Heat Release Rate of an Open Kitchen Fire of Small Residential Units in Tall Buildings

Many small units of area less than 30 m2 in residential buildings over 200 m tall are equipped with open kitchens in Asia, including Hong Kong. Fire safety provisions of these kitchens are determined by performance-based design (PBD). In most PBD projects, only the spread of smoke from the kitchen on fire to the outside was commonly studied. However, a fire load survey in Hong Kong indicated large quantities of combustibles are stored in residential units. Cooking oil was found to be ignited easily even when using induction cookers. The burning of all combustibles in a big post-flashover fire needs to be studied. Data of heat release rate for local combustible products is not yet available. Estimations are based on very crude assumptions of low radiative heat flux in most of the PBD projects, and they are not supported by full-scale burning tests. Three conditions are therefore imposed by the authorities in the design approval. Firstly, gas cookers cannot be used; only flameless electric induction cookers are allowed. Secondly, additional fire suppression systems, including water mist or dry powder systems, are specified for installation. The systems are supposed to act on the stove fire and prevent its growth. The residential unit owner cannot remove the system, nor change the cooking stove without approval from the government. Thirdly, the estate management office has to sign an undertaking to implement the fire safety management procedures specified in the PBD report. However, the fire behaviour of open kitchen in small units of tall buildings is not studied in detail. No comparison has been made between scenarios with and without fire resisting enclosures. Fire dynamics is not well understood in open kitchen fires inside a small unit. Full-scale burning tests are not carried out to support fire hazard assessment. Only the spread of smoke from the kitchen fire to areas outside the unit is commonly studied to calculate the Available Safe Egress Time (ASET) and Required Safe Egress Time (RSET) in the timeline approach. Also, kitchen fires with and without fire resisting walls are not compared. The spread of smoke from the open kitchen to areas outside the residential unit was predicted by fire models. In this paper, the first important parameter on fire hazard assessment, heat release rate for an open kitchen fire will be discussed. The important issues in the estimation of heat release rate will be addressed and discussed. Example calculation of achieving low values of heat release rate will also be illustrated by the principle of superposition. Authority is recommended to review such approach

Fire Safety Technology Related to Building Design and Construction

Fire safety technology related to building design and construction will be discussed in this paper. Four areas on possible fire hazards and fire safety provisions; performance-based design; flawed concept of timeline analysis; water suppression system in atrium including sprinkler and its alternatives with water gun and sidewall long-throw sprinklers are reported. The proposed annual inspection scheme on the design criteria in fire safety design to ensure assumptions made in the fire safety assessment by the Hong Kong Fire Services Department should serve as an example of good practice

Fire Safety Technology Related to Building Design and Construction

Fire safety technology related to building design and construction will be discussed in this paper. Four areas on possible fire hazards and fire safety provisions; performance-based design; flawed concept of timeline analysis; water suppression system in atrium including sprinkler and its alternatives with water gun and sidewall long-throw sprinklers are reported. The proposed annual inspection scheme on the design criteria in fire safety design to ensure assumptions made in the fire safety assessment by the Hong Kong Fire Services Department should serve as an example of good practice

Fire Hazards of Refrigerants in Air Conditioning Control System

Air conditioning control systems are commonly installed in restaurants, commercial buildings, office buildings and institutional buildings in Hong Kong. The systems invariably involve the use of fans for moving the air, filters for cleansing, ducts for air distribution, a control system for regulating the amount of heating or cooling automatically and a refrigerating plant connected to the heat exchange surface. The ducts in turn present the possibility of spreading fire and smoke throughout the building or areas served. According to the local Code of Practice for Minimum Fire Service Installations and Equipment [1], when a ventilation or air conditioning control system to a building is provided, it shall stop mechanically induced air movement within a designated fire compartment. In order to fulfil such requirement, the architects and building services engineers will design to install associated equipment of air conditioning control systems to satisfy the relevant fire safety requirements of the local authority, which includes the provision of fire resisting ducting, fire dampers, smoke detectors and fire resisting cables, etc. However, lessons learned from past experience reveal that owners or property management staff of the buildings or covered areas and maintenance contractors will mainly concern the efficiency and energy saving of the systems without paying much attention to the fire hazards arising from the use of refrigerants. It is also noted that fire or explosion incidents [2] involving air conditioning control systems are often attributed to improper maintenance work conducted by maintenance contractors, such as refilling the refrigerating plant with poor quality refrigerants, recharging refrigerants incompatible with the metal parts of the system, refilling refrigerants at high pressure resulting in bursting of piping and joints, valves contaminated by grease, presence of an ignition source in close proximity of the refrigerating plant, etc. In general, refrigerants present two basic hazards [3], namely toxicity and flammability. Refrigerants mix readily with air and if flammable, may reach flammable concentrations ready to be ignited by an ignition source. As diffusion may not take place rapidly enough to avoid the hazards in the event of leakage, fire or explosion may occur. With reference to a recent fire with explosion incident involving air conditioning control system in a restaurant in Hong Kong, this paper will outline and discuss the fire hazards of refrigerants in air conditioning control systems

