CA2180586C - Environmentally benign non-toxic fire flooding agents - Google Patents

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

-~ Ar.r.Y Rr!NTrN NON-T~'YTC
FIRE F~QODING ~ rs FI~ F T~ INVRNTION
This invention involves novel total flooding and streaming-type fire exting~; RhAnt~ and novel detoxifiers which are envirnnmPnt;~l 1 y safe and non-toxic in natural form as well as fire exposed degraded forms.

DESrr~TPTION OF ~ P~TOR ART

In recent years, it has been discovered that certain halocarbons such as CFC 11, CFC 12, Halon 1301, and 15 the like, which have been widely used as refrigerants, blowing agents and fire exting~ hAnte 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 20 3pace. These harmful substance3 are being phased out of product ion .

Halocarbons have been used as f ire extinglli~h~ntR. Thacker, U.K. 1,603,867, discloses CFC 11 25 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 CloHI6. As stated, CFC ll and CFC 12 are now well known to be detrimental to the ozone layer.

Halocarbon exting ~ hi~ntf~ fall into two broad groups, streaming agents and flooding agents. A streamlng agent is directed at the source of the fire and should be high boiling to thereby resist decomposition until it 35 reaches the source of the fire. A flooding agent fills a volume around the fire and smothers the fire. It should be low-boiling 80 that it vaporizes readily.

~ 2 ~ 80586 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 5 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 Cl5U24.
Solvents and dispersing agents may also be provided. This composition is suited for stream-type firefighting si tu-10 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 15 high boiling enviL~ ~l ly amicable gtream-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, 2-20 difluoroethane; (b) less than 48~6 by weight of a fluorocar-bon selected from the group consisting of: chlorodifluoro-methane, 1-chloro-1, 2, 2, 2-tetrafluoroethane, penta-fluoroethane, 1, 2, 2, 2-tetrafluoroethane; and (c) a detoxifying substance selected from the group consisting of 25 terpenes: citral, citronellal, citronellol, l; ~nf~, dipentene, menthol, terpinene, terpinolene, sylve~trene, sabinene, methadiene, zingiberene, ocimene, myrcene, ~-pinene, ~-pinene, turpentine, camphor, phytol, vitamin A, abietic acid, squalene, lanosterol, saponin, oleanolic 30 acid, lycopene, ~-carotene, lutein, o~-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 10~6 by weight.
In the chlorof luorocarbon stream- type mixtures taught by Green, it is emphasized that high boiling chloro-~ 2 1 805~6 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 form-llAt;nn. The other components are in the vast majority and boil at temperatures well above 0~C. For ;ncltAn~, 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 exting~ hAnt~ 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, F~rnAn~f~7~ and IJ.S. Patent No.
5,393,438, issued February 28, 1995, FPrnAn~7, are of general interest because they digcloge exting-~ hAnt~
Both patents of Ff~rnAnr~ disclose chlorofluorocarbons which are not ~ully 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 F-~rnAn~1~7 patent of using one or more detoxifying sub-stances. Furthermore, neither FPrnAn-1.o7 patent discloses any significance inherent with low boiling chlorofluoro-carbons .
SUMM~RY OF THE INVE~IQN
The invention pertains to a f ire extinguishing mixture of the formula:
(a) about 909c to 100 . 0~6 wt . of a halocarbon selected from the group consisting of:
hydrochlorofluorocarbon.21 - dichlorofluoromethane hydrochlorof luorocarbon . 2 2 - ch~orodi f luoromethane hydrofluorocarbon 23 - trifluoromethane -~ 2~8~586 hydrochlorofluorocarbon.123 - 2,2-dichloro-1,1,1-trif luoroethane hydrochlorof luorocarbon . 123a - 1, 2 -dichloro-1, 1, 2 -trif luoroethane hydrochlorofluorocarbon.124 - 2-chloro-1,1,1,2-tetraf luoroethane hydrochlorofluorocarbon.124a - 1-chloro-1,1, 2, 2-tetraf luoroethane hydrofluorocarbon 125 - pentafluoroethane hydrochlorofluorocarbon.131 - chlorotrlflll--roethalle hydrochlorofluorocarbon.132 - 1,2-dichloro-1,1-dif luoroethane hydrochlorofluorocarbon. 133 - 2-chloro-1, 1,1-trifluorethane hydrofluorocarbon.134a - 1,1,1, 2-tetraf luoroethane hydrofluorocarbon.227 - heptafluoropropane hydro f luorocarbon . 2 3 6 - hexa f luoropropane hydrofluorocarbon.245 - pentafluoLu~,~J~dlle; and (b) between 0.25 and 10~ by weight of a detoxifying substance selected ~rom the group consisting of:
ethene propene butene isopropene pentene isopentene 25 trimethylethene tetramethylethene butadiene z-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 exting-i~h~ and fire 2 1 805~6 extingui~hing flooding mixtures consiRting of one or more hydrocarbons having f rom two to six carbon atom~, with one or more double bonds, said additive reducing the amount of hydrogen halides and carbonyl halides that are produced on 5 exposure of the extinguishant or mixture~ to fire. The additive for halogenated fire exting~l; Rh~ntR 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 15 trimethylethene tetramethylethene butadiene 2-methylbutadiene pentadiene isobutylene; and 1, 3-butadiene;
The invention iR also directed to a specif ic 20 additive for halogenated fire extinguishants and fire extinguiRhing flooding mixtures consisting of l,3-butadiene, said additive reducing the amount of hydrogen halides and carbonyl halides that are produced by the halogenated f ire extinguishants and f ire extinguishing 25 mixtures on exposure to fire. The fluid viscosity of the mixture can be below l. 0 ccntipoise between the initial boiling point of the mixture and 25~C.
The invention is also directed to a non-toxic 30 envill -It~l ly benign fire extinguishing mixture for use in a flooding fire extinguishing techni~ue, said fire extinguishing mixture comprising about 8296 by weight HCFC-22, about 9.5~ by weight ~CFC-124, about 4.75g6 by weight HCFC-123 and about 2~ by weight 1,3-butadiene.

