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Fire Hazards and the Compartment Fire Growth Process : Outline of a Swedish JointResearch Program

Pettersson, Ove

1980

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Citation for published version (APA):Pettersson, O. (1980). Fire Hazards and the Compartment Fire Growth Process : Outline of a Swedish JointResearch Program. (Report / Lund Institute of Technology, Lund, Sweden, Department of Structural Mechanics;Vol. R80-5). Lund Institute of Technology.

Total number of authors:1

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LUND INSTITUTE OF TECHNOLOGY . LUND· SWEDENDEPARTMENT OF STRUCTURAL MECHANICSREPORT NO. R80-5

OVE PETTERSSON

FIRE HAZARDS AND THE COMPARTMENTFIRE GROWTH PROCESS-OUTLlNE OF ASWEDISH JOINT RESEARCH PROGRAM

LUND INSTITUTE OF TECHNOLOGY. LUND. SWEDEN

DEPARTMENT OF STRUCTURAL MECHANICS

REPORT NO. R80-5

OVE PETTERSSON

FIRE HAZARDS AND THE COMPARTMENT FIRE GROWTH PROCESS ­

OUTLINE OF A SWEDISH JOINT RESEARCH PROGRAM

Reprinted from FoU-brand (Fire Research and DevelopmentNews) No. l, 1980

l e 1980ranForskning och utveckling·brand • Fire Research and Development NewsUtges av Svenska Brandförsvarsföreningen med ekonomiskt stöd av Styrelsen för svensk brandforskning. Publisherl by The Swedish. Fire Pro;ection. Asso~iation withfinancial support by The Swedish Fire Research Board Kungsholms Hamnplan 3, $-11220, Stockhol.m.• Sw~den. Tfn. 08/5208. 40. U~glvareJPubhsher:. managmg dlreclorKjell Gunnarson. Redaktör/Editor: tekn lic Vilhelm Sjöiin, Styrelsen för svensk brandforskmng. AdmInistrativ re.daktorlManagmg ed!tor: 9un,,:,or Beije, SB.F/SFPA. Re­daktionsrAd/Editorial board: profe_ssor.Kai Qdeen, Kungl Teknis]<:a ..Hö.8skolan, Stockholm,. docent Harald Frosthng, Svenska Arbetsglvareforemngen, avdelningschef ArneWestlin, Arbetarskyddsstyrelsen, overlngenjor Lars Bergman, ForsakrIngsbranschens Service AB. Best nr 1243

Fire hazams and the compart..ment fire growth process... outline of aSwedish ioint research programBy Ove Pettersson1

1. NATIONAL SWEDISHFIRE RESEARCHPROGRAM

As has been reported in previous issuesof this journal, an expanded fire re­search program has been initiated inSweden [1] as a joint venture betweengovernment, insurance companies andprivate industry. Based on an extensivesurvey carried out whitin the NationalDefense Research Institute (FOA) [2],the present three year program (endingDecember 1981) is defined by 26 speci­fied research projects. These are nowin various stages of implementationunder the supervision of the establish­ed board of directors and a programsecretariat - the Swedish Fire Re­search Board. The overall programcovers most of the major research are­as: fire growth processes and spread ofsmoke and fires in buildings (sectorB), their impact on human behaviour(sector H) and on materials and pro­ducts (sector M), fire fighting and firedetection and extinction (sector K),systems and operational research (sec­tor S), and general and overall func­tions and surveys (sector F).

Admittedly, there is a considerablevariation in depth and scope. Naturallimitations in resources. and nationalcompetence necessarily led to projectspecifications in some cases merelyasking for further survey and feasibili­ty studies. One major sector where an

l Division of Structural Mechanics, Lund Insti­tuteof Technology, Lund, Sweden

active and extensive contribution al­ready has started concerns the area ofbuilding fire growth and spread in thepre-flashover stage. The aim of thepresentation given here is to outlinethe scope, contents and organizationof this particular effort and, in a fewcases, indicate some of the experiencesand results obtained so far.

2. SCOPEANDORGANIZATION OF AJOINT PRE-FLASHOVERCOMPARTMENT FIRERESEARCH PROJECT

Among the 26 research projects, con­stituting the national program, thefollowing four were thought to be in­terrelated to such a degree that greatadvantage could be gained by a combi­ned study, made simultaneously andin paraIleI.

The titles of these are• project B2: generation of smoke and

toxic gases,• project M3: surface lining materials

- c1assificationand fire hazards,• project M4: building materials - fi­

re tests and fire growth,• project M6: upholstered furniture

- fire safety requirements.The combined project has the title

"Fire Hazard - Fire Growth in Com­partments in the Early Stage of Deve­lopment (Pre-flashover)" and is carri­ed out as a joint project by the Divi­sion of Fire Technology and the Labo-

ratory for Chemical Analysis at theSwedish National Testing Institute,Borås and the Division of StructuralMechanics at Lund Institute of Tech­nology.

The ultimate goal of the project isto develop test methods in full orhalf-sized 'scale for surface lining ma­terials as weIl as for furniture andother fittings, from which the real be­haviour and contribution of the testedmaterial or product in a natural firecan be predicted. To achieve this goal,it will be necessary to develop andexploit theoretical analyses, based onreliable mathematical models for allthe fire processes, those making use ofinformation obtained from the testmethods and those processes descri­bing the fire itself, e.g. the flows ofgases and the energy transfers. Suchanalyses will also facilitate the formu­lation of functionally based require­ments and performance criteria. Animportant, paraIleI task within thecombined project is to evaluate thosesmall scale "reaction to fire" tests,being developed within ISO/TC921WG2 and 4, and to relate them to what

ContentllnnehållFire hazards and the compartmentfire growth process .

