Related Commercial Resources CHAPTER54 FIREANDSMOKECONTROL Baiancef Aproach to Fire Protecrio.. 54.1 Shaf Pressrisation - Pressried Stairweis. 54.8 Fire aned Smoke Dameper... Fire Stopping at HVAC Pemefrations . 54.2 54.9 54.2 Pressrrized Eleveators... 54.13 Smoke Erhaust Fans. 54.3 Zowet Smoke Controf. 54.16 Smoke Movement Design Wenther Deta.. 54.3 Atrir Swoke Cowurol. 54.17 54.3 Tenabifiy System.. 54.23 Mfetiod's Usesd fo Contro! Smoke 54.5 Cowmissioning and Testing 54.24 Smoke Feedbnek.. 54.7 Extraoralonary Incidents .. 54.24 Pressrrization Sjstem Design. 54.7 Sywbois. 54.25 MOKE which causes the most deaths in fires consists of air- borne solid and liquid particles and gases produced when a PIRESAFETY ao sd s DBJECTVES entrained or otherwise mixed into the mass. In building fires smoke ouj damaging property. Stairwells and elevators frequently fill with often flows to locations remote from the fire threatening life and PREVENT IGNMION FIRE BFFECT MANAGE ASHRAE. smoke thereby blocking or inhibiting evacuation. The idea of using pressurization to prevent smke infiltration of stairwells began to attract attention in the late 1960s. This concept 2019 was followed by the idea of the pressure sandwich (L.e. venting or exhausting the fire floor and pressurizing the surrounding floors). CONTROL SOURCEFUEL CONTROL CONTROL MANAGE FUEL EXPOSURE* MANAGE Frequently a building's HVAC system is used for this purpose. SOURCES [INTERACTI0NS] THREAT* This chapter focuses on smoke control systems in buildings ‘Jesn including the relationship between smoke control and HVAC. A N: e l ise ofmy ti tois thl be sd me the ftrel and esposure efre. e|bu|s smoke control system is an engineered system that modifies smoke movement for the protection of building occupants firefighters and Fig. 1 Simplified Fire Proteetion Decision Tree property. The focus of code-mandated smoke control is life safety. For an extensive technical treatment of smoke control and related Historically fire safety professionals have considered the HVAC topics see the Handbook of Smoke Cotrof Engineering (Klote et al. system a potentially dangerous penetration of natural building 2012) referred to in this chapter as the Smoke Control Handfbook. membranes (walls floors etc.) that can readily transport smoke For those interested in the theoretical foundations of smoke control and fire. For this reason HVAC has traditionally been shut down the Smoke Coetrol Hfandbook includes an appendix of derivations of flow but does not prevent ducted smoke movement caused by when fire is discovered; this prevents fans from forcing smoke equations. National Fire Protestion Association (NFPA) Standard 92 pro- developed to address smoke movement; however smoke control buoyancy stack effect or wind. Smoke control methods have been vides information about smoke control systems for buildings. For further information about heat and smoke venting for large industrial should be viewed as only one part of the overall building fire pro- and storage buildings se NFPA Srandard 204. tection system. The objective of fire safety is to provide some degree of protec- tin fr abildings ccupants te buiding and prperty insid it BALANCED APPROACHTO FIRE and neighboring buildings. Various forms of analysis have been used PROTECTION to quantify protection. Specific life safety objectives differ with Many codes and standards seek a balanced aproach to fire pro- occupancy for example nursing homes have different requirements tection consisting of detection suppresion and occupant protec- than office buildings do. tion. This approach results in highly reliable protection from the Two basic approaches to fire protection are (1) to prevent fire threat of fire. A NFPA study (Ahrens 2017) based on data from the ignition and (2) to manage fire effects. Figure I shows a decision tree National Fire Incident Reporting System peovides reliability infor- for fire protection. Building occupants and managers have the pri- mation for automatic sprinkler protection. The report states “In fires mary role in preventing fire ignition though the building design considered large enough to activate the sprinkler sprinklers operated q 92% of the time. Sprinklers were effective in controlling the fire in Because it is impossible to prevent fire ignition pletely 96% of