Smoke-Control Systems and Homeland Security Using a building’s existing damper system to help mitigate the effects of a chemical, biological, or radiological (CBR) attack

building’s existing damper system can economizer dampers in areas likely to be affected. offer much in terms of protection in • Pressurize spaces adjoining areas in which the event of an airborne chemical, contaminants are known to be present. This helps biological, or radiological (CBR) attack. prevent movement to uncontaminated areas. Though nearly every building’s duct and damper Smoke-control zones provide an ideal map, while arrangement is unique, principles of sandwich-pressurization systems By LARRY FELKER fire and smoke control hold sway, provide a tool. Where smoke-conguiding virtually any design ap- Belimo Aircontrols (USA) Inc. trol systems are not installed, at least Sparks, Nev. proach. Mechanical-systems defloor isolation is needed. signers would do well to familiarize • Exhaust any possible contamithemselves with these principles.1 nants outside. Be aware of downwind intakes and In safeguarding a building against a CBR attack, the possibility of spread to other local areas and the a designer must consider potential attack points exposure of other people. Although codes require inside and outside the building, as well as options careful placement of exhaust and intake louvers, for action. Before involving the damper system, the older buildings may not comply. And as of this designer must have a thorough understanding writing, the location of smoke-exhaust-fan outlets is of the entire building. Information from sensors not covered by codes. and indicator lights, direct-digital-control- (DDC-) • Prevent the intake of contaminants if they are system displays, and manual and automatic alarms externally present. Shut down all fan systems as a must be readily available to facilitate the system’s default procedure. use by the building staff, firefighters, and police. Firefighter control stations should be in a protected room with its own air handler and, ideally, BASIC STRATEGIES separate CBR filtration. Remote modem control Following are basic strategies involving the use via the DDC system is an option. of air-handling units (AHUs) and fire and smoke Figure 1 shows the range of building size and systems in emergency situations: complexity. As can be seen in Figure 2, duct paths • Limit contaminant spread. Confine an inter- can be hidden and/or above ceiling tiles. Frequently, nally released agent to a specific area or floor with drawings are either absent or inapplicable, making the use of smoke or isolation dampers. retrofits difficult. Typically, trade-offs are needed to • Limit the introduction of externally released deal with cost-vs.-benefits-vs.-possibility-of-attack agents by shutting down air handlers and closing issues.

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Larry Felker is a mechanical engineer and the fire- and smoke-product manager for Belimo Aircontrols (USA) Inc. Previously, he was technical manager for the Western United States for Belimo and vice president of engineering for a Chicago controls distributor. He can be contacted at [email protected]. HPAC Engineering • July 2004

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Small office building Interlocked multibuilding complex High-rise

FIGURE 1. The range of building size and complexity. DESIGN GOALS

Establishing goals for dealing with a CBR attack is the responsibility of the architect, owner, or security consultant. Achieving those goals is the responsibility of the mechanical designer. Following are goals of a smoke-control and HVAC designer: • Prepare a written list of priorities, action items, and options for building operators. • Sense, alarm, and notify as necessary. Instructions over a public-address system should be loud and clear. Panic must be averted. • Ensure that maintenance personnel, building-automation- and security-system contractors, building security, police officers, and firefighters can access the control systems and that they have a copy of the written list of priorities. • Limit the exposure of occupants in any area of a building into which toxic agents are introduced. • Minimize the exposure of other occupants by preventing spread. • Avoid the exposure of emergency personnel. • Avoid spread to other buildings or outside areas in which people are present. • Minimize the overall contamination of the building. These goals usually are impossible to achieve simultaneously. For example, reducing exposure in one part of a building may be accomplished best through 2

ventilation and exhaust. But if the exhaust spreads toxic agents downwind, the agents may become entrained at the intake louver of another building. In some cases, such conflict may be unavoidable. Regardless, notifying and communicating with building opera-

tors is essential. DESIGN CONSIDERATIONS

lating chemical airflows. Hazard analysis considers wind, makeup air, the short-circuiting of airflow from supply to return diffusers within buildings and from exhaust to intake louvers outside buildings, variable-air-volume- (VAV-) fan involvement with pressure differences and in stairwells, mechanical exhaust, and general complex airflows. Figure 3 shows airflows in a singlezone VAV system with a central return. Any attempt to contain the transport of a contaminant in the space served while the fans continue to run will fail, with the exception of areas immediately pulled negative by exhaust fans. Contamination of this space by others could occur easily because of pressure differences from other air handlers, piston action by the elevators, or stack effect.