Systematiska brandplats­undersökningar . . . . . . . . . . . . . . .. 10

The department of fire safetyengineering at the Universityof Edinburgh. . . . . . . . . . . . . . . . .. 17

Fire behaviour of Roaf Structures forIndustrial Buildings 20

FoU-brand 1/1980

2

REDAKTÖRENUnder de senaste 20 åren har forsk­ningen kring bränders förlopp ochegenskaper i stort sett varit knutnatill brandförloppet efter övertänd­ning. Det är i det skedet som bygg­nadens bärande delar påverkas medrisk för brott och sammanstörtning.Forskningsinsatserna har varitframgångsrika. Undan för undanhar kunskapen ökat och burit fruktbl a i form av kvalificerade, ingen­jörsmässiga beräkningsmetoder.Ett stort steg framåt var byggnads­lagstiftningens godkännande avteoretisk beräkning som ett alterna­tiv till provning.

Emellertid formas brandensverkningar i stor utsträckning avbrandförloppets tidigare del. Detgäller särskilt verkan på människoroch på ömtåligare delar av bygg­nadskonstruktioner och inredning.Den tidiga delen av brandförloppetär dock ur forskningssynpunktmycket svår att hantera och förhål­landevis få mera omfattande ochdjupgående projekt har kommit tillstånd. Ett skäl härtill är att manmåste räkna med en stor satsning pålångsiktig kompetensutveckling in­nan man kan förvänta resultat förpraktisk tillämpning. Med den fi­nansiering som brandforskningentidigare haft i vårt land, har det va­rit svårt att garantera så stora an­slag under tillräckligt lång tid föratt göra satsningen meningsfylld.

Förhållandena har emellertidförändrats sedan BRANDFORSKtillkommit. En av dess första åtgär­der blev därför att bevilja medelför ett stort projektblock av ny ka­raktär. Härigenom har Institutio­nen för byggnadsstatik vid Lundstekniska högskola i samarbete medbrandlaboratoriet vid statens prov­ningsanstalt kunnat påbörja ett tre­årigt projekt - "det tidiga brand­förloppet" . De båda forskningsin­stitutionerna har genom att skjutatill egna medel kunnat disponera ca4 miljoner kronor t o m 1982. Pro­jektet stöttas ytterligare av formali­serat samarbete med Fire ResearchStation i Storbritannien och genominformellt samarbete med andra ut­ländska institutioner och organ.

Professor Ove Pettersson redo­gör i artikeln för projektblocketssyfte och innehåll. Artikeln publi­ceras på engelska som ett led i an­strängningarna att tidigt orienteraomvärlden om vad som pågår inomden svenska brandforskningen. Envidare orientering för det svenskabrandförsvarets personal förberedsi annan form.

happens at real fires. Undertakingsuch a project, will have a significantrole in increasing the national fire re­search competence.

Tackling such an extensive andcomplex research area, an effective co­operation between research graups be­comes a necessity. On the national le­vel, an agreement to co-ordinate andco-operate in work within fire researchwas signed in 1978 between the Swe­dish National Testing Institute (SP)and the Fire Research Group at LundInstitute of Technology (LTH). As aconsequence, the application for theresearch grant sent to the Swedish FireResearch Board was a joint one and di­rectly based on a factual and conti­fillOUS cooperation.

Internationally, documents outli­ning joint research interests betweenthe Fire Research Station (FRS), UKand LTH has been agreed. This colla­boration will be focused on problemsin the growth of fire in compartmentsin the early stage of development (pre­flashover). Extensive discussions andconsultations have taken place withFRS and form much of the back­ground for the formulation of the re­search project, presented in this artic­le. Chapter 3 is largely based on theoriginal letter of intent for theFRS/LTH co-operation.

Il should also be mentioned the roleplayed for the project by the informa­tion dissemanating from the NationalBureau of Standards (NBS) inWashington. A number of people havewillingly discussed projects in pro­gress, given access to unpublished da­ta, to computer programs and in otherways facilitated our work. Furthermo­re, the activities going on within theAd Hoc Fire Mathematical ModelingCommittee in USA and within ClBWI4 - pIanning to. organize a workshop on pre-flashover fire mathemati­caj modelling during 1981 - will con­siderably support the research project.

3. GENERALBACKGROUND OF THERESEARCH PROJECT

Traditionally, efforts to increase thefire safety in buildings have been di­rected towards requirements on struc­tural components and - to alesser ex­tent - also to building materials. Fur­nishings and other non-structural fea­tures of buildings have until recent ti­me remained essentially non-regula­ted. Il is now widely recognized thatan increase in human firesafety levelsrequires an assessment of the roIe offurnishings and other building con­tents. Consumer demands in a numberof countries have resulted in efforts tocontroi the flammability of furnishingby statutary or non-statutary require-

ments. The material or product selec­tion is almost invariably related toperformance in a specified small scaletest method. As of now, the relation­ship between the behaviour of mate­rials in a test and in a real fire, afterthe initial ignition, remains unknownin any general predictive sense. Awealth of data is gradually becomingavailable regarding ignition times, fla­me spread velocities, burning intensiti­es, radiation output and so forth, butthere is no satisfactory comprehensivetheory of furnishing fire behaviour onwhich to base design or predict hazard.To a large degree, this also applies tothe roIe of internai linings in the resi­dential fire process. The problem isaggravated by the new materials andproducts being continually developed,expanding the range of fire responsesand performance charactetistics.

Fire science and technology are at­tacking the mountain fire problem bya number of avenues. In the area of in­ternal linings, standard laboratory fi­re test methods are being designedwhich measure the quantitative re­sponse of a material to specified fireexposure situations. Examples are the"reaction to fire" tests being develop­ed within ISO/TC92/WG2 and 4. Byoperating at a number of exposure le­vels, these tests will provide a compre­hensive, quantitative description of ba­sic fire performance characteristics (ig­nitability, surface flame spread, rateof heat release). Simultaneously, ini­tial but nevertheless extensive effortsare being made to mathematically mo­del fire process dynamics, in a numberof areas, to determine the dominantcontrolling mechanisms. Examples ofimportant subrnodels or aspects of thefire growth phenomena are• field and zone models for part tur­

bulent flows in enclosures,• fire growth models (flame spread

under arbitrary externai radiation),• characteristics of flame and hot gas

radiation,• convective heat transfer through

ventilation openings,• convective heat transfer within en­

closure.The modelling problems inherent in

the list of transient, thermophysicalprocesses enumerated above will notbe solved in detail for many years tocome. One of the major problems willbe to strike a proper balance betweenthe need for reasonably quick answersand the need for modelling accuracy.Tools to complement the analyticalmodelling comprise experiments infull or small scale, reliability studiesand empirical data from standardtests. Attempts at interpreting stan­dard tests by modelling them alsohelps to extract data from (hem in themost useful way for wider application.

