Firing Environments

Table 111. Elemental volatilization and transformation of chemical and physical properties in the fire environment.

Accuracy of Oxygen Consumption Method. We have demonstrated that the oxygen consumption method can be used to quantify the amount of heat contributed to the fire environment by the walls. The heat release rate can be used as a diagnostic tool to evaluate performance of assemblies in question. 

The versatility and accuracy of the oxygen consumption method in heat release measurement was demonstrated. The critical measurements include flow rates and species concentrations. Some assumptions need to be invoked about (a) heat release per unit oxygen consumed and (b) chemical expansion factor, when flow rate into the system is not known. Errors in these assumptions are acceptable. As shown, the oxygen consumption method can be applied successfully in a fire endurance test to obtain heat release rates. Heat release rates can be useful for evaluating the performance of assemblies and can provide measures of heat contribution by the assemblies. The implementation of the heat release rate measurement in fire endurance testing depends on the design of the furnace. If the furnace has a stack or duct system in which gas flow and species concentrations can be measured, the calorimetry method is feasible. The information obtained can be useful in understanding the fire environment in which assemblies are tested. 

Parker, William J. An Investigation of the Fire Environment in the ASTM E-84... 

A further difficulty with small scale tests is that the relative fire performance and even the rank order of materials can change with different fire environments. Small scale tests can rarely reflect real life fire situations and examples already exist where reliance on small scale tests has let to hazardous full scale situations. 

Convections to objects in a fire environment usually occur under natural convection conditions. Turbulent natural convection is independent of scale and might be estimated from... 

Generally, compartment fire simulation models predict the fire development in a compartment under varying conditions. These types of simulations are useful for estimating tenability criteria, thermal insult to the compartment, and the likelihood of fire spread from one compartment to another. These types of models can be further subdivided into three categories based on their approach to simulating the fire environment the zone model, the field model, and the post-flashover model. 

Azone model calculatesthe fire environment by dividing each compartment in the model into two homogeneous zones. One zone is an upper hot smoke zone that contains the fire products. The other zone is a lower, relatively smoke-free zone that is cooler than the hot zone. The vertical relationship between the zones changes as the fire develops, usually via expansion of the upper zone. The zone approach evolved from observations of such layers in full-scale fire experiments. While these experiments show some variation in conditions within the zones, the variations are most often small compared to the difference between the zones themselves. 

Field models estimate the fire environment in a space by numerically solving the conservation equations (i.e., momentum, mass, energy, diffusion, species, etc.) as a result of afire. This is usually accomplished by using a finite difference, finite element, or boundary element method. Such methods are not unique to fire protection they are used in aeronautics, mechanical engineering, structural mechanics, and environmental engineering. Field models divide a space into a large number of elements and solve the conservation equations within each element. The greater the number of elements, the more detailed the solution. The results are three-dimensional in nature and are very refined when compared to a zone-type model. 

Although field models generate detailed estimates of the effects of compartment fire environments, they are time consuming because of the enormous number of computations that are made. Some effects, such as radiation, can only be treated on a simplified level. In many instances, such a detailed solution is not needed, and simpler approaches are appropriate. Field models are useful to resolve problems that yield excessively conservative results when calculated using other model types. 

The structural fire endurance of a structural system is a measure of its ability to resist collapse during exposure to a fire. The thermal/structural response models evaluate the time-temperature history within a solid exposed to a fire environment. The time-temperature history, or design fire exposure, can be a... 

Kuhlbusch, T. A. J. (1995). Method for determining black carbon in residues of vegetation fires. Environ. Sci. Technol. 29, 2695-2702. 

Review of smoke and toxic gas hazards in fire environment." Int. Symp. Fire Safety of Combust. Mater., Univ. of Edinburgh, Scotland. Oct., 1975. 

There are a large number of different methods used for bench-scale assessment of combustion toxicity, and the applicability of test data to lire hazard assessment is not always clear. Obviously, toxic potency data should not be used in isolation but should either be a part of a classification scheme or as part of the input to lire risk and lire safety engineering assessments. It is important that uncertainty or confidence limits should be used with toxic potency data, because they are often relatively large. Fire effluent toxic potency does not have a unique value but is a function of the material and the fire conditions, particularly temperature and oxygen availability in the fire zone, and also the fire environment (enclosure, geometry, and ventilation). To assess the fire hazard, toxic potency data must be relevant to the end use fire situation, and the fire condition, which can be defined using the ISO classification of fire stages. 

