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Title: Safety Strategies for Supertall Buildings in Hong Kong

Authors: Wan-ki Chow, Chair of Architectural Science & Fire Engineering, The Hong Kong Polytechnic University Nai-kong Fong, Associate Professor, The Hong Kong Polytechnic University Che-heng Liu, Associate Professor, The Hong Kong Polytechnic University Tam Tai-keung, Divisional Commander, Hong Kong Fire Services Department Yue Tsz-kit, Senior Station Officer, Hong Kong Fire Services Department

Subject: Fire & Safety

Keywords: Building Code Density Evacuation Fire Safety Refuge Areas Supertall

Publication Date: 2013

Original Publication: CTBUH Journal, 2013 Issue I

Paper Type: 1. Book chapter/Part chapter 2. Journal paper 3. Conference proceeding 4. Unpublished conference paper 5. Magazine article 6. Unpublished

© Council on Tall Buildings and Urban Habitat / Wan-ki Chow; Nai-kong Fong; Che-heng Liu; Tam Tai- keung; Yue Tsz-kit Research: Fire and Safety Fire Safety Strategies for Supertall Buildings in Hong Kong In the course of updating fire safety standards in Hong Kong, an array of fire Authors Chow Wan-ki, Chair of Architectural Science & Fire safety issues in supertall buildings were found, raising concerns about the Engineering effectiveness of existing codes. By reviewing fire safety strategies adopted in Fong Nai-kong, Associate Professor Lui Che-heng, Assistant Professor Hong Kong, this article illustrates how these concerns can be addressed Department of Building Services Engineering globally and specific areas that require further study. The Hong Kong Polytechnic University Hung Hom, Kowloon, Hong Kong, China t: +852 2766 5843; +852 2766 5854; +852 2766 7959 e: [email protected]; nai-kong.fong@polyu. Introduction et al. 2001) or supertall buildings (Chow & edu.hk; [email protected] Chow 2009 , 2010) and the Hong Kong Fire

