Several widely publicized attacks using biological and chemical threat agents in the last two decades have increased the urgency of protecting buildings and the materials, persons, and critical operations housed in them from these threats. To address that need, the Defense Advanced Research Projects Agency (DARPA) initiated the Immune Building Program to design, implement, and test a building protection system to make military buildings and their occupants less attractive targets for attack with biological or chemical threat agents. The Defense Threat Reduction Agency (DTRA), which is scheduled to assume responsibility for test beds1 and other results developed by DARPA’s Immune Building Program, asked the National Academies to convene a committee to consider existing work on preventing and mitigating the effects of airborne biological or chemical threat agents released within or infiltrated into built structures. The committee was asked to provide general principles that can be derived from those studies and existing test beds and to discuss the cost, benefit, and risks of potential protection schemes (see Appendix A for the complete Statement of Task). It is hoped that the results of this study will provide guidance for future investments in the Immune Building Program and other building protection efforts. The study committee included experts in technologies related to aerosols, biological and chemical warfare threats, detection and identification of biological and chemical threat agents, medical countermeasures, building design and operations, indoor airflow, and risk assessment (see Appendix B for committee member biographies). To gather information to address its task, the committee
heard about the purpose, feasibility, and capability of prior and current building protection schemes from representatives of various agencies and contractors involved in building protection programs and test beds. Based on these briefings, other documents, committee deliberations, and the committee’s collective expertise, this report highlights basic principles and lays out the variables and options to consider in designing and implementing building protection against biological and chemical threats.
FACTORS THAT INFLUENCE THE DESIGN AND IMPLEMENTATION OF BUILDING PROTECTION
Appropriate design and implementation of building protection is determined by multiple factors, including (1) threat types; (2) activities housed within the building and the mission of those activities; (3) the level of protection sought; (4) limitations posed by procurement type, quality of design and construction, maintenance, and wear and tear of the building; and (5) availability of resources.
Threat Types and Threat Agents
This report addresses two threat types: airborne releases of biological threat agents and airborne releases of chemical threat agents. “Threat agent” refers to the biological or chemical agent used in an attack. Biological threat agents considered here include bacteria (vegetative and spores), viruses, and products of organisms (toxins). Chemical agents considered here include those that can be dispersed as droplets or vapors. Because of the wide variety of biological and chemical agents, their symptomatic progressions, and associated fatality rates, the committee concluded that the best classification of threat agents is according to the two most critical properties related to current vulnerabilities in building protection—the ease of timely detection and the ease of timely treatment (see Figure S-1). This classification treats biological and chemical threats equally and addresses vulnerabilities from unknown threats. The ability to detect agents ranges from agents that are visible to the naked eye to those that are difficult or impossible to detect at levels of concern even with sophisticated equipment (see Figure S-1). The time window for treatment likewise varies from several days for threat agents that have long incubation or latent periods (slow-acting) to minutes for threat agents that produce rapid onset of illness or even death (fast-acting). Protection from difficult-to-detect and fast-acting threat agents is obviously the most challenging building protection scenario.
Activities and Mission
Buildings are constructed for different purposes and have different activities occurring within them. The need for protection varies among structures based
on the activities and missions they serve. For example, a structure used as a warehouse has different protection needs from one used to house troops or from one used as a critical operations control center or a hospital. For some buildings, a shut down of several days or several weeks for decontamination and recommissioning after a biological or chemical attack might be acceptable; in other structures, continuity of operations is paramount. Building use, with respect to its contents or occupants and their activities and mission, should play a large role in determining the type and level of protection needed.
