FEMA

Risk Management Series

Incremental Protection for 

Existing Commercial Buildings 

from Terrorist Attack

Providing Protection to People and Buildings

FEMA 459 / April 2008

U.S. AIR FORCE

Risk Management Series

Incremental Protection 

for Existing Commercial 

Buildings from Terrorist 

Attack

Providing Protection to People and Buildings

FEMA 459 / April 2008
Any opinions, findings, conclusions, or recommendations 

expressed in this publication do not necessarily reflect the views of 

FEMA. Additionally, neither FEMA nor any of its employees makes 

any warranty, expressed or implied, or assumes any legal liability 

or responsibility for the accuracy, completeness, or usefulness of 

any information, product, or process included in this publication. 

Users of information from this publication assume all liability 

arising from such use.
FOREWORD AND ACKNOWLEDGMENTS

FOREWORD AND ACKNOWLEDGMENTS 

BACKGROUND

T he Federal Emergency Management Agency (FEMA) developed 

FEMA 459, Incremental Protection for Existing Commercial Buildings 

from Terrorist Attack, to provide guidance to owners of existing 

commercial buildings and their architects and engineers on security and 

operational enhancements to address vulnerabilities to explosive blasts 

and chemical, biological, and radiological hazards. It also addresses how 

to integrate these enhancements into the ongoing building maintenance 

and capital improvement programs. These enhancements are intended to 

mitigate or eliminate long-term risk to people and property. 

FEMA’s Risk Management Series publications addressing security risks 

are based on two core documents: FEMA 426, Reference Manual to Mitigate 

Potential Terrorist Attacks Against buildings, and FEMA 452, Risk Assessment: 

A How-To Guide to Mitigate Potential Terrorist Attacks Against Buildings. 

FEMA 426 provides guidance to the building science community of 

architects and engineers on reducing physical damage caused by terrorist 

assaults to buildings, related infrastructure, and people. FEMA 452 

outlines methods for identifying the critical assets and functions within 

buildings, determining the potential threats to those assets, and assessing 

the building’s vulnerabilities to those threats. This assessment of risks 

facilitates hazard mitigation decision-making. Specifically, the document 

addresses methods for reducing physical damage to structural and nonstructural components of buildings and related infrastructure and 

reducing resultant casualties during conventional bomb attacks, as well as 

attacks involving chemical, biological, and radiological agents. 

FEMA 459 can be used in conjunction with FEMA 452. This manual 

presents an integrated, incremental rehabilitation approach to 

implementing the outcomes of a risk assessment completed in accordance 

with FEMA 452, Risk Assessment: A How-To Guide to Mitigate Potential Terrorist 

Attacks Against Building. This approach is intended to minimize disruption 

to building operations and control costs for existing commercial 

buildings. 

The integrated incremental approach to risk reduction in buildings was 

initially developed in relation to seismic risk and was first articulated in 
ii FOREWORD AND ACKNOWLEDGMENTS

FEMA’s Risk Management Series in the widely disseminated FEMA 395, 

Incremental Seismic Rehabilitation of School Buildings (K–12), published in 

June 2003. In 2004 and 2005, FEMA also published Incremental Seismic 

Rehabilitation manuals (FEMA 396-400) for hospitals, office buildings, 

multifamily apartments, retail buildings, and hotels and motels.

OBJECTIVE AND SCOPE

This manual outlines an approach to incremental security enhancement 

in four types of existing commercial buildings: office buildings, retail 

buildings, multifamily apartment buildings, and hotel and motel 

buildings. It addresses both physical and operational enhancements that 

reduce building vulnerabilities to blasts and chemical, biological, and 

radiological attacks, within the constraints of the existing site conditions 

and building configurations. 

The information contained in this document is:

Not mandatory

Not applicable to all buildings

Not applicable when it interferes with other hazards such as fire

However, the manual presents incremental approaches that can be 

implemented over time to decrease the vulnerability of buildings to 

terrorist threats. Many of the recommendations can be imple­mented 

quickly and cost-effectively. 

LIMITATIONS

This approach to incremental security enhancement applies to 

commercial buildings in urban or semi-urban areas. This approach does 

not apply to exceptionally high-risk iconic buildings of symbolic value. 

Examples of such buildings include the tallest buildings in a city, high 

rise buildings with a distinctive shape recognizable in the city skyline, and 

diplomatic buildings, such as embassies. Security enhancement in this 

class of buildings should be based on detailed engineering analysis and 

design. 

❍

❍

❍
FOREWORD AND ACKNOWLEDGMENTS iii

INTENDED AUDIENCE

This manual addresses the specific needs and practices of commercial 

building owners, and guides building owners and managers through a 

process that will reduce the risks to their buildings from terrorist attacks. 

It is intended for use by both technical and non-technical audiences, 

including: 

Building Owners

Facility Managers

Risk Managers

Security Consultants

Design Professionals

CONTENT AND ORGANIZATION

This manual provides building owners and their design consultants with 

guidance on developing a program of incremental security enhancements 

that can be implemented over a period of time. 

Chapter 1 provides an overview of integrated incremental rehabilitation 

of buildings, potential terrorist threats to buildings, the mitigation of 

the risks of terrorist attacks, special issues related to security in existing 

commercial buildings, a process for integrating incremental mitigation 

into the normal facility management process, and a step-by step 

approach to implementation of an incremental enhancement program. 

It is intended for building owners and their risk managers and facility 

managers.

Chapter 2 describes the relationship between this manual and FEMA 452 

and includes a list of terrorism risk reduction measures. It also discusses 

the implementation of an integrated incremental program and links (in 

the form of matrices) specific physical and operational enhancement 

measures to normal maintenance and capital improvement programs 

associated with commercial buildings. It is intended for risk managers, 

facility managers, and design professionals.

Chapter 3 discusses blast threats to buildings and physical enhancements 

that reduce the vulnerability to blasts. It is intended for design 

professionals and their blast consultants.

❍

❍

❍

❍

❍
iv FOREWORD AND ACKNOWLEDGMENTS

Chapter 4 discusses chemical, biological, and radiological threats to 

buildings and physical and operational enhancements that reduce the 

vulnerability to these threats. It is intended for design professionals and 

their CBR consultants.

Chapter 5 discusses operational security measures that reduce commercial 

building vulnerabilities to terrorist threats. It is intended for design 

professionals and security personnel.

ACKNOWLEDGMENTS

This publication has been developed in collaboration with the 

Infrastructure and Geophysical Division of the Science and Technology 

Directorate of the Department of Homeland Security.

Principal Authors:

Frederick Krimgold, D.Tech., Virginia Tech

David Hattis, Building Technology Incorporated

Robert Smilowitz, Weidlinger Associates, Inc.

William Blewitt, Batelle

Terrence P. Ryan, Raytheon UTD

Contributors:

Pax Williams, Batelle

Expert Review Panel:

Eric Letvin, URS Corporation

Ken Mead, Centers for Disease Control and Prevention 

John Sullivan, Portland Cement Association

Michael J. W. Kaminskas, Raytheon UTD

Mark M. Hankewycz, the Protection Engineering Group, PC

Mohamed Ettouney, Weidlinger Associates, Inc.

Project Officer:

Milagros Nanita Kennett

Infrastructure and Geophysical Division

Science and Technology Directorate

US Department of Homeland Security
Table of contents

Table of Contents

Foreword and Acknowledgments

Background................................................................................................................................i

Objective and Scope .................................................................................................................ii

Limitations ................................................................................................................................ii

Intended Audience..................................................................................................................iii

Content and Organization......................................................................................................iii

Acknowledgments.................................................................................................................... iv

1 Integrated Incremental Building Protection

1.1 What is Integrated Incremental Building Protection ................................................................... 1-1

1.1.1 Integration of Terrorism Risk Reduction in the Facility

Management Process............................................................................................. 1-1

1.1.2 Incremental Approach Distributes Cost Over Time and Avoids Added 

Disruption .............................................................................................................. 1-2

1.1.3 Risk Reduction Decisions...................................................................................... 1-3

1.2 Potential Threats................................................................................................................. 1-4

1.2.1 Explosive Threats................................................................................................... 1-5

1.2.2 CBR Threats........................................................................................................... 1-7

1.2.2.1 Chemical Agents ................................................................................ 1-7

1.2.2.2 Biological Agents ............................................................................... 1-8

1.2.2.3 Radiological Threats........................................................................... 1-8

1.3 Terrorism Risk Reduction....................................................................................................... 1-9

1.3.1 Categories of Risk Reduction Increments ........................................................... 1-9

1.3.2 Implementation Considerations......................................................................... 1-10

1.4 Special Issues Related to Existing Commercial Buildings ........................................................... 1-11
vi Table of contents

1.5 Commercial Building Classifications....................................................................................... 1-12

1.6 Facility Management Process for Existing Commercial Buildings................................................. 1-13

1.6.1 The Acquisition Phase of Commercial Building Facility Management........... 1-14

1.6.2 The Redevelopment Phase of Commercial Building Facility Management ... 1-15

1.6.3 The Current Building Use Phase of Commercial Building Facility 

Management ........................................................................................................ 1-17

1.6.4 The Planning Phase of Commercial Building Facility Management............... 1-19

1.6.5 The Maintenance and Rehabilitation Budgeting Phase of Commercial 

Building Facility Management............................................................................ 1-22

1.6.6 The Maintenance and Rehabilitation Funding Phase of Commercial 

Building Facility Management............................................................................ 1-24

1.6.7 The Maintenance and Rehabilitation Implementation Phase of

Commercial Building Facility Management...................................................... 1-25

1.7 Planning and Managing Incremental Terrorism Risk Reduction ................................................... 1-26

1.7.1 Step 1—Conduct a Due Diligence Terrorism Risk Assessment........................ 1-27

1.7.2 Step 2—Identify and Implement Initial Increment Integration 

Opportunities....................................................................................................... 1-28

1.7.3 Step 3—Assess Terrorism Risk ........................................................................... 1-29

1.7.4 Step 4—Develop a Security Master Plan............................................................ 1-30

1.7.5 Step 5—Plan Incremental Rehabilitation for Specific Buildings..................... 1-31

1.7.6 Step 6—Stage Rehabilitation Increments ......................................................... 1-32

1.7.7 Step 7—Coordinate with Tenant Work.............................................................. 1-33

1.7.8 Step 8—Define Budget Packaging ..................................................................... 1-34

1.7.9 Step 9—Implement Integrated Incremental Rehabilitation Project 

Management ....................................................................................................... 1-35

1.8 Terrorism Risk Assessment to Terrorism Risk Reduction ........................................................... 1-36

2 MOVING FROM RISK assessment TO IMPLEMENTATION

OF INCREMENTAL Building Protection

2.1 Risk Assessment Process ...................................................................................................... 2-1

2.1.1 Levels of Vulnerability Assessment ...................................................................... 2-3
Table of contents vii

2.1.2 The Building Vulnerability Assessment Checklist ............................................... 2-4

2.2 Scheduling Increments: Physical Protection and Strengthening Measures and Operational 

(Protective and Control) Measures ......................................................................................... 2-5

2.2.1 Physical Protection and Strengthening Measures............................................... 2-5

2.2.2 Operational Measures ........................................................................................... 2-5

2.3 Identifying Integration Opportunities for Incremental Building Protection ...................................... 2-6

3 PRINCIPLES OF DESIGN FOR RISK

REDUCTION RELATED TO BLASTS

3.1 Selected Examples of Terrorist Attacks on Buildings................................................................... 3-2

3.1.1 Baltic Exchange, City of London, April 1992 ...................................................... 3-3

3.1.2 World Trade Center, New York City, February 1993............................................ 3-3

3.1.3 Bishopsgate, City of London, April 1993 ............................................................. 3-4

3.1.4 Town Center, Manchester, England, June 1996 .................................................. 3-5

3.2 Performance Standards ........................................................................................................ 3-6

3.3 Site Incremental Upgrades: Perimeter Protection....................................................................... 3-8

3.4 Incremental Building Rehabilitation Measures......................................................................... 3-10

3.4.1 Building Envelope ............................................................................................... 3-10

3.4.2 Fragment Retention Film.................................................................................... 3-12

3.4.3 Laminated Glass................................................................................................... 3-15

3.4.4 Blast Curtains....................................................................................................... 3-16

3.4.5 Glazing Catch Cable/Bar Retrofit...................................................................... 3-18

3.4.6 Energy-Absorbing Catch Cable Systems............................................................. 3-19

3.4.7 Unreinforced Masonry Wall Debris Control ..................................................... 3-19

3.4.8 Other Facade Retrofits........................................................................................ 3-22

3.5 Nonstructural Members ...................................................................................................... 3-22

3.6 Structural Retrofits............................................................................................................ 3-23

3.6.1 Columns ............................................................................................................... 3-24
viii Table of contents

3.6.2 Floor Systems........................................................................................................ 3-25

3.6.3 Load-Bearing Unreinforced Masonry Walls ...................................................... 3-28

3.6.4 Transfer Girders................................................................................................... 3-29

3.7 Blast Protection Measures .................................................................................................. 3-29

3.8 Blast Protection Measure Cost Considerations ........................................................................ 3-31

4 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO 

CHEMICAL, BIOLOGICAL, AND RADIOLOGICAL THREATS

4.1 Overview of CBR Threats...................................................................................................... 4-1

4.2 Principles of Design for Risk Reduction Related to CBR .............................................................. 4-2

4.3 Prioritization of CBR Vulnerabilities: Incremental Improvements.................................................. 4-3

4.3.1 Level 1, Operational Measures and Expedient Protection................................. 4-4

4.3.2 Level 2, Enhanced Physical Security .................................................................... 4-4

4.3.3 Level 3, Enhanced Sheltering in Place................................................................. 4-5

4.3.4 Level 4, Aerosol Filtration, Medium Level........................................................... 4-5

4.3.5 Level 5, Gas-Phase Filtration, Medium Level....................................................... 4-6

4.3.6 Level 6, Aerosol Filtration, High Level ................................................................ 4-6

4.3.7 Level 7, Gas-Phase Filtration, High Level ............................................................ 4-7

4.4 Design Guidance for CBR Protective Levels .............................................................................. 4-7

4.4.1 Level 1, Operational Measures and Expedient Protection................................. 4-7

4.4.1.1 Scope and Capabilities....................................................................... 4-7

4.4.1.2 Methods and Requirements .............................................................. 4-8

4.4.1.3 Cost Considerations.......................................................................... 4-13

4.4.2 Level 2, Physical Security..................................................................................... 4-14

4.4.2.1 Scope and Capabilities..................................................................... 4-14

4.4.2.2 Methods and Requirements ............................................................ 4-14

4.4.2.3 Cost Considerations.......................................................................... 4-17

4.4.3 Level 3, Enhanced Safe Rooms and Isolated Zones.......................................... 4-17

4.4.3.1 Scope and Capabilities..................................................................... 4-17
Table of contents ix

4.4.3.2 Methods............................................................................................. 4-17

4.4.3.3 Cost Considerations.......................................................................... 4-20

4.4.4 Level 4, Aerosol Filtration, Medium Level......................................................... 4-20

4.4.4.1 Scope and Capabilities..................................................................... 4-20

4.4.4.2 Methods and Requirements ............................................................ 4-21

4.4.4.3 Cost Considerations.......................................................................... 4-21

4.4.5 Level 5, Gas-Phase Filtration, Medium Level..................................................... 4-22

4.4.5.1 Scope and Capabilities..................................................................... 4-22

4.4.5.2 Methods and Requirements ............................................................ 4-23

4.4.5.3 Cost Considerations.......................................................................... 4-24

4.4.6 Level 6, Aerosol Filtration, High Level .............................................................. 4-24

4.4.6.1 Scope and Capabilities..................................................................... 4-24

4.4.6.2 Methods and Requirements ............................................................ 4-24

4.4.6.3 Cost Considerations.......................................................................... 4-25

4.4.7 Level 7, Gas-Phase Filtration, High Level .......................................................... 4-25

4.4.7.1 Scope and Capabilities..................................................................... 4-25

4.4.7.2 Methods and Requirements ............................................................ 4-26

4.4.7.3 Cost Considerations.......................................................................... 4-28

4.5 Summary.......................................................................................................................... 4-28

4.6 CBR Protection Measures ................................................................................................... 4-30

5 PRINCIPLES OF DESIGN FOR RISK REDUCTION

RELATED TO OPERATIONAL SECURITY MEASURES

5.1 Overview of Operational Security Measures ............................................................................ 5-1

5.2 Detection and Assessment Measures ...................................................................................... 5-2

5.2.1 Exterior Intrusion Detection Systems .................................................................. 5-2

5.2.2 Interior Intrusion Detection Systems................................................................... 5-3

5.2.3 Video Assessment and Surveillance Systems........................................................ 5-3

5.2.4 Access Control Systems.......................................................................................... 5-5
Table of contents

5.2.5 Vehicle Inspection Systems ................................................................................... 5-6

5.2.6 Duress Alarms ........................................................................................................ 5-7

5.2.7 Mail/Package Screening ....................................................................................... 5-7

5.3 Interdiction/Response Measures............................................................................................ 5-9

5.3.1 Guard Force – Detection/Delay Role .................................................................. 5-9

5.3.2 Guard Force – Response/Interdiction Role...................................................... 5-10

5.3.3 Response Force Contingency Planning ............................................................. 5-10

5.4 Procedural Measures.......................................................................................................... 5-11

5.4.1 Restricted Areas ................................................................................................... 5-11

5.4.2 Parking and Traffic Controls............................................................................... 5-12

5.4.3 Restrict Access to Facility Information............................................................... 5-13

5.4.4 Encourage Employee Support............................................................................ 5-13

5.5 Preparedness Measures...................................................................................................... 5-13

5.5.1 Develop a Disaster Preparedness Plan ............................................................... 5-14

5.5.2 Conduct Risk Assessments................................................................................... 5-14

5.5.3 Develop Mass Notification Systems .................................................................... 5-14

5.5.4 Evacuation Planning and Shelter In Place Preparation ................................... 5-14

5.5.5 Monitor Emergency Systems and Resources ..................................................... 5-15

5.5.6 Conduct Training Drills and Exercises .............................................................. 5-15

5.6 Security Master Planning .................................................................................................... 5-16

5.7 Additional Aspects of Operational Security Measures Related to Blast Events.............................. 5-17

5.7.1 Establish an Explosive Detection Program ........................................................ 5-18

5.7.2 Establish Bomb Threat Procedures.................................................................... 5-18

5.7.3 Establish Blast-Related Mail/Package Handling Procedures........................... 5-18

5.8 Additional Aspects of Operational Security Measures Related to CBR Events .............................. 5-19

5.8.1 Prevent Access, and Secure and Monitor Outdoor Air Intakes ....................... 5-21

5.8.2 Establish CBR-Related Mail/Package Handling Procedures ........................... 5-21

5.8.3 Additional Measures............................................................................................ 5-22
Table of contents xi

5.9 Prioritization of Operational Security Considerations .............................................................. 5-23

5.9.1 Retail Buildings.................................................................................................... 5-24

5.9.2 Office Buildings................................................................................................... 5-24

5.9.3 Multi-Family Apartment Buildings..................................................................... 5-24

5.9.4 Hotel Security Measures...................................................................................... 5-25

5.10 Incremental Integration of Operational and Physical Security Measures Into a

Risk Reduction Program: Flexibility and Tradeoffs................................................................... 5-25

5.11 Operational Security Protection Measures ............................................................................. 5-27

5.11.1 Physical Protection and Strengthening Buildings............................................. 5-27

5.11.2 Operational Measures ......................................................................................... 5-28

5.11.3 Operational Measures Categorized into the Building Vulnerability

Assessment Checklist ........................................................................................... 5-30

Bibliography.......................................................................................................................I

Integrated INCREMENTAL Building Protection 1-1

Integrated Incremental Building Protection 1

1.1 What is Integrated Incremental

Building Protection

I

ntegrated incremental building protection is a 

process for improving safety in existing buildings 

with minimum cost and disruption of building 

function. Integrated, incremental protection of 

existing commercial buildings from terrorist attacks 

applies the basic principles of security evaluation and 

design to the physical and operational demands of 

existing buildings. Rehabilitation of existing buildings 

poses special challenges not faced in the case of design 

and construction of new buildings. Site conditions 

are pre-defined. Configuration and structural system 

are given, and current building occupants must 

be accommodated during the rehabilitation process. Investments in 

rehabilitation of existing buildings may also not be justified in light of the 

expected remaining useful life of the building. 

1.1.1 Integration of Terrorism

Risk Reduction in the Facility

Management Process

The integrated, incremental protection process is based on the 

identification of increments of security enhancement that may be 

integrated into the normal schedule of maintenance and capital 

improvement. For example, when window replacement is considered 

for energy conservation or modernization, blast resistance can be 

enhanced at the same time with relatively little added expense. The 

advantage of this approach to rehabilitation is that it reduces the cost 

of implementing security enhancements and it reduces the cost due to 

added business interruption related to a single purpose intervention 

in the building. The integration of terrorism risk reduction measures 

with normal maintenance and capital improvement takes advantage 

of regularly scheduled design, contracting, and staging to implement 

security enhancements at marginal added cost. The identification of 

specific increments of security enhancement allows these improvements 

The term “building protection” or 

“protection,” as used in this chapter, 

refers to a specific category of 

building “rehabilitation” that 

addresses terrorism risk reduction. 

When the term “rehabilitation” is 

used it refers to general activities 

that may or may not include 

terrorism risk reduction.
1-2 Integrated INCREMENTAL Building Protection

to be made opportunistically as normal work is 

carried out on various components of the building. 

Integration of specific increments of terrorism risk 

reduction is illustrated in the three buildings of 

Figure 1-1. These examples show the opportunistic 

character of the incremental approach. By preidentifying the increments of risk reduction, 

implementation can effectively “piggy-back” on 

work that arises in the normal course of building 

maintenance and capital improvement. For 

example, roofs are usually replaced on a schedule 

of 15 to 20 years. Strengthening the roof/wall 

connections and improving the blast resistance of 

the structure is relatively easy and inexpensive to do 

during a scheduled roof replacement. Provisions 

for opening up the roof and erecting scaffolding 

can serve both the purposes of roof renewal and 

terrorism risk reduction. 

In a similar way, exterior wall maintenance and 

window replacement provide the opportunity for 

reducing outdoor air penetration into the building 

and improving the blast resistance of the windows. 

Work on interior walls provides the opportunity for 

strengthening of blast resistance and the creation of 

safe areas. 

1.1.2 Incremental Approach Distributes 

Cost Over Time and Avoids Added

Disruption

Over time, the accumulated effect of the incremental measures will 

be the same as a comprehensive one-stage building rehabilitation that 

would require closing the building and a major one-time investment. The 

incremental approach spreads the cost of security enhancement over a 

period of years, reducing the impact of rehabilitation costs.

Because the integrated incremental rehabilitation approach is designed 

to accommodate business continuity and a continued revenue stream 

from the commercial building, it is closely tied to the schedules and 

requirements of specific occupancies. 

Figure 1-1: Schematic 

integration 

opportunities.
Integrated INCREMENTAL Building Protection 1-3

Figure 1-2: Cost 

decision scheme.

Investment in the rehabilitation of existing commercial buildings requires 

a strong business case. Sustainable costs must be justified and supported 

by future revenue generated by the building. Factors to consider in 

the justification of rehabilitation investment include: estimation of the 

remaining lifetime of the building, desirability for potential occupants, 

and the market value of security enhancements. 

1.1.3 Risk Reduction Decisions

This manual is designed primarily for application in existing office, 

retail, multi-family residential, and hotel buildings. Owners of existing 

commercial buildings face a sequenced set of cost decisions diagrammed 

in Figure 1-2. On the basis of risk assessment methodologies, building 

owners can evaluate the terrorism risk for specific buildings. Based on the 

informed risk perception, the building owner may decide that building 

protection is not necessary. Alternatively, the building owner may decide 

to invest in terrorism risk reduction measures. If the decision is made 

to invest in terrorism risk reduction, the next decision is whether to 

replace the building, i.e., demolish or sell it and build a new one, or to 

rehabilitate the building to reduce terrorism risk. 

Owners who decide to rehabilitate the building may initiate a singlestage intervention. Such an approach typically requires the evacuation 

of the building for a significant period of time and a major one-time 
1-4 Integrated INCREMENTAL Building Protection

rehabilitation investment. Both these factors may be difficult to accept 

in the case of an existing commercial building with limited remaining 

asset life. An alternative approach is the incremental rehabilitation of the 

building. 

The integrated incremental building protection approach has the 

advantage of reduced and distributed costs. While extending the time of 

implementation, an integrated incremental building protection program 

will eventually provide the same level of protection that can be supported 

by the revenue of an existing commercial building.

Careful planning and efficient use of opportunities for low cost risk 

reduction can make terrorism risk reduction feasible even for marginal 

existing commercial buildings.

1.2 Potential Threats

Commercial building owners who want to implement measures 

that may save lives and property must understand the nature of 

the hazards that can affect their buildings and the impacts of 

those hazards on the buildings. The term “threat” is typically used to 

characterize manmade disasters (technological accidents) or terrorism 

hazards. Because there have been few terrorist attacks in the United States 

and data for manmade threats is scarce, predictions of the magnitude and 

recurrence of terrorist attacks are largely subjective.

Aggressor tactics may include: moving vehicle bombs, stationary vehicle 

bombs, bombs delivered by persons (suicide bombers), exterior attacks 

(thrown objects like rocks, Molotov cocktails, hand grenades, or handplaced bombs), stand-off weapons attacks (rocket-propelled grenades, 

light antitank weapons, etc.), ballistic attacks (small arms and high-power 

rifles), covert entries (gaining entry by false credentials or circumventing 

security with or without weapons), mail bombs (delivered to individuals), 

supply bombs (larger bombs processed through shipping departments), 

airborne contamination (chemical, biological, and radiological [CBR] 

agents used to contaminate the air supply of a building), and waterborne 

contamination (CBR agents injected into the water supply). This section 

focuses on explosive threats, chemical agents, biological warfare agents, 

and radiological attacks. 
Integrated INCREMENTAL Building Protection 1-5

1.2.1 Explosive Threats

The explosive threat is particularly significant, because all of the 

ingredients required to assemble an improvised explosive device are 

readily available at a variety of farm and hardware stores. The intensity of 

the explosive detonation is a function of the weight of the explosive. For 

explosive threats, the weight of the explosive depends on the means of 

transportation and delivery. 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 U.S. Department of Defense (DoD) developed a chart 

indicating the weight of explosives and deflagrating materials that may 

reasonably fit within a variety of containers and vehicles (see Table 1-1). 

The table indicates the safe evacuation distances for occupants of 

conventional buildings, based on the ability of the buildings to withstand 

severe damage or resist collapse. 

Operational security measures (see Chapter 5) define the areas within 

or around a building at which a device may be located, undetected by 

the building facility staff. These security procedures include screening of 

vehicles, inspection of delivered parcels, and vetting hand carried bags. 

The extent to which this inspection is carried out will determine the 

size of an explosive device that may evade detection. Despite the most 

vigilant attempts, however, it is unrealistic to expect complete success in 

preventing a small explosive threat from evading detection. While it is 

unlikely that a large explosive threat may be brought into a building, a 

parcel sized device may be introduced into publicly accessible lobbies, 

garages, loading docks, cafeterias, or retail spaces and a smaller explosive 

device may be brought anywhere into a building. 

Only two domestic terrorist bombings involved the use of large quantities 

of High Energy explosive materials in the United States. (For more 

information on High Energy explosives, see FEMA 426, Reference Manual 

to Mitigate Potential Terrorist Attacks Against Buildings, Chapter 4.) Although 

these events represent the largest explosions that have occurred to date, 

they may not represent the current domestic explosive threat. The 1995 

explosion that collapsed portions of the Murrah Federal Office Building 

in Oklahoma City contained 4,800 pounds of ammonium nitrate and fuel 

oil (ANFO) and the 1993 explosion within the parking garage beneath 

the World Trade Center complex contained 1,200 pounds of urea nitrate.

Every year, approximately 1,000 intentional explosive detonations are 

reported by the Federal Bureau of Investigation (FBI) Bomb Data 

Center. The FBI statistics indicate that the majority of the domestic events 

contain significantly smaller weights of Low Energy explosives. (For more 

information on Low Energy explosives, see FEMA 426, Chapter 4.) 
1-6 Integrated INCREMENTAL Building Protection

Table 1-1: Safe Evacuation Distances from Explosive Threats
Integrated INCREMENTAL Building Protection 1-7

Although the majority of the explosions reported by the FBI targeted 

residential properties and vehicles, 63 took place in educational facilities, 

causing a total of $68,500 in property damage. Other than the attack 

against the Murrah Federal Office Building, no explosive devices were 

detonated at a Federal government-owned facility, and only nine were 

detonated at local/state government facilities. Nearly 80 percent of the 

people known to be involved in bombing incidents were young offenders, 

and less than 0.5 percent of the perpetrators were identified as members 

of terrorist groups. Vandalism was the motivation in 53 percent of the 

known intentional and accidental bombing incidents, and the timing of 

the attacks was fairly uniformly distributed throughout the day. 

1.2.2 CBR Threats

Like explosive threats, CBR threats may be delivered externally or 

internally to a building. While there may not be official warning of a CBR 

event, the best defense may be to be alert to signs of a release. 

There are three potential methods of CBR attack: 

A large exterior release originating some distance away from the 

building (includes delivery by aircraft)

A small localized exterior release at an air intake or other opening in 

the exterior envelope of the building 

A small interior release in a publicly accessible area, a major egress 

route, or other vulnerable area (e.g., elevator lobby, mail room, 

delivery, receiving and shipping) 

The following paragraphs provide summary information about each of 

the components of CBR attacks—chemical agents, biological agents, and 

radiological threats. 

1.2.2.1 Chemical Agents 

Toxic chemical agents can present airborne hazards when dispersed as 

gases, vapors, or solid or liquid aerosols. Unlike biological or radiological 

agents, chemical agents generally produce immediate effects. In most 

cases, toxic chemical agents can be detected by the senses, although a few 

are odorless. Their effects occur mainly through inhalation, although they 

can also cause injury to the eyes and skin. 

