建筑灭火器配置的技术要点

建筑灭火器是扑救初起火灾的重要消防器材 ,剖析了建筑灭火器配置时经常出现的问题和应考虑的技术要点 ,并举例说明。     

Performance evaluation of bromofluoropropene in extinguishing liquid fuel spray fires

Liquid fuel spray fires emit high radiation heat fluxes, posing great threat to humans. The study of suitable agents and techniques for extinguishing this particular type of fire is of great importance. In this study, degradable 2‐bromo‐3,3,3‐trifluoropropene (BTP), a new clean fire extinguishing agent, was tested for its effectiveness in extinguishing three types of liquid fuel spray fires, namely diesel, gasoline, and ethanol. Bench‐scale experiments were conducted in a 6 × 5 × 3 m compartment with natural ventilation. The liquid fuels sprayed at varying pressures were ignited by a small open flame and then extinguished by a portable BTP extinguisher. Results showed that BTP of less than 60.0 g could extinguish all liquid fuel spray fires of 0.20 to 1.0 MPa in less than 2.0 s. The results also showed that when compared with fire sparked by gasoline and diesel, it is significantly easier to put out ethanol spray fires because of its high flame temperature and low flame power. Based on well‐established fire suppression theories and experimental results, the detailed mechanism of how BTP functions as an extinguishing agent in the suppression of liquid fuel spray fires will be discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Faults in fire extinguishers

Specimens of dry powder, halogenated hydrocarobon and carbon dioxide extinguishers manufactured in 1972 were tested in that year as part of a monitoring scheme for fire extinguishers. Leakages and faults which prevented an extinguisher operating or might lead to it being discarded in a emergency are listed, and some of the other defects which were encountered are noted.     

Research on the influence of wollastonite fibers on the stability of foam extinguishment agent and its effect on the extinguishing efficiency of pool fire

Aqueous film-forming foam (AFFF) is a frequently used foam extinguishment agent for oil fires, but the foam stability of AFFF is not perfect, which results in poor fire extinguishing performance. In order to improve the foam stability of AFFF, wollastonite fibers were explored to increase the performance of foam extinguishment agent. The influences of wollastonite fibers' concentration on foam extinguishment agent's stability are studied. When the concentration of wollastonite fibers is 30.00 g/100 mL, the drainage time is prolonged, which is the best among all the formulas. Moreover, the fire resistance and fire-fighting performances are increased significantly due to the incorporation of wollastonite fibers. In order to reveal the effect of wollastonite fibers on the stability of foam extinguishment agent, the structure of the foam and the diameter of the bubbles are investigated. The results show that the complexity and compactness of foam layer's structure are very important for foam stability, and the fire-extinguishing performance is improved due to the introduction of wollastonite fibers.     

Sprinklered office fire tests

This paper presents data relating to the performance of sprinklers and detectors in real office fire situations. For sprinklers, these data are additional to that associated with the standardized testing used to determine the design delivery density and pressure requirements for various occupancy situations, and provide a useful insight into the effect of sprinklers on developing fires with various office situations. The data given in this paper include the times for activation of various types of sprinkler heads (normal and fast response), the efficacy of the systems as far as extinguishment is concerned, estimates of the maximum size of the fires prior to commencement of extinguishment and associated air temperatures at various locations within the office enclosures. Copyright © 2008 John Wiley & Sons, Ltd.     

Quantitative fire risk assessment of cotton storage and a criticality analysis of risk control strategies

Although fires can easily occur during cotton storage, research on cotton storage fire risk assessment is limited. This work focuses on cotton storage fire risk assessment and investigates the criticality of risk control strategies. Bow-tie and Bayesian network models are established to investigate the relationships among accident causes, safety barriers, and possible consequences. The results show that the first safety barrier (detection and extinguishment before fire brigade arrival) is more controllable and more effective than the second safety barrier (fire brigade). Based on the collected probability data, the probability and risk of a common accident are higher than those of a large accident and severe accident when safety barriers succeed; when the first safety barrier fails, the probabilities and risks of large and severe accidents increase by more than 2000 times. The criticality of safety measures is investigated by analysing their structural importance, probability importance, and critical importance. The critical events for fire occurrence are an open flame and sparks during storage, and the critical events for detection and extinguishment before fire brigade arrival are watchkeeper monitoring, regular patrolling, and automatic fire alarm systems. For cotton storage safety, this work and its outcomes are used to support the decision-making of fire risk prevention and control.     

