Smoke Management Fundamentals INTRODUCTION

This section describes objectives, design considerations, design principles, control applications, and acceptance testing for smoke control systems. A smoke control system modifies the movement of smoke in ways to provide safety for the occupants of a building, aid firefighters, and reduce property damage. References are at the end of this section which include smoke control codes.

Smoke is a highly toxic agent. Information from U. S. Fire Administration estimates that in 1989 approximately 6,000 fire fatalities occurred in the United States and 80 percent of these deaths were from inhalation of smoke. Furthermore, an additional 100,000 individuals were injured, and fire damage exceeded $10 billion.

Long term effects on humans from repeated exposure to smoke and heat is a major concern. According to the National Institute of Building Sciences, "The significance of time of human exposure is the fact that brief exposure to a highly toxic environment may be survived, while a lengthy exposure to a moderately toxic environment can lead to incapacitation, narcosis, or death."1 The primary toxic agent produced in building fires is carbon monoxide. Other toxic agents include hydrogen cyanide, hydrogen chloride, sulphur dioxide, acrolein, aldehydes, carbon dioxide, and a variety of airborne particulates carrying heavy metals (antimony, zinc, chromium, and lead).

Early smoke control systems used the concept of passive control to limit the spread of fire and smoke. This method evolved from early fire containment methods used in high rise buildings. With passive control, HVAC fans were shut down and dampers were used to prevent smoke from spreading through ductwork. This application required very-low-leakage dampers. Fire walls or barriers, used to prevent the spread of fire, were enhanced to prevent the spread of smoke.

In the late 1960s, the concept of active smoke control was created. With active control, the HVAC fans activate to prevent smoke migration to areas outside of fire zones. This method includes pressurized stairwells and a technique sometimes called the pressure sandwich or zoning in which the floors adjacent to the fire floor are pressurized and the fire floor is exhausted.

DEFINITIONS

AHJ: Authority Having Jurisdiction.

ASHRAE: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

Atrium: A large volume space within a floor opening or series of floor openings connecting two or more stories, covered at the top of the series of openings, and used for purposes other than an enclosed stairway, elevator hoistway, escalator opening, or utility shaft.

Buoyancy: The tendency of warmer air or smoke to rise when located in cooler surrounding air. Caused by the warmer air being less dense than the cooler air, resulting in pressure differences.

Combination fire and smoke damper: A device that resists the passage of air, fire, and smoke and meets the requirements of UL 555, Standard for Fire Dampers, and UL 555S, Standard for Leakage Rated Dampers for Use In Smoke Control Systems.

Covered mall: A large volume space created by a roofed-over common pedestrian area, in a building, enclosing a number of tenants and occupancies such as retail stores, drinking establishments, entertainment and amusement facilities, and offices. Tenant spaces open onto, or directly communicate with, the pedestrian area.

Expansion: The increase in the volume of smoke and gas caused by the energy released from a fire.

Fire damper: A damper that meets the requirements of UL 555, Standard for Fire Dampers, and resists the passage of air or fire.

FSCS: Firefighters' Smoke Control Station.

Large volume space: An uncompartmented space, generally two or more stories in height, within which smoke from a fire, either in the space or in a communicating space, can move and accumulate without restriction. Atria and covered malls are examples of large volume spaces.

NFPA: National Fire Protection Association.

Pressure sandwich: An application where only the zones adjacent to a smoke zone are pressurized and the fire zone is exhausted to limit the spread of smoke.

Smoke: The airborne solid and liquid particulates and gases developed when a material undergoes pyrolysis or combustion, together with the quantity of air that is entrained or otherwise mixed into the mass.

Smoke Control System: A system that modifies the movement of smoke in ways to provide safety for the occupants of a building, aid firefighters, and reduce property damage.

Smoke Management System, Active: A system that uses fans to produce airflows and pressure differences across smoke barriers to limit and direct smoke movement.

Smoke Management System, Passive: A system that shuts down fans and closes dampers to limit the spread of fire and smoke.

Smoke Control Zone: An indoor space enclosed by smoke barriers, including the top and bottom, that is part of a zoned smoke control system.

Smoke Damper: A device designed to resist the passage of air or smoke that meets the requirements of UL 555S, Standard for Leakage Rated Dampers for Use In Smoke Control Systems.

