Fire Safety Journal, 5 {1983) 191 - 197 191

T h e D e v e l o p m e n t o f a F u l l - s c a l e R o o m F i r e Test

U. WICKSTR{~M, B. SUNDSTROM and G. HOLMSTEDT

Swedish National Testing Institute, Bor~s (Sweden)

SUMMARY

A large-scale room calorimeter has been developed for testing surface lining materials as well as furniture and other fittings. Heat release rates in the fire room have been mea- sured in various ways. The technique based on oxygen consumption was deemed to be the most suitable for a standard test. A hood has therefore been built to collect all the fire gases leaving the room; thus, the rates o f pro- duction o f smoke and various chemical com- pounds can readily be measured and give a good basis for estimating the fire hazard of a specimen. As it is extremely difficult to scale fire tests there is an urgent need for evaluating laboratory scale tests. This accurately defined, full-size method could serve as an invaluable tool for this purpose. Tests o f several wall lining materials and pieces o f furniture are reported in the paper.

INTRODUCTION

This paper presents the progress of an experimental s tudy to develop a full-scale room fire test. The project is named "Fire H a z a r d - Fire Growth in Compartments in the Early Stage of Development (Pre-flash- over)". It is being carried out jointly by the Lund Institute of Technology and the Swedish National Testing Institute. The ulti- mate goal of the project is to develop a full scale test method for surface lining materials as well as for furniture and other products, from which the behaviour of the tested mate- rial or product can be predicted at a real fire [1 ]. To achieve that goal, it is necessary to have reliable mathematical models so that results from tests can be used to predict the fire behaviour under a variety of other con- ditions.

Full-scale room fire experiments are often used for evaluation of the growth charac- teristics of materials and building systems. In spite of this, there is still no standard version of a room fire test, and there is therefore a great need to develop such a test method. The exact details of a standard room fire test are presently being debated by working groups within the American Society for Testing and Materials (ASTM) [2]. Within the ISO a working group under TC/92 SC 1 has recently been proposed [3] to develop a similar method.

The purpose of a full-scale standard test would be to evaluate the fire performance of materials or objects under actual in-use situa- tions. The contribution of a specimen to the fire growth within a previously calibrated compartment can then be used to rate mate- rials and also to evaluate the validity of existing small scale methods.

Current thinking favors a test compartment with a single door and the ignition source placed in one corner of the interior, away from the door [2]. Various ways of grading test specimens are plausible. The most straight- forward and simple way is just to measure time to flashover, when flames begin to issue from the opening. More information on the properties of a specimen are, however, achieved if the rate of burning can be contin- uously measured, and the room used as a full- scale calorimeter. In this project the energy balance of a fire room has been studied under controlled conditions using a gas burner and inert walls, and the energy flow from the opening has been measured.

Measurement of the rate of heat release, RHR, has been achieved in two ways: by analyzing the heat balance of the fire room and by measuring the oxygen consumption. The former method is uncertain, as the con- vection heat loss term through the doorway is dominant in the heat balance equation, and

0379-7112/83/$3.00 © Elsevier Sequoia/Printed in The Netherlands

192

t e m p e r a t u r e and gas ve loc i ty vary consider- ab ly over the d o o r w a y . Several measur ing po in t s are requ i red to achieve sa t i s fac to ry accu racy [4, 5]. Addi t iona l ly , the wall loss t e r m is d i f f icu l t to assess, pa r t i cu la r ly w h e n tes t ing c o m b u s t i b l e wall linings. The m e t h o d was t h e r e f o r e d e e m e d unsu i tab le for a stan- dard test .

More p romis ing is the m e t h o d based on o x y g e n c o n s u m p t i o n . The heats o f com bus - t ion per uni t o f o x y g e n c o n s u m e d are a p p r o x - ima te ly the same for m o s t fuels c o m m o n l y e n c o u n t e r e d in fires [6] . A m e a s u r e m e n t of the ra te of o x y g e n c o n s u m p t i o n can t h e r e f o r e be c o n v e r t e d to a measu re o f R H R .

