Abstract:
The present invention describes halogenated alkane fire extinguishing compositions consisting essentially of 1,1,1,3,3-pentafluoro propane, optionally pentafluoro ethane, and optionally one or more fire extinguishing fluoro- or chlorfluoroalkanes.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application is related to and claims the priority benefit of U.S. Provisional Application No. 60/323876, which is incorporated herein by reference in its entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention is directed toward fire extinguishing compositions and methods having low ozone depletion potential and low greenhouse gas potential, fire extinguishing characteristics which compare favorably with the use of bromo-chloro-difluoro-methane (a highly efficient fire extinguishing agent which is unsuitable for continued use because of environmental issues).  
         BACKGROUND  
         [0003]    In general, extinguishing agents can be applied to a fire in three manners: 1) directing a stream of a liquid extinguishing agent at the fire (hereinafter, “streaming application”); 2) atomizing a liquid extinguishing agent to produce a “mist” or “fog” of liquid droplets suspended in gas (typically air) and presenting the “fog” to the fire (hereinafter, “fogging application”); and 3) filling an area within which a fire is contained with an extinguishing agent in a gaseous state (hereinafter, “flooding application”). Flooding application can be carried out by vaporizing a fire extinguishing agent to uniformly occupy the entirety of an enclosed space in which the fire is contained (total flooding) or by moving a body of the material in the form of a gas cloud over the region in which the fire is burning, suffocating the fire.  
           [0004]    Application of fire extinguishing agent compositions comprising alkanes which have some or all of their hydrogen atoms replaced with halogens (hereinafter “halo-alkanes”, certain subgenus groupings of which are also known in various industries as “Halons” and “Freons”) is generally limited to flooding or streaming. Examples of these include, for streaming application, bromo-chloro-difluoro-methane (Br(Cl)CF 2 ), and for flooding application, bromo-trirluoromethane (BrCF 3 ).  
           [0005]    Halo-alkanes used as fire extinguishing agents may exhibit a fire extinguishing effect through: (a) removal of heat energy from a fire (cooling below a level required to sustain combustion); (b) separating oxygen and fuel through blanketing the fuel (smothering); and (c) decomposition of the extinguishing agent generating fragments which effectively terminate the chemical processes sustaining combustion. Various of the halo-alkanes exhibit one or more of these properties when applied to a fire. The method by which the extinguishing agent is applied to a fire has bearing on the degree to which it is important that the extinguishing agent exhibits these fire extinguishing processes.  
           [0006]    In flooding applications, the fire extinguishing agent must be volatile in all ambient conditions in which the agent is used to insure that the space in which it is deployed contains sufficient concentration of the fire extinguishing agent to suppress the fire, thus, vapor phase heat capacity and flame suffocating ability are important aspects associated with a flooding agent. Secondarily, the ability of a flooding agent to decompose and disrupt the chemical process involved in combustion is also important.  
           [0007]    In streaming applications, the fire extinguishing agent is presented to the fire as a liquid. In such applications, a high value of liquid to vapor phase heat absorption (heat of evaporation) becomes important, as well as the vapor phase heat capacity. Of additional importance in fire extinguishing agents used in streaming applications is the volatility of the liquid. While high heat absorption in changing phase is desirable, a streaming agent which is not sufficiently volatile to provide a large volume of smothering gas upon application to the fire will not readily “knock down” the flame front of the fire, making it less efficient in extinguishing the fire.  
           [0008]    Fogging agents, which are suspended droplets of a liquid extinguishing agent in a gas, usually air, typically have very high liquid to gas phase change heat of evaporation and low volatility. An example of a good fogging agent is water.  
           [0009]    Typically, fire extinguishing agent compositions based on halo-alkanes have heretofore been formulated for application as a flooding or streaming agent, and not for fog application. Among the halo-alkane fire extinguishing agent compositions known, one that has long been known in the art as having superior performance in streaming application is bromo-chloro-difluoromethane (Br(Cl)CF 2 ). Br(Cl)CF 2  is toxic to humans, and therefore is not used in flooding applications. Even though it is a less efficient fire extinguishing agent, bromo-trifluoromethane (BrCF 3 ), which is non-toxic, is used in flooding applications instead of bromo-chloro-difluoromethane.  
