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Controlling Tomorrow’s World
Infinity Smoke Control Guide
Electronic Version
Andover Controls Corporation |
i |
Downloaded from - http://www.guardianalarms.net
Version B
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Copyright © 1995, 1996 Andover Controls.
Subject to change without notice.
Order No. 30-3001-446
Copyright © 1995, 1996
Andover Controls Corporation
300 Brickstone Square
Andover, Massachusetts 01810
All Rights Reserved.
Published by the Engineering Department at Andover Controls Corporation.
IMPORTANT NOTICE
Examples in this book are for illustrative purposes only and have never been tested in an actual building.
This product is subject to change without notice. This document does not constitute any warranty, express or implied. Andover Controls Corporation reserves the right to alter capabilities, performance, and presentation of this product at any time.
The following trademarks are used in this manual:
CROSSTALK is a registered trademark of Digital Communications Associates, Inc.
IBM is a registered trademark of International Business Machines, Inc.
VT is a trademark of Digital Equipment Corporation.
ii |
Infinity Smoke Control Guide |
Chapter 1
The Fundamentals of Smoke
Control
One of the most hazardous situations that you can face in a building is smoke. While fires themselves are often damaging, it is smoke that can cause the most injuries. For example, at the World Trade Towers in February 1993, over 1,000 were injured by the smoke that resulted from the fire.
To protect your building’s occupants, as well as furnishings and equipment that may be damaged by smoke, you need a smoke control system. A smoke control system, as its name implies, controls the flow of smoke in your building in the event of fire. It keeps smoke from spreading throughout the building, giving the building’s occupants a clear evacuation route, as well as preventing further damage to the building’s interior.
This chapter gives you an overview of smoke control theory.
The Fundementals of Smoke Control
Understanding Types of Smoke
Control Systems
Two types of smoke control systems exist—dedicated and nondedicated. The dedicated smoke control system is installed in a building for the sole purpose of controlling smoke. A nondedicated smoke control system uses parts of the building’s HVAC system to control smoke.
In most instances, a building has both nondedicated and dedicated systems. Nondedicated systems are used throughout the building for normal areas (offices, manufacturing). Dedicated systems are used for special areas, such as elevator shafts, stairtowers, and other areas that need special smoke control techniques.
The operation of the nondedicated smoke control equipment is verified by the “comfort level” in the areas that are served by the equipment. In other words, if the HVAC equipment is not functioning properly, the building’s occupants will be aware of this and the problem will get fixed.
The operation of the dedicated smoke control equipment is verified by an automatic self-test that is performed on a weekly basis.
1-2 |
Infinity Smoke Control Guide |
The Fundementals of Smoke Control
Using Pressure to Control Smoke
The basic concept behind controlling smoke, regardless of whether it is with a dedicated or nondedicated system, is to use air pressure to confine and (if possible) vent smoke from the building.
You cannot confine smoke by simply closing all access ways (such as doors and vents) to the room that has the fire in it. Even with these passages closed off, smoke can disperse throughout a building via cracks, holes made for pipes and electrical wires, and spaces around doors and windows. Smoke is driven through these small openings by the expanding gases from the fire. Smoke can also be driven onto other floors by the stack effect, which causes air to rise in buildings. The stack effect is caused by the difference in the interior and exterior temperature of the building. The following diagram shows how smoke can disperse throughout a building.
Figure 1-1. Smoke Infiltrating Areas Adjacent to the Fire
Adjacent
Area
Adjacent Area |
Area on Fire |
Adjacent Area |
Since smoke is carried by the movement of air, you can stop the spread of smoke throughout the building by lowering the air pressure in the area containing the fire and by raising the air pressure in the surrounding areas and floors. The difference in pressure (also called the pressure differential) between the smoke-filled area and the surrounding areas acts as a barrier to the smoke, pushing it back into the smoke-filled area. The next illustration shows how this works.
