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THE ll!lRARVFI~E RESEARCH STATION

BORE~II\~l WOOD·l-!EiUS.

Fire Research Note ~ \0

This must be re:umed to

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l=IRE RCEAI;CH 5TA1:'·6N.8O~EHAM \'/OOD,HEinS. WD62fl(.

FIRERESEARCHSTATION

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© BRE Trust (UK) Permission is granted for personal noncommercial research use. Citation of the work is allowed and encouraged.

Fire Research Station,

Borehamwood,

Herts.Tel,Ol-953-6177

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MINISTRY

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,FIRE' OFFICES·'CQMMITTEE, ,

JOINT FIRE RESEARCH 'ORGANIZATION

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FI RE. RESEARCH' NOTE,".f _',"' •.. "

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NO,,610

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This repcrt has not been puolished and'

should 00. considered as confidentialadvance information.' No reference shoudbe mode to' it, in ,any ,'publication, "

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-Novernbe r , 1965.,

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• 'l'HE FIRE PROPEllTIES OF COOKING FAi'S

by

G', W.: v. Stark and Wendy Mulliner

SUMllARY

F.R~ Note No.610.

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Tests on the fire properties of cooking fats used for deep fryinghave shown that when a cooking fat of any kind is overheated withoutfood added, the spontaneous ignition temperature and the fire point arereached when the temperature is inoreased to about 31O-360oC. There ia,therefore, an immediate danger of fire at temperatures above about 310oC...There ~~ also no substantial difference in the fire hazard of different

'fats, nor does the repeated use of the fat increase the fire hazard.'

'!4-Qui4 fat at cooking temperatures, (20S0C) is unlikely to catch fireif the fat passes through a' flame, but can ignite on surfaoes at or above'dull red heat. Such surfaces may be presented by solid eleotrio platesand ths,y are almost certain to be presented by radiant eleotric plates-during cooking~

The substantial interval between the maximum cooking temperature andthe temperature at which there is an imminent fire hazard, indicates thatthe presenoe of a SUitable thermo statio oontrol,on cookers would greatlyreduoe the risk of dangerous overheating~ I,"

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November, 1965.

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THE FIRE ;pROPERTIES OF COOKING' FA1fS

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G-. W.. V. Stark and WenCJ.y )fulliner, ,

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Experimental

Fires in cooking appliances .form a signific~t and inoreasing fraotion ,of the total number of firesl,2 '~'"'' Thus' the number' of fires in buildings in'the United Kingdom fttended by fire brigades' increas.ed from 51,000 in 1955to 79,000 iri 1963 (i.e. just over l~ times); In the same time those fireson cooking :appliances in which food was the mate'rial first ignited, increased

, from 3,000 to over 7,000 (2.3 times). in about 90 per oent of these fires .",the foods concerned were fata and oils. There is evidenoe th~t an important

oontributor.y factor to these fires is the ignition of fat and oil in a' pan',when it is left unattended. There is also evidence that the chance of afood or fat fire is greater with an eleotric, oooker than with a gas cooker.

In an earlier investigation4, the fire properties of one fat (groundnut oil) were studied and the conclusion was reaohed tha~ a major firehazard would result if thEi fat were overheated to a temperature of about 1500Cin excess of the standard cooking temperatlire. A possible' reason for theincrease of fires in cooking applianoes might be that a fat in oommon usecould beoome'espeoially hazardous under praotioal conditions. The main objeotof the enquiry described in this" report was to look for anY evidence thatthis might be so. A second object was to determine whether' there were any

_differenoes in the inoendive properties of g8SliandlloleetEr.iio'icookera. which:.might oontribute to the higher" frequenoy of fir'as assooiated with eleotriocooker-a,

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Materials and apparatus' used

The 'ignition temperature and the smoke and flash points of the fresh fatsare given in Table 1. The ignition temperattir~'was .m·easured in an apparatus',shown in Fig.4, similar to' that of the Electrioal Research Assooiationfollowing' the 'standard prooedure, and the smoke and fla'sh points were measuredusing apparatus', specified in' B.~9· 684 s J95B~ _