           [0010]    The use of various halo-alkanes in applications in which they enter the atmosphere has raised international concern with regard to the ability of these materials to contribute to destruction of ozone in the upper atmosphere and with regard to the ability of these gases to also function as “greenhouse” gasses. This concern has created a need for compositions which exhibit flood and streaming fire extinguishing agent properties similar to BrClCF 2  and BrCF 3  (hereinafter, “the halo-methanes”) identified above, but which do not posses the negative environmental impact associated with those materials.  
           [0011]    A class of compounds, halo-alkanes of 4 or fewer carbon atoms, have been identified as having sufficient volatility and heat capacity for use in fire extinguishing agent compositions and may be candidates for replacing the above-identified halo-methane compounds by virtue of their low ozone depletion potential and low potential as greenhouse gasses.  
           [0012]    One such compound is 1,1,1,2,3,3,3 heptafluoro-propane. When used as a fire extinguishing agent it is not as efficient as the halo-methanes it replaces due to its lower volume of smothering vapor. Another compound, pentafluoroethane, offers better smothering vapor than the heptafluoro-propane and is believed to also readily breakdown in the environment, thus it has potential to replace bromotrifluoro-methane (BrCF 3 ) as an extinguishing agent in flood applications. Pentafluoroethane compares favorably with bromotrifluoro-methane, based on a comparison of the vapor phase heat capacity and ability to deliver a volume of blanketing gas. This implies that pentafluoroethane is a good candidate for use as a fire extinguishing agent. However, when pentafluoroethane is used by itself as an extinguishing agent in a flood application, it is less efficient than the bromotrifluoro-methane it replaces, thus applicants perceive a continuing need for a replacement with improved efficiency.  
           [0013]    It has been suggested (see, U.S. Pat. No. 5,124,053 to Yuichi et al.), that blending various fluoro-alkanes can take advantage of the various indidividual properties of the fluoro-alkanes and produce compositions which are similar to the properties of the halo-methanes described above, providing a more suitable fire extinguishing agent composition for replacing them. Examples of such compositions include compositions described in published PCT application WO 93/17758, TAG Investments, Inc., applicants, (hereinafter, “the &#39;758 application”), which describes two fire extinguishing compositions for flood applications. A first composition is generically described comprising one or more fluoro- or chlorofluorcarbon compounds of up to 4 carbon atoms. A second composition is described as containing one or more fluoro- or chlorofluoro carbon compounds from a list naming about 40 such compounds. Pentafluoroethane is encompassed within this list. However, pentafluoroethane alone is unsuitable for use as a fire extinguishing agent in streaming applications. Because of its low boiling point, when pentafluoroethane is applied as a stream it disperses before it reaches the fire, making it unsuitable for use out-of-doors. All of the compositions described in the &#39;758 application also include from about 0.1 to about 10 wt. % of an acid scavenging compound of the type further described below.  
           [0014]    U.S. Pat. Nos. 5,393,438 and 5,141,654, both to Fernandez, (hereinafter, “the &#39;438 patent” and “the &#39;654 patent”, respectively) both describe fire extinguishing agent compositions, which are adaptable for use in flooding applications and which comprise pentafluoroethane or a mixture of pentafluoroethane and one or more propane compounds selected from a list comprising chloro-flouoropropanes, hexa- and heptafluoropropanes. Neither of the &#39;438 patent nor the &#39;654 patent describes the use of these compositions as streaming or fogging agents.  
           [0015]    Published PCT application WO 95/26218 describes fire extinguishing agent compositions for use as flooding agents which comprise one or more fluorocarbon compounds of the formula C x H y F z , where “x”=an integer and “y+z”=“2x+2”, and an acid scavenging compound comprising terpenes, unsaturated oils, and alkali metal compounds of bicarbonate, phosphate, halide, and urea. These compositions are described as being suitable for use as total flooding agents. This publication does not describe a fire extinguishing agent suitable for streaming or fogging applications, nor does it mention or suggest the use of 1,1,1,3,3 pentafluoropropane alone or in combination with pentafluoroethane.  
           [0016]    Applicants have come to appreciate the need for an improved method of extinguishing a fire in situations where there is no “line of sight” between the source of the fire extinguishing agent and the fire, such as where the fire is in a confined space or under a cover or cowl. It has been heretofor common to use a flooding method in such situations. Compositions which are sufficiently volatile to be employed as a flooding agent have heretofore been unsuitable for application as streaming or fogging fire extinguishing agents. This is because flooding agents and methods have been designed to vaporize the agent to the gas phase before application to the fire, whereas streaming and fogging agents must be applied to the situs of the fire as a liquid in order to taking advantage of the heat capacity involved in converting the liquid to a gas.  