Stack Effect: A difference in density caused by temperature-pressure differences between the air inside a building and the air outside a building. The air inside the building moves upwards or downwards depending on whether the air is warmer or colder, respectively, than the air outside.

UL: Underwriter's Laboratories Inc.

UPS: Uninterruptible Power Supply

Smoke Management Fundamentals

OBJECTIVES

Designing a smoke management system requires agreement on the system objectives. The following is a partial list of potential system objectives:- Provide safety for the occupants - Extend egress time - Provide safe egress route - Provide safe zones (tenable environment) - Assist firefighters - Limit property damage - Limit spread of smoke away from fire area - Clear smoke away for visibility - Provide elevator usage during fires as an egress route for the handicapped

DESIGN CONSIDERATIONS

General

Four points must be stressed in developing a smoke management system:

1. The smoke management system can be properly designed only with agreement on the objectives of the system.

2. The smoke management system must be designed as a complete mechanical control system that is able to function satisfactorily in the smoke management mode. The smoke management system should be designed independently of the HVAC system and then integrated, where feasible, without sacrificing functionality of the smoke control system.

3. The smoke management system must be designed to be reliable, simple, and maintainable.

4. The smoke management system must be designed to minimize the risks of failure and must be tested periodically. Sensors providing status of operation and building automation controls providing system monitoring and printed records can assist in the testing process.

Present smoke control systems use active methods and follow two basic design approaches to preventing the movement of smoke from the fire zone:

- Providing static pressure differences across penetrations in smoke barriers, such as cracks around doors.

- Providing adequate velocity of air through large openings in smoke barriers, such as doors in an open position.

Although these two methods are directly related, it is more practical to use one or the other to design with and measure the results.

Methods used to activate smoke control systems require careful consideration. For zoned smoke control, care must be taken in using smoke detectors to initiate a pressurization strategy. If a smoke detector that is not in the smoke zone goes into alarm, the wrong smoke control strategy will be employed. Alternatives for system initiation may not solve the problem. If a pull station is activated from a nonfire zone, the wrong smoke control strategy will be employed.

Any alarm activation of a smoke management system that is common to all strategies in the building, such as stairwell pressurization, atria, and exhaust, is acceptable.

For a smoke management system to function reliably, building leakage must be controlled during and after construction. Any penetrations of smoke barriers and walls used for pressurization must be carefully considered in order to maintain the intended smoke control.

Smoke management typically includes control of fires by automatic sprinklers. Designing smoke management systems for sprinklered buildings is quite practical. However, designing smoke management systems for buildings that do not have sprinkler systems is extremely difficult. Complicating the design task are problems with estimating the fire size and dealing with higher static pressures (or airflows).

Smoke vents and smoke shafts are also commonly used as a part of the smoke management system to vent pressures and smoke from fire areas; however, their effectiveness depends on the nearness of the fire, the buoyancy of the smoke, and other forces driving the smoke.

Layout of System

Smoke management equipment should be located in a building where it can best facilitate smoke control for various building layouts. The following guidelines apply:

Follow the drawings and specifications for the job. Locate the smoke controls near the mechanical equipment used to control the smoke. Try to minimize the length of runs for sensors, actuators, power, and communications

wiring in order to reduce the possibility of wiring being exposed to areas where there might be a fire.

Appendix A of NFPA 92A describes an example of a Firefighters' Smoke Control Station (FSCS). The FSCS allows firefighters to have control capability over the smoke control equipment within the building. The FSCS must be able to show clearly if the smoke control equipment is in the normal mode or the smoke control mode. The example in NFPA 92A includes location, access, physical arrangement, control capability, response time, and graphic depiction. This example is for information only and is not a requirement.

Codes and Standards

The integration of fire alarm and smoke control is covered in UL 864, Standard for Control Units for Fire-Protective Signaling Systems. Compliance with this UL standard for engineered smoke control systems requires the following:

- Compliance with NFPA 92A, Recommended Practice for Smoke Control Systems

- End-of-process verification of each control sequence

- Annunciation of any failure to confirm equipment operation

- Automatic testing of dedicated smoke control systems

Controls that meet UL Standard 864 are listed under UL Category UUKL. Standby power and electrical supervision items listed in UL864 are optional for smoke control systems.

