Title of Invention

A FLOODING METHOD FOR SUPPRESSING A FIRE AT A BURNING MATERIAL

Abstract

No.IN/PCT/2002/01248/CHE ABSTRACT A FLOODING METHOD FOR SUPPRESSING A FIRE AT A BURNING MATERIAL A flooding method for suppressing a fire at a burning material comprising delivering to said burning material (a) an inert gas and (b) a gaseous compound, stored as a compressed liquid in a separate container, selected from the group consisting of a hydrofluorocarbon, an iodofluorocarbon, and a mixture thereof, gases (a) and (b) being delivered in a combined concentration sufficient to extinguish the fire wherein the inert gas (a) is delivered to said burning material in a concentration of at least 4.8% v/v, and compound (b) is delivered to said burning material in a concentration of at least 1% v/v.

Full Text

FIELD OF THE INVENTION The present invention relates to a flooding method for suppressing a fire at a burning material. The present invention relates to the field of fire extinguishing compositions and methods for delivering a fire extinguishing composition to or within a protected hazard area. DESCRIPTION OF THE PRIOR ART Certain halogenated hydrocarbons have been employed as fire extinguishants since the early 1900's. Prior to 1945, the three most widely employed halogenated extinguishing agents were carbon tetrachloride, methyl bromide and bromochloromethane. For toxicological reasons, however the use of these agents has been discontinued. Until only recently, the three halogenated fire extinguishing agents in common use were the bromine-containing compounds, Halon 1301 (CF’ Br), Halon 1211(CF2,BrCl) and Halon 2402 (BrCF2,CF2BT). One of the major advantages of these halogenated fire suppression agents over other fire suppression agents such as water or carbon dioxide is the clean nature of their extinguishment. Hence, the halogenated agents have been employed for the protection of computer rooms, electronic data processing facilities, museums and libraries, where the use of water for example can often cause more secondary damage lo the property being protected than the fire itself causes. Although the above named bromine and chlorine-containing compounds are effective fire fighting agents, those agents containing bromine or chlorine are asserted to be capable of the destruction of the earth's protective ozone layer. For example, Halon 1301 has an Ozone Depletion Potential (ODP) rating of 10, and Halon 1211 has an ODP of 3. As a result of concerns over ozone depletion, the production and sale of these agents after January 1. 1994 is prohibited under international and United States policy. It is therefore an object of the present invention to provide a method for extinguishing fires which does not employ bromine or chlorine-containing agents and which does not lead to the depletion of stratospheric ozone. W09315794 recites fire extinguishing methods using gas-liquid mixtures that include at least a basis (e.g., halogenated hydrocarbon and one or both of a dispersing agent (e.g., SF,,, etc.) and/or an inert gas. US patent 5,340,490 is directed toward azeotrope-like mixtures. US patent 3,804,759 describes mixtures of CO2 and halocarbons for use with a handheld fire extinguisher. US patent 5,!4J,654 is directed toward single compositions for use in extinguishing fires with no mentions of combinations with inert gases. These references do not teach or suggest storing a gaseous compound as a compressed liquid in a separate container and delivering this compound with an inert gas at the specified concentrations. These references describe either storing mixtures, or providing single compounds, but not storing compounds as compressed liquids, and then providing a combination of the stored compound and an inert gas to a fire. The use of hydrofluorocarbons fHFCs), for example 1,1,1,2,3,3, 3-heplanuoropropane (CF3CHFCF3), as fire extinguishing agents has been proposed only recently (see for example, M. Robin, "Halogenated Fire Suppression Agents," in Halon Replacements, A. W. Miziolek and W. Tsang, eds., ACS Symposium Series 611, ACS, Washington, DC, 1995). Since the hydrofiuorocarbons do not contain bromine or chlorine, the compounds have no effect on the stratospheric ozone layer and their ODP is zero. As a result, hydrofluorofluorocarbons such as