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Canadian experience of fire safety in high buildings
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CANADIAN EXPERIENCE OF FIRE SAFETY I N HIGH BUILDINGS
by M. Galbreath
ANALYZED
Reprinted from Fire Safety Journal Vol. 7 (1 984) p. 87 - 9 1
DB R Paper No. 1 177
Division of Building Research
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Fire Safety Journal, 7 (1984) 87 - 9 1
Canadian Experience of Fire Safety in High Buildings
M. GALBREATHI
Division of Building Research, National Research Council Canada, Ottawa, Ont. K I A O R 6 (Canada)
I
SUMMARY
The circumstances leading t o the develop- ment in Canada during the 1970s o f special measures for life safety in high buildings are described. Examples are given o f tests carried o u t t o verify the effectiveness o f controls o n movement
o f
smoke, and reference is made t o some real fire incidents in high buildings.INTRODUCTION
High buildings are a relatively recent feature of our society. The invention of a safe passenger elevator and the development of the structural frame toward the end of the last century made such buildings possible. Early skyscrapers made much use of heavy mason- ry, and floor areas were generally subdivided into small fire compartments. To combat the new danger of fire in high buildings, tech- niques were developed such as the vertical division of a building by a fire wall with horizontal exits and the smoke-proof fire tower. These techniques, referred t o in some of our older codes, may still be useful. During the depression in the 1930s, however, con- struction of high buildings came t o a halt. When it resumed in the 1950s, the new high buildings were very different in concept and construction from those that had gone before.
The Division of Building Research first became interested in high buildings when studying the migration of moisture into exterior walls that occurred under the influ- ence of stack effect [ I ] (the pressure patterns that cause air t o flow from lower t o upper floors through the vertical shafts in heated
buildings in winter). A computer programme [2] developed t o simulate pressure patterns in a number of high buildings made it possible t o calculate the probable movement of smoke during a fire. This led t o a study of fire safety problems in high buildings [ 3
-
61 by a small group drawn from the Fire Research Section and the Energy and Services Section of the Division of Building Research.Information on the movement of people on stairs [7], based on studies by the National Bureau of Standards [8], showed that the time required t o evacuate a building increases with the number of storeys. This applies t o those buildings following U.S. and Canadian codes where the stair width is based on the population of one floor. Subsequent studies by the Division of Building Research [9] have shown that the time required for evacuation may in some cases exceed one hour, making it inevitable for most high-building occupants t o remain in the building during the firefighting.
The traditional concept of immediately starting t o evacuate a building on sounding a fire alarm came into question during 1967, when the occupants of a 22-storey office building in Ottawa were subjected t o a series of false fire a l m s . On six separate attempts t o evacuate the building the stairs became crowded, and none of the evacuations were completed in 20 t o 30 minutes.
A computer study of the probable move- ment of smoke in a 20-storey building from a fire on a lower storey indicated that un- tenable conditions would be reached in stairwells within 1 0 minutes, and on upper floors in 15 minutes [2]. It was assumed that conditions would be tolerable if the smoke from a fire floor, after reaching a steady state, was diluted by a t least 100 times its volume of clean air.
DEVELOPMENT OF BUILDING CODE PROVISIONS
The Dominion Fire Commissioner, Mr. Ross Switzer, set up a committee in 1968 t o study all aspects of fires in high buildings. On obtaining the results of this study, in 1970 the Associate Committee on the National Building Code added a new subsection 3.2.6., "Additional Requirements for High Build- ings", t o the National Building Code. This subsection contained provisions for control- ling elevators, voice communication, etc., but not limitations on smoke movement, because it was felt that more public discussion was needed before such a radical concept could be added t o the Code. In the same year, an explanatory paper on control of smoke move- ment in high buildings [ l o ] was issued, describing the problems and theories of smoke movement and outlining a number of detailed measures for controlling it.