           [0017]    Applicants have come to recognize that heretofor used streaming agents, as discussed above, suffer from the relative inability to provide sufficient suffocating volume after application to the fire, which generally requires relatively high volatility, while at the same time being of sufficiently low volatility to avoid dissipation of the liquid prior to contact with the situs of the fire.  
         SUMMARY OF THE INVENTION  
         [0018]    Applicants have discovered compositions which tend to overcome some or all of the above-noted disadvantages of the prior art, and others which are not mentioned above.  
           [0019]    One aspect of the present invention involves a method of extinguishing a fire comprising providing a fire extinguishing agent comprising pentafluoropropane and optionally pentafluoroethane, generating a fog of said fire extinguishing agent and introducing said fog to the fire. In preferred embodiments, the methods comprise introducing said fog to the fire by releasing the fog from a location that not in the line of sight of the fire.  
           [0020]    Although applicants do not wish to necessarily be bound by or to any particular theory of operation, it is believed that 1,1,1,3,3-pentafluoropropane has excellent performance as a replacement for bromochlorodifluoromethane (BrClCF 2 ) in streaming applications because at temperatures above 412° C. it displays facile decomposition. It is believed that this decomposition property gives 1,1,1,3,3-pentafluoropropane an exceptional ability to readily participate in free radical scavenging when exposed to a fire.  
           [0021]    Applicants have also discovered that, in certain applications, the use of 1,1,1,3,3-pentafluoropropane can be further improved by the addition of pentafluoroethane to the composition. Although it has similar heat capacity to bromochlorodifluoromethane, when 1,1,1,3,3-pentafluoropropane is applied to a fire it may not always produce as much smothering vapor as the halomethane. In such situations, it may provides adequate cooling to extinguish a fire, but may not exhibit rapid flame front “knock down” properties (fire smothering ability) comparable to halomethane. The use of pentafluoroethane and 1,1,1,3,3-pentafluoropropane together in the present compositions provides a fire extinguishing agent which in many cases is comparable to or exceeds the fire extinguishing efficacy of halomethane.  
           [0022]    One aspect of the present invention provides a fire extinguishing agent comprising, and preferably consisting essentially of, pentafluoroethane and pentafluoropropane, preferably 1,1,1,3,3-pentafluoropropane. In certain preferred embodiments, 1,1,1,3,3-pentafluoropropane is present in the composition in amount of at least about 20 wt. % of the composition. In other embodiments, the composition comprises at least about 6 wt % pentafluoroethane. Preferably, the composition comprises at least about 6 wt % pentafluoroethane and at least about 20 wt. % of 1,1,1,3,3-pentafluoropropane.  
           [0023]    Compositions of the present invention can optionally contain up to about 10 wt. % additional of a hydrogen fluoride (“HF”) scavenging agent. Preferably when an HF scavenging agent is employed it is comprises from about 2 wt % and about 10 wt % of the composition.  
           [0024]    Another aspect of the present invention is the provision of a fire extinguishing agent in the form of a fog made from a composition comprising, and preferably consisting essentially of, pentafluoroethane and from about 1 wt % 1,1,1,3,3-pentafluoropropane to about 80 wt. % 1,1,1,3,3-pentafluoropropane.  
           [0025]    Another aspect of the present invention is the provision of a fire extinguishing agent in the form of a stream made from a composition comprising, and preferably consisting essentially of, pentafluoroethane and from about 45 wt. % to about 94 wt. %, and even more preferably from about 64 wt % to about 94 wt. %, of 1,1,1,3,3-pentafluoropropane. According certain preferred embodiments, the fire extinguishing stream of the present invention is formed using a composition comprising from about 20 wt. % to about 36 wt. % of pentafluoroethane and at least about 45 wt. %, of 1,1,1,3,3-pentafluoropropane.  
           [0026]    Another aspect of the present invention is the provision of a method of extinguishing a fire by providing a fire extinguishing composition of the present invention to a fire as a stream of fire extinguishing agent comprising 1,1,1,3,3-pentafluoro propane and pentafluoroethane wherein the 1,1,1,3,3-pentafluoropropane is present in amount of at least about 45 wt. % of the composition and the pentafluoroethane is present to a level of at least 6 wt. % of the composition.  
