FIRE RESEARCH STATION

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1 Fie Reseach No.717 Note SLURRES OF SOLD CARBON DOXDE AS EXTNGUSHNG AGENTS by D. J. RASBASH, P. F. THORNE AND W. D. WOOLLEY June J FRE RESEARCH STATON BRE Tust (UK) Pemission is ganted fo pesonal noncommecial eseach use. Citation of the wok is allowed and encouaged.

2 F.R.Note No. 717 June 1968 SLURRn:S OF SOLD CARBON DOXDE AS EXTNGUSHNG AGENTS by J. J. Rasbash, P. F. Thone and W. D. Woolley SUMM.!Ry A peliminay assessment has been made on the eectiveness o sluies o, solid cabon dioxide in liquid nitogen and in vapoizing liquid extinguishing agents :f'<o extinguishing small f'lammab'l e liquid ies. sluy was applied by being tipped onto the suace. The t has been ound that the sluy is moe eective than the solid o liquid phases used sepaately. The quantities o sluy needed to extinguish a'keosine ie., " was substantially smalle'than othe extinguishing agents commonly used at the pesent. time, and was also compaable to the quantity pedicted om theoetical consideations. Key wods: Cabon dioxide, solids, vapoising liqui~ sluy, 8J.tingaishzig 9gen~, / ie, lammable liquid',.1 Cown copyight This epot has not been published and should be consideed as contidentiot advance infomation. No -ctecncc should be made to it in any publication without the witten consent of the Diecto of Fie RQsQach. MNSTRY OF TECHNOLOGY AND FRE OFFCES' COMMTTEE,. ': JONT FRE RESEARCH ORGANZATON

3 F.R.Note No. 717 June 1968 SLURRES OF SOLD CARBON DOXDE AS EXTNGUSHNG AGENS by D. J. Rasbash, P.F. Thone, and W. D. Woolley NTliODUCTON n a pevious note 1 an estimate was made of the possibl~ contibution of cooling the fuel to the extinction of liquid fies by vapoizing extinguishing agents. This' estimate indicated that if the full cooling powe of the agent was exeted in educing the ate of buning of the fie, then the size of fie which cou.ld be extinguished by a given mass of agent could be multiplied by a facto of about thee. 'n paticula the possible contibution due to cooling powe of solid cabon dioxide was substantially highe than eithe the inhibiting, ineting of the cooling powe of any othe common vapoizing agent. This suggested that sluies of solid cabon dioxide in a liquid vapoizing agent could in cetain cicumstances be effective extinguishing agents 2 The pesent note descibes a peliminay expeimental investigation caied out to assess the possibility of using sluies containing solid cabon dioxide as pactical extingilishing agents. EXPERMENTAL The expeimental wok may be divided into two pats:- a) Exploatoy tests using liquid nitogen and some halogenated hydocabons.b) as the continuous phase fo the sluy; A seies of tests with a 50 pe cent sluy of solid cabon dioxide in.. bomochloodifluoomethane (BCB) to obtain a bette definition of the quantitative effect of using sluy. obsevations on the physical behaviou of applied to vaious sufaces. These tests inoluded the~e 'i sluies when Table 1 shows the methods of obtaining sluies and oomments on the sluies obtained.