l,l,I,2,3,3,3-heptaf]uoropropan.e and pentafluoroethane(CF_,CF2H) are currently being employed as environmentally friendly replacements for the Halons in fire suppression applications. The bydrofluorocarbon fire suppression agents are not as efficient on a weight basis as the Halon agents and hence increased weights of the hydrofluorocarbon agents are required to protect a given space; in some cases the weight of hydrofluorocarbon agent required is twice that of the Halon agent. A further disadvantage of the hydrofluorocarbon fire suppression agents compared to the Halon agents is their relatively high cost. The relatively high agent cost and lowered efficiency associated with the hydrofluorocarbon fire suppression agents leads to suppression system COSK which are much higher compared to systems employing the Halon agents. It is therefore a author object of the present invention to provide a file suppression method which reduces the moving of hydrofluorocarbon fire suppression agent required for fire suppression, hence reducing the overall cost of the fire suppression system compared to conventional hydrofluorocarbon fire suppression systems. When employed foil titer extiflguishment of very large fires, the hydrofluorocarbon fire suppression agents react in the flame to form various amounts of the decomposition product HF, the relative amounts formed depending on the particular fire scenario. In larger quantities, HF can be corrosive to certain equipment and also poses a threat to personnel. It is therefore a further object of this infixion to provide a method for suppression fire which reduces the amount of decomposition products formed from the hydrofluorocarbon fire suppression agents. In addition to the hydrofiuorocarbon agents, inert gases have been recently proposed as replacements for the Halon file suppression agents (see for example, T. Winsock, "Inert Gas Fire Suppression Systems Using IG541 (INERGEN); Solving the Hydraulic Calculation Problem, "Proceedmgs of the 1996 Halon Options Technical Working Conference. Albuquerque, NM, May 7-9,1996). Pure gases such as nitrogen oi argon, and also blends such as a 50:50 blend of argon and nitrogen have been proposed. The mert gas agents are very inefficient at iire suppression, and as a result vast amouius of the inert gas agent must be employed to provide extinguishment. Typical extinguishing concentrations for inane gas agents range frona 45 to over 50SE by volume, compared lo ranges of 5-10% by volume for hydrofiuorocarbon fire suppression agents. The iarge amounts of agent required in the case of Uie inert gases results in the need for a much larger number of storage vessels conqjared to the case of the hydrofiuorocarbon agents, and as a result large storage areas are required to contain the inert gas system cylinders. For example, in cenainsimations requiring a single cylinder of a hydroflnorocaiboB agent, up to 50 cylinders of an inert gas agem may be required. It is therefore a further object of this invention to provide a method for suppression of fires which reduces the amount of inert &as requured for the suppression of fires, thereby reducing the number of inert gas cylinders required for the protection of a given hazard and reducing the overall cost of the suppressioa system, - A further disadvantage of the inert gas systems is the high enclosure pressure developed during discharge due to the large amounts of gas which must be injected into the protected enclosure. This can lead to structural damage jf the enclosure is not sufficiently vented to allow for leakage and pressure dissipation. It is a therefore a further object of this invention to provide a method for the extinguishment of fires which reduces the amount of inert gas required to extinguish a fire, hence reducing the high pressure development. Due to the large amounts of inert gas required for fire suppression, inert gas systems typically discharge their contents into the protected hazard over a one to two minute period. This compares to the case of the fluorocarbon agents, which, because they require much less gas, employ discharge times of 10 seconds or less. Fu-e extinguishment will not occur until the extinguishing concentration is achieved wilhin the protected enclosure, and hence due to the long discharge times employed