the fires in which they operated. Taken together sprinklers managing fire's effects is significant in fire protection design. Exam- both operated and were effective in 88% of the fires large enough to ples include partmentation suppression control of construction operate them." This means that sprinklers have an overall reliability materials exit systems and smoke control. The SFPE Handbook of of 88% (or put another way an overall failure rate of 12%). Fire Protection Engineering (SFPE 2016) contains detailed fire In general such reliability data are not available for other fire safety information. struction fire stopping or smoke control. Smoke control is par- safety features such as detectors fire alarms fire-resistant con- ticularly important because it provides protection for occupants The preparation of this chapter is assigned to TC 5.6 Control of Fire and from the threat of smoke. It is generally recognized that fires that Smoke. have resulted in loss of life have had failures of one or more fire 54.1
54.2 2019ASHRAEHandbook-HVAC Applications(SI) safety features. With the balanced approach if one or more fire pa ous p y qo d ss op and (5) resisting passage of smoke (smoke dampers) Dampers that f prottion trby providing greater reliability f fire pt- safety feature fails other features will continue to provide a level bination fire and smoke dampers. All dampers should be in- tion than any single system. stalled in accordance with manufacturer’s remendations. For moredald ifmtinb dmer ildingl 2.FIRE STOPPING ATHVAC PENETRATIONS owchatristittrtltiF Although most of this chapter discusses smoke control fire man- and Fellker (2009). agement at HVAC penetrations is also a concem. Fire-rated assem- The UL Stamdard 555 series (555 555S and 555C) includes reli- blies (e.g. floor or walls) keep the fire in a given area for a specific ability testing provisions for each type of damper the heat- gsuoi sd d responsive device and the actuator (if used). Among the tests are plumbing HV AC ductwork munication cables or other ser- vice.Thrfore frs systems arstalldtmantan than cycling (20 000 full cycles for two-position dampers and 100 000 accelerated lifespan testing hose stream spray levated tempera cycles for modulating dampers) structural integrity salt spray for of the fire-rated assembly. The rating of a fire stop system depends on the number size and type of penetrations and the construction as- tures and leakage. sembly in which it is installed. Performance of the entire fire stop system which includes the Fire Dampers construction assembly with its penetrations is tested under fire con- ditions by recognized independent testing laboratories. ASTM Fire dampers are intended to prevent the spread of flames from Stamdard E814 and UL Stamdarf 1479 describe ways to determine one part of the building to another through the ductwork. They are performance of through-penetration fire stopping (TPFS). gaps of up to 9.5 mm are alled fr operating clearmces.Fie not expected to prevent airflow between building spaces because TPFS is required by building codes under certain circumstances for specific construction types and occupancies. In the United dampers are rated to indicate the time they can be exposed to flames sd soud so pb sap pou s and still maintain their integrity with typical ratings of 3 h 1.5 h 1 ASTM Stamudard E814 testing TPFS classifications are published h and less than 1 h. Fire dampers are two-position devices (open or by testing laboratories. Each classification is proprietary and each qudo q sdp an (m closed) and are usually of either the multiblade (Figure 2) or curtain applies to use with a specific set of conditions so mumerous ypes poofoud uaar8 Kue uo panbau Aensn an fusible link and are spring loaded In a fire hot gases cause this link The construction manager and general contractor not the archi- to e art sothat th pingmakesthblesam shtmea tects and engineers make work assignments. Sometimes they assign plications use other heat-responsive devices in place of fusible links. fire stopping to the discipline making the penetration; other times Typically curtain dampers are also held open by a fusible link that they assign it to a specialty fire-stopping subcontractor. The Con- on gravity to make the blades close offthe pening bt hrizntal es