WO1997039805A1

WO1997039805A1 - Environmentally benign non-toxic fire flooding agents

Info

Publication number: WO1997039805A1
Application number: PCT/CA1997/000267
Authority: WO
Inventors: Elio F. Guglielmi; Lorne D. Macgregor
Original assignee: Tag Investments Inc.
Priority date: 1996-04-22
Filing date: 1997-04-22
Publication date: 1997-10-30
Also published as: AU2563097A; CA2180586C; CA2180586A1; CN1221354A; KR100359394B1; CA2252843A1; KR20000010579A

Abstract

Fire flooding and extinguishing agents and detoxifiers which are environmentally safe and non-toxic in both natural form and in fire exposed degraded forms are disclosed. The flooding and streaming-type fire extinguishing agents are rich in low boiling, unsaturated halocarbon compounds having low liquid viscosities, and low boiling alkenes as detoxifying agents. The detoxifiers are conjugated double bond hydrocarbons.

Description

ENVIRONMENTALLY BENIGN NON-TOXIC

FIRE FLOODING AGENTS

FIELD OF THE INVENTION This invention involves novel total flooding and streaming-type fire extinguishants and novel detoxifiers which are environmentally safe and non-toxic in natural form as well as fire exposed degraded forms.

DESCRIPTION OF THE PRIOR ART

In recent years, it has been discovered that certain halocarbons such as CFC 11, CFC 12, Halon 1301, and the like, which have been widely used as refrigerants, blowing agents and fire extinguishants are damaging to the environment because they accumulate in the stratosphere and damage the integrity of the ozone layer, which protects life on earth from harmful radiation from the sun and space. These harmful substances are being phased out of production. Halocarbons have been used as fire extinguishants. Thacker, U.K. 1,603,867, discloses CFC 11 and CFC 12 in combination with a monoterpene, that is, an essential oil or citrous oil, as a fire extinguishing agent . A monoterpene is defined in the chemical literature as C_I0H₁₆. As stated, CFC 11 and CFC 12 are now well known to be detrimental to the ozone layer.

Halocarbon extinguishants fall into two broad groups, streaming agents and flooding agents. A streaming agent is directed at the source of the fire and should be high boiling to thereby resist decomposition until it reaches the source of the fire. A flooding agent fills a volume around the fire and smothers the fire. It should be low-boiling so that it vaporizes readily.

U.S. Patent No. 4,826,610, issued May 2, 1989, Derek A. Thacker, discloses a firefighting composition comprising one or more halocarbons, namely Halons 11 (CFC 11) , 12 (CFC 12), 113 (CFC 113) and 114 (CFC 114) , together with 1% to 14% by weight of the extinguishant base of a sesquiterpene and one or more essential oils. A sesquiterpene is a compound having the formula C_1SH₂₄. Solvents and dispersing agents may also be provided. This composition is suited for stream-type firefighting situ¬ ations. The formulation is not touted to be ozone friend- ly.

United States Patent No. 4,954,271, issued September 4, 1990, Raymond W. Green, discloses and protects high boiling environmentally amicable stream-type fire extinguishing agents. The stream-type agents comprise in combination: (a) more than 50% by weight of a fluoro- chlorocarbon selected from the group consisting of: 1,1- dichloro-2, 2, 2-trifluoroethane, and 1, 2-dichloro-2, 2- difluoroethane; (b) less than 48% by weight of a fluorocar¬ bon selected from the group consisting of: chlorodifluoro- methane, 1-chloro-l, 2, 2, 2-tetrafluoroethane, penta- fluoroethane, 1, 2, 2, 2-tetrafluoroethane; and (c) a detoxifying substance selected from the group consisting of terpenes: citral, citronellal, citronellol, limonene, dipentene, menthol, terpinene, terpinolene, sylvestrene, sabinene, methadiene, zingiberene, ocimene, myrcene, α- pinene, /J-pinene, turpentine, camphor, phytol, vitamin A, abietic acid, squalene, lanosterol, saponin, oleanolic acid, lycopene, β-carotene, lutein, α-terpineol, and p- cymeme; and unsaturated oils; oleic acid, linoleic acid, linolenic acid, eleosearic acid, lincanic acid, ricinoleic acid, palmitoleic acid, petroselenic acid, vaccenic acid, and erucic acid, in the range of from 2 to 10% by weight.