with the inert gas agents the fire bums much longer before extinction compared to the case of the fluorocarbon agents. Because the fire bunts longer, increased amounts of combustion products are produced with inert gas systems. This is clearly undesirable as it Is well documented that small amounts of combustion products (e.g. smoke) can cause extensive equipment damage, and many combustion products are loKic lo humans in low cancentratioi’. It is a further object of the present invention to provide a method for the suppression of fires which reduces the extinguishment lime compared to inert gas systems, resulting in reduced amounts of combusiloo products. A further problem associated with the use of inert gas suppression agents is depletion of oxygen within the protected hazard to levels dangerous to hiunans. The amount of oxygen required to sustain human life, and therefore mammalian life, is well known, see for example, Paul Webb, BioastronauticsDataBook, NASASP-3006. NASA, 1964,page5. AtnormaJ atmospheric pressures at sea level, the unimpaired performance zone is in. the range of about 16 to 36 volume percent oxygen. The discharge of the inert gas agents into an enclosure results in oxygen levels significantly below the level of unimpaired performance. For example, at a use level of 50% by volume, a typically employed concentration for inert gas agents, the oxygen within the protected hazard will be reduced to 10.3 % due to dilution of ttie air by the inert gas agent. Further reductions in oxygen will occur due to dilution by the combustion products, resulting in an enclosure environment that is toxic to humans. It is therefore a further object of this invention to provide a method for fire suppression which does not reduce the oxygen in the protected hazard to unsafe levels. It is a further object of the present invention to provide a method for the suppression of fires which requires less inert gas agent and less fluorocarbon fire suppression agent than required with conventional inert gas and fluorocarbon suppression systems, leading to more cost effective fire suppression systems, Further objects of the invention will become apparent from the following description, DESCRIPTION OF THE PREFERRED EMBODIMENTS For the ptirpose of promoting an understanding of the principles of the invention, lefeiente will now te made to pieferred ranbodiments of the invention and specific language will be used to describe the same. It wil! nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations, further modifications and applications of the principles of the invention as described herein being conten’jialed as would normally occur to one skilled in the art to which the invention relates. In accordance with the present invention, it has been found that the use of a hybrid fluorocarbon/inert gas extinguishing system eliminates or significantly reduces the problems described above. In accordance with one embodiment of the present invention, there is provided a raetUod for extinguishing fires which comprises a system consisiiDg of a fluorocarbon fire suppression agent stored in a suitable cylinder, and an inert gas fire suppression agent stored in a second suitable cylinder. Both the fluoTocarbon and inert gas cylinders are connected via the appropriate piping and valves to discharge nozzles located within the hazard being protected. Upon detection of a fire, tbe suppression system is activated, b one embodiment of the invention, the fluorocarbon agent and the inert gas agent aie released from their respective storage cylinders simultaneously, affording delivery of the lluorocarbon and inert gas to the protected hazard at the same time. Typical detection systems, for example smoke detectors, infrared detectors, air sampling detectors, etc. may be en’Ioyed to activate the system, and a delay between detection and agent delivery may be employed if deemed appropriate to the hazard. In a further embodiment of the invention, upon detection of the fire the inert gas agent is delivered to the enclosure first, and the fluorocarbon agent is delivered at a later lime, either during or after the inert gas discharge, depending upon the needs of the particular fire scenario. It should be understood that fire extinguishing using a "flooding" method, as accomplished