Before applying any form of damper control, a mechanical engineer must examine the building requirements thoroughly. This involves studying relevant standards and codes and talking with the TACTICS Depending on the air-handling sysowner and architect. The engineer also needs to study the tem, different tactics may be applied. Tactic: Shelter in place. All fans are building components, zones and airflow paths, normal movement of people and shut down, and the smoke-control dampers are closed. materials into and out of This passive prothe structure, occupancy tection method is levels, lobbies, elevators, the default tactic parking garages, winwhen informed dedows, doors, and exiting cisions are impossiroutes. ble to make and Code officials must when a CBR rebe aware of exceptions lease has taken to existing codes that place outside a may need to be taken building. advantage of for the Benefits: Existing overall design goals to switches on the be met. firefighter control CBR agents are most panel can be emlikely to be particulate ployed. Crossor aerosols that move training police and with standard ventilafirefighters is possition air. Gas-tracer tests ble, with both poshelp determine design sessing keys. Police tactics that need to are on patrol and be employed. Smoke generally expected generators produce cold to be in the buildchemical smoke, which FIGURE 2. Interpenetrating air ing sooner. is appropriate for simu- systems.

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are pressurized. Benefits: Not all firefighting Stack effect stations have a RP RAF hand/off/auto Elevator EA REA doors switch for each RA Wind Other air SA MA SAF air handler. OA handlers VAV Retrofits using 5-15% networked conduct leakage Combustion-air trols allow a infiltraion relatively inexVAV VAV pensive method to gain control. EA = Exhaust air RAF = Return-air fan SAF = Supply-air fan MA = Mixed air REA = Return exhaust air VAV = Variable-airFloor dampers OA = Outside air RP = Relief plenum volume box are not required RA = Return air SA = Supply air in most existing FIGURE 3. Airflows in a single-zone VAV system with a central return. codes. Where DDC has been Tactic: Zone isolation. The contami- installed, only slight modifications nated zones are shut down, while the should be necessary to achieve goals. other zones are left running. A default (Note: Old pneumatically controlled zone is a single floor. One zone or floor buildings may need extensive modifishould be evacuated while the others cations.) 5-15% duct leakage

Mechanical exhaust Exfiltration

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Tactic: Zone pressurization. A contaminated area is isolated with the use of smoke-control dampers. Air handlers can be shut down as necessary. Typically, only the contaminated zone is exhausted, and the adjacent zones are placed in full supply with exhausts closed. Benefits: Ideal where full smoke-control systems exist. The control panel lends itself to isolation without modification. Hand/off/auto switches already exist. Test switches allow for good maintenance checks. ENHANCED PASSIVE PROTECTION AND OTHER APPROACHES

When a system is well-understood, it can be used in special operation modes. For example, a unit known to be far from any source of contaminant can be put in 100-percent-outside-air-intake mode to provide clean air. Intermediate units can be shut down, or VAV-box

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dampers in selected zones can be run fully closed. Then, units near an externally released contaminant can be put in return-air or relief-fan mode only. This puts a positive pressure on both the outside-air intake and exhaust-air dampers to keep contaminants from entering. The use of a DDC system requires knowledge of operations and access codes. Police and firefighters cannot make use of a DDC system without trained stationary engineers or building-security personnel present. Training and operation procedures for a building can be established easily. VAV zone dampers can be employed in zone isolation. Coordination between security or police and DDC operators is

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required to identify zones and dampers and to override dampers. Police, firefighters, and building operators must think strategically before taking action. Reflexively shutting down all AHUs might cause more problems than allowing pressurization and exhaust to continue to clean air. Placing systems in smoke mode may spread toxic agents, as elevator doors may be open. Some fire procedures, such as the recall of elevators to the ground floor, are inappropriate. DAMPER CONSIDERATIONS

Air Movement and Control Association (AMCA) Class I dampers are the replacement damper of choice for existing buildings and new construction.