According to NFPA 92A, control sequences should allow smoke control modes to have the highest priority; however, some control functions should not be overridden. Examples of these functions are duct-static high pressure limit control and shutdown of the supply fan on detection of smoke in a supply air duct.

Manual override of automatic smoke control systems should be permitted. In the event of multiple alarm signals, the system should respond to the first set of alarm conditions unless manually overridden.

All related energy management functions should be overridden when any smoke control mode is activated by an actual alarm or during the testing process.

During the planning stage of a project, design criteria should include a procedure for acceptance testing. NFPA 92A states that, "Contract documents should include operational and acceptance testing procedures so that all parties-designer, installers, owner, and Authority Having Jurisdiction (AHJ)-have a clear understanding of the system objectives and the testing procedure."2

Legal authority for approval of smoke control systems is from the Authority Having Jurisdiction (AHJ). The AHJ uses local building codes as its primary standard. Local building codes are established using several reference standards or codes including the following:

- Model Building Codes:

- Building Officials and Code Administrators International (BOCA), Inc.

- International Conference of Building Officials (ICBO)

- Southern Building Code Congress, Inc. (SBCCI)

- Western Fire Chiefs Association (WFCA)

- National Mechanincal Code (NMC)

- American with Disabilities Act (ADA)

- National Fire Protection Association (NFPA) Standards:

- NFPA 92A, Recommended Practice for Smoke Control Systems

- NFPA 92B, Guide for Smoke Management Systems in Malls, Atria, and Large Areas

- NFPA 90A, Installation of Air Conditioning Systems

- Underwriters Laboratories (UL) Standards:

- UL 555, Standard for Fire Dampers and Ceiling Dampers

- UL 555S, Standard for Leakage Rated Dampers for Use In Smoke Control Systems

- UL 864, Standard for Control Units for Fire-Protective Signaling Systems (UL Category UUKL)

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Smoke Management Fundamentals

DESIGN PRINCIPLES

Causes of Smoke Movement

The movement or flow of smoke in a building is caused by a combination of stack effect, buoyancy, expansion, wind velocity, and the HVAC system. See Figure 1. These items basically cause pressure differences resulting in movement of the air and smoke in a building.

Fig. 1. Factors Affecting the Movement of Smoke.

Before controls can be applied, it is necessary to first understand the overall movement of smoke.

Stack Effect

Stack effect is caused by the indoor and outdoor air temperature differences. The temperature difference causes a difference in the density of the air inside and outside of the building. This creates a pressure difference which can cause a vertical movement of the air within the building. This phenomenon is called stack effect. The air can move through elevator shafts, stairwells, mechanical shafts, and other vertical openings. The temperature-pressure difference is greater for fire-heated air which may contain smoke than it is for normal conditioned air. For further information of stack effect refer to the Buiding Airflow Systems Control Applications section.

When it is colder outside than inside, there is a movement of air upward within the building. This is called normal stack effect. Stack effect is greater for a tall building than for a low building; however, stack effect can exist in a one-story building. With normal stack effect, air enters the building below the neutral plane, approximately midheight, and exits above the neutral plane. See Figure 2. Air neither enters nor exits at the neutral plane, a level where the pressures are equal inside and outside the building.

Note: Arrows Indicate Direction of Air Movement

Fig. 2. Smoke Movement Caused by Normal or Reverse Stack Effect.

When it is colder inside than outside, there is a movement of air downward within the building. This is called reverse stack effect. With reverse stack effect, air enters the building above the neutral plane and exits below the neutral plane.

The pressure difference across the building's exterior wall caused by temperature differences (normal or reverse stack effect) according to Design of Smoke Management Systems published by ASHRAE is expressed as:3

Where:

= Pressure difference in. wcKs = Coefficient, 7.64To = Absolute temperature of outdoor air, Rankine (R) Ti = Absolute temperature of air inside the shaft, Rankine (R) h = Distance above the neutral plane, ft

Buoyancy

Buoyancy is the tendency of warm air or smoke to rise when located in cool surrounding air. Buoyancy occurs because the warmer air is less dense than the cooler air, resulting in pressure differences. Large pressure differences are possible in tall fire compartments.

The buoyancy effect can cause smoke movement through barriers above the fire and through leakage paths in walls. However, as smoke moves away from the fire, its temperature is lowered due to heat transfer and dilution; therefore, the effect of buoyancy decreases with distance from the fire.

