A computer model for estimating the response of sprinkler links to compartment fires with draft curtains and fusible link-actuated ceiling vents

A computer program, LAVENT, is now available which computes the heating of fusible links due to the presence of a ceiling jet imbedded in an upper layer. An important new feature in this program is that the two-dimensional structure of the ceiling jet is taken into account such that the location of the link beneath the ceiling plays a role in the response of the link. The links can be used to activate ceiling vents such that the effect of venting the upper layer on the ceiling jet may be studied. Additional applications would include the study of upper layer containment through the use of a combination of draft curtains and ceiling vents. The geometry modeled by the program is that of a large compartment enclosed by a combination of walls and draft curtains.     

An experimental study of fire growth and suppression of roll paper at small scales

This study investigates roll paper fire using laboratory-scale experiments, with emphasis on water transport on burning surfaces for sprinkler suppression. Freeburn, water transport and suppression experiments were conducted using different types of paper with various basis weight and water absorptivity. For fire suppression, the experimental results showed different water transport patterns that are sensitive to the burning surface conditions. This is in contrast to the water transport under no fire conditions in straight vertical rivulets exhibiting highly non-uniform distribution along the roll perimeter. For roll paper fire growth, both surface delamination and exfoliation play a crucial role, with the delamination length increasing either linearly or exponentially with time and the exfoliation rates strongly dependent on paper basis weight. Although the effects observed at the small scale in this work may have differences from those at large scales, the experimental results yield insights for better understanding of fire growth and suppression mechanisms and provide extensive data for numerical model development and validation.     

Aerial firefighting against urban fire: Mock-up house experiments of fire suppression by helicopters

The Great Hanshin Earthquake in 1995 claimed approximately 6400 lives. The majority was killed in large fires after the earthquake. Roads were cut off and collapsed buildings blocked the access of fire engines to fire fields. Water mains were broken and lack of water prevented firefighting efforts. If aerial firefighting had been effectively applied, many lives could have been saved.     

Using suppression and detection devices to steer CFD fire forecast simulations

Firefighters would greatly benefit from a technology based on predictive fire simulations, able to assist their decision making process. For those simulations to be useful, they need a certain degree of precision and resolution that can only be provided by CFD type fire models. But CFD simulations typically take large periods of time to complete, and their results would thus not be available in time to be of use during an emergency. Due to the high complexity of fire spread dynamics that arises from the interaction between solid and gas phase and the corresponding physical-chemical processes (e.g. pyrolysis), the spread of the fire cannot be predicted from first principles in real-time using contemporary computers, and has to be given as parameters to the model. Data can be incorporated into the model to characterise the fire, but only a limited range of measurements are recorded in current buildings. While it might be possible that buildings of the future incorporate a higher density of sensors than contemporary buildings, it is likely that emergency response systems will have access only to conventional data such as smoke detectors and sprinkler activation time for the foreseeable future. In this study the use of conventional detection and suppression devices for the estimation of fire characteristics by means of an inverse modelling framework is explored. Additionally to the growth rate of the fire, the location of the fire origin is successfully estimated. Inverse CFD modelling and tangent linearisation is used to assimilate the data. The nature of the incoming data is consistent with current detection and suppression devices, in such that only a time of activation is recorded and fed into the model. It is shown that the growth rate of the fire and the location of its origin can be correctly and efficiently estimated using sprinkler and smoke detector activation time only. It is further shown that the estimated spread rate is not sensitive to fire origin location.     

Experimental study of water mist fire suppression in tunnels under longitudinal ventilation

This paper studies water mist fire suppression under different longitudinal ventilation velocities in tunnels by small-scale experiments. After a scaling study, two mist nozzles are used for suppressing crib fires under 5 ventilation speeds. The result comes out that fire suppression process can be divided into three stages including flame unitary restraining stage, surface flame extinguishing stage and inside flame suppression stage. Several factors influencing efficiency are investigated. When the interval between mist nozzle and fire source enlarges, the relationship curve between fire suppression time and ventilation velocity shows a ‘V’ figure. The best ventilation speed exists. Following the rules summarized, a coupling system of water mist and ventilation may increase fire suppression efficiency remarkably.     

Principles for fire detection

A fundamental approach has been undertaken to provide principles for fire detection. Basic relationships have been developed for heat and chemical compound detectors and applied to duct and enclosure environments.     

A probabilistic occupant response model for fire emergencies

The present paper describes a probabilistic occupant response model for fire emergencies, which is integrated into a fire risk analysis model called CUrisk. Based on the PIA process, i.e., Perception, Interpretation and Action, the occupant response model predicts the probabilities of occupants perceiving fire signals due to direct perception, receiving fire alarms due to the activation of local alarms, sprinklers, the central alarm and the voice alarm, being warned by the other occupants and fire department, and taking actions including pulling the fire alarm, warning other occupants, calling the fire department, and commencing evacuation. The occupant response model is applied to predict the probabilities of evacuation initiation for a number of scenarios that consider combinations of fire detection and alarm systems for a mid-rise building. The results of the model show that asleep occupants need much longer response time to start evacuating and have lower probabilities of starting evacuation than awake occupants, which are consistent with what is observed in reality. Additionally, fire protection systems with only local alarms and only sprinklers connected to the central alarm can be improved significantly with systems with smoke detectors alone or combined with sprinklers connected to a central alarm, which result in higher probabilities of evacuation initiation with shorter delay times.     