❍

❍

❍
1-8 Integrated INCREMENTAL Building Protection

1.2.2.2 Biological Agents 

Biological agents are organisms or toxins that can kill or incapacitate 

people and livestock, and destroy crops. The three basic groups of 

biological agents that would likely be used as weapons are bacteria, 

viruses, and toxins.

Bacteria. Bacteria are small free-living organisms that reproduce by 

simple division and are easy to grow. The diseases they produce often 

respond to treatment with antibiotics.

Viruses. Viruses are organisms that require living cells in which to 

reproduce and are intimately dependent upon the body they infect. 

The diseases they produce generally do not respond to antibiotics; 

however, antiviral drugs are sometimes effective.

Toxins. Toxins are poisonous substances found in, and extracted 

from, living plants, animals, or microorganisms; some toxins can be 

produced or altered by chemical means. Some toxins can be treated 

with specific antitoxins and selected drugs. 

Most biological agents are difficult to grow and maintain. Many break 

down quickly when exposed to sunlight and other environmental factors, 

while others such as anthrax spores are very long lived. There are three 

methods for delivery of biological agents:

Aerosols. Biological agents are dispersed into the air, forming a fine 

mist that may drift for miles. Inhaling the agent may cause disease in 

people or animals.

Animals. Some diseases are spread by insects and animals, such as fleas, 

flies, mosquitoes, and mice. Deliberately spreading diseases through 

livestock is also referred to as agroterrorism. Person-to-person spread 

of a few infectious agents is also possible. Humans have been the 

source of infection for smallpox, plague, and the Lassa viruses.

Food and water contamination. Some pathogenic organisms and toxins may 

persist in food and water supplies. Most microbes can be killed, and 

toxins deactivated, by cooking food and boiling water. 

1.2.2.3 Radiological Threats

This manual does not address the severe and various effects generated by 

nuclear events, including blinding light, intense heat (thermal radiation), 

❍

❍

❍

❍

❍

❍
Integrated INCREMENTAL Building Protection 1-9

initial nuclear radiation, blasts, fires started by the heat pulse, and 

secondary fires caused by the destruction. 

Terrorist use of a radiological dispersion device (RDD), often called “dirty 

bomb,” is considered more likely than use of a nuclear device. These 

radiological weapons are a combination of conventional explosives and 

radioactive material designed to scatter dangerous and sublethal amounts 

of radioactive material over a general area. Very little technical knowledge 

is required to build and deploy such radiological weapons as compared 

to that of a nuclear device. Also, radioactive materials, used widely in 

medicine, agriculture, industry, and research, are more readily available 

and easy to obtain compared to the weapons-grade uranium or plutonium 

required for a nuclear device. 

1.3 Terrorism Risk Reduction

1.3.1 Categories of Risk Reduction 

Increments

T he adoption of risk reduction increments as part of enhancing, 

retrofitting, or rehabilitating a building can be an effective 

approach in reducing vulnerability to terrorist attacks. There is a 

range of risk reduction increments that can be used to enhance security 

in case of blasts and chemical, biological, and radiological hazards. For 

this manual, two categories are identified:

Physical Protection and Strengthening of Existing Buildings. Physical protection 

and strengthening deals with structural and non-structural 

modifications of existing buildings. While new buildings may include 

protective measures to reduce the potential impact of terrorist 

attacks, existing buildings may be at larger risk because they were 

constructed without the appropriate safety measures to withstand 

potential attacks. Thus, improving the safety and structural integrity 

of existing buildings is often the best way to reduce the impact of 

terrorist attacks on such structures. When a terrorism threat occurs, 

it can directly damage a target building or indirectly cause secondary 

effects in adjacent buildings (collateral damage). Poorly engineered 

and constructed buildings cannot usually resist the forces generated 

by a blast event or serve as safe havens in case of CBR attacks. 

Operational Measures. Unlike other risk reduction increments that 

improve the resistance of buildings to disasters, protective and control 

measures focus on protecting structures by deflecting the destructive 

forces from vulnerable structures and people. Ideally, a potential 

terrorist attack is prevented or pre-empted through intelligence 

❍

❍
1-10 Integrated INCREMENTAL Building Protection

measures. If the attack does occur, physical security measures combine 

with operational forces (e.g., surveillance, guards, and sensors) 

to provide layers of defense that can delay or thwart the attack. 

Deception may be used to make a facility appear to be more protected 

or lower risk than it actually is, making it a less attractive target. 

Deception can also be used to misdirect an attacker to a portion 

of the facility that is non-critical. Because of the interrelationship 

between physical and operational security measures, it is imperative 

for building owners and security professionals to define what extent of 

operational security is planned for various threat levels. 

1.3.2 Implementation Considerations

The implementation of some risk reduction increments may create 

public inconvenience. For example, the placement of bollards, closure 

of public streets, and rehabilitation of buildings may affect people’s 

access to public places or have a negative effect on community aesthetic. 

The implementation of mitigation enhancements involves the following 

considerations. 

Costs and Benefits. When implementing a risk reduction increment, 

the benefits (reduction of potential future losses) of implementing 

the option should outweigh the costs (capital cost of protection 

measure, operating cost of protection measure, and adverse effects on 

business). 

Legal Authority. A risk reduction increment should not be undertaken 

without the appropriate legal authority. Building owners should 

determine whether they have the legal authority to implement 

selected mitigation options. For example, creating standoff distances 

in urban areas can violate zoning ordinances and building set-back 

requirements. 

Adverse Effects on the Built Environment. Some risk reduction increments 

may have a negative effect on the built environment. When selecting 

mitigation measures, building owners should scrutinize the potential 

effects on:

Traffic/vehicular mobility

Pedestrian mobility

Ingress and egress to the building

Other building operations

Aesthetics

❍

❍

❍

❍

❍

❍

❍

❍
Integrated INCREMENTAL Building Protection 1-11

Interference with first responders 

Impact on the Natural Environment. Considering whether the recommended 

risk reduction increments will have a negative effect on environmental 

assets, such as air quality, water quality, threatened and endangered 

species, and other protected natural resources is also important. 

1.4 Special Issues Related to

Existing Commercial Buildings

Certain features of existing buildings clearly distinguish them from 

newly designed and constructed buildings and may limit the range 

of security mitigation options available for consideration: 

The physical fabric of the existing building may be concealed or 

unknown. New buildings are designed and specified in terms of 

materials and systems whose characteristics are fully defined and that 

conform to known standards. By contrast, the design basis, materials, 

and standards that governed the design and construction of currently 

existing buildings are more ambiguous. Determining the inherent 

response of the building and its systems to blast forces, for example, 

may not be possible. 

Existing buildings are likely to have been designed to conform to 

older, and possibly archaic, building codes. Their performance under 

current physical conditions may be difficult to determine or control. 

The relationship of existing buildings to the surrounding site, roads, 

access, standoff, utilities, and adjacent buildings is fixed and not 

subject to significant alteration.

The physical fabric of an existing building may constrain or prohibit 

the implementation of specific risk reduction measures that are 

considered in new building design as a matter of course.

Existing buildings are usually occupied and perform a variety of 

business, cultural, and life support functions for their occupants. 

This may constrain or prohibit the implementation of specific 

risk reduction measures unless business or service interruption is 

acceptable.

Compared to new buildings, existing buildings often have a limited 

useful remaining lifetime, which dictates a much shorter payback 

period for investments in security enhancement. 

❍

❍

❍

❍

❍

❍

❍

❍
1-12 Integrated INCREMENTAL Building Protection

Conditions of financing capital improvements in existing buildings 

may differ from those applicable to new buildings.

The commercial buildings addressed in this manual are office buildings, 

retail buildings, multifamily apartment buildings, and hotel buildings. 

All four categories have features that may limit the range of security 

mitigation options available for consideration: 

Commercial buildings are income-generating systems for their 

owners. Interruption of building operations interrupts the flow of 

income and is equivalent to an added cost when considering any 

capital improvement. This feature makes commercial buildings ideal 

candidates for integrated incremental enhancements, which better 

manage costs and disruption. 

Access control is a significant aspect of security enhancement for 

buildings. Commercial office, retail, hotel, and multifamily apartment 

buildings require public access. The extent to which that access can be 

controlled may be limited. 

1.5 Commercial Building 

Classifications

Commercial buildings are often classified for real estate purposes 

into three classifications—Classes A, B, and C. The Urban 

Land Institute, a noted authority on commercial land uses, 

says the following about these classifications in its Office Development 

Handbook. Class A space can be characterized as buildings that have 

excellent location and access, attract high quality tenants, and are 

managed professionally. Building materials are high quality and rents are 

competitive with new buildings. Class B buildings have good locations, 

management, and construction, and tenant standards are high. Buildings 

should have very little functional obsolescence and deterioration. Class 

C buildings are typically 15 to 25 years old but are maintaining steady 

occupancy. Tenants filter from Class B to Class A and from Class C to Class 

B. In a normal market, Class A rents are higher than Class B, which are 

above Class C. 

Facility management practices in commercial buildings vary as a function 

of this classification (Class A, B, or C) as well as the type and scale 

of ownership. The effectiveness of physical and operational security 

enhancements depends on the quality of the facility management.

❍

❍

❍
Integrated INCREMENTAL Building Protection 1-13

1.6 Facility Management Process 

for Existing Commercial

Buildings

Facility management processes for existing commercial buildings 

vary in detail by type of occupancy (office, retail, multifamily, 

hotels, etc.). The complexity and completeness of facility 

management practices may also vary by type of ownership (real estate 

investment trust [REIT], pension fund, insurance company, partnership, 

individual, etc.) and by scale of operation (dispersed portfolio, 

concentrated portfolio, individual building). Despite these variations, a 

generic facility management process consists of seven phases of activities: 

1. Acquisition 

2. Redevelopment 

3. Current Building Use 

4. Planning 

5. Maintenance and Rehabilitation Budgeting 

6. Maintenance and Rehabilitation Funding

7. Maintenance and Rehabilitation Implementation 

Figure 1-3 depicts these seven distinctive phases in the overall facility 

management process and the activities associated with each phase, 

which are discussed in detail in the following sections. The facility 

Figure 1-3: Typical facility management process.
1-14 Integrated INCREMENTAL Building Protection

management process is sequential, progressing from acquisition through 

implementation of rehabilitation in any given building. It begins with 

acquisition because commercial buildings normally change ownership 

every seven to 15 years, and this usually entails new financing and 

insurance, providing a unique opportunity for facility assessment and 

initial redevelopment. A current owner of an existing commercial 

building, as opposed to a prospective owner, begins the facility 

management process with the third phase, the use phase. An owner who 

has a large inventory of buildings is likely to have ongoing activities in all 

of these phases in different buildings.

This process is generic, and while there may be variations, commercial 

building owners generally follow it, either explicitly or implicitly. 

The following sections briefly describe each phase, the activities therein, 

and some factors that influence those activities (indicated graphically by 

downward arrows for factors outside the owner organization and upward 

arrows for factors internal to the organization). 

1.6.1 The Acquisition Phase of Commercial

Building Facility Management

The acquisition phase of the typical commercial building facility 

management process consists of due diligence activities and is influenced 

by significant internal and external pressures, as depicted in Figure 1-4.

Figure 1-4: Acquisition phase.
Integrated INCREMENTAL Building Protection 1-15

Commercial building acquisitions initiate the facility management process 

for all owners who are not also developers or merchant builders. The due 

diligence process that precedes an acquisition is intended to identify, and 

quantify if possible, all the liabilities and risks or potential liabilities and 

risks related to the asset being acquired.

Acquisition phase decisions are influenced by three factors: 

Market Conditions. External local conditions of the commercial rental 

market are the principal factors governing commercial building 

acquisition, regardless of the short-term or long-term strategic 

objectives of the purchaser. This is true for all types of owners, be they 

REITs, pension funds or other fiduciary institutions, partnerships, or 

individuals. 

Lenders and Insurers. Lenders and insurers are important external 

participants in many commercial building acquisitions, and each 

carry out due diligence functions to determine the risks and potential 

liabilities in any given deal. By their nature, lenders and insurers 

spread their risks over a wider range of investments than that 

presented to an owner in a specific acquisition. The insurability of the 

acquired property is of great concern to commercial building owners, 

but the cost of insurance is of lesser concern because the cost may be 

passed on to tenants in many commercial properties. 

Risk Management. Many commercial building owners have formally 

established internal risk management functions within their 

organizations. These risk managers participate in the due diligence 

analyses carried out prior to acquisition. The rigor of internal due 

diligence varies from owner to owner.

1.6.2 The Redevelopment Phase of

Commercial Building Facility

Management

The redevelopment phase of the typical commercial building facility 

management process consists of various types of capital improvements, 

and is influenced by significant internal and external pressures, as 

depicted in Figure 1-5.

❍

❍

❍
1-16 Integrated INCREMENTAL Building Protection

The types of redevelopment phase capital improvement projects vary 

as a function of the building’s classification (A, B, or C). They generally 

consist of:

Architectural upgrading of entrances, lobbies, and public areas

Architectural upgrading of facades

Upgrading of the heating, ventilation, and air-conditioning (HVAC) 

systems

Environmental and other risk remediation work identified in the due 

diligence process

Upgrading of life safety systems 

Redevelopment phase decisions are influenced by three factors: 

Market Conditions. Commercial properties in a given classification must 

compete with neighboring, similarly classified properties. Local 

architectural traditions and fashions and historic preservation are 

significant factors determining the specific nature of various capital 

improvement projects.

Lenders and Insurers. External lenders and insurers may require specific 

capital improvements as a condition of the deal. For example, they 

may require the replacement of a questionable roof or HVAC system. 

These are generally the direct result of the due diligence analyses.

❍

❍

❍

❍

❍

❍

❍

Figure 1-5: Redevelopment phase.
Integrated INCREMENTAL Building Protection 1-17

Owner Policies. Owners’ marketing and architectural policies are the 

principal internal factors governing capital improvement decisions in 

the redevelopment phase.

1.6.3 The Current Building Use Phase 

of Commercial Building Facility

Management

The current building use phase of the typical commercial facility 

management process consists of four categories of activities and is 

influenced by significant internal and external pressures, as depicted in 

Figure 1-6.

Occupancy. The primary function of this category is occupancy of 

commercial space by tenants. Support functions are administrative, 

such as collecting rents and addressing tenants’ concerns. Ancillary 

functions may be recreational, such as operating a health club, pool, 

or spa, and social, such as operating a lecture room, restaurant, or 

similar facility. The specific functions may vary depending on the 

building classification (A, B, or C).

Occupancy functions are carried out in each building by the tenants 

and facility managers. Each of these functions is subject to security risk 

and can be disrupted by terrorist attacks.

❍

❍

Figure 1-6: Use phase.
1-18 Integrated INCREMENTAL Building Protection

Operation. Facility operation consists of all the activities and functions 

that are required to support the occupancy. Examples of facility 

operation include mechanical functions (heating, cooling, and 

ventilation), electrical functions (lighting, communications, and 

alarm), and plumbing functions. 

Operation functions may be carried out by custodial staff of the owner 

and/or by contractors. Each of these functions is subject to security 

risk and can be disrupted by terrorist attacks.

Maintenance. Maintenance includes all the activities required to 

enable the occupancy and operation of the building continuously 

over time. They can be broken down into custodial maintenance, 

routine maintenance, and repair. 

Maintenance functions may be carried out by custodial staff of 

the owner and/or by contractors. In some cases, tenants or their 

contractors may carry out some maintenance functions. 

Scheduled Facility Assessment. Facility assessment, which less 

sophisticated commercial building owners may not carry out 

systematically, consists of the survey or inspection of the buildings 

on a scheduled basis. It may also include a review of documents, 

such as archival building plans, for retrieving specific information. 

The purpose(s) of the surveys or inspections is to determine facility 

conditions in relation to one or more of the following categories:

❍ Specific environmental hazards ❍ Preventive maintenance needs

❍ Asbestos ❍ Structural hazards

❍ Lead paint ❍ Fire/life safety

❍ Lead ❍ Environmental quality

❍ Radon ❍ Energy use/conservation 

❍ User complaints ❍ Accessibility

❍ Maintenance needs ❍ Other

These surveys may or may not be coordinated by schedule, content, 

personnel, etc. Facility managers may or may not use prepared 

inspection forms or checklists. Finally, the extent and specific nature of 

recordkeeping and reporting by facility managers may vary. 

Current use phase decisions are influenced by two factors: 

Federal and State Programs. Various external programs may establish 

requirements affecting the use of commercial buildings that have 

facilities implications (e.g., Americans with Disabilities Act [ADA] 

❍

❍

❍

❍
Integrated INCREMENTAL Building Protection 1-19

and Occupational Safety and Health Administration [OSHA] 

requirements). 

Specific surveys or inspections may be mandated by State or local 

laws/programs. These surveys/inspections may be carried out by a 

variety of entities:

Federal personnel (e.g., from OSHA or the Environmental 

Protection Agency)

State/city/county personnel (e.g., fire marshal, code 

enforcement, environmental, health)

Commercial building personnel (e.g., custodial or facility 

managers)

Commercial building contracted personnel (e.g., asbestos 

inspectors)

Consultants 

Complaints by Occupants. Complaints by tenants are a potentially 

significant internal pressure on the facility management process.

1.6.4 The Planning Phase of Commercial

Building Facility Management

The planning phase consists of projecting and forecasting future needs. 

It can be carried out periodically or continuously, and the time period 

covered by the projections and forecasts may vary. The owner, with or 

without the assistance of consultants, may carry out planning functions. 

Planning consists of two separate but related activities—strategic planning 

and facility planning—and is affected by significant internal and external 

pressures, as depicted in Figure 1-7. 

Strategic Planning. Strategic planning attempts to formulate future 

business strategy by analyzing and forecasting financial trends as well as 

national, regional, and local commercial space markets. Many owners 

acquire properties for a limited period of time, and many have an exit 

strategy in place at the time of acquisition. Strategic planning addresses 

such issues as:

Should the property classification (A, B, or C) be upgraded or 

downgraded?

Should the exit strategy be accelerated or prolonged?

❍

❍

❍

❍

❍

❍

❍

❍
1-20 Integrated INCREMENTAL Building Protection

Should trends in the insurance market revise current investment 

programs?

Should specific major capital investments be considered?

Strategic planning is usually carried out at the owner’s headquarters 

and addresses the owner’s entire commercial building portfolio or large 

segments of it. 

Facility Planning. Facility planning consists of preparing short- and longrange facility plans. It combines the products of two distinct activities—the 

strategic plan and the facility assessment (see Figure 1-6)—into a detailed 

projection of facility requirements. The projection may cover a defined 

time frame, such as 5 years.

Different owners may use different classifications of projects in their 

facility plans, reflecting a variety of legal, administrative, jurisdictional, 

and other factors. However they may be classified, a comprehensive 

facility plan should include the following elements:

New construction

Additions to existing buildings

Renovations of existing buildings

❍

❍

❍

❍

❍

Figure 1-7: Planning phase.
Integrated INCREMENTAL Building Protection 1-21

Building systems replacements

Building systems repairs

Scheduled maintenance

Preventive maintenance

Building disposition (change of use, sale, demolition)

The plan identifies the time frames for accomplishing each project, and it 

may include cost estimates. 

If effective, the facility plan is used as a budgeting tool and provides direct 

inputs into the budget process. It should be revised and updated on a 

routine basis to reflect:

Changes in the strategic plan (including market conditions)

Revised facility assessments

Budgeting and funding realities 

Facility planning usually begins at the individual building or project level 

and entails the flow of information up the management hierarchy for 

final capital decision-making and budgeting at the owner’s headquarters 

in the case of large portfolios. 

Planning phase decisions are influenced by three factors: 

Government Mandates. Federal, State, and local government agencies 

may establish external requirements affecting facility planning in the 

planning phase. These requirements may have facility rehabilitation 

implications. 

Insurance Carriers and Brokers. External private property and 

casualty insurance companies often require surveys or inspections 

of commercial buildings on an annual or other scheduled basis. 

Insurance carriers are more than willing, when asked, to provide 

building owners with Loss Control and Prevention Reports that 

include recommendations for loss prevention. Insurance brokers also 

employ loss/risk specialists. 

Board Policies. In terms of internal influences, boards of directors may 

occasionally adopt written policies on issues of business and social 

significance that can affect both strategic and facility planning. These 

policies guide the actions of the owner organization.

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
1-22 Integrated INCREMENTAL Building Protection

1.6.5 The Maintenance and Rehabilitation 

Budgeting Phase of Commercial

Building Facility Management

The budgeting phase consists of the projection of future financial 

resources required to meet future needs. It is carried out annually 

(covering a period of 1 or more years). Each local or regional facility 

manager initiates it with input from his or her staff. In the case of 

large portfolio owners, the facility budget process is initiated locally or 

regionally, and is overseen centrally. The facility budgeting is a process 

that can be thought of as percolating up through the organization. 

It is affected by external government fiscal regulations and lender 

requirements, and internal risk management policies and budget 

constraints, as depicted in Figure 1-8.

Three elements of the budget are relevant to the discussion of facility 

management:

Capital

Maintenance

Insurance 

❍

❍

❍

Figure 1-8: Budgeting phase.
Integrated INCREMENTAL Building Protection 1-23

Capital Budgets. Capital generally relates to the acquisition of 

buildings and major systems, which is not annual or repetitive, and 

which can therefore be amortized. The distinction between capital 

and maintenance budgets may vary among different commercial 

building owners. At one extreme is a total separation, mandated 

by law, labor jurisdiction, or other factor. At the other extreme is a 

rather unclear separation between the two funding mechanisms. 

Maintenance Budgets. Maintenance budgets generally relate to 

recurring annual expenditures and address existing inventories of 

buildings and systems without adding to the inventories. 

Insurance Budgets. Financial resources earmarked for insurance may 

be used in different ways, including the purchase of third-party 

insurance and/or the funding of a self-insurance reserve. Property 

and general liability insurance are relevant to facility management 

considerations.

Budgeting phase decisions are influenced by four factors: 

Government Fiscal Regulations. Federal, State, and local government 

agencies have historically established external requirements dealing 

with fiscal responsibility of commercial property owners. A variety 

of Security and Exchange Commission regulations apply to REITs. 

Pension funds are subject to a variety of fiduciary requirements. 

Partnerships are subject to a variety of State and Federal regulations. 

One important objective of these regulations is to ensure the 

responsible stewardship of third party resources. These requirements 

may have facility rehabilitation implications, if resources are 

expended in an irresponsible manner. Additionally, these regulations 

may determine, directly or indirectly, the length of time an acquired 

real estate asset must be held and, therefore, what the owner’s 

planning horizon should be. 

Lender Requirements. Commercial lenders impose requirements 

on building owners who use mortgage financing for capital 

improvements. Often, the lender requires the purchase of a 

particular type of insurance coverage.

Budgetary Constraints. Internally, political and economic conditions 

may place limits on commercial building capital and maintenance 

budgets. The problem is often exacerbated by unfunded mandates 

imposed on commercial buildings by Federal and State agencies. 

❍

❍

❍

❍

❍

❍
1-24 Integrated INCREMENTAL Building Protection

Risk and Insurance Management. Internally, the owner organization’s 

risk and insurance management may directly or indirectly affect 

insurance decisions in the budgeting phase of the process. 

1.6.6 The Maintenance and Rehabilitation 

Funding Phase of Commercial

Building Facility Management

The funding phase consists of those activities required to obtain the 

financial resources to meet the budgets. It is influenced externally by 

regional and local economic conditions and bond financing regulations, 

as depicted in Figure 1-9.

The funding of commercial building budgets in general, and of the three 

budget elements of capital improvement, maintenance, and insurance, 

varies among owner organizations. Commercial building owners can fund 

their budgets by various combinations of equity and debt. 

Funding phase decisions are influenced by two factors: 

Regional and Local Economic Conditions. Externally, the funding of 

commercial building construction is subject to local and national 

socioeconomic conditions well beyond the control of the building 

owner. Construction funding depends on interest rates, the owner’s 

bond rating, and similar parameters.

❍

❍

Figure 1-9: Funding phase.
Integrated INCREMENTAL Building Protection 1-25

Bond Financing Regulations. The local administrative procedures and 

structure in place to obtain bond financing will have a significant 

impact on the ability of commercial building owners to achieve their 

objectives, regardless of whether they include terrorism risk reduction 

or not. Certain types of expenditures out of the proceeds of a bond 

issue, such as operations or maintenance, may be prohibited by the 

conditions of the bond.

1.6.7 The Maintenance and Rehabilitation

Implementation Phase of Commercial

Building Facility Management

The implementation phase includes design and construction and can 

be broken into three categories of projects, all of which are relevant to 

existing buildings:

Building acquisition projects

Capital improvement projects

Maintenance projects

The implementation phase is primarily affected by external Federal and 

State programs and building code requirements, as depicted in Figure 

1-10. 

❍

❍

❍

❍

Figure 1-10: Implementation phase.
1-26 Integrated INCREMENTAL Building Protection

Acquisition includes new building construction and the acquisition of 

existing buildings. Acquisition of existing buildings is discussed above as 

the first phase of the facility management process.

Capital improvement and maintenance projects are managed by the 

commercial building owner’s staff and carried out by the staff and 

contractors. The management of these two categories may be separated or 

combined, depending on issues of labor jurisdiction and legal authority. 

Implementation phase decisions are influenced by two factors: 

Federal and State Mandates and Programs. Externally, Federal and State 

programs may establish requirements affecting the implementation 

phase (e.g., ADA and OSHA requirements). 

Codes and Code Enforcement. Also externally, building codes impose 

requirements on the implementation phase in cases of repair, 

alteration, or addition to existing buildings. These requirements may 

be enforced by a State or local agency. Such requirements can add 

costs to a project and jeopardize feasibility, unless done incrementally. 

1.7 Planning and Managing 

Incremental Terrorism Risk 

Reduction

T he implementation of an integrated incremental building protection 

program is supported by decisions and actions in each phase of the 

facility management process described in the preceding section. 

There are nine steps of an incremental terrorism risk reduction program:

1. Conduct a Due Diligence Terrorism Risk Assessment

2. Identify and Implement Initial Increment Integration 

Opportunities

3. Assess Terrorism Risk 

4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

8. Define Budget Packaging

9. Implement Integrated Incremental Rehabilitation Project 

Management

❍

❍
Integrated INCREMENTAL Building Protection 1-27

Each of these steps relates to one (or more) of the facility management 

phases, as illustrated in the following table.

Facility Management 

Process Phase Steps of an Incremental Terrorism Risk Reduction Program

Acquisition 1. Conduct Due Diligence Terrorism Risk Assessment

Redevelopment 2. Identify and Implement Initial Increment Integration Opportunities

Use 3. Assess Terrorism Risk

Planning 4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

Budgeting 8. Define Budget Packaging

Funding

Implementation 9. Implement Integrated Incremental Rehabilitation Project Management

Table 1-2: Steps of an Incremental Terrorism Risk Reduction Program 

1.7.1 Step 1—Conduct a Due Diligence 

Terrorism Risk Assessment

This step is implemented in the acquisition phase of the facility 

management process. It may be performed by the owner (buyer), lender, 

and insurer. Each may include a Tier 1 FEMA 452 assessment (discussed 

in more detail in Chapter 2) or equivalent terrorism risk assessment in 

their implementation of due diligence.

Phase Steps of an Incremental Terrorism Risk Reduction Program

Acquisition 1. Conduct Due Diligence Terrorism Risk Assessment

Redevelopment 2. Identify and Implement Initial Increment Integration Opportunities

Use 3. Assess Terrorism Risk

Planning 4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

Budgeting 8. Define Budget Packaging

Funding

Implementation 9. Implement Integrated Incremental Rehabilitation Project Management
1-28 Integrated INCREMENTAL Building Protection

Phase Steps of an Incremental Terrorism Risk Reduction Program

Acquisition 1. Conduct Due Diligence Terrorism Risk Assessment

Redevelopment 2. Identify and Implement Initial Increment Integration Opportunities

Use 3. Assess Terrorism Risk

Planning 4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

Budgeting 8. Define Budget Packaging

Funding

Implementation 9. Implement Integrated Incremental Rehabilitation Project Management

1.7.2 Step 2—Identify and Implement Initial

Increment Integration Opportunities

This step is implemented in the initial redevelopment phase of the facility 

management process. As stated above, the types of redevelopment phase 

capital improvement projects vary, but generally consist of:

Architectural upgrading of entrances, lobbies, and public areas

Architectural upgrading of facades

Upgrading of the HVAC systems

Environmental and other risk remediation work identified in the due 

diligence process

Upgrading of life safety systems

The owner should consider using the guidance provided in Chapter 

2 of this manual to identify and implement specific terrorism risk 

reduction increments that can be integrated with these redevelopment 

capital improvements. Detailed information on specific risk reduction 

increments is presented in Chapters 3, 4, and 5. 

❍

❍

❍

❍

❍
Integrated INCREMENTAL Building Protection 1-29

Phase Steps of an Incremental Terrorism Risk Reduction Program

Acquisition 1. Conduct Due Diligence Terrorism Risk Assessment

Redevelopment 2. Identify and Implement Initial Increment Integration Opportunities

Use 3. Assess Terrorism Risk

Planning 4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

Budgeting 8. Define Budget Packaging

Funding

Implementation 9. Implement Integrated Incremental Rehabilitation Project Management

1.7.3 Step 3—Assess Terrorism Risk 

This step is implemented as part of the scheduled and recurring 

assessment activities carried out in the use phase of the facility 

management process. As stated above, some of these assessment activities 

may address the following issues:

❍ Specific environmental hazards ❍ Preventive maintenance needs

❍ Asbestos ❍ Structural hazards

❍ Lead paint ❍ Fire/life safety

❍ Lead ❍ Environmental quality

❍ Radon ❍ Energy use/conservation 

❍ User complaints ❍ Accessibility

❍ Maintenance needs ❍ Other

The owner should consider performing a Tier 1 FEMA 452 terrorism 

risk assessment (discussed in more detail in Chapter 2 of this manual) 

or equivalent as appropriate. Particular attention should be paid to the 

following factors: 

Government tenants, such as the U.S. General Services Administration 

or DoD, or government leased facilities that may have specific security 

requirements

Tenant complaints about perceived security vulnerabilities

❍

❍
1-30 Integrated INCREMENTAL Building Protection

1.7.4 Step 4—Develop a Security Master

Plan

This step is implemented as part of the planning phase of the facility 

management process. A security master plan relates to both strategic 

plans and facility plans. A security master plan should be a 3- to 5-year 

plan, based on the goals of the overall organization. It should state the 

vision, goals, and objectives of the security program. The plan should 

also outline the operational security measures, the path for the security 

program to keep pace with the changing threat environment, and 

future initiatives. Further, it should be benchmarked against the security 

programs of similar facilities. 