FoU-brand 111980

Table l. Scheme of integration for the eleven research items of the total pre-flashover research project

Research item Project

B2 M3 M4 M6

1. Analysis of SIS 02 4823 (Swedish box test) x x x2. Bum room sensitivity study x x x3. Fire behaviour of surface Iining materials - full

scale testing x x x4. Fire behaviour of upholstered furniture - full

scale testing x x5. Interaction between buming items of furniture

and combustible surface lining materials - fullscale testing x x x x

6. Pilot studies of fire induced compartment flows x x x x7. Mathematical fire modelling x x x x8. Development of methods for analyzing

combustion products of polymeric materials x x x x9. ISO reaction to fire tests - correlation to real

fire, dassification x x x10. Development of standardized full scale tests

(a) Surface Iining materials x x x(b) Furniture x x

11. Testing of upholstered fumiture using half-scalerigs x x

3

EDITORIAlSo far, most of the research on fireshas been dealing with the fire situa­tion after flashover. This is notsurprising, as the fire effects on theloadbearing structural elements ofthe building, will be imposed du­ring this stage of a fire. In lateryears, however, extensive researchon postflashaver problems hasopened the way for an analyticalstructural fire engineering design,based upon well-defined functionalperformance criteria.

However, there are good reasonsto pay more attention to the earlystage of fire. A threat to humanswill certainly become eminent al­ready before flashover. Furthermo­re, in many cases, the early deve­lopment of a fire will determine thefire loss regardless of later damageto the loadbearing structural ele­ments. With this background, it isnot difficult to see the reasans forthe present worldwide trend in fireresearch to put more emphasis onthe early stages.

The Swedish Fire Research Boardis a new initiating and sponsoringbody in the field of fire research. Itis founded and funded by the Swe­dish Government and by privateenterprises on a 50-50 basis.Oneof its first undertakings was toestablish a block of projects aimedat studies of the early stage of fire.

In this artide, professor Ove Pet­tersson of the Lund Institute ofTechnology tells about the inten­tions and scope of the work. Theprojects are conducted in ca-opera­tion between the Institute and theFire Technology Laboratory of theNational Testing Institute. Bypooling financial resources, closeto U.S. $ one million has been setaside for a period of three years.The work indudes considerable in­ternational collaboration.

A short term goal may be a predicti­ve model of whether or not flashaverwill occur for a given set of initial con­ditions, and, if so, how long after igni~

tian it will occur.Our increasing capability in con­

structing physical or mathematicalmodels for important fire scenariosimplies that rationai approaches to es­timate life safety levels will graduallybecome avallable. The life safetyproblem must be approached by me­thodologies now being used within anumber of other sectors for assessingefficiency, sensitivity to disturbanceand reliability in complicated systems.Examples of analytical tools are pro­bability theory, variance analysis,

FoU-brand 1/1980

mathematical programming (linear l

dynamic), decision analysis, systemssimulation. Most of these methods ha­ve been used previously in one form oranother in the field of fire research.The choice of method has usually de­pended on the design level, 1.e. on thesize and complexity of the system in­volved.

4. DETAll STRUCTURE OFTHE RESEARCHPROJECT

For a more detailed planning of thetotal research project, it turned out tobe useful to break down the project in­ta eleven smaller research items. Tab­le lenumerates these items and illu­strates their relevance for and connec­tion to the four original research pro­jects B2, M3, M4 and M6 in the natio­nal Swedish fire research program.The different research items are not di­rectly comparable in regard to extentand complexity. One research item ­analysis of the Swedish box test - israther lirnited. Same other items be­long to very fundamental researchareas with a high degree of complexi­ty, for instance, items 6 and 7. For the­se items, the level of ambition for ajoint Swedish contributian naturallymust be limited to give only a few mo­dest complements to the comprehensi­ve international research develop­ment. Accordingly, Table 1 must bemadeconcrete in order to give maredetailed information on the scope andlevel of complexity of the different re­search items.

The remainder of the paper will beused to present the eleven research

items as weIl as the progress made upto now (August 1980). As will be no­ted, none of them is anywhere nearcampietian, most are still in an initialplanning stage.

4.1 Research Item 1.Analysis of SIS 02 4823(the Swedish Box Test!

The standard instrument in Sweden fora fire c1assification of building liningmaterials is the so called box test. Thetest configuration has features similarto the British fire propagation test andthe Dutch flashover test, the majordifference being that the ventilation iscontrolled in the Swedish box test.The material to be tested is attached tothe ceiling and three walls of a smallenc10sure and exposed to a ratherstrong gas flame without any additio­nal impressed radiation. Materials aregraded by the time curve o f the fluegas temperature with three specified li­mit curves.

1t is known that material fire pro­perties, for instance, mass buming rateper unit surface area, varies widely,and in many cases non-linearly, withthe level of thermal exposure. The va­Iue of the test as a measure of the con­tributian of lining materials to the firegrowth and spread could thus be con­siderably enhanced, if the exposure le­vels during the testing process are mea­sured and compared with those genera­ted in common natural compartmentfire scenarios. Useful information willa1so be gained byarnare completeeriergy balance study of the test pro­cess, giving the rates of heat outputand heat transfer within the enc1osure.The practicality of using oxygen con-

sumption calorimetry to measure thequantity of energy release by combus­tion will also be studied.