Su' fats were used in the tests as foll~wss-'

Corn oil lGround nut Oil, and representing vegetable fatsOlive oil' '1'

. Lard and dripping - representing aD1mal fats

. A hydrogenated oooking fat marketed by!a multiple grocers •

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Table 1

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Ignition temperature.···Flash

..E .R.A.: Snioke

Apparatus point point

°0 OF 00 OF °c OF,

~?rn.Qil .4l4 . 778 245, 473 219 427

Ground Ntit Oil '409 768 242 46B' 224- 436

,782 228 164Olive Oil 417 44} 327

Lard. 419 786 252 485 227 441

Dripping 420 788 " 'I 238 460' 154 309. ,

If,ydrogenated 403 , 757 291 555 229 444-Cooking FatI' ••

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Three heatd.ng applianoes 'were used, (Fig e-r),, ,

1. The burner of a (two burner and .grill) gas hob...·2. A 2 KW solid hot plate, controlled by 'an energy regulator

("simmer stat"). - • J

,3. A 2.2 KW radiant hot plate, 8 in dia,.,' controlled by an energy". \regulator.· ("simmer stat"}.

Thermocouples were fitted to these heating applianoes ,to measure thetemperature of the surfaces on which fat could be spilled. Gas flow was'measured by a flow.meter. Energy input into th~ electrio plates was notmeasured, directly, but the switohing oyole of an energy regulator wasmeasured to determine the proportion of load passed for a given setting ofthe regulator. This was found to be affeoted by the time the regulator hadbeen operating and by the direotion in which the setting of the regulator wasaltered. (Fig.2) •.•

. .The sol~d eleotrio plate' was oontrolled aocurately by a speoial system

for measurements of the temperature of the plate at which a drop of fat'~. spilled on it would ignite. (Firg.3). .

The fats were heated'in a oast aluminium pan of 7 in,dia., and 3 'pintscapacity. The lid of the pan had a small slot at the rim to aceommodatethe handle of the food basket used in some of the tests. The temperature ofthe heated fat was measured by a sheathed the:rnlocouple inserted thrOUgh theslot in the lid.

• Test pro gramme

Tests' on fat heated alone. One'litre of each fat was subjeoted to 8 cYQle'sof heating and CO'oling in the pan. The heating was oarried out on the gashob ,for a period of 15 minutes using Q. rate of";8upply of town gas of

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, .. i6.7 ft 3/hr . The.chip'basket was not used; although the 'lid of the pan wasI" in place. The sheathed thermocouple was placed centrally and 1 in above

. the bottom of the pan. ~h9 time ana tempeFBtYre were r@eoraed of the firstI appearanoe.of smoke I '(a) when t~e lid was momentari~ removed, and (b)

. through the slot in the lid With the lid in place. At the end of each,'heating period the gas was'turned off and the pan ,and contents allowed to'

\~. 'cool, with assistanoe' in the latter',tages by a draught of air., At the' endI '. of each cycle a 'sample of fat was withdr8.wnto measure the flashpoint after, " which the fat was 'returned to the pan.

',.' At the end of 8 cycles the fat in the pan was again heated but this time" ; '··.l).eating was continued until the fat ignited spontaneously when the lid wasl .,': removed (Fig.5). During the heating the smo~e pointp, the flashpoint andi. -: the fire point of the fat ,in the pan were measured, a wax taper being used

• I ; .as a small· ignition source for the latter tests. The lid of,the pan wasI ',' "replaced after .the fat had ignited spontaneously to extinguish the fire and

'T . the ga's was turned off. As the pan and its contents cooled the' lid was lifted 'and replaced from time'to' time until 'spontaneous ignition ceased. The lowest

" temperature at which spontaneous ignition occurre~ was recorded."

