INTRODUCTION 1

1.1 PURPOSE AND OVERVIEW 
The purpose of this primer is to introduce concepts that can help building designers, 
owners, and state and local governments mitigate the threat of hazards resulting 
from terrorist attacks on new buildings. This primer specifically addresses four high-
population, private-sector building types: commercial office, retail, multi-family 
residential, and light industrial. However, many of the concepts presented here are 
applicable to other building types and/or existing buildings. The focus is on 
explosive attack, but the text also addresses design strategies to mitigate the effects of 
chemical, biological, and radiological attacks. 
Designing security into a building requires a complex series of trade-offs. Security 
concerns need to be balanced with many other design constraints such as 
accessibility, initial and life-cycle costs, natural hazard mitigation, fire protection, 
energy efficiency, and aesthetics. Because the probability of attack is very small, 
security measures should not interfere with daily operations of the building. On the 
other hand, because the effects of attack can be catastrophic, it is prudent to 
incorporate measures that may save lives and minimize business interruption in the 
unlikely event of an attack. The measures should be as unobtrusive as possible to 
provide an inviting, efficient environment that does not attract undue attention of 
potential attackers. Security design needs to be part of an overall multi-hazard 
approach to ensure that it does not worsen the behavior of the building in the event 
of a fire, earthquake, or hurricane, which are far more prevalent hazards than are 
terrorist attacks. 
Because of the severity of the types of hazards discussed, the goals of security-oriented 
design are by necessity modest. With regard to explosive attacks, the focus is on a 
damage-limiting or damage-mitigating approach rather than a blast-resistant 
approach. The goal is to incorporate some reasonable measures that will enhance the 
life safety of the persons within the building and facilitate rescue efforts in the 
unlikely event of attack. 
It is clear that owners are becoming interested in considering man-made hazards 
for a variety of reasons including the desire to: 
. _ attract more tenants or a particular type of tenant, 
. _ lower insurance premiums or obtain high-risk insurance, 

INTRODUCTION
. _	reduce life-cycle costs for operational security measures, and 
. _ limit losses and business interruption. Protection against terrorist attack is 
not an all-or-nothing proposition. Incremental measures taken early in design may 
be more fully developed at a later date. With a little forethought regarding, for 
instance, the space requirements needed to accommodate additional measures, 

the protection level can be enhanced as the need arises or the budget permits after 
construction is complete. 
This primer strives to provide a holistic multi-disciplinary approach to security design 
by considering the various building systems including site, architecture, structure, 
mechanical and electrical systems and providing general recommendations for the 
design professional with little or no background in this area. 
This is one of a series of five FEMA primers that address security issues in high-
population, private-sector buildings. It is the intent of FEMA that these reports will 
assist designers, owners, and local/state government officials in gaining a solid 
understanding of man-made hazards. These reports will also discuss current state-of-
the-art methods to enhance protection of the building by incorporating low-cost 
measures into new buildings at the earliest stages of site selection and design. 
Best practices recommended in this primer are listed below. 
  Place building as far from any secured perimeter as practical.   
Secure the perimeter against vehicular intrusion using 
landscaping or barrier methods.   Use lightweight nonstructural 
elements on the building exterior and interior.   Place 
unsecured areas exterior to the main structure or in the exte
rior bay.   Incorporate measures to resist progressive collapse.   Design exterior 
window systems and cladding so that the framing, 
connections, and supporting structure have a lateral-load-resistance that is equal 
to or higher than the transparency or panel.   Place air intakes as far above the 
ground level as practical. 
 	Physically isolate vulnerable areas such as the entries and delivery 
areas from the rest of the structure by using floor-to-floor walls in 
these areas.