4 TABLE 1 Method of pepaation and popeties of solid cabon dioxide sluies ;...---l-b-~-~-~-.~- ~-g::sity Me~.~~":~~::..,,::.: Liquid foming continuous phase of sluy _._ <; sluy sluy Liquid nitogen BubbHng CO 2 'gas into liquid nitogen _._---<-.~ Powde settled downwad. C.ould not obtain'moe than 15 pe cent solid CO 2 Dichloo~~f'1uoomethane. (.. Tichloofluoomethane Chloobomomethane Bomochloodif'1uoo~ methane L8 ~ Powde settled - )Solid cabon downwad slowly )dioxide )Held CO powde 2 gound to' a )well even upto powde sieved ~75 pe cent sluy though 1.5mn sieve and mixed with Powde settled fluid upwad apidly Except in the case of liquid nitogen all sluies wee obtained by ginding solid oabon dioxide, sieving off paticles geate than 1 ;5 mm, and mixing the gound mateial into the liquid agent- With liquid nitogen an attempt was made' to obtain the sluy diectly in situ by bubbling the cabon dioxide gas into the liquid nitogen, but although the paticle size of the SlulJT was vey fine it was not found possible to obtai~ content geate than 15 pe cent in this way. a sluy with a solid ~he test fies vaied and in geneal wee a few squae feet in size i the»:: t:: fuel being eithe petol o keosine; a 'p.m... 2.::::: ~ few tests wee caied out on fie. The metho~ of application also vaied, the one used mostly was diect! tipping of t.:t!ll agent fqm a beake into the fie. Fo puposes of compaison, tests with unsluied liquid nitogen, chloohomomethane and bomochloodifluoo inet-hlie and also unaluied solid cabon dioxide wee caied out on the same fies on which the coesponding sluy was used. RESULTS a) Exploatoy tests. The sluies in liquid nitogen wee tested against a keosine fie 0.5 m 2 afte a pebun time of ~n~minute.1150 cc of the sluy. wee poue~ down a sloping channel so as to flow onto the keosine fie i the time taken to pou the liquid was 83 seconds. -2- Appoximately one half of the

5 aea o~ the ~ie was cleaed o~ ~lame. A simila esult was obtained when 1150 cc o~ liquid nitogen wee poued onto the ~ie in 80 seconds. An attempt to pou liquid nitogen onto the ~ie moe apidly esulted in a suge o~ ~lame ~ollowed a ~ew seconds late by a mild explosion. t was noted in the tests with the sluy that the solid cabon dioxide sepaated out in the channel and also coagulated into patioles ~ in to 1 inch diamete on the su~ace o~ the petol. These wee slow to evapoate. Of' couse, the tempeatue of this sluy was that o~ liquid nitogen, i.e c, and thee~oe the solid cabon dioxide was cooled deeply below its sublimation point. 250 ml o~ the sluy in di~luoodichloomethanewas poued ~om a beake on' to a petol ~ie 0.35 m 2 aea afte a pebun time o~ 30 seconds. The fl~es cleaed fom most o~ the ~ie aea, but the ~ie was not quite extinguished. A simila esult was obtained when the same quantity o~ sluy was eected ~o~ an extinguishe body, 570 ml of sluy in chloobomomethane eected f'-om an extinguishe extinguished the same petol ~ie. Chloobomomethane alone could not be used in a simila way in the extinguishe; 570 ml of this liquid poued on to the petol ~ie within a peiod o~ 5 seconds almost, but not quite extinguished the fie. These tested suggested that the quantity equied ~o extinction with sluy was about 1,500 to 2,000 g(m 2(0.25 to 0.35 b/~t2), which is somewhat bette than the quantity that might be expected to be needed i~ wate o dy powde wee used as the extinguishing agent. (b) Test seies with (B.C.F.) sluy light Table 2 shows the esults o~ the tests in which BCF solid. CO 2 and BCF/CO z sluy wee appli.ed to a ~ie in a tay 40 em squae0 The agents containing liquid wee applied by pouing ~om a beake, the time of' pouing being about 2 to 4 seconds. The solid cabon dioxide was applied fom a small scoop the time of' application being about 7 seconds. n the tests of solid cabon dioxid!, on avgas and N.B.F. the opeato used gloves and helmet ~o potection against the :~lames. This impoved the pe~omance o~ the extinguishing agent. t was chaacteistic' of all the extinctions that the f'lame was pushed sideways and upwads of'f' the vessel. Photogaphs of' the extinction with the keosine fie ae given in Fig 1-4. With petol ~ies th~e was a geate tendency to eignite ~om a small pocket o~ ~lame emote ~om the vessel, even when the suf'ace of' the vessel had emained clea of f'lame ~o seveal aeconds A summay of' expeimental citical quantities equied to extinguish ~ies the di~~eent fuels is given in Table 3. in Fo compaison estimated quantities of' sodium bicabonate dy powde and wate in the ~om o~ light wate ~oam needed to extinguish the f'z-e s have been inoluded. -3-