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,The fats were examined for deterioration during the tests,' the ignitiontemperature in the E.R.A. appar~tus being determined for some of the fats.

I! Fats used for cooking•. The cooking of food in the fats, might alter the effeot:' ., of heating on the igni~ability of the fats. ,Ground nut oil and the three ,I -', solid fats were therefore te'sted after repeated use for cooking, potato chips~

I • Seven hundred and fifty millilitres of. fat were heated on the gas hob using': :,'. gas at 16.7 ft 3/hr. When the fat temperature reached 1900C (373~) 290 g ofi -, chips in the chip baskat; were placed in the pan ,.. ,The quantity' of fat, theI ,: cooking temperature and the weight of chips cooked, were selected so as toI. -. -avoid froth-over of fat". The chips were cooked; for about 6 minutes, afterJ ' , which time' the chips were removed, the gas, turned 'off and the fat .ccol.ed;1- '. eight such cyclos were Inade.' A-further test was than made in which the fat

was heated alone until spontaneous ignition oocurred, .bhe same observationsand tests being made as in the first group'of tests.

Uneven heating of solid fats~ Solid fat was heated in the 'pan to' determineif the lower le~els of fat would be overheated before the bulk of the fat

_. became liquid. The sheathed thermocouple was placed close to the bottom of. the pan for the'se tests.

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! '._" Comparison of heating systems. ,A comparison was made 'of the heating of

1 1 Utre of fat in the pan using the three appliances. ,Heating rates wereI' , . adjusted on the electrio plates where necessary to give a rate of heating ofI' the fat no greater than that of the gas appliance. The tempera,tures reached

-: by the surfaqes of the applianoes were measured, in this group of tests.

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',' Ignition of fats on hot surf'acaa; . The temperatUre of'heated surfaces'on theI.·-~ three appliances, required for the 'ignition of a small drop, of fat from a

No.14 hypodermic needle, was measured. 'All freSh and used fats were testedI .. : on the solid eleotrio plate using the special'controlE(Ystem. ·(Fig.3). Used:_ ~ fat only was tested on the other tWo, applianoes.· ,For the gas burner the size

. -,' of the drops of fat was increased to 0.25 mI.'t··-~· ': . . '. _. .

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-Table 2

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..' 1st Cyole 2nd Cyole 3rd Cyole ,.th Cycle 5th Cycle 6th Cyole 7th Cycle 811lll· Cyole

, Smoke Pt. S.. ·Pt~ s, Pt.' S. Pt. S. Pt. S. Pt'. S. Pt. ' "'S. Pt.,-

F~' .~Flash F. F. F., F. F. F.Paint Lid L:i.d . pt. Lid Lid Pt~ Lid Lid Pt• Lid Lid Pt. Lid Lid Pt. Lid Lid Pt~

Lid Lid Pt. Md Lidoff on off OIl ' off on off OIl off. -OIl off on off OIl ~f • On

Corn °C 254- 173 212 24-6 173 218 241 135 239 24-3 135 177 24-3 132. 188 24J, 121 173 232 132 188 2271 ]21 205.

Oil OF 4-90 34-3 4J.4- 4-75 34-3 425 4-65 284- 4-62 4-60 284- 351 4-70 270 371 4-65 250 34-3 4-50 270 371 44-d 2,50 '4-02I

00 2di

Ground Nut 260 151 179 257 174- 230 260 190 254- 234- 184- 24-9 238 172 248 24-3 159 194- 256 157 204- lI.52 174·Oil OF 500 304- 354- 4-95 34-5 44-6 500 374 4-90 4-55, 363 4-80 4-60 341 4-78 4-70 318 381 qp 315 399 4-70: 306 34-5'

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Qlive °c N.D. N.D. 229 N.D. 224- 232 184- N.D. 218 N.D. 210 218 155 N~D. 216 N.D. 202 213 156 194 218' ]59 182I", Oil", , ~, 455: N.D; N.D. 44-5 N.D; 435 :450 363 N.D. 425 N'.D • 410 425 311 N.D. 420 N.D. 396 415 313 382 4251 3il8 3~0, . . . - ... -".