           [0027]    Optionally, the stream application fire extinguishing composition can contain up to about 10 wt. % additional of an HF scavenging agent. Preferably, when an HF scavenging component is employed it is added to the composition to a level of between about 2 wt. % and about 10 wt. % additional.  
           [0028]    Another aspect of the present development is the provision of a method of extinguishing a fire by providing the fire extinguishing composition of the present development to a fire as a fog of fire extinguishing agent comprising a mixture of 1,1,1,3,3-pentafluoro propane and pentafluoroethane wherein the pentafluoropropane is present to a level of at least 1 wt. % of the composition and the pentafluoroethane is present to a level of at least 20 wt. % of the composition.  
           [0029]    Optionally, the fog application fire extinguishing agent can have up to about 10 wt % additional of an HF scavenging agent.  
           [0030]    Other features of the present invention will be pointed out in the following description and claims, which disclose but do not necessarily limit the broad aspects of the present invention, the principles of the invention.  
           [0031]    In certain preferred embodiments, the present compositions do not contain fire extinguishing amounts of any compounds that are completely fluorinated and/or any compounds that contain chlorine. Preferably in such embodiments, the present compositions do not contain any substantial amount of, and even more preferably are substantially free of, any compounds that are completely fluorinated and/or any compounds that contain chlorine. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     Defintions  
       [0032]    Effectiveness in extinguishing fires is measured by the amount of an agent required to extinguish a standard fire within a specified time. Such tests can be performed using, for example, a cup burner or other extinguishing concentration measurement. A recitation of this method as a standard test of effectiveness can be found in the 2000 edition of “NFPA 2001 Standard on Clean Agent Fire Extinguishing Systems” Appendix B Cup Burner Test Procedure.  
         [0033]    Efficiency is measured by the speed with which the flame front of a standard fire is “knocked down” upon commencing the application of an extinguishing agent, and the amount of extinguishing agent that is required to be applied to the site to extinguish a standard fire. Efficiency can be quantified using either UL testing standard 2166 or the standard cup burner test described above.  
         [0034]    As the term is used herein, alkanes having a majority of the hydrogens replaced with fluorine (hereinafter “highly fluorinated” alkanes) and those with all of the hydrogen replaced by fluorine (hereinafter “completely fluorinated” or “perfluorinated”-alkanes) are those surmised to be not as likely to participate in ozone destruction as the analogous chloro, chloro/fluoro, and bromo compounds. The stability of these materials, however, raises concerns that their presence in the atmosphere can impede re-radiation of heat from the earth, leading to global warming. For this reason, highly fluorine substituted and perfluorinated alkanes have been implicated as greenhouse gases. Less highly fluorine substituted alkanes (hereinafter “partially fluorinated”) are those that are thought to be subject to more facile breakdown in the environment, and therefore have a lesser global warming potential.  
       Compostions of the Present Development  
       [0035]    As discussed above, pentafluoroethane and 1,1,1,3,3-pentafluoropropane are “partially fluorinated” fluoro-alkanes which have been identified as potential replacements for the halo-methane fire extinguishing agents described above. When a fire is small, 1,1,1,3,3-pentafluoropropane may be used by itself as a replacement streaming agent for bromochlorodifluoromethane, or with other halogenated alkanes having similar physical characteristics. In applications where chlorinated materials may be tolerated various fluoro- or chloro-/fluoro-alkanes may be substituted for or used in addition to pentafluoroethane to yield desirable fire extinguishing compositions. Thus, alternative or additional low and high boiling fluoro and chloro fluoro alkanes may be blended with 1,1,1,3,3 pentafluoropropane to provide for fire extinguishing agent compositions which may be used in stream or mist applications. Examples include, but are not limited to HC(Cl)F 2  (HCFC-22), HCF 3  (HFC-23), F 3 C—(H)CCl 2  (HCFC-123), F 2 C(Cl)—(H)C(F)Cl (HCFC-123a), Cl 2  C(F)—(H)CF 2  (HCFC-123b), F 3 C—(H)C(F)Cl (R124), F 2 C(Cl)—(H)CF 2  (R124a), F 2 C(H)—CF 2  (R134), F 3 C—(F)CH 2  (R134a), H(F)C(Cl)—(H)C(F)Cl (HCFC 132), F 3 C—(H)C(F)—CF 3  (HFC-227ea), F 2 C(H)—C(F 2 )—CF 3  (HFC-227ca), F 3 C—C(H 2 )—CF 3 ,(HFC-236fa), F 2 C(H)—(H)C(F)—CF 3  (HFC-236ea), H 2 C(F)—(CF 2 )—CF 3  (HFC-236cb), F 2 C(H)—C(H 2 )—CF 3  (HFC-245fa), F 2 C(H)—(H)C(F)—(H)CF 2  (HFC-245ea), H 2 C(F)—(H)C(F)—CF 3  (HFC-245eb), H 3 C—C(F 2 )—CF 3  (HFC-245cb), ICF 3 .  