Class II and III dampers leak more and save little money, while older Class IV dampers leak excessively. Leakage-rated dampers typically are UL555- and UL555S-listed combination fire/smoke dampers. (See www.amca.org/crp/ products/productselect.asp for certification information.) Economizer and floor-isolation dampers need not be listed, but leakagerated dampers should be considered. Higher-quality dampers can be used with standard modulating actuators. When an AHU is to be used to exhaust smoke or contaminated air, the possibility of contamination of outside air via the recirculation-air duct needs to be examined.

▼ National Bioterrorism Hospital Preparedness By ANDREW J. STREIFEL, MSPH University of Minnesota Minneapolis, Minn. he Department of Health and Human Services’ Health Resources and Services Administration (HRSA) developed the National Bioterrorism Hospital Preparedness Program to upgrade the nation’s health-care system in the event of bioterrorism, outbreaks of infectious disease, and other public-health threats and emergencies. The program requires each state to establish a system allowing the triage, treatment, and initial stabilization—above the current daily staffed-bed capacity—of 500 adult and pediatric patients with acute illnesses or trauma resulting from a chemical, biological, radiological, nuclear, or explosive incident per million in population. In addition, the program requires: • Participating hospitals to have the capacity to maintain in negative-pressure isolation at least one suspected case of a highly infectious disease (e.g., small pox, pneumonic plague, severe acute respiratory syndrome [SARS], influenza, hemorrhagic fevers) and any febrile patient with symptoms indicative of a potentially highly communicable disease. • Each state to identify at least one regional health-care facility capable of supporting in negative-pressure isolation the initial evaluation and treatment of at least 10 adult and pediatric patients at a time. All of this can be achieved with existing natural smoke/fire zones in hospitals. As shown in the accompanying article, these zones can be manipulated to achieve a suite of rooms capable of exhausting air to the outdoors and creating a depressurized zone.

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Ventilation can be controlled to limit the transmission of an internally released infectious agent without affecting the firemanagement function. These systems can be used to control pressures in an effort to minimize exposure. Hospitals should have airborne-infection-isolation (AII) rooms inventoried and assessed to meet Centers for Disease Control and Prevention criteria for pressure, air changes per hour, and filtration. Hospitals also should be evaluated for surge-capacity planning. Smaller (fewer than 25 beds) hospitals may require only minimal planning because the HRSA recommends that each hospital have the capacity for at least one AII room. This requirement often is met with portable “negative-pressure” machines; however, few hospitals have written plans for using them. Depending on the modernity of the mechanical systems in a hospital, the goal of achieving a depressurized exhausted area may be realized without major capital cost. The use of personal protective equipment must be part of planning for all aspects of biological exposure to infectious agents. Ventilation must be carefully controlled to avoid internal problems. For example, if a building were to be depressurized (greater than 0.10 in. wg), a tremendous amount of untreated air would enter the building. Prudent continuity planning for disastrous events requires a team effort. A member of HPAC Engineering’s Editorial Advisory Board, Andrew J. Streifel, MSPH, is a hospital-environment specialist for the University of Minnesota’s Department of Environmental Health & Safety.

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SA

RA

Open damper

Pressurized zone

Closed damper

Closed damper

Smoke zone

Open damper

Open damper

Pressurized zone

Closed damper

FIGURE 4. Floor-isolation and smoke dampers at shaft penetrations in sandwich-pressurization systems can be used for both smoke control and CBR isolation.

cator lights, while in many of those that do, an entire zone or floor is indicated by one light. Proximity switches, auxiliary switches on actuators, and damper-blade whisker switches are wired in series with the light. As a monitoring system for zone smoke control, switches are relatively inexpensive and provide an effective maintenance and commissioning tool. OTHER CONSIDERATIONS

A relief-fan system cannot cross-contaminate outside air. A return-air system could contaminate supply air, however. Outside-air fans, relief fans, and exhaustair dampers are of no concern. Floor-isolation and smoke dampers at shaft penetrations in sandwich-pressurization systems can be used for both smoke control and CBR isolation (Figure 4). (Note: Smoke-control systems may not be effective for heavy chemical agents, which tend to fall, not rise, as smoke does.) CONTROL PANELS