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1r-c 249 186 206 241 186 215 232 175 215 229 1.45 188 227 163 201 238 138 185 221 12i 203 ]34- 145

Lard 'OF 480 367 4-03 465 367 326 4-60 280 365 250 398 425 '"'3 293U9 450 347 419 44-5 293 370 44-0 394 4-30

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24Jj°C 254 179 220 249 154 196 249 159 244- 252 167 231 246 153 207 246 144- 205 '"224- ~150 '"245 ]57 212Dripping

OF 490 354 428 480 309 385 4-80 4-85 4-4-8 475 308 404 475 291 401 '"435 '"302 ·4-72 4651 Jl5 414319 471 333....

136 2101

Hydrogenated °c 260 214 23). 274 156 218 268 158 209 254 1.46 232 234- 95 154 254- 134- 184 210 194 ]35 184Cooking

OJ? 363 41d 263Fat 500 418 4-4-8 525 313 425 515 3).6 409 490 335 450 455 ;203 309 490 273 410 277 381 I2'74

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" Results , .Fats heated alone, ,The flash points and smoke points for each cycle of heating are given

in Table 2. The mean rate of rise of temperature of the eight repeatedheatings for each' fat tested'is' given in Fig.6., The rate of rise of

w temperature 'varied betwe'en" oycles,_ put the differences were small and: "probably not significant. These differences were due to slight differences,in the ambient conditions, and to slight differences in the initial

.: temperature of, the fat in the pan. After making due allowance for thej :' ~ifferences in initial ,.temperature, the differences between fats are also, " probably not' significant.

r'~ ~" Flash point and smoke point reduoed in' value as the number of cyclesL.' increased, the smoke .pod.rrt . reducing at a greater rate than the flash point ..i.' ,The hydrogenated cooking fat behaved exceptionally'in that the flash point, " at first increased, and did not decrease to below its initial value until after'

", the third cycle. Differences between the final flash point and smoke point ofthe six fats were small" the lowest flash point being given by the

. , hydrogenated cooking fat. ' All fats became more discoloured, and the liquidfats thickened, as the number of cycles increased. Dripping sputteredslightly during 'the first heating cycle, but not in sUbsequent oycLes , No

,sputtering occurred with the other fats.

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The fats ignited spontaneously without any frothing or boiling or anytendency for the fat to be ejected from the pan. The fumes escaping fromthe pan did not ignite'from the' gas flame. When the fats had cooled downthEW were felind te have ElisBolelii'ed and llhhltened eonBiderab~." ! '

(2) Fats used for cooking

When the chips were introduced the solid fats tended to spit somewhat'but tlii'S" tendency lessened as' the number of repeated oookings increased.The diiicolour;.tion of the fats was less than was found in the tests inSection (1). i , ',' '

The results' of the SUbsequent tests of heating to spontaneousignition are given in Table 4. The rate of change of temperature duringthe test with ground nut oil is given in Fig.9.' Smoke' and flash pointSdur-Lng heating were higher than, for the tests in Section (1), butspontaneous ignitions occurred at about the same temperatures with no'tendency dUring the tests for the' ~ats to froth over.

(3) Uneven heating of solid fats

Tests were made with dripping, as this was the' most solid fat.'The maximum temperature reached near the bo'ttom of the pan, when'the fatat, the top was solid, was 700 0 (158~),' which was about 500 e (9Qop ) aboveroom temperature.

(4) Ignition of fats on hot surfaces

The results of tests of ignition of drops of fat on the solid electrioplate are given in Table 5. There, was no significant differenoe, betweenthe temperatures of ignition 'of fresh or used fats.'

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Drops of fat from a pan of fat at about 2050C (40001 ) were notignited on any part of the gas hob with the burner alight. However,'whena drop of fat fell on to the edge of the burner boss, so'that it wastouohed ~y the flame, the flame was made luminous for a short time. Dropsof fat falling through the gELS flame were not ignited.