         [0036]    As described above, where fire extinguishing efficiency in a fire extinguishing agent is required, for example, in fighting large fire, use of 1,1,1,3,3-pentafluoropropane or pentafluoro ethane alone has not proved to be a fully adequate replacement in all applications, and blends containing either of these materials suitable for streaming and fogging application in fighting fires have not been heretofore identified.  
         [0037]    It has now been found, surprisingly, that by combining, preferably to a substantially homogenous mixture or blend, pentafluoroethane with 1,1,1,3,3 pentafluoropropane, the efficiency of the resulting composition when used as a streaming application fire extinguishing agent is improved to the point where it compares favorably with bromo-chloro-difluoro-methane in many applications.  
         [0038]    Without wanting to be bound by theory, it is believed that the improvement in the performance of the pentafluoropropane/pentafluoroethane combinations over pentafluoropropane alone is due to the low boiling component supplying a sufficient volume of a gas that has good smothering properties and sufficient heat capacity to impart rapid “knockdown” of the flame front, while providing a sufficient heat capacity between the gas phase component and liquid phase component dispersed as fine droplets therein that the blend retains adequate cooling properties as well. A blend made from pentafluoroethane and 1,1,1,3,3-pentafluoropropane is especially desirable because incorporation of the low boiling pentafluoroethane provides a vapor pressure to the composition that is sufficient to propel the liquid from a storage container in a stream application mode without the use of an additional propellant charge, although typically, a super pressure of gas, for example nitrogen, can also be used for this purpose.  
         [0039]    Preferred blends of pentafluoroethane and 1,1,1,3,3-pentafluoropropane have a boiling range (defined as the “bubble point” to “dew point” of the material measured, as detailed in  Experimental Thermodynamics Volume II , Edtors B. Le Neindre and B. Vodar (1975), page 780) that includes the boiling point of bromochlorodifluoromethane (−4° C.). Thus, a blend of 6 wt. % pentafluoroethane and 94 wt. % 1,1,1,3,3-pentafluoropropane exhibits a −4° C. “bubble point” and a blend of 55 wt % pentafluoroethane/45 wt. % 1,1,1,3,3-pentafluoropropane exhibits a −4°C. “dew point”. Blends comprising 44 wt. % 1,1,1,3,3-pentafluoropropane with the balance consisting of pentafluoroethane have also been found to exhibit a −4° C. “bubble point”. This similarity of physical properties indicates that such blends may be adequate to replace the halogenated methane now used in streaming applications.  
         [0040]    Additionally, blends consisting essentially of pentafluoroethane and 1,1,1,3,3-pentafluoropropane having between 74 and 94 wt. % of the pentafluoropropane can be made that have the same or greater ability to remove heat from a fire that is exhibited by a streaming agent currently used to replace bromochlorodifluoromethane, 1,1 dichloro-2,2,2 trifluoroethane. An example of such a blend comprises 23 wt % pentafluoro-ethane and 77 wt. % 1,1,1,3,3-pentafluoropropane.  
         [0041]    It has been additionally found that blends of the pentafluoroethane and 1,1,1,3,3-pentafluoropropane can be employed as a suspension of droplets, for example a fog or a mist, hereinafter “a fog dispersion”, produced using conventional equipment typically employed to deliver water as a fog in air dispersion. It has been suprisingly found that this type of a fog dispersion has “flood agent-like” characteristics which can be used to extinguish fires in situations where a flood application of the fire extinguishing agent is used.  
         [0042]    Blends consisting essentially of pentafluoroethane and 1,1,1,3,3-pentafluoropropane that make good candidates for such fogging application extinguishing agents have pentafluoroethane present in an amount between about 20 wt. % to about 99 wt. %. Fire extinguishing fog dispersions of these blends have been found to have the same heat capacity as heptafluoropropane when used as an extinguishing agent in flood applications. Additionally, they have the same efficiency as that demonstrated by flood application of the bromodichlorofluoromethane. As well, it will be appreciated by one of ordinary skill in the art that fogs of the blend of pentafluoroethane and 1,1,1,3,3-pentafluoropropane can be employed to extinguish enclosed fires, and as well, passed through labyrinthian passageways in the same manner that single molecule flood agents are employed. As well, it will be appreciated that these fog dispersions can afford improved efficiency in fire extinguishment over the single molecule compounds previously used to replace bromotrifluoromethane in such applications.  