氟碳表面活性剂应用研究

简要介绍了氟碳表面活性剂“三高”、“两憎”的化学性质,重点论述了氟碳表面活性剂在石油化工、消防、纺织、电镀等方面的广泛应用。     

Characterization of the fire environments in central offices of the telecommunications industry

Eight free burning and two sprinklered fire tests were performed with electrical cable trays and live digital switch racks in a large enclosure to simulate telecommunications central office (TCO) fires started by electrical overheating. Very‐slow‐growing (non‐flaming), slower‐growing (partially flaming) and low‐intensity‐faster‐growing (flaming) fires releasing gray‐white, gray, and black smoke, respectively, were observed in the tests. Under quiescent conditions present in the unvented enclosure fire tests for cables, very‐slow‐growing fires were detected in about 1452 s, whereas the slower‐growing fires were detected in about 222 s by commercial fire detectors. Under ventilation conditions typical of TCOs, detection times were very similar for the five types of commercial TCOs fire detectors used in the tests. The average detection times for slower‐growing fires (cable fires) and low‐intensity‐faster‐growing fires (digital switch rack fires) were 242±17% and 249±11%s respectively. The TCO procedures to reduce smoke damage from fires (on fire detection, inlet ventilation flow is turned off and exhaust flow is turned on) were found to be beneficial. The extent of smoke damage decreased significantly with an increase in the exhaust flow rate. The chloride ion mass deposition suggested that equipment recovery would be possible in the smoke environment if the cable vapor concentration could be reduced below about 3 g/m³. The metal corrosion rate was found proportional to the 0.6th power of the smoke concentration, similar to that found for the corrosion of metal surfaces exposed to aqueous solutions of HCl and HNO₃ and for acid rain with no protective layer at the surface. Sprinkler water was found to wash down the smoke deposits on the surfaces with little indication of corrosion enhancement. Copyright © 2003 John Wiley & Sons, Ltd.     

An efficient methodology for evaluating the nozzle performance of water-based automatic fire extinguishers

The performance of automatic fire extinguishers (AFE) was tested using a novel nozzle distribution test in relation to a point of visual approach. The visual nozzle distribution data was obtained from the mapping of the amount of the collected fire extinguishing agent to each position and the gradient was given in accordance with the visually collected amount. The results showed that the effective discharge time was determined by the nozzle structure and its size. The visual nozzle distribution test (VNDT) provided relevant information regarding the performance efficiency of AFE, including the nozzle coverage area, the effective amount of the fire extinguishing agent and the distribution uniformity of fire extinguishing agents, and calculations for the proper amount of a fire extinguishing agent to extinguish a fire. Consequently, the results indicate the VNDT is an excellent method for analyzing the performance efficiency of AFE.     

泡沫类灭火剂在化工企业火灾的应用

针对化工企业复杂多变的火灾情况,分析了不同种类的泡沫灭火剂灭火原理、性质以及适应扑救的化工火灾场所,为化工企业火灾扑救起到了一定的指导作用。     

A novel hot aerosol extinguishing agent with high efficiency for Class B fires

A novel hot aerosol extinguishing agent (HAEA), which is the combination of pyrotechnics and flame retardant technology, was found to have great efficiency in extinguishing Class B fires. A mixture of P and P₃N₅, referred to as P90x, was chosen as the reductant, and phase stabilized ammonium nitrate was chosen as the oxidant. This paper describes a study of the effectiveness of this agent in extinguishing n‐heptane fires (ie, Class B fires). We determined that the best efficiency was 15 g/m³ for extinguishing n‐heptane fires, four times more efficient than a traditional agent. The efficiency increases as the mass fraction of P90x rises. We also identified the key difference between the novel extinguishing agent and the traditional agent. The former consists of an inorganic phosphorus compound, while the latter is mainly comprised of KOH. Consequently, their extinguishing mechanisms are different. The phosphorus oxide of the novel HAEAs is the leading component to extinguish fire, which is more effective than alkali salts.     