In the chlorofluorocarbon stream-type mixtures taught by Green, it is emphasized that high boiling chloro- fluorocarbons should comprise more than 50% weight of his mixtures. In contrast, low boiling compounds must be less than 50% weight (see column 2, lines 22-27) . In the examples disclosed in Green, a low boiling chlorofluoro¬ carbon such as CFC 12, which boils at -30°C, amounts to 15% weight of the total formulation. The other components are in the vast majority and boil at temperatures well above 0°C. For instance, in Example 2 of Green, column 4, line 61, the boiling point of the NAF Interior Mixture is stated as being 10°C. Thus, the high boiling mixtures disclosed by Green are useful as stream-type extinguishants and are virtually the opposite of the low boiling mixtures which are suitable as flooding agents.

Two U.S. patents, U.S. Patent No. 5,141,654, issued August 25, 1992, Fernandez, and U.S. Patent No. 5,393,438, issued February 28, 1995, Fernandez, are of general interest because they disclose extinguishants. Both patents of Fernandez disclose chlorofluorocarbons which are not fully halogenated, with the provision that there be at least one fluorine atom (see column 2, line 57, of 5,141,654) in each halocarbon. However, the halocarbons are used in pure form. There is no disclosure in either Fernandez patent of using one or more detoxifying sub¬ stances. Furthermore, neither Fernandez patent discloses any significance inherent with low boiling chlorofluoro¬ carbons.

SUMMARY OF THE INVENTION

The invention pertains to a fire extinguishing mixture of the formula:

(a) about 90% to 100.0% wt. of a halocarbon selected from the group consisting of: hydrochlorofluorocarbon.21 - dichlorofluoromethane hydrochlorofluorocarbon.22 - chlorodifluoromethane hydrofluorocarbon 23 - trifluoromethane hydrochlorofluorocarbon.123 - 2, 2-dichloro-l, 1, 1- trifluoroethane hydrochlorofluorocarbon.123a - 1,2-dichloro-l, 1, 2- trifluoroethane hydrochlorofluorocarbon.124 - 2-chloro-1, 1, 1, 2- tetrafluoroethane hydrochlorofluorocarbon.124a - 1-chloro-1, 1, 2,2- tetrafluoroethane hydrofluorocarbon 125 - pentafluoroethane hydrochlorofluorocarbon.131 - chlorotrifluoroethane hydrochlorofluorocarbon.132 - 1, 2-dichloro-l, 1- difluoroethane hydrochlorofluorocarbon.133 - 2-chloro-1, 1, 1- trifluorethane hydrofluorocarbon.134a - 1,1,1,2- tetrafluoroethane hydrofluorocarbon.227 - heptafluoropropane hydrofluorocarbon.236 - hexafluoropropane hydrofluorocarbon.245 - pentafluoropropane; and (b) between 0.25 and 10% by weight of a detoxifying substance selected from the group consisting of: ethene propene butene isopropene pentene isopentene trimethylethene tetramethylethene butadiene

2-methylbutadiene pentadiene isobutylene; and

1, 3-butadiene; the mixture having a boiling point of between about -85° or -80°C and about -10°C to 25°C, a formula molecular weight in the range of about 70 to 250, and a vapour pressure of about 0.1 MPa to about 5 MPa at 25°C, said fire extinguishing agent being non-toxic and environ¬ mentally benign in both natural form and degraded fire exposed form. In another aspect, the invention pertains to an additive for halogenated fire extinguishants and fire extinguishing flooding mixtures consisting of one or more hydrocarbons having from two to six carbon atoms, with one or more double bonds, said additive reducing the amount of hydrogen halides and carbonyl halides that are produced on exposure of the extinguishant or mixtures to fire. The additive for halogenated fire extinguishants and fire extinguishing mixtures can have four or more carbon atoms with two or more double bonds, where at least two of the double bonds are conjugated.