A task group was established which held meetings over the next few years t o study the measures and consider comments from the public. In 1973 the National Building Code was amended t o require control of smoke movement, and a supplementary document
[ l l ] was issued providing a choice of mea- sures t o meet the Code conditions of life safety in high buildings. The requirements were set up so as t o leave the option of developing new solutions for the problem t o the designer, provided the basic objectives were met.
A high building was defined as one exceed- ing 1 8 m in height. This height was increased t o 3 5 m for office buildings with a limit on population that would permit total evacu- ation in about 1 0 minutes. In hospitals and nursing homes, which were considered t o be a special case because the limited mobility of the occupants increased the required evacu- ation time, smoke control measures were required for all buildings over 3 storeys high.
The measures for smoke control developed by the National Building Code have been criticized for allowing too many choices. However, smoke control systems have t o be tailored t o individual buildings and their occupants, who may be awake, asleep or handicapped. In an office building, for example, occupants may be assumed t o be awake; thus a fire will be discovered at an
early stage. On the other hand, in a residential building most occupants may be asleep and the probable detection and evacuation times will be longer. Hospitals have the added problem that some occupants can be moved only with great difficulty.
The measures described in the Supplement t o the National Building Code vary in their objectives. In some, occupants are protected on all floors other than the fire floor and the one immediately above. In others, movement t o a place of relative safety following an alarm is required.
FIRES IN HIGH BUILDINGS
Because of the delay before the National Building Code is adopted by the provinces, one or two years may elapse before the effects of the changes appear in buildings. We have not yet experienced a major fire in a building equipped with smoke control mea- sures. Problem fires, such as the one a t Inn on the Park, Toronto in January 1981 where smoke spread into upper floors in great quantity, are clearly the result of stack effect acting on fires that start at a low level. How- ever, if a fire occurs on a floor above the neutral plane, the smoke tends t o flow t o the outdoors when the windows break, reducing the smoke problem for occupants of other floors.
Fires in buildings not protected against smoke movement have illustrated some of the problems that may occur. A fire in the Chateau Champlain Hotel [12] in Montreal in December 1967, shortly after it had opened, was an example of a fire on a lower floor where smoke reached the upper floors through elevator and stair shafts. The fire occurred a t night in a restaurant, and smoke was drawn t o the elevator lobby and up the shaft t o the upper floors by stack effect. The elevator machinery room at the top of the shaft was vented t o the outside as required by the elevator code a t that time. The 60 guests on the upper floors were led t o safety, in spite of the dense smoke, by fire fighters who shared their breathing apparatus with the guests.
A similar incident occurred in January 1981 at Inn on the Park, Toronto. A fire caused by a domestic vacuum cleaner in a conference room grew t o such a size that the
windows broke on three sides of the room. The fire then spread to the elevator lobby and through the open elevator doors into the cabs. The fire caused smoke to penetrate not only through stair and elevator shafts into upper level corridors, but also through service shafts directly into suites. The hexagonal ring cor- ridor on each floor made it difficult for the firemen t o find their way about the tower. Six people died of exposure to smoke.
In a recent incident in a 40-storey apart- ment-hotel complex, fire occurred in a suite on the 18th floor, completely burning it out. Stack effect was not a factor, probably because the fire was close to the midheight, but an open door to the suite and loss of electrical power made fire fighting difficult. Smoke was drawn into the stair shafts by the air-handling system designed to pressurize the corridors. There was only one death, in a stairwell, but many people were exposed t o smoke, making it impossible for them t o leave the building until after the fire was con- trolled.
APPLICATION OF SMOKE CONTROL SYSTEMS A survey of smoke control systems incor- porated into high buildings in Toronto between 1975 and 1980 has been made by Rolf Jensen and Associates [13]. Among 79 apartment buildings, 56 used Measure G - a system with pressurized stair and elevator shafts, but with no additional precautions to prevent smoke entry into upper floors. The next choice was Measure M, used by 20 build- ings, which permits open balconies to every suite to be considered as temporary areas of refuge. The seven office buildings and one hospital in the survey employed Measure A, which depends primarily on an automatic sprinkler system t o limit the size of the fire. A similar survey conducted in Calgary by ACPH Engineering and Construction Ltd. [14] found that among 70 apartment build- ings, 42 used Measure M (balconies), and 1 5 used Measure G (pressurized stair shafts). Of 53 office buildings, 5 1 depended on Measure A (fully sprinklered building) for life safety. Among five hotels, two were fully sprinklered and three used pressurized shafts.