6 'l'abl.e' 2 The effect of BCF, BCP/C02 slu~ and solid C02 on 1,600 cm2 fi'e (1.8 t2). Agent applied by pouing fom beake (BCF/C02) o spinkling fom scoop Csolid C02) (a) BCF alone on keosine fie othewise ebun time 60 seconds unless stated No. Amount used Remaks, ml E. Fuel could not be eignited~ Liquid tempeatue educed to 55 C E. Fuel could not be eignited even afte 5 minutes. Pebun 75 s E.. Fuel could not be eignited., Liquid tempeatue 78oe E. Reignited with match. Liquid tempeatue 80 0 c E. Reignited with difficulty. Liquid tempeatue 93 C on suf'ace ~80oC afte mixing.',,6,,7 25 (TWo tests) NE. Limiting quantity 50 ml (90 g) (b) BCF/C0 2 sluy on keosine fie E. 9 '130 E E" Eo E NE E., f " \" Limiting quantity 25 ml (40 g~ NE. Fuel could not be eignited. Liquid tempeatue 50 C. Reignited, with match. tempeatue 70 0 C. Liquid Reignited, with match" Liquid tempeatue 70 C. 5 sec. Reignited, with match. Liquid tempeatue 950C on suf'ace 80 0 C afte mixi:ng. 3=4 set'. Sluy thick and no t mob'i.le, (Ca.ied out 30' seconds afte test "7)" Fie almost extinguished Caied out 30 sec afte test 16. ' E. Extinction ove the whole suface aea of the vessel. NE. Fie not extinguished ove whole suf'ace aea of vease'l.,

7 TABLE 2 (cont'd) (c) Solid C02 alone on keosine fie No. AmOlmt used Remaks g (paticle size..::: 1.5 mm) 95 g (paticle size <::'1.5 mm) s (paticle size NE. <,,1.5 mm) g (paticle size NE. > 1.5 mm) Limiting quantity 90g., NE. 40 g added afte one minute pebun, slight cleaance. Followed in 10 seconds by futhe 40 g. Cleaance ove 4/5 aea but no extinction. E. Appli.ed wi thin 7 seconds. Extinction at 10 seconds. An agglomeation.of paticles continued to evapoate afte extinction. Applied within 7 seconds'; :-"' 4/5 cleaance no extinction. Applied within 7 cleaance within no extinction. seconds. 9/10 10 seconds but (d) BCF alone on petol (naow boiling point 62/68 C) fie pebun time 30 seconds ml Limiting quantity 250 ml (450 g) NE....., ",.., NE. E. Fie diven fom tay in. 4-5 seconds, but emained ali.ght at edge - spead back in 5 seconds. (e) BCF/C0 2. sluy on petol f'ie 25 26, , ml (two tests) (two tests) Limiting quanti ty 100 ml (1 60 g) E. Extinguished except f'o small f'lame at a distance about 1 m f'om vessel. Flashed back in 5 seconds. E. Result as fo test 24. E. ExtingUished 3 to 4 seconds. 'SUf'ace tempeatue 23 to 24 C. Tempeatue af'te mixi.ng 18 c. Could be eignited by a match. E. Extinguished i.n 4-5 seconds. Tempeatue educed to C. Reign.iti.on diff'icult. E. Extinguished tempeatue educed to about -10 C. Could not be eignited even with lage toch.

8 -6-. T.A1lLE 2 (cont'd) (f). BCF/C02 sl~ on AVTAG fie. 60 seconds pebun No Amount used 150 ml Limiting quantity 50 ml (80 g) E. E. n 3.5 seconds n 3.0 n Remaks E. n 4.5 " NE. Tay suface almost clea of flame. NE. Tay suface clea of flame except fo two small edge flames and some flame hoveing outside tay. (g) C02 powde «1.5 md paticle size) on AVGAS f'ie. Pebun 30 seconds. Paticles spinkleed evenly on suface fom scoof g :NE But ta.v almost clea of flame. 37* 300 E. 10 seconds 38* 220 E. 12 " 39* 200 E. 12 " 40* 200 E. 10 " but eignition fom small pocket of flame outside tay 41* 180 NE. Fie ust not extinguished 42* 150 NE. Fie not extinguished. Limiting quantity 200 s (h) C02 powde (<: 1.5 md paticle size) on NBP fie 42* 43* 250 g 200 E. E. Fie out in 10 sec. of agglomeated C02 afte extinction. 10 s lump left in tay Fie ust out in 12 seconds. "'Helmet and gloves won, because of exta time (about 4 seconds) needed to apply agent ove suface. (k) BCF/C02 sl~ on AVGAS. 30 seconds pebun 44 45, ml Limiting quantity 100 ml (160 g) E. Extinction in 5 seconds E. Ex:tinction in 5 seconds on tay, but eignition fom small ponket outside. NE. NE.