in accordance with the present invention, provides sufficient exting-iishing agent(s) to flood an entire enclosure or room in which the fire is detected. Assuming perfect mixing of gases in the enclosure, the composition of the gases, including the extinguishing agent(s), at die burning material, is identical to the composition of gases at any other location within the enclosure. However, clearly, it is the composition of gases at the burning material which governs whether a fire can be extinguished and, since the mixing of gases in the enclosure may not be homogeneous early in die extinguishmg process, the appended claims refer to the gas composition "at die burmng material". The fluorocarbon agent may be stored in a conventional fire suppression agent storage cylinder fitted with a dip tube to afford delivery of the agent through a piping system. As it well known and practiced widely throughout the industry, the fluorocarboo agent in the cylinder can be superpressurized with nitrogen or another inert gas, typically to levels of 360 or 600 psig. In the case of lower boiling fluorocarbon agents such as trifiuororaethane (CFjH), the agent can be stored in and delivered from the cylinder without the use of any superpressurization. Alternatively, the fluorocarbon agent can be stored as a pure material in a suitable cylinder to which is conneaed a pressurization system. The fluorocarbon agent is stored as the pure liquefied compressed gas in the storage cylinder under its own equilibrium vapor pressure ai ambient ten’eratures, and upon detection of a fire, the fluorocarbon agent cylinder is pressurized by suitable means, and once pressurized to the desired level, the agent delivery is activated. Such a "piston flow" method for delivering a fire suppression agent to an enclosure, and additional fu'e suppression agents, mcluding perfluorocarbons, and hydrochlorofluorocarbons, useful in accordance widi the present invention, have been described in Robin, et al. U.S. Patent No. 6,112.822. hereby incorporated by reference. Specific fluorocarbon agents useful in accordance with the present invention include compounds selected from the chemical compound classes of the hydrofluorocarbons, and iodofluorocaibons. Specific hydrofluoro-carbons preferred in accordance with the present invention include trifiuoromethane (CFjH), pentafiuoroethane (CFjCFiH), 1,1,1.2-tetra-fluoroethane (CFjCHjF), 1,1,2,2-tetrafluoroethane (HCFjCFjH), l.l,1.2.3,3.3-hepta£hioroprc’ane (CFjCHFCFj), 1,1,1,2,2,3,3-heptafluoro-propane (CFjCFjCFjH). 1,1,1.3.3.3-hexafluoropropane (CFjCHjCF,), l.l,l,2,3,3-hexafluoropropaiie{CF3CHFCFiH),l.l,2,2,3,3-hexafluoropropane (HCFjCFjCFiH), and 1,1,1,2,2,3-hexafluoropropane (CFjCFjCHiF). Specific iodofluorocarbons useful in accordance with the present invention indude CFjI and CFjCF’J. Specific inert gases useful in accordance with the present invention mclude nitrogen, argon, helium, carbon dioxide, and mixtures thereof. Unlike conventional inert gas extinguishing systems, the present invention employs the inert gas not to extinguish the fire, but employs the inert gas al concentralions lower Iban Ihai reqaired for extinguishment. Because the invention employs the inert gas agent for other than extinguishing the fire by itself, the ir’rt gas agent need not he employed at the high concentrations required for extinguisbinent. The use of lower inert gas concentrations reduces the overall system cost as fewer inert gas cylinders are required for protection of the hazard. Since fewer inert gas cylinders are required, less storage space is required to house the cylinders, Because less inert gas agent is discharged into the enclosure, the pressure developed within the enclosure is reduced, and oxygen levels within the enclosure are not reduced to toxic levels. In addition to the above benefits, it has been discovered that the present uavention atfords fire extinguishment at fluorocarbon concentrations unexpectedly lower than that required with conventional fluorocarbon fire suppression sysfnns. This results in significantly lowered overall system costs, as the fluorocarbon agents are expensive and represent the major portion of the cost of a fluorocarbon fire suppression system. The invention will be fiirther described with reference to the following specific Examples. However, it will be understood that these Examples are illustrative and not restrictive in oalure. EXAMPLE 1 The effect of lowered oxygen levels on the concentration of HFC-227ea (1,1.1,2,3.3,3-heptafluoropropane, CFjCHFCFj) required for the extinguishment of n-heptane flaines was exammed in a cup burner apparatus, as described in M. Robin and Thomas F. Rowland, "Development of a Standard Cup Burner Apparanas: NFPA and ISO Standard Methods. 