1、53.1CHAPTER 53FIRE AND SMOKE CONTROLFire Management . 53.1Fire and Smoke Dampers. 53.2Smoke Exhaust Fans. 53.3Design Weather Data. 53.3Smoke Movement . 53.3Smoke Control 53.5Pressurization System Design 53.7Shaft Pressurization . 53.8Pressurized Stairwells 53.8Pressurized Elevators. 53.12Zoned Smoke
2、 Control . 53.15Atrium Smoke Control 53.16Tenability Systems 53.22Commissioning and Testing . 53.22Extraordinary Incidents . 53.23Symbols 53.23MOKE, which causes the most deaths in fires, consists of air-S borne solid and liquid particles and gases produced when amaterial undergoes pyrolysis or comb
3、ustion, together with air that isentrained or otherwise mixed into the mass. In building fires, smokeoften flows to locations remote from the fire, threatening life anddamaging property. Stairwells and elevators frequently fill withsmoke, thereby blocking or inhibiting evacuation.The idea of using p
4、ressurization to prevent smoke infiltration ofstairwells began to attract attention in the late 1960s. This conceptwas followed by the idea of the pressure sandwich (i.e., venting orexhausting the fire floor and pressurizing the surrounding floors).Frequently, a buildings HVAC system is used for thi
5、s purpose. Thischapter discusses smoke control systems and fire management inbuildings, including the relationship with HVAC. A smoke controlsystem is an engineered system that modifies smoke movement forthe protection of building occupants, firefighters and property. Thefocus of code-mandated smoke
6、 control is life safety.For an extensive technical treatment of smoke control and relatedtopics, see the Handbook of Smoke Control Engineering (Klote et al.2012), referred to in this chapter as the Smoke Control Handbook.For those interested in the theoretical foundations of smoke control,the Smoke
7、Control Handbook includes an appendix of derivations ofequations.National Fire Protection Association (NFPA) Standard 92 pro-vides information about smoke control systems for buildings. Forfurther information about heat and smoke venting for large industrialand storage buildings, refer to NFPA Stand
8、ard 204.The objective of fire safety is to provide some degree of protec-tion for a buildings occupants, the building and property inside it,and neighboring buildings. Various forms of analysis have been usedto quantify protection. Specific life safety objectives differ withoccupancy; for example, n
9、ursing home requirements are differentfrom those for office buildings.Two basic approaches to fire protection are (1) to prevent fireignition and (2) to manage fire effects. Figure 1 shows a decision treefor fire protection. Building occupants and managers have the pri-mary role in preventing fire i
10、gnition, though the building designteam may incorporate features into the building to support this effort.Because it is impossible to prevent fire ignition completely, manag-ing fires effects is significant in fire protection design. Examplesinclude compartmentation, suppression, control of construc
11、tionmaterials, exit systems, and smoke control. The SFPE Handbook ofFire Protection Engineering (SFPE 2008) and the Fire ProtectionHandbook (NFPA 2008) contain detailed fire safety information.Historically, fire safety professionals have considered the HVACsystem a potentially dangerous penetration
12、of natural buildingmembranes (walls, floors, etc.) that can readily transport smokeand fire. For this reason, HVAC has traditionally been shut downwhen fire is discovered; this prevents fans from forcing smokeflow, but does not prevent ducted smoke movement caused bybuoyancy, stack effect, or wind.