Fire modeling of an emerging fire suppression system

Self-contained fire extinguishers are a robust, reliable and minimally invasive means of fire suppression for gloveboxes. Test methodology has been developed (experiments and computations) to predict fire induced tube wall failure in small scale compartments such as gloveboxes. A small scale test apparatus has been developed to characterize tube wall temperature and breakage properties. Computational tools have been used to better understand experiments. The heat release rate and heat flux have been accurately predicted because the forward predicted temperatures closely matched the experimentally measured values. Data generated from computational modeling of fire phenomena helps to identify the limitations of self-contained fire extinguishers.     

The fire safety of TV set enclosure materials,a survey of European statistics

The composition of enclosure materials used in many TV sets sold on the European market has changed significantly since the early 1990s. To determine the potential impact of this change on TV fire safety, a review of European and US TV set fire statistics has been carried out. TV set fires can have internal electrical causes due to faults not apparent at the time of manufacture, simple wear and tear, or a variety of external causes. Recent detailed statistics suggest that about one third of all TV fires are due to external ignition. Available data show that the significant drop in the rate of TV set fires experienced in Europe during the 1980s is not continuing today. In fact, the rate appears to be increasing in some countries, such as the UK and Sweden. The number of TV set fires in Europe is estimated as 100 fires per million TV sets per year due to internal ignition sources, at least an order of magnitude higher than in the USA where the fire safety classifications for TV set enclosure materials has been historically high. TV set fires have a dramatic impact on life and property. To avoid an increase in TV set fires, fire safety requirements should be increased, and public awareness of the importance of fire safety in TVs heightened. Copyright © 2000 John Wiley & Sons, Ltd.     

Jet fires: An experimental study of the main geometrical features of the flame in subsonic and sonic regimes

Although jet fires are usually smaller than other fires, they may lead to a destructive chain of events that can increase the scale of an accident. Therefore, their size should be predicted for accurate risk assessment. In the literature, most of the proposals for estimating jet fire size concern small jet fires (up to 2.5 m in length) or subsonic flames. In this study, experiments on relatively large propane jet fires in still air were performed. Vertical turbulent diffusion flames up to 10 m in length, with sonic and subsonic mass flow rates, were obtained using six different orifice exit diameters. The experiments were filmed with video and thermographic cameras and the resulting visible and infrared images were used to determine flame length and lift‐off distance. Expressions for estimating jet length as a function of several variables (mass flow rate, orifice exit diameter, Froude and Reynolds numbers) are also proposed. © 2008 American Institute of Chemical Engineers AIChE J, 2009     

Highway vehicle fire data based on the experiences of US fire departments

In 2003–2007, US fire departments responded to an average of 267 600 highway vehicle fires per year. These fires caused an average of 441 civilian deaths, 1326 civilian injuries, and $1.0bn (in US dollars) in direct property damage annually. Highway vehicles include cars, trucks, and other vehicles designed for highway use; highway vehicle fires can occur anywhere, not just on a highway. While these fires and associated losses have been falling in recent years, highway vehicles fires accounted for 17% of reported US fires, 12% of US fire deaths, 8% of US civilian fire injuries, and 9% of the direct property damage from reported fires. Data from the US Fire Administration's National Fire Incident Reporting System and the National Fire Protection Association's fire department survey were used to provide details about the circumstances of highway vehicle fires. Mechanical or electrical failures caused roughly three‐quarters of the highway vehicle fires but only 11% of the deaths. Collisions and overturns were factors contributing to the ignition in only 3% of the fires, but fires resulting from these incidents caused 58% of these vehicle fire deaths. The rate of bus fires per billion miles driven was 3.5 times that for highway vehicle fires overall. Copyright © 2012 John Wiley & Sons, Ltd.     