~ 21 u0586 DETATT Rn DES~RTPTION OF ~ kt~:~]
EMBODI~Rl~TS OF TT~ INVENTION
The inventors have determined that f ully 5 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 wordA, all of the avail-able substitution pos~tion6 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 extingll~Ahi~rtA. 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-f luorocarbons . Green did not acknowledge the dif f erence 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 ~ormula-tions, which are ideal as fire flooding agents. Further-more, the formulations are environmentally benign because 21 8~5~6 the haloearbons are not fully halogenated, that is, tllere is always at least one hydrogen atom present in the ehlorofluoroearbons and fluoroearbons eomprising the family. In other words, the low boiling partially 5 halogenated ehlorofluoroearbon eompounds disclosed herein provide at least one hydrogen site on each molecule whieh thereby provides a location for the breakdown or deeomposi-tion of the molecule.
As is well understood in the art, the inclusion of hydrogen in a compound changes the physical and ehemieal eharaeteristies of that eompound suf f ieiently that it is not immediately predietable or obvious that the eompound ineluding the hydrogen atom will function or perform in a 15 manner that is similar to eompounds whieh are fully halogenated. The inelusion of hydrogen, a highly flammable and reactive element in its lln~ - in~-l form, in a fully halogenated hydroearbon to thereby render it only partially halogenated, can be expected by a person skilled in the art 20 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 25 fire extinguishing mixture because the results would not be predictable .
Furthermore, knowledge ac~[uired by a skilled artisan from stream-type halocarbon exting~ h~nt~ cannot 30 be extrapolated with predictability to flood-type halocarbon exting-1; 4h~nt~, At the time of development of the Thacker and Green stream-type fire extinguishing fur ll~t;~n~, indis-35 criminately using by and large high boiling fullyhalogenated chlorof luorocarbons, Thacker and Green did not disclose that such chlorofluorocarbons would be damaging to ~ 2 1 80586 the ozone layer encompassing the earth. Furthermore, Thacker and Green would not have been aware of global warming consequences of their fully halogenated chloro-f luorocarbons .