Directions for improving manual fire suppression using a physically based computer simulation

The Swedish Fire Research Board and the U.S. Federal Emergency Management Agency are sponsoring a project to further the understanding of the basic mechanisms involved, as well as to support the development of standards for and to seek ways of improving the performance of portable fire suppression systems used by fire departments.This paper describes a physically based computer model developed to simulate one aspect of the problem: the manual suppression of postflashover fires. This includes: (1) an overview of the physical basis behind the model; (2) a comparison of model predictions with available experimental data, and (3) an analysis of fire suppression effectiveness using the model.The analysis concludes that, when direct access and extinguishment of the burning fuel is not possible, improved fire control occurs with water sprays having a Rosin-Rammler distribution of droplet sizes with volume-median-drop diameters in the 0.15 to 0.35 mm range. This agrees with available experimental data. It is also shown that fire fighting venting and standoff distance requirements may lead to more severe fires requiring more water for control; although venting and water spray induced air/gas flow also serve to channel hot steam and gases away from the fire fighter adding to his safety. The analysis also shows that allowing higher gas and surface temperatures at fire control through improved fire fighter protective clothing and equipment design reduces water flow rate requirements. Additional experimental work is recommended before all these conclusions are considered definitive. Reference: L. M. Pietrzak and G. A. Johanson, Directions for Improving Manual Fire Suppression Using a Physically Based Computer Simulation,Fire Technology, Vol. 22, No. 3, August, 1986, p. 184.     

A reference model of fire detection and monitoring system using BACnet

The objective of this paper is to introduce a reference model of BACnet-based fire detection and monitoring system using MS/TP and ARCNET protocols. The reference model is designed to satisfy the requirements of response time, survivability and flexibility. The reference model is operated on the basis of BACnet, a standard communication protocol for building automation systems. In this study, a simulator for the reference model of fire detection and monitoring system was developed. Using the simulator, this study examined the validity of the reference model proposed in this study. This study also evaluated the performance of the BACnet-based fire detection and monitoring system in terms of network-induced delay. Simulation results show that the reference model satisfies the requirements of fire detection and monitoring system.     

Early fire detection algorithm based on irregular patterns of flames and hierarchical Bayesian Networks

This paper proposes a new vision-based early fire detection method for real-world application. First, candidate fire regions are detected using a background and color model of fire. Probabilistic models of the fire are then generated based on the fact that fire pixel values in consecutive frames change constantly. These models are then applied to Bayesian Networks. This paper uses hierarchical Bayesian Networks that contain intermediate nodes. Four probability density functions for evidence at each node are used. The probability density functions for each node are modeled using the skewness of the color red, and three high frequencies obtained from a wavelet transform. The proposed system was successfully applied to various fire-detection tasks in real-world environments, and it effectively distinguished fire from fire-colored moving objects.     

细水雾特性及其灭火机理分析

介绍了细水雾的基本属性及其表征特性，分析了细水雾的灭火模型及灭火特性。结果表明，细水雾可实现多种灭火效应(燃料冷却、烟气冷却、辐射衰减、惰化作用)，可以达到高效、快速灭火的目的。     

浅谈影剧院火灾的预防与扑救

通过对影剧院火灾案例的分析，提出了对公众聚集场所，尤其是对大空间、有闷顶的场所的火灾扑救及预防措施，以避免公众聚集场所发生火灾后造成群死群伤。     

公路交通隧道火灾探测技术研究

通过油盘火试验和模拟研究隧道火灾探测技术.油盘火试验分汽车下着火和汽车后方着火,模拟分为发动机舱着火和乘客舱着火.只有闭路电视图像探测器和感烟探测器能探测到车辆下方火灾,线型光纤感温探测系统探测车辆后方火灾较快.探测系统对乘客舱火灾的响应时间比发动机舱火灾的响应时间长.以50 km/h行驶的移动车辆着火,所有探测器无响应.建议采用两种及以上技术进行探测.     

抑制谐波电气火灾防控系统的关键技术要求

阐述了抑制谐波电气火灾防控系统的控制原理、硬件结构与软件程序,介绍了采用自动抑制谐波方法防控电气火灾的主要功能,以及总谐波抑制率、气候与机械环境耐受性和电磁兼容性等关键性能要求。     

客船火灾烟气蔓延及火灾探测器响应试验研究

基于对某豪华客船的实地调研,搭建了客船客舱区域火灾烟气蔓延模拟试验平台,通过典型火源燃烧试验研究了客船客舱区域的烟气蔓延特性,得到起火客舱及人员疏散走道典型截面不同高度的温度分布规律,以及不同类型船用火灾探测器的探测响应时间。基于试验结论,提出客船火灾探测器选型及烟气控制建议,也可为客船人员安全疏散研究提供一定的借鉴。     

固定消防设施在灭火救援中的应用

固定消防设施在火灾初期阶段的作用是巨大的，无数次初期火灾都被自动喷水灭火系统扑灭。对于固定消防设施因故障而没有实现联动，在不能正常发挥作用的情况下，提出了消防队员如何利用固定消防设施实施救人、排烟、灭火等急切需要解决的技术和战术问题。     

A new type of fire suppressant powder of NaHCO3/zeolite nanocomposites with core–shell structure

A new type of particulate fire suppressant with core–shell structure was fabricated, in which zeolites 13X were encapsulated in the shell of nanosized sodium bicarbonate (NaHCO₃) particles. Laboratory-scale tests showed that thus-prepared nanocomposites displayed much-improved extinction efficiency than that of conventional sodium bicarbonate (NaHCO₃) dry powder with relatively shorter extinguishing time and less amount of agents required. Such an improved fire suppression performance could be reasonably ascribed to the unique core–shell structure and nanosize of the composite particles. The possible fire extinguishing mechanism of the composite powder was discussed, which involved the simultaneous functions of NaHCO₃ and zeolite.