The additive can be selected from the group consisting of: ethene propene butene isopropene pentene isopentene trimethylethene tetramethylethene butadiene 2-methylbutadiene pentadiene isobutylene; and 1, 3-butadiene.

The invention is also directed to a specific additive for halogenated fire extinguishants and fire extinguishing flooding mixtures consisting of 1,3- butadiene, said additive reducing the amount of hydrogen halides and carbonyl halides that are produced by the halogenated fire extinguishants and fire extinguishing mixtures on exposure to fire. The fluid viscosity of the mixture can be below 1.0 centipoise between the initial boiling point of the mixture and 25°C. The invention is also directed to a non-toxic environmentally benign fire extinguishing mixture for use in a flooding fire extinguishing technique, said fire extinguishing mixture comprising about 82% by weight HCFC- 22, about 9.5% by weight HCFC-124, about 4.75% by weight HCFC-123 and about 2% by weight 1,3-butadiene.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The inventors have determined that fully halogenated halocarbons are highly stable, have long lifetimes, and are difficult to decompose. Thus when fully halogenated halocarbons enter the stratosphere, they take a long time to decompose and hence the damage time on the ozone layer is extensive. Specifically, two chlorofluorocarbons disclosed in Thacker, U.S. Patent No. 4,826,610, are fully halogenated compounds. In other words, all of the avail¬ able substitution positions on the carbon backbone are taken up by either chlorine or fluorine. Thacker did not recognize that fully halogenated chlorofluorocarbon com¬ pounds are highly stable, difficult to decompose, and hence are a primary enemy of the ozone layer enveloping the earth.

Specifically, Green discloses high boiling fully and partially halogenated chlorofluorocarbon mixtures which are suitable as streaming extinguishants. The Green mixtures comprise the following chlorofluorocarbons: CFC 11, CFC 12, CFC 22, CFC 114, HCFC 123, HCFC 124, HFC 125, HCFC 132 and HFC 134. Of these chlorofluorocarbons, CFC 11, CFC 12 and CFC 114 are fully halogenated chloro- fluorocarbons. Green did not acknowledge the difference between fully and partially halogenated chlorofluorocarbons and that chlorofluorocarbons that are fully saturated with halogen atoms are difficult to decompose and are harmful to the ozone layer protecting the earth. The inventors have invented a family of low boiling partially halogenated chlorofluorocarbon formula¬ tions, which are ideal as fire flooding agents. Further¬ more, the formulations are environmentally benign because the halocarbons are not fully halogenated, that is, there is always at least one hydrogen atom present in the chlorofluorocarbons and fluorocarbons comprising the family. In other words, the low boiling partially halogenated chlorofluorocarbon compounds disclosed herein provide at least one hydrogen site on each molecule which thereby provides a location for the breakdown or decomposi¬ tion of the molecule.

As is well understood in the art, the inclusion of hydrogen in a compound changes the physical and chemical characteristics of that compound sufficiently that it is not immediately predictable or obvious that the compound including the hydrogen atom will function or perform in a manner that is similar to compounds which are fully halogenated. The inclusion of hydrogen, a highly flammable and reactive element in its uncombined form, in a fully halogenated hydrocarbon to thereby render it only partially halogenated, can be expected by a person skilled in the art to dramatically alter the chemical characteristics of the fully halogenated hydrocarbon. It is unlikely that a person skilled in the art would expect that a partially halogenated aliphatic hydrocarbon could be substituted for a fully halogenated aliphatic hydrocarbon in a flood-type fire extinguishing mixture because the results would not be predictable.

Furthermore, knowledge acquired by a skilled artisan from stream-type halocarbon extinguishants cannot be extrapolated with predictability to flood-type halocarbon extinguishants.