THE ROOM AND INSTRUMENTATION

A tes t r o o m of l igh tweight conc re t e wi th d imens ions equal to t ha t discussed b y work i ng g roups wi th in ASTM has been bui l t

. . . . . . . . J 1

TO ~XHAUSI GAS @40~J ] ] (LEAN NO [

, . :

L ] i

i

J 6

ELEVATION

[ ..... l

/ HUE)I) }. i / / " ,

• t [DLIO#WA'~

FRONT VIEW

Fig. 1. Test room and ventilation system as shown in elevation and front view (lining materials and fur- nishing are usually not tested at the same time, as shown in the elevation).

bLAb3 PiLT~ S

f7.2

1 ! i . . . . . . . . . .

• " Z .72:_ 2 ; : ~ - ' ~

- - ~ = - - ":i 7: . . . . JL_n" r- ~ k _, ...... ~ _ ,

>APhMAONET ~H N~PARED SPEU[JPh(l~OMe ; ; , ~ ~ : " N [ .: '41

Fig. 2. Gas analysis system with sampling line from the exhaust duet.

(see Fig. 1 ). A hood , conneE~ted to the ordi- nary evacua t ion sys t em of the fire hall v i a an exhaus t duc t , is p laced outs ide the d o o r w a y to col lec t the fire gases leaving the r o o m . Figure 2 shows h o w gas is s ampled for cont in- uous regis t ra t ion o f the oxygen , ca rbon d ioxide , c a r b o n m o n o x i d e , h y d r o c a r b o n s and n i t rogen ox ides con ten t s . Gas samples for the d e t e r m i n a t i o n o f o t h e r species m a y also be taken. The sampl ing line is coo led so tha t the wa te r condenses be fo re enter ing the instru- ments .

The ra te of mass f low is measured by a p i to t t u b e and a t h e r m o c o u p l e in the cen te r o f the duet . To ob ta in a ful ly deve loped ve loc i ty prof i le a t a ra ther sho r t d is tance f rom the h o o d guide vanes are instal led b o t h be fo re and a f t e r the measur ing sec t ion , as shown in Fig. 3. Baffles are m o u n t e d inside the h o o d to ensure good gas mix ing be fo re en te r ing the duct .

The s m o k e dens i ty in the duc t is measu red by a l amp pho toce l l sys tem. In order to

194

Rate of heat release [kW]

$08

400

AL/'

2 8 8

F . . . . . .

I

I l I I

. . . . . . . + . . . . +

i i

8 I I~ 2 8 3 8 4 8 5 8 6 8 /0 8r~

'[ t l , ,~ ' ,

Fig. 4. R a t e o f h e a t release c a l c u l a t e d f r o m o x y g e n

c o n s u m p t i o n (full l ine) compa red wi th burner input (dashed line) as a func t ion of t ime.

RHR

300-

200 -

100

kW]

~UU N@PDTE£T

I

/

I f . l I loo

i,,I

S 'tO I c 20 Time [rmn]

Fig. 5. Heat release rates of ignit ion source v s . t ime as discussed wi th in NORDTEST and ASTM, respectively.

should r ep resen t a realist ic fire exposu re for the tes t spec imen and, at the same t ime, give a r e sponse for var ious mater ia ls sui table for ranking and classif icat ion. The igni t ion source cu r ren t ly used is a 17 cm >: t 7 cm, p r o p a n e fed, sand bed burner , which is loca ted in one co rne r of the tes t c o m p a r t m e n t .

Several i n t r o d u c t o r y tests have been con~ duc t ed to deve lop the test p rocedure . In Table 1 the t ime to f lashover is gwen for a n u m b e r of mater ia ls wi th var ious bu rne r hea t release ra tes ; some e x p e r i m e n t s were dupli- ca ted in o rde r to e s t ima te repea tab i l i ty . Flash- over is here def ined as the t ime when sus- ta ined f lames issue f r o m the d o o r w a y . Note tha t t ime to f lashover for c h l p b o a r d m o u n t e d on walls on ly is a b o u t the same as for chip- boa rd m o u n t e d on b o t h walls and ceiling while, on the o t h e r hand , a r e m a r k a b l e delay occurs if c h i p b o a r d is m o u n t e d on the ceiling only . When tes t ing the PVC wal lpaper , glued on g y p s u m plas te r board , at 100 kW the fire did no t spread. However , when a b o u t 30 min later a bu rne r p laced in the oppos i t e corner was run a t 300 kW f lames spread rap id ly over the ent i re ceiling and a severe fire deve loped tha t las ted for a b o u t five seconds.