The pressure difference between a fire zone and the zone above can be expressed as:3

Where:

= Pressure difference in. wcKs = Coefficient, 7.64To = Absolute temperature of surrounding air, Rankine (R) Tf = Absolute temperature of the fire compartment, Rankine (R) h = Distance above the neutral plane, ft

Expansion

The energy released by fire can move smoke by expansion of hot gas caused by the fire. A fire increases the volume of the heated gas and smoke and causes pressure in the fire compartment. If there are several openings, the pressure differences are small.

The volumetric flow of smoke out of a fire zone is greater than the airflow into the fire zone. This situation is expressed as:3

Where:

Qout = Volumetric flow rate of smoke out of the fire compartment, cfmQin = Volumetric flow rate of air into the fire compartment, cfmTout = Absolute temperature of smoke leaving the fire compartment, Rankine(R) Tin = Absolute temperature of air into the fire compartment, Rankine (R)

For tightly sealed fire zones, the pressure differences across the barrier caused by expansion can be extremely important. Venting or relieving of pressures created by expansion is critical to smoke control. Venting is often accomplished with smoke vents and smoke shafts.

The relationship between volumetric airflow (smoke) and pressure through small openings, such as cracks, is as:3

Where:

= Pressure difference across the flow p in. wcQ = Volumetric flow rate, cfmKf = Coefficient, 2610A = Flow area, sq ft

Wind Velocity

Wind velocity can have a significant effect on the movement of smoke within a building. The infiltration and exfiltration of outdoor air caused by wind can cause the smoke to move to areas other than the fire compartment. Positive pressures on the windward side cause infiltration; negative pressures on the leeward side cause exfiltration. The higher the wind velocity, the greater the pressure on the side of the building. In general, wind velocity increases with the height from the ground. The effects of wind on a tightly constructed building can be negligible. However, the effects can be significant for loosely constructed buildings or buildings with open doors or windows.

If a window breaks on the windward side of a building because of a fire, smoke can be forced from the fire compartment to other areas of the building, endangering lives and dominating air movement. If a window breaks on the leeward side, the wind can help to vent the smoke from the fire compartment to the outside.

PW = CW x KW x V2

The pressure caused by wind on a building surface is expressed as:3

Where:

PW = Wind pressure, in. wcCW = Dimensionless pressure coefficient KW = Coefficient, 4.82 x 10-4

V = Wind velocity, mph

The pressure coefficient, Cw, varies greatly depending on the geometry of the building and can vary over the surface of the wall. Values range from 0.8 to 0.8, with positive values for windward walls and negative values for leeward walls.

HVAC

HVAC systems can provide a means for smoke transport even when the system is shut down (e.g., a bypass damper venting smoke). Utilizing the HVAC system in smoke control strategies can offer an economic means of control and even meet the need for zone pressurization (e.g., pressurizing areas adjacent to a fire compartment).

Control of Smoke

Smoke control uses barriers within the building along with airflow produced by mechanical fans to contain the smoke. For some areas, the pressure difference across the barrier can be used to control the smoke. Where the barriers have large penetrations, such as door openings, it is easier to design and measure the control system results by using airflow methods. Both methods, pressurization and airflow, are discussed in the following.

In addition to life safety requirements, smoke control systems should be designed to provide a path to exhaust the smoke to the outdoors, thereby relieving the building of some of the heat of the fire and the pressure of the gas expansion.

Pressurization

Pressurization of nonsmoke areas can be used to contain smoke in a fire or smoke zone. Barriers are required between the nonsmoke areas and the area(s) containing the smoke and fire. For the barrier to perform correctly in a smoke control system, a static pressure difference is required across any penetrations or cracks to prevent the movement of smoke. Figure 3 illustrates such an arrangement with a door in a wall. The high pressure side can act as a refuge or an escape route, the low pressure side as a containment area. The high pressure prevents any of the smoke from infiltrating into the high pressure area.

Fig. 3. Pressurization Used to Prevent Smoke Infiltration.