At the time of development of the Thacker and Green stream-type fire extinguishing formulations, indis¬ criminately using by and large high boiling fully halogenated chlorofluorocarbons, Thacker and Green did not disclose that such chlorofluorocarbons would be damaging to the ozone layer encompassing the earth. Furthermore, Thacker and Green would not have been aware of global warming consequences of their fully halogenated chloro¬ fluorocarbons. The low boiling fire flooding mixtures disclosed by the inventors herein are partially halogenated halo¬ carbons and have highly desirable low ozone depletion potentials, and perform well as fire flooding agents, in natural form as well as degraded form which occurs on exposure of the extinguishant to fire.

We have also invented a family of low boiling hydrocarbons of two to six carbons with one or more double bonds in each molecule, for use in detoxifiers (or acid scavengers) in association with low-boiling halocarbons used as flooding-type extinguishants.

Overall, we have invented a family of lower alkenes detoxifying agents which, when used in combination with a family of new hydrochlorofluorocarbon and hydro- fluorocarbon fire extinguishing agents, make ideal flood- type fire extinguishants and also render the decomposed halocarbons non-toxic and cause minimum damage to the ozone layer of the earth. The family of flood-type extinguishants I have invented contain no bromofluoro- carbons which have been discovered to have serious ozone damaging effects.

Fire extinguishing mixtures for flooding applica- tions, that is, smothering the fire by filling a volume space, as opposed to streaming the fire extinguishing agent onto the source of the fire, should be considerably more volatile than for streaming-type applications. In stream¬ ing applications, the mixture should remain cohesive and resist decomposition due to heat, until it reaches the source of the fire. The need for cohesion of the mixture in flooding-type situations is not only reduced but in fact cohesion becomes detrimental to rapid dispersion of the agent throughout the volume. Thus, for flooding applica- tions, it is desirable that the halocarbons making up the extinguishant have low boiling points. It is also desir¬ able that the detoxifying substance used in the formula¬ tions for flooding applications have a lower boiling point than that used for streaming-type applications. Lower boiling points of both the halocarbons and the detoxifiers promote dispersion.

Apart from that, we have discovered that some of the substances listed by Thacker and Green can in some cases leave an undesirable terpene or sesquiterpene residue when used in flooding applications to extinguish fires (even though the Green and Thacker formulations are primar¬ ily intended for stream-type use) .

While we do not wish to be bound by any theories, we believe that the halogen scavenging by the detoxifier when a halocarbon is used as a fire extinguishant takes place on a molecular basis and thus lower molecular weight detoxifiers are required at a lower weight fractions of halocarbons to achieve the same degree of detoxification as in the case of higher molecular weight compounds . We have discovered that low-boiling light hydro¬ carbons with two or more conjugated double bonds are particularly effective as detoxifiers (acid scavengers) for low-boiling halocarbons used as flooding extinguishants. There is resonance stabilization of formed intermediate products during the halogen scavenging process when the low-boiling halocarbons are used as a flooding fire extin- guishants. Alkenes, having six or less carbons and one or more double bonds, have higher vapour pressures and lower boiling points than the terpene additives listed by Green. Again, regarding halocarbons and ozone layer damage, we do not wish to be bound by any adverse theories. However, we offer the following discussion as a possible aid to understanding why the low boiling halocarbons we have invented are successful as environmentally friendly flood-type extinguishants. Halocarbons which contain at least one hydrogen, we believe, are generally more environ- mentally benign than their fully halogenated counterparts because the presence of even a single hydrogen on a halo¬ carbon molecule provides a site which is subject to attack by hydroxyl radicals . This leads to breaking down of the molecule and a drastic reduction in the atmospheric life- time of the molecule. The ozone depletion potential of a compound is, we believe, dependent on its atmospheric lifetime mainly due to the long time that it takes the compound to be transported from near the earth's surface up and into the stratosphere. Global warming potentials are also strongly dependent on atmospheric lifetime as the time integrated climate forcing of even a strongly absorbing molecule will be minimal if the molecule does not survive a significant time in the atmosphere. Our invention therefore involves using partially halogenated halocarbons which contain at least one hydrogen to thereby provide a molecule breakdown site and thus the compound is relatively environmentally benign.

