FEMA 453 Design Guidance for Shelters and Safe Rooms

mechanism at the base of the window to hold the excess curtain
material. The blast curtain with curtain rod attachment and sill
trough differ largely from one manufacturer to the next. The
curtain fabric, material properties, method of attachment, and
manner in which they operate all vary, thereby providing many
options within the overall classification of blast curtains. This fact
makes blast curtains applicable in many situations.
Blast curtains differ from standard curtains in that they do not
open and close in the typical manner. Although blast curtains are
intended to remain in a closed position at all times, they may be
pulled away from the window to allow for cleaning and blind or
shade operation. However, the curtains can be rendered ineffective
if installed such that easy access would provide opportunity
for occupants to defeat their operation. The color and openness
factor of the fabric contributes to the amount of light that is transmitted
through the curtains and the see-through visibility of the
curtains. Although the color and weave of these curtains may be
varied to suit the aesthetics of the interior décor, the appearance
of the windows is altered by the presence of the curtains.
The curtains may either be anchored at the top and bottom of
the window frame or anchored at the top only and outfitted with
a weighted hem. The curtain needs to be extra long, with the surplus
either wound around a dynamic tension retainer or stored in
a reservoir housing. When an explosion occurs, the curtain feeds
out of the receptacle to absorb the force of the flying glass fragments.
The effectiveness of the blast curtains relies on their use
and no protection is provided when these curtains are pulled away
from the glazing (see Figure 2-15).
2- Structural deSign criteria