Andover Controls Corporation |
1-3 |
The Fundementals of Smoke Control
Figure 1-2. Air Pressure Containing Smoke
Positive |
Positive |
Positive |
Air Pressure |
Air Pressure |
Air Pressure |
Positive |
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Air Pressure |
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Air Pressure |
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Pressure |
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Positive |
Positive |
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Positive |
Air Pressure |
Air Pressure |
Air Pressure |
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You lower the air pressure in the smoke-filled area by shutting off all air flow into it and turning on the exhaust fans from the area to full capacity. This technique pulls the smoke out of the area and vents it outside of the building.
You pressurize the areas and floors surrounding the fire by turning off all exhaust systems (including closing any exhaust dampers) and forcing supply air to those areas at full capacity. The air in the pressurized areas tends to leak into the smoke zone, using the same cracks and holes that the smoke would use to get out. This airflow into the burning room keeps the smoke from spreading.
Areas that are neither being pressurized nor depressurized (i.e. areas far away from the fire) have both their air inlets and air return systems turned off. Turning off the air return prevents the smoke that is being vented into the return air system from coming into the area.
In cases where there are large openings (such as an open doorway) between the area on fire and an adjacent area, smoke can be confined by a large volume of air. Pumping large amounts of air through the adjacent space creates a constant draft through the opening into the smoke zone (as shown in the next illustration). The draft through the open space keeps back the smoke, confining it to the smoke zone. The amount of air required to keep the smoke from penetrating the open space is quite large, so you should avoid this sort of situation when possible.
1-4 |
Infinity Smoke Control Guide |
The Fundementals of Smoke Control
Figure 1-3. Keeping Smoke Away from a Large Opening
Andover Controls Corporation |
1-5 |
The Fundementals of Smoke Control
Creating Smoke Zones
In order to contain the smoke by using pressure, you must divide the building into smoke control zones. A floor or several floors of the building can be a single zone, or one floor can be broken into a number of zones. A zone must be separated from other zones by smoke dampers, airtight doors, and smoke-proof barriers.
When a fire breaks out, the smoke control system can then pressurize all of the zones around the one where the fire broke out (called the fire zone), isolating the smoke to that single zone.
If the smoke control system is nondedicated, the layout of the smoke control zones should take into consideration the layout of the HVAC system. You should place multiple areas served by the same VAV boxes in the same smoke control zone. Also, the smoke control zones must conform to any fire control zones that have been established, because the smoke detectors are tied into the fire detection system. Also, keeping the smoke control zones and the fire control zones the same makes coordinating the two systems simpler.
Smoke Control vs. Fire Control Systems
The smoke control system is usually separate from the fire control system, since they have different goals. The fire control system’s goal is to contain and extinguish the fire as fast as possible. These systems, which halt the fire but not the smoke, are often triggered automatically, relying on the heat of the fire to activate the system. Although smoke control systems are also automatic, you must have manual overrides for the automatic controls. Another difference between smoke control and fire control systems is that where fire control systems, such as sprinklers, often rely on only a water supply, smoke control systems usually rely on electricity to run fans and dampers. So, some smoke control systems have a standby power supply. Standby power provides the smoke control system with electricity in case the main power fails.
The smoke control system should be designed to work with the fire control system and not interfere with its operation. For instance, if the building has a sprinkler system, then the smoke control system does not need to control a large quantity of smoke, since the size of any fire should be smaller.
1-6 |
Infinity Smoke Control Guide |
The Fundementals of Smoke Control
A smoke control system may also have to be designed to work with gas-based fire extinguishers, such as the halon gas systems installed in many computer rooms. If the smoke control system tried to vent a room with such a system, it would probably vent the fire suppressing gas as well. Removing the gas lets the fire continue burning. Also, pressurizing the areas surrounding an extinguisher equipped room reduces the effectiveness of the system as well. Air forced into the room from the outside by pressure can provide the fire with the oxygen it needs to continue burning. So, gas-based fire extinguishers and smoke control systems should not be active at the same time in the same area.
The smoke control system receives the location of the fire from the fire panel. The fire panel uses a combination of smoke and heat sensors to determine where the fire is located.