1999 Halon Options Technical Working Conference. April 27-29, 1999, Albuquerque, NM. The cup burner method is a standard method for determining extinguishing concentraiions for gaseous extinguisbanis, and has been adopted in both national and iiuemational Tae suppression standards, for example NFPA 2001 Standard on Clean Agent Fire Extinguishing Systems and ISO 14520: Gaseous Fire-Extinguishing Systems. A mixture of air, nitrogen and HFC-227ea flowed through a 85 mm (ID) Pyrex chimney around a 28 mm (OD) fuel cup. The chimney consisted of a 533 mm length of 85 mm ID glass pipe. The cup had a 45* ground inner edge. A wire mesh screen and a 76 ram (3 inch) layer of 3 ram (OD) glass beads were employed to provide thorough mixuig of air, nitrogen and HFC-227ea. n-Hepiane was gravity fed to the cup burner from a liquid fuel reservoir consisting of a 250 mL separatory funnel mounted on a laboratory jack, which allowed for an adjustable and constant liquid file! level in the cup. The fuel was lit with a propane mini-torch, the chunney was placed on the apparatus, and the air and nitrogen flows initiated. The fiiei level was then adjusted such that the ground inner edge of the cup was completely covered. A 90 second prebuni period was allowed, and the HFC-227ca concentration in the air stream increased in small increments, with a waiting period of 10 seconds between increases in HFC-227ea flow. After flame extinction, the used fuel was drained and the test repeated several times with fresh fuel. Immediately following flame extinction, a sample of the gas stream at a point near the lip of the cup was collected through a length of plastic tubing attached to a Hamilton IL precision gas syringe. The sample was then injected into a IL TEDLAR bag aad subjected to gas chromatographic analysis. Calibration was performed by preparing standards in a IL TEDLAR bag. Results are shown in Table 1. TABLE 1 Extinguishing Concentrations of HFC'227ea And Nj for n-Heptane Flames tun Air Flow Nitrogen Flow HF-227ea Flow %0: HFC-227ca L/min L/min L/min v/v Ext. Cone.. %v/v 1 42.3 0.00 2.89 20.8 6.4 2 42.3 4.17 2.71 18.9 5.5 3 42.3 7.35 2.36 17.7 4.5 4 42.3 10.80 1.75 16.6 3.2 5 423 14.20 1.10 15.6 1.9 6 42.3 17.50 0,61 14.7 I.O 7 42.3 21.60 0.00 13.8 0.0 The results of Table 1 demonsn'ate that flame extinguishment is achieved with lowered amounts of both the inert gas and the hydrofluorocarbon agent compared to conventional inert gas or hydrofluorocarbon suppression systems. Employing HFC-227ea by itself requires 6,4% v/v HFC-227ea for extinguishment; a conventional nitrogen system would require a concentration of 33.8% v/v nitrogen [Run 7: {100)(2I.6)/(21.6 + 42.3)], Employing the combination of an inert gas and a hydrofluorocarbon agent of the present invention, for example under the conditions of Run 4, where the oxygen concentration is reduced to 16.6% v/v, extinguishmeiU is afforded at a nitrogen concentration of 19.7% and an HFC-227ea concentration of 3.2%. Hence the requirements for both nitrogen and HFC-227ea have been reduced by approximately 50%, which would lead to a substantial reduction in overall system cost, while avoiding atmospheric conditions that are hazardous to personnel. Table 2 shows the resulting system requuements for the protection of a 5000 f’ enclosure with a n-heptane fuel bazard. In each case a single cylinder of HFC-227ea would be required. Employmg the combination of an inert gas and a hydrofluorocarbon agent of the present invention, for example under conditions where the oxygen concentration is reduced to 16.6% v/v, the requirements for both nitrogen and HFC-227ea have been reduced by approximately 50% compared to tbe conventional systems, which would lead to a substantial reduction in overall system cost, while avoidmg atmospheric conditions that are hazardous to personnel. TABLE 2 