Tam Tai-keung, Divisional Commander Hong Kong is densely populated with more Safety Code requires a refuge floor to be than seven million people living in an area of constructed in buildings above this height. Hong Kong Fire Services Department Divisional Headquarters (East/New Territories) 1,108 square kilometers. The vast majority of The China Fire Code imposes a similar 26 Yuen Wo Road, New Territories, Hong Kong, China people are settled in a small residential zone requirement and defines supertall buildings t: +852 2603 1420 e: [email protected] of about 76 square kilometers and an even as building exceeding 100 meters. smaller commercial area of about 4 square Yue Tsz-kit, Senior Station Officer kilometers. However, studies have shown no significant Hong Kong Fire Services Department increase in fire risk in buildings at or above 40 10/F, Fire Services Headquarters Building 1 Hong Chong Road, Kowloon, Hong Kong, China The increasing number of supertall buildings stories. Very few big high-rise building t: +852 2733 7667 in Hong Kong CBD (see Figure 1) has have been recorded, though the fire load e: [email protected] intensified concerns over fire safety. However, density was surveyed to be very high (Arup additional fire safety requirements in supertall 2010). Therefore, it is suggested that other Chow Wan-ki is the Chair Professor of Architectural Science & Fire Engineering, and also the Director of buildings often become a competing factors, such as wind, culture, fire department Research Centre for Fire Engineering at The Hong objective to innovative architectural designs. capability, and law enforcement strength, Kong Polytechnic University. He has also served as the Head of the Department of Building Services En- These requirements can raise construction should also be considered in determining the gineering. He is the Founding President of the Society costs for some new projects; most minimum fire safety provisions of supertall of Fire Protection Engineers – Hong Kong Chapter. importantly, they might not guarantee buildings, in addition to height. Dr. Fong is an associate professor of the Department of Building Services Engineering of the Hong Kong substantial and quantifiable enhancement in Polytechnic University. He obtained his BSc degree in fire safety for future supertall buildings. There The Guideline for Very Tall Buildings (SFPE Applied Mathematics and Computing in 1986 and his PhD degree in Fire Engineering in 1991. is little research available on fire safety 2012) and the China Fire Code state that a Dr. Lui is an assistant professor in the Department provisions for supertall buildings, which multiplication factor should be used to of Building Services Engineering of the Hong Kong makes it difficult to develop effective estimate the Required Safe Egress Time (RSET Polytechnic University. She graduated from the same university with a Bachelor of Engineering (Hons) standards. Therefore, a performance-based – the time required to escape to a safe place) degree in Building Services Engineering in 1995 and a approach is suggested for future supertall of supertall buildings as occupants may PhD degree in 2001. building projects in Hong Kong to identify fire require more time to escape. Also, firefighting Tam Tai-keung is currently working as the Divisional Commander of East/New Territories. He had been safety concerns and formulate fire safety lifts are required by the China Fire Code and the officer-in-charge of the New Projects Division of strategies. the Hong Kong Fire Safety Code for buildings the Fire Safety Command for years in which he was responsible for formulating fire safety requirements exceeding 24 meters and 30 meters in respect of all new buildings and alteration works respectively. These provisions show that to existing buildings. During his tour of service in the Fire Services Department, he has taken charge of a High-rise and Supertall Buildings effective vertical transportation is necessary number of major incidents like high-rise building fires for firefighting in high-rise buildings of at least and landslides. He was also the leader of the HKSAR Rescue Team for the 512 Sichuan Earthquake Incident There is no consensus on the definition of tall 40 stories, not to mention buildings of 300 in May 2008. and supertall buildings among international meters or above. Yue Tsz-kit obtained his degree of BSc in Surveying fire safety standards, including Hong Kong’s in 2005, and MSc in Fire and Safety Engineering in local regulations. For example, the Hong Kong Although no significant increase in fire risk 2012. He has been working in the Fire Services De- partment since 2006. Mr. Yue is now responsible for Fire Service Installations Code describes could be shown in buildings at or above 40 vetting building plans and fire engineering reports high-rise to be buildings that exceeds 30 stories, there is a question mark on whether related to performance-based designs from both public and private sectors. In addition, he is an active meters. In the global context, 23 meters and existing fire safety provisions are effective in researcher interested in new fire safety requirements 18 meters are adopted in NFPA 5000 and BS coping with elevated fire risks in supertall for novel and complex developments. 9999: 2008, respectively. Buildings with more buildings with heights exceeding 300 meters. than 40 stories have been classified as ultra high-rise buildings (Lo 1997; Lo et al. 2002; Lu

26 | Fire and Safety CTBUH Journal | 2013 Issue I International Commerce Centre Two International Cheung Kong (484 m) Finance Centre Centre (283 m) (412 m) According to the Central Plaza The Center Bank of China (374 m) (346 m) Tower (367 m) “Hong Kong Fire Safety Code, refuge floors are mandatory for non- industrial buildings higher than 25 stories,

Figure 1. Scenic view of Hong Kong CBD from the Peak. © Yuliantina Widjaja industrial buildings

Fire Safety Concerns in Hong Kong office, podium, and basement. When a higher than 20 stories, detector is activated, only alarms on the fire Fire safety requirements for supertall buildings floor, one floor below and two floors above and residential in Hong Kong follow either a prescriptive the fire floor will be actuated. Alert messages buildings exceeding 40 approach or a performance-based approach. will be broadcast on non-affected floors in the Differences between the two approaches can same zone and other unaffected zones stories. be illustrated by the fire detection and alarm (Whittall 2012). Fire alarms in other zones will systems of two supertall buildings. In Supertall not be actuated unless total evacuation is ” Building A (412 meters, completed in 2003), required (see Figure 3). Despite the differences Staircase reliability the fire detection system is divided by four between alarm zoning and actuation scope, In high-rise buildings around the world, refuge floors to form five zones. Fire alarms both approaches were accepted by the local evacuees may flee through protected will sound in the whole building if any fire authority. staircases, external windows, or via adjacent detectors in any one zone is actuated (see buildings in some cases. However, evacuees in Figure 2). supertall buildings in Hong Kong can only rely Evacuation on staircases, since only staircases are On the other hand, the fire detection system accepted by the Hong Kong Authority as a of Supertall Building B (484 meters, completed Different approaches and standards are used means of escape. Therefore, the reliability of in 2010) is divided into four zones: hotel, in evaluating evacuation systems: staircases is paramount in ensuring the safety of occupants. Nevertheless, prescriptive staircases do not always guarantee effective Hotel evacuation.