On the basis o f the expe r i ence gained f rom these e x p e r i m e n t s it was dec ided to use an ignit ion source of 100 kW for the first 10 min. If f lashover has n o t occur red within t ha t per iod of t ime , the hea t release ra te is in- creased to 300 kW, as shown in Fig. 5. This igni t ion source is s t rong enough to give f lames

TABLE 1

Time to flashover, f /o , def ined as sus ta ined f laming issuing f rom the doorway for various ma~,. rials m o u n t e d on the walls or the ceiling

Material Ceiling Walls Burner R H R Time of ," % (kW) (min.s~

Chipboard yes yes 175* !. 50 Chipboard yes yes 50 ! .00 Chipboard yes yes 50 1 00 Chipboard yes yes 100 2: ~ 5 Ch ipboard yes yes 100 2.30 Chipboard yes no 100 7" 50 Chipboar d no yes 100 3 : 15 Porous board yes yes 100 l 00 PVC wall paper yes yes 100 -- PVC wall paper yes yes 300 -* *

*Burner size 30 cm x 30 cm. **F lames deve loped along the ent i re ceiling.

TABLE 2

Time to flashover, f/o, for materials tested in full scale with an ignition source of 100 kW increasing to 300 kW after 10 min

195

Materials Thickness Density Time to f/o (mm) (kg m -3) (min:s)

g/b 13 700 -- Paper w/p on g/b 0.6 + 13 200* -- Textile w/p on g/b 0.7 + 13 370* 10:40 PVC w/p on g/b 0.7 + 13 240* 10:15 c/b 10 750 2:30 Hardboard 12 600 2:14 Wood panel 11 530 2:18 Porous board 13 250 1:07 Paper w/p on c/b 0.6 + 10 200* 2:22 Veneer on c/b 2 + 10 810 7:45 Textile w/p on m/w 0.7 + 50 370*]70 0:55 Polystyrene foam 50 20 2:12 Polyurethane foam 30 30 0:14

g/b = gypsum board. c/b = chip board. m/w = mineral wool. w/p = wallpaper. *Surface density of wallpaper, g m -2.

reaching the ceiling; materials m o u n t e d on the ceiling only can therefore be tested.

A s t ronger ignit ion source would be t oo d o m i n a n t and drive m a n y materials o f interest to f lashover t oo quickly. The ignit ion source discussed within ASTM commi t t ee s starts to simulate a burning object in three steps and after 90 s reaches a hea t release rate o f 176 kW (10 000 Btu min TM ), as shown in Fig. 5. We have no t a d o p t e d such a stepwise start as we believe it unnecessar i ly compl ica tes the test p rocedure and makes possible theore t ica l analysis more difficult .

A comprehens ive test series has recent ly been carried ou t wi th the ignition source run at 1 0 0 / 3 0 0 kW, as described above. Thir teen materials o f various compos i t ions , including plastics, were tested, all m o u n t e d on the walls and the ceiling. The same materials were also tested accord ing to several l abora to ry scale methods , and the results are cur ren t ly being evaluated and will later be c o m p a r e d and cor- related with the full scale results. Repor t s are being prepared.

The t ime to f lashover for the tested mate- rials is given in Table 2. Note tha t f lashover occur red for two materials af ter more than 10 min when the ignit ion source was raised f rom 100 to 300 kW. As an example, Fig. 6 shows the measured heat release rate for a test o f a

Rate

1.0

0.6

0,7

0.6

0.5

0.4

0.3

0.1

0.0,

0,0

of heat release [MW]

A.

2 . 0 4 .0 6 . 0 8 . 0 18 2 12.0 14 ,0 10.0 18.0 2 0 . 0

TJ-me [ m z n ]

Fig. 6. Rate of heat release v s . time for paper wall- paper on gypsum board with an ignition source of 100 kW increasing to 300 kW after 10 minutes.

material o f good fire pe r fo rmance , paper wall- paper on gypsum board. In this case, f lashover does no t occur at all, a l though the heat re- lease rate reaches a peak when the burner o u t p u t is raised ins tan taneous ly af ter 10 min and the area near the ignit ion source flames burns off.

A m u c h faster fire g rowth leading to flash- over in less than one minute occurs with a texti le wallpaper glued on mineral wool , as