9 '-... TABLE 3 Expeimental citical quantities 1600 cm 2 fie,,,,-,ant.ity of agent needed (gans) Liquid Aw.tu ll.",tag At...gas Petol (keosine) (petol) (NBP) BCF - '-- BCF!C sluy Solid C0 2alon e Sodium bicabonate Dy powde, Light wate foam Appo~'mately ,,!tppox 'mately Table 3 shows that fo both the petol fie and the keosine fie> athe less than half the amount of sluy was needed to e:xtinguish the fie tlia-tj. with BCF alone, Howeve, both agents wee vey much moe effective on the keosine fie than on the petol fie. With the BCF!C0 sluy OD. the keosine fie 2 substantially less agent was used than would be expected if foam o dy powde wee used, but the impovement fo the petol fie was not so maked. A compai.son of tests 3 and 9 in Table 2 indicates that although the sluy could cool the liqui.d moe effecti1>ely than the BCF alone, it was not quite as effective in peventing eignition. This suggested that the solid cabon dioxide vapoized pefeentially to the BCF, This would be expected fom the lowe tempeatue of volatilization of the cabon dioxide. n tests when the fi.e was not extinguished, paticulaly on the petol fi.e it was noted that the suface bubbled vigoously afte the failue to extinguish and the fie buned with the poduction of black smoke, This suggested that B. C.F. was being vapoized fom the fuel, -7-

10 af'te Also the esidual fuel/tests 29 and 30 contained a substantial amount of BCF ~ even afte standing fo 24 hcus, Tests on spead of sluy on sufaoes Fou samples of BCF/C0 2 sluy wee applied to a laye of fuel in a vessel 30 em squae unde ambient (non buning) conditions. The esults ae shown in Table 4. On Avtag and Avtu the agent spead evenly acoss the suface and the evapoation was not violent. With NBP and Avgas the agent spead patchily and the evapoation was violent and of much shote duation. TABLE 4 Spead and evapoation tests of BCP/C0 2 sluy on a seies of fuels ~~;;;.apoation' time (sec) i Obsevations NBP 2.2 (62/6S oc) ~SUy spead unevenly ove whole t~ suface AVGAS 2.4 )leaving patche~ of )uncoveed fuel AVTAG 5,;7 )sluy spead evenly )ove whole tay AVTUR 16,0 )sufaoe Wi th solid cabon dioxide, a.5 g sample of the powde spead to abcut 10 to 20 em and evapoated in!.,2 to 1 5 seconds on the petol and 2 5 to 3.5 seconda on the keosine, A 5 g sample of the coase paticles 5 md diamete evapoated in 12 seconds, on the petol and 15 seoonds on the keosine. When the s Lu-y was poued on concete thee was little spead and aggegates of the sluy tended to evapoate in isolated small patches about 1 to 2 em diamete. The sluy poued on wate foze it almos t instantly f applied to one spot quite a lage lump of ice fomed which appeaed to enclose the sluy and estict futhe evapoation. Lage scale test~ A few tes.ts wee caied out with a 5 m 2 Avtu fie buning in a s.qua'e ta.. Attempts wee made to extinguish the fie by meely thowing the BCF/CO" sluy diectly on to the fie f'om a Dewa flask" 1 em and the pebum time one minute~ The depth of fuel used was ~ -8-

