细水雾控制高层住宅烟道火灾的有效性及参数优化

为了有效控制高层住宅厨房烟道火灾,构建细水雾控制厨房食用油火和带分支烟道的高层住宅厨房烟道油垢火的FDS数值模型,分析高层住宅厨房烟道细水雾灭火系统有效性的影响因素及最佳设计参数。结果表明,如果未能即时扑灭高层住宅底层厨房食用油火,在强烈的烟囱效应作用下,高温火焰和烟气会引燃烟道内油垢,造成火势的迅速蔓延。本文所建的30 m高厨房烟道火模型中,最佳细水雾灭火系统运行模式为关闭厨房抽油烟机,即时开启厨房灶台上方和主烟道内分段设置的细水雾喷头,雾流量分别为0.6,10 L/min,细水雾最佳参数为喷射流速10 m/s、喷射角度60°、水雾粒径500 μm。     

A Relative Time Analysis of the Performance of Residential Smoke Detection Technologies

A statistical study was conducted to compare the performance of different residential smoke detector technologies when exposed to different fire types. In order to facilitate comparisons between different fire and smoke growth rates, a non-dimensional smoke detector activation relative time was employed. Data from four major experimental studies was analyzed utilizing the relative time approach. The Common Language Effect Size, a measure of the probability that a particular detector technology will be the first to detect a fire of a particular type, was used to assess detector performance. The analysis confirmed previous results that ionization detectors, on average, respond faster to flaming fires, and that photoelectric detectors, on average, respond faster to smoldering fires. More importantly, this study also determined that the responses of ionization, photoelectric, and combination technologies are statistically equivalent for any given future residential fire That is, it cannot be determined with confidence which detector technology will alarm first to the next fire. Additionally, the analysis found that this statistical equivalence between detector technologies has not changed in the last 35 years despite increased fire growth rates associated with changes in furniture materials over that same time span.     

Risk factors for fatal residential fires

Residential fires are the most important cause of fire-related mortality in the United States. Previous research has concentrated on fatal fires in urban areas; considerably less is known about fatal fires in rural areas.We studied fatal and nonfatal residential fires in predominantly rural areas. Using a casecontrol design, we compared all 151 fatal fires (cases) in single-family dwellings in North Carolina during a 13-month period with a sample of nonfatal fires (controls). Case fires were identified through the medical-examiner system, and control fires that occurred within a few weeks of the case fires were chosen from the records of randomly selected fire departments statewide. For each fire, fire officials were interviewed about the dwelling, the fire, the people involved, and the fire-response system.Although heating incidents were the leading cause of fires, fatal fires were more likely to have been caused by smoking (31% of fatal fires vs. 6% of nonfatal fires). Mobile homes posed a higher risk of death if a fire occurred (odds ratio, 1.7; 95% confidence interval, 1.1 to 2.6), as did the absence of a smoke detector (odds ratio, 3.4; 95% confidence interval, 2.1 to 5.6). Smoke detectors were more protective against death in fires involving young children and when no one present was impaired by alcohol or drugs or had a physical or mental disability. The presence of an alcohol-impaired person was the strongest independent risk factor for death in the case of a fire (odds ratio, 7.5; 95% confidence interval, 4.4 to 12.7).In conclusion, residential fires are most likely to be caused by heating equipment or smoking materials. The risk of death is greatest in fires in mobile homes, in those involving alcoholimpaired persons, and in those in houses without smoke detectors. Reprinted with permission from The New England Journal of Medicine, 1992 Sep 17, 327 (12), pp. 859–863.     

Video Image Detection and Optical Flame Detection for Industrial Applications

In order to provide a technical basis for the selection and use of flame detectors in challenging industrial applications, an experimental study was conducted. Multiple flame detectors were tested in numerous scenarios representative of those expected in industrial applications. The study systematically evaluated the fire detection performance of devices at different distances from fires and with different detector viewing angles relative to fuel type, a range of obstructions and exposure to nuisance/interference sources. Limited comparisons between the “state of the art” Video Image Detectors and Optical Flame Detector candidate systems to older flame detector technologies were included.     

Prediction of fire detector response

Reliable fire detection is an essential aspect of fire protection in residential and industrial applications, both for the safe evacuation of people and for fire control or extinguishment. Assessment of the necessary detection response requires identification/quantification of: (1) the appropriate fire detector characteristics; (2) the environment generated by the fire: and (3) the fire hazard. In this paper, a generalized response theory for fire detectors is presented together with special cases for specific detector types. The fire environment and fire hazard are examined within a defined set of detection criteria and for a selected application to duct fires.     