         [0043]    It is known that when hydrogen and fluorine atoms are present in the same molecule (as in the case of partially or highly fluorinated alkanes), the compounds tend to generate HF upon decomposition. HF is highly corrosive to materials and represents a danger to humans occupying the air space where it is present. Copious HF generation is particularly acute in compounds that have a high ratio of hydrogen to fluorine. In fire extinguishing agent compositions employing such fluoroalkanes, a scavenger of HF is included in the formulation. This permits the use of such materials as components in fire extinguishing agents employed in confined space occupied by humans, or in the presence of equipment or material which is damaged by the corrosive effects of HF. Acid scavenging molecules are easily included in fire extinguishing agent compositions. In this manner they are delivered to a fire along with the fire suppressing components, and so their presence at the point of HF generation is insured. Suitable acid scavenging compounds for use in both streaming and flooding agents are, for example, disclosed in published patent applications WO 93/17758 and WO 95/26218 and U.S. Pat. No. 4,954,271 to Green.  
         [0044]    Extinguishing agent compositions of the present invention may also incorporate an effective amount of an HF scavenging agent in their formulation to mitigate problems caused by the HF generated when fluoroalkanes of the present invention compositions are heated in the process of extinguishing a fire. Examples of agents known to have HF scavenging properties are beta-carotene, citral, citronellol, citronnellal, para-cymeme, camphor, lanosterol, limonene, lutein, lycopene, menthadiene, menthol, myrcene, ocimene, oleanolic, dipentene, alpha-pinene, beta-pinene, phytol, sabinene, saponin, squalene, sylvestrene, terpinene, alpha-terpineol, terpinolene, turpentine, vitamin A, zingiberene, oleic acid, eleostearic acid, palmitoleic acid, linoleic acid, lincanic acid, petroselenic acid, abietic acid, linolenic acid, ricinoleic acid, vaccenic acid. Additional examples may be found as well in U.S. Pat. No. 4,954,271 to Green and in published PCT applications WO95/26218 and WO 93/17758, the disclosures of which are incorporated herein by reference. It will be appreciated by one skilled in the art that mixtures of the various acid scavenging compounds may additionally be used to scavenge HF generated during extinguishment of a fire.  
         [0045]    Generally, acid scavenging compounds are added to the fire extinguishing composition in an amount between about 0.1 and 10 wt % of the composition. Preferably, they are added in an amount that is between about 2.0 wt % to about 10 wt. % of the fire extinguishing composition.  
         [0046]    Preparation of Fire Extinguishing Agent Compositions  
         [0047]    The compositions of the present invention may be prepared by mixing the components in a sealed vessel, starting with the least volatile component first, in a manner familiar to those skilled in blending condensible gas. Thus, for example, a composition comprising 10 wt % of an acid scavenging component, 80 wt. % of 1,1,1,3,3-pentafluoropropane, and 10 wt % of pentafluoroethane will be prepared by first placing a weight of the acid scavenging component into a sealed gas cylinder, condensing a weight of 1,1,1,3,3-pentafluoropropane into the cylinder eight times as much as the weight of acid scavenging component initially charged, followed by condensing into the gas cylinder a weight of pentafluoroethane equal to the weight of the acid scavenging component initially charged into the cylinder. The mixture can then be left to statically blend, or be dynamically blended by rolling or otherwise agitating the cylinder.  
         [0048]    It will be appreciated that other known means of blending volatile liquids and of blending liquid and condensible gas components may be equally effective in preparing compositions of the present invention.  
       EXAMPLES  
       [0049]    Calculations modeling the discharge behavior of extinguishing agent compositions comprising a blend of 1,1,1,3,3-pentafluoropropane with pentafluoroethane present in amounts varied between 0 and 55 mole % were studied. In a typical determination, an amount of the composition is assumed to be discharged from a container using a driving pressure of 600 psig to drive the discharge. The calculations were carried out by assuming an amount of the composition in a sealed vessel equilibrated to the ambient temperature. Further, it is assumed that the composition is then released from the vessel under the force of the driving pressure through a standard orifice developing a directed stream. During discharge, the composition and temperature of the stream and vapor of the discharged material were calculated based on adiabatic expansion of the material. This determination was carried out for eight example blends, with the results listed below in Table 1.  