11 1300 g o sluy - the Bcaled up quantity o the citical ate o the small scale ie -. had little efect when thown on to the 5 m 2 ie. Howeve when ollowed ate 5 seconds by a uthe 1300 g a cleaance o lame om thee quates of the ie aea was obtained, 2500 g o sluy thown on to the fie esulted in a mild explosion. ollowed by a cleaance o flame om 50 pe cent of the fie aea. When ollowed by a uthe 2500 g o sluy 95 pe cent o the ie aea was cleaed o the flame. DSCUSSON n qualitative tems the.possible contibution which solid cabon dioxide could make by cooling to the extinction o a liquid f'le has been appeciated f'o- some time. An extensive seies o small-scale tests 3 wee caied out by Bugoyne: Katan and Richadson in 1949 on the extinction of small liquid f'l-es by dy ice. These indicated t~at diect cooling o the liquid made a useul contibution fo ies in liquids with f'lash points a..tobl1lb...m.t\ :i;oollchuilpe<:abui'e but not fo moe volatile liquids e.g_ petol. On the othe hand o less volatile liquids th~ stiing esulting f'-om the vapoizing pocess was impotant. t was assumed that o the moe volatile liquids the low flash point pevented the liqu~d om being cooled to the ie point and theeoe cooling was not an eective mechanism.. On the basis o the theoetical analysis 1 efeed to peviously, it may be shown that as long as vapoization takes place evenly nea the su-ace, then the contibution o coolin.g to the extinction o ne may be substantial. even i,.;.f the ligpid is not cooled to the ie point. The pesent tests conim this. in many o the extinctions with both petol and keosine the uel was not cooled to the ie point and flash back o eignition took place vey easily ollowing the tansient peiod duing which extinotion took place. This was paticulaly the oase when the amouat o sluy o BCF used was small. Fom available Lnf'omat Lon on the buning ates o keosine and petol tes 4 it lbo' be estimated that the ate of' buning of' the 1,600 cm 2 keosine and petol ies ae espectively 2.3" and 3.2 gammes pe second. On this basi.s, and assuming an extinction time o 5 seconds foe tohe slufes ailld:"bcf and 10 seconds o the solid cabondioxide the amounts of' application o agent to the ies that would have been expected to extinguish them, have been estimated and have been compaed with the amount actually used in Table 5, -9-

12 TABLE 5' Compaison of theoetical and expeimental amounts of extinguishing agents,!, Agent..Kenosine Petol lnbp) ; Expeimental theoetical expeimental theoetical i, BCF [ BCF/C0 2 " i sluy (, J Solid CO i alone , n all cases the is substantially less than the The diffeence was least fo BCF/C0 2 sluy on the keosine fie. Moeove if in this paticula instance of the longe evapoation time of 16 seconds' indicated in Table 4 is used instead of the extinction time of 5 seconds to estimate the theoetical %uantity then the diffeence between the expeimental and theoetical quantity would disappea. n othe instances howeve, the use of the data in Table 4 instead of the extinction time does not impove ageement. The obsevations on the We<! the agent evapoated whez, applied to the suface of the diffeent fuels give some insight into these disoepancies. When the sluy was applied t o keosine the agent spead apidly and evenly to the whole su-ace and then continued to evapoate unifomly fo a sufficiently long time to ensue the extinction of all flames that wee pushed off the fie. When the sluy was applied to petol, the sluy tended to evapoate violently ove a shot peiod. This led to an unevenness in evapoation, a st,iing effect within the liquid and an entainment of fuel fom busting bubbles into the flame. As a esult of this in the fie tests moe fuel was fed into the fflames and the tansient cleaance was not suffioiently long to pevent a flashback. The solid cabon dioxide did not spead as well as the sluy on keosine and tended to evapoate too quickly. The, lack of ageement between' the theoetical and expeimental esu]ts indicate that thee is ample oom fo impovement in the pefomance of the agents and the obsevations on the way the agents evapoate suggest a numbe of ways in which this impoved pefomance may be obtained. Application of the agent as a coase spay should allow moe unifom app.d.cat.lon of agents and should educe the violence of the evapoation. A change in the paticle size of the sluy and the natue of the continuous phase could also educe the violence of the evapoation of the sluy on the petol fie. -10-