Typification of Fires in Buildings in Spain

Although the Dirección de General de Protección Civil (DGPC), an agency of the Spanish government, has been responsible for the collection of data and the statistical analysis of fires since 1985, it has not as yet issued any reports. It is true that a couple of studies have been made, but in neither case did they use a standardized methodology but relied simply on the heterogeneous information provided by the fire brigades which cooperated in the studies. At that time Spanish fire brigades did not have special units for professional fire investigation, nor was the information derived from standardized methodologies suited to research purposes. In addition, information was extremely scarce and basic, focussed only on the fire, the use of the building and personal data of the victims. In this context, the project for a Fire Investigation Unit in the Fire Brigade of Málaga (the sixth largest Spanish province in inhabitants) was set up. Although inspired in the methodologies used in the USA and in the UK, the aim was to create a customized methodology for the first scientific investigation of fires in Spain. Our research was conducted in 2007. Using the methodologies of the USA and the UK, our own methodological approach and the Spanish regulations, we drew up a questionnaire with 110 variables arranged into 6 modules. We studied 96 fires out of the 154 emergency fire calls received in 2007, having omitted some emergency calls for various reasons. Our results revealed that it was necessary to generalize the installation of fire extinguishers in residential buildings, to train the general public in the use of these devices, to promote the use of fire and smoke detectors in residential buildings, to encourage the inspection and control of old electric installations and to monitor the new installations, to generalize the implementation of emergency and evacuation plans and to design new systems and materials for the cabinets where hand-held extinguishers are stored.     

Detection of smoke gases by solid state sensors — A focus on research activities

Conventional smoke detection in fire alarm systems is based on a measurement of either physical properties of smoke aerosols (ionization and optical detectors), temperature increase (thermal detectors) or electromagnetic radiation emitted by the fire (radiation detectors). Not much emphasis has been put on smoke gases as signatures of various types of fires. In this paper the most elementary gases produced in CEN-norm fires are qualitatively discussed in order to define levels of gas concentrations reached on time scales typical of early fire warning. Based on that information, various principles and the current state of the research and development of solid state gas sensors are presented and discussed. These are, in particular, the solid state electrolyte, the metal oxide semiconductor, the silicon semiconductor device element and, finally, the microcalorimeter. It is concluded that, with the exception of the last mentioned operating principle, solid state gas detection could provide a viable alternative or additional means for the detection of smouldering or pyrolytic fires at an early stage.     

Advanced fire detection algorithms using data from the home smoke detector project

The primary goal of this study is to develop fire detection algorithms for use in residential occupancies that reduce the nuisance sensitivity and detect fires at least as fast as conventional ionization and photoelectric detectors. An analysis is conducted using the output from ionization, photoelectric and carbon monoxide (CO) detectors, and a thermocouple measurement from 32 fire tests and 11 nuisance tests. Eight parameters are identified from the data collected from the four sensors by considering the magnitude and rate of rise of the output from each sensor. Algorithms are developed from these eight parameters using three approaches: analyzing the value of a single parameter relative to the response of commercial detectors given fire and nuisance sources, conducting the same analysis with two or three parameters and conducting the same analysis with a principal component analysis (PCA) of all eight parameters. The best fire sensitivity and nuisance immunity was observed for three algorithms: temperature rise and CO; CO and ionization detector; and temperature rise, CO and ionization detector.     

厨房火灾危险性分析与专用灭火装置

分析了食用油火灾的危险性,指出了食用油灭火的机理,提出了厨房灭火装置的选用原则,达到减少火灾损失、促进厨房专用灭火装置发展的目的,为同行设计厨房专用灭火设备提供参考。     

Rapid Detection and Suppression of Mining Equipment Cab Fires

The National Institute for Occupational Safety and Health (NIOSH/PRL) conducted a series of large-scale experiments to evaluate the effectiveness of optical flame detectors, photoelectric smoke detectors, and combined ionization and photoelectric smoke detectors for rapidly detecting mining equipment cab fires. The detector alarm times were then used to trigger the discharge of a fire inerting system inside the cab to suppress cab material fires. This paper discusses the types of fire detectors tested, the experiments that were conducted, and the results that were obtained. Conclusions are that rapid detection of equipment cab fires can be achieved to trigger the discharge of a fire inerting system inside the cab to protect the operator in the cab.     

Fire detector systems with ‘distributed intelligence’ the pulse polling system

Well over a million fire detectors are currently in use in the Federal Republic of Germany. Provided they are correctly installed and efficiently maintained, they detect fires reliably at a very early stage. At the present time, the false alarm rate equals about 1% of the number of installed detectors per annum. This false alarm rate must be at least proportionately reduced as further detectors are installed.

Since it is scarcely possible to improve tried-and-tested detector designs, the employment of higher-grade detector signal processing methods suggests itself.