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 10 natural form as well a3 degraded form which occurs on exposure of the extinguishant to fire.
We have also invented a family of low boiling hydrocarbons of two to 3iX carbons with one or more double 15 bonds in each molecule, for use in detoxifiers (or acid scavengers) in association with low-boiling halocarbo~s used as flooding-type exting~l; Rh~nt~.
Overall, we have invented a family of lower 20 alkenes detoxifying agents which, when used in combination with a f amily of new hydrochlorof luorocarbon and hydro-fluorocarbon fire extinguishing agents, make ideal flood-type fire e~ctingl];~h~t~ and also rehder the decomposed halocarbons non-toxic and cause minimum damage to the ozone 25 layer of the earth. The family of flood-type exting~ h~nt~: I have invented contain no bromofluoro-carbons which have been discovered to have serious ozone damagi~g ef f ects .
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 21 8G~86 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 5 extinguishant have low boiling points. It is also desir-able that the detoxifying substance used in the ~ormula-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 10 promote disper3ion.
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 ses~uiterpene residue 15 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, 20 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 re~uired at a lower weight fractions of halocarbons to achieve the same degree of detoxification as 25 in the case oi higher molecular weight compounds.
We have discovered that low-boiling light hydro-carbons with two or more con~ugated double bonds are particularly e~ective as detoxifiers (acid scavengers) for 30 low-boiling halocarbons used as flooding exting~ hi~n~R.
There is resonance stabilization of formed intGrr~~; ~te products during the halogen scavenging process when the low-boiling halo~-~rh~-n~ are used a3 a flooding fire extin-guishants. Alkenes, having six or less carbons and one or 35 more double bonds, have higher vapour pre~sures 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 5 have invented are successful as enviI~ -nti~l ~y 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-10 carbon molecule provides a site which is subject to attackby 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 15 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 pot-~nt;;-l~ are also strongly dependent on atmospheric lifetime as the time integrated climate forcing of even a strongly absorbing 20 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 ~lydr U~t:ll to thereby provide a molecule breakdown site and thus the compound is relatively 2 5 envi r ~ t i~ 1 1 y benign .
When a f looding or inerting f ire extinguishing technique is to be used, that is, where the extinguishant is released into an enclosed volume cr-nt;~;n;n~ a fire, and 30 maximum toxic decomposition products are generated, we have discovered that fires of this type are ~uickly and safely extinguished using low-boiling partially halogenated non-toxic mixtures as follows:
(a) 90 to 99 . 996 by weight of one or more of:
dichlorofluoromethane (HCFC 21) chlorodifluoromethane (HCFC 22) - 11 - 2~8~586 trifluoromethane (HFC 23) dichlorotrifluoroethane (HCFC 123) chlorotetrafluoroethane (HCFC 124) pentafluoroethane (HCFC 125) dichlorodifluoroethane (HCFC 132) chlorotrifluoroethane (HCFC 133) tetraf luoroethane (HCFC 13 4 ) heptafluoLu~lu~alle (HFC 227) pentafluu~u~Lu~alle (HFC 245) hexafluo,u~lu~alle (HCFC 236) (b) 0.1~ to 1096 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 0.196 to 10~ by weight of any one or more detoxifying hydrocarbons with from two to 8iX 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 p.on~ l; .on~ isobutylene 3 o1, 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 35 vapor physical characteristics, and the configuration of the extinguishant flooding system nee~ed to protect the in-tended volume (8) .

