FEMA 453 Design Guidance for Shelters and Safe Rooms

decides not to chance fate and constructs a shelter). A collection
of factors could include the type of hazard event, probability of
event occurrence, severity of the event, probable single and aggregate
annual event deaths, shelter costs, and results of computer
models that evaluate the benefits and costs of the shelter project.
1.2 PotentiaL tHreats
Rather than identify a specific threat, this document provides
general guidance that will address different types of building
construction and the reasonable mitigative measures to provide
a secure shelter. However, it is important for building owners and
design professionals to understand the potential threats to which
buildings may be exposed. This section provides an overview of
manmade threats.
The term “threat” is typically used to describe the design criteria
for manmade disasters (technological accident) or terrorism.
Identifying the threats for manmade threats can be a difficult
task. Because they are different from other natural hazards such
as earthquakes, floods, and hurricanes, manmade threats are difficult
to predict. Many years of historical and quantitative data, and
probabilities associated with the cycle, duration, and magnitude of
natural hazards exist. The fact that data for manmade threats are
scarce and that the magnitude and recurrence of terrorist attacks
are almost unpredictable makes the determination of a particular
threat for any specific site or building difficult and largely subjective.
Such asymmetrical threats do not exclusively target buildings
and may employ diversionary tactics to actually direct occupants to
a primary attack instrument.
With any manmade threat, it is important to determine who has
the intent to cause harm. The aggressors seek publicity for their
cause, monetary gain (in some instances), or political gain through
their actions. These actions can include injuring or killing people;
destroying or damaging facilities, property, equipment, or resources;
or stealing equipment, material, or information.
1-4 design considerations