13、Smoke control methods have beendeveloped to address smoke movement; however, smoke controlshould be viewed as only one part of the overall building fire pro-tection system.1. FIRE MANAGEMENTAlthough most of this chapter discusses smoke control, fire man-agement at HVAC penetrations is also a concern
14、. The most efficientway to limit fire damage is through compartmentation. Fire-ratedassemblies (e.g., floor or walls) keep the fire in a given area for a spe-cific period. However, fire can easily pass through openings forplumbing, HVAC ductwork, communication cables, or other services.Therefore, fi
15、re stop systems are installed to maintain the rating of thefire-rated assembly. The rating of a fire stop system depends on thenumber, size, and type of penetrations, and the construction assemblyin which it is installed.Performance of the entire fire stop system, which includes theconstruction asse
16、mbly with its penetrations, is tested under fire con-ditions by recognized independent testing laboratories. ASTM Stan-dard E814 and UL Standard 1479 describe ways to determineperformance of through-penetration fire stopping (TPFS).TPFS is required by building codes under certain circumstancesfor sp
17、ecific construction types and occupancies. In the United States,the model building codes require that most penetrations pass ASTMStandard E814 testing. TPFS classifications are published by testinglaboratories. Each classification is proprietary, and each applies touse with a specific set of conditi
18、ons, so numerous types are usuallyrequired on any given project.The preparation of this chapter is assigned to TC 5.6, Control of Fire andSmoke.Fig. 1 Simplified Fire Protection Decision Tree53.2 2015 ASHRAE HandbookHVAC ApplicationsThe construction manager and general contractor, not the archi-tect
19、s and engineers, make work assignments. Sometimes they assignfire stopping to the discipline making the penetration; other times,they assign it to a specialty fire-stopping subcontractor. The Con-struction Specifications Institute (CSI) assigns fire-stopping specifi-cations to Division 7, whichEncou
20、rages continuity of fire-stopping products on the project byconsolidating their requirements (e.g., TPFS, expansion joint firestopping, floor-to-wall fire stopping, etc.)Maintains flexibility of work assignments for the general contrac-tor and construction engineerEncourages prebid discussions betwe
21、en the contractor and sub-contractors regarding appropriate work assignments2. FIRE AND SMOKE DAMPERSDampers are used for one or more of the following purposes: (1)balancing flow by adjusting airflow in HVAC system ducts, (2) con-trolling flow (for HVAC purposes), (3) resisting passage of fire (fire
22、dampers), and (4) resisting passage of smoke (smoke dampers).Dampers that are intended to resist the passage of both fire andsmoke are called combination fire and smoke dampers. For moredetailed information about dampers, including pressure losses, flowcharacteristics, actuators, installation, and b
23、alancing, see Felker andFelker (2009).Fire DampersFire dampers are intended to prevent the spread of flames fromone part of the building to another through the ductwork. They arenot expected to prevent airflow between building spaces, becausegaps of up to 3/8 in. are allowed for operating clearances
24、. Firedampers are rated to indicate the time they can be exposed to flamesand still maintain their integrity, with typical ratings of 3 h, 1 1/2 h,1 h, and less than 1 h. Fire dampers are two-position devices (openor closed), and are usually of either the multiblade (Figure 2) or cur-tain design (Fi
25、gure 3). Most multiblade fire dampers are held openby a fusible link and are spring loaded. In a fire, hot gases cause thislink to come apart so that the spring makes the blades slam shut.Some manufacturers use other heat-responsive devices in place offusible links. Typically, curtain dampers are al
26、so held open by a fus-ible link that comes apart when heated. Curtain dampers often relyon gravity to make the blades close off the opening, but horizontal(ceiling) curtain dampers must have spring closure.In the United States, fire dampers are usually made and labeledin accordance with UL Standard
27、555. This standard addresses firedampers intended for use (1) where air ducts penetrate or terminateat openings in walls or partitions, (2) in air transfer openings, and (3)where air ducts extend through floors.Fire dampers are evaluated for use as static, dynamic, or combi-nation fire and smoke dam
28、pers. Static dampers are for applicationswhere the damper will never have to close against an airstream, suchas when HVAC systems are automatically shut down when a fire isdetected. Dynamic dampers are for applications where the dampermay be required to close against airflow, such as an HVAC systemt
29、hat remains operational for smoke control purposes. UL Standard555 also applies to ceiling dampers and ceiling diffusers intendedfor use in hourly-rated fire-resistive floor/ceiling and roof/ceilingassemblies.Smoke DampersSmoke dampers are intended to seal tightly to prevent the spreadof smoke from
30、one part of the building to another through the build-ings ductwork, and to allow an engineered smoke control system tobuild up pressures across zone boundaries. A smoke damper is notrequired to withstand high temperature and will not prevent a firefrom spreading. Smoke dampers are of the multiblade
31、 design (Fig-ure 2), and may be either two-position devices (open and closed), ormay be modulated between the open and closed positions to serve asboth a smoke damper and a control damper.In the United States, smoke dampers are usually made and clas-sified for leakage in accordance with UL Standard