The security master plan provides the basis for all subsequent steps of the 

incremental terrorism risk reduction program.

A comprehensive Security Master Plan should:

Be communicated and disseminated to all levels of management and 

building occupants as appropriate

Be integrated into the facility construction or renovation planning

Be benchmarked or compared to related facilities

Be tested and evaluated

Identify threats/hazards, assets, vulnerabilities, and risks 

❍

❍

❍

❍

❍

Phase Steps of an Incremental Terrorism Risk Reduction Program

Acquisition 1. Conduct Due Diligence Terrorism Risk Assessment

Redevelopment 2. Identify and Implement Initial Increment Integration Opportunities

Use 3. Assess Terrorism Risk

Planning 4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

Budgeting 8. Define Budget Packaging

Funding

Implementation 9. Implement Integrated Incremental Rehabilitation Project Management
Integrated INCREMENTAL Building Protection 1-31

Establish a security improvement implementation schedule 

Establish a security operating and capital budget 

Follow regulatory or industry guidelines/standards 

The owner should consider requiring the development of a Security 

Master Plan in accordance with guidance provided in Chapter 5.

1.7.5 Step 5—Plan Incremental

Rehabilitation for Specific Buildings

This step is implemented as part of the planning phase of the facility 

management process. 

The owner should consider using the guidance provided in Chapter 2 of 

this manual to identify and implement specific terrorism risk reduction 

measures that can be integrated with planned maintenance and capital 

improvement projects. 

The incremental rehabilitation plan combines information from the 

Security Master Plan (Step 4) and the strategic and facility plans discussed 

in Section 1.5.4, and provides a coherent sequencing of increments.

❍

❍

❍

Phase Steps of an Incremental Terrorism Risk Reduction Program

Acquisition 1. Conduct Due Diligence Terrorism Risk Assessment

Redevelopment 2. Identify and Implement Initial Increment Integration Opportunities

Use 3. Assess Terrorism Risk

Planning 4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

Budgeting 8. Define Budget Packaging

Funding

Implementation 9. Implement Integrated Incremental Rehabilitation Project Management
1-32 Integrated INCREMENTAL Building Protection

1.7.6 Step 6—Stage Rehabilitation 

Increments 

This step is implemented as part of the planning phase of the facility 

management process, and is closely related to Step 5.

Consider the staging of increments of terrorism risk reduction on the 

basis of a life-cycle benefit analysis. Figure 1-11 illustrates such a lifecycle benefit analysis. The three wide arrows represent the benefits 

of single-stage rehabilitation occurring at three points in time: now, 

in 10 years, and in 20 years. Clearly, the largest benefit derives from a 

single-stage rehabilitation done now, and is designated as 100 percent. 

The benefits of single-stage rehabilitation done in the future must be 

discounted and expressed as some percentage lower than 100 percent, as 

represented by the smaller arrows. The stepped portion of the diagram 

represents incremental rehabilitation starting soon and completed in 

four increments over 10 years. The benefits of the future increments 

must also be discounted, and the benefit of the completed incremental 

rehabilitation is therefore expressed as a percentage lower than 100 

percent, but higher than the single-stage rehabilitation in year 10 or 

20. Reducing the overall duration of the incremental rehabilitation will 

increase its benefit, and extending the duration will decrease it.

Phase Steps of an Incremental Terrorism Risk Reduction Program

Acquisition 1. Conduct Due Diligence Terrorism Risk Assessment

Redevelopment 2. Identify and Implement Initial Increment Integration Opportunities

Use 3. Assess Terrorism Risk

Planning 4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

Budgeting 8. Define Budget Packaging

Funding 

Implementation 9. Implement Integrated Incremental Rehabilitation Project Management
Integrated INCREMENTAL Building Protection 1-33

Figure 1-11: Life-cycle benefit analysis.

1.7.7 Step 7—Coordinate with Tenant Work

This step is implemented as part of the planning phase of the facility 

management process, and is closely related to Step 5.

Phase Steps of an Incremental Terrorism Risk Reduction Program

Acquisition 1. Conduct Due Diligence Terrorism Risk Assessment

Redevelopment 2. Identify and Implement Initial Increment Integration Opportunities

Use 3. Assess Terrorism Risk

Planning 4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

Budgeting 8. Define Budget Packaging

Funding 

Implementation 9. Implement Integrated Incremental Rehabilitation Project Management
1-34 Integrated INCREMENTAL Building Protection

In addition to the integration opportunities with maintenance and capital 

improvement work done in Step 5, the owner should consider integrating 

additional increments of terrorism risk reduction with tenant work in 

coordination with the tenants.

1.7.8 Step 8—Define Budget Packaging

This step is implemented as part of the budgeting phase of the facility 

management process. 

The owner’s facility, risk, and financial managers should determine:

Potential losses due to terrorist attack (life, property, business 

interruption)

The owner’s potential liability related to terrorist attacks

The extent of security considerations attendant to government fiscal 

regulations applicable to the owner’s organization

The extent of lender-imposed terrorism risk insurance requirements 

The owner’s facility, risk, and financial managers should carefully plan the 

presentation of incremental security enhancement budgets to maximize 

the probability of their being approved, given the financial realities of the 

owner organization. A benefit-cost analysis as initiated in Step 6 can help. 

Concentrating on terrorism risk reduction measures that also reduce 

the risk of damage from natural disasters, and other causes may also be 

useful.

❍

❍

❍

❍

Phase Steps of an Incremental Terrorism Risk Reduction Program

Acquisition 1. Conduct Due Diligence Terrorism Risk Assessment

Redevelopment 2. Identify and Implement Initial Increment Integration Opportunities

Use 3. Assess Terrorism Risk

Planning 4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

Budgeting 8. Define Budget Packaging

Funding 

Implementation 9. Implement Integrated Incremental Rehabilitation Project Management
Integrated INCREMENTAL Building Protection 1-35

Phase Steps of an Incremental Terrorism Risk Reduction Program

Acquisition 1. Conduct Due Diligence Terrorism Risk Assessment

Redevelopment 2. Identify and Implement Initial Increment Integration Opportunities

Use 3. Assess Terrorism Risk

Planning 4. Develop a Security Master Plan

5. Plan Incremental Rehabilitation for Specific Buildings

6. Stage Rehabilitation Increments

7. Coordinate with Tenant Work

Budgeting 8. Define Budget Packaging

Funding 

Implementation 9. Implement Integrated Incremental Rehabilitation Project Management

1.7.9 Step 9—Implement Integrated

Incremental Rehabilitation Project 

Management

The implementation of the plans developed in Step 5, consisting of 

selected incremental security rehabilitation measures in combination with 

other building work, may require added attention to project design and 

bid packaging.

Fully brief or train in-house architects/engineers or outside 

consultants preparing the bid documents on the rationale behind the 

integration of physical protection and strengthening increments with 

the maintenance and capital improvement activities, as presented in 

Chapter 2 of this manual, to ensure that the terrorism risk reduction 

objectives are achieved. 

Ensure the continuity of building documentation from the analysis 

and design stages through construction and as-built drawings.

Conduct a pre-bid conference to explain to all prospective bidders 

the terrorism risk reduction objectives and the rationale for their 

selection.

In cases where security rehabilitation increments are to be 

implemented within tenant spaces, whether or not they are integrated 

with other items of tenant work, the tenant work and owner work 

should be well coordinated.

❍

❍

❍

❍
1-36 Integrated INCREMENTAL Building Protection

1.8 Terrorism Risk Assessment to

Terrorism Risk Reduction

T hese two activities, briefly discussed in this chapter as they relate 

to the phases of commercial building facility management, are 

discussed in detail in the Chapter 2.
MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection 2-1

2

MOVING FROM RISK assessment TO IMPLEMENTATION

OF INCREMENTAL Building Protection

T he terrorism risk assessment process 

described in FEMA 452, Risk Assessment: A 

How-To Guide to Mitigate Potential Terrorist 

Attacks Against Buildings, helps building owners 

to assess major vulnerabilities in a building and 

identify mitigation measures to correct such 

vulnerabilities. The information generated 

by the application of FEMA 452 and by the 

methodology provided in this manual are 

fundamental for implementing an incremental 

security enhancement process for existing 

commercial buildings.

A building owner or facility manager proceeding through the five steps 

of FEMA 452 described in Section 2.1 generates a series of physical 

protection and strengthening measures, as well as operational mitigation 

measures. In moving from a risk assessment to implementation, the 

building owner should check the compatibility of the former (physical 

protection and strengthening), as well as some of the latter (operational), 

with the maintenance and capital improvement plans. A matrix, as shown 

in Section 2.3, should be used to highlight opportunities for integration 

of specific mitigation options with specific maintenance or capital 

improvement activities.

2.1 Risk Assessment Process

T he risk assessment process described in FEMA 452 is based on five 

critical steps (Figure 2-1). These critical steps identify the best and 

most cost-effective terrorism mitigation measures for a building’s 

unique security needs. 

Conducting a threat assessment to identify, define, and quantify the 

threats or hazards is the first step of the risk assessment process. For 

terrorism, the threats are aggressors (people or groups) that are known to 

exist and that have the capability and a history of using hostile actions, or 

that have expressed intentions for using hostile actions against potential 

targets. Current credible information on targeting activity (surveillance 

of potential targets) or indications of preparation for terrorist acts may be 

available for these aggressors. 

The mitigation measures generated by 

the application of FEMA 452 provide the 

starting point for the application of this 

document. This document then demonstrates 

how a building owner or facility manager 

categorizes those mitigation measures into 

increments of terrorism risk reduction, and 

integrates the increments into ongoing or 

planned facility maintenance or capital 

improvement projects.
2-2 MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection

The second step of the risk assessment process is to identify the 

consequences of the loss of a building that needs to be protected from 

terrorist attack. Consequences relate to the criticality of the building in 

terms of the importance of the building operation to the owner and the 

locality, and can be defined as a degree of debilitation that would be 

caused by its destruction. This assessment of consequences can be applied 

to the entire building or significant portions of a very large building. It 

can also refer to a resource of value requiring protection. Consequences 

can be tangible (i.e., loss of buildings, facilities, equipment activities, 

operations, and information) or intangible (e.g., loss of processes or a 

company’s reputation).

As explained in FEMA 452, “after assessing consequences, the third 

step is to conduct a vulnerability assessment. A vulnerability assessment 

evaluates the potential vulnerability of the critical assets against a broad 

range of identified threats and natural hazards. By itself, the vulnerability 

assessment provides a basis for determining mitigation measures for 

protection of the building and its content. The assessment is a bridge in 

the methodology among threat/hazard, consequences, and the resultant 

level of risk.

“The fourth step of the process is the risk assessment. The risk assessment 

analyzes the likelihood or probability of the threat or natural hazard 

occurring and the consequences of the occurrence. Thus, a very high 

Figure 2-1: Risk assessment process model.
MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection 2-3

likelihood of occurrence with very small consequences may require 

simple low cost mitigation measures, but a very low likelihood of 

occurrence with very serious consequences may require more costly and 

complex mitigation measures. The risk assessment should provide a 

relative risk profile. High-risk combinations of assets against associated 

threats, with the identified vulnerability, allow prioritization of resources 

to implement mitigation measures.

“The fifth and final step is to consider mitigation options that are directly 

associated with, and responsive to, the major risks identified during Step 

4. From Step 5, decisions can be made as to where to minimize the risks 

and how to accomplish that over time.” 

2.1.1 Levels of Vulnerability Assessment 

FEMA 452 provides guidance in conducting varied levels of assessments, 

ranging from screening level assessments to in-depth assessments. As 

stated in FEMA 452, “the level of assessment for a given building is 

dependent upon a number of factors such as potential threat, type 

of building, location, type of construction, number of occupants, 

economic life, and other owner specific concerns and available economic 

resources.” FEMA 452 defines a three-tier assessment process as follows:

“Tier 1. A Tier 1 assessment is a ‘70 percent’ assessment. It can typically 

be conducted by one or two experienced assessment professionals in 

approximately two days. A Tier 1 assessment will likely be sufficient for 

the majority of commercial buildings and other non-critical facilities and 

infrastructure.

“Tier 2. A Tier 2 assessment is a ‘90 percent’ assessment. It typically 

requires three to five assessment specialists, can be completed in 3 to 5 

days, and requires key building staff participation. A Tier 2 assessment 

is likely to be sufficient for most high-risk buildings such as iconic 

commercial buildings, government facilities, schools, hospitals, and other 

high-value designated infrastructure assets.

“Tier 3. A Tier 3 assessment is a detailed evaluation of the building using 

blast, weapons of mass destruction (WMD), earthquake, flood, and high 

wind models to determine building response, survivability, and recovery, 

and the development of mitigation options. The assessment team is not 

defined for this tier; however, it could be composed of 8 to 12 people. 

Modeling and analysis can often take several days or weeks and is typically 

performed for high value and critical infrastructure assets.”
2-4 MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection

2.1.2 The Building Vulnerability

Assessment Checklist

FEMA 452 includes a Building Vulnerability Assessment Checklist, 

covering explosives, CBR, earthquakes, floods, and high-wind hazards. 

The checklist can be used to collect and report information related to the 

building. It compiles many best practices, based on the latest technologies 

and scientific research, to consider during the design of a new building or 

renovation of an existing building. 

The vulnerability assessment step is supported by the Building 

Vulnerability Assessment Checklist (FEMA 452, Appendix A), which is 

organized into 13 sections corresponding to building subsystems: 

1. Site

2. Architectural

3. Structural Systems

4. Building Envelope

5. Utility Systems

6. Mechanical Systems

7. Plumbing and Gas 

Systems

8. Electrical Systems

9. Fire Alarm Systems

10. Communications and IT 

Systems

11. Equipment Operations and Maintenance

12. Security Systems

13. Security Master Plan

The 13 sections of the Building Vulnerability Assessment Checklist 

provide a framework for the categorization of incremental measures of 

terrorism risk reduction discussed in the following sections. 

To support the building assessment 

process, a Risk Assessment 

Database has been developed 

as a companion tool to FEMA 

452. The database is a standalone application with several 

functions: import files and folders; 

display digital photos, emergency 

plans, and digital floor plans; and 

provide specific GIS tools. The 

database can be used to collect 

and report information related to 

the building.
MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection 2-5

2.2 Scheduling Increments: 

Physical Protection and

Strengthening Measures and

Operational (Protective and

Control) Measures

Once identified, the terrorism risk reduction improvements 

should be considered in relation to the owner’s ongoing facility 

planning for maintenance and capital improvements (discussed 

in Section 2.3). Physical protection and strengthening measures and 

some operational measures can then be integrated with maintenance 

and capital improvements using this document, and can be scheduled for 

implementation. 

2.2.1 Physical Protection and

Strengthening Measures

The increments of physical protections measures listed on the vertical 

axes of the integration matrices 1 and 2 in Section 2.3 are presented 

as an example of measures that might be generated by the FEMA 452 

process or others and implemented using this manual. The specific 

measures included in the matrices were generated for this manual and 

are discussed in Chapters 3, 4, and 5. Where applicable, the references in 

parentheses following items in the list refer to the respective discussions 

in Chapters 3, 4, and 5. The protection measures are presented in 

the order of the 13 sections of the Building Vulnerability Assessment 

Checklist in Appendix A of FEMA 452. 

2.2.2 Operational Measures

The list of incremental operational measures is presented in Chapter 5, 

Section 5.11 as an example of measures that might be generated by the 

FEMA 452 process or others and implemented using this manual. The 

specific measures included in the matrices were generated for this manual 

and are discussed in Chapters 4 and 5. Some of these measures include 

physical elements and are also included in the list that comprises the 

vertical axes of the integration matrices in Section 2.3. Where applicable, 

the references in parentheses following items in both lists (Section 2.3 

and Section 5.11) refer to the applicable discussions in Chapters 4 and 

5. The measures are presented in the order of the 13 sections of the 

Building Vulnerability Assessment Checklist in Appendix A of FEMA 452.
2-6 MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection

2.3 Identifying Integration 

Opportunities for Incremental

Building Protection

Typical maintenance and capital improvement projects in 

commercial buildings fall into two categories:

Maintenance and capital improvements that are common to all 

four types of commercial buildings—office, retail, and multifamily 

apartment buildings, and hotels.

Maintenance and capital improvements specific and unique to each of 

the four types of commercial buildings. 

These categories may also vary by building classification (A, B, or C). The 

following categorizations of maintenance and capital improvements are 

typical and reflect groupings of building elements, administrative and 

funding categories, tenant versus public spaces, or other parameters. 

Owners can substitute their own categories. 

Common categories of maintenance and capital improvement projects:

1. Roofing maintenance and repair/reroofing

2. Exterior wall and window maintenance/façade modernization

3. Fire and life safety improvements

4. Public area modernization (Retail: mall public areas; Hotels: 

public and service areas)

5. Underfloor and basement maintenance and repair

6. HVAC upgrade and energy conservation

7. Hazardous materials abatement

8. Landscaping and site work

Occupancy-specific categories of maintenance and capital improvement 

projects:

Office Buildings:

1. New technology accommodations

2. Tenant alterations and improvements

❍

❍
MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection 2-7

Retail Buildings:

1. Retail area modernization

Multifamily Apartment Buildings:

1. Kitchen and bathroom modernization

Hotels and Motels:

1. Guestroom finishing, furniture, and equipment (FF&E)

2. Public area FF&E

Both of these respective categories are used as the horizontal axes of the 

integration matrices presented on the following pages.

How to Use the Matrices

In order to identify integration opportunities, a building owner should 

follow these three steps:

1. Identify the column of the planned maintenance or capital 

improvement.

2. Identify the physical increments of building protection with a 

corresponding check mark in the column.

3. Consider integration of the physical increments with the planned 

maintenance or capital improvement activities.
2-8 MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection

Maintenance and

Capital Improvement Projects

Roofing maintenance & repairExterior wall & window workFire & life safety improvementsPublic area modernizationUnderfloor & basement workHVAC upgrade & energy workHazardous material abatementLandscaping

1. Site

1.1 Increased standoff distance (3.3) 4

1.2 Anti-ram vehicle barriers (3.3) 4

1.3 Speed calming devices (3.3) 4

1.4 Operable barriers (3.3) 4

1.5 Security lighting (5.8) 4

1.6 Detection & assessment 

measures

1.6.1 Exterior intrusion detection systems (5.2.1) 4

1.6.2 Access control systems (5.2.4) 4

1.7 Interdiction/response 

measures

1.7.1 Guard force—detection/delay role (5.3.1) 4

2. Architectural

2.1 Bracing or reinforcing masonry walls at interior stairs (3.5) 4 4

2.2 Restraint of hazardous materials containers (3.5) 4 4 4 4 4

2.3 Architectural isolation of lobby, mailroom, cloakroom, & loading docks (4.3.2) 4

2.4 Architectural measures to isolate mechanical spaces that require large volumes of 

outside air (4.4.3.2)

4 4

2.5 Vestibules or revolving doors for highly protected zones (4.3.5, 4.3.6) 4 4

2.6 Vestibules or revolving doors for protected zones (4.3.7) 4 4

2.7 Access control systems (5.2.4) 4 4

3. Structural Systems (3.6)

3.1 Upgrading the structure to make it more ductile 4 4 4 4 4 4

3.2 Upgrading spandrel beams to achieve catenary response 4

3.3 Upgrading slabs to achieve catenary response 4 4

3.4 Standoff distance around vulnerable columns (3.6.1) 4 4

3.5 Localized hardening of vulnerable columns (3.6.1) 4 4

3.6 Floor slab upload resistance (3.6.2) 4

Note: The references in parentheses refer to the applicable discussions in Chapters 3, 4, and 5.

Matrix 1: Integration Opportunities for Common Categories

of Maintenance and Capital Improvement Projects
MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection 2-9

Maintenance and

Capital Improvement Projects

Roofing maintenance & repairExterior wall & window workFire & life safety improvementsPublic area modernizationUnderfloor & basement workHVAC upgrade & energy workHazardous material abatementLandscaping

3.7 Load-bearing URM1 (3.6.3) 3.7.1 Shotcrete 4 4 4 4 4 4

3.7.2 Steel sections 4 4 4 4 4 4

3.7.3 Stiffened steel-plate wall system 4 4 4 4 4 4

3.7.4 Reinforcing 4 4 4 4 4 4

3.8 Transfer girder retrofit (3.6.4) 4

4. Building Envelope

4.1 Glazing 4.1.1 Fragment retention film (3.4.2) 4 4 4 4

4.1.2 Laminated glass (3.4.3) 4 4 4 4

4.1.3 Blast curtains (3.4.4) 4 4 4

4.1.4 Glazing catch cable/bar (3.4.5) 4 4 4

4.1.5 Energy absorbing cable systems (3.4.6) 4 4 4

4.2 URM (3.4.7) 4.2.1 Sprayed-on polymer 4 4 4 4

4.2.2 Geotextile fabric 4 4 4

4.2.3 Steel stud and sheetmetal construction 4 4 4

4.3 Other building envelope 

retrofits

4.3.1 Bracing parapets, gables, ornamentation, & 

appendages (3.4.8)

4 4

4.3.2 Cladding anchorage (3.4.1) 4

4.3.3 Anchorage of masonry veneer (3.4.8) 4

4.3.4 Anchorage of steel stud backup (3.4.8) 4 4 4 4

4.3.5 Anchorage of exterior wythe in cavity walls 

(3.4.8)

4

4.3.6 Debris catch systems for façade elements 

(3.4.8)

4 4 4 4

4.3.7 Increasing the roof’s resistance to blast (3.6) 4

4.3.8 Upgrading connections of light metal deck roofs 

to structure (3.6)

4

4.4 Sealing measures to tighten the envelope of the building and selected safe rooms 

(4.3.3)

4 4

Note: The references in parentheses refer to the applicable discussions in Chapters 3, 4, and 5.

1.	URM = unreinforced masonry

Matrix 1: Integration Opportunities for Common Categories

of Maintenance and Capital Improvement Projects (continued)
2-10 MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection

Maintenance and

Capital Improvement Projects

Roofing maintenance & repairExterior wall & window workFire & life safety improvementsPublic area modernizationUnderfloor & basement workHVAC upgrade & energy workHazardous material abatementLandscaping

5. Utility Systems

5.1 Light, secure, and monitor water service access points (5.8) 4 4 4

5.2 Intrusion detection sensors for all utility services to the building (5.8) 4 4 4 4

5.3 Redundant utility systems to support security, life safety, and rescue functions 4 4

5.4 Attachment and bracing of tanks (3.5) 4 4 4 4 4

6. Mechanical Systems (HVAC)

6.1 Fastening and bracing of mechanical equipment above ceilings (3.5) 4 4 4 4

6.2 Attachment and bracing of boilers and chillers (3.5) 4

6.3 Enhanced physical security 

(4.4.2.2)

6.3.1 Secure air intakes against unauthorized access 

(5.8.1)

4 4 4 4

6.3.2 Secure mechanical rooms & HVAC plenums 

against unauthorized access

4 4

6.4 Enhanced sheltering in 

place (4.4.3.2)

6.4.1 Single-switch control of fans for sheltering and 

purging

4

6.4.2 Automatic dampers for outside air intakes and 

exhaust fans

4 4

6.4.3 Separate fans & air streams for ventilation and 

recirculation for conditioning safe rooms

4

6.4.4 Recirculation filter units in safe rooms 4 4 4

6.5 Aerosol filtration, medium 

level (4.4.4.2)

6.5.1 Sealing filter frames to minimize bypass 4

6.5.2 Installation of filters of greater depth/surface 

area & higher MERV2 rating

4

6.5.3 Operating at positive internal pressures 4

6.6 Gas-phase filtration, 

medium level (4.4.5.2) 

6.6.1 Indoor-air-quality type, low resistance adsorbers 4

6.6.2 Operating at positive internal pressures 4

6.7 Aerosol filtration, high 

level (4.4.6.2)

6.7.1 Installation of ventilation/makeup-air units with 

HEPA3 filtration

4

6.7.2 Operating at positive internal pressures 4

Note: The references in parentheses refer to the applicable discussions in Chapters 3, 4, and 5.

2.	MERV = Minimum Efficiency Reporting Value

3.	HEPA = High Efficiency Particulate Air

Matrix 1: Integration Opportunities for Common Categories

of Maintenance and Capital Improvement Projects (continued)
MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection 2-11

Maintenance and

Capital Improvement Projects

Roofing maintenance & repairExterior wall & window workFire & life safety improvementsPublic area modernizationUnderfloor & basement workHVAC upgrade & energy workHazardous material abatementLandscaping

6.8 Gas-phase filtration, high 

level (4.4.7.2)

6.8.1 Ventilation/makeup-air units with high 

efficiency adsorbers & HEPA filtration

4

6.8.2 Operating at positive internal pressures 4

6.9 Secure and monitor exterior mechanical spaces and equipment (5.8) 4 4

6.10 Secure and monitor interior HVAC access points (5.8) 4 4

7. Plumbing & Gas Systems

7.1 Attachment and bracing of sprinkler piping (3.5) 4 4 4 4

8. Electrical Systems

8.1 Attachment and bracing of emergency lighting (3.5) 4 4 4 4

8.2 Fastening and bracing of electrical equipment above ceilings (3.5) 4 4 4 4

8.3 Attachment and bracing of transformers (3.5) 4 4 4 4

8.4 Attachment and bracing of emergency generators (3.5) 4 4 4 4

9. Fire Alarm Systems

10. Communications and IT Systems

10.1 Public address system to achieve rapid implementation of emergency actions 

(4.4.3.2)

4 4 4

11. Equipment Operations & Maintenance

12. Security Systems

12.1 Exterior intrusion detection systems (5.2.1) 4 4 4

12.2 Interior intrusion detection systems (5.2.2) 4 4 4 4

12.3 CCTV4 systems (5.2.3) 4 4 4 4 4 4 4 4

12.4 Duress alarms (5.2.6) 4 4 4 4

13. Security Master Plan

Note: The references in parentheses refer to the applicable discussions in Chapters 3, 4, and 5.

4.	CCTV = closed circuit television

Matrix 1: Integration Opportunities for Common Categories

of Maintenance and Capital Improvement Projects (continued)
2-12 MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection

Maintenance and Capital Improvement Projects

OFFICE RETAIL APARTMENT HOTEL

New TechnologyTenant AlterationsRetail Area ModernizationKitchen & Bath ModernizationGuestroom FF&EPublic Area FF&E

1. Site

2. Architectural

2.1 Bracing or reinforcing masonry walls at interior stairs (3.5)

2.2 Restraint of hazardous materials containers (3.5) 4 4 4 4

2.3 Architectural isolation of lobby, mailroom, cloakroom, & loading docks 

(4.3.2)

2.4 Architectural measures to isolate mechanical spaces that require large 

volumes of outside air (4.4.3.2)

2.5 Vestibules or revolving doors for highly protected zones (4.3.5, 4.3.6) 4

2.6 Vestibules or revolving doors for protected zones (4.3.7) 4

2.7 Access control systems (5.2.4) 4

3. Structural Systems

3.1 Upgrading the structure to make it more ductile 4 4 4 4 4 4

3.2 Upgrading spandrel beams to achieve catenary response (3.6.2

3.3 Upgrading slabs to achieve catenary response (3.6.2) 4 4 4 4

3.4 Standoff distance around vulnerable columns (3.6.1) 4 4

3.5 Localized hardening of vulnerable columns (3.6.1) 4 4

3.6 Floor slab upload resistance (3.6.2) 4 4 4 4

3.7 Load-bearing URM 

(3.6.3)

3.7.1 Shotcrete 4 4 4 4 4 4

3.7.2 Steel sections 4 4 4 4 4 4

3.7.3 Stiffened steel-plate wall system 4 4 4 4 4 4

3.7.4 Reinforcing 4 4 4 4 4 4

3.8 Transfer girder retrofit (3.6.4)

4. Building Envelope

4.1 Glazing 4.1.1 Fragment retention film (3.4.2) 4 4 4 4

4.1.2 Laminated glass (3.4.3) 4 4 4 4

4.1.3 Blast curtains (3.4.4) 4 4 4 4

4.1.4 Glazing catch cable/bar (3.4.5) 4 4 4 4

4.1.5 Energy absorbing cable systems 

(3.4.6)

4 4 4 4

Note: The references in parentheses refer to the applicable discussions in Chapters 3, 4, and 5. 