apart when heated. Vertical static curtain dampers often rely 9 ndos-ay sse (st0 IS) asu sood uans specifications to Division 7 Themmal and Moisture Protection which (ceiling) and all dynamic curtain dampers must have spring closure. Dynamic dampers are for applications where the damper may e e • Encourages continuity of fire-stopping products on the project quired to close against airflow such as an HVAC system that remains by consolidating their requirements (e.g. TPFS expansion joint dampers are usully made and labeled in accordance with UL Sam- operational for smoke control purposes. In the United States fire • Maintains flexibility of work assignments for the general fire stopping floor-to-wall fire stopping etc.) where air ducts penetrate or teminate at openings in walls or parti dard 555. This standard addresses fire dampers intended for use (1) • Encourages prebid discussions between the contractor and sub- contractor and construction engineer tions (2) in air transfer openings and (3) where air ducts extend contractors regarding appropriate work assignments through floors. 3.FIRE AND SMOKE DAMPERS Ceiling Radiation Dampers Dampers are used for one or more of the following purposes: (1) Ceiling radistion dampers are designed and tested to UL Stam- balancing flow by adjusting airlow in HVAC system ducts (2) con- dlnd 555C. These dampers prevent heat transfer they have some trollingflow forHVAC purposes) (3)resisting passage offire fire dampers) (4) resisting het transfer (ceiling radiation dampers) resistance to fire and smoke but are not tested for fire and smoke passage. 99 SHAFT BLADE EXT[NSION EXTENSION SHAFT BLADE O SECTION PARALLEL-BLAQE DAMPER SECTION QPPOSED-BLADE DAMPER Fig 2 Multiblade Dampers
Fire and Smoke Control 54.3 BLADES NORMAL STACK EFFECT REVERSE STACK EFFECT MS FUSIBLE NEUTRAL LINK DANE TRACKS GUIDE N;tc: Arows indicale direction of air mov FRAME - Fig 4 Air Movement Caused by Normal and smoke control systems for many locations in the United States Can- Reverse Stack Effeet Fig. 3 Curtain Fire Damper ada and other countries. Wind is measured at weather stations which are often at airports. Because lcal terain has significant fft n wind wind speeds a Smoke Dampers uspuspe moge oeu a ss peasuoq qou e ponseu asoq uog uap an ensn aue sas oafod ou] Smoke dmpers arentened toseal tighly tprevent the sd of smoke from one part of the building to another through the wind speed to a project site see Chapter 3 of the Smoke Controf ASHRAE. ductwork and to allow an engineered smoke control system to build Handbook and Chapter 24 of the 2017 ASHRAE HandbookFiu- j st aduep axous y suepunq ouoz soe smssnd dn dumentals. from spreading Smoke dampers are of the mltiblade design (Fig required to withstand high temperature and will not prevent a fire 6.SMOKEMOVEMENT ure 2) and may be listed for either two-position (open and closed) A smoke control system needs to be designed so that it is not p s overpowered by the driving forces that cause smoke movement: vice can be used as bination smoke and HV AC dampers.In the stack effect buoyancy xpansion wind forced ventilation an le ‘Jesn United States smoke dampers are usually made and classified for vator piston effect. In a building fire smoke is usually moved by a leakage in accordance with UL Stamdard 555S. This standard bination of these forces. ebus includes construction requirements; air leakage tests; and endur- ance tests of cycling temperature degradation salt-spray exposure Stack Effect and operation under airflow. Combination fire and smoke dampers It is mon to have an upward flow of air in building shafts ply with the dynamic fire damper requirements of UL Stamdard dumbwaiters and mechanical shafs. The upward fow is casedby during winter. These shafts include stairwells elevator shafts 555 and with the smoke damper requirements of UL Srandaral 555S. the buoyancy of warm air relative to the cold outdoor air. This Corridor Dampers upward flow is similar to the uward flow in smke stacks adiis Corridor dampers are bination fire and smoke dampers that from this analogy that the upward flow in shafts got the name stack are tested for horizontal installation in ceilings. They have sleeves effect. In summer flow in shafts is downward Upward flow in designed for this application and allow use of