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09 NBS TECHNICAL NOTE 879

U.S. DEPARTMENT OF COMMERCE/ National Bureau of Standards

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NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology,

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THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

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Environment* — Technical Evaluation and Application* — Fire Technology.

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* Part of the Center for Radiation Research.

* Located at Boulder, Colorado 80302.

* Part of the Center for BitOding Technology.
JUL 2 a 1975

\oo Fire Buildup in a Room and the Role of

r:s

Interior Finish Materials *

t° f lAVV na, $1 °\

Jin B. Fang

Center for Fire Research

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

Sponsored by:

Office of Policy Development and Research Department of Housing and Urban Development

Washington, D.C. 20410

and

National Bureau of Standards Washington, D.C. 20234

*<"*AU Of *

U.S. DEPARTMENT OF COMMERCE, Rogers C. B. Morton, Secretary

\j >S i NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued June 1975
Library of Congress Catalog Card Number: 74-600145

National Bureau of Standards Technical Note 879

Nat. Bur. Stand. (U.S.), Tech. Note. 879, 49 pages (June 1975) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1975

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 <Order hv SO Catalog No. C13.4n:ft7<ft. Price tl.10 <Add 25 percent additional for other than U.S. mailing).
CONTENTS

Page

1. INTRODUCTION 1

2. EXPERIMENTAL DETAILS 3 2.1. Test Compartment 3 2.2. Instrumentation 3 2.3. Test Specimens and Standardized Wood Cribs 5

3. TEST PROCEDURE

4. TEST RESULTS . COMPARISON WITH LABORATORY TEST METHODS 2 5 5.1. Ease of Ignition 29

5.2. Flame Spread 29

5.3. Heat Release Rate 34

5.4. Smoke Generation 36

SUMMARY AND CONCLUSIONS 3 8 ACKNOWLEDGMENTS 4

8. REFERENCES 40

APPENDIX A. A SENSITIVITY EVALUATION OF ROOM CORNER TEST PROCEDURE. . 42

APPENDIX B. SMOKE MEASUREMENTS IN OPEN AND CLOSED ENCLOSURES 4 3

ill

FIRE BUILDUP IN A ROOM AND THE ROLE

OF INTERIOR FINISH MATERIALS

J. B. Fang

A variety of wall and ceiling panels in a full-scale room

corner have been exposed to a fire from a standardized wood crib,

simulating the environment produced by the burning of a single

item of furniture, to evaluate their contribution to room fire

growth. A total of twenty room corner tests were performed using

selected combinations of eight wood-base and gypsum board-base

interior finish materials on the walls and ceiling. Gas temperatures and velocities, surface temperatures, heat fluxes, smoke

densities, and concentrations of oxygen, carbon dioxide and

carbon monoxide were measured. Ignition times of newsprint,

cotton fabric and plywood in the lower part of the room were also

recorded. The results of these full-scale tests were compared

with laboratory tests of the ease of ignition, surface flame

spread, heat release rate and smoke generation on the same materials. The maximum upper room gas temperature has been found to

agree with the ignition of such indicators as newsprint and

plywood, and to represent a measure of fire hazard in terms of

potential involvement of all combustible contents or room flashover. A temperature range of 450 to 650°C appears to be the

boundary between limited and full involvement.

Key words: Buildings; fire growth; flame spread; heat release;

interior linings; material ignitability ; performance criteria; room fires; smoke; wood crib.

1. INTRODUCTION

Recent fire loss statistics [l] 1 indicate that fires caused by smoking,

child-related activities and defects in electric wiring and appliances were

responsible for approximately one-third of all building fires and a higher

percentage of fire fatalities. These fires generally start small and, in a typical case, may be localized in a wastebasket, upholstered chair or bed.

Under certain circumstances, such a small, low intensity, or "incidental"

fire may grow into a fully developed room fire. The extent of this fire

growth depends on the quantity and type of combustible materials including

furnishings, movable contents and structural components located within the

room, upon which the fire can feed. Most building codes traditionally

regulate the potential fuel contribution of structural components, but not of

the movable combustible contents brought in by the building occupants.