It appears that in the marketplace the preference is for pressurized stair shafts in
apartment buildings if the cheaper alternative of balconies is not permitted, and for auto- matic sprinklers in office buildings. Vinto Engineering Ltd., Edmonton, in their cost comparison study of alternate smoke control measures used in typical hospital, apartment and office buildings, found that, regardless of which National Building Code smoke control method was adopted, there was little or no variation in cost.
TESTS OF SMOKE CONTROL SYSTEMS Tamura has carried out many tests of smoke control installations in high buildings. Tests of pressurized stair shafts [15] showed that the pressure drop due to the presence of stairs and landings was significant. Injecting air at the top and at intervals of not more than five storeys helped t o produce more uniform pressures. A pressure difference of 25 Pa was judged to be sufficient t o prevent smoke from entering a stair shaft when the doors t o the fire floor and t o the outside at grade were open*. Opening doors to other floors, which might occur intermittently, would reduce the effective pressure, but any small quantity of smoke entering the shaft would be diluted by the air flow through the stair shaft to the outdoors. A pressure differ- ence of 100 Pa was considered t o be the maximum desirable to allow fleeing occupants t o open the doors into the stairs.
Although excessive pressure difference across doors is a real problem, it could be alleviated by using offset hinges that permit the door to swivel about its centre, in order to break the seal at the joints, before swinging open normally. These hinges are commonly used on entrance doors t o prestigious build- ings to overcome the problem of pressure dif- ference across the doors in winter. What is needed is a more economical version of the same hinge for stair doors in high buildings.
The performance of a vestibule pressuriza- tion system in a 17-storey hotel [16] in
*The door t o the fire floor is likely to be open during the fire fighting; in addition, the door to the outside at grade is required t o be held open by the conditions for a pressurized stair shaft in the National Building Code.
Ottawa was measured after the building was completed and found t o be effective. Objec- tions t o this system are the loss of rentable space and an increase in the number of doors required. For a very high building there might also be a problem of excessive pressure across doors if pressure modulation or special hinges are not used.
Designing a fully pressurized system [17] is not appropriate for a building where the floor area or the enclosure of the perimeter is not the same for all floors. I t is thus not suitable for tall buildings erected on a large podium or linked t o an extensive shopping mall. In this system, pressures need t o be modulated according to variations in outdoor tempera- tures. Tamura has recently suggested a design approach based on a fully sprinklered building
[18], having a smoke shaft with mechanical exhaust, assuming that the sprinklers will both prevent windows from breaking and limit the temperature of the gases in the smoke shaft.
The Division of Building Research last year opened a new facility designed to study smoke movement in high buildings and conduct full-scale fire experiments at the Fire Research Field Station, situated in the country 60 km west of Ottawa. Included in this facility is a 10-storey tower building with stair, elevator, service and smoke shafts nor- mally found in the building core, and a minimal floor area of about 37 mZ on each floor where controlled experimental fires can take place. There is also a work and viewing area on each floor, separated from the experi- mental area by a fire-resistant wall with viewing ports. The work of installing gas burners t o simulate a fire on the second storey and instrumenting the tower t o measure temperature and pressure and sample gases should be completed sometime this year. There is also a burn hall with an open floor 1670 m2 in area and 1 2 m in clear height under a fire-resistant ceiling. At one end the floor has been reinforced and provided with anchorage for full-scale fire experiments on building structures.
In the service unit are workshops, office space, and equipment for gas analysis, data acquisition and computation. This facility is said t o be the most sophisticated structure that exists for studying smoke movement in high buildings.