When a flooding or inerting fire extinguishing technique is to be used, that is, where the extinguishant is released into an enclosed volume containing a fire, and maximum toxic decomposition products are generated, we have discovered that fires of this type are quickly and safely extinguished using low-boiling partially halogenated non¬ toxic mixtures as follows :

(a) 90 to 99.9% by weight of one or more of: dichlorofluoromethane (HCFC 21) chlorodifluoromethane (HCFC 22) trifluoromethane (HFC 23) dichlorotrifluoroethane (HCFC 123) chlorotetrafluoroethane (HCFC 124) pentafluoroethane (HCFC 125) dichlorodifluoroethane (HCFC 132) chlorotrifluoroethane (HCFC 133) tetrafluoroethane (HCFC 134) heptafluoropropane (HFC 227) pentafluoropropane (HFC 245) hexafluoropropane (HCFC 236)

(b) 0.1% to 10% weight of one or more hydrocar¬ bons having from two to six carbon atoms, and one or more double bonds.

The mixture should be relatively volatile and preferably have a boiling point between -85°C and 25°C, a formula molecular weight between 70 and 250 and a vapour pressure between about 0.1 MPa and 5 MPa at 25°C.

The 0.1% to 10% by weight of any one or more detoxifying hydrocarbons with from two to six carbon atoms, with one or more double bonds, may be one or more of the following light alkenes: ethene propene butene isopropene pentene isopentene trimethylethene tetramethylethene butadiene 2-methylbutadiene pentadiene isobutylene

1,3-butadiene

The precise choice of agents and compositions will be governed in each case by a balance of cost, factors governing fluid and vapor flow, factors governing fluid and vapor physical characteristics, and the configuration of the extinguishant flooding system needed to protect the in¬ tended volume (s) . We have also discovered that for extinguishing fires in enclosed volumes by flooding or inerting tech¬ niques, it is critical that the initial boiling point of the fire extinguishant is low. This includes both the halocarbons and the detoxifier. We have also discovered that it is important in such flooding fire extinguishants that the detoxifying agent (s) has a low boiling point which coincides closely with that of the halocarbon(s) so that they volatilize at the same time. The mixtures we have invented that are suitable for flooding or inerting fire extinguishing agents have the following beneficial characteristics and attributes:

1. The class of fire flooding mixtures according to the invention must be rich in lower boiling compounds, and not exhibit much cohesion. The flooding class we have described will therefore rapidly vaporize and flood the intended volume with extinguishant to a concentration level that is required to smother or inert the gaseous phase and prevent or extinguish the included fire.

2. The low boiling points exhibited by our class of flooding mixtures enables low boiling detoxifying agents to be used. This comprises low boiling light unsaturated alkenes which cannot, because of their low boiling points, be successfully used with higher boiling streaming- type extinguishants.

3. We have found surprisingly that when the detoxifying agents are eliminated completely from the fire extinguishing mixtures, the fire extin¬ guishing capacity is less efficient than when the detoxifying compounds are included in the agents. Also, when detoxifying lower alkenes are omitted, dangerous levels of toxic halogen and hydrogen halides are produced when the halocarbon extin¬ guishant mixture is decomposed by the heat of the fire. 4. To maximize the foregoing attributes, we have determined that the physical characteristics of a flooding mixture should have a boiling range between -80°C and -10°C. It should also have a liquid viscosity less than 1.0 centipoise throughout a temperature range from initial boiling point of the mixture to approximately 25°C.

Example 1

In one particular test, a test chamber measuring 0.5 x 3 x 3 meters and containing five standard pot fires was flooded using a pipe system about 3 meters in total length. The pot fires were extinguished in less than 10 seconds by using 1 kg of a mixture consisting of 96 percent by weight of chlorodifluoromethane and 4 percent by weight of limonene through the pipe. This mixture had an initial boiling point of -40.5°C and a liquid viscosity of 0.21 centipoise at 25°C.