The investigation will be carried outat SP during autumn and winter 1980.

KEI(;KT (m1

"

IolASS FLOW

(kg!5)

KEI(;KT (m)

"

tiO T;me(mj~_!

&O Time(min}

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"

..

OIFFEREHCE

,.o+---~--~--~--~-_o

precise: Given a fire source withknown heat output near a wall,what will different classes of walland ceiling surface materials meanin terms of time to untenable situa­tions inside the room, time to flash·over, etc?The Swedish full scale method for

surface finishes now in use was initial­ly modelled on the room-corridor firespread situation. Being developed inthe late 1950's, the test method inevit­ably has some inherent drawbackswhen measured against modern stan­dards and requirements. The test pro­cess may be sensitive to changes inweather conditions. Acceptance crite­ria are not firmly quantified but of arather subjective nature. The test pro­cess has not been correlated to one­room fire growth scenarios.

As an alternative test procedure, thecorner test was an obvious candidate j

and the burn room at SP is being usedfor development work on a room cor­ner test. To find suitable fire scena­rios, a series of tests were ron with va­rious surface finishes. Heptane bur­ners of various sizes were used and se­veral sizes of the opening of the com­partment were tried. The burners wereopen containers with water and hepta­ne floating on top. Materials to be tes­ted were mounted on walls and cei­ting.

000

Figure 3. Measured rate of heat loss byconvection Qa versus time. StationarYconditions. Test I: Qe = 125 kW. TestII:Qe = 250kW[3]

'"

EFFECT

(kW)

"

'"".

lHFLOW

,.o~

Figure 2. Measured mass flow in andout of fire compartment and the diffe­rence of these values versus time.Qe = 250kW[3]

1.0 2.0

~:/~F~~r

o.,

-2.0 -1.0

(a) 0c = 125 kW

o, j-Z.O -1.0 o-~,-o~Z'_O

~ASS FLOW(k,,/5 m Z)

bl Qe" 250 kW'.0

(b) Oc = 250 kl.

Figure 1. Mass flow profiles in thedoorway at two rates of heat releaselevels [3]

4.3 Research Item 3.Fire Behaviour of SurfaceUning Materials - FullScale Testing

Recently, the Swedish regulations re­garding the use of surface finishingmaterials were substantially extendedto cover new classes of buildings (es­sentiaIly, one family homes) and inte­rior surface areas, which previouslyhad not been regulated. The minimumrequirements for all surface finishingmaterials, sold to the consumer, arethat their flammability characteristicsmust give at least equal safety as thoseof massive wood, when tested in theSwedish hot box.

The extension of governmental re­gulations brings a renewed urgency tosome old and only partial1y solvedproblems regarding a functional clas­sification of surface finIshes. Amongthese are

• to what extent is the classification ofa surface material dependent on thechoice of base or backing material(degree of combustibility, value ofthermal inertia)?

• what is the relation between theclassification of a Iining material inthe box test and the contribution ofthe same material to room firegrowth and spread? Or to be more

4.2 Research Item 2.Burn Room SensitivityStudy

A full scale experimental burn roomhas been built and instrumented at SP.It will serve several functions duringthe project, viz.,

• to establish basic f1ame spread andcombustion characteristics of liningmaterials as well as furnishings (up­holstered furniture) under full scaleconditions,

• to serve as basic configuration for aroom corner test,

• to serve as a room size calorimeter.

The instrumentation basically fol­lows the "Recommended Practice forRoom Fire Test", issued by ASTME-39.101, the main difference beingthe number of bi-directional probesfound necessary to map door f10wconditions.

An extensive energy and mass ba­lance calibration with gas burner asfuel source has been carried out andsummarily reported in [3]. Energy, re·leased by combustion in the fire room,leaves the room by convection and ra­diation through the doorway and byconduction through the surroundingstructures. The object of the calibra­tion tests was to evaluate the variouscomponents at heat transfer and esti­mate the accuracy of the measure­ments by checking the heat balance.

In a first series of calibration experi­ments, gas velocity or rate of massf10w and temperatures were measuredonly a10ng a vertical line in the centerof the doorway. Considerable diffe­rences between calculated total rate ofmass f10ws in and out of the fire roomwere, however, registered because thehorizontal distributions of gas velocityare different in the f10ws in and out.

A second series of experiments wastherefore made where the horizontaldistribution was investigated. Themass flow and the temperature werethus measured in 66 points over thedoorway.

Examples of the vertical mass flowprofiles are shown in Fig.1 - the massf10w is integrated horizontaliy overthe doorway. Fig. 2 shows an exampleof the measured mass flow in and out,integrated over the doorway, and thedifference between these two as a func­tion of time. The total rate of energyf10w Qa out of the compartment, in­tegrated over the doorway, is given inFig. 3. As shown by Fig. 2 and 3, theaccuracy of the measurernents is satis­factory.

4

<2 min.

2 min,6 min,

20 min,

• to estimate the time available for es­cape or evacuation out of the roomof fire origin, Le. the minimum timefor a hazard component (heat, smo­ke or toxic gas concentration, heatfluxes) to reach untenable condi­tians,

• to validate the results obtained bysimulation computer programs. Inour case the Harvard Computer FireCode [5J and a time-dependent ver­sion of the Quintiere model, deve­loped at FOA, Stockholm [6J wereused,

II to find correlation with experimentscarried out with a prototype scaleddown test rig (see further researchitem 11).

As an example of the results derivedin [4], Fig. 4 gives for five differentmaterial combinations the total, accu­mulated smoke production Dacc as afunction of time. Dacc is expressed, inaccordance with the terminology usedin [7J, as (dB/m) . m', where the firstfactor expresses light attenuation asdecibel per m of light path through theoutflowing smoke, and the second oneexpresses the total flow of combustionproducts (smoke). Table 2 gives de­tails of the material combinationsused. Fig. 4 clearly illustrates the in-

®

t 000

2000

:::: jr

5000

4000 ~l

3000 J

Development, has been carried out inthe previously mentioned burn roomat SP and been preliminary reported[4J.