front grilles for access shafts is called normal staek effeet and downward flow is called to the damper and actuator. Corridor dampers need to be tested to reverse stack effeet. UL Stamdards 555 and 555S for 1 h at 0.76 m/s. Figure 4 shows both kinds of stack effect. In normal stack effect air flows into the building below the neutral plane flows up building 4.SMOKE EXHAUST FANS shafts and out of the building above the neutral plane. The neutral Typically smoke control systems for buildings are designed to plane is a horizontal plane where pressure inside the shaft equals outdoor pressure and is often near the midheight of a building. avoid the need for operation at elevated temperatures. For zoned At standard atmospheric pressure the pressure difference caused smoke control systems usually the zone being exhausted is much larger than the fire space and this limits the gas temperature at the by either normal or reverse stack effect is expressed as exhaust fan. For atrium smoke control systems air is entrained in the smoke plume that rises above the fire and this entrained air Pso 3460 1 (1) reduces the temperature of the smoke exhaust. ASHRAE Standard 149 establishes uniform methods of labora- tory testing and test documentation for fans used to exhaust smoke in smoke control systems. βso = pessure diffeenc fom shff to ondoes Pa 7 = absolute temperature of shaft K 5. DESIGN WEATHER DATA To absolute temperature of outdoors K 2 = distance above neutral plane m The performance of smoke control systems can depend on Figure 5 diagrams the pressure diffrence between a building outdoor temperature and wind. Chapter 2 of the Smoke Control shaft and the outdoors. A positive presure difference indicates that Handbook lists design climatological data (winter and summer tem- shaft pressure is higher than the outdoor pressure and a negative peratures wind speed standard barometric pressure) for design of pressure difference indicates the opposite. For a building 60 m tall
54.4 cations(SI) by a network flow model such as CONTAM (see the section on Computer Analysis). Buoyaney High-temperature smoke has buoyancy because of its reduced dqpmsd oaesy 54 ment and its surroundings can be expressed as follows: NEUTRALPLANE 209S (2) where Prs pse diffee frmfre catmt t suoning Pa 7s = absolute temperature of surroundings K 2 = distance above neutral plane m BOTTOM OF BUILDING NEGATIVE (-) 0 T average absolute temperature of fire partment K PRESSURE DIFFERENCE Po The neutral plane is the plane of equal hydrostatic pressure be- tween the fire partment and its surroundings. For a fire with a Fig. 5 Pressure Difference Between Building Shaft and fire partment temperature at 800°C (1073 K) the pressure dif- Outdoors Caused by Normal Stack Effect ference 1.5 m above the neutral plane is 13 Pa. Fang (1980) studied with a neutral plane at midheight an outdoor temperature of 18°C pressures caused by room fires during a series of full-scale fire tests room wall t the ceiling. Much larger presure differences are pos- and found a maximum pressure difference of 16 Pa across the bum (255 K) and an indoor temperature of 21°C (294 K) the maximum pressure difference from stack effect is 54 Pa. This means that at the sible for tall fire partments where the distance z from the neu- top of the building pressure inside a shaft is 54 Pa greater than the tral plane can be larger. outdoor presure. At the base of the building pressure inside a shaff is 54 Pa lower than the outdoor pressure. In sprinkler-controlled fires the temperature in the fire room re- mains at that of the surroundings except for a short time before sprin- Smoke movement from a building fire can be dominated by kler activation. Sprinklers are activated by the ceiling jet which is a stack effect In a building with nomal stack effect the existing ait layer of hot gas under the ceiling. The ceiling jet's maximum tem- 2) currents (as shown in Figure 4) can move smoke considerable dis- perature depends on the fire’s location activation temperature of the 2 tances from the fire origin. If the fire is below the neutral plane sprinker andthmallgofte sinklr’satrepnsivelm 3 smoke moves with building air into and up the shafts. This upward For most rsidential and cmercial applicatios the ceiling t is smoke flow is enhanced by buoyancy forces