Example 2 In another evaluation using the same test chamber as in Example 1, the five pot fires were extinguished in less than 10 seconds using 1 kg of a mixture consisting of 85 percent by weight of chlorodifluoromethane, 11.5 percent by weight of 1-chloro-1,2,2,2-tetrafluoroethane, and 3.5 percent by weight of dipentene.

Example 3 In a third test using the same test chamber as in

Example 1, the five pot fires were extinguished in less than 10 seconds using 1 kg of a mixture consisting of 65 percent by weight of chlorodifluoromethane, 15.5 percent by weight of 1, 2-dichlorotetrafluoroethane, 15.5 percent by weight of trichlorofluoromethane, and 4 percent by weight of limonene. This mixture had an initial boiling point of -27°C and a fluid viscosity of 0.28 centipoise at 25°C. Example 4 In a fourth application using the same test chamber as in Example 1, the five pot fires were extin¬ guished in less than 10 seconds using 1 kg of a mixture consisting of 65 percent by weight of dichlorodifluoromethane, 15.5 percent by weight of 1,2- dichlorotetrafluoroethane, 15.5 percent by weight of trichlorofluoromethane and 4 percent by weight of limonene. This mixture exhibited an initial boiling point of -13°C and a viscosity of 0.36 centipoise at 25°C.

Example 5 In a fifth test using the same test chamber as in Example 1, the five pot fires were extinguished in less than 10 seconds using 1 kg of a mixture consisting of about 65 percent by weight of dichlorodifluoromethane, about 15.5 percent of 1, 2-dichlorotetrafluoroethane, about 15.5 percent by weight of trichlorofluoromethane, and about 4 percent by weight of dipentene.

Example 6 In a sixth evaluation using the same test chamber as in Example 1, the five pot fires were extinguished in less than 10 seconds using 1 kg of a mixture consisting of about 75 percent by weight of chlorodifluoromethane, about 11.75 percent by weight of 1, l-dichloro-2, 2 , 2-trifluoro¬ ethane, about 9.5 percent by weight of 1-chloro-l, 2, 2, 2- tetrafluoroethane, and about 3.75 percent by weight of limonene.

Example 7 In fire extinguishing tests conducted using a mixture of HCFC's in the ratio 82:9.5:4.75 HCFC-22 :HCFC- 124 :HCFC-123, it was found that when 2 parts of 1,3- butadiene were added, the HF concentrations generated decreased by 60% compared to the tests where no hydrocarbon was added to the HCFC mixture. These examples vividly demonstrate the key role that low fluid viscosity and low boiling point plays in parameterizing the mixtures required to achieve optimum volume of flood-type fire extinguishing performance. The goal is to achieve mixtures having an initial boiling point approximating -60°C and a fluid viscosity approximating 0.15 centipoise at 25°C.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A fire extinguishing mixture which is environ¬ mentally benign characterized by: (a) 90 to 99.9% wt. of one or more halocarbons selected from the group consisting of: chlorodifluoromethane dichlorofluoromethane trifluoromethane dichlorotrifluoroethane dichlorodifluoroethane chlorotetrafluoroethane chlorotrifluoroethane pentafluoroethane tetrafluoroethane heptafluoropropane hexafluoropropane pentafluoropropane; and

(b) 0.1% to 10% by weight of a detoxifying agent of one or more hydrocarbons having from two to six carbon atoms, with one or more double bonds, said fire extinguish¬ ing agent being non-toxic and environmentally benign in both natural form and degraded form on exposure to fire.

2. A mixture as claimed in claim 1 wherein the mixture has a boiling point between about -85°C and 25°C, a formula molecular weight between about 70 and 250 and a vapour pressure between about 0.1 MPa and 5 MPa at 25°C.