The concept of refuge areas/floors Sub-Panel 4 The concept of refuge floors was introduced Indication only to Hong Kong in 1996. According to the Hong

Sub-Panel 3 Kong Fire Safety Code, refuge floors are Indication only Office mandatory for non-industrial buildings higher Refuge Floor than 25 stories, industrial buildings higher than 20 stories, and residential buildings Sub-Panel 2 exceeding 40 stories. By using an intermediate Indication only refuge floor within a certain number of floors, occupants could reach a temporary place of safety within 10 floors. On the other hand, Sub-Panel 1 Indication only many international fire codes stipulate the Tower automatic Podium requirement of an area of refuge (about 1.5 x fire alarm (AFA) Direct telephone main control panel Basement 1.5 meter located at the protected staircase) line (DTL) to FSD (G/F Fire Service ) for the temporary safety of people with Figure 2. Schematic diagram of the design of the fire Figure 3. The zoning arrangement of the fire detection disabilities. However, caution has to be paid if detection system of Supertall Building A. © Authors system in Supertall Building B. © Authors

CTBUH Journal | 2013 Issue I Fire and Safety | 27 an area of refuge is used in calculating total As the reliability of fire detection and alarm evacuation time (TET) or RSET. Evacuees may Hotel systems is crucial to the effectiveness of such Alert Zone be reluctant to wait for rescue on a refuge an approach, the Hong Kong Fire Services floor after the collapse of the World Trade Department (FSD) has issued a circular letter Center on September 11, 2001. specifying measures to be carried out in case of shutdown or repair of detection and alarm In the Hong Kong Fire Safety Code at least systems, such as the provision of standalone 50% of the gross floor area on a refuge floor smoke detectors in buildings adopting shall be designated as a place of refuge. Office Evacuation Zone performance-based design. Additional However, if the factor of 4.5 m2/ firefighting staff and equipment are also person for a typical residential development is deployed and more frequent patrolling adopted, the occupancy factor of the refuge intervals are imposed. floors would be 0.22 2m /person. If a greater occupancy factor, such as 1 m2/person in restaurants and 0.5 m2/person in a banking Fire Suppression Podium hall as stated in the code is considered, there Alert Zone would be too many evacuees on the refuge Basement The provision of fire suppression systems in floor. Therefore, the prescriptive refuge area supertall buildings requires additional calculation in supertall building should be Figure 4. An illustration showing phased evacuation on attention in Hong Kong. Suppression systems office floors of Supertall Building B. © Authors further studied. might have unintended consequences all MoE in supertall buildings are free from unique to supertalls. For example, sprinkler Counter flow problem obstruction and combustibles. In addition, water might cool down hot smoke while Clashing between emergency responders change in use and structural alterations of stack effect might cause smoke logging. and evacuees may increase the time for buildings have to be approved by the Therefore, the suppression philosophy in rescue and evacuation (SFPE 2012). For this building authority in advance because it may supertall building has to be revisited. reason, a “hydraulic flow” approach (Chow lead to increases in occupant load, travel 2006) may not be applicable in estimating the distance, and fire load. Also, the use of fixed fire pumps for the fire evacuation time of occupants with different hydrant/hose reel (FH/HR) system to replace physical strengths (Kady & Davis 2009). To intermediate booster pumps may lower the ensure safe evacuation, clashing has to be Fire Detection and Alarm reliability of the FH/HR system in supertall incorporated in the calculations. Indeed, the buildings. If both of the FH/HR pumps fail, NFPA 5000 has pointed out this deficiency. It is understood that if a fire is detected early, firefighters have to manually lift heavy What’s more, the China Fire Code incorporates the RSET would be decreased. The increased portable pumps to deliver firefighting water. clashing in the calculation of evacuation time margin of safety is based on the assumption that occupants were safe when all of them For this reason, the Hong Kong FSD imposed Lift evacuation entered the protected staircase. However, the specific measures to maintain the suppression Apart from traditional means of evacuation shaft configurations of supertall buildings strength in supertall buildings. First, fast via , lift evacuation could be an effective pose a challenge. More evacuees would be response sprinkler heads are installed in alternative. There are standards on evacuation queuing to enter the escape routes in a special hazard areas. Also, owners of fire using lifts. However, more research on supertall than in conventional buildings. To service installations (FSIs) are obliged to validating the reliability and effectiveness of maintain the same level of RSET and the employ a registered FSI contractor to inspect lift evacuation has to be conducted, safety margin, detection time in supertall the FSIs of their buildings at least once every particularly in supertall buildings, in order to buildings has to be shortened with better 12 months. Moreover, periodic maintenance be accepted by the Hong Kong authority. alarm zoning. and functional tests during joint exercise/drills are conducted between the building Law enforcement in evacuations In addition, it is suggested that evacuating management and FSD personnel. Effective evacuation relies on unobstructed some floors above and below the fire floor by means of escape (MoE) with adequate width means of a zoned detection and alarm system and an ordered evacuation. Although the may alleviate congestion in the MoE Fire Service Intervention width of MoE in supertall buildings is (Bukowski 2010). This approach has been regulated by the Hong Kong Fire Safety Code, adopted in some supertall buildings such as Fire service intervention can be discussed in the authority, owners, and/or facility the Supertall Building B in Hong Kong (see terms of means of access (MoA) and active managers of supertall buildings should ensure Figure 4). suppression by firefighters.

