Flashover Fire Research Articles

Evaluation of Intumescent Coatings for Shipboard Fire Protection

In response to several claims from Manufacturers that intumescent coatings could be used in place of fire insulation and provide equal protection to shipboard structures during a fire, U.S. Navy conducted an extensive investigation of several fire protective coatings for use aboard ship. These fire protective coatings included water and solvent based coatings, insulative coatings, and foams. The objective of this program was to identify passive fire protection (PFP) coatings for shipboard interior applications capable of meeting U.S. Navy (USN) fire resistance requirements (DRAFT MIL-PRF-XX 381) of 30 min rating with backside average temperature rise less than 139 C using UL-1709 fire curve (post flashover fire). This evaluation consisted of small scale fire, adhesion, and impact tests; intermediate scale room corner fire tests, and full scale fire tests conducted aboard ex-USS SHADWELL. The test results with steel substrate show that all candidate coatings failed to meet minimum U.S. Navy fire resistance criteria when used as stand-alone coatings. Furthermore, many coatings demonstrated poor adhesion, and fell off from the substrate during the fire test. These data have led the Navy to conclude that intumescent coatings tested in this study are not sufficient to protect shipboard spaces during a fire and are not equivalent when used alone as direct replacement for batt or blanket type fibrous fire insulation (mineral wool, StructoGard) installed aboard U.S. Navy ships. However, U.S. Navy smallscale fire tests have also demonstrated that some of the intumescent coatings, when applied over substrates such as Glass Reinforced Plastic (GRP), did reduce flame spread and smoke generation.

물분무를 이용한 화재제어에 관한 실험적 연구

The present study investigates the fire suppression characteristics using a water mist fire suppression system. The fire extinguishing times are measured for various fire sources, fuel types, and different total flooding rates of water mist. Pool fire with hydrocabon fuel is successfully extinguished within a minute under the operating conditions of the water mist system. Two different regimes of the smoke layer cooling are observed, such as rapid and slow cooling processes. The regimes are divided by threshold time which is calculated with auto-correlation function. The threshold time for the initial cooling decreases with increasing water flow-rates and fire sources. These initial cooling effects play an important role in preventing the occurance of flashover fire by the initial fire suppression.

Using Sensor Signals to Analyze Fires

Building fire sensors are capable of supplying substantially more information to the fire service than just the simple detection of a possible fire. Nelson, in 1984, recognized the importance of tying all the building sensors to a smart fire panel [1]. In order to accomplish a smart fire panel configuration such as envisioned by Nelson, algorithms must be developed that convert the analog/digital signals received from sensors to the heat release rate (HRR) of the fire. Once the HRR of the fire is known, a multiroom zone fire model can be used to determine smoke layers and temperatures in the other rooms of the building. This information can then be sent to the fire service providing it with an approximate overview of the fire scenario in the building. This paper will describe a ceiling jet algorithm that is being developed to predict the heat release rate (HRR) of a fire using signals from smoke and gas sensors. The prediction of this algorithm will be compared with experiments. In addition, an example of the predictions from a sensor-driven fire model, SDFM, using signals from heat sensors, will be compared with measurements from a full-scale, two-story, flashover townhouse fire.

Application of Water Mist Fire Suppression Systems in Small Retail Shops

Protecting small retail shops packed with combustible goods by sprinkler system might not be too satisfactory. Any delay in system activation will lead to a flashover fire. Also, there might be serious water damage which is not good for shops selling expensive items. Alternative fire protection systems should be searched for. Water mist might be effective for suppressing postflashover fires if the system is designed properly. Whether water mist fire suppression systems can be used in the small shops is discussed in this paper. Key factors affecting the system performance will be discussed. Potential application strategies are outlined. An example was used to illustrate the design of the system.

Determination of actions due to fire: recent developments in Bayesian risk assessment of structures under fire

AbstractIt is well recognized that the probability of fire start and conditional probability of fire flashover, given fire starts, may be expected in a given building within a broad range, depending on the applied fire safety system. Within the fire safety system the scale of active fire protection can be used to determine the design fire load. Similarly the probability of structural failure and extent of possible injuries from a fire depend considerably on the system of structural protection and arrangement of escape routes. Thus, risk assessment of structures under fire should be based on probabilistic concepts, taking into account various conditional probabilities, for example the proportion of fully developed fires of all started fires, i.e. the conditional probability that of fire flashover, provided that fire has started.It appears that Bayesian causal (belief) networks, supplemented by appropriate input data, may provide an effective tool to analyse the significance of various characteristics of a fire safety system in terms of the resulting probability of flash over and other unfavorable consequences. Moreover, Bayesian networks, supplemented by decision nodes and a number of utility nodes (influence diagram), make it possible to estimate the expected total risk for both the buildings and their occupants and the actions due to the fire.This review paper indicates that application of Bayesian causal (belief) networks may improve assessment of expected total risk, taking into account significant fire safety measures, including structural protection and arrangements of escape routes.

A comprehensive study of externally venting flames —: Part II: Plume envelope and centre-line temperature comparisons, secondary fires, wind effects and smoke management system

In this part, comparisons are presented between predicted and experimental plume characteristics in terms of plume envelope and centre-line temperatures of venting flames during full-scale flashover fires. Window cracking times and heat transfer from the external plume are discussed in relation to the possibility of a secondary fire. Surface and line approximations are developed to represent the change in the external plume temperature with height, width and depth within the plume above the window opening.