Matrix 2: Integration Opportunities for Occupancy-Specific Categories

of Maintenance and Capital Improvement Projects
MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection 2-13

Maintenance and Capital Improvement Projects

OFFICE RETAIL APARTMENT HOTEL

New TechnologyTenant AlterationsRetail Area ModernizationKitchen & Bath ModernizationGuestroom FF&EPublic Area FF&E

4.2 URM (3.4.7) 4.2.1 Sprayed-on polymer 4 4 4 4

4.2.2 Geotextile fabric 4 4 4 4

4.2.3 Steel stud and sheetmetal 

construction

4 4 4 4

4.3 Other building envelope 

retrofits

4.3.1 Bracing parapets, gables, 

ornamentation and appendages (3.4.8)

4.3.2 Cladding anchorage (3.4.1)

4.3.3 Anchorage of masonry veneer 

(3.4.8)

4.3.4 Anchorage of steel stud backup 

(3.4.8)

4 4 4 4

4.3.5 Anchorage of exterior wythe in 

cavity walls (3.4.8)

4.3.6 Debris catch systems for façade 

elements (3.4.8)

4 4 4 4

4.3.7 Increasing the roof’s resistance to 

blast (3.6)

4.3.8 Upgrading connections of light metal 

deck roofs to structure (3.6)

4.5 Sealing measures to tighten the envelope of the building and selected 

safe rooms (4.3.3)

4 4 4 4 4

5. Utility Systems

5.1 Light, secure, and monitor water service access points (5.8)

5.2 Intrusion detection sensors for all utility services to the building (5.8)

5.3 Redundant utility systems to support security, life safety, and rescue 

functions

4

5.4 Attachment and bracing of tanks (3.5)

6. Mechanical Systems (HVAC)

6.1 Fastening and bracing of mechanical equipment above ceilings (3.5) 4 4 4 4 4 4

6.2 Attachment and bracing of boilers and chillers (3.5)

6.3 Enhanced physical 

security (4.4.2.2)

6.3.1 Secure air intakes against 

unauthorized access (5.8.1)

6.3.2 Secure mechanical rooms & HVAC 

plenums against unauthorized access.

4

Note: The references in parentheses refer to the applicable discussions in Chapters 3, 4, and 5. 

Matrix 2: Integration Opportunities for Occupancy-Specific Categories

of Maintenance and Capital Improvement Projects (continued)
2-14 MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection

Maintenance and Capital Improvement Projects

OFFICE RETAIL APARTMENT HOTEL

New TechnologyTenant AlterationsRetail Area ModernizationKitchen & Bath ModernizationGuestroom FF&EPublic Area FF&E

6.4 Enhanced sheltering in 

place (4.4.3.2)

6.4.1 Single-switch control of fans for 

sheltering and purging

6.4.2 Automatic dampers for outside air 

intakes and exhaust fans

6.4.3 Separate fans & air streams 

for ventilation and recirculation for 

conditioning safe rooms 

6.4.4 Recirculation filter units in safe 

rooms

4 4 4 4

6.5 Aerosol filtration, 

medium level (4.4.4.2)

6.5.1 Sealing filter frames to minimize 

bypass

6.5.2 Installation of filters of greater 

depth/surface area & higher MERV rating

6.5.3 Operating at positive internal 

pressures

6.6 Gas-phase filtration, 

medium level (4.4.5.2)

6.6.1 Indoor-air-quality type, low 

resistance adsorbers

6.6.2 Operating at positive internal 

pressures

6.7 Aerosol filtration, high 

level (4.4.6.2)

6.7.1 Installation of ventilation/makeupair units with HEPA filtration

6.7.2 Operating at positive internal 

pressures

6.8 Gas-phase filtration, high 

level (4.4.7.2)

6.8.1 Ventilation/makeup-air units with 

high efficiency adsorbers & HEPA filtration

6.8.2 Operating at positive internal 

pressures

6.9 Secure and monitor exterior mechanical spaces and equipment (5.8)

6.10 Secure and monitor interior HVAC access points (5.8) 4 4 4

7. Plumbing & Gas Systems

7.1 Attachment and bracing of sprinkler piping (3.5) 4 4 4 4 4 4

8. Electrical Systems

8.1 Attachment and bracing of emergency lighting (3.5) 4 4 4

8.2 Fastening and bracing of electrical equipment above ceilings (3.5) 4 4 4 4 4 4

8.3 Attachment and bracing of transformers 

8.4 Attachment and bracing of emergency generators

Note: The references in parentheses refer to the applicable discussions in Chapters 3, 4, and 5. 

Matrix 2: Integration Opportunities for Occupancy-Specific Categories

of Maintenance and Capital Improvement Projects (continued)
MOVING FROM RISK assessment TO IMPLEMENTATION OF INCREMENTAL Building Protection 2-15

Maintenance and Capital Improvement Projects

OFFICE RETAIL APARTMENT HOTEL

New TechnologyTenant AlterationsRetail Area ModernizationKitchen & Bath ModernizationGuestroom FF&EPublic Area FF&E

9. Fire Alarm System

10. Communications and IT Systems

10.1 Public address system to achieve rapid implementation of emergency 

actions (4.4.3.2)

4 4

11. Equipment Operations & Maintenance

12. Security Systems

12.1 Exterior intrusion detection systems (5.2.1) 4

12.2 Interior intrusion detection systems (5.2.2) 4 4 4 4

12.3 CCTV systems (5.2.3) 4 4 4 4 4

12.4 Duress alarms (5.2.6) 4 4 4 4

13. Security Master Plan

Note: The references in parentheses refer to the applicable discussions in Chapters 3, 4, and 5. 

Matrix 2: Integration Opportunities for Occupancy-Specific Categories

of Maintenance and Capital Improvement Projects (continued)

PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-1

3

PRINCIPLES OF DESIGN FOR RISK

REDUCTION RELATED TO BLASTS

Most commercial buildings in the 

United States have not been 

designed and constructed to resist 

blasts. Therefore, the results of a FEMA 452 

risk assessment may yield many high-risk scores 

to explosive blasts. New technologies and 

mitigation options are available to incrementally 

reduce the consequences of explosive blasts.1

Some existing buildings may require retrofits 

for explosive threats if changes in purpose, 

occupancy, or world events make them 

more likely to be targets of a terrorist attack. 

Similarly, prudent facility managers should also 

consider whether nearby buildings are likely 

targets for terrorist attack. Conducting a risk 

assessment is the first step in determining the 

need to upgrade a conventionally designed 

building to protect its occupants and assets. 

The risk assessment identifies the maximum 

credible threats and the associated hazards 

based on the site conditions, neighboring 

properties, building layout, access control, structural framing, and facade 

components.

The effectiveness of the upgrades depends to a great extent on the 

structural details of the building and the acceptability of the aesthetic 

and functional impacts. For example, historic preservation requirements 

may limit secure design alternatives that would otherwise be considered 

appropriate. The cost of protective design and the impact of this 

protection on the property may be minimized using advanced analytical 

methods. These methods, developed over years of explosive testing 

and numerical simulation, enable the design team to focus resources 

on portions of the structure that are most likely to sustain damage and 

minimize materials required to mitigate these hazards. The protective 

measures that may offer the most benefits from these methods include 

1.	 Much of the content for this chapter has been drawn from the articles “Designing to Resist Explosive Threats”

and “Retrofits to Resist Explosive Threats” by Robert Smilowitz. These documents were originally prepared

for the National Institute of Building Sciences in 2005 and later published on their Web-based portal, Whole

Building Design Guide (www.wbdg.org), as a resource for building professionals.

FEMA 452, Risk Assessment: A How-To 

Guide to Mitigate Potential Terrorist Attacks 

Against Buildings, January 2005, outlines 

methods for identifying the critical assets 

and functions within buildings, determining 

the threats to those assets, and assessing 

the vulnerabilities associated with those 

threats. The Guide provides a means to 

assess the risk and make risk-informed 

decisions to reduce vulnerability. The 

Guide also discusses methods to reduce 

physical damage to structural and nonstructural components of buildings and 

related infrastructure and reducing resultant 

casualties that may occur during an 

explosive or CBR attack. Finally, the Guide 

leads the reader through a process for 

conducting a risk assessment and selecting 

mitigation options.
3-2 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

the design of defensible perimeters, the design of protective facade 

systems, the hardening of structures to resist the effects of progressive 

collapse, the retrofit of existing structures, and the protection of nonstructural components. The following sections describe retrofit upgrades 

that may be used to either reduce the hazard of debris impact or increase 

the load resistance of the structure. 

This chapter identifies the protective measures that may be applied to the 

building perimeter, structure, and envelope, and non-structural systems 

within the incremental framework. Starting from the exterior of the 

building and working inward, these distinct protective upgrade projects 

may be combined with building maintenance and capital improvement 

projects. For buildings perceived as vulnerable to attack by virtue of 

their iconic nature or controversial occupancy, perimeter protection 

projects or column hardening may be beneficial. For other buildings, 

which may be in the vicinity of a likely target, perimeter protection and 

structural hardening will not reduce the risk of collateral damage. A 

protective facade upgrade makes more sense for these buildings. The 

incremental approach allows building owners to identify the best use 

of limited resources and combine these protective measures with other 

modernization projects that may increase the value of their property. 

Following a brief description of significant terrorist attacks against 

commercial properties, this chapter explores protective measures for: 

Building perimeters 

Building structures 

Building envelopes 

Non-structural systems

3.1 Selected Examples of Terrorist 

Attacks on Buildings

T he following sections describe past terrorist attacks on buildings 

and the extent of collateral damage to neighboring structures.2

The approximate dollar values for damages correspond to the 

time of the incident. These descriptions of blast damage inform the 

methods of assessing building vulnerabilities described in FEMA 452 and 

the physical and operational enhancements to address vulnerabilities to 

explosive blasts described in this document.

.	 These descriptions were first published in 2007 as part of FEMA 430, Site and Urban Design for Security.

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-3

3.1.1 Baltic Exchange,3 City of London, 

April 1992

Founded in the mid-eighteenth century, the Baltic Exchange is a United 

Kingdom company that operates the premier global marketplace for 

shipbrokers, ship owners, and charterers. It occupied a historic London 

building built in 1903. 

In April 1992, at 9:20 p.m., the offices of the Baltic Exchange at 30 St. Mary 

Axe, London were virtually destroyed in an Irish Republican Army (IRA) 

bomb attack. A small truck carrying the explosives pulled up to the building 

on St. Mary Axe, a narrow street in the heart of London’s financial district. 

The attack represents the first use of a large fertilizer-based homemade 

explosive device: the bomb’s power was enhanced by a Semtex-based 

detonating cord wrapped around the explosives. Although most of the 

office workers had gone home, the bomb killed three people, all by flying 

glass, and injured 91. The damage was estimated at about $1.2 billion. 

3.1.2 World Trade Center,4 New York City, 

February 1993

On Friday, February 26, 1993, at 12:18 p.m. a large explosion ripped 

through the public parking garage of the World Trade Center. The 

explosion caused six deaths, more than 1,000 injuries, and $300 million in 

property damage. 

The explosive device, a 1,500-pound urea-nitrate bomb (equivalent 

to about 900 pounds of trinitrotoluene [TNT]), was detonated in a 

rented Ford van parked in the basement parking garage using a timer. 

The explosion created a 200-foot by 100-foot crater several stories deep 

(Figure 3-1). The power and emergency systems of the World Trade 

Center were destroyed. Most of the injuries were due to smoke inhalation. 

.	 SOURCES: Jonathan Bell, “The Morning News: Letters from London: Raising the Game”; Peter Dorsman,

“Peak Talk, The Baltic Exchange Bomb,” from www.peaktalk.com/archives/000143.php; “London Destruction:

Baltic Exchange,” from http://us.geocities.com/londondestruction/baltic.html; Leslie Hutchings, “Discussion

Forum,” from www.sapling.info/discussionforum/postings/1104.shtml.

.	 SOURCES: ADL Law Enforcement Agency Resource Network; CNN, “WTC’s owners found negligent in 1993

bombing”; “The 1993 Bombing: the First Attack on the World Trade Center,” from http://911research.wtc7.

net; John V. Parachini, “February 1993 Bombing of the World Trade Center in New York City,” CNS Center

for Nonproliferation Studies, from http://cns.miis.edu/pubs/reports/wtc93.htm; J. Dwyer et al., Two Seconds 

Under the World: Terror Comes to America—The Conspiracy Behind the World Trade Center Bombing, Crown

Publishers, New York, 1994.
3-4 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

3.1.3 Bishopsgate,5 City of London, April

1993

A bomb hidden in the back of a large truck exploded in a narrow 

street, killing one person and injuring more than 40. The explosive was 

a homemade device using about 1 ton of fertilizer and was similar to 

the bomb that devastated the nearby Baltic Exchange (Section 3.1.1). 

The explosion shook buildings and shattered hundreds of windows, 

sending glass showering down into the streets below. A medieval church, 

St. Ethelburga’s, collapsed. Another church and the Liverpool Street 

underground station were also destroyed. 

The damage was estimated at more than $1.5 billion. The Baltic 

Exchange, just having reopened following the completion of repairs 

from the 1992 bombing, was again damaged. Huge insurance payouts 

contributed to a crisis in the insurance industry, including the near 

financial collapse of the world’s leading insurance market, Lloyds of 

London.

.	 SOURCES: BBC On This Day, 1993, “IRA bomb devastates City of London”; Jonathan Liebenau, London

School of Economics, “Information and Communications Disaster Recovery.”

Figure 3-1: Damage in 

WTC garage caused 

by the 1993 bomb 

attack.

SOURCE: Corbis
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-5

3.1.4 Town Center, Manchester,6 England, 

June 1996

On June 15, 1996, at a peak shopping time on Father’s Day, a 3,000-

pound IRA bomb (equivalent to about 1,800 pounds of TNT) exploded 

in Manchester, the second largest city in the United Kingdom. The 

explosion injured more than 200 people and ripped into the fabric of the 

city’s main shopping center (Figure 3-2). 

Several telephone warnings about an hour before the blast and the 

subsequent police evacuations averted major casualties. Shoppers were 

evacuated from the Marks and Spencer Department Store at the center of 

the site, outside which the truck bomb was parked. An army bomb squad 

employing a robotic anti-bomb device was checking an illegally parked 

van, which had been recorded by several closed-circuit security cameras in 

the city, when the bomb exploded.

Most injuries were sustained from falling glass and building debris. The 

main railroad stations were closed for several hours, and the city center 

was sealed off. 

An estimated 450,000 square feet of retail space and about 200,000 

square feet of office space required reconstruction. A master plan for 

redevelopment of the city center was quickly developed. An international 

.	 SOURCES: John Moss, “Manchester 2004, The Manchester Bombing, June 1996,” from www.manchester

2002-uk.com/buildings/bombing.html; BBC On This Day, 1996, “Huge explosion rocks central Manchester.”

Figure 3-2: Manchester 

shopping center 

damage.

SOURCE: Corbis
3-6 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

urban design competition launched one month after the bombing 

provided a cohesive plan for rebuilding. After 4 years, the devastated zone 

was completely restored. Marks and Spencer rebuilt on its original site, 

with its largest store in the world (Figure 3-3). 

3.2 Performance Standards 

Based on such recent experience of terrorism blast damage in 

commercial buildings, methods of analysis and design have 

been developed to reduce damage in existing buildings. These 

methods are discussed below.

A building’s performance in response to blast loadings must be evaluated 

whether it is a likely target or close enough to a likely target to suffer 

collateral damage. The effects of a near contact detonation, such as a 

satchel threat placed in contact with a column or a vehicle-transported 

explosive near the structure, are significantly different from the effects 

of a distant detonation. Different analytical methods are required to 

evaluate the likely performance of building systems in response to varied 

intensities of blast loading. 

Appropriate analytical methods are needed to demonstrate compliance 

with blast criteria or performance specifications established by agencies, 

such as the General Services Administration, the U.S. Department of 

Figure 3-3: New Marks 

and Spencer store, 

Manchester.

Source: Chris Arnold
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-7

State, and others. Risk-based 

performance criteria must be 

established for each building in 

order to define the protective 

objectives. Continuity of services 

objectives require performance 

criteria that are significantly 

more severe than those for a life 

safety objective. Consequently, 

establishing the design objectives 

at the onset is important. 

Furthermore, many of these 

performance criteria require that 

the building system be a balanced 

design. The objectives of balanced 

design are to fully utilize the 

load capacity of all the materials, 

maximize the potential energy 

dissipated due to deformation, 

and manage the failure 

mechanisms. These objectives 

can be accomplished by ensuring a controlled sequence of failure. The 

expected performance of the building systems in response to either a 

targeted attack or collateral damage will determine the level of protection 

required, the sizing of the structural and nonstructural members, and the 

design of the connections between the different building components.

The behavior of structural materials, such as steel and aluminum, 

in response to explosive loading has been the subject of intensive 

investigation by the governments of the United Kingdom, Israel, and 

the United States of America. Some structural materials behave very 

differently when subjected to high strain rate loading than they do under 

static conditions. Furthermore, the inelastic deformation of structural 

members depends on their section properties, shape functions, and 

extent of deformation. For compound sections composed of different 

pieces and materials, transformed section properties may be used to 

characterize an equivalent material and a combined or composite section 

property may be used to represent its structural resistance. Care must be 

taken to calculate composite section properties when strain compatibility 

between components can be justified and combined section properties 

when deformation compatibility between components is achieved.

Dynamic Analysis of Buildings

The performance of building systems and components in 

response to blast loading may be evaluated numerically 

using the principals of Structural Dynamics. These methods 

represent the inertia, the stiffness, and the strength of the 

dynamic system using a combination of nonlinear springs 

and masses. Simple Single Degree of Freedom (SDOF) 

models are appropriate for components on which the 

loading is uniform and the response is well characterized 

by the nonlinear spring. More complex material behavior, 

dynamic loading effects, and geometric nonlinearities 

require more complex Multi-Degree of Freedom (MDOF) 

models. The most complex structural systems must be 

analyzed using Finite Element Methods (FEM), which 

determines the nonlinear dynamic response using an 

explicit formulation of the equations of motion. Each 

level of analytical complexity requires successively more 

experience and expertise on the part of the blast response 

analyst.
3-8 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

3.3 Site Incremental Upgrades: 

Perimeter Protection

T he risk analysis will help facility owners determine whether their 

building is a likely target or close enough to a likely target to 

suffer collateral damage. Perimeter protection only improves 

the performance of buildings that are targets of explosive attacks and 

provides no reduction in hazard if the building is vulnerable to collateral 

damage. However, characteristics of explosives, such as the charge 

weight, the efficiency of the chemical reaction, and the source location, 

The performance of building systems in response to explosive loading is 

highly dynamic, highly inelastic, and highly interactive. By controlling the 

flexibility and resulting deformations, the structural or facade component 

may be designed to dissipate considerable amounts of blast energy. The 

phasing of the different component responses and the energy that is 

dissipated through inelastic deformation must be carefully represented in 

order to accurately determine the behavior of the components. The ‘SDOF 

model’ approach commonly used to analyze individual components is 

likely to produce conservative designs. An accurate representation of the 

structural system requires a complex MDOF model. These MDOF models 

may be developed using appropriate inelastic Finite Element software in 

which an explicit formulation of the equations of motion is solved. 

Advanced analytical methods provide the most authentic 

representation of the system’s ability to resist the dynamic blast 

loading and will produce the most cost-effective retrofits wherever 

the strength of the system is being evaluated. 

Simplified analytical methods and empirical relations are sufficient 

for debris mitigating upgrades, such as a daylight application of 

fragment retention film or blast resistant glazing fabricated with 

laminated glass. 

Approximate methods, such as the ASTM F 2248-03, Standard 

Practice for Specifying an Equivalent 3-Second Duration Design 

Loading for Blast Resistant Glazing Fabricated with Laminated 

Glass, do not require advanced analytical methods. Although this 

approximate approach does not quantify the improved behavior 

of glass in response to blast loading it “provides a design load 

suitable for sizing blast resistant glazing comprised of laminated 

glass or insulating glass fabricated with laminated glass” (ASTM, 

2003). 

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-9

that would likely be used in such attacks cannot be reliably predicted. 

Given these uncertainties, the most effective means of protecting a 

structure is to keep the bomb as far away from the building as possible 

by maximizing the standoff distance. Facility managers often respond 

to world events by constructing a perimeter around their building even 

before they evaluate the risk to their building. This approach presumes 

the facility will be the target of a terrorist attack and is intended to either 

discourage the attacking vehicle or to prevent it from driving up against 

the structure. Although a temporary incremental rehabilitation measure 

may be an appropriate strategy until a risk assessment can be performed, 

a permanent perimeter protection installation requires an intensive study 

of traffic patterns and subgrade conditions. 

To guarantee the maximum standoff distance between unscreened 

vehicles and the structure and to resist a moving vehicle attack, anti-ram 

barriers must be placed around the entire perimeter of the building. For 

urban buildings, the defensible perimeter is most effectively located as 

close to the curb as possible in order to maximize the available standoff 

distances. More standoff distance is typically available at suburban and 

rural sites and there may be more options for locating the defensible 

perimeter without diminishing effectiveness. The site conditions 

determine the maximum vehicle speeds attainable, and thus the kinetic 

energy that must be resisted. Both the impact-protective device (bollard 

or barrier) and its foundation must be designed to resist the maximum 

load (see Figure 3-4). Permanent barriers, especially ones rated for high 

impact levels, generally have very large, deep foundations. Placement 

of these foundations is difficult in urban areas because underground 

Figure 3-4: Barriers and 

bollards.
3-10 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

transportation facilities, building vaults, and utilities are often densely 

packed, and their locations may not be documented correctly or at all. 

Surveys and testing must be performed before construction begins to 

fully understand the feasibility and extent of these complications and to 

develop an appropriate design. 

Conversely, if design restrictions limit the capacity of the impact-protective 

device or its foundation, then site restrictions will be required to limit 

the maximum speeds attainable. Speed calming devices may be installed 

to control the speed of oncoming vehicles. Furthermore, public parking 

abutting the building must be secured or eliminated, and street parking 

should not be permitted adjacent to the building. Removing one lane 

of traffic and turning it into an extended sidewalk or plaza can add 

additional standoff distance. However, the practical benefit of increasing 

the standoff depends on the charge weight. If the charge weight is small, 

this measure will significantly reduce the forces to a more manageable 

level. If the threat is a large charge weight, the blast forces may overwhelm 

the structure despite the addition of several feet to the standoff distance, 

and the measure may not significantly improve survivability of the 

occupants or the structure.

Entrances to parking garages and loading docks require operable barriers 

so that security personnel have the means to deny access to unauthorized 

vehicles following an inspection of their credentials or the contents of 

their cargo space. These operable barriers must be located to provide 

security personnel an effective means to inspect vehicles while minimizing 

the impact of queues on surrounding traffic patterns. Furthermore, the 

surrounding structure must be designed to accept the large dynamic 

forces that may be transferred upon impact.

3.4 Incremental Building 

Rehabilitation Measures

3.4.1 Building Envelope

One of the most formidable tasks facing property owners is the 

upgrade of an existing facade to resist blasts. Blast pressures 

engulf a structure, and glass damage can occur as far as a 

mile from a sizable vehicle detonation. Glass damage from the terrorist 

bombing in Oklahoma City was reported up to 4,000 feet away from the 

Murrah Building (see Figure 3-5). Because the intensity of blast loads vary 

as a function of height and exposure relative to the point of detonation, 

facility managers may be able to prioritize upgrades to take advantage of 

site-specific features. This is particularly true if another nearby building is 
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-11

identified to be the likely target of the attack and the directionality of the 

blast waves produce reflected pressures on some surfaces and not others. 

Similarly, results of a blast analysis may permit upper floors to be treated 

differently from lower floors. 

Contractors rarely have access to the entire facade from within the 

building unless the building is undergoing a major modernization. But 

when these opportunities do arise, a significant level of protection can 

be introduced into the existing structure. This is particularly true when 

Figure 3-5: Locations 

of Murrah Building 

and other damaged 

structures.
3-12 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

the design team uses state-of-the-art technologies. With conventional 

approaches, all glazing is treated as if it were supported in rigid openings; 

however, the actual performance of flexible facade systems in response to 

blast loading may be far more forgiving. An accurate representation of the 

glazing response to blast loading requires proper understanding of the 

facade’s flexibility. The full load-bearing capacity of all the components 

may then be realized through the appropriate detailing of the mullions, 

connections, and anchorages. Over-design of glass and its support 

structure can lead to wasted money and in some cases premature failure.

Since the retrofit of existing structures is often hampered by insufficient 

information about the structure and the presence of brittle materials, 

innovative energy-absorbing retrofit systems may provide the best 

protection for these aging structures. Although difficult to quantify 

by simplified analytical approaches, these energy absorbing systems 

have been demonstrated to transfer reduced forces to the surrounding 

structure. Once the decision to upgrade a facade is made, advanced 

analytical methods can be used to enhance blast resistance at a 

minimum cost. 

The increased mass of precast panels and masonry walls make them more 

vulnerable to greater intensity blast pressures than glazed facades. The 

strength of unreinforced masonry (URM) or lightly reinforced precast 

panels may be increased with the adhesion of fiber reinforcement to 

the inner surface, and debris may be restrained with the application of 

an elastopolymer; however, the connection details typically present the 

greatest difficulty for new construction and for incremental rehabilitation 

measures. The anchorages of precast concrete panels must develop the 

panels’ ultimate capacity, in response to direct loading and rebound, in 

order to develop the full blast resistance of the material. Similarly, the 

anchorage of grouted and reinforced masonry walls must be designed to 

take full advantage of the materials’ strength. Debris catch systems, such 

as geotextile fabrics and steel stud walls, may be installed interior to the 

precast panels and masonry walls if the reinforcement is insufficient and 

the anchorages are inaccessible. 

3.4.2 Fragment Retention Film

Fragment retention film, also commonly known as “shatter-resistant 

window film” or “security film,” is a laminate used to improve post-failure 

performance of existing windows. Applied to the interior face of glass, 

fragment retention film holds the fragments of broken glass together in 

one sheet, thus reducing the projectile hazard of flying glass fragments. A 

more appropriate name for fragment retention film would be “fragment 

reduction” film, since the methodology behind this hazard mitigation 
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-13

technique focuses on retaining glass fragments resulting from blast 

overpressures. 

Most fragment retention films are made from polyester-based materials 

and coated with adhesives. Clear and tinted fragment retention films are 

available. Clear film has minimal effects on the optical characteristics of 

the glass; tinted film can increase the effectiveness of existing heating/

cooling systems, while also providing a variety of aesthetic and optical 

enhancements. Most films are designed with solar inhibitors to screen out 

ultraviolet (UV) rays, though over time the UV absorption damages the 

film’s adhesive and degrades its effectiveness. 

Film is packaged on rolls in widths as small as 24 inches and as large as 72 

inches, depending on the manufacturer. Some manufacturers laminate 

multiple layers of film together to enhance performance. Whether oneply or multi-ply, the overall film thickness can range from 2 to 15 mils. 

According to some government criteria (and verified by published 

test results), a 7-mil thick fragment retention security film, or specially 

manufactured 4-mil thick film, is considered to be the minimum thickness 

required to provide effective response to blast loads. 

There are three types of fragment retention film installation methods. 

Each of the methods is capable of resisting different intensities of blast 

pressure, with the daylighting installation providing the lowest level of 

protection and the mechanically anchored installation providing the 

highest level of protection. Therefore, the selected installation method 

for incremental rehabilitation should be based on the required level of 

protection. For example, the reduction of fragment hazard in response 

to collateral damage may permit the use of the least invasive installations. 

The different installation methods are:

Dry-Glazed Installation 

Wet-Glazed Installation 

Mechanically Anchored Installation

Dry-Glazed Installation. The application of security film must, at a 

minimum, cover the clear area of the window (i.e., the portion of the 

glass unobstructed by the frame). This minimum application to the 

exposed glass without any means of attachment or capture within the 

frame, termed “daylighting installation,” is commonly used for retrofitting 

windows. Application of the film to the edge of the glass panel where it 

would cover the glass within the bite is called an edge-to-edge installation. 

Other methods of application may improve film performance and further 

reduce hazards but are typically more expensive to install, especially in 

retrofits.

❍

❍

❍
3-14 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

Energy absorbing catch systems, used in conjunction with a daylight 

application of fragment retention film, is another mechanism for 

retaining and reducing debris hazards. Cables spanning the window 

will impede the flight of filmed glass and absorb a considerable amount 

of energy upon impact. These cable catch systems are demonstrated, 

through explosive testing, to be more efficient and effective than the 

more rigid catch bar systems described below.

Wet-Glazed Installation. The wet-glazed installation is a method in which 

the film is positively attached to the frame using a high-strength, liquid 

sealant, such as silicone. Frequently used for field retrofits, the method 

allows the flexible frame to deform slightly, reducing glass fragments 

entering the building and offering more protection than the dry-glazed 

installation. The wet-glazed installation system is more costly than the dryglazed installation method, but is less expensive than the mechanically 

anchored/attached installation method described below.

Mechanically Anchored/Attached Installation. Fragment retention film is 

most effective when it is used in conjunction with a blast-tested anchorage 

system. While a film may be effective in keeping glass fragments together, 

it may not be particularly effective in retaining the glass in the frame. 

Securing the film to the frame with a mechanically connected anchorage 

system further reduces the likelihood of the glazing system exiting the 

frame. Mechanical anchorage systems employ screws and/or batten strips 

to attach the film to the frame along 2 or 4 sides. Because additional 

framework is necessary, the mechanical attachment method can be less 

aesthetically pleasing than the wet-glazed installation system.

All application and attachment methods can be installed on site in either 

steel or aluminum frames. While some mechanically attached systems may 

be used for a wide variety of windows, others are designed for a particular 

type of window frame. Certain types of window frames may require a 

custom-fabricated anchorage system.

In addition to considering the various methods of installation, the 

designer must consider the thickness of the film and the task of 

positioning the film on the glass. A lighter weight or thinner film eases 

installation. Water used to aid in positioning the film during application 

must be thoroughly extruded, as the film is not very permeable and 

moisture that does not dry will prevent the development of the full 

adhesive bond strength. Fragment retention film should be carefully 

selected for its physical, optical, and thermal characteristics, with special 

consideration given to the adhesive used, the window thickness, and the 

window area. Window frame systems must also be capable of transferring 

the load collected by the glazing system. Corner-welded frames are 
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-15

preferred over frames constructed of individual components. A schematic 

of this mitigation measure is shown in Figure 3-6.

3.4.3 Laminated Glass

Laminated glass consists of two or more pieces of glass permanently 

bonded together by a tough plastic interlayer made of polyvinyl butyral 

(PVB) resin. Once sealed together, the glass “sandwich” behaves as a single 

unit. Annealed, heat strengthened, tempered glass or polycarbonate 

glazing can be mixed and matched between layers of laminated glass 

Figure 3-6: Mechanically 

attached fragment 

retention film.
3-16 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

in order to design the most effective lite for a given application. When 

fractured, fragments of laminated glass tend to adhere to the PVB 

interlayer instead of falling freely and potentially causing injury.