28 | Fire and Safety CTBUH Journal | 2013 Issue I Supertall buildings have extremely high Table 1 lists the fire service installations (FSIs) supertall buildings in Hong Kong and should façades which are out of reach of aerial requirements for high-rise commercial and be pressurized to 50 Pa. However, the pressure ladders. Therefore, additional fire safety domestic buildings. Currently there are no difference between ground floor and the roof requirements are imposed by worldwide additional FSI requirements for supertall due to the stack effect in supertall buildings building codes. For example, NFPA 5000 and buildings with height exceeding 300 meters. may be up to 1 kPa. Therefore, using CFD the Hong Kong Fire Safety Code require the FSIs for supertall buildings are the same as modeling to predict smoke movement in a distance between an emergency vehicular high-rise buildings. However, in view of the vertical shaft should be cautious (Zhang et al. access (EVA) and fire service access point possible differences between normal tall 2006; Zhao & Chow 2009). should not be longer than 10 meters and 18 buildings and supertall buildings in vertical meters respectively. Apart from the distance, transportation strategy of firefighters and The Buildings Department of Hong Kong has the width of EVA for new buildings should be firefighting water, extensive verifications of issued the Code of Practice on Wind Effects in no more than 4 meters and 7.3 meters as existing fire safety provisions are necessary. Hong Kong 2004 which addresses structural required by the China Fire Code and Hong stability of a building façade. Nevertheless, the Kong Fire Safety Code, respectively. However, effect of natural wind to smoke and flame the provision of a reliable rescue staircase and Smoke and Fire Spread spread is not discussed, not to mention the stairway may be even more crucial to fire effect of natural wind on a refuge floor. As service intervention, though firefighters may Buoyancy, stack effect, and ambient wind high wind speed may accelerate fire growth need some time to reach the uppermost floor have determining effects on fire growth, in supertall buildings, empirical study on of a supertall building by staircase. particularly at high level. In addition, higher natural wind effect to ventilation-controlled fire risk, the acceleration of fire and smoke fire growth and smoke spread is necessary. Fireman lifts are required in tall and supertall spread, and the aggravation of fire damage buildings for the conveyance of manpower due to characteristics of supertall buildings and equipment to the fire floor. The Hong must be investigated. Interaction between Different Risk Kong Fire Safety Code stipulates the Parameters in Supertall Buildings dimension, rated load, and speed of a The validity of smoke movement and control fireman’s lift. Nevertheless, there is no deduced by computational fluid dynamics Apart from physical fire safety requirements, additional requirement for fireman’s lift in (CFD) software is often subject to challenge, fire safety management also plays an supertall buildings despite more manpower since they are predicted by numerical important role in supertall buildings. and equipment. approximation. Even if the software could be Occupancy arrangement, fire load density, well verified, considering all fire dynamics in and their interactions can help determine the supertall buildings (e.g., stack effect, external level of fire risk. wind loading, and fire Commercial Domestic Fire Service Installations (FSIs) whirl) in a single fire Mixed-type occupancy High-rise High-rise model to generate a Due to economic development, mixed-type Audio/visual advisory system  converged result could occupancy is commonly found in supertall Automatic actuating devices  be a great challenge. buildings. For example, laboratories may be Automatic fixed installation other than water  present in commercial buildings, but visitors Emergency generator   He and Beck (1996) may not be aware of the risk. Moreover, illegal Emergency lighting   interpreted stack effect , such as the over-storage of as “the pressure dangerous goods, pose additional fire risk to Exit sign   difference that can be supertall buildings. Fire alarm system   experienced between Fire control center  an enclosure and its Fire load density and heat release rate Fire detection system  surroundings if the air Prescriptive fire safety strategies in supertall Fire hydrant/hose reel system,   temperature inside the buildings may be insufficient to address high Fireman’s lift   building is different fire load in dense commercial floors and Portable hand-operated approved appliance   from that outside.” mixed type occupancies. For example, cartons Pressurization of staircase  Scholars assert that of paper stored in modern office may be stack effect may affect uncontrollable by the prescriptive-designed Sprinkler system  smoke movement. For hazard group. Also, evacuation in hotels may Static or dynamic smoke extraction, system  example, pressuriza- be longer than in offices during certain hours Ventilation/air conditioning control system  tion of staircases is due to the sleeping characteristics. Table 1. Fire service installations (FSIs) required for commercial and domestic use ac- widely adopted in cording to Hong Kong Fire Service Department (FSD).