from the smoke tem- between 80 and 150°C. In Equation (2) TF is the average tempera- perature. Once above the neutral plane smoke flows from the ture of the fire partment. shafts into the upper floors of the building. If leakage between For a sprinkler-controlled fire floors is negligible floors below the neutral plane except the fre floor) remain relatively smoke free until more smoke is produced T = H(HH) H (3) than can be handled by stack effect flows. Smoke from a fire located above the neutral plane is carried by where building airflow to the outdoors through exterior openings in the Ty average absolute temperature of fre partment K building If leakage between floors is negligible al floors other than 7 = absolute temperature of suroundings K the fire floor remain relatively smoke free until more smoke is pro- H floe-fo-ceiling height m duced than can be handled by stack effect flows. When leakage H - thickness of ceing jet m between floors is considerable smoke flows to the floor above the T = absolute temperature of ceiling jet K fire floor. pue 6 0 *w 1o u s’ oI aex Air currents caused by reverse stack effect (see Figure 4) tend to 150 273 423 K the average absolute temperature of the fire - move relatively cool smoke down. In the case of hot smoke buoy- partment is ancy forces can cause smoke to flow upward even during reverse T = [293(2.5 0.1) 423 ×0.1/2.5 = 298 K or 25°C stack effect conditions. difference of 0.5 Pa which is insignificant for smoke control applica- In Equation (2) this value of T and z of 1.5 m results in a pesure Caution: It is a myth that the pressure difference caused by stack effect is nearly proportional to the temperature difference between tions. the building and the outdoors. Instead this pressure difference is nearly proportional to the temperature difference between ashgfr and Expansion the outdoors. Looking at Figure 4 it is easy to see how the shaft and Energy released by a fire can also move smoke by expansion. In building temperatures might be considered identical. Often they are a fire parment with only one pening to the building building the same. However shafts that have one or more walls on the outside air flows in and hot smoke flows out. Neglecting the added mass of of the building tend to be relatively cold im winter and warm in the fuel which is small pared to airflow the ratio of volumetric summer and this can have a major influence on stack effect. flows can be cxpressed as a ratio of absolute temperatures: For a building with shafts of various heights and different shaft temperatures the flows bee very plicated and would not (4) resemble those in Figure 4. Each shaf could have its own neutral uos where tral plane. Equation (1 is not applicable for such plicated build- volumetic flow rate of smoke out of fire partment ms ings but the flows and pressures in such buildings can be analyzed V = volumetric flow rate of air into fire partment m2/s
Fire and Smoke Control 54.5 absolute temperature of air entering fire partment K absolute temperature of smoke leaving fire partment K ratio of volumetric flows is 3.32. Note that absolute temperatures For smoke at 700°C (973 K) and entering air at 20°C (293 K) the ment at 1.5 m/s thcn smoke flows out at 5.0 m/s with the gas are used in the calculation. In such a case if air enters the part- SNGLEI-CAR expanding to more than three times its original volume. SHAFT Fora fire partment with open doors or windows the pressure difference across these openings caused by expansion is negligible. QUADRUPLE. CAR SHAF However for a tightly sealed fire partment the pressure differ- ences from expansion may be important. DOUBLE-CAR SHAFT Wind In many instances wind can have a pronounced effect on smoke movement within a building. The pressure that wind exerts on a wall CAR VELOCITY m/s 3 4 is Fig. 6Caleulated Upper Limit of Piston Effeet Across (5) Elevator Lobby Doors. where wind pressure Pa SPus AAU (6) C -prsue cefficie P outdoo ar density kgm Uy = velocity at wall height H m/s where ou] The pressure coefficient C depends on wind direction building upelimit prese iffre fm shaf oblng Pa ASHRAE. geometry and local obstructions to the wind. The pressure coeffi- cros-sectiomal area of shaf m² p = air density in boistway. kg/m cients are in the range of 0.8 to 0.8 with positive