Accordingly, building code officials are particularly concerned with the

increased risk of fire growth in residential occupancies due to combustible

interior finish materials, since rapid fire spread on interior surfaces is

listed among the major contributors to residential fire fatalities.

Interior finish materials represent a large portion of the area which

may be exposed to an accidental fire within buildings. These materials can

serve as barriers to fire with little or no contribution of heat and smoke,

or may burn as part of the chain of ignitions. It is of practical importance,

therefore, to assess the degree of hazard associated in the use of interior

finish materials in various locations in buildings and to improve the existing

lumbers in brackets refer to the literature references listed at the end of

this paper.
performance standards used as the measurement basis for keeping the hazard

within an acceptable level. Many performance standards currently being employ

are derived from subjective fire experience; thus, there is little substantiation that the fire ratings or indices obtained from standard laboratory tests can be correlated with the actual level of fire hazard. The objective of this

program is to assess the possible correlation between (a) standardized laboratory test evaluations, and (b) the observed fire growth patterns resulting

from exposure of wall lining materials to a typical low intensity fire source

in a residential room arrangement. While the conclusions reached in this

initial study are based on the actual and limited experimental conditions

employed, it is hoped that the techniques developed may ultimately serve to

assess the extent to which real fire hazards may be predicted by laboratory

tests.

A fire originating near the corner of a room formed by the intersection

of two adjacent walls, the floor and the ceiling subjects the wall linings

to increased radiative and convective heat flux levels due to multiple reflections and confinement of hot combustion gases. Thus, such a corner may consti

tute a critical configuration for evaluation of the fire performance of interi

linings. Furthermore, a corner/room test requires only a limited quantity of

test materials (e.g., two wall panels and one ceiling panel) and may be

instrumented to provide data on fire growth from initiation of the test up to

involvement of typical combustibles in fires or room flashover. In order to

compare the flame spread characteristics of various lining materials, corner

fire tests have been used to serve as an evaluation tool [2,3] and to demonstrate residential fire hazards [4]

Previous experimental studies have provided information on the fire

environment produced by various combustible contents of wastebaskets and

individual pieces of upholstered furniture [5,6], and on the development of

standardized wood cribs to simulate reproducibly similar levels of low intensi

fires in rooms [6,7]. A recent study on reduced scale modeling [8] represents

an encouraging approach to the determination of the fire hazards of compound

finish materials on walls and ceiling. In order to obtain a better understanding of the physical behavior and prediction of the fire intensity of such

small fires, a mathematical description of a freely burning fire [9] has also

been developed. This may be used to include the physical, thermal and fire

properties of interior lining materials into a prospective thermal analysis of

room fire growth.

The growth of a fire in a compartment with combustible linings and

sufficient ventilation can generally be described in terms of: ignition;

spread of fire across the walls and ceiling; rise of the compartment temperature; and "flashover" or full room involvement. The rate at which a fire

builds up depends on the balance between the rate of heat release by the

burning materials and the rate of heat loss by absorption in the walls and

ceiling, and by venting of the hot gases. A fire hazard rating based simply

on flame spread classification does not provide any direct information regarding the rate and amount of heat release by the material as displayed in the

room or the resultant heat balance. Whereas a finish material or assembly

with high thermal diffusivity may not necessarily contribute appreciably to a serious fire hazard, a material of the same flame spread classification having

relatively low diffusivity value might be a potential fire hazard because of

the resulting higher temperatures in the enclosing room or building. In a room fire, the rise in temperature of the enclosure walls and the hot gas

beneath the ceiling creates increased radiant and convective heat flux levels

which serve to produce new ignitions and enhance the rates of flame spread and

heat release. Evaluating the fire performance of a material in a room con- figuration is realistic since the material behavior in a fire depends considerably on the environment to which it is exposed. However, due to the expense

of large-scale testing and the large number of possible arrangements and sizes

of the room, it has not been considered practicable to employ full-scale corne room testing as a general evaluation tool in place of laboratory testing.
Therefore, this study was limited to: (a) an initial evaluation of fire growth

in a particular room arrangement and a few selected materials, and (b) comparisons with several laboratory test methods, including the ASTM E84 Tunnel Test

referred to in most building codes.