A Study on the Fire Safety Issues for Large Window Openings in Supertall Residential Buildings in Hong Kong

The trend in building supertall residential buildings with large glass pane and window openings has becoming a modern building design. It is well understood that with this design, better views and borrowing more light from the outside environmental are well known and accepted by people living in metropolitan city like Hong Kong. However, there is no report specifically on the fire safety issues related to this kind of building feature. The study aims to look for the trend and associate fire risks for large window pane and opening area and the gross floor area of each unit on the floor as well as the relationship between these two design features. These specific features will be studied separately using statistical method to ascertain the general trend in the latest building designs. In this study, the floor layouts of thirty-one supertall residential blocks from the same number of building developments will be studied. The study involves a building survey to take measurement from approved building plans on one typical floor of each block. Two sets of data, one on the total window and glass pane areas of each unit and the other on the gross floor area of the same unit will be taken. All the units on the floor will be taken into consideration. In general, larger area of the window pane will mean wider the window pane since the floor height is fixed. It is understood that the height of the window pane will not exceed the height of the floor. In the case of Hong Kong the clear height of each floor is around 2.8 meters. It has been reported that wider the window, the closer against the wall will be the flame to rise in fire situation causing fire spreading to the immediate floor/s above. The trajectory of the flame from fire below normally requires the breakage or falling-out of window pane of the affected floor and the floor/s above; as such a report on the performance of glass under the effect of fire will also be included in this study. Finally, a fire safety studies on the heat release rate in a fire compartment with references to the window openings and the floor areas will also be conducted by adopting the derived results from sophisticated studies on flashover fire in compartments. Co-relation of the results will be discussed and analyzed

Evacuation Hazards in Crowded Subway Stations

Underground subway system is the key transportation means in dense urban areas such as Hong Kong. Subway stations are crowded with passengers on the platforms and they are observed to squeeze into the train carriages during rush hours. Putting in platform screen doors made the situation even worse. As reported in the local news, subway management claims that after following the change in maximum capacity from six passengers per meter square to four passengers per meter square, the capacity is only 70% full at rush hours. However, the capacity can be over 90% of full loading under the new calculation. Subway stations become more crowded with an average weekday patronage of nearly 5.3 million passengers.  Subway stations are mostly located in the basement or ground levels connecting the shopping mall, commercial or residential building in downtown areas. The occupancy density of passengers can be much higher than expected during festivals with fireworks show and during large-scale movements such as Occupy Central. Therefore, evacuation time in emergency situation will be prolonged. To have a better understanding of the safety issue in subway stations, evacuation time in emergency situations will be studied in this paper.  Two subway stations, Station A and Station B are selected in this paper to study the evacuation hazard of crowded stations when a fire occurs. Station A is an interchange station between two railway lines, being one of the most crowded stations with high occupancy density. Station B is the first station in the local rail network to feature a special design - “Lift-only Entrancesâ€. This is a deep underground station which lies under 70 m of ground level, the passengers have to be evacuated by lift. The occupancy density in Station B is relatively much lower than Station A under normal conditions at the moment, though the station can be very crowded if there are train delays due to signal failure or other reasons.  In this paper, the evacuation effectiveness of Station A and Station B are estimated in terms of evacuation time in different scenarios by using Hydraulic Model Calculation. Moreover, the special evacuation feature of “Lift-only Entrances†in Station B and the fire safety management strategies for emergency evacuation will be discussed.  Three scenarios will be studied in each station:  Scenario A: Assume that the passengers are evenly distributed in different exits in emergency situation. All the possible factors such as passenger behaviors and conditions are eliminated.  Scenario B: Passengers have a higher tendency to evacuate at the larger exit, this is one of the passenger behaviors in emergency situation. Therefore, the passenger distribution which depends on the exit width will be studied.  Scenario C: Assume that some of the exit routes are blocked.  The most important factor for the above study is the passenger behaviors. As in scenario B, passenger behaviors would affect the evacuation time. Therefore, fire safety management is identified to be a key part in keeping efficient evacuation. For example, a good fire action plan on crowd control is needed

Experimental Fire Studies on Load Bearing Steel Structures with Common Protective Coatings Used in China