Laminated glass usually lasts as long as ordinary glass if it is not broken 

or damaged. The correct installation of laminated glass is very important 

to ensure long life. Manufacturers typically recommend installation 

of laminated glass on setting blocks that are at least 6 inches long and 

placed at the quarter points of the pane. Architectural details should 

incorporate a weep system for exterior glazing systems. Regardless of 

the degree of protection required, laminated glass needs to be installed 

with a proper sealant to ensure that no water comes in contact with the 

edges of the glass. The sealant supplier should verify that the sealant and 

PVB interlayer are compatible. Generic sealants shown to be compatible 

with PVB are the polysulfides, silicones, butyl or polybutene tapes, and 

polyurethanes. Minimum face and edge clearance should be provided as 

required by the manufacturer. Field cutting should be minimized in butt 

glazing installations to minimize edge defects. Glazing guidelines, such as 

those presented in the Glass Association of North America (formerly Flat 

Glass Marketing Association) Glazing Manual should be followed to avoid 

installation problems. Typical allowances for glass, metal, and erection 

tolerance, expansion, and contraction should be made.

3.4.4 Blast Curtains

Blast curtains (see Figure 3-7) are attached to the interior frame of a 

window opening and essentially catch the glass fragments produced by 

a blast wave. The debris is then deposited on the floor at the base of 

the window. The use of these curtains does not eliminate the possibility 

of glass fragments penetrating the interior of the occupied space, but 

instead limits the travel distance of the airborne debris. Overall, the 

hazard level to occupants is significantly reduced by the installation of 

blast curtains. However, a person sitting directly adjacent to a window 

outfitted with a blast curtain may still be injured by shards of glass in the 

event of an explosion.

Figure 3-7: Blast 

curtains.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-17

Blast curtains are made from a variety of materials, including a warp 

knit fabric or a polyethylene fiber. The fiber can be woven into a panel 

as thin as 0.029 inch that weighs less than 1.5 ounces per square foot. 

This fact dispels the myth that blast curtains are heavy sheets of lead that 

completely obstruct a window opening and eliminate all natural light 

from the interior of a protected building.

The main components of any blast curtain system are the curtains 

themselves, the mechanism by which the curtain is attached to the 

window frame, and either a trough or another retaining mechanism at 

the base of the window to hold the excess curtain material. Blast curtains, 

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 also vary, providing 

many options within the overall classification of blast curtains, which 

makes blast curtains applicable in many situations.

As shown in Figure 3-8, blast curtains differ from standard curtains in 

that they do not open and close in the typical manner. Blast curtains are 

designed to remain in a closed position at all times. The curtain may 

be pulled away from the window to allow for cleaning, blind or shade 

operation, or occupant egress in the case of fire. However, the curtains 

can be rendered ineffective if the building occupants do not use them 

Figure 3-8: Blast curtain 

system.
3-18 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

correctly by pulling them away from the glazing. The color and openness 

factor of the fabric contributes to the amount of light that is transmitted 

through the curtains and their transparency. While 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 relative to the window 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. 

3.4.5 Glazing Catch Cable/Bar Retrofit

As explained earlier, laminated and filmed glazing is designed to hold the 

glass shards together if the window is damaged. Unless the window frames 

and attachments are upgraded to withstand the capacity of the laminated 

glass, there is a high possibility that entire sheets of glass would fly free of 

the window frames in a blast environment. Rigid catch bar systems have 

been designed and tested as a means of increasing the effectiveness of 

laminated window upgrades. The rigid catch bars intercept the laminated 

glass and disrupt their flight (see Figure 3-9).

Rigid catch systems collect huge forces upon impact and require 

substantial anchorage into a very substantial structure to prevent failure. 

If either the attachments or the supporting structure are incapable of 

restraining the forces, the catch system will be dislodged and become part 

of the debris. Alternatively, the debris may be sliced by the rigid impact, 

severely limiting the effectiveness of the catch bars.

Flexible catch bars can be designed to absorb a significant amount of the 

energy upon impact, thereby keeping the debris intact and impeding 

Figure 3-9: Glazing catch bar.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-19

their flight into occupied spaces. They also may be designed to repel the 

debris from the failed glazing, as well as the walls in which the windows 

are mounted. The debris restraint system must be strong enough to 

withstand the momentum transferred upon impact, and the connections 

must be capable of transferring the forces to the supporting slabs and 

spandrel beams. Under no circumstances should the design of the 

restraint system add significant amounts of mass to the structure because 

it could be dislodged and present an even greater risk to the occupants of 

the building.

3.4.6 Energy-Absorbing Catch Cable 

Systems

The use of cable systems has long been recognized as an effective means 

of stopping massive objects moving at high velocity. Cables are extensively 

used to absorb significant amounts of energy upon impact, and their 

flexibility makes them easily adaptable to many situations. The diameter 

of the cable, the spacing of the strands, and the means of attachment 

are all critical in designing an effective catch system. These catch cable 

concepts have been used by protective design window manufacturers as 

restraints for laminated lites. An analytical simulation or a physical test is 

required to confirm the adequacy of the cable catch system to restrain the 

debris resulting from an explosive event. 

High-performance energy-absorbing cable catcher systems retain glass 

and frame fragments and limit the force transmitted to the supporting 

structure. These commercially available retrofit products consist of a 

series of 1⁄4-inch diameter stainless steel cables connected with a shockabsorbing device to an aluminum box section, which is attached to 

the jambs, the underside of the header, and topside of the sill. The 

energy-absorbing characteristics allow the catch systems to be attached 

to relatively weakly constructed walls without the need for additional 

costly structural reinforcement. To reduce the possibility of slicing 

the laminated glass, the cable may either be sheathed in a tube or an 

aluminum strip may be affixed to the glass directly behind the cable. 

3.4.7 Unreinforced Masonry Wall Debris 

Control

URM facade provides limited protection against air blast due to 

explosions. When subjected to overload from air blast, brittle 

unreinforced concrete masonry unit (CMU) walls will fail and the debris 

will be propelled into the interior of the structure, possibly causing 

severe injury or death to the occupants. Masonry debris may result from a 
3-20 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

100-pound TNT equivalent detonation within 300 feet or a 1,000-pound 

explosion within 1,000 feet and buildings may be subject to collateral 

damage due to an attack against a nearby building. Existing unreinforced 

CMU walls may be retrofitted with a sprayed-on polyurea coating to 

improve their air blast resistance. Polyurea materials are widely used as 

truck-bed liners and roof coatings; however, this innovative incremental 

rehabilitation technique takes advantage of their toughness and resiliency 

to effectively deform and dissipate the blast energy while containing the 

shattered wall fragments (see Figure 3-10). Although the sprayed walls 

may shatter in a blast event, the polyurea material remains intact and 

contains the debris. 

The blast mitigation retrofit for unreinforced CMU walls consists of an 

interior (and an optional exterior) layer of polyurea applied to exterior 

walls and lapped onto the adjacent floor and ceiling slabs. The polyurea 

provides a ductile and resilient membrane that catches and retains 

secondary fragments from the existing concrete block as it breaks apart 

in response to an air blast wave. The effectiveness of a spray-on polymer 

coating in controlling debris has been demonstrated through explosive 

testing at the Air Force Research Laboratory and by extensive numerical 

simulations. This retrofit is not applicable to load-bearing walls for which 

the preservation of structural integrity is required.

Instead of the spray-on polyurea, an aramid (geotextile) debris catching 

system may be attached to the structure by means of plates bolted through 

the floor and ceiling slabs (see Figure 3-11). Similar to the polyurea 

retrofit, the aramid layer does not strengthen the wall, but instead 

restrains the debris from being hurled into the occupied spaces in the 

case of an explosion.

Figure 3-10: Spray-on 

polyurea.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-21

A steel stud wall construction may also be used to limit debris associated 

with masonry wall failure (see Figure 3-12). Commercially available 18 

gauge steel studs may be attached web to web (back to back) and 16 

gauge sheet metal may be installed outboard of the steel studs behind 

Figure 3-11: Geotextile 

debris catch system.

Figure 3-12: Metal stud 

blast wall.
3-22 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

the cladding. While the wall absorbs a considerable amount of the 

blast energy through deformation, its connection to the surrounding 

structure must develop large tensile reaction forces. In order to prevent 

a premature failure, these connections should be able to develop the 

ultimate capacity of the stud in tension (FEMA, 2006a). The interior face 

of the stud should be finished with a steel-backed composite gypsum 

board product.

3.4.8 Other Facade Retrofits

In addition to upgrading the facade to minimize debris associated with 

failed glass, other retrofits might include the bracing of parapets, gables, 

ornamentation, and appendages that might be propelled into occupied 

space. Although these upgrades are more likely to be associated with 

increased resistance to seismic motions or hurricane force wind loads, 

they may also be warranted for buildings exposed to blast loading. 

Similarly, masonry veneer, steel stud back-up, and the exterior wythe 

of cavity walls may be upgraded to improve their resistance to extreme 

loads; however, these upgrades are relatively invasive and are rarely 

implemented to minimize the debris associated with blast loading. Due 

to the difficulty of improving the capacity of these building components, 

debris catch systems are typically installed instead of strengthening the 

components themselves. Although canopies at building entrances are 

vulnerable to an exterior explosion, they are outside of the building 

envelope and are rarely upgraded to improve their resistance to blast 

loading.

3.5 Nonstructural Members

Because of the likelihood of glass damage and the associated infill 

pressures, significant damage to nonstructural members in the 

exterior bays is likely. This damage will produce additional debris 

that may cause injuries and disrupt emergency mechanical systems, such 

as sprinkler systems, emergency lighting, and smoke exhaust systems. 

Consequently, critical nonstructural systems should be protected by means 

of improved support and lateral bracing. While it may not be feasible 

to upgrade mechanical systems without conducting a comprehensive 

interior renovation, there may be an opportunity to perform incremental 

rehabilitation as systems are renovated. Some nonstructural systems that 

may be considered for upgrade are: 

Sprinkler piping 

Emergency lighting 

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-23

Mechanical and electrical equipment above ceilings 

Masonry walls at interior stairs 

Hazardous materials container 

Transformers

Emergency generators

Boilers

Tanks

Chillers

3.6 Structural Retrofits

Unlike seismic upgrades of structural systems, which generally 

address the global lateral load resisting system, upgrade to 

resist blast loads are more local. Generally, measures that tie 

the structure together, that increase the redundancy and ductility of 

individual members and upgrades, and that transfer the lateral loads 

into the diaphragms improve the structure’s ability to resist blast loads. 

Since the capacity of members may be limited by the strength of the 

connections, upgrades must be comprehensive if they are to be effective. 

The incremental rehabilitation of the structure to accept the threat 

independent removal of any load-bearing member, as required by the 

alternate path method, is generally invasive and expensive. This typically 

requires the development of beam-to-column moment connections for 

steel frame construction and the installation of tension reinforcement 

through beam/column connections. Steel frame connections are 

often difficult to access and connection upgrades may be infeasible 

unless the structure is fully exposed. Similarly, the inclusion of tension 

reinforcement through concrete frame connections may be accomplished 

by grooving the existing concrete and bonding supplemental 

reinforcement with epoxy or the adhesion of a composite fiber 

reinforcement to the exterior of the members. 

In some cases, it may not be possible to retrofit an existing building to 

limit the extent of collapse to one floor on either side of a failed column. 

If the members are retrofitted to act as a catenary—the natural curve 

created by a flexible cord freely suspended between two fixed points—

the adjoining bays must be upgraded to resist the large lateral forces 

associated with this mode of response. The catenary behavior may be 

achieved through the application of a glass or carbon fiber material to 

the top and underside of the spandrel beams and slabs. Alternatively, 

❍

❍

❍

❍

❍

❍

❍

❍
3-24 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

steel plates may be through-bolted to the spandrel beams in order to 

develop continuity and axial capacity. However, developing the large 

lateral forces may require more extensive retrofit than is either feasible or 

desirable. In such a situation, it may be desirable to isolate the collapsed 

region rather than risk propagating the collapse to adjoining bays. 

This approach is best suited for arresting the horizontal progression 

of collapse in low structures with large floor plates. The creation of 

structural fuse planes prevents the lateral propagation of collapse. Vertical 

compartmentalization requires the structure resist the impact of debris 

from above without pancaking the floors below and this is more difficult 

to achieve. 

The incremental rehabilitation of existing structures to protect against a 

potential progressive collapse resulting from the detonation of a terrorist 

explosive may best be achieved through the localized hardening of 

vulnerable columns. These columns need only be upgraded to a level of 

resistance that balances the capacities of all adjacent structural elements. 

At greater blast intensities, the resulting damage would be extensive and 

termed global collapse rather than progressive collapse. 

Lightweight metal deck roof structures, without a concrete fill, are 

particularly susceptible to direct blast loading and suction associated with 

diffusion over the edge of the roof. Strengthening these roof systems 

may require extensive upgrades; however, the connections of the metal 

deck to the roof framing members and the roof framing members to 

the columns may also be upgraded to limit the extent of debris. While 

these systems may sustain significant damage in response to a sizeable 

vehicle-borne explosive threat, particularly for low buildings, improved 

connections protect occupants from falling debris hazards. Openings in 

walls and reentrant corners are not as critical for blasts as they are for 

multiple cycles of seismic base motions; however, they will create stress 

concentrations and must be developed with sufficient ductility to accept 

larger deformations. 

3.6.1 Columns

Conventionally designed columns may be vulnerable to the effects of 

explosives, particularly when placed in contact with their surface. Standoff 

elements such as partitions and enclosures may be designed to guarantee 

a minimum standoff distance; however, this alone may not be sufficient. 

A steel jacket or a carbon fiber wrap may be used to provide additional 

resistance to reinforced concrete structures (see Figure 3-13). These 

systems effectively confine the concrete core, increase the confined 

strength and shear capacity of the column, and hold the rubble together to 

permit it to continue carrying the axial loads. The capacity of steel flanged 
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-25

columns may be increased with a reinforced concrete encasement that adds 

mass to the steel section and protects the relatively thin flange sections. 

Alternatively, steel plate may be welded to flanged sections to create a box 

section that is more resistant to explosion. The details for these retrofits, 

and the corresponding connection upgrades, must be designed to resist the 

specific weight of the explosives and the standoff distance.

3.6.2 Floor Systems

Floor systems that span between column lines resist gravity loads and 

contribute to the lateral resistance of the building, either through frame 

action or as diaphragms that transfer lateral forces to braced frames or 

shear walls. Steel construction typically relies on concrete-filled metal 

decking that spans between closely spaced filler beams, which in turn span 

girders along the column lines. Steel beams and girders typically possess 

equal resistance to both upward and downward loading and are capable 

of developing large inelastic deformations; however, their ability to resist 

extreme loading is often limited by the capacity of their connections.

There is a greater variety of reinforced concrete floor systems, which may 

consist of beams and concrete slabs, beams and joists, waffle slabs, and 

flat slabs. Each of these systems optimizes the placement of reinforcement 

where they most efficiently resist the design loads; top reinforcement 

near the supports and bottom reinforcement at mid-span. Although 

the American Concrete Institute Building Code Requirements for Structural 

Figure 3-13: Steel jacket 

retrofit detail.
3-26 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

Concrete (ACI, 2005) requires additional continuous reinforcement for 

enhanced structural integrity, these nominal quantities do not resist the 

effects of direct blast loading and rebound. Furthermore, the effectiveness 

of the concrete sections to develop large inelastic deformations is 

governed by the confinement of the concrete within the steel cages. This 

confinement enhances both the ductility of the members and the ability 

to transfer shear forces across the cracked sections. Beam-to-column 

connections are often congested with vertical column reinforcement and 

horizontal beam reinforcements and are particularly vulnerable to blast 

loading. Confinement of the connection details, such as those used in the 

design of structures to resist seismic loading, is more likely to resist the 

effects of blast loading than conventional concrete detailing; however, the 

effectiveness of critical connection details must be confirmed through 

dynamic analysis. 

Flat slab structures do not rely on beams along edges to transfer loads 

to the columns; instead, they contain patterns of steel reinforcement 

within column strips and middle strips that develop the positive and 

negative moments that are imposed by the design loads. Because of the 

efficient use of materials, flat slab structures lack the redundancy of beamslab systems and are vulnerable to punching shear failures around the 

columns (see Figure 3-14). 

Floor slabs are typically designed to resist downward gravity loading and 

have limited capacity to resist uplift pressures or the upward deformations 

experienced during a load reversal (i.e., blast). Therefore, floor slabs 

that may be subjected to significant uplift pressures, which may overcome 

the gravity loads and subject the slabs to reversals in curvature, require 

tension reinforcement at the top fiber of the mid-span locations and 

bottom tension reinforcement at the underside near the supports (see 

Figure 3-15). The failure of floor slabs in response to explosive loading 

propels debris onto to the slab below and increases the unbraced 

length of the supporting columns. Both the pancaking of slabs and the 

destabilization of columns increases the potential for progressive collapse. 

The incremental rehabilitation of steel floor systems typically involves 

the welding of plates at the connections to increase their capacity. Often, 

the inaccessibility of the connections makes these upgrades difficult 

to achieve. The incremental rehabilitation of conventional concrete 

construction in order to increase confinement, improve ductility, and 

provide for load reversals relies on techniques that were developed for 

the seismic upgrade of structures. If the slab does not contain this tension 

reinforcement, it must be supplemented with a lightweight carbon 

fiber application that may be bonded to the surface at critical locations. 

Carbon fiber reinforcing mats bonded to the top surface of slabs would 

strengthen the floors for upward loading and reduce the likelihood of 
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-27

slab collapse from blast infill uplift pressures, as well as from internal 

explosions in mailrooms or other susceptible spaces. This lightweight 

high tensile strength material would supplement the limited capacity of 

the concrete to resist these unnatural loading conditions. Preliminary 

experience shows these retrofits to be effective. An alternative approach 

is to notch grooves into the top of the concrete slabs and then epoxy 

carbon fiber rods into those grooves. Although this approach may offer 

greater capacity, it is much more invasive and has not been evaluated with 

explosive testing.

Figure 3-14: Flat slab 

failure mechanisms.
3-28 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

3.6.3 Load-Bearing Unreinforced Masonry

Walls

URM load-bearing-wall buildings are prohibited by the Department of 

Defense Unified Facilities Criteria where blast resistance is required. 

These buildings may sustain severe damage when subjected to 100 

pounds of TNT-equivalent explosives at a standoff distance of 30 feet 

or 1,000 pounds of TNT-equivalent at a standoff distance of 150 feet. 

This makes the URM, load-bearing-wall buildings vulnerable to damage 

even when the structure is not the primary target of the attack. For this 

type of structure, it is not enough to just control the debris resulting 

from an explosive event; the structural integrity of the walls must be 

preserved to prevent structural collapse. Strengthening of the walls may 

be accomplished by means of a shotcrete sprayed onto the wall with a 

welded wire fabric. This method supplements the tensile capacity of the 

existing wall and limits the extent of debris that might be propelled into 

the protected space. Steel sections may also be installed against existing 

walls to reduce the span and provide an alternate load transfer to the 

floor diaphragms. Alternatively, stiffened steel-plate wall systems may be 

designed to withstand the effects of explosive loading by providing both 

redundancy and fragment protection. These load-bearing-wall retrofits 

require a more stringent design, capable of resisting lateral loads and the 

transfer of axial forces. Stiffened wall panels, consisting of a steel plate to 

catch the debris and welded tube sections spaced approximately 3 feet 

on center, supplement the gravity load-carrying capacity of the bearing 

walls and prevent the debris from entering the protected space. Finally, 

Figure 3-15: Effects 

of uplift and load 

reversal.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-29

internal strengthening of URM walls may be achieved using a system 

wherein cables are snaked through holes that are cored through the 

wall and anchored in place with an injected grout without disturbing the 

finishes. 

3.6.4 Transfer Girders

Key elements that may be exposed to the explosive threat, such as transfer 

girders and mega-columns, warrant the most immediate attention to 

incremental rehabilitation. The risk assessment will identify the most 

critical members and the priority for hardening. If structural upgrades 

such as concrete encasement or steel jacketing are not feasible, then 

vulnerability of key elements may be reduced by means of architectural 

enclosures that provide increased standoff distance. Small increases 

in standoff distance greatly reduce the intensity of the near-contact 

blast loading and increase the survivability of structural members. If 

the architecture permits, this approach is both inexpensive and highly 

effective; however, advanced analysis may be required to demonstrate the 

performance of the structural members in response to the reduced load 

intensity. These key components should also be upgraded to increase 

the resistance of fireproofing in response to blasts to account for a wider 

range of potential threats and hazards. If the connections of vulnerable 

steel-braced and moment-frame members are accessible, they may be 

upgraded to develop the plastic capacity.

3.7 Blast Protection Measures 

T he preceding discussions of blast threat mitigation measures 

(Sections 3.3–3.6) can be condensed into the following list. 

It is presented here as an example of measures that might be 

generated by the FEMA 452 process and implemented using FEMA 459, 

as discussed in Chapter 2. These measures are all included in the list that 

comprises the vertical axes of the matrices in Section 2.3.

Site upgrades 

Increased standoff distance

Anti-ram barriers

Speed calming devices

Operable barriers

❍

❍

❍

❍
3-30 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS

Building envelope upgrades

Glazing

Fragment retention film

Laminated glass

Blast curtains

Glazing catch cable/bar

Energy-absorbing cable systems

URM

Sprayed-on polymer

Geotextile fabric

Steel stud and sheetmetal construction

Other building envelope retrofits 

Bracing parapets, gables, ornamentation, and appendages

Anchoring cladding 

Anchoring masonry veneer

Anchoring steel stud backup

Anchoring exterior wythe in cavity walls

Installing debris catch systems for facade elements

Increasing the roof’s resistance to blast

Upgrading connections of light metal deck roofs to the 

structure

Structural upgrades

Upgrading the structure to make it more ductile

Upgrading spandrel beams to achieve catenary response

Upgrading slabs to achieve catenary response

Increasing standoff distance around vulnerable columns

Localized hardening of vulnerable columns

Enhancing floor slab upload resistance

Installing load-bearing URM retrofits 

Shotcrete

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO BLASTS 3-31

Steel sections

Stiffened steel-plate wall system

Reinforcing

Retrofitting transfer girders

Nonstructural upgrades

Sprinkler piping

Emergency lighting

Mechanical and electrical equipment above ceilings

Masonry walls at interior stairs

Restraint of hazardous materials containers

Transformers

Emergency generators

Boilers

Tanks

Chillers

3.8 Blast Protection Measure Cost 

Considerations

T he major costs to consider in protection are those associated with 

standoff distance and building component costs. Cost reduction 

achieved by decreasing standoff and perimeter length must be 

evaluated against the comparative increased cost of other solutions, such 

as hardening the building, providing more guards, increasing camera 

surveillance, relocating the facility, or relocating key building occupants 

to interior locations. These costs must be evaluated with respect to 

achieving an acceptable level of risk. 

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-1

4

PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO 

CHEMICAL, BIOLOGICAL, AND RADIOLOGICAL THREATS

Recent terrorist events have increased interest in the vulnerability 

of buildings to CBR threats. Of particular concern are building 

HVAC systems, because they can become an entry point and 

distribution system for airborne hazardous contaminants. Even without 

special protective systems, buildings can provide protection in varying 

degrees against airborne hazards that originate outdoors. Conversely, the 

hazards produced by a release inside a building can be much more severe 

than a similar release outdoors. Because buildings allow only a limited 

exchange of air between indoors and outdoors, not only can higher 

concentrations occur when there is a release inside, but hazards may 

persist longer indoors. 

The results of the FEMA 452 risk assessment, including the vulnerability 

checklist, will likely yield many opportunities to reduce risk over time by 

upgrading the building’s HVAC and other systems. This chapter describes 

the nature of the CBR threat and some of the opportunities for risk 

reduction. 

4.1 Overview of CBR Threats

T here are hundreds of toxic chemical, biological, and radiological 

agents that could be released in an accident or terrorist attack. 

Among them are chemical-warfare agents, industrial chemicals, 

radioactive materials, toxins, irritants, incapacitants, and biological agents, 

which are mainly bacteria, viruses, and rickettsiae. The potential hazard 

each agent presents is determined by its toxicity, persistence, and quantity. 

Toxicity among these agents varies over several orders of magnitude. 

Toxicity and likely quantity of exposure determine the level of protection 

needed for protective systems. Toxic agents also vary widely in persistence. 

Gases such as chlorine are non-persistent and usually dissipate in 

minutes outdoors. Radiological agents and some of the biological 

agents are extremely persistent and may remain toxic in an indoor or 

outdoor environment for decades unless decontamination measures are 

undertaken. 

Toxicity and persistence determine the extent and duration of a hazard, 

but the more important characteristics relative to protective strategies are 
4-2 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

how readily the agents can be filtered and detected. Filtration involves the 

removal of a toxic agent from an air stream. The full spectrum of toxic 

agents includes gases, vapors, and aerosols (finely divided particles). With 

current technology, filtering the full spectrum of toxic agents requires 

three different processes—mechanical filtration for aerosols, physical 

adsorption for chemical agents of low vapor pressure, and chemisorption 

for chemical agents of high vapor pressure. The latter two are usually 

incorporated into a single filter called an adsorber. 

With regard to detection, most of the toxic chemicals have warning 

properties; that is, they can be detected by the human senses—by smell, 

irritation of the eyes/respiratory tract, color, and in some cases by taste—

before severe effects occur. There are no warning properties associated 

with airborne microbial pathogens or radioactive aerosols.

Most toxic chemicals produce immediate effects. Automatic detectors are 

available for the accurate detection of a few of the most toxic chemicals. 

Single-pass filtration systems of the high level of efficiency necessary for 

protection against toxic chemicals are generally expensive and cannot 

filter all toxic chemicals.

Biological agents are neither perceptible by the senses nor detectable in 

real time by automatic detectors. Their effects are delayed. The particle 

size range of concern for biological aerosols is 1 to 5 microns, and the 

very high filter efficiencies necessary for these aerosols can be achieved 

with HEPA filtration.

Similarly, radiological agents are not perceptible by human senses and 

their effects are delayed. However, they can be detected in real time and 

are easier to decontaminate from indoor spaces than biological agents. 

They can be filtered at very high efficiencies with HEPA filters. 

4.2 Principles of Design for Risk 

Reduction Related to CBR

For a building owner or manager, reducing CBR risk means 

reducing the CBR vulnerability of the building. There are several 

options for doing so that vary in effectiveness and cost. The most 

effective measures are those that are preventive and protective.

Preventive measures are those intended to prevent the release of a toxic 

agent in or into a building. Protective measures are those that impose 

barriers and high-efficiency filter systems between people and spaces that 
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-3

are or may become contaminated. A building may be considered as a 

system of barriers. Protective measures can be achieved by improving the 

building’s filtration system, making the barrier system more complete, 

and applying pressures with fans to overcome the natural pressures of 

wind and buoyancy acting on air leakage paths.

There are two types of protective measures: passive (continuously 

protective) and active (initiated upon determining that a hazard exists or 

is imminent).

The nature of the CBR threat to a specific facility determines the strategy 

for applying preventive and protective measures. A building for which 

the threat, vulnerability, and asset value/consequence are considered 

high requires a high level of protection. If the combination of threat, 

vulnerability, and asset value/consequence is low, a low level of protection 

is appropriate. If the primary threat is an indoor or air-intake release, 

the greatest benefit is derived from physical security enhancements. 

Enhanced filtration of recirculated air is also beneficial. If the primary 

threat is an outdoor release, enhanced filtration of the ventilation air 

and/or enhanced safe rooms are most beneficial for reducing risk.

4.3 Prioritization of CBR 

Vulnerabilities: Incremental

Improvements

T here are several improvements that can protect building occupants 

from a CBR release or prevent a release from occurring inside or 

directly into a building. However, not all measures are effective 

against all types of agents and against all delivery methods. Systems 

involving air-filtration and pressurization are the most effective, and they 

provide secondary, but significant, benefits of better indoor air quality. 

They are also most expensive in terms of initial cost, operating cost, and 

maintenance cost.