2. EXPERIMENTAL DETAILS

2.1. Test Compartment

Figure 1 is a plan view of the burn room showing the locations of wall

panels and a standardized wood crib in a room corner, and the arrangement of

instrumentation. All full-scale tests were conducted in a burn room having

a 2.9 x 3.2 m (9.5 x 10.5 ft) floor with a ceiling height of 2.4 m (7.9 ft).

An open doorway measuring 0.9 m (35 in) wide by 2 m (80 in) high near the

corner in the south wall (one of the smaller compartment walls) represented

a typical situation involving a single source of ventilation for the room. The basic construction of the test compartment was reinforced concrete

with the wall and ceiling lined with 16 mm (5/8 in) thick, type "X" gypsum

wallboards mounted to 51 x 102 mm (2 x 4 in) steel studs and finished with

a vermiculate gypsum plaster. Sand was placed over the brick subfloor. The

entire test compartment was situated within a large building to minimize

exterior weather effects.

2.2. Instrumentation

Temperature measurements were made with 36 thermocouples placed at the

selected locations inside the test compartment, as shown in figure 1, three

positioned along the flame axis above the wood crib, and 49 thermocouples

attached on both exposed and unexposed surfaces of the test panels. All bare

beaded thermocouples were of No. 24 B. and S. gage (0.51 mm wire diameter)

chromel and alumel wires. A total of eight Gardon type radiometers mounted on

the walls, ceiling and floor were used for measuring the heat flux levels

including the thermal radiation from hot ceiling and upper walls, and the

layer of hot gases and flames. The vertical distribution of the horizontal

component of gas velocity at the doorway was measured by four pitot tubes in

conjunction with variable reluctance pressure transducers.

In order to determine its weight loss rate during burning, the standardized wood crib was located on a weighing platform supported on a 227 kg (500

lbs) capacity strain gage load cell.

The levels of smoke density at various locations were monitored by

measuring the attenuation of a collimated visible light beam impinging on a photocell. Both the light sources and the photomultiplier tubes were protected from smoke deposition by air purging. Smoke measurements were made at

three locations shown in figure 1 — one horizontal measurement at 1.5 m (5

ft) height within the compartment, and two vertical measurements, one near the

left-center of the room, and the other at the doorway. These arrangements

permitted the measurement of relative values for the smoke accumulated within

the compartment or convected through the door opening.

Continuous measurements of carbon monoxide, carbon dioxide and oxygen

concentrations at a height of 76 mm (3 in) below the ceiling within the room

and at the upper edge of the doorway were made by extracting gas samples and

determining concentrations with infrared gas analyzers.

Three indicator specimens of ordinary newsprint, 0.19 mm thick white

cotton fabric and 6.4 mm thick fir plywood commonly found in dwellings were

placed within the test compartment to provide a direct indication of the
VERTICAL SMOKE METER O RADIOMETER • PITOT TUBES HORIZONTAL SMOKE METER

A GAS SAMPLING LOCATION <& INDICATOR SPECIMEN S

X THERMOCOUPLE PLACED AT 122 cm BELOW THE CEILING

® 2 THERMOCOUPLES, RESPECTIVELY AT 2.5 AND 122 CM BELOW THE CEILING

® 5 THERMOCOUPLES, AT 2.5, 25, 81, 122 AND 183 CM BELOW THE CEILING

® 9 THERMOCOUPLES AT THE DOORWAY

Figure 1. Plan View of the Burn Room Showing Locations of

Test Panels and Wood Crib, and Arrangement of

Instrumentation.
involvement of typical combustibles in fires. These indicators, each consisting of two 102 x 152 mm sheets and formed in a "L" shape with one sheet held

parallel to the floor, were placed at two locations as shown in figure 1: near one room corner and at the center of the floor, respectively at heights

of 500 and 100 mm above the floor.

In each test, a total of 110 channels of the output signals from thermocouples, heat flux meters, load cell, pitot tubes, smoke meters and gas analyzers were directly recorded every 10 seconds on a magnetic tape by a high

speed digital data acquisition system. The data were processed, tabulated and

plotted by the digital computer.

2.3. Test Specimens and Standardized Wood Cribs

Eight interior finish materials typical of those used in residential

dwellings and 127 mm (1/2 inch) thick bare asbestos-cement board were selected

for this test program. They represent a wide range of flame spread and smoke

levels. A summary of surface treatments, nominal thickness and bulk density

of these interior finish materials are presented in table 1 along with their

identification symbols.