HFC-227ea System Requirements for 5000 ft’ enclosure: Fuel = n-Heptane Desired In endosure %v/v Inert gas required to produce desired %0] Inert gas required. Inert gas, Number of cylinders required* %HFC-227ea required for extinction Weight of HFC-227ea required for extinctiont lb. 20.8 0 0 0 6.4 155 18.9 9.1 479 3 5.5 132 17.7 14.9 907 5 4.5 107 16.6 20.2 1128 6 3.2 75 15.6 25.0 1439 8 1.9 44 14.7 39,3 1736 9 :.o 23 13.8 33.8 2052 11 0 0 * Employing standard inert gas cylinders containing 201 ft' of inert gas. EXAMPLE 2 Example 1 was repeated, employii’ HFC-125 (pentafluoro-ethane, CFjCF’H) as the hydrofluorocarbon agent. Results are shown in Tables 3 and 4, where it can be seen that the use of the present invention leads to reduced requirements of both the inert gas and the hydrofluorocarbon agent compared to conventional systems. TABLE 3 Extinguisliing Concentrations of HFC-12S and Nj for n~Heptane Flames RtID I 2 3 4 5 6 7 Air Flow L/min 42.3 42.3 42.3 42.3 42.3 42.3 42.3 Nitrogen Flow L/min HF-227ea Flow L/min 0,00 4.05 4.17 3.45 7.35 3.00 10.80 2.39 14.20 2.47 17.50 0.85 21.60 0,00 T/T 20.8 18.9 17.7 16.6 15.6 14.7 13-8 HFC-125 Ext. Cone, %V/T 8.7 6.9 5.7 4.3 2.5 1.4 0.0 TABLE 4 HFC-125 System Requirements for 5000 ft* enclosure: Fuel = n-Heptane % v/v Inert Inert gas Inert gas, % HFC-125 Weight of gas required required, Number of required for HFC-125 ft' Desired %0, In enclosure 20.8 18.9 17.7 16.6 15.6 14.7 13.8 to produce desired ftO, 0 9.1 14.9 20.2 25.0 29,3 33.8 0 479 907 1128 1439 1736 2052 cylinders required* 0 3 5 6 8 9 11 extlndton 8,7 6.9 5.7 4.3 2.5 1.4 0.0 required for exltnctiou, ib. 150 117 95 71 40 22 0 * Employing standard inert gas cylinders containing 201 ft’ of inert gas. Analysis of Tables 1 and 3 shows that the extinguishment of these fires is accomplished by delivering to the fne (1) an amount of an inert gas sufficient to reduce the oxygen concentration to a certain level and (2) an amount of a fluorocarbon agent at a concentration sufficient to provide, when combined with the inert gas, extinguishment of the fire. Sufficient inert gas is delivered to reduce the oxygen, at the fire, to a level ranging from about 10% to about 20% v/v oxygen, preferably about 14% to 20% v/v oxygen, and more prefei’bly, to provide an atmosphere in which human activity is unimpaired, from about 16% to about 20% v/v oxygen. Assuniing an ambient oxygen level of 21% v/v oxygen, reduction to 10% to 20% oxygen would require an inert gas concentration of from about 52.4 to 4.8% v/v. Reduction of the oxygen level to 14% to 20% v/v would require aninert gas concentration of from 33.3 to 4.8%. Reduction of the oxygen level to 16 % to 20% v/v would require an inert gas concentration Offrom23.8to4.8%. The concentration of fluorocarbon required for extinguishment depends upon the particular fluorocarbon being employed. For example, from Table 1 it can be seen they in the case of HFC-227ea, the concentration required ranges from about 1% to6.59£ v/v. preferably 1% to 6%, and most preferably from about 3% to 6% v/v. For the case of HFC-125 (Table 3), the concentration of HFC-125 ranges from about 1 % to 8% v/v, preferably 1 % to 7% v/v, and most preferably from about 4% to 8% v/v. WE CLAIM: 1. A flooding method for suppressing a fire at a burning material comprising delivering to said burning material (a) an inert gas and (b) a gaseous compound, stored as a compressed liquid in a separate container, selected from the group consisting of a hydrofluorocarbon, an iodofiuorocarbon, and a mixture thereof, gases (a) and (b) being delivered in a combined concentration sufficient to extinguish the fire, wherein the inert gas (a) is delivered to said burning material in a concentration of at least 4.8% v/v, and compound (b) is delivered to said burning material! in a concentration of at least i % v/v. 2. A method as claimed in claim 1 wherein each gas (a) and (b) is delivered in less than an extinguishing concentration when used alone. 