Drops of fat that were allowed to fallon to the radiant plate,tended to float off the element on a cushion' of vapour. Care was thereforetaken to place the drop so that, this did not oocur. The temperaturemeasurements during these tests were unreliable because of the markedcooling of ' the thermocouple leads. However, ,it was observed that thetUbular element had to be raised above dull red heat for ignition of thedrop of fat to occur. The ,temperatures reaohed by the surfaoes of theheating appliances during cooking are given in seotion,(S) •

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(5) Comparison of heating systems

The results' of these tests' are given in Pigs 10-12., The rate ofheating with the solid plate at full,power, 2 Kw,was less than that withgELS at 16.7 ft 3/hr (2.4 Kw). A similar rate' of heating to that of gas wasobtained with the radiant electrio plate operated at 1.8 Kw. The settingof the enerID" regulator to obtain this' output was difficult,. as theset~ing was near the point at whioh the regulator delivered full power.The temperatures of the caaf iron parts of the gELS hob were substantiallylower than the temperature of ignition' of fats' on hot surfaces, (aboutSSOOC (.966°p) ) and after 15 min heating 'were approaching thEiir maximum'value', The maximum value for the hottest part is estimated at about '4500 e (8400 p ) . The temperature' of: the solid eleotrio plate was about

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. 4600C (860°F) after 20 min heating but the temperature was still rising1 ' • steadily, sugges.ting that the final teinperatUi'e could well' exceed the igmtionI temperature of fats on hot surfaoes;' The temperature of the radiant plateI' reached a mean value of 559°0 (~660F), in about J min, and the fluotuation ofI t;eillP lil'lI lil,l:f' lI dUE! ~q j;!Jfj e,tltieTi of' the enerl!Y P8gu'j.atop was sueh that the p'l,ate

would reaoh 55000 (966OF) at the maximum of a fluotuation in' less than 2 min.·

Table 3

Fire properties of fats in the pan

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•. Table 4,i

Fire properties' of fats after repeated use for cooking'

Smoke Flash Fire Initial Final

point point point spontaneous spontaneousi¢tion temp. gnition temp.

°c Op Ocr OF °c Op' °C Op °c Op

Ground Nut Oil(used for.; 203 397 286 547 351 664- 361 682 279, 534

~Jooking)

Lard(used for 206 403 287 549 345 653 355 671 297 567

(Jooking)

Dripping(used for 154 309 247 477 334 633 355 671. 272 522, '

o"oking)

If,;rd.ro genatedcooking fat 190 374 294- 561 357 674 362 684- 265 509(used for

cooking),

r Initial FinalSmoke Flash Fire spontaneous spontaneousiPoin't .... ;w;i.ntJP°J.Xl.· ' 't' " '~.ti.! it.iL.f.l';!c ] •.5'.\1 ~!I'}'., r "". <W LE1!!ll'.·

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°c of °c of °c of °c of °C of

Ground Nut Oil (Fresh) 191 376 299 570 347 657 362 684- 267 513-

Ground .Nut Oil, (HeaWd) 135 275 250 482 335 635 34,2 64-8 280 536-

• •Corn Oil ,(Heated) 142 288 243 469 321 610 309 588 283 541

.Olive Oil (Heated) N.D. N.D. 243 469 ,316 601 340 644 280 536

Lard (Heated) 163 325 275 527 326 619 355 671 282 540

Dripping (Heated) 126 259 246 475 331 628 348 658 276 ?29

Hydrogenated .140 284- 228 442 331 628 355 671 273 523Cooking Fat ~iieat,ed)

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Table 5

6£pition temperAtureS of fats on hot plate

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Ignition on solid hotl plate

Fresh fat Fat usedfor 8 cycles'