Two types of standardized wood cribs, developed to simulate the fire

environments due to incidental fires, were employed to serve as ignition

sources. A large sized crib, measuring 560 x 560 x 550 mm (22 x 22 x 21 3/4

in) high and weighing approximately 33 kg (72 lbs) consisted of 34 pieces of

nominal 51 x 102 x 560 mm (2 x 4 x 22 in) long hemlock sticks nailed into a lattice to represent a- moderate intensity furniture fire. A smaller 360 x 360

x 300 mm (14 x 14 x 12 in) high crib weighing about 6.3 kg (14 lbs) and con- structed by piling 28 pieces of nominal 51 x 51 x 360 mm (2 x 2 x 14 in) long

sticks was used to simulate an incidental fire of shorter flame length and

duration. The large crib had eight layers, each containing four sticks with a 63.5 mm (2.5 in) stick spacing, plus a bottom layer containing two sticks.

The small sized crib consisted of six four-stick and two two-stick layers and

the spacing between sticks, except for the bottom two layers, was 51 mm (2 in).

The moisture content of the wood cribs was approximately 9 percent, as measured with an electrical resistance moisture meter.

3. TEST PROCEDURE

Three 1. 2x2. 4m (4x8 ft) full sized test panels were used to cover a room corner opposite of the doorway. Two wall panels were mounted at a spacing

of 89 mm (3.5 in) from the two adjacent walls on steel studs extending from

floor to ceiling. One ceiling panel, with its 2.4 m length running towards

the doorway, was nailed directly to wood furring strips whose thickness provided an, air space of approximately 19 mm (3/4 in) between the panel and the

ceiling, (see fig. 1) . A standardized wood crib was situated on the weighing

platform placed close to the corner at 254 mm (10 in) above the floor and 51 mm (2 in) away from the test wall panels. Photograph 1 shows the position of

the wood crib in a room corner prior to ignition, and a portion of instrumentation arrangement as viewed from the open doorway.

The test was started by application of an open flame to ignite 80 ml of

ethanol in a 203 x 203 x 25 mm (8x8x1 in) deep steel pan placed beneath

the crib. Visual observations and a photographic record of the fire buildup

process were made during the course of several of the tests. Data were collected until spontaneous ignition of specimen indicators occurred, which

usually required a minimum of 8 minutes, although the tests were extended

beyond this time for materials which did not cause full flame involvement.
Photo 1. Test Arrangement Before

Ignition Viewed Through the Open Door.
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4. TEST RESULTS

The photographic records of the development of an experimental fire with

Lauan plywood walls and acoustic tile ceiling in the full sized test compartment are shown in photos 2 to 4 . Photos 4 to 6 illustrate active burning

stage of the tests involving different types of wall lining materials exposed

to a common ignition condition. These observations reveal that -the rate and

extent of fire development depend considerably on the nature of lining materials involved.

In order to determine the experimental variables to which results in the

full-scale room corner tests were sensitive and the variability of present

test procedure, three test conditions including the size of wood crib, type of

wall lining material and choice of ceiling finish material were selected to be

explored for their possible effects on the maximum upper room gas temperature

and the peak one minute average smoke density within the fire compartment.

For this test series, two materials used to cover the walls and ceiling of a room corner were painted gypsum wallboard and particle board. They were each

exposed to the two ignition sources: the large and small standardized wood

cribs. Repeat tests were performed on eight randomly selected combinations of

experimental conditions as tabulated in table 2. This table also gives the

maximum values of the upper room gas temperature and the smoke density of the

duplicate test runs for each of the eight combinations.

By applying a statistical technique on factorial designs [10] , the estimated standard deviations of replication error were found be 27 °C for the

upper room gas temperature and 0.08 optical density/m (OD/m) for smoke density

measurements. The optical density/m is a measure of the density of lightobscuring smoke suspended in a volume, and is defined as the optical density,

or the common logarithm of the ratio of the intensity of the incident light to

that of the transmitted light, measured over 1 m of light path length. The

changes in crib size and type of materials on walls and ceiling all produced

significant variation in the upper room gas temperature at the 95% confidence

level. It was found that the conditions exerting important influences on smoke density measurement included the size of wood crib and type of wall

lining material. The change made in the type of ceiling finish material had

an insignificant effect on the results at this level. A detailed calculation

based on summary data presented in table 2 is given in Appendix A.