Plume equations for studying smoke-filling process in atria with a zone model

Application of zone model for studying atrium smoke-filling process was evaluated. The fire zone model FIRST was selected as the fire simulator. Studies were focused on the plume model, the geometry of the atria and the heat release rate of fires. Six plume models reported in the literature were reviewed. Their expressions on the velocity, temperature and mass flow were compared. Three halls of same volume but different shapes were taken as the samples. A small volume of 2000 m³ was used because a zone model should work in halls of this size. Numerical simulations of the fire environment in the atrium buildings with those six plume models were carried out using the zone model FIRST. A total number of 108 simulations were performed with nine sets of fires. © 1997 John Wiley & Sons, Ltd.     

Effect of particle granularity on smoldering fire in wood chips made from wood waste: An experimental study

Fires in wood waste storages cause financial losses, are difficult to extinguish, and emit large amounts of fire effluents. The mechanisms related to fires in wood chip piles are not well elucidated. To find suitable preventive measures for handling such fires in wood waste, a better understanding of the physical properties of wood waste is needed. The present study investigates how granularity affects mechanisms of smoldering fire and transition to flaming in wood chip piles. Eighteen experiments with samples inside a top-ventilated, vertical cylinder were conducted. Heating from underneath the cylinder induced auto-ignition and smoldering fire, and temperatures and mass loss of the sample were measured. The results showed that granularity significantly affects the smoldering fire dynamics. Material containing larger wood chips (length 4-100 mm) demonstrated more irregular temperature development, higher temperatures, faster combustion, and higher mass losses than material of smaller wood chips (length <4 mm). The larger wood chips also underwent transition to flaming fires. Flaming fires were not observed for small wood chips, which instead demonstrated prolonged and steady smoldering propagation. The differences are assumed to be partly due to the different bulk densities of the samples of large and small wood chips affecting the ventilation conditions. Increased knowledge about these combustion processes and transition to flaming is vital to develop risk-reducing measures when storing wood chips made from wood waste in piles.     

A calibration and sampling technique for quantifying the chemical structure in fires using GC/MSD analysis

This work presents an approach to measure, calibrate, and verify local concentrations of combustion products in pool fires steadily burning in a quiescent environment. This study describes a method that can be used to measure and verify the chemical species present in a fire. Such information is needed to assist in the development and validation of the chemistry subroutines in computational fluid dynamic fire models. Samples are extracted along the centerline of pool fires using a thermal quenching probe. Gas species volume fractions are analyzed using a custom Agilent 5977E Series gas chromatograph fitted with a permanent gas dual-column comprised of a Molsieve 5 Å and PoraBOND Q capillary columns in parallel flowing into mass selective and thermal conductivity detector. The system can identify and quantify a variety of stable reactant, intermediate, and product species collected from the fire, including several condensable species (eg, water, methanol, ethanol, and acetone). The time-weighted average soot mass fraction is determined using a gravimetric sampling method. In order to solidify the legitimacy of the measured gas composition, the results are verified by implementing different techniques, including the determination of the carbon to hydrogen ratio, calculating the argon to nitrogen ratio, and comparing the total moles estimated from the chromatogram peaks to the total moles of the injected sample.     

Improving Fire Suppression of Water Mist by Chemical Additives

Although water mist fire suppression system (WMFSS) is very common, there are concerns that the system is not efficient in controlling some fires. Additives are proposed to use in a WMFSS for better fire protection. In this paper, different groups of additives for WMFSS will be briefly reviewed. Experimental studies on the surface physical and chemical characteristic of polymethylmethacrylate (PMMA) under four groups of original polymer surface without treatment, self-extinguishment, suppressed by water mist and by water mist with sodium chloride NaCl, are reviewed. The surface profiles, element constitutions, binding energies and functional groups of PMMA surfaces were analyzed with scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR).

The near surface molten polymer and bubble layers in burning polymethylmethacrylate (PMMA) are found to be very complicated. The melted surface of burning PMMA is not saturated with pure MMA. Results also demonstrated that chemical reactions do occur while applying water mist. Water mist with NaCl can penetrate deeper on the burning surface of PMMA, suggesting that NaCl might be involved in the extinguishment reactions. The chloride ion from NaCl might be responsible for the interaction with the melting surface of PMMA.