However, ‘more intelligent’ detector signal processing using microprocessors calls for an entirely new fire detection system structure: detectors which independently ‘decide’ whether an alarm criterion is met and then initiate an alarm are replaced by sensors which continuously transmit their measured values to the ‘intelligence’ panel for evaluation. Passive panels which simply receive alarm signals from activated detectors and indicate these or transmit them to the fire brigade are replaced by active processors using permanently improved algorithms for the detection of real fires.

A structural change of this type is possible provided the positive — and the customary — characteristics of the conventional technique are not lost, viz. two-wire lines between detector and panel, simple installation and handling, easy detector replaceability, low cost, etc.

The pulse detector technology is described in detail; it combines the simplicity of conventional fire detection systems with new characteristics, e.g. identification of individual detectors, permanent functional check of all connected detectors, automatic notification of maintenance requirement prior to a slowly developing fault (e.g. such as that caused by corrosion or contamination), uniform response sensitivity unaffected by drifting from the operating points of the detectors and, above all, greater protection against false alarms.     

Findings of the International Road Tunnel Fire Detection Research Project

Fire detection systems are essential fire protection elements for road tunnels to detect fires, activate safety systems and direct evacuation and firefighting. However, information on the performance of these systems is limited and guidelines for application of tunnel fire detection systems are not fully developed. The National Research Council of Canada and the Fire Protection Research Foundation, with support of government organizations, industries and private sector organizations, have completed a research project to investigate current fire detection technologies for road tunnel protection. The project included studies on the detection performance of current fire detection technologies with both laboratory and field fire tests combined with computer modelling studies. This paper provides an overview of the findings of the project. Fire detectors, fire scenarios and test protocols used in the test program are described. A summary of the research results of the series of full-scale fire tests conducted in a laboratory tunnel facility and in an operating road tunnel as well as of the computer modelling activities will be reported.     

Polycyclic Aromatic Hydrocarbons (PAHs) Quantified in Large-Scale Fire Experiments

A number of large-scale fire experiments with detailed quantitative analysis of polycyclic aromatic hydrocarbon (PAH) including PAH congener distribution have been conducted by SP. This data is reviewed here and is further assessed with regard to toxicity applying a Toxic Equivalency Factor (TEF) model for estimation of cancer potential. The PAH yield data from the large-scale fire experiments is also compared to emission factors from other combustion sources. The study shows that full-scale fire experiments with different products exhibit a large variation in total PAH yields. Fires with products containing flame retardants were shown to produce the highest yields and generally a more toxic mixture of PAHs than fires with non-flame retarded products. The distribution of individual PAH congeners is generally quantitatively dominated by low molecular weight PAHs, whereas a small number of medium to high molecular weight PAHs are most important in determining the toxicity of the PAH mixture. The large-scale fire experiments indicate that fires normally produce orders of magnitudes higher yields compared to, e.g. modern residential combustion devices. The relative distribution of individual PAHs, which determines the toxicity of the PAH mix, is similar for the fires and open burning data studied, in that benzo(a)pyrene and dibenz(a,h)anthracene dominate the toxicity of the mix as a whole.     

Using multivariate statistical methods to detect fires

Fire detectors must accurately detect fires, but they should not respond to false alarms. Contemporary smoke detectors sometimes cannot discriminate between smoke and odor sources. These detectors can also be slow in responding to smoldering fire sources. In this paper, a statistical approach for detecting fires based on fusing sensor signals from multiple sensors is presented. The multivariate statistical approach, called principal component analysis, is used to compress the sensor information down to a small number of variables that can be interpreted more easily than the raw sensor signals themselves. Experimental results presented here show that the proposed approach is more accurate than a conventional smoke alarm, particularly for early detection of smoldering fires. However, this new approach does not overcome the problem of false alarms. In spite of this current limitation, the method discussed holds great promise for future fire detection applications.     

Monitoring Multiple Aspects of Fire Signatures for Discriminating Fire Detection

Numerous researchers are exploring multisensor detection as the principal means of discriminating between fire and nuisance sources. Multisensor detectors can monitor multiple aspects of a wide variety of signatures produced by flaming fires, non-flaming fires, and nuisance sources. This paper describes one program of small- and large-scale experiments that has been conducted using a prototype advanced fire detector with multiple gas sensors. An elementary analysis is applied to demonstrate that spacing guidance can be rationally developed for multiple gas sensors to detect fires of a particular threshold fire size, i.e., heat release rate. Discriminating between flaming fires, non-flaming fires, and nuisance sources could be achieved using either a threshold concentration or CO₂ rate-of-rise to identify flaming fires and a CO or CO₂ rate-of-rise for non-flaming fires. Time to detection was also compared to commercial smoke detectors, and the reductions in time were noted.     