Guidelines for pressurization values are found in NFPA 92A, Recommended Practice for Smoke Control Systems. Table 1 indicates minimum design pressure differences across smoke barriers. The design pressure difference listed is the pressure difference between the smoke zone and adjacent spaces while the affected areas are in the smoke control mode. The smoke control system should be able to maintain these minimum pressure differences while the building is under typical conditions of stack effect and wind. This table is for gas temperatures of 1700F adjacent to the barrier. To calculate pressure differences for gas temperatures other than 1700F, refer to data in NFPA 92A.

Table 1. Suggested Minimum Design Pressure Differences Across Smoke Barriers.

Pressure differences can vary because of fan pulsations, wind, and doors opening and closing. Short-term variances, from the suggested minimum design pressure differences in Table 1, do not seem to have significant effects on the protection furnished by a smoke control system. There is no actual definitive value for short-term variances. The value depends on the

tightness of the construction and the doors, the toxicity of the smoke, the airflow rates, and the volume of the protected space. Occasional variances of up to 50 percent of the maximum design pressure difference can be allowed in most cases.

Table 2 lists values for the maximum pressure differences across doors. These values should not be exceeded so that the doors can be used when the pressurization system is in operation. Many door closers require less force when the door is initially opened than the force required to open the door fully. The sum of the door closer forcE and the pressure imposed on the door by the pressurization system combine only until the door is opened sufficiently to allow air to move easily through the door. The force imposed by a door closing device on closing a door is often different from that imposed on opening a door.

Note: Total door opening force is 133N. Door height is 2.13m. The distance from the doorknob to the knob side of the door is 0.076m.

Table 2. Maximum Pressure Difference Across Doors in In. wc (NFPA 92/92A).

The door widths in Table 2 apply only for doors that are hinged at one side. For other arrangements, door sizes, or for hardware other than knobs (e.g., panic hardware), refer to calculation procedures furnished in Design of Smoke Control Systems for Buildings published by ASHRAE3.

Airflow

Airflow is most commonly used to stop smoke movement through open doorways and corridors. Figure 4 illustrates a system with relatively high velocity to prevent backflow of smoke through an open doorway. Figure 5 illustrates a system with relatively low velocity which allows backflow of smoke. The magnitude of the velocity of the airflow required to prevent backflow depends on the energy release rate of the fire. Since this can vary, the velocity should be regulated to prevent oxygen from being fed to the fire. The fact that doors are sometimes left open during evacuation of a building, allowing smoke to flow through, should be taken into account in designing the smoke control system. This is done by designing and testing the system with one or more doors open.

Fig. 4. High Air Velocity Preventing Backflow of Smoke Through an Open Doorway.

Fig. 5. Low Air Velocity Allowing Backflow of Smoke through an Open Doorway.

Purging

Because fires produce large quantities of smoke, purging cannot ensure breathable air in a space while a fire is in progress. After a fire, purging is necessary to allow firefighters to verify that the fire is totally extinguished. Traditionally, firefighters have opened doors and windows to purge an area. Where this is not possible, the HVAC system can be designed to have a purge mode.

The principle of dilution can be applied to zones where smoke has entered and is being purged. Purging dilutes the contaminated air and can continue until the level of obscuration is reduced and the space is reasonably safe to enter. The following equation allows determining a concentration of contaminant in a compartment after purging for a given length of time3:

C = C0 x eat

Where:

C = concentration of contaminant at time, t iC0 = initial concentration of contaminant a = purging rate in number of air changes per minute t = time after doors close in minutes e = constant, approximately 2.718

Care must be taken in the use of this equation because of the nonuniformity of the smoke. Buoyancy is likely to cause greater concentration of smoke near the ceiling. Therefore, consideration of the locations of supply and exhaust registers is important to effective purging.

CONTROL APPLICATIONS

Figure 6 illustrates a smoke control system with detectors, an initiating panel, and a communications bus to an alarm processor and remote control panels in appropriate areas of the building. A configuration similar to this will meet the requirements of UL 864, Standard for Control Units for Fire-Protective Signaling Systems, and comply with NFPA 92A recommended practice for smoke control systems. The remote control panels position dampers and operate fans to contain or exhaust smoke, depending on the requirements of the various areas in the building. The system can have an operator's control console for the building personnel and an FSCS from which to view the status of and override the smoke control system. The system requires a means of verifying operation, such as differential pressure or airflow proving devices, for each control sequence. An uninterruptible power supply (UPS) is optional but recommended.