To get reproducible fire scenariosand clearly defined and measurablereactions to variations in the main pa­rameter, Le. material selection, thetest furniture was a full scale mock upmodel of a three-seat sofa, designedwith loose cushions on a steel frame.A liquid fuel burner with a heat out­put of 20-30 kW was used as ignitionsource.

The materials of the cushions waschanged in a systematic way to repre­sent the ranges available in the consu­mer market. In all, Il sofas were test­ed. Extensive measurements were ta­ken of mass burning rates, gas tempe­ratures, gas flow velocities, heatfluxes to floor and ceiling, smoke con­centration and gas species concentra­tians.

The experimental data have beenprocessed and analyzed for a numberof purposes, viz.

• to assess basic components of therisk profile of the product (rate offire spread, maximum rate of heatrelease, concentration of producedsmoke),

A square burner with a surface of0.03 m' gives approximately a rate ofheat release of 50 kW, thus simulatinga burning waste paper basket. Whenthe burner was placed in a corner, thefollowing time intervals between igni­tion of the burner and flashover (de­fined here by flames coming out of theopening) were recorded

" untreated porous board• chip boardIl surface veneer, bonded to

chipboard• polystyrene foam, flame

retardant

With the same test conditions, thefollowing products did not causeflashover

• plaster board,• PVC-wallcovering, on plaster

board,• traditional wall-paper, on non­

combustible board.

The PVC wall paper was also testedwith smaller openings and with a lar­ger burner; on no occasion did flash­over occur.

To complement the full scale studi­es, a series of room corner tests in mo­del scale has been planned. Some pre­liminary tests have been performed ina cubic room with dimensions I x l x lm' for a study of ignition, fire growthand flashover at different combina­tions of wall and ceiling linings, madeof wood or wooden-based products. Agas burner. placed in a corner. wasused for simulating a scaled-down,representative thermal exposure. Tem­perature, gas velocity, heat flow andheat radiation were measured. In thefollowing tests, the measurement sys­tem will be expanded with an oxygenconsumption calorirneter for a deter­mination of the energy, released bycombustion. An evaluation of the re­sults of the preliminary tests is inprogress.

Table 2. Material combinations nsed in full scale tests of upholstered furniture

Figure 4. Total, accumulated smoke productian Dacc as function of time fortests 5, 6, 7, 8 and 11 [4]4.4 Research Item 4.

Fire Behaviour ofUpholstered Furniture ­Fuil Scale Testing

The overall objective of project M6 isto study the fire behaviour of uphols­tered furniture to assess the hazards,associated with ignition, growth of fireand production of smoke and toxic ga­ses. A major element is developmentand validation work to produce func­tionally based fire tests ..Research item4 in particular comprises a study of thefull scale burning characteristics ofupholstered furniture, as influencedby the choice of upholstery Jabric, in­terlining and filling material. A firststudy, financed by the industry and theNational Swedish Board for Technical

Test No.

l23

45678

91011

Upholstery fabric

Acrylic 1000/0Acrylic 100%Acrylic 100%

Woolloo%Acrylic 100%Wool61 "lo, viscose 39%Wool61 "lo, viscose 39%Wool61 "lo, viscose 39%

Wool61 "lo, viscose 39%Wool61 "lo, viscose 39%Woo161 "lo, viscose 39%

Interliner

FirendVonarKynol

FiIling material

ConventionaI polyurethaneConventional polyurethaneConventionaI polyurethanewith FR additivesConventional polyurethaneConventionai polyurethaneConventionai polyurethaneHigh-resilient polyurethaneConventionai polyurethanewith FR-additivesConventionai polyurethaneConventionai polyurethaneConventionai polyurethane

FoU-brand 1/1980 5

Figure 5. Smoke producing potentialper unit weight of eonsumed fueJ Do asfunetion of time for tests 6, 7and 8 {4}

fluenee of material selection on the ra­te of smoke production.

An effort was also made to examinehow the quantity Do, (dB/m) . (m' /g),expressing the smoke producing poten­tial per unit weight of consumed fuel,varied over the fire process. A constantvalue of Do obviously would providea convenient way of classifying mate­rials. Unfortunately, as shown by Fig.S, Do varies strongly and shifts ran­king order during the fire process.

4.5 Research Item 5.Interaction betweenSurning Items ofFurniture andCombustible Surfacetining Materials ~ FullScale Testing

This item should be studied at the endof the three-year program, when re­sults from items 3 and 4 are availableand have been analyzed.

4.6 Research Item 6.Pilot Studies of FireInduced CompartmentFlows

Througout the series of full scaletests, which will be carried out forother, primary objectives, velocitymeasurements will be taken of the gasflow field inside the fire compartment(upper gas layer) as well as in the ven­tilation opening. The instrumentationwiU be based on the use of bi-directio­nal probes, and one purpose will be totest the accuracy and speed, espedallyin highly transient compartment fires,of the measurement system. Other pur­poses include the need to check the li­mits and definition of the controi vo­lume concept now used in the zane

6

modelling approach. In particular twoidealisations need further examina­tion. The first is the concept that thefluid in the fire room is stratified intotwo horizontal layers of uniform tem­peratures with no mixing. The investi­gations in [8J imply that secondary andrecirculatory flows near the enclosureopening may be an important cause ofreducing the oxygen concentration ofthe combustion air and hence the massburning rate. The second concept is theone of a ventilation outflow, driven bya hydrostatic pressure distribution andwithout influence from the kineticenergy of the rising fire plume gasflow. These two approximations con­cern the basic problem of predictingthe temperature rise in the upper partof the enclosure and the concentra­tions of combustion products and un­burnt fuel, and the way the fire inter­acts with the enclosure. In addition,measurement~ taken under researchitem 2 are being used to compute an ef­fective flow coefficient. It is importantto investigate how the flow coeffici­ents vary with the range of size of ven­tilation openings and fire sourcestrengths, encountered under practicalconditions.