Steel structures take the advantages of good stability, good ductility, low construction cost, fast construction and hence high flexibility in shape with high utilization rate. With the rapid economic growth, steel structures are popularly used in modern architecture, particularly in supertall buildings of height over 300 m in China. However, the fire behaviour of steel structures should be watched because the mechanical strength of steel reduces when temperature increases. In this paper, fire protective coatings commonly used in China for steel structures were studied by full-scale fire tests. Three types of ultra-thin, one type of thin and one type of thick coatings were evaluated. Test samples were prepared by applying the coatings on the typical H-type steel load bearing beams following standard fire resistance test. Different sets of fire protective coatings were applied on the surface of the sample as in the actual construction process. The coating thickness for the steel structural members met the Chinese regulation with ultra-thin fire protective coating of 2.00 mm ± 0.02 mm, thin fire protective coating of 5.0 mm ± 0.5 mm and thick fire protective coating of 25 mm ± 2 mm. Experiments were carried out in the large-scale testing facilities at Sichuan Fire Research Institute, Dujiangyan, Sichuan, China. The transient temperatures at different positions inside and outside the steel structure, and structural distortion of the steel structural members with different fire protective coatings under the testing condition were measured. Results on the measured temperatures, middle flexibility change values and corresponding time parameters on related parts of the test samples were then studied. A mathematical model was used for analyzing the result. The associated variables and correlation expressions among different variables were studied. Results can be taken as a reference for drafting new standards on evaluating the fire protective coatings for load bearing steel structures. For example, for the fire test of ultra-thin fire protective coating, it is possible to analyze and generalize the acquired data on temperature-time curve. For the thick-type steel structure fire protective coating, when the maximum temperature of the steel structure approaches 500oC and there is a high rate of temperature change, the fire resistance period of the structural members with protective coating can be predicted

Study on flashover in small residential units with an open kitchen by nonlinear dynamics

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Flashover is a dangerous phenomenon in building fires which is characterized by a sharp increase in burning rate and gas temperature. Open kitchens have been designed for many small units in tall residential buildings in densely populated areas, sparking big concerns about fire safety because of its small confined area and high fire load density. Efforts on preventing flashover should be made. In this paper, nonlinear dynamical system was used to study flashover in an example apartment with an open kitchen. A two-layer zone model was used to simulate the apartment fire by a hot upper smoke layer and a cool lower layer. The hot smoke layer temperature was taken as a single state variable in the model. The rates of heat gain from the fire and heat loss from the smoke layer were expressed as functions of temperature. A differential equation was set up to describe the rate of change of the layer temperature based on a simple heat balance of the smoke layer. Evolution of the smoke layer temperature, equilibrium states of the system and their corresponding stabilities were then investigated. The heat release rate was taken to be one of the most important control parameters affecting the evolution of the system state. The impacts of different heat release rates on the system state were studied. Critical conditions for the onset of flashover obtained from this model were compared with data available in the literature.cf201

Proposed fire safety strategy on airport terminals

Fire safety strategy for airport terminals will be proposed in this paper. The local airport terminal is taken as an example. Special features of airport terminals will be outlined. The retail areas are identified as places with higher fire risk. Standards, codes and design guidelines used overseas are reviewed and compared with the local codes. Based on the study, fire safety strategy is suggested to have four parts: passive building construction for fire safety; active fire protection systems or fire services installation; fire safety management; control of risk factors. All four parts will be discussed in this paper. Suggestions are made to give a fire safe airport terminal.Department of Building Services Engineerin

Stability of Pharmaceutical Cocrystal During Milling: A Case Study of 1:1 Caffeine-Glutaric Acid

yesDespite the rising interest in pharmaceutical cocrystals in the past decade, there is a lack of research in the solid processing of cocrystals downstream to crystallization. Mechanical stress induced by unit operations such as milling could affect the integrity of the material. The purpose of this study is to investigate the effect of milling on pharmaceutical cocrystal and compare the performance of ball mill and jet mill, using caffeine-glutaric acid (1:1) cocrystal as the model compound. Our results show that ball milling induced polymorphic transformation from the stable Form II to the metastable Form I; whereas Form II remained intact after jet milling. Jet milling was found to be effective in reducing particle size but ball milling was unable to reduce the particle beyond certain limit even with increasing milling intensity. Heating effect during ball milling was proposed as a possible explanation for the difference in the performance of the two types of mill. The local increase in temperature beyond the polymorphic transformation temperature may lead to the conversion from stable to metastable form. At longer ball milling duration, the local temperature could exceed the melting point of Form I, leading to surface melting and subsequent recrystallization of Form I from the melt and agglomeration of the crystals. The findings in this study have broader implications on the selection of mill and interpretation of milling results for not only pharmaceutical cocrystals but pharmaceutical compounds in general