Fig. 6. Typical Smoke Control System Meeting the Requirements of UL Standard 864 and NFPA 92A.

The following discussions cover smoke control applications for building zones, stairwells, and large areas including malls and atria. Each of these discussions conclude with a typical operational sequence complying with UL Standard 864 for the smoke control system illustrated in Figure 6.

Zone Pressurization

The objective of zone pressurization is to limit the movement of smoke outside the fire or the smoke control zone by providing higher pressure areas adjacent to the smoke zone. Zone pressurization can be accomplished by:

- Providing supply air to adjacent zones

- Shutting off all returns or exhausts to floors other than the fire floor

- Exhausting the smoke zone (also aids stairwell pressurization systems by minimizing buoyancy and expansion effects)

- Shutting off, providing supply air to, or leaving under temperature control all supplies other than those adjacent to the fire floor

A smoke control zone can consist of one or more floors or a portion of a floor. Figure 7 illustrates typical arrangements of smoke control zones. The minus sign indicates the smoke zone. The plus signs indicate pressurized nonsmoke zones. In the event of a fire, the doors are closed to the fire or smoke control zone and the adjacent zones are pressurized. In the example in Figures 7A and 7B, the floors above and below the smoke zone are pressurized. The application in Figure 7B is called a pressure sandwich. In Figures 7C and 7D, the smoke zone consists of more than one floor. In Figure 7E, the smoke zone is only a part of a floor and all the rest of the building areas are pressurized. Smoke zones should be kept as small as reasonable so control response can be readily achieved and quantities of air delivered to the nonsmoke zones can be held to manageable levels.

Fig. 7. Typical Zone Pressurization Arrangements for Smoke Control Zones.

The practice of exhausting air as a means of providing higher pressure areas adjacent to the smoke zone should be examined carefully. Exhausting air from the fire floor may tend to pull the fire along and cause flames to spread before they can be extinguished.

Another consideration in zone pressurization is that bringing in outdoor air at low temperatures can cause serious freeze damage. Provision should be made to prevent damage when using outdoor air, such as providing emergency preheat and minimizing the quantity of outdoor air used.

Testing of smoke control strategies should include not only verification of acceptable pressures but also confirmation that interaction with other systems creates no problems, such as excessive door pull in a stairwell pressurization system.

Typical Operation for Zone Pressurization System (See Fig. 6):

1. Smoke detector(s) initiate alarm in specific zone. 2. System switches to smoke control mode as determined in remote control panel. 3. System turns on pressurization fans if not already on. 4. System allows pressurization fans to continue running if supply duct smoke detector is not in alarm or manual override is not activated. 5. System enables damper operation as appropriate for smoke control mode. 6. Operator verifies operation as appropriate (e.g., action of differential pressure switch). 7. Operator cancels smoke control mode as long as initiating panel is not in alarm and FSCS is not in manual override.

Stairwell Pressurization

The objective of stairwell pressurization is to provide an acceptable environment within a stairwell, in the event of a fire, to furnish an egress route for occupants and a staging area for firefighters. On the fire floor, a pressure difference must be maintained across the closed stair tower door to ensure that smoke infiltration is limited. Also, adequate purging must be provided to limit smoke density caused by temporary door openings on the fire floor.

To ensure proper stairwell pressurization system design, a means should be included to modulate either the supply or the exhaust/relief dampers. Also, a means should be included to provide multiple supply injection points at a minimum of every three floors (unless design analysis can justify a greater spacing) to provide uniform pressurization.

According to NFPA 92A, Recommended Practice for Smoke Control Systems, the intake of supply air should be isolated from smoke shafts, roof smoke and heat vents, and other building openings that might expel smoke from the building in a fire. Wind shields should be considered at fan intakes.

Open-loop control of pressurization is seldom acceptable because of significant pressure differences caused by door openings. Closed loop or modulation provides the ability to control pressurization within acceptable limits. Closed loop control can be as simple as a barometric pressure damper (Fig. 8) to relieve pressure at the top of a stairwell or a more complex system to modulate dampers or fans at multiple injection points (Fig. 9) in response to differential pressure measurements at these points.

Fig. 8. Stairwell Pressurization with Barometric Pressure Damper to Vent to the Outside.