4.7 Research Item 7.Mathematical FireModelling

The developments, taking place in thelast five years within the area of com­puterbased simulation of the enclosu­re fire process, has led to a number ofmedels for common fire scenarios.The range of practical application aswell as the predictive capability of the­se models is steadily increasing. Themore recent developments were sket­chily summarized in a review report tothe 1980 CIB WI4-meeting in Athens[9].

In [9], available models were, some·what arbitrarily, divided into generalpurpose enclosure fire models (theQuintiere model and its successor [6]),models of growth of compartment fi­res involving combustible lining mate­rials, models for a specified applica­tion - such as early growth of the clo­sed room fire or the ventilation requir­ed to perrnit sustained burning orgrowth of compartment fire - and, fi·nally, models for a simplified predic­tion of room flashover. Other impor­tant modelling areas include probabi­listic models for fire spread, model­ling of laboratory scale tests, model­ling of essentially micro'scale firephysics (ignition, flame spread, extinc­tion), see e.g. the very recent survey in[17].

The research group expects to parti­cipate actively in the efforts takingplace within the cm framework to vi­talize and co-operate with the Euro­pean work on fire modelling.

The specifications for project M4emphasizes the need for establishing anational competence in this sector offire research. Within the project, theefforts will be concentrated on twotasks.

With the kind assistance of NBS andthe Harvard Fire Research Group, ver­sion four of the Harvard computer firecode [5J has been transferred to LTH,and is now being used to simulate thefull scale tests, mentioned under item4. Simultaneously, the predictive ca­pacity of the FOA simulation programFLASHOVER [6J for this kind ofcompartment fires is being looked in­to.

The second task concerns a modelfor the prediction of wall fire spread.Very recently, important elements ofan analytical model describing the fla·me spread process across a combustib­le wall were for the first time outlinedby Quintiere [JO]. An effort will bemade to couple the experimental dataproduced in the model and full scaletests under research item 3 with theongoing efforts to put the mathemati­cal modelon a firmer base.

4.8 Research Item Il.Characterization ofCombllstion Productsfrom Small and Full Scalelaboratory Fires

The overall responsibility for this partof the total project will be with theLaboratory for Chemical Analysis atSP. The primary aim of the researchtask is the development and calibra­tion of a measurement system, basedon gas chromatography and massspectrometry, to analyze the combus·tion products from laboratory fires.These can be generated in small scalestandard tests such as the Swedish boxtest or the Smith RHR apparatus asweil as by full scale experiments usingthe burn room. In the first year, thesystem will be assembled and calibra­ted, while the second and third year.will be used to qualitatively and quan­titatively identify possible toxic spe­cies from a number of natural andsynthetic polyrneric materials, withand without fire retardant additives.

4.9 Research Item 9.ISO Reaction to FireTests ~ Correlation toReal Fires. Classif/cat/on

The procedures available for predic·ting fire hazard from small scale testsare outlined in the ISO Technical Re-

FoU-brand 111980

with

V-I/2 = C(q' ". - q' ")f O,lg e

V·1!2 - CI (T T)f - 19- s

Tig effective ignition temperature,and

Ts surface equilibrium temperatu~

re.

The development of standardizedfull scale tests for furnishings, e.g. up­holstered furnitures and beds, for thepost-ignition phase, is in a still moretentative stage of development.

A number of factors determine thehazard profile of a specified product,involved in the post-ignition stages ofa room fire: flame spread and firegrowth properties in general, maxi­mum rate of combustion heat release,generation of smoke and toxic gases.The components in the first and thirdcategory determine the time availablefor safe escape, while the maximumrate of heat release indicates the risk ofroom flashover and spread to otherrooms. The flashover phenomena ha­ve been the subject of a number of re­cent papers and certain quantified li­mit criteria have been proposed. Theother hazard components, acceptancecriteria cannot yet be determinedobjectively.

The most extensive work has pro­bably been carried out in the UK and,by way of an example, resulted in a se­ries of "fire retardant specifications",issued by DOE/PSA [14]. One of the­se, DOE/PSA. FR 6, tests the burningcharacteristics of upholstered chairsby a burn-out test in an instrumentedroom. Data collected during the testinclude smoke temperature, opticaldensity and volume, heat fluxes to theenvironment and CO-concentration.

To test, for instance a full scale pie·ce of an upholstered furniture in a ful­ly instrumented burn room, using ca~

lorimetric measurements and energybalance equations, involves a con­siderable amount of time and east. AI­so, as long as effective ventilationflow coefficients are not available as afunction of opening geometry and heatsource strength, the number of veloci­ty probes necessary for accuratelymapping highly transient gas flow ve­locity fields makes for a rather un­wieldy test procedure. An attractivealternative in this situation is tOtiseoxygen consumption techniques [13 J.Still another approach is the room sizedynamie room calorimeter, developedat Monsanta [15], working under for­ced air flow conditions. The impact onburning characteristics of the artificialflow system may not be negligible,however. As a further alternative andif the influence of the enclosure on thefire growht process is of minor impor­tance, pieces of furniture could be tes­ted by free burning under an exhausthood and with rate of heat releasemeasured by oxygen consumption.

The problem of enhancement ofburning rate by thermal feed back,from enclosing structures and uppergas layer, was investigated by Thomas[16], who found that the ratio of rateof burning at the flashover point for a

is a material parameter, includ­ing radiation from flame, effec­tive width of this radiation,thermo-physical properties,is minimum radiation flux forpiloted ignition, andis the imposed radiation flux.

q~,ig

where

c

q;

4.10 Research Item 10.Standardized Full ScaleTests

This research item is considered one ofthe more important part objectives ofthe total project. Experience has clear­ly demonstrated that small scale labo­ratory tests may give mislcading andeven erroneous information regardingmaterial or product performance in anatural fire. The need for further fullscale studies, using internationallystandardized procedures, where pos­sible, is thus direct and urgent. Thisapplies to surface lining materials asweIl as furnishings.