The experimental results of full-scale corner fire tests on time to

ignition, surface flame spread, time to flame penetration, maximum smoke

density, maximum upper room gas temperature, and time to flames emerging from

the doorway for selected combinations of eight finish materials used as wall

and ceiling linings are summarized in table 3. The data show that the elapsed

time for ignition of wall panels ranged from about 2 minutes for acoustic tile

(test 16) to approximately 3.5 minutes for vinyl covered gypsum board (tests

8, 13). The rate of weight loss of the small wood crib at ignition of the

wall materials varied from 0.38 to 0.51 kg/min with an average of 0.44 kg/min.

The maximum weight loss rate was found to range from 0.43 kg/min for painted

gypsum board to 0.79 kg/min for melamine finished hardboard walls, depending

on the feedback energy of the burning walls and ceiling involved. The weight

loss rate of the large crib was estimated to be of the order of 1.1 kg/min.

Excluding the tests the painted gypsum wallboard and vinyl covered gypsum

board which burned only to a vertical distance of about 0.5 m, the time taken

after ignition for flames to travel up the 1.8 m high wall to reach the ceiling

varied from 19 seconds (0.32 min) for Lauan plywood to 52 seconds (0.87 min)

for acoustic tile. The data also suggest that for the same type of material

(except particle board) , the rate of horizontal flame spread across the ceiling

was generally higher than that vertically along the wall surface, and was strongly dependent upon the type of wall lining material. The spread of

flames across the ceiling was enhanced by radiant and convective heating due

to the burning of the upper walls. Except for particle board, painted gypsum
Photo 2. Spread of Fire Along Wall

Panels, 4 Min After

Ignition.

Photo 3. Involvement of Ceiling Lining,

6 Min After Ignition.
Photo 4. Active Burning Stage,

8 ir.in after Ignition,

for Test Fire Involving Lauan Plywood Walls

and Acoustic Tile

Ceiling.

Photo 5. Fire Development, 9 min

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Fire Involving Painted

Gypsum Board Walls and

Acoustic Tile Ceiling.

Photo 6. Fire Development, 8 min

after Ignition, for Test

Fire Involving Melamine/

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12
wallboard and vinyl covered gypsum board, the time to "flame-through", i.e. to

burn completely through the panel, varied from 5 to 11 minutes and was dependent

upon the chemical composition and thickness of the material involved.

The maximum concentrations of smoke based on a one minute average generated within the ventilated compartment by painted gypsum board (tests 4,5,9),

vinyl covered gypsum board (tests 8,13) and asbestos cement (test 20) walls

under crib flame exposure condition were of the order of 0.2, 0.3 and 0.1 OD/m

respectively. The data also show that the walls covered with melamine finished

hardboard (tests 7,12,15) and those with particle board (tests 1,6) produced

the highest levels of smoke density and those with coated acoustic tile (tests

18,19) the least. For all tests, the times taken to reach peak smoke levels were found to range from 1.5 to 7 minutes after the onset of ignition on the

test panel.

The temperature of the gases within the upper half of the test compartment

was calculated by averaging of the temperatures of room gas at 10 locations; 5 at mid-height and the other 5 at 25 mm below the ceiling. This upper room gas

temperature is believed to directly relate to the possibility of full involvement of the combustible room contents. As shown in table 3, the peak temperatures of the upper room gas varied from approximately 130 °C for painted gypsum

board panels (test 5) to 800°C for melamine finished hardboard walls and

ceiling (test 15), depending on the type, thickness and arrangement of the

panels.

Flames emerging from a doorway or from a window opening can initiate the

spread of fire along a corridor and adjacent rooms or to the upper stories of

the building. In these tests, the time elapsed between ignition of the starter

fuel beneath the crib and flame emerging from doorway was obtained from visual

observations and was found to vary from about 4.5 minutes to infinity (i.e. no emergent flames) depending on the nature of the linings involved.