Fig. 9. Stairwell Pressurization with Modulating Dampers and Multiple Injection Points to Regulate Pressure.

Testing of stairwell pressurization systems should be conducted with agreed on conditions including:

- Number and location of doors held open - Outside pressure conditions known - Maximum door pull force allowed

Typical Operation for Stairwell Pressurization (See Fig. 6):

1. Any fire alarm initiates smoke control mode. 2. System turns on pressurization fans. 3. System allows pressurization fans to continue running if supply duct smoke detector is not in alarm or manual override is not activated. 4. System enables damper operation as appropriate for smoke control mode. 5. Operator verifies operation as appropriate (e.g., action of differential pressure switch). 6. Operator cancels smoke control mode as long as initiating panel is not in alarm and FSCS is not in manual override.

Control of Malls, Atria and Large Areas

The objective of malls, atria, and other large area smoke control systems is to prevent the area from filling with smoke as a result of fire in the area or an adjoining area. Purging is used as the means to dilute and remove smoke.

In large areas (Fig. 10), the smoke produced is buoyant and rises in a plume until it strikes the ceiling or stratifies because of temperature inversion. The smoke layer then tends to descend

as the plume continues to supply smoke. Smoke can be exhausted to delay the rate of descent of the smoke layer. Also, sprinklers can reduce the heat release rate and the smoke entering the plume. Adjacent spaces to the mall or atrium can be protected from the smoke by barriers or opposed airflow.

Fig. 10. Control of Smoke in Malls, Atria, and Other Large Areas.

Additional information can be found in NFPA 92B, Guide for Smoke Management in Malls, Atria, and Large Areas.

Typical Operation for Malls, Atria, and Large Area Smoke Control System (See Fig. 6):

1. Any fire alarm initiates smoke control mode. 2. System turns on exhaust fans. 3. System enables damper operation as appropriate for smoke control mode. 4. Operator verifies operation as appropriate (e.g., action of airflow-proving sail switch). 5. Operator cancels smoke control mode as long as initiating panel is not in alarm and FSCS is not in manual override

ACCEPTANCE TESTING

Smoke control systems must be tested carefully and thoroughly. All measurements should be recorded and saved.

ASHRAE Guideline 5-1994 should be followed.

The system should be activated by an appropriate sensor within the zone (if applicable) and the results should be monitored and recorded.

Where standby power is used, testing should be conducted with both normal power and standby power.

The use of smoke bombs or tracer gas to test smoke control systems is discouraged because they cannot accurately simulate fire conditions. Smoke bombs and tracer gas lack the buoyant forces caused by heat generated in a fire. These items can be used, however, for identifying leakage paths and leakage areas.

Periodic testing should be conducted in accordance with the following:

- NFPA 90A, Installation of Air Conditioning and Ventilating Systems - NFPA 92A, Recommended Practice for Smoke Control Systems - NFPA 92B, Guide for Smoke Management Systems in Malls, Atria, and Large Areas

Smoke Management Fundamentals

BIBLIOGRAPHY

Referenced Publications

1. Toxicity Effects Resulting from Fires in Buildings, State-of-the Art Report, May 16, 1983, National Institute of Building Sciences.

2. NFPA 92A, Recommended Practice for Smoke Control Systems, 1996 Edition.

3. Design of Smoke Management Systems, 1992 Edition, J.H. Klote and James A. Milke; ASHRAE, Inc., and Society of Fire Protection Engineers, Inc.

Additional Related Publications

1. Smoke Management, Chapter 48, ASHRAE 1995 HVAC Applications Handbook.

2. NFPA 72 National Fire Alarm Code, 1996 Edition.

3. NFPA 90A, Installation of Air Conditioning and Ventilating Systems, 1996 Edition.

4. NFPA 92B, Guide for Smoke Management Systems in Malls, Atria, and Large Areas, 1995 Edition.

5. NFPA 101, Life Safety Code, 1994 Edition.

6. Smoke Control in Fire Safety Design, A. G. Butcher and A. C. Parnell, E. & F. N. Spon Ltd., 11 New Fetter Lane, London EC4P 4EE, 1979.

