGUs are windows which have two panes of glass separated by an air gap. These
window types are generally used for sound or climate control and are found in areas of
the United States with more extreme environments or high sound areas such as around
airports or rail lines.
The glass in IGUs can be any of the
normal glass types (or a combination of
glass types) and can be either monolithic
or laminated. In air-blast resistant
applications, IGUs will have a
monolithic outer pane (exterior to the
building) and a laminated inner pane
(interior to the building.)
Insulating Glass Unit
Insulating Glass Unit with
with Laminated Glass