3. A mixture as claimed in claim 1 wherein the hydrocarbon of from two to six carbon atoms is selected from the group consisting of: ethene propene butene isopropene pentene isopentene trimethylethene tetramethylethene butadiene 2-methylbutadiene pentadiene isobutylene; and

1,3-butadiene.

4. A flood-type fire extinguishing mixture of the formula: (a) about 90% to 100.0% wt . of a halocarbon selected from the group consisting of: hydrochlorofluorocarbon.21 - dichlorofluoromethane hydrochlorofluorocarbon.22 chlorodifluoromethane hydrofluorocarbon 23 trifluoromethane hydrochlorofluorocarbon.123 2, 2-dichloro-l, 1, - trifluoroethane hydrochlorofluorocarbon.123a 1, 2-dichloro-l, 1,2- trifluoroethane hydrochlorofluorocarbon.124 2-chloro-l, 1,1,2- tetrafluoroethane hydrochlorofluorocarbon.124a 1-chloro-l, 1,2,2- tetrafluoroethane hydrofluorocarbon 125 pentafluoroethane hydrochlorofluorocarbon.131 chlorotrifluoroethane hydrochlorofluorocarbon.132 1,2-dichloro-l, 1- difluoroethane hydrochlorofluorocarbon.133 2-chloro-l, 1, 1- trifluorethane hydrofluorocarbon.134a 1,1,1,2- tetrafluoroethane hydrofluorocarbon 227 heptafluoropropane hydrochlorofluorocarbon.236 hexafluoropropane hydrofluorocarbon 245 pentafluoropropane; and

(b) between about 0.25 and 10% by weight of a detoxifying substance selected from the group consisting of: ethene propene butene isopropene pentene isopentene trimethylethene tetramethylethene butadiene 2-methylbutadiene pentadiene isobutylene; and

1, 3-butadiene; the mixture having a boiling point of between -85° and about 25°C, a formula molecular weight in the range of about 70 to 250, and a vapour pressure of about 0.1 MPa to about 5 MPa at 25°C, said fire extinguishing agent being non-toxic and environmentally benign in both natural form and degraded form on exposure to fire.

5. A halogenated fire extinguishant of fire extin¬ guishing flooding mixture comprising:

(a) a halogenated hydrocarbon fire extinguishant or halogenated hydrocarbon fire extinguishing flooding mixture; and

(b) one or more hydrocarbons having from two to six carbon atoms, with one or more double bonds, said hydrocarbons reducing the amount of hydrogen halides and carbonyl halides that are produced on exposure of the extinguishant or mixtures to fire.

6. A halogenated fire extinguishant as claimed in claim 5 wherein the one or more hydrocarbons have four or more carbon atoms with two or more double bonds, and at least two of the double bonds are conjugated.

7. A halogenated fire extinguishant as claimed in claim 5 wherein the additive is selected from the group consisting of: ethene propene butene isopropene pentene isopentene trimethylethene tetramethylethene butadiene 2-methylbutadiene pentadiene isobutylene; and

1, 3-butadiene.

8. A halogenated fire extinguishant as claimed in claim 5 wherein the hydrocarbon is 1,3-butadiene, said compound being present in sufficient quantity to reduce the amount of hydrogen halides and carbonyl halides that are produced by the halogenated hydrocarbon fire extinguishants and fire extinguishing mixtures on exposure to fire.

9. A mixture as claimed in claim 1 wherein the initial boiling point of the mixture is between -80°C and -10°C.

10. A mixture as claimed in claim 3 wherein the fluid viscosity of the mixture is below 1.0 centipoise between the initial boiling point of the mixture and 25°C.

11. A mixture as claimed in claim 4 wherein the fluid viscosity of the mixture is below 1.0 centipoise between the initial boiling point of the mixture and 25°C.

12. A non-toxic environmentally benign fire extin- guishing mixture for use in a flooding fire extinguishing technique, said fire extinguishing mixture comprising about 82% by weight HCFC-22, about 9.5% by weight HCFC-124, about 4.75% by weight HCFC-123 and about 2% by weight 1,3- butadiene.