There are seven distinct levels of CBR protection for buildings. These 

levels are listed below in general order of cost. Each succeeding level 

involves increased cost and provides greater protection for occupants 

and the building. Each level provides additional protection to the one 

preceding it, if the threat, vulnerability, and criticality so indicate. Seven 

options for CBR Protection include:

1. Operational measures and expedient protection

2. Enhanced physical security 

3. Enhanced sheltering in place 
4-4 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

4. Aerosol filtration, medium level 

5. Gas-phase filtration, medium level 

6. Aerosol filtration, high level 

7. Gas-phase filtration, high level 

4.3.1 Level 1, Operational Measures and

Expedient Protection

Level 1 consists of basic, low-cost preparations for reducing the effects of 

a CBR attack. These are primarily operational measures and require no 

modifications to the building or special equipment. These operational 

measures involve developing procedures (active measures) for responding 

to a release of toxic agent, including:

Expedient sheltering in place

Designating safe rooms: interior rooms with a low air exchange 

rate

Identifying switches for air handling units and fans for 

deactivation

Defining procedures and responsibilities for sheltering and for 

purging the building after plume passage 

Establishing a building-wide notification system

Familiarizing building occupants with procedures and 

responsibilities

Evacuation

Purging

Using escape respirators

4.3.2 Level 2, Enhanced Physical Security

Level 2 measures focus on preventing the internal or air-intake release 

of agents. Incorporating building modifications or installing security 

equipment may include:

Securing air intakes, mechanical rooms, and HVAC plenums against 

unauthorized access

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-5

Performing entry inspections

Installing and monitoring video surveillance equipment

Instituting mail screening procedures

Maintaining operational security to building plans and signage

Applying mechanical and architectural isolation of lobby, mailroom, 

cloakroom, and loading docks

4.3.3 Level 3, Enhanced Sheltering in Place

Level 3 includes modifications to the building to make emergency 

protective actions more effective and to isolate zones in which indoor 

releases are most likely to occur. Modifications include:

Installing single-switch control of fans for sheltering and purging

Sealing the envelope of the building and selected safe room(s)

Installing automatic dampers for outside air intakes and exhaust fans

Implementing a public address system to achieve rapid 

implementation of emergency actions

Isolating mechanical spaces that require large volumes of outside air 

by mechanical and architectural means

Installing separate fans and air streams for ventilation and 

recirculation, as well as cooling and heating of safe rooms

Installing recirculation filter units in safe rooms

4.3.4 Level 4, Aerosol Filtration, Medium

Level

Level 4 is the first of four levels involving improved air filtration. It is 

the least costly of the four levels of filtration and includes only aerosol 

filtration and the use of existing air-handling units that filter mixed 

air (both ventilation air and return air) with the same filters. Aerosol 

filtration provides protection against biological agents, radiological 

agents, and most irritants. Level 4 may be applied to selected zones 

only or to the entire building (with the exception of mechanical spaces 

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
4-6 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

requiring large volumes of outdoor air). It provides benefits against both 

outdoor and indoor releases and requires:

Sealing filter frames to minimize bypass

Installing filters of greater depth/surface area and higher Minimum 

Efficiency Rating Value (MERV) rating, such as MERV 14, 15, or 16 

mini-pleats

Operating at outdoor air fractions that produce positive internal 

pressures of approximately 0.1 to 0.2 inch, water gauge

4.3.5 Level 5, Gas-Phase Filtration, Medium

Level

Level 5 expands filtration capability in air handling units to include gas 

adsorbers, which are the filters needed to remove chemical vapors and 

gases. Using indoor-air-quality type adsorption systems that have relatively 

low pressure drops produces initial removal efficiencies of about 99 

percent for physically adsorbed (low vapor pressure) agents and provides 

about 1 year service life. Filtration of chemicals of high vapor pressure is 

poor. This type of filtration may be applied to the entire building (except 

for mechanical spaces requiring large volumes of outdoor air) or to 

selected zones. It provides protective benefits against both outdoor and 

indoor releases and requires:

Indoor-air-quality type, low resistance adsorbers that may necessitate 

substantial modification to air handling units

Operating at outdoor air fractions that produce positive internal 

pressures of approximately 0.1 to 0.2 inch, water gauge

Vestibules or revolving doors for highly protected zones

4.3.6 Level 6, Aerosol Filtration, High

Level

Level 6 increases the level of protection against an outdoor release of 

toxic aerosols substantially over Level 4, but it does not provide any 

benefits over Level 4 against an indoor release. Level 6 requires the 

installation of makeup-air/ventilation units with HEPA filters. This may be 

applied to the entire building or selected zones. It involves:

❍

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-7

Installing ventilation/makeup-air units with HEPA filtration for each 

zone to be protected

Vestibules or revolving doors for highly protected zones

Operating at outdoor air fractions that produce positive internal 

pressures of approximately 0.1 to 0.2 inch, water gauge

4.3.7 Level 7, Gas-Phase Filtration, High

Level

Level 7 involves the installation of high-efficiency gas adsorbers in 

ventilation/makeup air units serving protected zones. It expands the 

protective capability to toxic gases and vapors in addition to the aerosol 

capability of Level 6. Its cost is relatively high, and costs vary with the 

tightness of the envelope being pressurized. It provides the highest, 

most complete level of protection against an outdoor release and may be 

applied to the entire building or selected zones. It involves:

Installing ventilation/makeup air units with high efficiency gas 

adsorbers as well as HEPA filters for each zone protected

Vestibules and revolving doors for the protected zones

Operating at outdoor air fractions that produce positive internal 

pressures of approximately 0.1 to 0.2 inch, water gauge.

4.4 Design Guidance for CBR 

Protective Levels

T he following sections contain detailed descriptions and discussions 

of the seven levels summarized above.

4.4.1 Level 1, Operational Measures and

Expedient Protection

4.4.1.1 Scope and Capabilities

This basic level of protection is achieved by preparing emergency plans 

and procedures, then familiarizing building occupants with these plans 

❍

❍

❍

❍

❍

❍
4-8 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

and procedures for responding to a 

toxic-agent release. These plans and 

procedures cover:

Expedient sheltering in place

Purging

Evacuating

Using escape respirators

Each of these is an active measure; 

that is, it is initiated only when a 

hazard is present or known to be 

imminent. Active measures are most 

practical against chemical agents 

because chemical agents can be 

immediately detected, either by their 

warning properties (particularly odor), automatic detectors, or visible/

audible signs of a release. Biological agents are not detectable in real 

time; therefore, these measures are not expected to apply for biological 

agents unless there is forewarning of some kind provided by those who 

are releasing, transporting, or storing the agent.

Sheltering in place is employed mainly for outdoor releases, evacuation 

mainly for indoor releases, and escape respirators for either indoor or 

outdoor releases.

4.4.1.2 Methods and Requirements

Sheltering in Place

Some content addressing protective actions in this section was originally 

published in Protecting Buildings and their Occupants from Airborne Hazards,

U.S. Army Corps of Engineers, October 2001.

For maximum protection, sheltering in place requires two actions to 

temporarily change a building’s indoor-outdoor air exchange rate. The 

first is to reduce the air-exchange rate before contaminated air begins 

to enter the building. This involves shutting off all fans that promote the 

exchange of air between indoors and outdoors, closing all exterior doors 

and windows, and shutting off elevators. 

❍

❍

❍

❍

Summary of Capabilities for Level 1

Sheltering in place provides a low level of protection 

from chemical agents released outdoors. 

Evacuation and purging (when the nature of the 

release is known) provide low-level protection in 

response to indoor releases. 

Operational measures and expedient protection 

are not generally practical for biological agents

because biological agents cannot be detected in real 

time. 

Operational measures and expedient protection 

also apply to radiological agents, but automatic 

detectors (e.g., radiac meters) are likely to be 

necessary.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-9

The second action is to increase the air-exchange rate after the outdoor 

hazard has dissipated. This is necessary because even a tightly sealed 

building will not fully prevent contaminated air from entering. However, 

outdoor air will enter more slowly, and once the external hazard has 

passed, the building will release the contaminated air slowly

The advantage of sheltering in place is that it can be implemented rapidly. 

The disadvantage is that its protection is variable and diminishes with the 

duration of the hazard. The amount of protection varies with the building 

air exchange rate, the duration of exposure, and the period of occupancy 

after the hazardous condition has passed. 

Sheltering can be employed as a precautionary measure if there is an 

impending release (e.g., a tanker truck crash involving a fire that releases 

toxic material, a non-windward release when winds shift, or a release at 

a great distance from the building). Sheltering is not appropriate for 

protecting people when the duration of exposure to an outdoor hazard is 

long and continuous, i.e., for several hours. 

The need to shelter in place may be indicated by (1) visible or audible 

signs of release of agent, (2) information from authorities that there has 

been a release in the area, (3) observed symptoms of chemical-agent 

exposure in people outside the building, or (4) automatic detectors, if 

available, sampling air outside the building or outside air as it is drawn 

into the building.

One option for sheltering is to use designated rooms or safe rooms, if 

they are better sealed than the building as a whole and/or the location 

of the room is less subject to wind pressures or buoyancy pressures that 

induce infiltration. Safe rooms may also be located in the building on 

the side opposite a likely source (e.g., a nearby chemical storage facility 

or railroad line). The safe rooms must be of a number and capacity to 

accommodate all building occupants and visitors. Generally, safe rooms 

require a minimum of 5 square feet per person, with 10 square feet per 

person preferred.

Using a sealed interior room within a sealed building provides greater 

protection than a sealed building by itself. A sealed interior room has 

greater resistance to infiltration flow driven by wind and buoyancy. 

However, use of designated safe rooms is not essential. In many cases, 

office buildings do not have sufficient space in interior rooms for 

sheltering all building occupants. 

To be effective in large commercial buildings, sheltering in place requires 

planning and preparation. All exterior doors must be secured and all 
4-10 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

air handling units and exhaust fans must be turned off. Procedures for a 

sheltering plan, therefore, should include:

Identifying all air handling units, fans, and the switches needed to 

deactivate them

Identifying procedures for purging if an indoor release occurs, such as 

opening doors and windows; turning on smoke fans, air handlers, and 

exhaust fans that were turned off to shelter; and setting air-handlers 

on maximum outdoor air

Designating safe rooms (see Figure 4-1), interior rooms having a lower 

air exchange rate that may provide a higher level of passive protection 

Establishing a building-wide notification system

Familiarizing occupants with the procedures and responsibilities for 

sheltering in place 

Although sheltering is for protection against an external release, 

sheltering in place on one or more floors of a multi-story building after 

an internal release has occurred on a single floor is also possible, though 

more complex. Under such conditions, stairwells must be isolated by 

closed fire doors, elevators must not be used, and clear evacuation 

routes must remain open in case evacuation becomes necessary. Escape 

respirators may be needed if the only evacuation routes are through 

contaminated areas.

Purging

Emergency actions for purging a building and reducing occupants’ 

exposure include turning on a building’s ventilation fans and smokepurge fans and increasing air-handling units’ outdoor air fraction 

to nominal 100 percent. Purging is useful primarily when the agent 

is known, the source of the agent is indoors, and as the final step in 

sheltering in place. The ventilation system and smoke purge fans can 

also be used to purge the building after an outdoor hazard has dissipated 

and it has been confirmed that the agent is no longer present near the 

building.

The location of the source and the time of the release should be 

carefully considered when purging. The source of agent must be inside 

the building; if not, purging should not be attempted. If the hazardous 

material has been identified before release or immediately upon release, 

purging should not be employed, as it may spread the hazardous material 

❍

❍

❍

❍

❍

Figure 4-1: Signage 

designating safe room.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-11

throughout the building or zone. In this case, all air-handling units 

should be turned off to isolate the hazard while evacuating or temporarily 

sheltering in place. 

Evacuating

Evacuating is the most common protective action when there is an 

airborne hazard in a building. In most cases, existing plans for fire 

evacuation apply. Though evacuating is the simplest and most reliable 

action, it may not be the best action for an outdoor release, particularly 

one that is widespread. Determining whether the source of the agent 

is indoors or outdoors is an important consideration in a non-fire 

evacuation.

If the source is outdoors, and the agent has infiltrated the building, 

evacuation is not the safest action (unless the source has dissipated), 

and the use of respirators is appropriate. Sheltering in place may also be 

employed, but generally should not be used once the hazardous material 

has entered the building. Evacuation routes may also be hazardous if they 

take people through contaminated areas as they leave the building.

Alternate routes that do not pass through the main lobby are best. For 

multi-story buildings, the elevators should be avoided because elevator 

movement promotes the exchange of air between and among floors. 

Assembly points should be designated outside the building so people can 

be accounted for or be given additional instructions.

Using Escape Respirators

Several models of universal-fit escape respirators have been developed for 

short-duration escape-only protection against chemical-warfare agents, 

aerosols (including biological agents), and some of the toxic industrial 

chemicals (see Figure 4-2). The National Institute for Occupational Safety 

and Health has a certification process for such respirators. Most of these 

respirators have their protective seals at the neck, rather than around 

the face, and consequently do not require special fitting techniques or 

multiple sizes to fit a large portion of the adult population. Training 

is required to use the masks properly. Depending on mask design, the 

wearer breathes through a mouth bit or uses straps to tighten a nose cup 

around the nose and mouth. 

The protective capability and shelf life of these masks vary with the design. 

The filter units of the masks contain both HEPA filters and packed carbon 

adsorbers, so they will remove chemical and biological aerosols, as well 
4-12 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

as chemical vapors and gases. Although the carbon filters are designed 

to filter a broad range of toxic chemicals, they cannot filter all chemicals. 

For example, the filters of escape masks are not effective against some 

chemicals of high vapor pressure. Unless they have a special filter, they 

provide no protection against the carbon monoxide that is produced in 

fires. Other escape hoods are available that employ compressed oxygen 

cylinders, rather than air filters, to provide eye and respiratory protection 

for short periods that vary with the intensity of the activity (i.e., walking, 

sitting, and climbing/descending stairs). 

Plans for training, fitting, storing, and record retention procedures 

should be established for escape masks and respirators. 

Figure 4-2: Escape 

respirators.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-13

4.4.1.3 Cost Considerations

Costs of Expedient Sheltering In Place

The initial costs of establishing a basic sheltering-in-place capability are 

small where space is available. These costs are associated with: 

Conducting a survey to identify safe rooms

Defining, printing, and distributing the sheltering procedures and 

familiarizing the building occupants with these procedures

Assigning responsibilities for: closing doors, turning building fans off/

on, and acting as safe room monitors in an emergency 

Creating signage designating the safe room and providing instructions 

for the occupants 

Keeping a supply of bottled drinking water in each safe room 

Operating and maintenance costs are those associated with periodic 

training and exercises, such as an annual sheltering drill, and 

replenishing supplies in the safe rooms.

Costs of Escape Respirators

The initial costs of employing escape respirators that meet requirements 

developed by the U.S. Army and/or the National Institute of 

Occupational Safety and Health include: 

Purchasing respirators (approximate unit cost ranges from $100 to 

$300). This may include the purchase of respirators for visitors and 

new employees. 

Initial training in use of the respirators.

Establishing an inventory system for the respirators that addresses 

serviceability checks and shelf life.

The operating and maintenance costs of escape respirators include: 

Replacement costs for respirators or respirator filters. Air-purifying 

type respirators require replacement every 4 to 5 years. Self-contained 

breathing apparatuses have a shelf life of 10 years.

❍

❍

❍

❍

❍

❍

❍

❍

❍
4-14 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

Maintaining an inventory system, conducting refresher training, 

reissuing serviceable unused respirators, and ordering and issuing 

replacement respirators or filters. Cost data from one Federal facility 

show this cost to be roughly 10 percent of the respirator costs per year. 

4.4.2 Level 2, Physical Security

4.4.2.1 Scope and Capabilities

The purpose of the physical security 

measures applied in this level is to prevent 

the release of an agent from a point inside 

the building or through a penetration in 

the building shell from a point near the 

building. 

These physical security measures, which 

also provide benefit against other criminal 

acts, include five measures as described in 

4.4.2.2 below.

Physical security measures are preventive 

measures; they serve to deter potential attackers and to prevent the 

release of agent in or into the building. They are effective only within the 

building and/or its secure perimeter; they apply to indoor releases and 

outdoor releases near the building. 

Among the security measures presented below, only the entry inspection 

requires the capability to detect toxic agents. Because of technical 

challenges in detecting and reliably identifying agents, entry inspection 

is most practical for chemical agents and least practical for biological 

agents.

4.4.2.2 Methods and Requirements

Securing Air Intakes

Securing air intakes is the highest priority physical security measure 

(see Figure 4-3). There are, however, several degrees of vulnerability 

for air intakes. Generally, the more difficult an intake is to access for 

surreptitious insertion of a toxic agent, the lower its vulnerability. 

Elevating intakes is the best approach to decreasing vulnerability. In 

retrofit, however, doing so can be expensive and require architectural 

❍

Summary of Capabilities for Level 2 

Level 2 consists of physical security measures, 

preventive or deterrent measures that apply to 

indoor releases or outdoor releases close to the 

building.

These measures apply to all toxic agents—

chemical, biological, and radiological 

agents—although detectability makes them 

most practical for chemical agents.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-15

changes that may not be aesthetically acceptable. There are less 

expensive, less effective measures that can be taken to reduce intake 

vulnerability, such as installation of security fencing and surveillance 

cameras. Whether an intake should be secured depends on its 

vulnerability and the level of threat to the building. 

Securing Mechanical Rooms and HVAC Plenums

Securing mechanical rooms is a relatively inexpensive means of denying 

access to the HVAC system (except for the outside air intakes). Unsecured 

mechanical rooms present a vulnerability similar to but lower than 

unsecured outside air intakes. In most cases, mechanical rooms are 

accessed from inside the building; therefore, the routes of access are 

subject to the physical security of the building.

HVAC ceiling plenums present an accessible pathway to the air-handling 

units, in which a dissemination device could be concealed by lifting a 

drop-ceiling tile. Plenum return pathways are not present in buildings 

with ducted returns and cannot be secured in buildings with hallway 

returns. Securing the ceiling plenum is impractical in most applications 

because access to the ceiling plenum must be retained for maintenance 

purposes.

Figure 4-3: Typical air 

intakes.
4-16 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

Performing Entry Inspections

Adding entry inspections to prevent containers of toxic agents from being 

brought into a building is practical only if security guards control access to 

the building. Entry inspections have varying degrees of effectiveness. They 

can be effective for both deterrence and detection. Detecting toxic agents 

in containers is difficult, however, as there is no practical technology for 

rapid, non-intrusive detection/identification of toxic agents. Current 

methods of detection are based on the type of container (e.g., pepper 

spray devices) or on quantities of specific chemicals detected on exposed 

surfaces.

Performing entry inspections in a lobby that is isolated architecturally and 

mechanically from the rest of the building is best. Such isolation should 

involve measures described in 4.4.3.2. In some cases, performing entry 

screening in a separate building (i.e., a visitors center) is more efficient 

and effective than modifying a lobby for isolation. Similarly, it may cost 

less to receive, inspect, and sort mail and packages in a separate building. 

Employing Video Surveillance

The principles of deterrence and detection are also applied in the use of 

video surveillance equipment. For detection to be effective in preventing 

or mitigating the effects of a release, images from the cameras must be 

monitored continuously in real time. For deterrence, the surveillance 

must be overt rather than covert. Because of privacy concerns, overt 

surveillance is most commonly employed in office buildings. 

Generally, surveillance cameras should be placed in common areas that 

are not within the normal view of security personnel. Indoors, these 

areas may include hallways, cloakrooms, and obscure parts of the lobby. 

Outdoors, suitable placement may include unsecured air intakes and 

areas where vehicles or pedestrians may release an agent that would be 

transported into the building.

Other Security Considerations

Building plans may contain information relevant to CBR vulnerabilities. 

For this reason, access to drawings and specifications should be restricted. 
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-17

4.4.2.3 Cost Considerations

The cost of installing security equipment varies substantially with the 

number of surveillance cameras, resolution and features of cameras, and 

monitors and recording equipment.

4.4.3 Level 3, Enhanced Safe Rooms and

Isolated Zones

4.4.3.1 Scope and Capabilities

Level 3 CBR protection involves 

increased protection against 

indoor releases. This level includes 

architectural and mechanical 

modifications to designated safe 

room(s) to increase the protection 

the safe room can provide, and 

to zones of concern, such as the 

mailroom and lobby, to isolate 

them from the rest of the building. 

The mailroom is a primary zone of 

concern, and the lobby is a zone 

of concern for access-controlled 

buildings. Isolating zones of concern 

is a passive measure that prevents the 

transport of airborne agents to other spaces of the building.

4.4.3.2 Methods

Safe Room Enhancements

There are three classes of safe room, as defined by U.S. Army documents 

on CBR collective protection (USACE, 2001). These classes provide three 

levels of protection, with Class I being the most protective.

Class I safe rooms are ventilated and pressurized by air filtered at high 

efficiency. 

Class II safe rooms have air filtration with either no ventilation or a 

ventilation rate that produces little or no overpressure. 

Summary of Capabilities for Level 3 

Level 3 mitigates indoor releases. It applies to 

all types of agents: chemical, biological, and 

radiological. 

These measures prevent an agent released in a lobby 

or mailroom from migrating to other parts of the 

building and require access control and some level 

of entry screening.

For enhanced sheltering in place, the protective 

capabilities described in level 1 apply.
4-18 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

Class III safe rooms are unventilated and have no air-filtration equipment. 

These safe rooms apply what is commonly referred to as sheltering in 

place.

The features listed below facilitate rapid transition to sheltering mode 

and improve the level of protection a CBR safe room provides. These 

apply mainly to Class II and III safe rooms, but some apply to Class I. The 

design of Class I (pressurized) safe rooms is covered under Level 7. 

For commercial buildings, these enhancements are as follows:

Single-switch, rapid-shutdown capability for all fans that induce 

indoor-outdoor air exchange (See Figure 4-4). This includes shutdown 

capability for ventilation fans, exhaust fans, and air-handling units that 

draw outside air. 

Sealing measures. The level of protection varies with the tightness of 

the building in its sheltering configuration; the lower the air exchange 

rate, the higher the level of protection. 

A public-address system to rapidly instruct all people in the building to 

shelter in place (i.e., not to exit the building or open exterior doors). 

A broadcast voice system is preferable to a tone-alert, ring-down, or 

computer-screen message system because it is the most rapid and 

reliable. 

Dampers for outside air intakes and exhaust fans. Dampers should 

be automatic and interlocked with the fan operation and must be 

maintained in good working order. 

❍

❍

❍

❍

Figure 4-4: A single 

switch for stopping 

HVAC fans.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-19

Typical dampers are not effective enough to allow heating and air 

conditioning in the safe room while in the sheltering mode. Safe use of 

an air-handling unit serving a CBR safe room requires a recirculation fan 

separate from the makeup air fan. Cooling or heating in the safe room in 

the sheltering mode can be safely accomplished with separate ventilation 

and recirculation fans, when the damper for the ventilation fan is closed. 

A system with separate fans eliminates the potential for internally induced 

infiltration that typically occurs with an air-handling unit (single fan and 

damper) in the full recirculation mode. 

Filtering recirculated air in a safe room increases the protection level of 

the safe room from Class III to Class II. Some recirculation filter units 

have substantial adsorbers as well as high-efficiency particulate air filters 

and are suitable for enhanced sheltering in place (See Figure 4-5). To 

improve the safe room’s protection against chemical agents, the filter 

unit must have a substantial gas adsorber. The adsorber removes most 

chemical agents, while the high-efficiency particulate filter, found in most 

recirculation filter units, removes biological agents and other aerosols 

such as radioactive dust, tear gas, and pepper spray. While recirculation 

filters have the capability of removing biological agents, it is unlikely that 

the safe room would be used in the case of a biological release due to 

limitations in detection capability for biological agents.

Figure 4-5: Two 

recirculation filter units.
4-20 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

Isolating the Lobby and Mail Room

The lobby and mailroom are two spaces in an office building in which a 

toxic agent release would be most likely to occur. Isolating these spaces 

architecturally and mechanically reduces the probability that large 

portions of the building will become contaminated by an indoor release. 

The probability of a lobby release is higher if the building is accesscontrolled and the lobby is open to the public. 

Isolating these spaces from the rest of the building may require both 

architectural and mechanical changes, including: 

Full-height walls 

A dedicated air handling unit (serving only the space) if an all-air 

HVAC system is used

An exhaust fan or system balancing to maintaining the space at a 

negative pressure relative to the rest of the building 

Doors into and out of the lobby that are normally closed (The 

frequency of entries and exits determines whether vestibules or 

revolving doors are also required.)

4.4.3.3 Cost Considerations

Initial costs vary widely, as lobbies generally require architectural changes 

to place a barrier and doorway between the lobby and adjoining spaces. 

Mechanical changes would require a separate air-handling unit for the 

space. 

4.4.4 Level 4, Aerosol Filtration, Medium

Level

4.4.4.1 Scope and Capabilities

This is the first of four levels involving improved air filtration. Among 

the four, it is the simplest to apply and requires the least cost and space. 

Any improved air filtration requires a licensed mechanical contractor to 

ensure effective installation and prevent adverse effects on ventilation 

rates and HVAC system operation.

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-21

Level 4 involves aerosol filtration only 

in the existing air-handling units and 

provides a medium level of protection 

because the filters are less efficient than 

HEPA filters. Also, existing air-handling 

units typically allow substantial volumes of 

air to bypass the filters. This bypass occurs 

not only at the filter-holding frames but 

also at leakage paths in the air-handling 

unit cabinet under negative pressure.

4.4.4.2 Methods and 

Requirements

This increased level of protection for 

aerosols requires:

Installing filters of higher MERV within available space and within 

resistance limitations of the air-handling unit fan. This is most easily 

accomplished by installing filters of mini-pleat configuration having 

greater filter depth and therefore, greater surface area.

Sealing filters to their retaining frames to minimize bypass, and sealing 

leakage paths on the air-handling unit cabinet between the filter 

frames and the fan.

Operating at outdoor air fractions that produce a positive internal 

pressure in the building. 

The details of sealing frames vary from installation to installation. 

Generally, front-access filters provide much better potential for reducing 

bypass than do side-access filters, although there are side-access 

housings available with locking mechanisms to ensure a good filter seal. 

Pressurization levels are the same as those discussed for Levels 6 and 7.

4.4.4.3 Cost Considerations

The costs of modifications to the filter holding frames vary with the type 

and condition of the air-handling unit. 

Additional resistance to flow in terms of pressure drop may result in 

increased operating costs, which are likely to be offset by additional service 

life resulting from greater surface area.

❍

❍

❍

Summary of Capabilities for Level 4

Level 4 improves the protection against 

biological and radiological agents and 

certain irritants in aerosol form, such as tear gas 

and pepper spray. 

For these agents, this provides a medium level 

of protection against outdoor releases and a 

low level of protection against indoor releases.

This level adds no capability to protect against 

chemical agents. At this level, sheltering in 

place provides capability for protecting against 

chemical warfare agents and toxic industrial 

chemicals (TICs).
4-22 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

Costs of replacement filters will increase, as will the labor to change 

filters, re-establish effective seals, and dispose of hazardous wastes that are 

characteristic for higher efficiency filters.

4.4.5 Level 5, Gas-Phase Filtration, Medium

Level

4.4.5.1 Scope and Capabilities

The second level of filtration involves the 

addition of adsorbers to the HVAC system 

to filter chemical agents from recirculated 

air and ventilation air. This level produces 

substantial protection against a chemical 

release either indoors or outdoors; 

however, it provides a lower level of 

protection against an outdoor release than 

Level 7.

Adsorbers for this application are 

commercially available and commonly 

used in buildings having special indoorair-quality requirements. As such, the 

adsorbers have a relatively low resistance 

(pressure drop of around 0.5 to 1 inch, 

water gauge) and consequently, a much lower efficiency (initially about 

99 percent) and capacity than adsorbers made to the higher standards of 

military or Department of Energy specifications. 

These adsorbers do not filter agents of higher vapor pressure as well as 

military adsorbers do. Typically, they have coarse granular carbon trays of 

1-inch depth in a V-bed configuration. The units typically have an initial 

bypass of at least 1 percent. There are also adsorbers made of multiple 

layers of pleated, carbon-loaded, non-woven material (see Figure 4-6). 

This capability is best attained with installation of adsorbers in an airhandling unit or ducted in line. A similar capability can be attained with 

free-standing, floor-mounted units or ceiling-mounted units; however, 

these are less practical in most large commercial buildings in that several 

units may be necessary in each room to provide performance equivalent 

to the units ducted in line or mounted in the air-handling unit. 

Service life of these adsorbers is typically 12 to 18 months; however, 

efficiency diminishes with time in service, to relatively low values within 

a year, reducing the protection provided to low levels later in the service 

Summary of Capabilities for Level 5

Level 5 applies a medium level of protection 

against chemical warfare agents and 

against some TICs released outdoors. 

It provides a low level of protection against 

indoor releases of these chemical agents. 

The filtering capability for chemicals of higher 

vapor pressure is less than that of Level 7.

This level provides no additional capability for 

biological or radiological agents beyond 

Level 4. 
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-23

Figure 4-6: Figure 4-6: 9,000-cfm filter un 9,000-cfm filter uniit iincorporat ncorporatiing pleated adsorbers. ng pleated adsorbers.

life period. Manufacturers of the adsorbers provide surveillance testing to 

help determine the frequency of filter replacement. 

4.4.5.2 Methods and Requirements

Adsorber units can be installed by adding an adsorber section 

(approximately 3 feet long) to an air-handling unit, or by adding an 

in-line filter unit in the supply duct. Upgrading the air-handling unit fan/

motor may be necessary to accommodate the additional airflow resistance 

of the adsorbers.

There are two types of adsorbers, those with granular carbon beds and 

those with carbon pleats consisting of non-woven material loaded with 

fine-mesh carbon granules. Comparison of performance between these 

two types of adsorbers can be made on a carbon-per-cubic feet per minute 

(cfm) basis (usually this is in the range of 0.05 to 0.1 pound per cfm for 

substantial efficiency and capacity). 

Multi-panel housings in which removable flat panels form V-bed 

configurations generally have greater bypass than V-bed cells or pleated 

cartridges. 
4-24 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

4.4.5.3 Cost Considerations

The installation costs for adsorber units are about $0.50 per cfm. With 

a one-year service life, filter replacement costs are about $0.25 per cfm 

per year. Additional operating energy costs are about one fourth the 

maintenance costs due to the pressure drop of the adsorbers (0.75 inch of 

water gauge).

4.4.6 Level 6, Aerosol Filtration, High

Level

4.4.6.1 Scope and Capabilities

This level is the first of two that involve 

very high efficiency filtering of ventilation 

air separately from recirculation air. This 

level is for aerosol filtration only and is 

to be applied in a continuously operating 

system, rather than activated upon 

detection, because biological agents are 

not detectable in real time. 

4.4.6.2 Methods and 

Requirements

This level involves the installation of a 

makeup-air unit with HEPA filters and 

an effective sealing system to prevent filter bypass. The makeup-air unit 

requires heating and cooling coils to temper the air introduced into the 

building before it is further conditioned by the air-handling units.

An ultraviolet germicidal irradiation (UVGI) system of certified 

performance could be used in place of the HEPA filter for disinfection 

of air as it enters the building; however, such systems also require 

mechanical filtration for removal of other aerosols (and to keep lamp and 

reflector surfaces clean). Although there are several UVGI systems on the 

market for use in air-handling units, most do not have the capability for 

high-efficiency disinfection of biological threat agents in air. Some systems 

are intended for surface disinfection, killing mold, bacteria, and fungi on 

cooling coils or drain pans. There is currently no certification process for 

UVGI systems for protection against bio-agent attack.