values for wind- ward walls and negative for leeward walls. A = effective area m² U elevtor car velocity，ms Frequently a window breaks in the fire partment. If the fr oud lr car m² window is on the leeward side of the building the negative pressure A =Iaage area betw blding nd lbby m² caused by the wind vents the smoke from the fire partment. This C flow coeffcient for flow aroumd car 9 reduces smoke movement throughout the building. However if the The flow coeficient C was determined experimentally at about ‘Jesn broken window is on the windward side wind forces the smoke 0.94 for a multiple-carhoistway and 0.83 for asinglecarhoistway. throughout the fire floor and to other floors which endangers the The free area around the elevator car is the cross-sectional area of e(bu|s lives of building occupants and hampers firefighting. Wind-induced the shaft less the cross-sectional area of the car. Effective areas are pressure in this situation can be large and can dominate air move- ment throughout the building. For more detailed information about discussed in the section on Height Limit. wind and smoke control see Chapter 3 of the Smoke Controf Hand- the building for normal elevator car velocities from I to 5 m/s. All Figure 6 shows the upper limit of piston effect from the lobby to book. elevator velocities are in this range except for those in extremely tall Forced Ventilation shafts and elevators that ravel at relatively high velocities in single- buildings. Figure 6 shows that piston effect is greatest for single-car stand fires and either shut dowm in the event of a fire or go into a Modern HVAC systems are built of materials intended to with- car shafts have the potential for piston effect that may adversely smoke cotrolme fopeationFor details nthe lattrapprach affect smoke control performance. see the section on Zoned Smoke Control. 7.METHODS USEDTO CONTROLSMOKE Elevator Piston Effect In this chapter smoke control includes all methods that can be The transient pressures and flows produced when an elevator car used singly or in bination to modify smoke movement to pro- moves in a shaft are called piston effeet and can pull smoke into a tect occupants or firefighters or reduce property damage. These normally pressurized elevator lobby or elevator shaft. For a validat- methods are (1) partmentation (2) dilution (3) pressurization ed analysis of piston effect see Klote (1988) and Klote and Tamura the following sections. (4) airflow and (5) buoyancy. These mechanisms are discussed in (1986 1987). In the absence of stack effect or other driving forces pressure Compartmentation above a rising elevator car is higher than that below the car. For this Barriers that can remain effective throughout a fire exposure upward-moving car there is airflow into the shaf below thecat and have lng becn used to protect against fire spread. In this approach airflow out of the shaft above the car. When the car passes a floor walls partitions floors doors and other barriers provide some the pressure difference across the elevator door on that floor sud- level of smoke protection to spaces remote from the fire. Passive closed doors (enclesed lobbies) the pressure difference across th denly drops and then increases. For elevators with lobbies that have smoke control consists of using barriers alone (or without pressur- closed lobby doors reacts in a similar way to elevator car motion. ization) Using partmentation with pressurization is discussed in the section on Pressurization (Smoke Control). Passive smoke For a car traveling from the bottom to the top of the shaff the control systems can be analyzed with the goal of providing a tenable largest value of pressure difference from piston effect is at the top of environment at specific locations during a fire. For more informa- the shaft; for a car traveling from the top to the bottom the largest value is at the bottom ofthe shaft. This largest value of pressure dif. the Lijfe Sefery Codes (NFPA 2012) and the ftermariomal Building tion see the section on Tenability Systems. Many codes such as ference (called the piston effect) for an elevator with enclosed lob- Codes (ICC 2012) provide speeifie criteria for construction of pas- bies is sive smoke barriers (including doors) and their smoke dampers. The
Ashrae 2019 防火和烟雾控制标准.pdf