Levels of Protection
Different strategies can be chosen to provide varying levels of protection across the spectrum, from no protection to strategies designed to totally eliminate the exposure of personnel to an agent. Active or passive strategies can be used to protect against threat agents. Passive measures provide protection by using approaches that do not include identification and detection technologies. For example, compartmentalization of spaces within the building, continuous cleansing of airstreams, visual recognition of threats and their effects, and relying on the integrity of the building as a whole to protect building occupants and contents are passive approaches to protection. Conversely, active measures use identification and detection technologies to recognize the presence of a threat agent and trigger a response, but as a result of technological and operational complexity, they have
more complex operation and higher risk of failure (including false positive and false negative rates) than passive strategies. The committee defined four levels of protection (LPs) that are not absolute but can be used to illustrate the components needed and options available for achieving desired protection goals. These levels of protection are qualitative, like the biosafety levels of microbiological and biomedical laboratories. In some circumstances, advanced protection options could be implemented without some of the low-level components.
Level of protection 1 (LP-1) is a low-level passive protection that has no sensors or additional options installed specifically to address biological and chemical threat agents. LP-1 is provided by a well-maintained building that has minimal air leakage through the exterior or interior of the building and has an HVAC (heating, ventilating, and air-conditioning) system with sufficient filtration and air exchange. Its construction methods are aimed at reducing particulates and chemical vapors in the finished structure.
Level of protection 2 (LP-2) is a high-level passive protection that does not utilize sensors. Options for achieving LP-2 include site selection, addition and upgrade of filters and adsorption units specific to biological and chemical threats, compartmentalization and overpressurization of building interiors, filtration of outdoor air, relocation of outdoor air intake vents, local air-washes,2 security protection in the surrounding area, and appropriate operational responses.
Level of protection 3 (LP-3) is a low-level active protection designed to detect and identify threat agents in time to execute therapeutic responses, but not quickly enough to warn occupants of the threat before exposure occurs. LP-3 requires a broad-spectrum detection and identification system that determines a threat agent within a time period necessary for operational response and treatment.
Level of protection 4 (LP-4) is a high-level active protection that can detect and identify a threat agent in time to mitigate the release. LP-4 can detect a threat early enough to make operational responses that prevent exposure, such as redirecting ventilation or donning personal protective equipment.
The difference between LP-1 and LP-2 is the inclusion of options specifically for protection from biological and chemical airborne threats in LP-2. The presence of detection and identification technologies for biological and chemical airborne threats defines LP-3 and LP-4. Automated response to threat detection separates LP-3 from LP-4. In general, active protection (LP-3 and LP-4) has fewer vulnerabilities when implemented in conjunction with passive protection. In this case, LP-3 or LP-4 is likely to include the virtues of LP-1 and LP-2.
Procurement Method and Building Type and Condition
Building procurement method and building type could limit the options that are available and the subsequent level of protection achieved in a building. Leased buildings that are partially or completely occupied by federal tenants likely offer security planners fewer options than federally owned buildings because of contractual constraints. Building type or interior layout affects a building’s vulnerability to threat agents because compartmentalization or the lack thereof can affect the spread of threat agents throughout the building.
A protection system designed to be integrated into newly constructed buildings is likely to have fewer limitations than a retrofit to an existing building. Building protection systems cannot be standardized or even generalized because the physical characteristics of buildings—their age, quality of construction, “leakiness”—and ongoing activities inside vary greatly within and across military and civilian sectors.
An integral part of the decision-making process when implementing a building protection system is cost consideration. The budget for building protection obviously limits the design and implementation of the protection system. Protection systems in newly constructed buildings could be more or less expensive than retrofitting an existing building depending on protection goals. In general, the former is less expensive than the latter given the same level of protection, especially if security needs are anticipated early in the pre-design and design phases and are identified in a threat and risk assessment.
All monetary costs associated with a protection system within its lifetime (life-cycle costs) need to be considered prior to its implementation. Fitting a building with protection from biological and chemical airborne threats would be unwise if a budget for operations and maintenance costs cannot be ensured. Inadequate long-term operation and maintenance budgets can defeat the performance objectives of the building and render investments in building protection worthless. Complete life-cycle costs of a building protection system include the initial costs of planning, design, and construction; cost of purchase, installation, and periodic and preventive maintenance; cost of operation, repair, and replacement of parts; and cost of upgrade of all its components. It should be noted that in government facilities, long-term budgeting and planning for costs of operation and maintenance are the exception rather than the rule.