In the event that signals are received from more than one smoke zone, the smoke control system should continue automatic operation in the mode determined by the first signal received.
Smoke control systems should never be triggered by manual pull boxes. The risk of someone pulling a box someplace other than the fire zone is too high for you to trust your smoke control system to this form of activation.
All smoke control systems installed in buildings must meet the standards established by the National Fire Protection Association in their publication NFPA 92A, Smoke Control Systems, 1988 edition. You can find additional information regarding fire alarm control units in the Underwriters Laboratories Inc. Standard UL 864.
Andover Controls Corporation |
1-7 |
The Fundementals of Smoke Control
Designing a Smoke Control System
What is the basic goal of the smoke control system? To maintain a tenable environment. A tenable environment allows:
•The building’s occupants to evacuate safely
•The fire fighters to get to the fire zone
The first step you take in designing your smoke control system is to lay out the smoke control zones, as previously explained. After the smoke zones are established, you have to address the following design factors:
•The zone-by-zone smoke control strategies to use
•The amount of pressure needed to contain smoke
•Proper separation between zones
•The fans and ductwork used in the smoke control system
•Dampers required for smoke control
•The air inlets and outlets used in the smoke control system
•Duct smoke detectors
Devising a Smoke Control Strategy
For each zone in your building, you have to establish a smoke control strategy. The smoke control strategy is a series of steps the smoke control system must take to contain the smoke. For each zone, you must decide:
•Whether you should depressurize the zone if a fire occurs.
•If the zone is to be depressurized, by how much you should depressurize it.
•Which adjacent zones should be pressurized and how much pressure is required.
Some zones in your building may need special consideration. As mentioned earlier, zones that have gas fire extinguisher systems should not be vented (depressurized) and the zones surrounding the fire zone with such a system should not be pressurized. You may not be able to pressurize other areas, such as hospital or animal labs, due to the risk of contaminating surrounding areas.
Consider the number of zones surrounding the fire zone that should be pressurized. While in theory, all you need to do is to pressurize all of the
1-8 |
Infinity Smoke Control Guide |
The Fundementals of Smoke Control
zones immediately surrounding the fire zone, it is possible that smoke can find its way around the pressurized areas and infiltrate zones far away. Depending on the size of your building, and the capacity you plan to have in the smoke control system, you may decide you want to pressurize more than just the surrounding zones. But, the more zones you want to pressurize, the larger your air supply system needs to be.
Write down the state that all fans, dampers, and other smoke control equipment should be in to control smoke in each zone. Later, you have to program this information into the smoke control system. This information gives the smoke control system a strategy for containing smoke in each possible fire zone.
Andover Controls Corporation |
1-9 |
The Fundementals of Smoke Control
Determining the Amount of
Pressure Needed
Since air pressure is what keeps smoke from spreading, the primary design factors are the amount of pressure that you need to confine the smoke and the size of the system used to create this pressure.
For the smoke control system to create a barrier of air pressure between the smoke zone and surrounding zones, the amount of pressure required varies with the height of the ceiling and whether or not the building has a sprinkler system. The next table shows the minimum pressure differential needed to keep smoke out of surrounding rooms.
Table 1-1. Minimum Pressure Differential to
Pressurize Fire Zone
Sprinkler |
Ceiling |
Minimum Pressure |
System |
Height |
Differential (wg) |
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Yes |
Any |
0.05 |
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No |
9 ft |
0.10 |
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No |
15 ft |
0.14 |
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No |
21 ft |
0.18 |
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For buildings without sprinklers and with ceiling heights not shown in the table, you can use the following formula to determine the minimum amount of pressure needed to keep smoke out:
MinimumPressure = 7.64 × H × |
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1 |
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+ SafetyFactor |
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To |
Tf |
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H is the distance between the fire space and a surrounding space where
2
the pressure differential is zero. A figure of - the floor to ceiling height
3
is a conservative estimate.
To is the absolute room temperature of the surrounding zones measured in °R (degrees Rankine). Typically, To = 530° R (70° F). The conversion from °R to °F is: °R = °F + 460.