Beyler, C.L., Major species production by diffusion flames in a two-layer compartment fire environment,... 

Tewarson, A., Characterization of the fire environments in central offices of the telecommunications industry, Fire Mater., 2003, 27, 131-149. 

Larson D. A. and Small R. D., Analysis of the large urban fire environment. Part II. Parametric analysis and model city simulations. PSR 210, Pacific Sierra Research Corporation, Los Angeles, CA, USA, 120 pp. (1982). 

Maximum use temperatures are reported on refractory data sheets in terms of pyrometric cone equivalent (pee). In essence, this pee defines the temperature at which a small standard sized cone of the material slumps due to softening. Table 18-1 lists the pee numbers with the corresponding temperature limits and generic types of brick which fall within the various pee ranges. These reported pce s indicate a refractory s maximum use limit when exposed to a gas-fired environment however, they may actually soften at much lower temperatures due to reactions with the atmosphere they are containing. 

Fire resistance is the ability to prevent the passage of flame heat, smoke, and lire gases in a defined (often developed) fire environment. Polymer products arc rarely required to meet fire resistance requirements on their own, although they may be used in composite systems. Fire resistance tests of a similar nature are specified in many countries and by the ISO. 

As reviewed steel support, beams fail in a fire. To significantly extend the life of structural beams hardwood (thicker than steel, etc.) can be used thus, people can escape even though the wood slowly burns. The more useful and reliable structural beams would be using RPs that meet structural performance requirements with even a much more extended supporting life than wood. To date these RPs are not used in this type of fire environment primarily because of their high cost. 

L. Y. Cooper Interaction of an isolated sprinkler spray and a two-layer compartment fire environment, Int. J. Heat Mass Transf. 38, 679-690 (1995). 

For simulation, a rectangular compartment of 80 m long, 10m wide, 8 m high with opening at one end is considered. A section of the compartment is shown in Fig. 5 (half section of a symmetric compartment is shown). As the fire source a burning wood cribs is considered for this study of fire environment inside the compartment. The volume of the fire source is taken to be 9 m (3 m X 3 m X 1 m). The source is located 24 m from open end of the compartment, i.e. left portal. The heat release rate curve, as shown in Fig. 6 is taken from experimental results measured by Ingason et al. (1994) [19] on a wood crib fire imder natural ventilation condition as mentioned therein. 

Townsend, W., Anderson, C. E., Zook, X, Cowgill, X C., Comparison of thermally coated and un-insulated rail tank-cars filled with LPG subjected to a fire environment. Report FRA-OR D 75-32, US DOT, 1974... 

The duration of the fire test for air accident qualification was set at 60 min. Statistical data on fires resulting from air accidents support the conclusion that the 60 min thermal test exceeds most severe fire environments that a package would be likely to encounter in an aircraft accident. Fire duration statistics are frequently biased by the duration of burning of ground structures and other features not related to the aircraft wreckage, as well as by the location of consignments involved in the accident. To account for this effect, information on fire duration was evaluated carefully to avoid bias by accounts of fires that did not involve the aircraft. The fire test has the same characteristics as those specified in para. 728. 

The fire environment within the 25-ft Comer Test has been characterized by heat flux and temperature measure-... 

Hahn J (1991) Environmental effects of the Kuwaiti oil fires. Environ Sci Technol 25 1531-1532... 

Towsend, W., C. Anderson, J. Zook, and G. CowgiU. 1974. Comparison cf Thermally Coated and Uninsulated Rail Tcmk Cars Filled with LPG Subjected to a Fire Environment, U.S. Department of Transport, Report no. FRA-OR8D, 75-32, Washington, DC. 

PVDF powders are not explosive, but the MSDS guidelines for personal protective equipment should be followed. The powder is not removed readily by dry cleaning it should be brushed from dark clothing. Storage of large quantities of PVDF should adhere to local regulations regarding possible hazards in fire environments. 

Cooling ejfect (heat sink effect) flame retardants that decompose in endothermic reactions are able to cool the fire environment and therefore to slow down the reaction pathway. These additives are usually hydrated minerals or metal hydroxide fillers. 

Once the roles, duties, and tasks required have been established the training needs to meet these requirements. For example, a very important training need is the experience of fire, heat and smoke in a confined area similar to a fire environment It is important that key ECO persoimel are not taken by surprise by the fire enviromnent In this way they will be famihar with h, they will be more effective in their duties, and be less likely to panic or act irrationalfy. ECO persoimel should be familiar with - and therefore, trained where necessary - in the following ... 

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