Case Studies in Fire Safety最新文献

Engineers rely on studies that publish building evacuation data from various occupancies when conducting an egress analysis; this usually includes the people’s pre-movement and movement times. However, much of the available data was collected in Western cultures, such as the U.S., which brings into question their validity to other non-Western cultures, such as Saudi Arabia. This study examines how cultural differences between the U.S. and Saudi Arabia can affect occupants’ self-reported recognition/reaction times, and the cognitive state of occupants during a fire drill. The results of this research indicate that the U.S. populations are more likely to recognize and react to a fire alarm faster than the Saudi populations during a fire drill.

The proper operation of a ventilation system plays a key role in tunnel safety. Foremost, the ventilation system needs to provide acceptable air quality for the safe passage of tunnel users. Further, it needs to provide tenable environment and to facilitate rescue conditions during a smoke or fire event. While accomplishing the first task (normal operation), i.e. providing sufficient fresh air, is relatively straightforward, dealing with the second issue is the subject of considerable debate since defining the best means to ventilate a tunnel during a fire emergency is not always clear.

Although fire tests in tunnels have been performed since the early 1960s, and although the topic of fire ventilation was raised in early national and international guidelines, relatively little interest was given to fire ventilation until several big fire events occurred in the 1990s. The tunnel ventilation systems and ventilation methodologies existing at that time proved to work well under normal operation, but failed during fire ventilation. Nowadays, the design and operation of the ventilation system during fire incidents (commonly called ‘fire ventilation’) is a major topic. While the design might follow the well-established principles, the question, ‘how to control tunnel ventilation during a fire event?’, is quite controversial. This paper discusses methods of fire ventilation with a focus on the methodologies themselves as well as on the requirements for sensors and control technologies.

Forest fires are among the most dangerous natural threats that bring calamities to a community and can turn it totally upside down. In this paper, to enable a prevention mechanism, we rely on analytics to build a novel fire danger index model that predicts the risk of a developing fire in north Lebanon. We use correlation methods such as statistical regression, Pearson, Spearman and Kendall’s Tau correlation to identify the most affecting parameters on fire ignition during the last six years in north Lebanon. The correlations of these attributes with fire occurrence are studied in order to develop the fire danger index. The strongly correlated attributes are then derived. We rely on linear regression to model the fire index as function of a reduced set of weather parameters that are easy to measure. This is critical as it facilitates the application of such prevention models in developing countries like Lebanon. The outcomes resulting from validation tests of the proposed index show high performance in the Lebanese regions. An assessment versus common widespread weather models is then made and has showed the significance the selected parameters. It is strongly believed that this index will help improve the ability of fire prevention measures in the Mediterranean basin area.

Gypsum “dehydration” phenomena, occurring when gypsum plasterboard wall assemblies are exposed to a high temperature environment, result in water vapour production and subsequent dispersion in the fire compartment; these phenomena are often neglected in relevant Computational Fluid Dynamics (CFD) simulations. Aiming to investigate the impact of gypsum dehydration in full-scale CFD simulations of lightweight drywall buildings, the FDS code is used to simulate a two-storey residential building, exposed to a typical domestic fire scenario. The building employs a structural steel frame combined with gypsum plasterboard wall assemblies. Temperature-dependent thermo-physical properties are used for all construction materials. The effects of gypsum dehydration are assessed by using two alternative modelling approaches, an effective specific heat model and a solid reaction kinetics model; the obtained predictions are compared to a benchmark test case, where no such phenomena are modelled. The obtained results demonstrate that when the highly endothermic gypsum dehydration phenomena are simulated, lower overall heat release rates, gas and wall surface temperatures are predicted. In addition, the developed solid reaction kinetics model allows, for the first time, quantitative predictions of gypsum dehydration induced water vapour production and dispersion phenomena.

Colored powders such as colored corn starch are used in events such as The Color Run to blanket the air and surroundings with decorative color. Their use, however, presents a risk of dust explosion. The fact that such powders are used at events drawing large crowds makes any fire or explosion likely to result in a mass casualty incident. For instance, the Formosa Fun Coast explosion on June 27, 2015, resulted in multiple deaths and injuries. Development of alternatives to flammable/explosive colored powders would eliminate this hazard. We demonstrate as a proof-of-concept that an ultrasonically driven water mist can produce effects similar to those created by colored powders. Food coloring was dissolved in water, and the colored water was subsequently dispersed from various ultrasonic devices and photographed. Colored clouds were formed from the colored water. Colored clouds were visible under various conditions, and color combinations were possible. Possible risks of colored corn starch and water mists are discussed. An ultrasonic misting system is capable of safely replacing colored powders with regard to appearance.

Effective fire detection systems properly installed in bus and coach toilet compartments and driver sleeping compartments may save human lives and property loss. Rapid detection allows for early evacuation and extinguishment of a small fire, while late or no detection may allow the fire to spread. The purpose of the work presented in this paper is to provide recommendations on how to install fire detection systems in toilet compartments and driver sleeping compartments. The recommendations also cover what type of detection system is most suited. As a basis for the recommendations, full scale fire tests were performed with different detection systems. The fire tests were conducted in realistic mockups of a toilet compartment and a sleeping compartment. Different heat and smoke detection systems were analyzed at different positions for different fire scenarios to provide information on how to best install detection systems in these compartments. Five different scenarios were run and the most interesting finding was that two realistic fire scenarios in the toilet compartment did not activate fire detectors in the ceiling at realistic air flow rates. It is very rare that fire detectors are placed anywhere else than on the ceiling in toilet compartments on buses and the fire would then be very large upon detection.

Design fires are often used to the evaluate performance based designs by fire protection engineers all over the world and can be an invaluable tool if used properly. One potential big issue however is the fact that the exact same design fire is recommended by authorities in similar building types despite the fact that some building characteristics, such as building material, can differ greatly. This paper focused on investigating several key characteristics of a building (building material, openings, room floor area size and ceiling height) and its effect on the design fire using computational fluid dynamics. When well to moderately insulating materials was used the design fire growth rate and maximum heat release rate was in many cases significantly increased, especially if the room was well ventilated, the ceiling height was relatively low and the room floor area was moderate. However, using thermally thin materials (steel sheet) or materials with large heat storing capacity (concrete) very little change was seen on the growth rate or maximum heat release rate. In conclusion it was recommended that one should take precaution when using recommended design fires in buildings with certain characteristics since it potentially can overestimate the safety in such case.

This paper uses four different simple geometrical shapes to simulate a large-scale heavy goods vehicle (HGV) tunnel fire experiment using Fire Dynamics Simulator, version 6 (FDS6) in order to investigate the influence of using different fuel package shapes. Simulations also investigate the influence on temperature profiles when a large target is placed downstream of the fuel package. Predictions of flame extension, temperature profiles and gas species concentrations are compared with the experimental data. The use of the geometrical shapes causes significant differences in flame extension lengths during the fully developed fire phase. The variation in temperature predictions caused by using the different fuel shapes are insignificant when a large target is present behind the fire, however this is not the case if the target is omitted especially during the fully developed phase.