Tf is the absolute temperature of the hot gases in the fire zone. It is also measured in °R. Typically, Tf is 2160° R (1700° F).
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Infinity Smoke Control Guide |
The Fundementals of Smoke Control
SafetyFactor is a constant added to the results to make sure they are sufficient. A value of 0.03 wg (inches water gauge) is recommended.
Pressure buildup in an area depends on how much leakage there is. Leakage occurs through joints, cracks, openings for pipes and wires, gaps between doors and their door jams, and so forth. The better the zone is sealed off from its neighbors, the easier it is to maintain the required pressure. Since larger openings, like doorways that are normally open, require large amounts of air to maintain pressurization, you should avoid this type of situation.
Andover Controls Corporation |
1-11 |
The Fundementals of Smoke Control
Separating Zones
You must separate smoke zones from one another by smoke barriers, which prevent smoke from passing through them. Smoke barriers can be a wall, a floor, or a ceiling. Any openings in the smoke barrier must be closed with a smoke-proof fitting. For example, all duct work going through a smoke barrier must have a smoke damper in it. A smoke damper is a damper that prevents smoke from passing through it when fully closed. (Refer to the dampers section below for more information.) During a smoke emergency all of the fittings should seal themselves, so that smoke cannot penetrate the barrier.
Since the smoke control zones should be the same as the fire control zones, you usually separate your zones with a fire rated partition. A fire rated partition is a wall that is built of fire resistant materials and that reaches from floor to ceiling. Different floors should be separated by a fire rated ceiling, a ceiling made of fire resistant materials. Both fire rated partitions and fire rated ceilings are rated for the amount of time they can withstand a fire. Any openings in a fire rated partition or ceiling must be sealable with a fire rated closure, such as fire rated doors or fire damper.
Selecting Dampers
The dampers used to isolate the smoke zone must be smoke dampers. Smoke dampers are dampers that meet the requirements given in UL 555S, Standard for Leakage Rated Dampers for Use in Smoke Control
Systems. Following this standard ensures that the dampers are able to block the smoke when they are fully closed. These dampers may be different from those you might use in an HVAC system that does not perform smoke control.
In a smoke control system, the dampers must be able to travel to their desired setting in 75 seconds. All dampers must be fitted with end position microswitches to provide feedback to the smoke control system. These switches let the control system know the position of the dampers, since smoke dampers are usually either fully closed or fully open.
Dampers sometimes function as both smoke dampers and fire dampers. Fire dampers are dampers that block a fire from penetrating a fire rated partition via a duct. These dampers are normally open, held in place by a fusible link. The fusible link is a heat-sensitive device that releases the
1-12 |
Infinity Smoke Control Guide |
The Fundementals of Smoke Control
dampers when it is heated to a certain temperature. Once the fusible link releases, the dampers close by the force of gravity. So, fire dampers operate even if the electricity has failed. The specifications for fire dampers appear in the document UL555, Standard for Fire Dampers.
If you want a damper to function as both a smoke damper and a fire damper, it must meet the requirements for both devices. These dampers can be operated by electric motors or pneumatics. But it must, however, also have a fusible link or other means of closing automatically, like a regular fire damper. The control system can override the closure due to temperature. The damper needs the fusible link in case the automatic control of the damper by the control system is interrupted.
Choosing Fans and Duct Work
The fans and duct work used in the smoke control system must be capable of providing the amount of pressure you calculated earlier. In a nondedicated system, this may mean that you need to install fans that have a higher capacity than the HVAC system calls for. The ducts must be capable of taking the pressurization (or the depressurization, for the fire zone’s return duct) that the smoke control system will exert.
Both the fans and the ducts should meet the requirements stated in NFPA 90A, Standard for the Installation of Air Conditioning and Ventilating Systems.
Fans for a smoke control system normally do not have to meet any special heat resistance rating. In a smoke control system, fans must be able to reach the required setting in 60 seconds. Each fan must have a pressure monitor mounted so that the smoke control system can receive feedback on the status of the fan to determine whether it is actually operating or not.