For surface lining materials, initialdevelopment work has been describedunder research item 3. The work beingcarried out in the USA to produce anASTM room corner test is being clase­ly monitored [13J.

Quintiere also shows how values ofC and q".ig may be determined for aspecific material from a single test runwith the surface spread of flarne appa­ratus. Values of q".ig can also be ob­tained by imposing a uniform fluxover a smaller sample.

For a thermally thick material, the­re is a unique relation between q~ andthe corresponding equilibrium tempe­rature. This implies that an alternativeexpression for Vf is

A key element in the Quintiere con­ceptual quasi-steady model for wallfire spread is a simplified theoreticalmodel of surface spread of flame un­der sup·porting radiation, such as canbe studied on the equipment being de­veloped by ISO [12]. A simple expres­sian for the horizontal flame spread V,as may OCCUr in a corner test fire canbe theoretically derived if the materialis preheated so that its rear surface isstill cold when the front face hasreached thermal equilibriurn, viz.

port TR 6585 "Fire Hazard and De­sign and Use of Fire Tests". October1979 and in [16]. In the absence of ana­lytical models for a standard testand/or the full scale experiment,multi-dimensional regression analysiscan be used to correlate test resultswith values of specified full scale ex­periment variables (maximum roomtemperature, time of flashover, etc).On the other hand, an analytical mo­del of the small scale test dynamicscan provide information on a numberof important aspects. Identification ofthe test sample characteristics (area,orientation, exposure conditions),which contral the test outcome, formsthe basis for numerical simulationsand a sensitivity analysis of the testmethod itself. With a mathematicalmodel of the test dynamics to hand,important material characteristicscontrolling fire growth can be givenquantitative values, which then can beused as input for full scale. This pro­cedure .would be of value, especiallyfor non-homogeneous materials, whe­re relevant material properties, likethermal inertia, otherwise might notbe obtainable.

The research group participates acti­vily in ongoing development and vali­datian work on the ISO reactian to firetests. The apparatus for ignitability,surface spread of flarne and smokegeneration is being evaluated at SP. AtLTH, calibration work is now beingdone on the rate of heat release (RHR)apparatus, designed by Prof. Smith atOhio State University. The apparatusis instrumented to measure the rate o fheat release by convective heat flowasweIl as by oxygen consumption.Among the problems likely to be en­countered, if basic data are to be ob-

tained for wide use, is the fact that theapparatus, designed to work duringtests at constant levels of impressedradiation, progressively heats up andincreases the thermal exposure [Il].

Other RHR standard tests under de­velopment include an unconfined de­sign configuration. To this group oftest methods belongs the NBS rate ofheat release test, based on measure­ment of the oxygen depletion. A grantfor a further study of this test has beengiven to the Swedish Forest ProductsResearch Laboratory.

Also the Swedish box test, cf. itemI, may be considered as a crude proto­type to a RHR test method.

If a given material is being testedwith the three methods mentioned, thetest results will certainly differ. Anunderstanding of the differences in thetest processes will help to provide a ra­tional explanation of the divergencesas weIl as of the relation between thetest methods and the natural fire pro­cess.

7

1500

oL..l"-"...L..l....lL.J:'--"''''--''--''-.L-'--..JL.L..J=-'--.b.L-'''--''..L..JL.L..J=_~

TESTNo 2 3 5 6 7 8 9 10 11 13 l' lS 16 11 18 19 2011 12 2' 2S 26

D ConvenlLonolpolyurelhone

1000

500

fire in an enc10sure to the rate of bur­ning when the same product is allowedto burn freely in the open, is nearly aconstant '" 1.7. The implications arethat results from a free burning test,indeed can be used to indicate the riskfor the same product causing roomflashover.

Finally, as our own and others expe­riments have demonstrated, a test toassess the horizontal flame spreadproperties of furniture with extendedsurfaces remains essential both to pro­vide basic input data in computer-bas­ed mathematical models of enclosurefire growth and as a more direct riskelassification tool. As pointed out in[16], fire spread may be more suscep­tible to radiative enhancement thanpure rate of burning.

r------------IIL~,

\\

\\\

\

Table 3. Total accumulated smoke production Dacc for upholstered fumiture,obtained in half-scale and full scale tests [4J

Figure 7. Total, accumulated smoke produetian Dacc for pieces of upholsteredfumiture, determined in ha/f-sca/e tests. In the tests, not reported in the figure,the smoke produetian was to small to enable any eva/uation [4]

39 40 'l 42 43 ,s 46 47 48 SO 51 S2

17T p-

17 17'/

/ 1/ // 1/ 1/ 1/ // V 7 1/

"XV /

r- / V / V 1/r; // " V / / '" V /~ r '" - '"V V V '/ V /

~

"-

" I- '" ~ "V"

V'" ~

/

" F:; V"

1/

"V"

'/

'" '/

" ~ /

"V ~

V"

'/"7" V j "X '"/

"V

'"1/ / 1/ / 1/oTEST No 21 28 29 31 32 33 3' 3S 36

500

1000

1500

r-------------IIIII

r~

J/

// .,

//

/

4.11 Research Item 11.Testing of UpholsteredFurniture UsingHalf-Scale Rigs

It follows from the discussions underresearch item 10 that obvious advanta­ges would be gained, if testing of pie­ees of furniture could be made on spe­cimens of a reduced size.

As a part of the project, brieflydescribed under research item 4, anumber of burning tests (52) were per­formed with a testing rig designed ac­cording to DD 58:1978, the originalproposal for a British ignitability stan­dard. The test configuration is describ­ed by Fig. 6.

@ PHOTOCELL • THERMOCOUPLE

o GAS FLOW MEASUREMENT

Half-scale Full scale

Test No.

2530208039056910

465603639

1296

Smoke production Dacc ('!!f . m')

Half-scale Full scale

5678

1464847

LOAOING/CELL

Figure 6. Arrangements for testing up­holstered fumiture, using a ha/f-sca/erig.