CTBUH Journal | 2013 Issue I Fire and Safety | 29 Sprinkler controlled (High FLD) Sprinkler controlled (High FLD)

FS intervenon (High FLD) FS intervenon (High FLD)

Uncontrolled Fire (High FLD) Uncontrolled Fire (High FLD)

Sprinkler controlled (Low FLD) Sprinkler controlled (Low FLD)

FS intervenon (Low FLD) FS intervenon (Low FLD)

Uncontrolled Fire (Low Uncontrolled Fire (Low

Figure 5. Timeline analysis on stakeholders’ actions in low-rise building fires. © Authors Figure 6. Timeline analysis on stakeholders’ actions in high-rise building fires. © Authors

For this reason, Hong Kong has restricted vertical water relays mixed occupancy in building design. for firefighting is Sprinkler controlled (High FLD) Nevertheless, systematic controlling measures strenuous and time FS intervenon (High FLD) to excessive fire load and incompatible consuming. For this Uncontrolled Fire (High FLD) occupancies are still required. reason, installation of Sprinkler controlled (Low FLD) a standpipe system is FS intervenon (Low FLD) required in buildings Uncontrolled Fire (Low Evacuation of People with Disabilities under construction.

Barrier free provisions have been incorporated In Hong Kong, fire since 1997 and the revised Design Manual – safety during Barrier Free Access 2008 incorporates more construction of barrier free access provisions and accommo- supertall buildings is Figure 7. Timeline analysis on stakeholders’ actions in supertall building fires. © Authors date the growing elderly population. governed by the Fire Services Department (FSD) with reference to required in new buildings. On the other hand, Barrier free access requirements in the manual the height, layout, and configuration of the all FSIs should be inspected at least once are similar to NFPA 5000 and BS 9999:2008, building. FSD mandates a temporary every 12 months in accordance with the which is based on the presumption that 1 in commission of a fire hydrant system. Hong Kong FSI Code, but the frequency of 200 persons is disabled. Nevertheless, it is Moreover, the top most hydrant should be maintenance, inspection, and testing of reported that 142,740 people (about 2% of within 30 meters from the topmost floor. elements has not been the population) are receiving disability specified. allowance in Hong Kong. Also, not every building has a tailor-made evacuation Management and Maintenance strategy, as there is no such requirement in Analysis on Stakeholders’ Actions the manual (except hospitals and care home Effective evacuation in supertall buildings also for elderly and disabled due to licensing relies on the performance of fire service Figures 5 to 7 illustrate how fire safety requirements). Therefore, the requirements in installations (FSIs), such as sprinklers, fire concerns are approached in Hong Kong. The providing barrier free access facilities and the hydrant/hose reel, drencher systems, and three figures are drawn based on the associated evacuation strategy have to be passive fire protection elements, including assumptions that: reviewed. smoke reservoir and smoke extraction. Although these provisions are incorporated in 1. Flashover time, which is easier to determine the Deed of Mutual Covenant in Hong Kong, than time to tenability, because it can be Fire Safety during Construction there is an overriding concern about how judged by flame moving out of an opening, these requirements can be effectively is shorter when floors are higher (due to Several major fires have been reported in the implemented. better ventilation) and when fire load is construction of quasi-supertall buildings, such higher (due to more burning surfaces). as the Beijing CCTV Headquarters in 2009 and Similar to NFPA 5000 and BS 9999:2008, the Anemometric data compiled by the Hong a residential complex in Hong Kong in 2005. Hong Kong Fire Safety Code stipulated the Kong Observatory (HKO 2013) found Water supply was found to be critical since extent of passive fire protection elements stronger winds in higher altitude. Taking