In some climates, the outside air can be so cold that drawing it directly inside the building can damage the building’s interior (freeze pipes or damage temperature-sensitive equipment, for example). In these cases, some sort of preheater needs to be installed on the air inlet. The smoke control system does not have to control the heater as closely as one in an HVAC system, since maintaining comfort levels is not an issue. It simply has to make sure the air sent into an area is not going to damage the building’s interior.
Andover Controls Corporation |
1-13 |
The Fundementals of Smoke Control
Positioning Air Inlets and Outlets
You need to carefully consider the placement of the air inlets and outlets on your building. If you place an outlet that vents smoke too close to an air inlet, the air intake can draw the smoke back into the building.
Since smoke rises, the exhausts that vent smoke should be placed well above air inlets. The exhausts should be placed at least 3 ft above the roof level, to allow space for the smoke to rise and disperse.
Keeping smoke outlets far away from air inlets does not guarantee that the air brought into the building is always smoke free. You may want to place smoke detectors in air inlets that operate during a smoke emergency. If the detector finds smoke in the incoming air, it alerts the control system. The control system has to decide whether or not to shut down the air inlet.
You should refer to NFPA 90A for more information on smoke detectors in inlets and outlets.
1-14 |
Infinity Smoke Control Guide |
The Fundementals of Smoke Control
Employing Dedicated Smoke
Control Systems
Most of the systems discussed so far have been nondedicated systems. Even in a building whose primary smoke control system is nondedicated, you may have special zones or functions where you need to use a dedicated system. The most common dedicated system is a dedicated smoke control system for a stairtower.
StairTowers
Stairtowers are stairwells with a ventilation system and are isolated from the main building. The only connection between the building and the stairtower is fire-rated doors on each floor. Since the building’s occupants should use the stairtower to leave during an evacuation, keeping the stairtower smoke free is vital.
A stairtower has its own dedicated system that pressurizes the stairwell to keep smoke out. This dedicated system can take several forms, from a fan mounted in the roof of the stairtower, to a duct system that delivers air to each level.
You must pressurize a stairtower enough to keep smoke out. However, if the pressure in the stairtower is too great, then opening the doors leading into the stairtower can be difficult. You must strike a balance. The stairtower smoke control system must pressurize the stairway enough to keep the smoke out, but it must not pressurize it so much that the doors cannot be opened.
Figure 1-4. The Effects of Too Much and Too Little Pressure
Too Much Pressure |
Too Little Pressure |
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Stairtower |
Building |
Stairtower |
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Andover Controls Corporation |
1-15 |
The Fundementals of Smoke Control
Figure 1-5. Parts of a Stairtower System
Exhaust Fan or Vent
Air
Supply
Duct
Pressure
Vents
Supply Fan
Fire Rated Door 
Building Stairtower
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Infinity Smoke Control Guide |
The Fundementals of Smoke Control
Ensuring Doors Can Be Opened
The table below shows the maximum allowable pressure differential across a door in inches water gauge based on how wide the door is and how much force the automatic door closing mechanism exerts. At the pressures shown in the table, the door requires 30 lbf (pound of force) to open, the maximum limit suggested by the NFPA Life Safety Code.
Table 1-2. Pressure Differential Across Doors
Door Closer |
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Pressure Differential for Various |
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Force (lbf) |
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Door Widths (inches) |
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32 in |
36 in |
40 in |
44 in |
48 in |
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6 |
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0.45 |
0.40 |
0.37 |
0.34 |
0.31 |
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8 |
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0.41 |
0.37 |
0.34 |
0.31 |
0.28 |
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10 |
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0.37 |
0.34 |
0.30 |
0.28 |
0.26 |
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12 |
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0.34 |
0.30 |
0.27 |
0.25 |
0.23 |
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14 |
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0.30 |
0.27 |
0.24 |
0.22 |
0.21 |
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The table above assumes a door height of 7 ft and a distance from the doorknob to the knob side of the door of 3 in. If your door does not meet these requirements, or has opening hardware other than a doorknob, such as panic hardware, then refer to the ASHRAE publication Design of Smoke Control Systems for Buildings for a formula to calculate the proper opening force. The door widths in the table are only valid for doors that are hinged at one end. For other types of doors, see the ASHRAE document.