                                                                           TABLE 1                                           Mole %               Mole %   Pentafluoroethane in           Pentafluoroethane   discharged agent                Example #   (before discharge)   liquid   vapor                            A   0   0.0   0.0           B   10   3.8   39.4           C   20   7.1   58.8           D   30   11.0   71.7           E   45   19.3   84.4           F   50   23.1   87.4           G   52   24.8   88.5           H   55   27.6   89.9                      
 
         [0050]    Inspection of the data in Table 1 shows that increasing the percentage of low boiling constituents increases the amount of low boiling constituent comprising the vapor to a greater degree than it increases the presence of the low boiling constituent in the liquid discharged.  
         [0051]    During these discharge tests, the volume of the vapor discharged with the stream was calculated, and the heat of vaporization of a liquid having the composition of the discharged stream was calculated in each case. In each case, the calculated volume of vapor discharged represents the relative amount of suffocant available from each composition. Heat removal calculations were performed by assuming a final vapor temperature of 412° C., the auto ignition temperature of 1,1,1,3,3-pentafluoropropane. At or above the autoignition temperature, decomposition of the pentafluoropropane is facile, and radical scavenging by the decomposition products will become significant in the process of extinguishing a fire to which such a composition is directed. These results are presented below in Table 2.  
                                                     TABLE 2                           Mole %   Heat       Temp.           pentafluoroethane   Removed*   Smothering   discharged       Exp. #   (initial composition)   (kj/kg mole)   volume**   stream (° C.)                                A   0   84098   12.4   15       B   10   81952   29.9   3.6       C   20   79842   43.5   −4.3       D   30   77765   55.4   −12.3       E   45   74710   71.1   −22.3       F   50   73706   75.6   −24.5       G   52   73307   77.3   −25.7       H   55   72710   79.6   −27.6                                  
 
         [0052]    It can be seen that as the pentafluoroethane content of the liquid is increased, the heat removal ability of the composition decreases and the smothering volume produced by the composition increases monotonically with the increase in pentafluoroethane content.  
         [0053]    The heat capacity and smothering behavior of compositions of the present invention fire extinguishing agent, as reported in Tables 1 and 2, can be compared with those of a prior art flooding agent (1,1,1,2,3,3,3 heptafluoropropane) and with a prior art streaming agent (1,1 dichloro, 2,2,2 trifluoroethane). The flooding agent is known to produce a smothering volume of 47.1 ml/g. The streaming agent is known to remove 76649 kilojoules/kg-mole when it is converted from a liquid to a 412° C. gas. By choosing a composition comprising between about 20 wt. % to about 36 wt. % pentafluoroethane and the balance substantially 1,1,1,3,3 pentafluoropropane, the smothering capability of the flooding agent and the heat capacity of the streaming agent can be achieved in a single composition. A composition within this range can then be used either in a stream application, or dispersed in a fog application and employed as a flooding agent, depending upon the equipment from which it is discharged.  
         [0054]    Cup Burner Tests of Various Compositions  
         [0055]    Comprising 1,1,1,3,3 Pentafluoropropane and Pentafluoroethane.  
         [0056]    Cup burner tests were run according to testing protocol listed in the 2000 edition of “NFPA 2001 Standard on Clean Agent Fire Extinguishing Systems” Appendix B “Cup Burner Test Procedure” using binary blends of pentafluoroethane (hereinafter, “R125”) and 1,1,1,3,3 pentafluoropropane (hereinafter, “R245fa”) as an extinguishing agent. The fluoroalkanes from which the blends were made were sourced from Honeywell. They had a purity exceeding 99.5%, and were used as received. The volumetric ratio of the two components comprising the extinguishing agent was varied by varying the flow rate of the two constituents admitted in gaseous form into the air stream of the cup burner apparatus. The flow rate of the various components was controlled using an Environics® gas mixer equipped with flow meters calibrated for the gasses used.  