7. Smoke Control Technology, Code 88146, ASHRAE, 1989.

8. UL 555, Standard for Fire Dampers and Ceiling Dampers, Fifth Edition, 1995 Revision.

9. UL 555S, Standard for Leakage Rated Dampers for Use In Smoke Control Systems, Third Edition, 1996 Revision.

10. UL 864, Standard for Control Units for Fire-Protective Signaling Systems (UL Category UUKL), Eighth Edition, 1996 Revision.

11. ASHRAE Guidelines 5-1994, Commissioning Smoke Management Systems, ISSN 1049 894X.

12. NFPA Fire Protection Handbook, 17th Edition, 1991.

13. Smoke Movement and Control in High-Rise Buildings, George T. Tamura, P.E., NFPA, Quincy Massachusetts, December 1994; Library of Congress 94-069542; NFPA SCHR-94; ISB: 0-87765-401-8.

Referenced Publications

1. Toxicity Effects Resulting from Fires in Buildings, State-of-the Art Report, May 16, 1983, National Institute of Building Sciences.

2. NFPA 92A, Recommended Practice for Smoke Control Systems, 1996 Edition.

3. Design of Smoke Management Systems, 1992 Edition, J.H. Klote and James A. Milke; ASHRAE, Inc., and Society of Fire Protection Engineers, Inc.

Additional Related Publications

1. Smoke Management, Chapter 48, ASHRAE 1995 HVAC Applications Handbook.

2. NFPA 72 National Fire Alarm Code, 1996 Edition.

3. NFPA 90A, Installation of Air Conditioning and Ventilating Systems, 1996 Edition.

4. NFPA 92B, Guide for Smoke Management Systems in Malls, Atria, and Large Areas, 1995 Edition.

5. NFPA 101, Life Safety Code, 1994 Edition.

6. Smoke Control in Fire Safety Design, A. G. Butcher and A. C. Parnell, E. & F. N. Spon Ltd., 11 New Fetter Lane, London EC4P 4EE, 1979.

7. Smoke Control Technology, Code 88146, ASHRAE, 1989.

8. UL 555, Standard for Fire Dampers and Ceiling Dampers, Fifth Edition, 1995 Revision.

9. UL 555S, Standard for Leakage Rated Dampers for Use In Smoke Control Systems, Third Edition, 1996 Revision.

10. UL 864, Standard for Control Units for Fire-Protective Signaling Systems (UL Category UUKL), Eighth Edition, 1996 Revision.

11. ASHRAE Guidelines 5-1994, Commissioning Smoke Management Systems, ISSN 1049 894X.

12. NFPA Fire Protection Handbook, 17th Edition, 1991.

13. Smoke Movement and Control in High-Rise Buildings, George T. Tamura, P.E., NFPA, Quincy Massachusetts, December 1994; Library of Congress 94-069542; NFPA SCHR-94; ISB: 0-87765-401-8.

Additional Related Publications

1. Smoke Management, Chapter 48, ASHRAE 1995 HVAC Applications Handbook.

2. NFPA 72 National Fire Alarm Code, 1996 Edition.

3. NFPA 90A, Installation of Air Conditioning and Ventilating Systems, 1996 Edition.

4. NFPA 92B, Guide for Smoke Management Systems in Malls, Atria, and Large Areas, 1995 Edition.

5. NFPA 101, Life Safety Code, 1994 Edition.

6. Smoke Control in Fire Safety Design, A. G. Butcher and A. C. Parnell, E. & F. N. Spon Ltd., 11 New Fetter Lane, London EC4P 4EE, 1979.

7. Smoke Control Technology, Code 88146, ASHRAE, 1989.

8. UL 555, Standard for Fire Dampers and Ceiling Dampers, Fifth Edition, 1995 Revision.

9. UL 555S, Standard for Leakage Rated Dampers for Use In Smoke Control Systems, Third Edition, 1996 Revision.

10. UL 864, Standard for Control Units for Fire-Protective Signaling Systems (UL Category UUKL), Eighth Edition, 1996 Revision.

11. ASHRAE Guidelines 5-1994, Commissioning Smoke Management Systems, ISSN 1049 894X.

12. NFPA Fire Protection Handbook, 17th Edition, 1991.

13. Smoke Movement and Control in High-Rise Buildings, George T. Tamura, P.E., NFPA, Quincy Massachusetts, December 1994; Library of Congress 94-069542; NFPA SCHR-94; ISB: 0-87765-401-8.