Many door closers vary the amount of force as the door opens. They provide less resistance in the early stages of opening the door than they do later, when the door is almost fully open. The force to open the door shown in the previous table represents the force needed to open the door only enough to let air flow through the opening. Once air is able to flow, the force exerted by the difference in air pressure on the door lessens. Therefore, when calculating the force required to open the door, you may need to lower the door closer force.
Andover Controls Corporation |
1-17 |
The Fundementals of Smoke Control
Controlling Pressure in a Stairtower
Stairtower smoke control systems are divided into two categories— noncompensated and compensated. Noncompensated systems simply turn on a fan to pressurize the stairtower. The fan’s speed does not change to compensate for doors opening and closing. The more doors that are open, the more the pressure differential between the stairwell and the building drops.
Figure 1-6. Compensated and Noncompensated Stairtower
Systems
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Vent
A compensated system adjusts the airflow to make up for pressure lost through open doors. It can use dampers to relieve excess pressure in the stairtower to ensure that the pressure does not go over the maximum limit.
There are a number of ways compensated stairtower smoke control systems can control pressurization. In a basic system with a roofmounted fan blowing air into the stairtower, pressure can be regulated by varying the speed of the fan, the pitch of the fan’s blade, the inlet vanes, or the number of fans operating (assuming there is more than one).
More sophisticated systems use ducts to deliver air to several points in the stairtower. The dampers can be controlled to maintain the appropriate pressure in their zone.
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Infinity Smoke Control Guide |
The Fundementals of Smoke Control
Figure 1-7. Examples of Controlling Stairtower Pressure
Pressurization Fan
Air Pressure
Duct
Duct systems can also use bypass dampers and ducts to control the amount of air flowing from the fan to the outlets. The bypass dampers are opened when the stairtower is at the proper pressure, so that excess air flows not into the duct system, but into the bypass duct and back to the air inlet. See the next diagram for an example of a bypass duct system.
Figure 1-8. A Bypass Pressure Control System
Bypass Duct Dampers
Air Intake
Bypass Duct
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Andover Controls Corporation |
1-19 |
|||||
The Fundementals of Smoke Control
There are also a number of ways a compensated stairtower smoke control system can get rid of excess air pressure, to ensure that the doors leading into the stairtower can open properly. One or more vents to the building’s exterior (with dampers) can be used in the stairtower to release excess pressure. These dampers can be barometrically controlled (being forced open by the excess air pressure) or controlled by electric motors or pneumatics as in conventional HVAC systems. In both cases, the dampers must be placed far enough away from the air supply to prevent venting of air that has not yet been able to disperse through the stairtower. Vents can also lead into the building, but you should consider carefully the impact of venting extra pressure into the building before using this type of vent.
In some cases, a ground-level stairtower door can be used in place of dampers. This door automatically opens and closes to maintain the proper amount of pressure in the stairtower. The door is usually locked, for security reasons. During an emergency, the smoke control system has to be able to override the lock. Using a door in this manner has its problems, since wind effects close to the base of a building could prevent the air from escaping through the door.
Figure 1-9. Methods of Controlling Stairtower Pressure
Roof-mounted Exhaust Fan
Vent to Outside with Barometrically or Automatically Controlled Dampers
Automatic Door Used to Vent Pressure
You can also use an exhaust fan to vent the excess pressure from the stairtower. Such a fan should be designed to operate only when the stairtower is overpressurized. It should never be on when the pressure differential between the building and the stairtower is below the lowest limit.
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Infinity Smoke Control Guide |
The Fundementals of Smoke Control
Elevators
Elevator shafts present a special menace with regards to smoke control. The elevator shafts form perfect chimneys to draw smoke into the upper levels of a building. Since elevators usually have openings on each floor, and the seals on the elevator doors are often poor, the elevator shaft can become a mechanism to spread smoke throughout a building. Smoke control in an elevator shaft is an important consideration in the overall smoke control plan.