°C OF °c OF

Corn Oil 526 977 542 1004-

Ground Nut Oil 552 1023 535 992

Olive Oil 562 1041 543 1008

Lard 541 1002 568 1052

Dripping 553 1025 537 997

Hydrogenated 568 1052 554 . 1028oooking fat

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Effect of type of fat on fire hazard

The tests reported above' show ttmt there was little difference in the'fire properties of the fats investigated. In particular the spontaneous'ignition temperatures and the fire'points, which are the two dangeroustemperatures as far as fire hazard is concerned, did not vary sUbstantiallyfor different fats iIor were they affected significantly by pre-use of thg fat.The initial spontaneous'ignition temperatures measured in the pan for bothfresh and used fats varied within the range of 309 - 362oC, and the fire points

, , ~n the pan v!'ried within the rangEr of 316 - 357CC. There were some differenoesin the smoke and the flash points of the fresh fats but these differencesbecame insignificant after the fats' had been used a number of times.

From the point of view of safety of the f~ts under oonditions of over­heating it is important to compare the dangerous temperatures mentioned abovewith the maximum temperature of the fat which would be required for cookingpurposes (20500). No fat under any conditions of test presented imminentdanger of fire at a temperature less than 1000C above the cooking temperature.On the other hand all the fats tested under all oonditions had become highly'hazardous witil a temperature increase of 1600C above the normal cookingtemperatures.. It may be concluded therefore that although there is no evidenoe,that any of the fats was, partiCUlarly prone to' cause a fire during normal use,all fats tested, could give rise to dangerous conditions when overheated.Inapeotion of the heating curves of the fat in Figs. 7,,8:!il.nd9 a1so:'showsthat the time of overheating required to produoe dangerous conditions is' about5 - 10 mins and is' generally less than the time 'required to' heat the fat toits normal cooking temperature.

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The temperature required to igDite drops of fat on a hot sUrfaoe wasvery muoh higher than that required for fats to become ignited spontaneous~

in a pan. Here again there was little dif'ference between various kinds offate 9~ Whe~R@r ~h@ t~~ij ~ft~O troAh @~ b§~ ~OOft "@o~m~ ~~mOij. ~ho igft~tiOfl

r temperature for all fats being about 5500C or dull red heat. -

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Incendive properties of the cooker-,

" The ability of fats to ignite as a result of overheating cannot be, attributed particular~ to' any specific type of cooker since all cookers MVe

• .- the heating' capacity not, only to heat the fat to cooking temperatures but:'" also to overheat the fat to a temperature where it would spontaneously ignite.,, Moreover, dispersicns of fuel ,in air in the form of fuel vapour-air mixtures,

_ .. ~ fine sprays of :fuel, and froth or foam can be ignited both by a small gas; , flame or by a hot aurf'ace if the temperature of the latter is sufficient~

'"high, It might be"t~ought that if a fat is heated above the flash point on a,', , gas fired hob, the f1am~s might ignite the fat direct~ but this did not occur,

in any of the present tests., There might be a difference, however, between the" ability of a gas and an electric cooker to ignite a spillage of liquid fat at

. temperatures in the region of' the cooking temperature. For a stable flame to'form on the spillage as 'it passed through a' gas flame it would be necessary f'or

, • the spillage to be heated to at least the fire point. In the test .. spillagesof' up to a t ml in size could not be ignited when allowed to f'all through the'f'lames of'the gas appliance presumably for~the reason toot they could not beheated by the r-equfr-ed amount as they f'ell. The tests' also showed that the

, ,'temperatures reached by solid surfaces dUring the' normal use of the cooking';,appliances were considerably higher for both eleotrical hobs tested than the,y" were for the' gas hob tested. Moreover the temperatures of the sUrfaces of the'

,':, gas hob tested levelled out at values substantially less than that required to"', ignite a drop of' oil spontaneously, whereas the surfaoes of the electric hcit,: plates, tested could or did reach such a temperature.. . . .