Fire in a residential building: Comparisons between experimental data and a fire zone model

Fire hazards in residential buildings were investigated by conducting a range of fire experiments on a typical New Zealand dwelling built for this purpose. Hazards evaluated ranged from limited liquid-fuel fires to larger-scale burns using items of furniture. The effectiveness of detection and suppression devices was also tested.A series of experiments in a three-bedroom dwelling were conducted and included both a nonflashover and a flashover fire, and a selection of experimental results were analyzed to determine smoke and gas movement together with temperature rises in the various rooms. These results were compared to the predictions of the CFAST fire and smoke transport computer model.     

Smoke detectors in apartments and one-family houses: Fire risk, property loss and the presence of smoke detectors

This study compared the changes in fire risks and average monetary compensation for property loss before and after the distribution of 21 000 free home smoke detectors from a local insurance company. Life safety and injuries to people were not considered. To control for changes that were not due to the large increase in smoke detector coverage, a second insurance company in the same geographical area was added as a comparison, or control group. Average monetary compensation and fire risks were compared for small, medium-sized and heavy fires. The results showed no general effect of the sharp increase in smoke detector coverage on fire risk and compensation paid by the insurance companies. For the heavy fires, though not for the small and medium-sized fires, there was a significant decrease in compensation paid by the company with the free smoke detector. The reduction in compensation paid was small compared to the yearly costs of the batteries for the smoke detectors. The results were discussed in terms of smoke detectors as a technical device and a self-selection of fire safety conscious persons to the group that install a smoke detector in their homes.     

Advanced fire detection using multi-signature alarm algorithms

The objective of this work was to assess the feasibility of reducing false alarms while increasing sensitivity through the use of combined conventional smoke detectors with carbon monoxide (CO) sensors. This was accomplished through an experimental program using both real (fire) and nuisance alarm sources. A broad selection of sources was used ranging from smoldering wood and flaming fabric to cooking fumes. Individual sensor outputs and various signal-conditioning schemes involving multiple sensors were explored.The results show that improved fire-detection capabilities can be achieved over standard smoke detectors by combining smoke measurements with CO measurements in specific algorithms. False alarms can be reduced while increasing sensitivity (i.e., decreasing the detection time for real fires). Patented alarm criteria were established using algorithms consisting of the product of smoke obscuration and the change in CO concentration. Alarm algorithms utilizing ionization detector smoke measurements proved to be more effective than measurements from photoelectric detectors.     

Cigarette Fires Involving Upholstered Furniture in Residences: The Role that Smokers,Smoker Behavior,and Fire Standard Compliant Cigarettes Play

Residential structure fires pose a significant risk to life and property. A major source of these fires is the ignition of upholstered furniture by cigarettes. It has long been established that cigarettes and other lighted tobacco products could ignite upholstered furniture and were a leading cause of fire deaths in residences. In recent years, states have adopted fire standard compliant cigarettes (‘FSC cigarettes’) that are made with a wrapping paper that contains regularly spaced bands, which increases the likelihood of self-extinguishment. This paper measures the effectiveness of FSC cigarettes on the number of residential fires involving upholstered furniture, and the resulting fatalities, injuries, and extent of flame spread, while accounting for the under-reporting of fire incidents. In total, four models were estimated using fire department data from 2002 to 2011. The results provide evidence that FSC cigarettes, on average, reduced the number of residential fires by 45%, reduced fatalities by 23%, and extent of flame spread by 27% in 2011. No effect on injuries was found. Within each state, effectiveness is moderated by the number of smokers and their consumption patterns. In general, FSC cigarettes are more effective in places with a large smoking population who engage in heavier smoking. There is a very limited effect on the lightest of smokers, suggesting behavioral differences between heavy and light smokers that influence fire risk.     

变电站电缆沟火灾探测试验与数值仿真研究

为探讨火灾探测器灵敏度对电缆沟火灾响应的影响程度,验证火灾监控系统的准确性,应用点式温度探测器、点式烟雾探测器、电缆式感温探测器和吸入式烟雾探测器4种火灾探测器,在标准变电站电缆沟防火分区内进行了全尺寸电缆火灾试验,测试不同灵敏度火灾探测器的火灾报警序列。根据电缆沟的实际尺寸,利用FDS搭建模拟明火和阴燃两种不同火灾场景,对不同灵敏度火灾探测器的温度场、有毒气体质量浓度和火灾报警顺序进行了分析和讨论。试验结果表明,在变电站电缆沟火探测中,电缆式感温探测器、吸入式烟雾探测器、点式感烟探测器火灾平均响应时间分别为41.2,111.4,331.8 s;吸入式感烟探测器的灵敏度对探测结果影响较大,其火灾报警响应时间比电缆型线性温度探测器约延迟50%。