FEMA 453 Design Guidance for Shelters and Safe Rooms

Although operational security measures can drastically limit
the size of the explosive device that could be introduced onto
a building site, there is no means of limiting the size of the explosive
that could be contained within a vehicle traveling on the
surrounding streets or roadways.
Explosives weigh approximately 100 pounds per cubic foot and, as
a result, the maximum credible threat corresponds to the weight
of explosives that can be packaged in a variety of containers or
vehicles. The Department of Defense (DoD) developed a chart to
help indicate the weight of explosives and deflagrating materials
that may reasonably fit within a variety of containers and vehicles
(see Table 1-1). The table also indicates the safe evacuation distances
for occupants of conventional unreinforced buildings,
based on their ability to withstand severe damage or resist collapse.
Similarly, Table 1-1 indicates the safe evacuation distance
for pedestrians exposed to explosive effects based on the greater
of fragment throw distance or glass breakage/falling glass hazard
distance. Because a pipe bomb, suicide belt/vest, backpack, and
briefcase/suitcase bomb are specifically designed to throw fragments,
protection from these devices may require greater safe
evacuation distances than an equal weight of explosives transported
in a vehicle. Table 1-2 shows safe evacuation distances for
liquefied petroleum gas (LPG) threats.
1-6 design considerations