Summary of Capabilities for Level 6

For biological or radiological agents, 

Level 6 provides the highest possible level of 

protection against outdoor releases. 

Against an indoor release of biological or 

radiological agents, this level does not 

improve upon the protection Level 4 provides.

Except for irritant aerosols, this provides no 

additional capability for chemical agents

beyond sheltering in place (Levels 2 and 3) or 

the adsorbers of Level 5.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-25

Less space is required for Level 6 makeup-air units than Level 7, which 

requires both HEPA filters and high-efficiency adsorbers. Sizing of 

the filtration system in terms of airflow capacity is determined by the 

building’s leakage rate and the square footage of the protected space. 

With normal building construction techniques, leakage is less than 

optimum for pressurization of the building. Desired pressure levels 

in low-rise buildings are 0.1 to 0.2 inch, water gauge, and greater in 

high-rise buildings. Pressurizing a building to these levels usually takes 

substantially more ventilation air than is supplied for health and comfort 

requirements. Table 4-1, below, shows the flow rate of air required per 

square foot of floor area for a 0.1-inch, water gauge pressure.

The airflow required for pressurization can be determined by fanpressurization testing, American Society of Heating, Refrigerating and 

Air-Conditioning Engineers (ASHRAE) tables (ASHRAE, 2004), and tables 

based on previous fan-pressurization tests provided by the manufacturer. 

Table 4-1: Estimated Makeup Airflow Rate per Square Foot (Floor Area) 

to Achieve an Overpressure of 0.1 Inch, Water Gage

Type of Construction

Airflow Rate

(cfm per sq ft floor area)

Very Tight: 26-inch thick concrete walls and roof with no windows 0.04

Tight: 12-inch thick concrete or block walls and roof with tight windows 

and multiple sealed penetrations

0.20

Typical: 12-inch thick concrete or block walls with gypsum wall board 

ceilings or composition roof and multiple sealed penetrations

0.50

Loose: Wood-frame construction without special sealing measures 1.00

4.4.6.3 Cost Considerations

This level is relatively high in cost because it requires pressurization of 

the building or selected spaces to ensure that all exchange of indoor and 

outdoor air occurs through the filters. Pressurizing buildings typically 

requires substantial increases in the rate of ventilation air flow, which 

leads to increased heating and cooling costs.

4.4.7 Level 7, Gas-Phase Filtration, High

Level

4.4.7.1 Scope and Capabilities

As with Level 6, this level also involves filtering the ventilation air 

separately from recirculation air at very high efficiency. Level 7 involves 
4-26 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

the installation of high-efficiency gas 

adsorbers to filter makeup air for 

pressurizing the protected zones, and 

thereby expands the high-level protective 

capability to toxic gases and vapors.

Because this level includes HEPA 

filtration in series with the high-efficiency 

adsorber it provides the highest, most 

complete level of protection against an 

outdoor release of chemical, biological, 

or radiological agents. However, it is 

limited in the filtration of some chemical 

agents of higher vapor pressure. 

Generally, chemicals of vapor pressure above 10 millimeters of mercury 

are filtered by chemisorption; that is, carbon is impregnated with salts 

of copper, silver, zinc, and molybdenum, and the gases react with these 

impregnants as they pass through the filter bed to form products that 

are innocuous or retained in the bed. However, the best broad-spectrum 

carbon will not filter all toxic chemicals. The addition of a special sorbent, 

mixed or layered in the bed, can add to the filter capability for specific 

gases, but increases the size and resistance of the adsorber. 

Filtering only ventilation air is not effective against an indoor release. 

Protecting against an indoor release requires the internal filtration of 

Levels 4 and 5 or the physical security measures of level 2.

4.4.7.2 Methods and Requirements

Among the primary decisions in applying this level of protection is 

whether to protect the whole building or a relatively small selected space. 

This decision is usually based on cost and the need for a high level of 

protection. 

Whole building. In pressurizing the whole building, mechanical rooms are 

generally excluded or divided to exclude furnaces or boilers from the 

protected space. In mechanical rooms containing both air-handling units 

and boilers, the mechanical room is partitioned so that the air-handling 

units are within a pressurized space and the boilers are not.

Selected space. Spaces usually selected for pressurized, high-level chemical 

protection are security operations centers, emergency operations centers, 

command and control centers, command suites, and safe rooms. A 

safe room with this level of protection is considered a Class I safe room 

(section 4.4.3).

Summary of Capabilities for Level 7

For chemical agents, Level 7 provides a very 

high level of protection for filterable chemicals 

released outdoors.

This level does not increase the protection against 

biological or radiological agents beyond that of 

Level 6.

Against an indoor release, this level does not 

provide benefit beyond that of Level 5.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-27

A second decision regarding the application of Level 7 is whether to 

design a continuously operating system or a standby system. The latter 

may be applied because gas-phase filtration is for chemical agents, which 

can be detected in real time. Therefore, the system can be activated upon 

detecting a release or learning of a heightened threat level. Canistertype filter systems for use in safe rooms and home shelters are intended 

for standby use; these are hermetically sealed and can retain their full 

capability for at least 10 years. The high-efficiency filtration unit can be 

installed in a mechanical room, on the roof, or at grade inside secure 

fencing. 

Three types of adsorbers commonly used are V-bed, radial-flow, and 

pleated, as shown in Figure 4-7. Installations of radial-flow and V-bed 

adsorbers are shown in Figures 4-8 and 4-9.

Figure 4-7: Three types of high-efficiency gas adsorbers commonly used (from left to right: radial-flow M98 

military adsorber, V-bed adsorber, and multi-layer pleated adsorber).

Figure 4-8: Radial-flow 

adsorbers in multiple 

1,000-cfm housings in 

a 16,000-cfm system 

serving a hospital.
4-28 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

4.4.7.3 Cost Considerations

Installing, operating, and maintaining systems for ultra-high efficiency gas 

adsorption is very expensive. Installing such a system costs approximately 

$20 to $100 per square foot.

The principal maintenance cost is the replacement of filters, the highefficiency gas adsorbers, approximately every 3 years. This equates to a 

cost of $2 per year per cfm, or about $0.50 to $1.00 per square foot per 

year. Energy costs for such units are about one-fourth the maintenance 

costs. 

4.5 SUMMARY

Operational Risk-Reduction Measures for CBR

T he following summarizes the operational measures for CBR risk 

reductions:

Develop plans, procedures, and training for sheltering in place, 

evacuation, and purging 

❍

Figure 4-9: A 6,000-cfm 

V-bed filter unit serving 

a 12,000 sq ft safe 

room.
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-29

Provide CBR threat awareness and response training to building 

occupants

Purchase escape hood respirators for all occupants and provide 

training in their use

Secure air intakes, mechanical rooms, and HVAC plenums against 

unauthorized access

Perform entry inspections at the building lobby

Institute mail-screening procedures

Maintain operational security for building plans and building signage 

Building Upgrades for CBR

Install single-switch control of all building fans to facilitate sheltering 

in place and purging

Install a public-address system to achieve rapid implementation of 

emergency actions

Apply sealing measures to tighten selected safe room(s)

Install automatic dampers for outside air intakes and exhaust fans to 

facilitate sheltering in place

Place recirculation filter units having substantial adsorbers for use in 

safe rooms

For safe rooms, install a separate, isolated recirculation system for 

cooling and heating

Install and monitor video-surveillance cameras

Isolate the lobby, mailroom, cloakroom, and loading dock 

architecturally and mechanically

Install filters of greater depth/surface area and higher MERV rating, 

such as MERV 14, 15, or 16 mini-pleats, in air-handling units and seal 

filters and frames to minimize bypass

Modify air-handling units to install indoor-air-quality type, low 

resistance adsorbers

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
4-30 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

Install ventilation/makeup-air units with HEPA filtration for each zone 

to be protected

Install ventilation/makeup-air units with high-efficiency gas adsorbers, 

as well as HEPA filters for each zone protected

Install vestibules or revolving doors for highly protected zones

With upgraded air filtration, operate air-handling units at outdoor air 

fractions that produce positive pressures of approximately 0.1 to 0.2 

inch, water gauge, in the building

4.6 CBR Protection Measures 

T he preceding discussions of CBR threat mitigation measures can 

be condensed into the following list. It is presented here as an 

example of measures that might be generated by the FEMA 452 

process and implemented using this document (FEMA 459), as discussed 

in Chapter 2. These measures are all included in the list that comprises 

the vertical axes of the matrices in Section 2.3.

Level 1, Operational Measures and Expedient Protection

Expedient sheltering in place

Designating safe rooms, interior rooms having a lower air 

exchange rate

Identifying switches for all air-handling units and fans for 

deactivation

Defining procedures for sheltering and for purging the building 

after plume passage

Establishing a building-wide notification system

Familiarizing occupants with procedures and responsibilities

Evacuation

Purging

Using escape respirators

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS 4-31

Level 2, Enhanced Physical Security

Secure air intakes against unauthorized access

Secure mechanical rooms and HVAC plenums against unauthorized 

access

Perform entry inspections

Employ video surveillance equipment

Institute mail screening procedures

Maintain operational security to building plans and signage 

Apply mechanical and architectural isolation of lobby, mailroom, 

cloakroom, and loading docks

Level 3, Enhanced Sheltering In Place

Install single-switch control of fans for sheltering and purging

Tighten the seal for the envelope of the building and selected safe 

room(s)

Install automatic dampers for outside air intakes and exhaust fans

Implement a public address system to achieve rapid implementation 

of emergency actions

Isolate mechanical spaces that require large volumes of outside air

Install separate fans and air streams for ventilation and recirculation, 

as well as cooling and heating, of safe rooms

Use recirculation filter units in safe rooms

Level 4, Aerosol Filtration, Medium Level

Seal filter frames to minimize bypass

Install filters of greater depth/surface area and higher MERV rating

Operate at positive internal pressures

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
4-32 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO CBR THREATS

Level 5, Gas-Phase Filtration, Medium Level

Install indoor-air-quality type, low-resistance adsorbers

Operate at positive internal pressures

Install vestibules or revolving doors for highly protected zones

Level 6, Aerosol Filtration, High Level

Install ventilation/makeup-air units with HEPA filtration

Install vestibules or revolving doors for highly protected zones

Operate at positive internal pressures

Level 7, Gas-Phase Filtration, High Level

Install ventilation/makeup-air units with high-efficiency adsorbers and 

HEPA filtration

Install vestibules or revolving doors for the protected zones

Operate at positive internal pressures

All of these measures can be implemented independently with the 

exception of expedient sheltering in place (Level 1). 

❍

❍

❍

❍

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-1

5

PRINCIPLES OF DESIGN FOR RISK REDUCTION

RELATED TO OPERATIONAL SECURITY MEASURES

Operational security measures for commercial buildings 

augment the blast and CBR physical protective measures by 

establishing the capability to deter, detect, delay, and respond 

to these threats, as well as other harmful acts. Operational security 

measures encompass the physical security systems, the security policies 

and procedures, and the personnel resources committed to protecting 

commercial buildings. This chapter reviews the range of operational 

security measures available to commercial facilities to counter blast and 

CBR threats and addresses considerations for applying these measures 

to retail, office, and multifamily residential facilities, and hotels. The 

chapter concludes with an examination of the integration of operational 

and physical protective measures, including the relative flexibility of 

operational measures and the resulting tradeoffs during implementation.

5.1 Overview of Operational

Security Measures

Operational security measures work 

in conjunction with blast and CBR 

measures to protect personnel, 

equipment, and intellectual property. A 

baseline of protective measures established at 

commercial facilities might include locking 

doors, lighting parking lots, and controlling 

access to small expensive items. Beyond this 

baseline, additional security measures are 

commonly added to counter specific threats. 

These measures might include procedures 

as simple as checking the picture and date 

on an identification card. Additional security measures can also include 

sophisticated systems, such as biometric identification, metal detectors, 

video assessment and surveillance systems, armed security personnel, and 

even chemical and radiation detectors.

Operational security measures can be divided into five basic components: 

detection and assessment measures, interdiction and response measures, 

procedural measures, preparedness measures, and security master 

planning. 

Operational Security Measures

Detection and Assessment Measures

Interdiction and Response Measures

Procedural Measures

Preparedness Measures

Security Master Planning

❍

❍

❍

❍

❍
5-2 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

5.2 Detection and Assessment 

Measures 

Detection and assessment measures for blast events and CBR 

threats include exterior intrusion detection, interior intrusion 

detection, CCTV systems, access control systems, vehicle 

inspections, duress alarms, and mail/package screening.

5.2.1 Exterior Intrusion Detection Systems

Exterior intrusion detection systems are used to detect an intruder 

crossing the boundary of a protected area. They can also be used in clear 

zones along fences or around buildings or for detecting unauthorized 

access to critical outdoor infrastructure (transformers, water tanks, 

etc.). Generally these systems use infrared, (see Figure 5-1) seismic, 

microwave, or video motion technologies to alert security personnel to 

an encroachment. Because of the nature of the outdoor environment, 

exterior sensors are more susceptible to nuisance and environmental 

alarms than interior sensors. The use of dual technology sensors and a 

proper assessment method is key to an effective system.

Figure 5-1: Doorway 

with balanced 

magnetic switch 

and passive infrared 

motion sensor.

Source: Terrence Ryan
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-3

5.2.2 Interior Intrusion Detection Systems

Interior intrusion detection measures, like exterior systems, are designed 

to detect penetration or attempted penetration through perimeter 

barriers. Interior sensors can be deployed at a facility’s perimeter or 

in an interior space. An interior asset is one contained within a cube 

with sensors protecting all six faces, such as walls, ceilings, and floors, 

to include duct openings, doors, and windows. Tamper protection and 

access/secure mode capabilities should be considered when planning 

interior systems. Interior sensors include:

Structural vibration sensors

Glass-breakage sensors

Passive ultrasonic sensors

Balanced magnetic switches

Grid wire sensors

Microwave motion sensors

Passive infrared motion sensors

Dual technology sensors

Video motion sensors

5.2.3 Video Assessment and Surveillance 

Systems

Video assessment and surveillance systems may be used to conduct 

access control, surveillance, and video motion detection. Access control 

applications include monitoring building entrances, loading docks, 

and other access points. Surveillance applications include maintaining 

observation over large or concentrated areas, such as site access points, 

parking lots, building perimeters, key interior areas, or points of alarm. 

Video motion detection applications have sensors that generate an alarm 

when an intruder enters a selected portion of a camera’s field of view. 

They can be programmed to activate alarms, initiate recording, or prompt 

other designated actions when motion is detected by a security camera.

Interior Applications. Alarm assessment, card reader event assessment, 

emergency exit activation assessment, and surveillance of lobbies, 

corridors, and open areas.

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

Dual Technology Sensors

Dual technology sensors use 

two technologies in a logical 

combination to reduce false alarms. 

One example is a combination of 

a microwave sensor and a passive 

infrared sensor that must activate 

simultaneously to create an alarm.
5-4 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

Exterior Applications. Alarm assessment, individual zones and portal 

assessment, specific paths and areas, exclusion areas, and surveillance 

of activities.

Video Motion Detection. Video motion sensors are available on most 

digital video recorders (DVRs) used in security applications. The 

sensor processes and compares successive images against predefined 

alarm criteria. The system usually provides adjustable windows that 

can be positioned to monitor selected points of the video image. 

Some DVRs can be programmed to monitor very specific fields 

of view for specific types of motion in order to increase system 

effectiveness and minimize extraneous detections.

Video assessment and surveillance systems may be monitored in real time 

or recorded for later viewing (see Figure 5-2). Systems designed for one 

usage may not be optimized for the other. 

❍

❍

Additional Video Assessment and Surveillance 

Systems Considerations

Plan camera placement to provide adequate coverage of vehicle 

and pedestrian movements along perimeter fence lines, site, 

roadway and parking lot access points, building exteriors, entrances, 

emergency exits, and utility systems. 

Use the integration features of modern Pan Tilt Zoom cameras 

systems to point and focus on cues from door contacts and switches, 

interior motion detection devices, or other sensors.

Integrate landscaping efforts with camera placement initiatives. 

Control plantings and tree and shrubbery growth to avoid 

obstructing camera fields of view. 

Perform a lighting survey to ensure lighting levels are adequate and 

consistent with camera equipment manufacturer specifications. 

Train staff members on the use (and limitations) of the camera system. 

Video motion sensors can greatly improve the efficiency of security 

personnel monitoring security cameras by alerting them when 

motion is detected.

❍

❍

❍

❍

❍

❍

Additional Video Assessment and Surveillance 

Systems Considerations

Plan camera placement to provide adequate coverage of vehicle 

and pedestrian movements along perimeter fence lines, site, 

roadway and parking lot access points, building exteriors, entrances, 

emergency exits, and utility systems. 

Use the integration features of modern Pan Tilt Zoom cameras 

systems to point and focus on cues from door contacts and switches, 

interior motion detection devices, or other sensors.

Integrate landscaping efforts with camera placement initiatives. 

Control plantings and tree and shrubbery growth to avoid 

obstructing camera fields of view. 

Perform a lighting survey to ensure lighting levels are adequate and 

consistent with camera equipment manufacturer specifications. 

Train staff members on the use (and limitations) of the camera system. 

Video motion sensors can greatly improve the efficiency of security 

personnel monitoring security cameras by alerting them when 

motion is detected.

❍

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-5

5.2.4 Access Control Systems

The building layout, rate and flow of employees and visitors, threat 

level, personnel available, and types of technical equipment installed are 

considerations for establishing access control measures. A screening plan 

should be comprehensive to permit authorized personnel to conduct 

their business with minimum delay, but provide access to only those with 

a legitimate need. Access control measures normally consist of a public 

access control area, a walk-through metal detector and/or hand-held 

metal detector, and an entry control system.

Public Access Control Area. This allows for identifying and screening of 

visitors before admitting them into restricted areas (see Figure 5-3).

Walk-Through Metal Detector and/or Hand-Held Metal Detector. Metal 

detectors are intended to detect the presence of concealed firearms 

or other weapons while avoiding the intrusiveness of individual 

searches or frisking. Additionally, screening may detect the presence 

of concealed electronic devices (such as hidden transmitters) and 

explosive devices having metal components.

Entry Control Systems. The function of an entry control system is to 

ensure that only authorized personnel are permitted into or out of 

a controlled area. Entry can be controlled by locked fence gates, 

locked doors to a building or rooms within a building, or specially 

designed portals. Entry control can be enforced physically with 

❍

❍

❍

Figure 5-2: Video 

assessment and 

surveillance systems.

Source: Bob Cizmadia
5-6 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

guards or automatically using entry control devices. For a guard 

system, guards verify that a person is authorized to enter an area, 

usually by comparing the photograph and personal characteristics of 

the individual requesting entry. For an automated system, the entry 

control device verifies that a person is authorized to enter or exit. 

The automated system usually interfaces with locking mechanisms 

on doors or gates that open momentarily to permit passage. All entry 

control systems control passage using one or more of three basic 

techniques: a Personal Identification Number, a credential, or an 

identifying feature like a fingerprint. Automated entry control devices 

based on these techniques are grouped into three categories: code, 

credential, and biometric devices.

5.2.5 Vehicle Inspection Systems

Vehicle inspection systems employ personnel to examine entering 

vehicles in accordance with predetermined guidelines (see Figure 5-4). 

Figure 5-3: Blast effects related to access control. Source: Michael Kaminskas
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-7

Inspections may be appropriate at low and high threat locations. At low 

threat locations, guards may only inspect a vehicle driver’s identification 

or a facility parking sticker. At higher threat locations, guards may inspect 

the vehicle and occupants’ identification, vehicle interior, undercarriage, 

engine compartment, interior, trunk, and gas-fill cover area. Inspections 

should occur as far from critical site facilities as possible (preferably at the 

site perimeter). The inspection area may include vehicle arresting devices 

that prevent vehicles from tailgating or from leaving the inspection area 

without permission.

5.2.6 Duress Alarms

Duress alarms installed at fixed locations (see Figure 5-5) or carried as 

mobile devices alert security personnel to a potential threat or incident. 

If used outside a defined area, duress alarms should be programmed to 

transmit the precise location of the user.

5.2.7 Mail/Package Screening

Mail and package screening involves controlling and screening the mail 

and packages for contraband, weapons, chemical, biological, radiological, 

or incendiary materials, and other items, whether brought into a facility 

by an individual or by mail/package delivery. Screening technologies 

may detect components of explosive devices or explosive compounds 

by radiographic analysis, by analyzing chemical emissions, or by other 

methods (see Figure 5-6). Radiological detectors, which are accurate, 

Figure 5-4: Entry control 

point.

Source: Terrence Ryan
5-8 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

reliable, and relatively inexpensive, may also be used. Package screening 

measures may include:

Arranging for off-site inspection of mail/packages

Centralizing mail/package delivery and screening into a standalone 

building or on the perimeter of the facility

Providing explosive detection and response training to mail handlers

Conducting X-ray screening of mail and packages

Utilizing explosive and CBR detection equipment 

❍

❍

❍

❍

❍

Figure 5-6: Example of 

an air sampling system 

in a mailroom.

Source: Terrence Ryan

Figure 5-5: Emergency 

phone in parking 

garage.

Source: Bob Cizmadia
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-9

5.3 Interdiction/Response 

Measures

Response/interdiction forces provide a means to delay adversaries 

while protecting personnel and critical locations from blast and 

CBR events. Response force requirements are dependent on 

contingency planning and range from on-site or off-site security guards 

to local and State police forces. Response/interdiction measures include 

security guard forces with a deterrence or delay role, security guard forces 

with a response/interdiction role, and general contingency planning with 

local and State police. 

Security guard services consist of proprietary or contract guards, or 

a combination of both depending on their purpose, the size of the 

facility, and other factors. Their effectiveness, however, is dependent on 

the quality of the individuals involved. Proper licensing, training, and 

background checks are critical for ensuring each individual response 

force member is qualified.

5.3.1 Guard Force – Detection/Delay Role

Guard forces with a detection or delay role generally monitor video 

surveillance equipment, check credentials, and patrol. They may be 

located in a lobby area, a patrol area, or in a security operations center 

connected to several entry points. These security guards perform access 

control functions and surveillance by either direct observation or through 

video surveillance. If an event occurs, they conduct an assessment and 

coordinate the response actions of employees and internal and external 

response forces. They may also respond directly to events if simple 

interdiction may limit the incident or to assist with evacuation and 

isolation.

For the largest facilities, the security guard may be afforded a protected 

booth with hardened walls, protected egress, pass tray, access denial 

system, CCTV monitors, controls of entrances and exits, radios, 

telephones, paging systems, intercoms, key boxes, indicator and alarm 

panels, the active vehicle barrier override control, security light controls, 

elevator controls, and controls for air-handling systems.
5-10 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

5.3.2 Guard Force – Response/Interdiction 

Role

Guard forces with a response/interdiction role are more highly trained 

and responsible for conducting containment and denial actions. Guards 

may be trained and equipped for duties including: delaying at a distance, 

delaying to permit occupants at risk to escape, and finally delay–hold–

counterattack. These guards protect personnel, goods, and services, but 

should not be expected to engage in law enforcement activities.

5.3.3 Response Force Contingency

Planning

Conducting contingency planning and documenting procedures are 

critical to an effective response function. Contingency planning involves 

identifying potential intruders and developing response procedures for 

each likely threat. For example, facilities may specify a level of force that 

guards would be expected to use in different scenarios. Contingency 

planning also ensures the availability and redundancy of communication 

systems with both internal and external responders. This increases the 

ability of the guards to receive notification of an event, coordinate their 

internal response, and synchronize the response with outside agencies.

Guard Force Roles

Detection. Monitor video surveillance equipment, control access, 

and patrol to detect threats.

Delay at a Distance. Increase the time that elapses between the 

detection of an imminent terrorist attack and the actual onset of 

an attack to permit the arrival of response forces or the successful 

evacuation of personnel. 

Delay to Permit Flight. Increase the amount of time that elapses 

between the onset of an attack and terrorist access to executives to 

permit the arrival of response forces or the successful evacuation of 

executives under attack. 

Delay, Hold, and Counterattack. Increase the duration of an attack 

by allowing occupants to remain secure in a safe haven until a 

response force can arrive to repulse the attack, and apprehend the 

terrorists.

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-11

5.4 Procedural Measures

Procedural measures are the policies and procedures that limit 

vehicle and pedestrian movement around and within critical 

areas, limit the release of building information, such as plans 

and schematics, and encourage employee support of security programs. 

While most commercial buildings need to provide access for their 

tenants, customers, or the general public, each employee, maintenance 

person, and visitor does not need equal access to every space. Restricted 

areas may protect critical infrastructure or simply keep the public in 

easily observable spaces. Designating and enforcing parking controls are 

procedural measures of special note because of the possible use of vehicle 

bombs by terrorists.

5.4.1 Restricted Areas

Restricted areas are classified as controlled, limited, or exclusion areas, 

depending on the degree of security and control required (see Figure 5-7).

Figure 5-7: Electronic 

entry control device 

into restricted area.

Source: Bob Cizmadia
5-12 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

Controlled Area. A controlled area is that portion of a restricted area near 

or surrounding a limited or exclusion area. Entry to a controlled area is 

restricted to personnel with a need for access. Movement of authorized 

personnel within this area is not necessarily controlled because entry does 

not provide access to a security interest. The controlled area is provided 

for administrative control, for safety, or as a buffer zone to the in-depth 

security of the limited or exclusion area.

Limited Area. A limited area is a restricted area near a security interest. 

Uncontrolled movement may permit access to the security interest. 

Escorts and other internal restrictions may prevent access within limited 

areas.

Exclusion Area. An exclusion area is a restricted area containing a security 

interest. Uncontrolled movement permits direct access to the security 

interest.

5.4.2 Parking and Traffic Controls

In general, vehicle parking near buildings should be discouraged due 

to the threat of vehicle bombs. While pre-entry screening of vehicles 

at perimeter entrances will decrease the risk of penetration by vehicleborne improvised explosive devices (IED), it does not eliminate this 

hazard. Restricting unscreened vehicles from parking under facilities, 

from parking within a predetermined distance from a building, or from 

traveling into a protected area will increase blast protection. 

In summary, parking and traffic control activities include:

Control on-site parking with ID checks, security personnel, and access 

systems (see Figure 5-8)

Separate employee and visitor parking

Eliminate internal building parking

Ensure natural surveillance by concentrating pedestrian activity, 

limiting entrances/exits, and eliminating concealment opportunities

Prevent pedestrian access to parking areas other than via established 

entrances

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-13

5.4.3 Restrict Access to Facility

Information

Facility information, including drawings and operational procedures for 

mechanical, electrical, plumbing, structural, and security systems should 

be controlled, and its release should be restricted.

5.4.4 Encourage Employee Support

Procedural measures require that employees be motivated to support 

the security program. Regardless of the security measures employed, 

if employees do not follow operational policies and procedures, 

vulnerabilities will persist. An appropriate corporate climate, adequate 

operational planning, and established management objectives will help 

encourage employees to support security measures.

5.5 Preparedness Measures

Preparedness measures are actions taken to increase readiness 

for a crisis, mitigate impacts, and respond to and recover from 

an incident. These include disaster preparedness planning, 

conducting risk assessments, developing mass notification warning 

systems, evacuation planning, preparing to shelter in place, monitoring 

systems and resources, and conducting training exercises. 

Figure 5-8: Parking 

control.

Source: Terrence Ryan
5-14 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

5.5.1 Develop a Disaster

Preparedness Plan

Protecting facilities begins with developing a disaster 

preparedness plan. The FEMA Web site provides 

numerous links and examples of plans that can be 

tailored to fit your facility. The risk assessment, as well 

as identification of mitigation measures to minimize 

or prevent losses, provides the basis for developing the 

plan.

5.5.2 Conduct Risk Assessments

Risk assessments are conducted to assess threat/hazards, 

impacts on assets, vulnerabilities to incidents, and 

subsequent risks. Security countermeasures should be 

defined and prioritized relative to their impact on risk.

5.5.3 Develop Mass Notification 

Systems

Mass notification systems, such as automatic messaging 

or public address systems, should be developed to reach 

all building occupants. These systems should provide 

warning and alert information, along with actions to 

take before and after an incident. System and electric power redundancy 

should be ensured.

5.5.4 Evacuation Planning and Shelter in 

Place Preparation

The building occupants should be prepared for independent action 

prior to the arrival of emergency responders. This preparation involves 

evacuation planning and shelter in place preparation. The building 

occupants should also be trained on the Incident Command System 

in order to understand the chain of command, available integrated 

communications, and management of resources throughout the recovery.

Preparedness Measures

Develop a Disaster 

Preparedness Plan

Conduct Risk Assessments

Develop Mass Notification 

Systems

Conduct Evacuation 

Planning and Shelter in 

Place Preparation

Monitor Systems and 

Resources

Conduct Training Drills 

and Exercises

More information on disaster 

preparedness is available at 

the FEMA Web site: www.fema.

gov/plan/index.shtm

❍

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-15

5.5.5 Monitor Emergency Systems and

Resources

Systems and resources intended to support the facility during a crisis 

should be monitored to ensure their availability and function. Examples 

of such systems and resources include, but are not limited to:

Emergency equipment and critical utilities

Fire alarms and detection and suppression systems

Emergency resources and vendors (e.g., fuel for emergency 

generators)

Alternate worksites

Updated maps and floor plans 

System backups and off-site storage

5.5.6 Conduct Training Drills and

Exercises

Training drills and exercises help to improve efficiency of emergency 

response teams and employees, clarify responsibilities, reveal weaknesses, 

and reduce stress. A commitment to testing also lends credibility and 

authority to the security program.

In summary, training involves:

Rehearsing emergency plans with local law enforcement

Conducting joint exercises with first responders 

❍

❍

❍

❍

❍

❍

❍

❍

Emergency Management

Complete information on the management of various emergency events 

and the Incident Command System is available from the FEMA Web site: 

www.fema.gov/emergency/nims/index.shtm
5-16 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

5.6 Security Master Planning

All of these operational security measures should be guided by the 

final component, a Security Master Plan (see Figure 5-9). This 

3- to 5-year plan, based on the goals of the overall organization, 

states the vision, goals, and objectives of the security program. The plan 

should also outline the operational security measures, the path for the 

security program to keep pace with the changing threat environment, and 

future initiatives. Further, it should be integrated into the organization’s 

facility planning process as well as benchmarked against the security 

programs of similar facilities. 