Firefighter control stations must be clearly marked and easy to use (Figure 5). Relatively complicated stations require study for expert control to be achieved. Although a “kill switch” can be added to a panel to allow single-switch shutdown of all systems, the flexibility of individual switches is preferred so that selective strategies can be applied. Operators should have prepared plans for different situations, as they are not likely to be pressure-control experts. Individual control can be expensive, particularly in large, complex buildings. Cost and potential benefits, then, must be weighed. A reasonable balance can be achieved. Most control systems do not have indi-

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tionary engineers, and occupants, thus, need to be knowledgeable about safety within buildings and take responsibility. Instituting a training program or appointing a task force or review committee might be a good start. While the possibility of a CBR attack exists, fire likely still is a bigger threat to a building’s occupants. A smoke-control system’s primary purpose is to allow people to escape in the event of a fire. That goal should not be compromised by other security efforts. CONCLUSION

The use of a smoke-control system may allow low-cost mitigation of the effects of a CBR attack. However, not every attack can be prevented, nor can occupants be totally protected. Placing isolation, economizer, and smokecontrol dampers under the control of a firefighter station may help, however. To more of a degree than in the past, architects must design buildings from the inside out. What’s more, airflow is more important and not just the responsibility of the mechanical engineer. Given energy and indoor-air-quality standards for design, the need for smoke and fire protection, and additional security issues, mechanical systems must be

The economizer sequence of operation and damper control may be under firealarm-isolated hard-contact relay control. In such a case, the alarm panel must be able to operate dampers. Alarm companies rarely are qualified to interface directly. The drawings, therefore, must indicate who is to provide what wiring at which terminal strip to separate trades and responsibilities. If the economizer is fully controlled by the temperature-control DDC system, then a clear sequence must be achievable via interface switches. If water coils can Supply-air fan Return-air fan On On freeze, then the seAuto Auto quence in the event Off Off of purge evacuation must protect the coil SA RA Open Open damper, damper, Auto Auto by opening valves. Floor 5 Floor 5 Closed Closed (The design must provide three-way SA RA Open Open valves and, if necesdamper, damper, Auto Auto sary, runaround Floor 4 Floor 4 Closed Closed pumps.) System mainteSA RA Open Open nance is a problem damper, damper, Auto Auto Floor 3 Floor 3 in most buildings. Closed Closed With budget constraints, operational Light on Switch checks often are deferred until failure. FIGURE 5. Firefighter control stations must be clearly marked Building owners, sta- and easy to use. HPAC Engineering • July 2004

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▼ given higher priority and a greater share of budgets. The purpose of commercial buildings is to provide healthy, comfortable, and productive environments. Engineers and architects must cooperate with one another to reach those goals.

Hospital-Preparedness Funds By ANDREW J. STREIFEL, MSPH he National Bioterrorism Hospital Preparedness Program is providing funding to all 50 states; the District of Columbia; the nation’s three largest municipalities (New York City, Chicago, and Los Angeles County); the commonwealths of Puerto Rico and the Northern Mariana Islands; the territories of American Samoa, Guam, and the U.S. Virgin Islands; the Federated States of Micronesia; and the republics of Palau and the Marshall Islands. In Minnesota, a portion of this funding is being used to assess the isolation capacity of the state’s 141 hospitals. The inventory will determine if pressure relationships (0.01 in. wg) are appropriate in airborne-infection-isolation rooms. The survey will ask questions about the number of beds, exhaust capability, negativepressure machines/operational protocols, surge-capacity planning, and training. All state health departments have a bioterrorism hospital-preparedness coordinator. Contact the one in your state for more information.

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REFERENCE

1) Klote, J.H., & Milke, J.A. (2002). Principles of smoke management. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers. BIBLIOGRAPHY

AMCA. (1993). Fire, ceiling and smoke dampers application manual. AMCA Publication 503-93. Arlington Heights, IL: Air Movement and Control Association International Inc. ASHRAE. (2003). Report of presidential ad hoc committee for building health and safety under extraordinary incidents

on risk management guidance for health, safety and environmental security under extraordinary incidents. Available at xp20 .ashrae.org/about/extraordinary.pdf. NIOSH. (2003, April). Guidance for filtration and air-cleaning systems to protect building environments from airborne

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chemical, biological, or radiological attacks. Available at www.cdc.gov/niosh/docs/ 2003-136/pdfs/2003-136.pdf. For HPAC Engineering feature articles dating back to January 1992, visit www.hpac.com.

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