CONCLUSION
The National Building Code smoke control requirements, in existence now for nearly 1 0 years, are somewhat older than the first build- ings t o comply with them, due t o the time lag in enforcing provisions. There appears t o be a trend toward using sprinklers and pressurized stair shafts in apartment buildings.
In cold-climate countries such as Canada, stack effect is an important factor in the movement of smoke through high buildings.
Thus fire on a lower floor presents more
problems than one on an upper floor.
The Division of Building Research now has a tower t o study under real conditions the problems presented by fire in high buildings. The facilities of the Fire Research Field Station can be made available as circum- stances permit t o both public and private organizations in Canada.
REFERENCES
1 G. T. Tamura and A. G. Wilson, Pressure differ- ences caused by chimney effect in three high buildings and building pressures caused by chim- ney action and mechanical ventilation, ASHRAE Trans., 73 (11) (1967) 1 - 8.
2 G. T. Tamura, Computer analysis of smoke move- ment in tall buildings, ASHRAE Trans., 75 (11) (1969) 8 1
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9 2 .3 N. B. Hutcheon and G. W. Shorter, Smoke prob- lems in high-rise buildings, ASHRAE J., 10 ( 9 )
(Sept.) (1968) 57
-
61.4 J. H. McGuire, Smoke movement in buildings,
Fire Technol., 3 ( 3 ) (Aug.) (1967) 1 6 3
-
174. 5 J. H. McGuire, Control of smoke in buildings,Fire Technol., 3 ( 4 ) (Nov.) (1967) 281
-
290. 6 M. Galbreath, Fire in High Buildings, DBR FireStudy N o . 21, Nat. Res. Council Canada, April,
1968.
7 M . Galbreath, Time of evacuation by stairs in high buildings, Fire Fighting in Canada, February,
1969, Parkins Publ. Co., Montreal.
8 Design and Construction of Building Exits, Misc. Publ. M151, National Bureau of Standards, U.S.
Department of Commerce, Washington, DC, October, 1935.
9 J. L. Pauls, Movement of people in building evac- uation, Human Response t o Tall Buildings, Ch.
21, Community Developments Series, Vol, 34, Dowden, Hutchinson and Ross, Stroudsburg, PA, 1977, pp. 281
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292.1 0 Explanatory Paper o n Control o f Smoke Moue- ment in High Buildings, National Research
Council Associate Committee on the National Building Code, June 1970.
11 Measures for Fire Safety in High Buildings, Na- tional Research Council Associate Committee o n the National Building Code, 1973.
1 2 D. M. Baird, chateau Champlain fire, Fire J., 62 ( 3 ) (M a y ) ( 1 9 6 8 ) 15
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19.13 Rolf Jensen and Associates Ltd., Survey o f S m o k e Control Systems Installed in High-Rise Buildings in Metropolitan Toronto during 1976 t o
1980, Don Mills, Ontario, August, 1981. 1 4 Survey o f Smoke Control Systems Installed in
High-Rise Buildings in the City o f Calgary since
1976, ACPH Engineering and Construction Ltd., Calgary, Alberta, March, 1982.
15 G. T . Tamura, Experimental studies o n pressur- ized escape routes, A S H R A E Trans., 80 (11) ( 1 9 7 4 ) 224
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237.16 G. T . Tamura, T h e performance o f a vestibule pressurization system for t h e protection o f escape routes o f a 17-storey hotel, A S H R A E Trans., 86 ( I ) ( 1 9 8 0 ) 593
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603.17 G. T . Tamura and C . Y . Shaw, Field checks o n building pressurization for smoke control in high rise buildings, A S H R A E J., 23 ( 2 ) (Feb.) ( 1 9 8 1 ) 21
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25.18 G. T . Tamura, A smoke control system for high- rise o f f i c e buildings, A S H R A E J., 24 ( 5 ) ( M a y ) ( 1 9 8 2 ) 29