Figure 5-9: Security Master Planning integrates the operational security measures into the organization’s 

facility planning process. Source: Terrence Ryan
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-17

A comprehensive Security Master Plan should:

Be communicated and disseminated to all levels of management and 

building occupants as appropriate

Be integrated into the facility construction or renovation planning

Be benchmarked or compared to related facilities

Be tested and evaluated

Identify threats/hazards, assets, vulnerabilities, and risks 

Establish a security improvement implementation schedule 

Establish a security operating and capital budget 

Follow regulatory or industry guidelines/standards

5.7 Additional Aspects of

Operational Security Measures 

Related to Blast Events

Tactics for developing and employing IEDs are continuing to evolve. 

Fortunately, responses to IED threats are also rapidly changing as 

technologies and procedures to detect 

and mitigate the terrorist leave-behind IED, 

human-carried IED, and vehicle-borne IED 

threats progress. Evolving countermeasure 

technologies are designed to provide timesensitive information that security forces, 

critical asset managers, police/bomb squads, 

and incident commanders need to detect and 

counter IEDs away from critical infrastructure 

and personnel.

Additional operational security measures 

related to blast events include establishing 

an explosive detection program, establishing 

bomb threat procedures, and establishing blastrelated mail/package handling procedures.

❍

❍

❍

❍

❍

❍

❍

❍

Additional Operational 

Security Measures Focused on 

Blast Events

Establish an explosive detection 

program

Establish bomb threat procedures 

Establish blast-related mail/package 

handling procedures

❍

❍

❍
5-18 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

5.7.1 Establish an Explosive Detection 

Program

The effectiveness of an explosive detection program is dependent on 

the level of sophistication of the detection measures. At the low end, 

bomb detection is conducted by inspection. Higher levels of protection 

are achieved using detection equipment, such as X-ray devices, metal 

detectors, and explosive detectors. Explosive detection dogs are an 

alternative to explosive detection technology. 

5.7.2 Establish Bomb Threat Procedures

The following procedures should be followed when receiving a 

telephoned bomb threat:

Get as much information from the caller as possible. Ask the following 

questions, if possible: 

When is the bomb going to explode? 

Where is it right now? 

What does it look like? 

What kind of bomb is it? 

What will cause it to explode? 

Did you place the bomb?

Why? 

What is your address? 

What is your name? 

Keep the caller on the line and record the conversation.

Notify the police and building management.

5.7.3 Establish Blast-Related Mail/Package 

Handling Procedures

Over the years, postal inspectors have identified typical characteristics of 

suspicious parcels. In many cases the packages:

Are unexpected or from someone unfamiliar

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-19

Have no return address or have one that cannot be verified as 

legitimate

Have protruding wires or aluminum foil, strange odors, or stains

Show a city or State in the postmark that doesn’t match the return 

address

Are of unusual weight given their size or are lopsided or oddly shaped

Are marked with threatening language

Have inappropriate or unusual labeling

Have excessive postage or packaging material, such as masking tape 

and string

Have misspellings of common words

Are addressed to someone no longer with your organization or are 

otherwise outdated

Have incorrect titles or titles without a name

Are not addressed to a specific person

Have hand-written or poorly typed addresses

5.8 Additional Aspects of

Operational Security Measures 

Related to CBR Events 

When protecting and responding to an accidental hazardous 

material release or an intentional CBR attack on a 

commercial building, focus operational security measures on 

personnel and vehicle access points, storage areas, the roof, mechanical 

areas, outdoor air intakes, and water utility feeds. The operational security 

needs of each building should be individually assessed, as the threat from 

a nearby hazardous material release or an actual CBR attack will vary 

considerably from building to building (Figure 5-10). Some operational 

security measures are low cost, such as locking doors to mechanical 

rooms or water utility pits, and can be implemented in retail, office, and 

multifamily residential buildings. Other operational security measures, 

such as personnel and package searches by X-ray or explosive detection 

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
5-20 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

equipment, are expensive and may substantially inconvenience businesses. 

Measures should be implemented as warranted after careful consideration 

of the likelihood of an incident and the resulting consequences.

Additional Operational Security Measures Focused 

on CBR Events

Restrict access, and secure and monitor outdoor air intakes

Light, secure, and monitor utility access points

Secure and monitor exterior mechanical/electrical spaces

Secure and monitor interior HVAC access points

Provide internal first responders appropriate hazardous materials 

equipment 

Restrict access to facility and utility drawings

Prevent unauthorized access and monitor roof areas

Establish CBR related mail/package handling procedures

❍

❍

❍

❍

❍

❍

❍

❍

Figure 5-10: Projected 

plumes of CBR 

incident.

Source: Michael

Kaminskas
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-21

5.8.1 Prevent Access, and Secure and

Monitor Outdoor Air Intakes

A contaminant could quickly spread throughout the building by the 

HVAC system. Air intakes that are publicly accessible and at or below 

ground level are at the most risk due to ease of approach, as well as 

characteristics of many CBR agents that cause them to remain close to 

the ground. Relocating or extending the air intakes upward can prevent 

access. Creating a restricted area to prevent public access, but allow access 

for authorized personnel can also improve security. Fencing or similar 

see-through barriers are preferred to allow visual detection of abnormal 

activity or a deposited CBR source. Security lighting should be provided 

for outdoor air intakes and other accessible points of the HVAC system, 

which should also be monitored with CCTV cameras. Intrusion detection 

sensors programmed to activate alarms, redirect surveillance cameras, and 

initiate recording should also be installed.

5.8.2 Establish CBR-Related Mail/Package 

Handling Procedures

Additional measures to mitigate the dangers from suspicious envelopes 

and packages with potential CBR agents include: 

Refraining from eating or drinking in a designated mail handling area

Placing suspicious envelopes or packages in a plastic bag or some 

other type of container to prevent leakage of contents

Avoiding sniffing or smelling suspect mail

Covering the envelope or package with anything available (e.g., 

clothing, paper, or trash can)

Leaving the room and closing the door and/or sectioning off the area 

to prevent others from entering

Washing your hands with soap and water to prevent spreading any 

contaminants to your face

Reporting the incident to your building security official or an available 

supervisor, who will notify authorities without delay

Listing all people who were in the room or area when this suspicious 

letter or package was recognized to help local public health 

❍

❍

❍

❍

❍

❍

❍

❍
5-22 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

authorities and law enforcement officials with follow-up investigations 

and advice

5.8.3 Additional Measures

Additional measures to mitigate the potential spread of CBR agents 

through plumbing, mechanical, and electrical systems include: 

Hardening and locking incoming water service line junction points 

and service pits by installing intrusion detection sensors on the access 

points for all site utilities.

Providing security lighting and monitoring on-site stored water and 

associated junction points with CCTV systems (Figure 5-11).

Conducting perimeter surveys to identify mechanical, plumbing, and 

electrical rooms with exterior doors, windows, and utility openings. 

Hardening and locking the doors. Providing grills or louvers for 

all windows and man-passable openings in exterior walls below the 

second floor. (Openings greater then 96 square inches are considered 

man-passable.) Installing intrusion detection sensors on the access 

points. 

❍

❍

❍

Figure 5-11: Exterior 

video camera for 

monitoring critical 

utilities.

Source: Bob Cizmadia
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-23

Securing exterior mechanical spaces and equipment. Identifying 

external mechanical spaces and equipment that are publicly accessible 

and establishing a means for direct surveillance, or monitoring with 

intrusion detection equipment and CCTV systems.

Securing interior HVAC access points, such as return-air grills. 

Identifying the return-air grills that are publicly accessible and 

establishing a means for direct surveillance, or monitoring with 

intrusion detection equipment and CCTV systems. Removing or 

relocating furniture that obscures surveillance or provides access to 

the return air grills. 

Providing internal first responders access to appropriate hazardous 

materials response equipment. Required items, such as a hazardous 

material suit, gloves, boots, and a protective hood, may be packaged 

together for convenience. 

Restricting access to mechanical, plumbing, and electrical systems 

by outside maintenance personnel. Providing escorts for outside 

maintenance personnel that have not been pre-screened or are not 

from a trusted provider. 

Restricting access to facility and utility drawings and schematics. 

Preventing unauthorized access and monitoring facility roofs, which 

can provide access to HVAC systems, air intakes, and exhaust vents. 

Establishing fencing or barriers to restrict access from adjacent roofs. 

Locking and monitoring roof access doorways. Providing grills or 

louvers to man-accessible openings. 

5.9 Prioritization of Operational

Security Considerations 

Commercial buildings range in function from retail to office to 

multi-family facilities and hotels. They can be free-standing, 

strip mall, or multi-story structures, and have one occupant or 

thousands. These characteristics vary depending on whether building is 

located in a rural setting, a suburban setting, or a large urban area. The 

following general guidance is provided to protect retail, office, and multifamily apartment buildings, and hotels. 

❍

❍

❍

❍

❍

❍
5-24 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

5.9.1 Retail Buildings

Retail buildings are openly accessible to the public. This limits some of 

the operational physical security measures that can be applied. Physical 

hardening of the critical infrastructure may be implemented to address 

this limitation. However, even in these buildings, operational security 

measures can be applied:

Restricted areas can be established for mechanical rooms, loading 

docks, roofs, and air vents. 

Interior and exterior CCTV systems may be established both for loss 

prevention and security detection.

Anti-ram, landscaping, and other vehicle barriers may be established 

to mitigate the vehicle-borne IED threat. 

Certain detection and delay measures, such as visitor screening and 

access control, may not be practical during business hours. However, 

after business hours, all intrusion detection measures can be activated. 

Most procedural, preparedness, and master planning measures can 

be applied. Of these, rehearsing emergency plans with local law 

enforcement and conducting joint exercises with first responders 

are especially important because they contribute to a coordinated 

response in an incident.

5.9.2 Office Buildings

Office buildings usually have a circulation plan and procedures that 

permit greater control over visitors compared to retail facilities. This 

facilitates the use of the full range of the operational security measures to 

protect offices from blast and CBR attacks. Based on the risk assessment 

for an office building, effective physical security measures to deter, 

delay, detect, and interdict/respond may be established. All procedural, 

preparedness, and master planning measures, as appropriate, may also be 

applied.

5.9.3 Multi-Family Apartment Buildings

A range of operational security measures is available for use in multifamily apartment buildings. Emergency preparedness plans and occupant 

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-25

education may be the most important life savers in the event of an attack. 

Measures should include:

Reviewing and updating emergency preparedness plans 

Providing education and training to occupants on evacuation 

procedures and identifying and reporting suspicious activity 

Installing suitable hardware to lock doors and windows (delay measures) 

and using a remotely monitored alarm system (detection and interdiction/

response measures) may also be useful in rented or leased spaces. 

5.9.4 Hotel Security Measures

Operational security measures, similar to those for the other types of 

commercial buildings, may be established to protect a hotel from blastand CBR-related events. Interior and exterior video surveillance systems 

may be established for loss prevention and security detection. Access 

to mechanical rooms, loading docks, roofs, and air vents should be 

restricted. Visitor screening and access control can be established during 

nighttime hours. 

Most procedural, preparedness, and master planning measures can 

also be applied. Of these, rehearsing internal emergency plans and 

establishing a liaison with local law enforcement and other first 

responders are especially important because they contribute to a 

coordinated response in an incident.

5.10 Incremental Integration of

Operational and Physical

Security Measures into a Risk 

Reduction Program: Flexibility

and Tradeoffs

Providing both an open, business-friendly environment and a 

safe and secure facility involves a delicate balance. Many diverse 

technologies are available to meet the security needs of a specific 

facility. The following flexibility and tradeoff considerations will help in 

the selection of incremental operational security measures.

Balance program improvements. Incremental increases in security 

should be implemented program-wide, with balanced deterrence, 

delay, detection and assessment, and interdiction/response measures. 

❍

❍
5-26 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

Randomly implemented technology may only have a limited impact on 

risk reduction. For example, establishing electronic security systems on 

the doors and not the windows of a facility does not significantly improve 

security. Similarly, establishing a hardened, gated vehicle entrance that 

can be bypassed by driving across a lawn does not appreciably improve 

protection from vehicle bombs. Facility owners should plan incremental 

improvements that decrease the level of risk and increase the overall level 

of protection. 

Use technology to improve detection effectiveness. Having a guard watching 

a bank of CCTV monitors without technology cueing systems usually 

limits detection. The integration of sensors with a CCTV system greatly 

increases the security effectiveness and the area that can be covered. 

Replacing or supplementing security guards with centralized monitoring 

station technology, rather then adding more personnel to monitor simple 

CCTV systems, may be a cost-effective incremental improvement.

Internet Protocol (IP)-based systems may provide flexibility and eliminate 

the need to integrate with other renovation projects. The rapid shift away 

from the classic, analog-only CCTV solutions to digital encoding and IP 

or network transport over open system connections presents existing 

building owners with new improvement opportunities. The installation 

of IP-based electronic security systems does not require the disruptive 

installation of long individual cable runs back to a central console. IPbased systems can generally be installed independent of major facility 

renovations.

Wireless systems may increase flexibility. In the past, installation of 

traditional wired external cameras or intrusion detection systems required 

thousands of dollars in installation costs and business disruptions 

from digging up roadways or parking lots to bury cables. This type of 

improvement had to be linked to other scheduled major renovations. 

Now, with IP-based systems and wireless links, installation may be less 

expensive and less disruptive, and can be completed independent 

of other scheduled renovations. However, wireless systems are more 

accessible to outsiders than wired systems and require appropriate 

protection, such as encryption, firewalls, and passwords to prevent 

hacking and tampering.

Not all hardware and software applications are compatible. Many proprietary 

systems cannot be integrated with other systems. They may also preclude 

future upgrades or the introduction of new capabilities. Facility managers 

should carefully project requirements and the necessary components of a 

complete system and plan for incremental improvements accordingly. 
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-27

Plan the implementation of variable security measures. After establishing 

a baseline of protection, facility managers must be able to increase 

their protective posture in response to an increased threat. While many 

physical measures have long lead times (like applying fragment retention 

film on windows), many operational security measures do not require 

major capital improvement and can be quickly modified as needed. The 

practiced and proven capability to implement variable security measures, 

such as closing underground parking, screening visitors, or limiting 

access, may provide facilities with the alternative of continuing operations 

rather than doing nothing or closing during periods of increased threat.

Install a high profile security measure early in the improvement sequence to 

publicly highlight increased security. If a facility has several equally effective 

improvements, schedule the high profile items, such as gated entry into 

the loading dock area or a public access control system, early to increase 

the public perception of security. 

5.11 Operational Security

Protection Measures

T he operational security measures identified in the preceding 

discussions are listed below as an example of measures that might 

be generated by the FEMA 452 process and implemented using 

this document, as discussed in Chapter 2. The measures are categorized 

into those that include physical protection and strengthening measures 

(5.11.1), and those that are entirely operational (5.11.2). The former are 

all included in the list that comprises the vertical axes of the matrices in 

Section 2.3.

5.11.1 Physical Protection and

Strengthening Buildings

1. Operational security measures related to blast and CBR events

Detection and assessment measures

Exterior intrusion detection systems

Interior intrusion detection systems

Video assessment and surveillance systems

Access control systems

Duress alarms

❍

❍

❍

❍

❍

❍
5-28 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

Interdiction/response measures

Guard force: detection/delay role

2. Additional operational security measures related to blast events

None.

3. Additional operational security measures related to CBR Events

Restrict access and secure and monitor outdoor air intakes

Light, secure, and monitor water service access points

Install intrusion detection sensors for all utility services to the 

building

Secure and monitor exterior mechanical spaces and 

equipment

Secure and monitor interior HVAC access points

These measures can be implemented independently from one another. 

5.11.2 Operational Measures

1. Operational security measures related to blast and CBR events

Detection and assessment measures

Exterior intrusion detection systems

Interior intrusion detection systems

Video assessment and surveillance systems

Access control systems

Vehicle inspection systems

Duress alarms

Mail/package screening procedures 

Interdiction/response measures

Guard force: detection/delay role

Guard force: response/interdiction role

Response force contingency planning

Procedural measures

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-29

Restricted areas: controlled areas

Restricted areas: limited areas

Restricted areas: exclusion areas

 Parking and traffic controls: separate employee and visitor 

parking

Parking and traffic controls: eliminate internal building 

parking

Parking and traffic controls: ensure natural surveillance

Parking and traffic controls: limit pedestrian access to 

parking areas

Restrict access to facility information

Encourage employee support

Preparedness measures

Develop a disaster preparedness plan

Conduct risk assessments

Develop mass notification systems

Conduct evacuation planning and shelter in place 

preparation

Monitor emergency systems and resources

Conduct training drills and exercises

Security master planning measures

Communicate and disseminate security master plan

Integrate into the facility construction or renovation 

planning

Benchmark or compare to related facilities

Test and evaluate the plan

Identify threats/hazards, assets, vulnerabilities, and risks

Establish security improvement implementation schedule

Establish security operating and capital budget

2. Additional operational security measures related to blast events

Establish an explosive detection program

Establish bomb threat procedures

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
5-30 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

Establish mail/package handling procedures

3. Additional operational security measures related to CBR events

Restrict access to, secure, and monitor outdoor air intakes

Light, secure, and monitor water service access points

Install intrusion detection sensors for all utility services to the 

building

Secure and monitor exterior mechanical spaces and 

equipment

Secure and monitor interior HVAC access points

Provide first responders appropriate hazardous materials 

equipment 

Restrict access to critical utility drawings

Prevent unauthorized access to and monitor roof areas

Establish CBR-related mail/package handling procedures

All of these measures can be implemented independently from one 

another. 

5.11.3 Operational Measures Categorized

into the Building Vulnerability

Assessment Checklist

The following list of operational mitigation measures reorganizes the 

preceding list (5.11.2) into the 13 sections of the Building Vulnerability 

Assessment Checklist in Appendix A of FEMA 452. Where applicable, 

the references in parentheses below refer to the respective sections in 

Chapters 4 and 5 where the item is discussed. 

1. Site

1.1 Vehicle inspections (5.2.5)

1.2 Guard force, detection/delay role (5.3.1)

1.3 Guard force, response/interdiction role (5.3.2)

1.4 Parking and traffic controls (5.4.2)

1.4.1 Control on-site parking 

❍

❍

❍

❍

❍

❍

❍

❍

❍

❍
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-31

1.4.2 Separate employee and visitor parking 

1.4.3 Eliminate internal building parking 

1.4.4 Ensure natural surveillance 

1.4.5 Limit pedestrian access to parking areas 

2. Architectural

2.1 Expedient sheltering in place (4.4.1.2)

2.1.1 Designating safe rooms, interior rooms having a 

lower air exchange rate

2.1.2 Identifying switches for all air handling units and 

fans for deactivation

2.1.3 Defining procedures for sheltering and for 

purging the building after plume passage

2.1.4 Establishing a building-wide notification system

2.1.5 Familiarizing occupants with the procedures and 

responsibilities 

2.2 Evacuation (4.4.1.2)

2.3 Using escape respirators (4.4.1.2)

2.4 Enhanced physical security (4.4.2.2)

2.4.1 Perform entry inspections

2.4.2 Employ video surveillance equipment

2.4.3 Institute mail screening procedures

2.4.4 Maintain operational security to building plans and 

signage

2.5 Mail/package screening (5.7.3, 5.8.2)

2.6 Restricted areas (5.4.1)

2.6.1 Controlled areas 
5-32 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

2.6.2 Limited areas 

2.6.3 Exclusion areas 

2.7 Prevent unauthorized access to and monitor roof areas 

(5.8.4)

3. Structural Systems

4. Building Envelope

5. Utility Systems (water, sewer, fuel, electrical service, telephone, fire 

alarm)

6. Mechanical Systems (HVAC)

6.1 Purging (expedient sheltering in place (4.4.1.2))

7. Plumbing and Gas Systems

8. Electrical Systems

9. Fire Alarm Systems

10. Communications and Information Technology Systems

10.1 Expedient sheltering in place

10.1.1 Defining building-wide notification system

10.2 Develop mass notification systems (5.5.3)

11. Equipment Operations and Maintenance

11.1 Provide first responders appropriate hazardous materials 

equipment (5.8.4) 

12. Security Systems (perimeter security, interior security, security 

system documents)

13. Security Master Plan

13.1 Detection and assessment measures

13.1.1 Vehicle inspection systems (5.2.5)
PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 5-33

13.1.2 Mail/package screening procedures (5.2.7)

13.2 Interdiction/response measures

13.2.1 Response force contingency planning (5.3.3)

13.3 Procedural measures

13.3.1 Restrict access to facility information (5.4.3)

13.3.2 Encourage employee support (5.4.4)

13.4 Preparedness measures

13.4.1 Develop disaster preparedness plan (5.5.1)

13.4.2 Conduct risk assessments (5.5.2)

13.4.3 Conduct evacuation planning and shelter in place 

preparation (5.5.4)

13.4.4 Monitor emergency systems and resources (5.5.5)

13.4.5 Conduct training drills and exercises (5.5.6)

13.5 Security master planning measures (5.6)

13.5.1 Communicate and disseminate 

13.5.2 Integrate into the facility construction or 

renovation planning 

13.5.3 Benchmark or compare to related facilities 

13.5.4 Test and evaluate the plan 

13.5.5 Identify threats/hazards, assets, vulnerabilities, and 

risks 

13.5.6 Establish security improvement implementation 

schedule 

13.5.7 Establish security operating and capital budget 

13.6 Additional operational security measures related to blast 

events
5-34 PRINCIPLES OF DESIGN FOR RISK REDUCTION RELATED TO OPERATIONAL SECURITY MEASURES 

13.6.1 Establish an explosive detection program (5.7.1)

13.6.2 Establish bomb threat procedures (5.7.2)

13.6.3 Establish mail/package handling procedures 

(5.7.3)

13.7 Additional operational security measures related to CBR 

events

 13.7.1 Restrict access to critical utility drawings (5.8.4)

These security enhancement operational increments can be implemented 

at any time, as they do not entail physical work in the building.
Bibliography

Bibliography

American Concrete Institute (ACI), 2005. ACI 318-05, Building Code 

Requirements for Structural Concrete and Commentary, ACI Committee 318, 

2005.

American Society of Heating, Refrigerating and Air-Conditioning 

Engineers (ASHRAE), 2004. ASHRAE Handbook – HVAC Systems and 

Equipment, ASHRAE, Inc., Atlanta, GA, January 2004.

ASHRAE, 2004. “Homeland Security for Buildings,” ASHRAE Satellite 

Broadcast, ASHRAE, Inc., Atlanta, GA, April 14, 2004.

American Society for Industrial Security (ASIS) International, 2000. 

Protection of Assets Manual, ASIS International, Alexandria, VA, www.

protectionofassets.com.

ASIS International, 2005. ASIS Business Continuity Guideline: A Practical 

Approach for Emergency Preparedness, Crisis Management, and Disaster Recovery, 

ASIS International, Alexandria, VA, www.asisonline.org/guidelines/

guidelinesbc.pdf.

American Society for Testing and Materials (ASTM), 2003. ASTM F 2248-

03, Standard Practice for Specifying an Equivalent 3-Second Design Loading for 

Blast Resistant Glazing Fabricated with Laminated Glass, ASTM International, 

West Conchohocken, PA, August 10, 2003.

Blewett, W.K., and Arca, V.J., 1999. Experiments in Sheltering in Place: How 

Filtering Affects Protection Against Sarin and Mustard Vapor, AD A365348, U.S. 

Army Chemical Biological Center, Aberdeen Proving Ground, MD, June 

1999.

Blewett, W.K., et al., 1996. Sheltering in Place: An Evaluation for the Chemical 

Stockpile Emergency Preparedness Program, AD A370441, U.S. Army Chemical 

Biological Center, Aberdeen Proving Ground, MD, May 1996.

Blewett, W.K., 2002. Fail-Safe Application and Design of Air Conditioners 

for NBC Collective Protection Systems, ECBC-TR-223, U.S. Army Chemical 

Biological Center, Aberdeen Proving Ground, MD, February 2002. 
II Bibliography

Centers for Disease Control and Prevention (CDC) and National Institute 

for Occupational Safety and Health (NIOSH), 2002. Guidance for Protecting 

Building Environments from Airborne Chemical, Biological, or Radiological 

Attacks, Atlanta, GA, www.cdc.gov/niosh/bldvent/2002-139.html.

Department of the Army, 1996. Expedient Sheltering In Place: An Evaluation 

for the Chemical Stockpile Emergency Preparedness Program, ERDEC-TR-336. 

U.S. Army Edgewood Research, Development and Engineering Center, 

Aberdeen Proving Grounds, MD, June 1996. 

Department of the Army, 2001. Field Manual 3-19.30, Physical Security, www.

army.mil/usapa/doctrine/Active_FM.html.

Department of Defense, 2003. UFC 4-010-01 Unified Facilities Criteria 

(UFC) DoD Minimum Antiterrorism Standards for Buildings, www.wbdg.org/

references/pa_dod.php.

Department of Health and Human Services, National Institute for 

Occupational Safety and Health (NIOSH), 2002. Guidance for Protecting 

Building Environments from Airborne Chemical, Biological, or Radiological 

Attacks, Publication No. 2002-139, May 2002.

Department of Health and Human Services, NIOSH, 2003. Guidance 

for Filtration and Air-Cleaning Systems to Protect Building Environments from 

Airborne Chemical, Biological, or Radiological Attacks, Publication No. 2003-

136, April 2003.

Department of State, 2003. Specification for Vehicle Crash Test of Perimeter 

Barriers and Gates, Revision A, SD-STD-02.01, Washington, DC, https://pdc.

usace.army.mil/library/BarrierCertification.

Federal Emergency Management Agency (FEMA), 2003. Reference Manual 

to Mitigate Potential Terrorist Attacks Against Buildings, Publication 426, 

FEMA, Washington, DC, www.fema.gov/plan/prevent/rms/rmsp426.

shtm.

FEMA, 2003. Incremental Seismic Rehabilitation of School Buildings (K–12),

Publication 395, FEMA, Washington, DC, www.fema.gov/plan/prevent/

rms/rmsp395.shtm.

FEMA, 2005. A How-To Guide to Mitigate Potential Terrorist Attacks Against 

Buildings, Publication 452, FEMA, Washington, DC, www.fema.gov/plan/

prevent/rms/rmsp452.shtm.
Bibliography III

FEMA, 2006a. Design Guidance for Safe Rooms and Shelters, Publication 453, 

FEMA, Washington, DC, www.fema.gov/plan/prevent/rms/rmsp453.

shtm.

FEMA, 2006b. Bomb Threat, FEMA, Washington, DC, www.fema.gov/

hazard/terrorism/exp/exp_threat.shtm.

FEMA, 2006c. Suspicious Packages and Letters, FEMA, Washington, DC, www.

fema.gov/hazard/terrorism/exp/exp_parcels.shtm.

FEMA, 2007. Site Urban Design for Security: Guidance Against Potential Terrorist 

Attacks, Publication 430, FEMA, Washington, DC, www.fema.gov/library/

viewRecord.do?id=3135.

Fennelly, Lawrence J., 1999. Handbook of Loss Prevention and Crime 

Prevention, Stoneham, MA, Butterworth-Heinemann, ISBN: 0-7506-9703-2.

Fennelly, Lawrence J., 2004. Effective Physical Security, Third Edition, 

Burlington, MA, Elsevier Inc., ISBN: 0-7506-7767-8.

Garcia, Mary Lynn, 2001. The Design and Evaluation of Physical Protection 

Systems, Stoneham, MA, Butterworth-Heinemann, ISBN: 0-7506-7367-2.

General Services Administration, 2002. Facilities Standards for 

Public Buildings Service, PBS-P100, General Services Administration, 

Washington, DC, www.gsa.gov/Portal/gsa/ep/channelView.

do?pageTypeId=8195&channelId=-15012.

General Services Administration, 2005. Facilities Standards for the Public 

Buildings Service, PBS-P100-2005, General Services Administration, 

Washington, DC, www.gsa.gov/Portal/gsa/ep/channelView.

do?pageTypeId=8195&channelId=-14201.

Kovacich-Halizobek, 2003. The Managers Handbook for Corporate Security, 

Butterworth-Heinemann, Woburn, MA, pp. 186-206.

Lawrence Berkeley National Laboratory (LBNL), 2003. Protecting Buildings 

from Biological or Chemical Attack: actions to be taken before or during a release,

Publication 51959, January 10, 2003.

Patterson, David G. III, CPP, CFE, CHS, 2004. Implementing Physical 

Protection Systems: A Practical Guide, USA, ASIS International, ISBN: 

1-887056-58-0.
IV Bibliography

Purpura, Philip P., 2002. Security and Loss Prevention, An Introduction, Fourth 

Edition, Woburn, MA, Butterworth-Heinemann, ISBN: 0-7506-7437-7.

Smilowitz, Robert, 2005. Designing to Resist Explosive Threats, prepared for 

the National Institute of Building Sciences, 2005.

Smilowitz, Robert, 2005. Retrofits to Resist Explosive Threats, prepared for the 

National Institute of Building Sciences, 2005.

U.S. Air Force, 2003. Entry Control Facilities Design Guide, www. afcee.

brooks.af.mil/dc/dcproducts/products.asp.

U.S. Army Corps of Engineers, 1999. “Design of Collective Protection 

Shelters to Resist Chemical, Biological, and Radiological (CBR) Agents,” 

Engineer Technical Letter 1110-3-498, Washington, DC, 24 February 1999. 

U.S. Army Corps of Engineers, 2001. Protecting Buildings and Their 

Occupants from Airborne Hazards (draft), Technical Instruction 853-01, 

October 2001.

U.S. Army Corps of Engineers, 2005. Security Engineering: Procedures for 

Designing Airborne CBR Protection for Buildings (draft), UFC 4-024-01, 4 

February 2005.