To illustrate the results obtained,Fig. 7 outlines the range in total accu­mulated smoke production Daee, ob­tained by material changes and modi­fications. Finally, Table 3 gives thecorrelation between full scale and mo­del scale testing for those few caseswhere results are obtainable.

The table indicates a positive corre­lation but shows simultaneously thatthe relative ranking order is not unam­biguous. Before more definite conelu­sions can be drawn, further tests mustbe carried out.

5. SUMMARYThe following four projects from thepresent National Swedish fire researchprogram

• generation of smoke and toxic gases(B2),

• surface lining materials - elassifi­cation and fire hazards (M3),

• building materials - fire tests andfire growth (M4),

• upholstered furniture - fire safetyrequirements (M6)

have been brought out and integratedto a research project with the tille "Fi­re Hazards - Fire Growth in Com-

8 FoU~braD~ 1/1980

partments in the Early Stage of Deve­lopment (Pre-f1ashover)". The inte­grated project is carried out as a jointproject by the Division of Fire Techno­logy and the Laboratory for ChemicalAnalysis at the Swedish National Tes­ting Institute (SP), Borås and the Divi­sion of Structural Mechanics at LundInstitute of Technology (LTH). With­in the frarnework of a collaborationagreed between the Fire Research Sta­tion, UK and LTH, extensive discus­sions and consultations have takenplace and are forming much of thebackground for the formulation of theresearch project. The project is finan­ced by the Swedish Fire ResearchBoard.

The paper presents the generalbackground, scope, organization anddetailed structure of the integrated re­search project. In order to facilitatethe detalled planning, it turned out tobe useful to break down the project in­to eleven smaller research items.Table lenumerates these and illustra­tes their relevance for and connectionto the four original research projectsB2, M3, M4 and M6 in the nationalSwedish fire research program.The maln part of the paper is devotedto a presentation of the eleven researchitems as weil as the progress made upto now (August 1980). As it appears,none of them is anywhere near com­pletion, most are still in an initialplanning stage.

The final goal of the project is de­fined as the development and valida­tion of test meihods, for surface liningmaterials as weil as furnitureandother fittings, having the capability ofpredicting the behaviour and contribu­tion of the tested material or productto natural fire growth and spread in acompartment. In order to achieve thisgoal, analytical modelling of thecompartment fire process becomes anecessity, e.g. as a tool to perform sen­sitivity studies; In this sense, the use ofmathematical models a1so facilitatesthe formulation of performance-basedclassification requirements. Specifi­cally, evaluation and verification ofthe ISO reaction to fire tests representsan important task.

ACKNOWlEDGEMENTDr Philip Thomas,Fire Research

Station, UK, has generously contribu­ted in consultations and discussions,giving a decisive influence on the for­mulation of the research project, pre­sented in this article. He has a1so acti­vely followed and given advice on in­dividual research items of the project.

All participants in the research pro­ject wish to express their hearty thanksfor this support and look forward to astimulating future co-operation.

REFERENCES[I] FoU-brand (Fire Research and

DevelopmentNews),1·1979.[2] FoU-brand (Fire Research and

Development News), 2·1979.[3] Sundström, B. and Wickström,

U., Fire: Full Scale Tests ­Background and Test Arrange­ments, Technical Report SP ­Rapp 19S0:14, Borås 19S0.

[4] Andersson, B. and Magnusson,S.E., Fullskaleprov - Brand istoppmöbler (Full Scale Tests ­Fire Behaviour of UpholsteredFurniture), Byggnadsstatik, LTH,June 19S0.

[5] Mitler, H.E., The Physical Basisfor the Harvard Computer FireCode, Home Fire Project, Techni­caJ Report No. 34, actober 1975.

[6] Häggiund, B., Simulating theEarly Fire Orowth in ResidentialRooms, FOA, Stockholm 19S0.

[7] Rasbash, D.J. and Pratt, B.T.,Estimation of Smoke Produced inFires, Fire Safety Journal, Vol. 2,January 19S0.

[S] Quintiere, J.O., McCaffrey, B.and DenBraven, K., Experimentaland Theoretical Analysis ofQuasi-Steady Small ScaJe Enclo­sure Fires, NBSIR 7S-1511.

[9] Magnusson, S.E., Recent Deve­lopments in Mathematical Mode­ling of Fire Orowth, Notes for areport to the ClB/W14 meeting inAthens, May 1980.

[10] Quintiere, J., An Approach toModeling of Wall Fire Spread ina Room, Presentation given at theP .H. Thomas Honorary Confe­rence, Washington, Apri119S0.

[II] Babrauskas, V., Private comrnu­nication.

[12J Quintiere, J., A Simplified Theo­ry for Oeneralizing Results froma Radiant Panel Rate of FlarneSpread Apparatus. To be publish­ed.

[I3J Williarnson, R.B. and Fisher,F.L., Fire Orowth Experiments ­Toward a Standard Room FireTest WSS-79-48, Department ofCivil Engineering and LawrenceBerkeley Laboratory, Universityof California, Berkeley.

[I4J Paul, K.T., Fire Testing of Up­holstered Furniture and Bedding,Fire and Materials, Vol. 4, No. 2,19S0.

[15] Fitzgerald, W.E., Kinetics of Bur­ning in a Room Sized Calorime-

ter, Nat Symposium on Fire Safe­ty Aspects of Polymeric Mate­rials, American Chemical Socie­ty,1977.

[16J Thomas, P.H., Testing Productsand Materials for Their Contribu­tion to Flashover in Rooms. To bepUblished.

[17] Thomas, P.H., Fire Modellingand Fire Behaviour in Rooms.ISth Symposium (International)of Combustion, Toronto, August1980.

9

PETTERSSON, OVE FIRE HAZARDS AND THE COMPARTMENT FIRE GROWTH PROCESS-OUTLlNE OF A SWEDISH JOINT RESEARCH PROGRAM R80-5

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