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, ,·

Although these tests were carried out using only three cooking hobs, it'is unlikely that this picture of the maximum temperature of sUrfaces on the

r ' " hob would be very 'dif'ferent if' the range of' cooking hobs investigated were, extended, unless these incorporated marked changes in design, Broadly this

point m~ be summarised in the observation, that drops' of oil did not become, ignit'ed by .a hot sUrface unless this surface has reached a dull red heat. Ingeneral the hot metal parts of gas cookers do not reach dull red heat whereas,

: the hot metali'parts of eleotric hobs do often reach and exceed dull red heat.

•

, ,

"

,'.'

,,' Automatio temperature ~ensinfj devices'

Thus if' th, behaviour of the hobs tested is broadly representative of the'behaviour of cookers in' use, it may be concluded that an electric cooker ismore likely to ignite a spillage of hot oil in liqui~ form, than a gas cooker. ,It is possible that this might be responsible for some of the extra fires

" which the.available' statistics attribute to electric oookers, a Lbhough nodirect evidence of' this has been found f'rom recent reports from fire brigades•It 1's unlikely~ if' the fat in a pan is at ordinary cooking temperatures, thatthe ignition of eVEm a substantial spillage would bring about a directignition of the fat in the vessel itself'. A large momentary flame associated

" with a spillage, however, covJ.d ignite f'lammable material left carelessly• near or above the oook~.,

, '

" "-- There is, little doubt that many fires caused bi heating f'ats in a pan on'

a hob are a direot result of' the f'ats being oarelessly'allowed to overheat to'dJmgerous temperatures. Thus' of 750 reported fires caused in' 1957 by material

"

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~eing heated or cooked on an eleotric hot plate or ring; fat was thematerial first ignited on 649 occasions and,in 232 of these occasions it .was speoifioal~ stated that this,fat was left unattended on the cooker.f.~ tn~ ~@m~~~~a ~1 ee0asie~s ~be ~epQ~~s aFe ~et sPeoif~e en this Paint.It is clear'that if fat could be' prevented from overheating ,to a dangeroustemperature, then'a substantial reduotJon in the number of fires associatedwith cookers might be' achieved. The experimental evidence ,given in thisreport suggests that this might be done by providing a device on the hobwhich' automatical~ 'shuts off the power supp.Iy or the fuel suppIy onoe.the temperature of a pan exceeds by a predetermined amount the maximumcooking temperature for hot fats.' The resUlts presented in this'reportmay be regarded as reasonab~ representative of the bulk of ,fats used incooking and these resUlts show that for all these fats there issubstantial margin between the maximum temperature that might be required

,in any cooking oper-ation (20500) and a temperature at which a fat becomesimmediate~ dangerous as a fire hazard (3100C). If a pan sensor weredesigned to operate, for example, wi thin the range of temperature of220' - 2500C then on the one hand this should leave'an ample margin toallow oooking operations at the highest safe temperatures and on the other'

'hand an ample margin' before the fat reached temperatures whioh were .immediate~ dangerous. Pan sensors have been used for a number of yearsalready" for example, to prevent the boiling over of milk. The use ofsuch devices'for preventing fat overheating to a dangerous temperatureis ce~tirl~ just as feasible as' its use for any other' purpose, and thewide limits of temperatUre available for the device to operate for fatcooki~g wo~ld make its reliable design a less difficult task than itsdesign for other cooking operations•.

References

-.. '.

""

-,

, .

1. HOGG, JANE M. "Fires associated with electrio cooking:.applianoes".,'I Fire Research Technical Paper No.9..

2. United KingdotD Fire Statistios 1962."

3. United Kingdom Fire 'Statistios 1963~ .", "

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4. STARK, G. W. VO' "Some tests on the flaming 'properties of cookingoil. L, Ground nut oil".' Internal Note No.82. ~, A.

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"FIG.9, IGNITION TEST - GROUND. NUT OIL USED FOR COOKING - GAS RATE 16·7ft3/h

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FIG.11. TEMPERAJ"UR~S ON SOLID HOT PLAT~ HEATING RATE 2kW ..

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