30 | Fire and Safety CTBUH Journal | 2013 Issue I into account two fire compartments with to be considered in order to minimize the CHOW, C. L. & CHOW, W. K. 2009. “Fire Safety Aspects of same size, layout, area of opening, and RSET. Moreover, protected staircases or refuge Refuge Floors in Supertall Buildings with Computational Fluid Dynamics.” Journal of Civil Engineering and building material, stronger wind is more floors may serve as the end of the phased Management 15 (3): 225–236. likely to speed flashover; evacuation. 2. Ventilation rate is the same and is not a CHOW, C. L. & CHOW, W. K. 2010. “Heat Release Rate of Accidental Fire in a Supertall Building Residential Flat.” limiting factor to fire size until flashover; To address shorter flashover time in supertall Building and Environment 45 (7): 1632–1640. 3. Fire service response times are constant so buildings, early detection and suppression are the operation time of fire hydrant is the essential. Figures 5 to 7 assist fire safety CHOW, W. K. 2004. “Evacuation in a Supertall Residential Complex.” Journal of Applied Fire Science 13 (4): 291–300. same in the three figures. professionals to identify potential risks and formulate strategic solutions. However, the fire CHOW, W. K. 2006. “A Retrospective Survey on Elevator In low-rise buildings and low level atria, scenario and duration of stakeholders’ activity Evacuation of Supertall Buildings under Fires.” Journal of Applied Fire Science 16 (4): 315–327. natural ventilation is usually weaker (HKO may vary according to particular situations 2013) and restricts the development of fire. and coordination of stakeholders. CHOW, W. K. & HAN, S. S. 2009. “Experimental Investigation Therefore, firefighters may arrive well before on Onsetting Internal Fire Whirls in a Vertical Shaft.” Journal of Fire Sciences 27 (6): 529–543. flashover and prevent it from occurring. However, many unburnt fire gases and toxic Conclusion CHOW, W. K. & LAM, C. 2006. “Evacuation Studies for Tall smoke are generated in the long smothering Office Buildings in Hong Kong.” Journal of Applied Fire Science 15 (3): 169–181. stage, which may become untenable even Current research questions whether existing without flashover. codes for high-rise buildings are sufficient to HK FIRE SERVICES DEPARTMENT. 2008. “Shutdown of Fire cope with the unique characteristics of Service Installation for Inspection, Maintenance, Modification or Repair.” FSD Circular Letter No. 3/2008. In high-rise buildings, stronger winds at supertall buildings. Also, occupants in higher levels speed up the increase in heat supertall buildings may find it difficult to HE, Y. & BECK, V. 1996. “Estimation of Neutral Plane Position flux and the generation of unburnt gases. As evacuate in the same manner as in shorter in High-rise Building.” Journal of Fire Sciences 14 (3): 235–248. the increases speed up, the available safe high-rise buildings. All these suggest that a egress time (ASET) will be shortened and new fire safety standard for supertall buildings HONG KONG OBSERVATORY. 