Fire performance of timber construction

This paper is a review of the performance of timber buildings exposed to fire. Important distinctions are made between the impacts of pre- and post- flashover fires, and between the performance of light timber framing and heavy timber construction. Recent literature is reviewed.

A Comparison of CFAST Predictions to USCG Real-Scale Fire Tests

The zone model CFAST was used to make predictions of single room pre- flashover fire tests conducted in a steel enclosure. These results were then compared with previously published measurements obtained in fire tests. Tests included diesel pool fires, polyurethane slab fires, and wood crib fires. Half of these tests used natural ventilation (window, 1/4 door, and full door) while the remaining tests used forced ventilation (0.25 m 3 /s, 0.38 m 3 /s, and 0.61 m 3 /s). With the exception of heat release rates, all CFAST inputs were selected without knowledge of the experimental results. Key variables com- pared include the upper layer temperature, the hot layer interface location, and ceiling tem- peratures. Overall, predictions made by CFAST were in good agreement with the data. There was a general tendency to over predict both the hot gas layer temperature and the boundary surface temperature which may be due to under prediction of boundary heat losses. Experimental results showed that heat release rates varied with ventilation configu- rations by as much as a factor of 3. This observation indicates that the wide practice of using free burn heat release rate data in compartment fire predictions can result in over prediction of compartment fire conditions.

Flames venting externally during full-scale flashover fires: two sample ventilation cases

The effects of burn room ventilation and environmental conditions on venting plumes have been examined during a series of full-scale flashover fires at the Experimental Building Fire Facility of CESARE (Centre for Environmental Safety and Risk Engineering) of Victoria University of Technology. The focus in this paper is on two typical test cases, each corresponding to one of the two ventilation classes examined during this series of fires, namely, Class 1: through-draft (flow through) and Class 2: no-through-draft conditions. These conditions correspond to the open door and window in the burn room, and the closed door and open window, respectively. Three-dimensional temperature contours outside the burn room have been used to study plume dispersion. Total and radiant heat flux measurements, combined with the overall reach and severity of venting flames indicate that flames emerging from the room of fire origin are capable of initiating a secondary fire in the level above. While each fire has a natural periodicity innate to the combustion process itself, any swirling motion of the venting plume has been observed to be caused by a cross-wind.

On the "Cabins" Fire Safety Design Concept in the New Hong Kong Airport Terminal Buildings

The "cabins" fire safety design concept in the terminal buildings of the new Hong Kong international airport is evaluated in this paper. Retail shops in the terminal hall are taken as cabins in which it is highly possible to get a flashover fire. Correlations for the flashover time were derived using sixty simu lations for cabins of different sizes employing the fire protection engineering tool FASTLite. Heat generated by the fire would be conducted out through the cabin wall or ceiling to the terminal hall and the associated heat transfer equations are reviewed. Upon flashover, the whole cabin becomes a large hot object and a ther mal plume would be induced. Smoke generated in the cabin would flow out from the door left opened for human egress. Computational Fluid Dynamics (CFD) was used to study the smoke filling process in the terminal hall for cases with and without a cabin.

Application of field model and two-zone model to flashover fires in a full-scale multi-room single level building

This paper presents a comparison of the results from a computational fluid dynamics (CFD) model and a two-zone model against a comprehensive set of data obtained from one flashover fire experiment. The experimental results were obtained from a full-scale prototype apartment building under flashover conditions. Three polyurethane mattresses were used as fuel. The CFAST two-zone model (version 2.0) was also used to predict results for this flashover fire test. The mass release rate, gas temperature, radiation heat flux and gas compositions (O 2 , CO 2 and CO) were measured. A CFD program, CESARE-CFD Fire Model, has been developed and was used also to predict results for polyurethane-slab fire. A simple flame spread model was incorporated into the CFD program to predict the mass release rate and heat release rate during the fire instead of providing it as an input as is required for most zone and CFD models. It was found that the CFD model provided reasonable predictions of the magnitude and the trends for the temperatures in the burn room and the species concentrations, but over-predicted the temperatures in the adjacent enclosures. From a life safety perspective, the CFD model conservatively predicted the concentrations of CO and CO 2 . The predicted temperatures from the CFAST fire model agreed well with the experimental results in most areas. However, the CFAST model under predicted the temperature in the lower layer of the room of fire origin and the concentration of CO in most areas.

A study of non-flashover and flashover fires in a full-scale multi-room building

Realistic fire environments in a prototype multi-room apartment in a multi-storey building are studied. The fires are designed as non-flashover and flashover types, using standard polyurethane mattresses as fuel. A comprehensive set of experimental data is presented. The measured results include flame spread velocity, mass release rate, gas temperature, radiation heat flux and gas analysis. A computational fluid dynamics (CFD) model, called a CESARE-CFD fire model, has been used to simulate these polyurethane slab fires. The CFD model is described by three-dimensional transport equations for mass, momentum and enthalpy. The turbulence flow was modelled using the k−ϵ model. A soot formation model and a flame spread model were incorporated into the CFD model. The flame spread velocity and the mass release rate of the polyurethane slab fires were predicted in this study. It was found that the CFD model provided reasonable predictions of the magnitude and trends for the experiments both in the non-flashover and flashover fire cases.

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.