3. A method as claimed in claim 1, wherein gases (a) and (b) are delivered to the burning material in quantities sufficient to reduce an oxygen concentration, at the burning material, to less than 20% v/v. 4. A method as claimed in claim 3, wherein gases (a) and (b) are delivered to the burning material in quantities sufficient to reduce the oxygen concentration, at the burning material, to a range of 16% to 20%i v/v. 5. A method as claimed in claim !, wherein the inert gas is delivered to the burning material in an amount such that the inert gas concentration at the burning material is 52.4% v/v or less. 6. A method as claimed in claim 5, wherein compound (b) is delivered to the burning material in an amount sufficient such that the concentration of compound (b) at the burning material is in the range of 1% to 9% v/v. 7. A method as claimed in claim 1, wherein the inert gas is delivered to the burning material in an amount sufficient such that the concentration of inert gas at the burning material is in the range of 4.S% to 52.4% v/v. 8. A method as claimed in claim 7, wherein the inert gas is devoured to the burning material in an amount sufficient such that the concentration of inert gas at the burning material is \i\ the range of 4.8% to 33.3% v/v. 9. A method as claimed in claim 8, wherein the inert gas is delivered to the burning material in an amount sufficient such that the concentration of inert gas at the burning material is in the range of 4.8% to 23.8% v/v. 10, A method as claimed in claim 9, wherein the inert gas is delivered to the burning material in an amount sufficient such that the concentration of inert gas at the burning material is 9.1% to 29.3% v/v. 11. A method as claimed in claim 1, wherein compound (b) delivered to the burning material is sufficient such that the concentration of compound (b) at the burning material is in the range of 1 % to 9% v/v. 12. A method as claimed in claim 6, wherein compound (b) is delivered to the burning material in an amount sufficient such that the concentration of compound (b) at the burning material is in the range of 1% ten 8% v/v. 13. A method as claimed in claim 12, wherein compound (b) is delivered to the burning material in an amount sufficient such that the concentration of compound (b) at the burning material is in the range of 1% to 6.5% v/v. 14. A method as claimed in claim 12, wherein compound (b) is delivered to the burning material in an amount sufficient such that the concentration of compound (b) at the burning materia] is in the range of 1% to 7% v/v. 15. A method as claimed in claim 12, wherein compound (b) is delivered to the burning material in an amount sufficient such that the concentration of compound (b) at the burning material is in the range of 4% v/v to 8%^ v/v. 16. A method as claimed in claim 1, wherein the concentration of inert gas at said burning materia] is in the range of 4.8% to 52.4% v/v, and the concentration of compound (b) at said burning material is in the range of 1% to 9% v/v. 17. A method as claimed in claim 16, wherein the concentration of inert gas at said burning material is in the range of 4.8% to 33.3% v/v, and the concentration of compound (b) at said burning material is in the range of 3% to S% v/v. 18. A method as claimed in claim 17, wherein the concentration of inert gas at said burning material is in the range of 4.8% to 23.8%) v/v, and the concentration of compound (b) at said burning material is in the range of 3% to 8% v/v. 19. A method as claimed in claim 1, wherein the iodofluorocarbon is CF3I, 20. A method as claimed in claim 1, wherein the inert gas is delivered to the burning material prior to delivering compound (b) to the burning material. 21. A method as claimed in claim 1, wherein compound (b) is delivered to the burning material prior to delivering the inert gas to the burning material.

Documents:

in-pct-2002-1248-che abstract-duplicate.pdf

in-pct-2002-1248-che abstract.pdf

in-pct-2002-1248-che claims-duplicate.pdf

in-pct-2002-1248-che claims.pdf

in-pct-2002-1248-che correspondence-others.pdf

in-pct-2002-1248-che correspondence-po.pdf

in-pct-2002-1248-che description(complete)-duplicate.pdf

in-pct-2002-1248-che description(complete).pdf

in-pct-2002-1248-che form-1.pdf

in-pct-2002-1248-che form-18.pdf

in-pct-2002-1248-che form-26.pdf

in-pct-2002-1248-che form-3.pdf

in-pct-2002-1248-che form-5.pdf

in-pct-2002-1248-che others.pdf

in-pct-2002-1248-che pct.pdf

in-pct-2002-1248-che petition.pdf

in-pct-2002-1248-che-description (complete).tif

in-pct-2002-1248-che-triplicate-claims.pdf

in-pct-2002-1248-che-triplicate-claims.tif