Goals and Objectives for Protection
The goals and objectives of building protection vary depending on the mission and activities of each building. Clear definitions of goals and objectives for
building protection prior to designing, implementing, or deploying a protection system are essential so that appropriate components of the system and metrics for evaluation can be chosen. Because of variations in goals and in the factors that influence the feasibility of building protection, protection systems clearly cannot be designed generically. In defining goals and objectives, factors that influence building protection can provide guidance in determining the feasibility and limitations of desired protection options, thus determining the level of protection that can be achieved. The committee has developed three recommendations related to the design planning for building protection.
Recommendation 1: Clear and realistic building protection goals and objectives should be defined prior to deploying protection systems.
Recommendation 2: Building protection systems should be designed and implemented on a case-by-case basis for each structure to be protected.
Recommendation 3: Life-cycle costs should be planned for prior to deploying building protection systems.
COMPONENTS FOR BUILDING PROTECTION
A number of components can be used in building protection and applied in different combinations to achieve different levels of protection. Components that can be designed, modified, installed, or implemented to enhance building protection include the following:
Building design and planning strategies. These are passive strategies for enhanced physical security, such as choosing a site with adequate standoff from neighbors and protecting sensitive areas (such as fan rooms and filtration and pump rooms) from unauthorized access.
Heating, ventilating, and air-conditioning systems. HVAC can be used as a passive strategy that enhances protection from biological and chemical airborne threats through zoning, enhanced particulate filtration, the addition of continuous gas and vapor protection, and sensing and active control of airflows and air treatment devices. HVAC can also be used as an active strategy if it is coupled with validated sensor networks and used for threat mitigation.
Filtration. Using particulate and vapor adsorption filters with the highest feasible efficiency and replacing filters routinely are passive strategies to enhance protection for even those threat agents that cannot be detected.
Detection and identification technologies. These technologies are a part of an active protection strategy. They can include a sampling system to identify the threat agent; sensors that actively monitor the presence of threat agents, either periodically or continuously; and triggers that measure an event and initiate
another action. The use of these technologies singly or in combination could enhance the ability to respond to a threat by exposure prevention, mitigation, or treatment.
Operational responses. An overall concept of operations is an integral and necessary part of planning and preparation because inappropriate response actions can increase the hazard to occupants or missions. Operational responses could include active HVAC responses, shelter-in-place,3 use of personal protective equipment, or evacuation. Developing and practicing operational responses will maximize protection from biological and chemical threats.
A protection system can be designed to use passive or active approaches or both. Although active approaches, detection, and identification technologies are necessary to achieve LP-3 and LP-4, the components of passive protection (LP-1 and LP-2) are integral in these active systems. Sensor systems cannot perform to their best capacity without the high air quality provided by LP-1 and LP-2 systems. Similarly, LP-3 and LP-4 systems are not useful if operational plans are not available and in place to respond to alarms.
ROLE OF TEST BEDS AND EXISTING DEPLOYMENT
The defense community has developed test beds and field studies to evaluate the use of protection components, and it has active deployments that can provide further data. Because the factors that influence protection and protective components and technology vary from building to building and change over time, the ability to extrapolate results from test beds and deployments is limited. However, test beds, field studies, and deployments are valuable for evaluating the performance of individual sensors under realistic conditions and for evaluating the performance of integrated sensor systems and building protection systems (with or without sensors). One advantage of test beds is that they can be configured and challenged in ways not possible in an operational facility. Data collected on degradation, maintenance, and operational and life-cycle costs of building protection systems in test beds—and, in time, from operational buildings—can be used as points of reference for future analyses.
Because test facilities cannot faithfully duplicate specific operational buildings and data from actual biological or chemical attacks are sparse, modeling and simulation are necessary for assessing building protection. Data from test beds and existing deployments are important for developing and refining models, but uniform test methods for data collection in the test beds and deployments are necessary for data comparison.