- 12 - 2 1 805~6 We have also discovered that for extinguishing f ires in enclosed volumes by f looding or inerting tech-niques, it is critical that the initial boiling point o~
the f ire extinguishant is low. This includes both the 5 halocarbons and the detoxifier. We have also discovered that it i3 important in such flooding fire exting l; ~hAnt~
that the detoxifying agent (8) has a low boiling point which coincides closely with that o~ 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 f ire .
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 3 0 ext ing~ h il n t .~, 5. We have found surprislngly 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, - 13 - 2 1 8()5~36 dangerous levels of toxic halogen and hydrogen halides are produced when the halocarbon extin-guishant mixture i3 decomposed by the heat of the fire.

6. To maximize the foregoing attributes, we have determined that the physical characteristics of a f looding mixture should have a boiling range between -80~C and -10~~. It should also have a lo liquid viscosity less than 1. 0 centipoise throughout a temperature range from initial boiling point of the mixture to approximately 25~C.
Exam~le In one particular test, a test chamber measuring 0.5 x 3 x 3 meters and ~r~ntA;n;ng five standard pot fires was f looded using a pipe system about 3 meters in total 20 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 chlorodifluor~mf~thAn~ and 4 percent by weight Of 1; ~ n~nf~ through the pipe . This mixture had an initial boiling point of -40.5~C and a liquid viscosity of 0.21 25 centipoise at 25~C.
Exam~le 2 In another evaluation using the same test chamber 30 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 - tetraf luoroethane, and 3 . 5 percent by weight of dipentene 2 ~ 8~586 Examb~le 3 In a third test using the same test chamber as ln Example 1, the five pot flres were extinguished in less S 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 trichlorof luoromethane, and 4 percent by weight Of l; ~nP. This mixture had an initial boiling point of -27~C and a fluid vlscosity of 0.28 centipoise at 25~C.
Exam,,le 4 In a fourth application using the same test chamber as in Example 1, the f ive pot f ires were extin-guished in less than 10 seconds using 1 kg of a mlxture 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 o~ rAnp, This mixture exhibited an initial boiling point of -13~C
and a viscosity of 0.36 centipoise at 25~C.
F;XA le 5 In a fifth test using the same test chamber as in Example l, the f ive pot f ires 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 trichlorof luoromethane, and about 4 percent by weight of dipentene.
ExamAle 6 In a sixth evaluation using the same test chamber as in Example 1, the five pot fires were extinguished in ~ ~ ~ 805~6 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 1,1-dichloro-2,2,2-trifluoro-ethane, about 9.5 percent by weight of 1-chloro-1,2,2,2-5 tetrafluoroethane, and aboout 3.75 percent by weight ofl; nF~.
Exam~le 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 15 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 20 volume of flood-type fire extin~uishin~ performance. The goal is to achieve mixtures having an initial boiling point appr~ ;r~;n3 -60~C and a fluid viscosity approximating o.15 centipoise at 25~C.
As will boe 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 3 0 conE~trued in accordance with the substance def ined by the following claimg.

Claims (12)

1. A fire extinguishing mixture which is environmentally 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 extinguishing 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 99.9% wt. of a halocarbon selected from the group consisting of:
hydrochlorofluorocarbon.21 - dichlorofluoromethane hydrochlorofluorocarbon.22 - chlorodifluoromethane hydrofluorocarbon 23 - trifluoromethane hydrochlorofluorocarbon.123 - 2,2-dichloro-1,1,-trifluoroethane hydrochlorofluorocarbon.123a - 1,2-dichloro-1,1,2-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-1,1-difluoroethane hydrochlorofluorocarbon.133 - 2-chloro-1,1,1-trifluorethane hydrofluorocarbon.134a - 1,1,1,2-tetrafluoroethane hydrofluorocarbon 227 - heptafluoropropane hydrochlorofluorocarbon.236 - hexafluoropropane hydrofluorocarbon 245 - pentafluoropropane; and (b) between about 0.1 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 or fire extinguishing 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 mixture 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 hydrocarbon(s) is (are) 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 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.