32、555S. Thisstandard includes construction requirements; air leakage tests; andendurance tests of cycling, temperature degradation, salt-sprayexposure, and operation under airflow.Fig. 2 Multiblade DampersFig. 3 Curtain Fire DamperFire and Smoke Control 53.3Each smoke damper o pass testing for (1) rel
33、iability, (2) temper-ature resistance, and (3) air leakage resistance. The operational testconfirms proper smoke damper operation after 20,000 cycles, or100,000 cycles for modulating smoke dampers. The temperaturetest confirms proper smoke damper operation after 30 min exposureto elevated temperatur
34、es. Smoke dampers must meet the require-ments at a minimum temperature of 250F, and may receive highertemperature ratings in increments of 100F.After the reliability and temperature resistance tests, the air leak-age test is conducted. UL defines air leakage classes by the maxi-mum allowable leakage
35、 through the closed smoke damper at aminimum pressure difference of 4.5 in. of water. The smoke damperclasses are I, II, and III, and the leakages of these damper classes arelisted in Table 1.Designers can use these leakage classes to specify smoke damp-ers. At a location where very little smoke lea
36、kage is acceptable, aclass I damper may be needed. Where some smoke leakage will notadversely impact smoke control performance, a class II or IIIdamper may be appropriate. Combination fire and smoke damperscomply with the dynamic fire damper requirements of UL Standard555 and with the smoke damper r
37、equirements of UL Standard 555S.3. SMOKE EXHAUST FANSTypically, smoke control systems for buildings are designed toavoid the need for operation at elevated temperatures. For zonedsmoke control systems, usually the zone being exhausted is muchlarger than the fire space, and this limits the gas temper
38、ature at theexhaust fan. For atrium smoke control systems, air is entrained inthe smoke plume that rises above the fire, and this entrained airreduces the temperature of the smoke exhaust.ASHRAE Standard 149-2000 (reaffirmed in 2009) establisheduniform methods of laboratory testing and test document
39、ation forfans used to exhaust smoke in smoke control systems.4. DESIGN WEATHER DATAChapter 2 of the Smoke Control Handbook lists design climato-logical data for design of smoke control systems for many locationsin the United States, Canada, and other countries. These data con-sists of winter tempera
40、ture, summer temperature, and wind speed.Standard barometric pressure at these locations is also listed. Wind is measured at weather stations, which are often at airports.Because local terrain has a significant effect on wind, wind speedsat project sites are usually very different from those measure
41、d atneighboring weather stations. For information about adjustingdesign wind speed to a project site, see Chapter 3 of the Smoke Con-trol Handbook and Chapter 24 of the 2013 ASHRAE HandbookFundamentals.5. SMOKE MOVEMENTA smoke control system must be designed so that it is not over-powered by the dri
42、ving forces that cause smoke movement: stackeffect, buoyancy, expansion, wind, forced ventilation, and elevatorpiston effect. In a building, fire smoke is usually moved by a com-bination of these forces.Stack EffectIt is common to have an upward flow of air in building shafts dur-ing winter. These s
43、hafts include stairwells, elevator shafts, dumb-waiters, and mechanical shafts. The upward flow is caused by thebuoyancy of warm air relative to the cold outdoor air. This upwardflow is similar to the upward flow in smoke stacks, and it is from thisanalogy that the upward flow in shafts got the name
44、 stack effect. Insummer, flow in shafts is downward. Upward flow in shafts is callednormal stack effect, and downward flow is called reverse stackeffect.Figure 4 shows both kinds of stack effect. In normal stack effect,air flows into the building below the neutral plane, flows up buildingshafts, and
45、 out of the building above the neutral plane. The neutralplane is a horizontal plane where pressure inside the shaft equalsoutdoor pressure, and is often near the midheight of a building.At standard atmospheric pressure, the pressure difference causedby either normal or reverse stack effect is expre
46、ssed aspSO= 7.63 z (1)wherepSO= pressure difference from shaft to outdoors, in. of waterTS= absolute temperature of shaft, RTO= absolute temperature of outdoors Rz = distance above neutral plane, ftFigure 5 diagrams the pressure difference between a buildingshaft and the outdoors. A positive pressur
47、e difference indicates thatshaft pressure is higher than the outdoor pressure, and a negativepressure difference indicates the opposite. For a building 200 ft tallwith a neutral plane at midheight, an outdoor temperature of 0F(460R), and an indoor temperature of 70F (530R), the maximumpressure diffe
48、rence from stack effect is 0.22 in. of water. This meansthat, at the top of the building, pressure inside a shaft is 0.22 in. ofwater greater than the outdoor pressure. At the base of the building,pressure inside a shaft is 0.22 in. of water lower than the outdoorpressure.Smoke movement from a build
49、ing fire can be dominated by stackeffect. In a building with normal stack effect, the existing air cur-rents (as shown in Figure 4) can move smoke considerable distancesfrom the fire origin. If the fire is below the neutral plane, smokemoves with building air into and up the shafts. This upward smokeflow is enhanced by buoyancy forces from the smoke temperature.Once above the neutral plane, smoke flows from the shafts into theTable 1 UL Standard 555S Leakage Classifications for Smoke DampersLeakage ClassMaximum Leakage at4.5 in. of water,cfm/ft28.5 in. of water,cfm/ft212.5