Figure 1-10. Smoke Control For Elevator Shafts
Low Pressure Area
Created by Elevator
Special Smoke
Proof Elevator
Doors
Low Pressure Area
Created by Elevator
Pressurization Fan for Elevator Shaft
If you could manage to make them safe during smoke emergencies, elevators would ease the evacuation of the building, especially for people in wheelchairs. To have the elevators usable during a smoke emergency, you need to pressurize the elevator shafts the same way you pressurize a stairtower.
However, pressurizing the elevator shaft presents a number of problems. While the elevator doors can be fitted with improved seals and rubber sweeps, these systems will not totally eliminate air leakage. Also, most elevator shafts are not designed to be pressurized. They often have large openings at the top where the cables feed into the winding room. Shafts are often constructed of porous material that cannot contain the air pressure. And since most shafts are not designed to be inspected after the elevators are installed, finding and repairing cracks that would let smoke infiltrate or pressure escape is difficult.
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The Fundementals of Smoke Control
Another primary problem with letting elevators run during a smoke emergency is the localized pressure differences that the cars create as they travel up and down the shafts. For example, a car moving down from the top of the shaft may create a small low air pressure zone near the shaft’s top, which can pull smoke from the fire zone into the shaft.
At the present time, these issues have not been resolved. Pressurizing the elevator shafts so that the elevators can operate during a smoke emergency is still being studied. In general, elevators should not be used as an escape route during an evacuation.
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The Fundementals of Smoke Control
Detecting Smoke
The fire control system is the system that is connected to the smoke and fire detectors. Every smoke zone should have a Listed smoke and fire detector installed in it. The detectors should be located so that they will detect the presence of smoke or fire before it spreads beyond the zone. Once the fire control system detects the fire, it relays to the smoke control system the zone and the type of alarm that was triggered. The smoke control system then takes action.
Never use manual pull stations to start the smoke control system. There is no guarantee that the person pulling the alarm is in the same smoke zone as the fire. The automatic smoke control system should take only those actions that are common to all smoke strategies when a manual pull station is activated. For example, the stairwell can be pressurized in response to a manual pull box alarm. Implementing a specific smoke control strategy must wait until the smoke detectors locate the fire zone.
Configuring and Monitoring a Smoke Control
System
The smoke control system should be able to act on its own in response to detecting smoke. When it detects smoke, the system enacts the strategy you planned out (as discussed in the design section of this article). The automatic smoke control should stick with the strategy to control smoke in the first zone that smoke is detected in. It would be difficult for you to create strategies for controlling smoke in all possible combination of zones.
The automatic smoke control system must have the highest priority over all other automatic control systems in the building. It must override energy management, occupancy schedules, or other controls. The smoke emergency will probably last only several hours, so the impact on energy management should be minimal. The only systems that should be able to automatically override the smoke control system are such safety systems as high pressure limiters.
Considering how unpredictable smoke is, you must have a manual control panel from which the smoke control system can be monitored and overridden. This panel, called a Firefighter’s Smoke Control Station (FSCS), allows firefighting personnel to take manual control of the smoke control system.
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The Fundementals of Smoke Control
Firefighter’s Smoke Control Station
The Firefighter’s Smoke Control Station (FSCS) is a graphic annunciating control panel that gives firefighters information about the state of the smoke control system as well as manual control over all of its components. The FSCS should be located in a secure room or cabinet to prevent unauthorized personnel from tampering with it. The room or cabinet should be clearly marked so that firefighters can quickly locate the FSCS.
The Fireman’s Smoke Control Station panel has a diagram of the building showing the entire smoke control system, along with status lights and override switches for all of the system’s components. The diagram of the building should include all smoke control zones, all of the ducts leading to and from the zones with arrows indicating the direction of air flow in the ducts, and a clear indication of which zone each piece of equipment serves.