         [0057]    Initially, the cup-burner apparatus was calibrated using pure R125 as an extinguishing agent. In this manner it was determined that an air stream flow rate of 25 l/min required the highest volume percent (8.4 Vol. %) of R125 to be introduced into the air stream to extinguish the test flame, and this flow rate of burner air was employed throughout the tests. Cup-burner tests were repeated using 25 l/min of air stream flow into which was introduced a fire extinguishing agent comprising 0, 2.4, 4.8, 7.0, 9.1, 10.5, 11.3, 13.3, 15.5, 15.7, 17.6, 18.7, 19.8, 20.3, 27.1, 31.0, 35.0, 41.6, 48.4, and 62.5 Vol. % R245fa with the balance of extinguishing agent volume comprising R125. The amount of this blended extinguishing agent which had to be introduced into the burner air stream to extinguish the test flame (expressed as a volume percent of the extinguishing agent in the air stream) is presented graphically in FIG. 1 for each blend tested.  
         [0058]    [0058]FIG. 1 presents three traces, a base line trace, a trace of the above-described test data, and a trace of “no-effect blend” data, further described below. The test data trace of FIG. 1 is in the form of a black diamond located at the value (in volume % of burner air) recorded for each extinguishing agent composition tested (described above), the base line trace is a line comprising alternating long and short dashed, and the “no-effect blend” trace is a dotted line.  
         [0059]    The base line of FIG. 1, a horizontal line at 8.4 Vol % of extinguisher composition in the burner air stream, is the amount of pure R125, expressed as Vol. % of the burner air stream, required to extinguish the test flame, as described above.  
         [0060]    The “no-effect blend” trace, the upper-most curve of FIG. 1, is based on the notion that a composition comprising a diluent having no fire extinguishing properties and R125 would be effective in extinguishing the cup burner flame when a sufficient volume percent of the composition was introduced into the burner air stream that the R125 present therein accounted for 8.4 Vol. % of the cup burner air stream. To generate the “no-effect blend” data, a theoretical binary blend comprising R125 and a diluent having no fire extinguishing properties was postulated. For any given ratio of R125 and diluent, the volume percent of the “no-effect blend” indicated as adequate to extinguish the burner flame is that amount (expressed as a volume percentage of the burner air stream) which would be required of the given indicated composition to be introduced into the burner air stream to provide burner air containing 8.4 Vol % of R125.  
         [0061]    The test data trace, the middle trace in FIG. 1, is indicated by a series of black diamonds located at the amount of composition (in vol. % of burner air) of the various binary extinguishing agent blends tested, as described above. This trace indicates that the extinguishing agent “blends” of the present invention perform significantly better than the theoretical “no effect” binary blends described above. This data also indicates that pure R125 vapor alone is a more efficient extinguishing agent than the vapor of an R125/R245fa blend.  
         [0062]    It will be appreciated that the cup burner test does not take into account that the physical characteristics of pure R125, as described above, which make it unsuitable for use as a fire extinguishing agent in the form of a “stream” or “fog”, and as such the test can not indicate its suitablity for use as a “streaming” or “fogging” agent. As described above, the fire extinguishing agent comprising a blend of R245fa and R125 of the present invention are intended to replace those used in streaming application (a fire extinguishing agent in the form of a stream) or as a dispersion of liquid droplets (a fire extinguishing agent in the form of a fog). Thus, when the unsuitablity of R125 alone is taken into account, and in consideration of the data presented in FIG. 1 and Tables 1 and 2 above, it is clear that blends of R125 and R245fa provide an effective fire extinguishing agent which has the physical properties suitable for use in fogging or streaming applications.  
         [0063]    As an added benefit, the blended compositions display vapor pressures of up to about 165 psig when contained at ambient temperature. Thus, present invention compositions may be charged into standard fire extinguishing equipment, and discharged therefrom using standard propellant systems.  
         [0064]    A preferred fire extinguishing agent in the form of a stream which has superior fire extinguishing properties from the standpoint of rapid “knockdown” of flame and good cooling and smothering characteristics when the stream is applied to a fire is made from a composition having between 0 and about 55 wt. % pentafluoroethane with the balance substantially consisting of 1,1,1,3,3-pentafluoropropane. Even more preferred is a stream made from a composition having from about 20 wt. % to about 36 wt. % pentafluoroethane with the balance substantially consisting of 1,1,1,3,3-pentafluoropropane.  
         [0065]    A preferred fire extinguishing agent in the form of a fog which exhibits rapid “knockdown” of the flame front and possesses good cooling and smothering characteristics when the dispersion is applied to a fire is made from a composition having more than about 20 wt % pentafluoroethane with the balance substantially consisting of 1,1,1,3,3-pentafluoropropane.