2013. “Regional Climate of flashover will occur earlier. Also, flashover may is required. Despite the fact that Hong Kong, a Hong Kong.” http://www.weather.gov.hk/cis/regione.htm. occur at the time when firefighters arrive. On city on the cutting edge of supertall building KADY, R. & DAVIS, J. 2009. “The Impact of Exit Route Designs the other hand, due to dense population and construction, has imposed additional fire on Evacuation Time for Crawling Occupants.” Journal of Fire high fire load density in Hong Kong, the safety safety provisions for supertall buildings, a Sciences 27 (5): 481–493. margin is usually tight. A small reduction (e.g., comprehensive standard is necessary. LO, S. M. 1997. “The Use of Designated Refuge Floors in 10%) of ASET might already make the ASET High-rise Buildings: Hong Kong Perspective.” Journal of shorter than the RSET. Nevertheless, This study highlights several fire safety Applied Fire Sciences 7 (3): 329–356. competent property management staff could concerns in supertall buildings that are worth LO, S. M.; CHEN, D.; YUEN, K. K. & LU, W. 2002. “A Numerical react more swiftly in a high-rise building fire. investigation. Further studies on improving Study of External Smoke Spread in Designated Refuge Therefore, the RSET in high-rise buildings are the existing situation are suggested.  Floor.” Building and Environment 37 (3): 257–268. also reduced and safety margins are not LU, W. Z.; LO, S. M.; FANG, Z. & YUEN, K. K. 2001. “A Preliminary compromised. Investigation of Airflow Field in Designated Refuge Floor.” Acknowledgment Building and Environment 36 (2): 219–230. This project is supported by the Fire Services Department In supertall buildings, ventilation due to ultra (FSD) of the Hong Kong Special Administrative Region MALOTT, D. 2010. “Hong Kong International Commerce strong wind at supertall level is likely to affect Government and the Research Center for Fire Engineering, Center.” CTBUH Journal 2010 Issue IV: 12–17. fire development. It may be argued that Department of Building Services Engineering, The Hong Kong Polytechnic University (PolyU), Hong Kong, China, SOCIETY OF FIRE PROTECTION ENGINEERS. 2012. sprinklers, which are mandatory to all under the PolyU/FSD Mentorship Programme supervised “Guidelines for Designing Fire Safety in very Tall Buildings commercial buildings in Hong Kong by the leading author, Professor W.K. Chow. The authors – Draft for Consultation.” Bethesda: SFPE regardless of height, may greatly reduce the wish to thank Mr. Chan Chor-kam Andy, Director of Fire Services, for his generous support and technical advice. WHITTALL, S. 2012. “ASD: Relative or Fixed Sensitivity.” Asia chance of flashover. However, an illegal Pacific Fire Magazine 41: 17–21. closure of a sprinkler system’s subsidiary valve resulted in firefighter deaths in a big fire in References ZHANG, J. Y.; JI, J.; HUO, R.; YUAN, H. Y. & YANG, R. 2006. “A ARUP. 2010. Research in East Asia. Hong Kong: Arup. Comparison of Simulation and Experiment on Stack Effect 2007 and so sprinklers cannot be regarded as in Long Vertical Shaft.” Journal of Fire Sciences 24 (2): fail-safe. To maintain the safety margin in BUKOWSKI, R. 2010. “International Applications of Elevators 121–135. supertall building, RSET has to be reduced for Fire Service Access and Occupant Egress in Fires.” CTBUH Journal 2010 Issue III: 28–33. ZHAO, J. & CHOW, W. 200. “Experimental and Numerical dramatically. Nevertheless, total evacuation in Studies on Stack Effect in a Vertical Shaft.” Journal of Applied supertall buildings may take hours to CHENG, C. K.; LAM, K. M.; YUEN, K. K.; LO, S. M. & LIANG, J. Fire Science 19 (4): 369–400. complete. Therefore, phased evacuation has 2007. “A Study of Natural Ventilation in a Refuge Floor.” Building and Environment 42 (9): 3322–3332.

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