The panel must have controls to activate all fans, dampers, and other equipment related to the smoke control system. These manual controls must be able to override all automatic control of smoke control equipment. In particular, the FSCS must be able to override:
•Hand/off/auto switches
•Local start/stop switches on fan motor controllers
•Freeze detection devices
•Duct smoke detectors
The FSCS must not override such safety controls as:
•Electrical overload protection
•Maintenance personnel’s electrical disconnects
•High limit pressure switches
•Any fire/smoke damper thermal control as required by UL33 (standard for heat responsive links for fire protection service), heat responsive links, or UL555S (the standard used for leakage rated dampers for use in smoke control systems).
In non-dedicated systems, local motor controller’s hand/off/auto switches can remain in-circuit with the FSCS panel. But, they can remain in-circuit only if the switches are in a locked room accessible only to authorized personnel. Also, if such a switch is thrown, a trouble alarm must sound in the building’s main control center.
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Infinity Smoke Control Guide |
The Fundementals of Smoke Control
The indicator lights on the FSCS provide information about the functioning of the system. The following colors should be used for the FSCS indicators:
•Green—Fans and other equipment are running or dampers are open.
•Yellow—Dampers are in the closed position.
•Orange or Amber—The equipment has failed.
•Red—A fire has been detected in the area.
The FSCS has a lamp test button that turns on all the panel’s lights. Use this button regularly to make sure none of the lights has burned out.
The FSCS gets information on the status of the smoke control system’s equipment from proof monitors on the equipment itself. Each fan that has a capacity over 2,000 cfm capacity should be mounted with a pressure monitor. Smoke dampers should be fitted with end-range microswitches to indicate that they are fully opened or fully closed.
All of the failure lights on the FSCS (the orange or amber ones) represent the state of the equipment as determined by the proof sensors. The failure light comes on if the piece of equipment is not in the state its control is set for within its trouble indication time. This time is 60 seconds for a fan and 75 seconds for a damper. If, within that time, the proof sensors do not report that the piece of equipment has responded to the control system’s command, the FSCS indicates that the piece of equipment has failed.
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The Fundementals of Smoke Control
Testing the System
During the installation, you should perform operational tests that make sure the components and subsystems of the smoke control system are installed correctly. After the installation is done, you must perform acceptance tests, to prove that the smoke control system is capable of doing what it was designed to do. The testing procedures are covered in a later chapter of this manual.
Bibliography
The National Fire Protection Association. NFPA 90A, Standard for the Installation of Air Conditioning and Ventilating Systems. The National Fire Protection Association.
The National Fire Protection Association. 1988. NFPA 92A, Recommended Practices for Smoke Control Systems. The National Fire Protection Association.
Underwriters Laboratories, Inc. UL 555S, Standard for Leakage Rated Dampers for Use in Smoke Control Systems. Underwriters Laboratories, Inc.
Underwriters Laboratories, Inc. UL 555, Fire Dampers. Underwriters
Laboratories, Inc.
Underwriters Laboratories, Inc. UL 864, Control Units for FireProtective Signaling Systems. Underwriters Laboratories, Inc.
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Chapter 2
Infinity Smoke Control
System Components
This chapter presents a general overview of the Infinity smoke control system and describes the UL listed system components used, the features of each component, and their role within the system. The following components are described:
•CX9200 main controller
•SCX920S controller
•TCX840 series controllers
•TCX850 series controllers
•TCX860/865 series controllers
•EnergyLink 2500 repeater
•InfiLink 200 repeater
•InfiLink 210 repeater
•FSCS (Firefighter’s Smoke Control Station)
•Fire Panel
Infinity Smoke Control System Components
Smoke Control System Overview
Figure 2-1 shows the components that are used in an Infinity smoke control system and how they are connected together. The component descriptions in the remainder of this chapter describe in more detail the role of each component in the system. Notice that the smoke control system itself is electrically isolated from the non-smoke control components.
Figure 2-1. Smoke Control System Overview
Smoke Detectors,
Fire Detectors,
Manual Pull Boxes,
Etc.
RS-232 |
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CX9200 |
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