13 Possib]y coating the solid c abon dioxide with a suface active agent may help dispese the solid cabon dioxide paticles ove the suface of the liquid. ndeed the tests suggest it may be possible to tailo a sluy to suit a given fuel unde a given fie condition. The ate of buning pe unit aea of the 5 m 2 fie would have been about twice as geat as the ate of buning of the 0.16 m 2 fie. On this basis the theoetical quantity of sluy needed would have been twice as much. 2500g when thown on the fie in two lots cleaed flame fom thee quates of the fie aea and as one lot fom one half of the aea. This suggests that a less cude method of application may well have bought about extinction of the fie with 2500g of the sluy, which is the expected quantity needed afte making allowance fo the geate buning ate of the fie. t is clea fom the esults that when the natue of the extinguishing agent and its application ae such that the cooling effect in educing the buning ate can be efficiently exeted, then a highly effective agent may be obtained. Thus, the amount of BCF/sluy equied to extinguish a keosine fie was fa less than the amount which would be expected if light wate c sodium bicabonate dy powde wee employed. Knock-down is vey fast indeed and was of the ode of seconds. Moeove, although the amount of agent used is insufficient to cool the fuel to the fie point when the minimum amount of agent is used and the fuel can be easily eignited, the continued application of the agent does cool and inhibit the flammable liquid making it vey difficult to eignite. The 50 pe cent BCF/C02 sluy is vey effective on keosine and Avtag. This agent may, theefoe, have application to aicaft cash fies whioh in geneal ae lage spill fies in these fu.els, and lage scale tests ae theefoe ecommended. Moeove although the tests on the 5 m 2 fie indicate that a cetain degee of sophistication in the agent is equied to obtain the best esults they also suggest that useful esults coul.d be obtained by vey cude methods of applioation. t may be possible theefoe to dump the agent fom a helicopte on to a fie o even popel the agent in to the cente of a fie by using a homing ocket; in the latte use of couse the agent would need to be in a weak containe which could be made to bust hamlessly. Howeve it would be difficult to use sluies containing solid cabon dioxide in common extinguishes because of the necessity of keeping the agent at low tempeatues. -11-

14 Conclusions (1) A sluy o solid cabon dioxide in bomochloodiluoomethane was about two to t~~ times Eiio~L!it~/as ef'f'eot ve in extinguishing petol and keosine ies as the liquid agent alone o solid cabon dioxide alone. h all cases the agent was applied by being poued onto the suface o a ie om a beake o a scoop,, (2) Compaatively small quantities o the sluy wee needed to extinguish a keosine ie (25 gams pe ft 2). (3) The quantity o sluy used f'o' the keosine f'le was compaable to the amount which might be estimated om a theoetical appoach. Howeve, the amount used o the petol ie was much geate than that estimated theoetically. (4.) Thee is scope f'o- impoving ef'f'f.ci.enoy o the sluies vaying thei popeties impoying the method of application to the fie (5).t appeas possible to obtain ef'f'ect ive sluies with solid cabon dioxide and a ange o halogenated hydocabons and vapoizing liquid agents, including a mixtue designed to have the same density as solid cabon Q.ioxide,:. \.hich may be u aef'ul ot' cetain pactical isks e.g. af.-c-af't cash ies ighting whee a vey apid contol with a small quantity o agent appeas feasible. '(6) Sluies o solid cabon dioxide in liquid nitogen do not appea to be vey ef'f'ec t i.ve because of the deposition o the solid,.abon dioxide and the peeential vapoization o the liquid nitogen. Refeences (1 )S\.'\BA..'lH. D."T. F.R.iote No, 705' (2) RASBASH. D. J, Patent Application 4542/67 (3) BURGOYNE.. J. M, KALAN. L. L. and RCHARDSON,. F. J.nst. Fet.Vol 35 No.312 p (4) RASBASH, D. J. ROGOWSK. Z. W. and STARK, G. W. V. Fuel p

15 <, FG.' M 2 KEROSNE FRE BEFORE APPLCATON OF BCF/C02 SLURRY. PREBURN 60 SECONDS

16 .- FG SECOND AFTER APPlJCATON OF 50 CM2 (80 GMS) BCF/C02 SLURRY

17 .- FG SECONDS AFTER APPLCATON OF SLURRY

18 ,-' FG SECONDS AFTER APPLCATON OF SLURRY. FffiE COMPLETELY EXTNGUSHED N SECONDS

19 , 1. l