 	Use redundant, separated mechanical/electrical control systems. 
INTRODUCTIO


1.2 	CONTENTS AND ORGANIZATION OF THE REPORT 
This report provides basic qualitative and descriptive information characterizing 
potential terrorist threats: the effects of terrorist-caused explosions or releases of 
chemical, biological, and radiological (CBR) agents; and measures that can be taken 
to limit and mitigate their impacts on buildings and their occupants. 
Because explosive attacks are expected to remain the dominant terrorist threat, most 
of the guidance in the document relates to explosions and limiting their effects. In 
addition to descriptive information and guidance, each chapter identifies references 
for further reading.  Chapter 2 focuses principally on bomb (explosion) threats, likely 
targets, and likelihood of occurrence.  Weapons effects are described in Chapter 3, 
which discusses blast pressure waves, initial blast forces, and the decay of these forces 
with time and distance.  Chapter 4 focuses on damage caused by explosions, 
including damage mechanisms for various building elements and systems, including 
both structural and nonstructural components. Topics include (1) progressive 
collapse, (2) comparisons with forces imposed by other extreme loads, such as 
earthquakes and wind storms, and (3) the potential extent and distribution of deaths 
and injuries resulting from various damage mechanisms.  Design approaches to limit 
or mitigate damage caused by bomb attacks are described in Chapter 5. Goals include 
preventing collapse (at least until the building can be fully evacuated) and reducing 
the effects of flying debris. Security measures described include:  (1) preventing an 
attack, (2) delaying an attack, and (3) mitigating the effects of these attacks. 
The heart of the document is Chapter 6, which contains extensive qualitative design 
guidance for limiting or mitigating the effects of terrorist attacks, focusing primarily 
on explosions, but also addressing chemical, biological, and radiological attacks. 
Checklists of mitigation measures are provided at the end of each major section.  Site 
and layout design guidance is provided in Section 6.1. Important concepts are stand-
off distance from the perimeter property line, controlled access zones, and anti-ram 
barriers, which can be either passive or active.  Section 6.2 describes architectural 
issues and attributes affecting the impact of explosions on buildings. The primary 
focus is on building shape, placement, exterior ornamentation, and the functional 
layout of the interior. Structural design issues are discussed in Section 6.3. Topics 
include (1) methods to prevent progressive collapse; (2) the selection of a building 
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structural system, including desirable attributes of the system; (3) structural layout 
(the placement of structural elements); (4) design methods, including the 
relationship between security design and design for conventional loads; and (5) the 
design of critical structural elements, focusing on the exterior frame, roof system, 
floor system, interior columns, and interior walls.  Section 6.4 addresses the building 
envelope; i.e., exterior walls and cladding, window systems, and other openings. 
Specific guidance is provided on exterior wall and cladding design. Window design is 
given special consideration, including glass design, mullion design, and frame and 
anchorage design. Guidance is also given on wall design, multi-hazard 
considerations, and the design of other openings (doors and louvers). Issues relating 
to the design and placement of mechanical and electrical systems are described in 
Section 
6.5. Topics addressed include emergency egress routes, air intakes, emergency power 
systems, fuel storage, ventilation systems, the fire-con-trol center, emergency 
elevators, the smoke and fire detection and alarm systems, the sprinkler and 
standpipe system, smoke-control systems, and the communication system. Finally, 
Section 6.6 addresses  issues specific to chemical, biological, and radiological 
protection.  Issues discussed include air intakes, mechanical areas, return air systems, 
vulnerable internal areas (lobbies, loading docks, and mail sorting areas), zoning of 
HVAC systems, positive pressurization, air-tightness, filtration systems, detection 
systems, management of emergency response using the fire/HVAC control center, 
and evolving technologies for CBR prevention. 
Chapter 7 discusses special considerations for multi-family residential buildings, 
buildings that include retail uses, and light-industrial buildings. Chapter 8 
discusses cost issues, including some general suggestions on prioritizing potential 
security enhancements.


1.3 FURTHER READING 
Other recently issued FEMA documents related to man-made hazards are listed 
below. 
Federal Emergency Management Agency, FEMA 426, Reference Manual to Mitigate 
Potential Terrorist Attacks Against Buildings. 
Federal Emergency Management Agency, FEMA 428, Primer for Designing Safe School 
Projects in Case of Terrorist Attacks. 
Federal Emergency Management Agency, FEMA 429, Primer for Terrorist Risk Reduction 
in High Occupancy Buildings. 
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Federal Emergency Management Agency, FEMA 430, Security Component for Architectural 
Design. 
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INTRODUCTIO