Shelter-in-place means taking refuge in a small, interior room with no or few windows. See the following website for more information: http://www.redcross.org/services/disaster/beprepared/shelterinplace.html.
METRICS AND SYSTEM EVALUATION
A well-conceived building protection strategy includes metrics to measure the success of that strategy against building protection objectives. In addition to measuring the performance of a protection system, metrics can provide a common basis for comparison between different deployments and demonstrations. Protection metrics and operational performance metrics are used to gauge whether a building protection system is performing as planned. Protection metrics, which can include fraction of building exposed, fraction of occupants exposed, and lives saved, usually measure against the protection goals. Evaluation of these performance metrics requires either comprehensive testing in the facility or use of modeling tools to infer values for the desired metrics. Operational performance metrics, which may be less quantifiable than protection metrics, include response time, user acceptance, adaptability to new technologies, and management of disruptions caused by false alarms.
There is no universal set of metrics that can be used to assess protection systems of all buildings because of the uniqueness of each building, its use, and the goals and objectives of its protection. The goals and objectives shape the design and implementation of the system, as well as the appropriate metrics to measure system performance. The committee makes the following recommendation related to metrics:
Recommendation 4: Because goals and objectives for protection drive the choice of building protection system for each installation, metrics for a building protection system should be based on these same well-understood, clear goals and objectives.
A FRAMEWORK FOR DECISION MAKING
A systematic process that takes into account the building’s vulnerabilities and risks of attacks, its physical limitations, the budget, and options for protection using risk assessment and management approaches is needed to guide decision making and cost-benefit analysis for building protection. Because of the complex interactions of factors that determine the design of a building protection system, establishing a systematic process that weighs these factors against different protection options would help DTRA and other agencies to design appropriate protection systems. Such a process would help optimize protection within the physical limitations of the building, technological limitations of the components (such as the HVAC system, filters, and sensors), and financial constraints.
Recommendation 5: Prior to implementation of a building protection program, the Department of Defense (DOD) should establish a complete framework for building protection that guides decision making for each building to be protected. The decision-making framework should
consider the following steps: (1) defining the objectives of building protection; (2) preparing a threat assessment; (3) establishing a risk assessment; (4) developing a case-by-case plan for building protection; (5) conducting a risk management analysis; and (6) analyzing costs and benefits using appropriate metrics and modeling and simulation tools as needed. The complexity of steps in the framework and the time required for each step will depend upon the program and building protection objectives.
PLAN FOR THE FUTURE
Although buildings, threats, and vulnerabilities are unique and dynamic, there are some guiding principles for designing and implementing building protection. The level of protection needed depends on the goals and objectives defined, the vulnerabilities of the building, and the risks of attack, which could change over time as the building ages and the threat spectrum evolves. New threat types could be developed and deployed as scientific advances remove technical barriers. Cutting-edge building materials and techniques are being developed not only to provide basic protection but also to provide a “healthy” environment for building occupants. Predicting future needs and capabilities will be difficult, but designing today with likely future capabilities in mind can lower life-cycle costs of building protection systems and facilitate the utilization of future options.
Recommendation 6: Building protection should be designed to accommodate changing building conditions, emerging threats, and changing technology. Both the deployed building protection and the framework for deploying the building protection (proposed in Recommendation 5) should be reviewed periodically for sustained performance in light of changing resources and threats.
Protecting buildings from biological and chemical airborne threats is a complex matter subject to many variables. These variables have a striking impact on the feasibility and capability of the desired protection system. A well-defined strategy for protection, starting at the design phase and continuing through the deployment phase, combined with sound decision making, can lead to the best options for reaching building protection goals now and into the future. Although the principles of building protection might not change substantially over time, the technologies for protection and the threats will likely change; therefore, periodic reviews of strategies for building protection might be necessary.