The times taken for spontaneous ignition of the indicators were observed

visually and found to depend upon the nature and location of the specimen

involved. In general, the newsprint was the easiest and the plywood the hardest

to ignite. Also, the indicator specimens near the room corner ignited earlier

than those at the center of the floor. The incident heat flux measured at the

center of the floor corresponding to the ignition of newsprint and plywood was

found to range from 1.7 to 2.5 W/cm^ and 2.1 to 3.3 W/cm , respectively.

Figure 2 shows a plot of upper room gas temperature at which newsprint or fir plywood indicators placed at the room center was ignited versus the elapsed

time between initiation of the test and ignition of the indicator involved.

The fire conditions required to cause ignition of these typical combustibles

was considered critical as they could ultimately lead to full room fire involvement and spread of fire to other rooms, and thus affect the survival of the

occupants and property. As shown in figure 2, the upper room gas temperature

at which the indicator was ignited varied from test to test, and ranged from

458 to 638°C for ignition of newsprint and 531 to 681°C for ignition of plywood.

Visual observation and experimental data indicate that the induction times for

ignition of these indicator specimens were considerably shorter than the

elapsed time between involvment of wall linings and onset of ignition on the

indicators. Also, the level of heat flux imposing on the indicators from the

developing fire was time variant depending upon the fire buildup process or

the type of finish materials used. For the purpose of estimating the condition

leading to involvement of all combustible contents or room flashover, the

average upper room gas temperatures necessary for spontaneous ignition of

newsprint and plywood panel placed at the center of the floor were 540 + 40°C

and 590 + 40°C, respectively, based on 95% confidence level. As shown in the

figure, the time taken to ignite newsprint and plywood varied from 5 minutes

for melamine finished hardboard walls and ceiling to approximately 9 minutes

for acoustic tile linings. The experimental data presented in figure 2 are tabulated in table 4

.

13
600 -.

400

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1 i i

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1

IGNITION OF

n

PLYWOOD -p»

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NEWSPRINT ^^ a*V

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MATERIALS INDICATORS

WALLS CEILING PLYWOOD 1 NEWSPRINT

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P G o

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IGNITION TIME (Min.j

8 10

Figure 2. A plot of the average upper room gas temperature

at which specimen indicator was ignited versus ignition

time. Identification symbols for these lining materials

are given in table 1. Dashed lines represent one standard

deviation limits for newsprint.

14
Table 4. Ignition Times of Newsprint and Plywood and the Upper

Room Gas Temperatures at which the Indicators

were Ignited Spontaneously.

Materials Newsprint Plywood

Walls Ceiling

Ignition

Time

(min)

Upper Room

Gas

Temperature

(°C)

Ignition

Time

(min)

Upper Room

Gas

Temperature

(°C)

Particle

Board

Particle

Board 5.7 605 7.0 681

Fir

Plywood

Painted Gypsum

Board — — 8.4 521

Particle

Board

Painted Gypsum

Board — — 6.9 545

Melamine /

Hardboard

Painted Gypsum

Board 5.5 563 7.0 592

Fir

Plywood

Acoustic

Tile 5.6 535 5.7 572

Melamine /

Hardboard

Acoustic

Tile 5.4 473 6.7 600

Particle

Board

Acoustic

Tile 6.9 518 8.4 603

Melamine /

Hardboard

Melamine /

Hardboard 5.2 570 5.8 670

Acoustic

Tile

Acoustic

Tile 8.9 519 9.2 533

Particle

Board

Painted Gypsum

Board 5.4 458 7.6 531

Particle

Board

Particle

Board 5.8 638 6.8 668

15
Some typical vertical gas temperature profiles at three locations inside

the fire room for a test where spontaneous ignition of the plywood indicator

occured at 9 minutes, and one test where no ignition took place is given in

figure 3. These profiles illustrate the convective flow pattern inside the

test compartment, and also show the presence of vertical stratification and

non-uniform distribution of temperature attributed to the induced cooling draft

along the floor and heat released by burning the lining materials. It can be seen that the temperature of the gases immediately above the plywood indicator

located at the center of the room was usually less than 370°C, which was the

measured ignition temperature for plywood [7]. It appears that the lower part

of the walls and floor were actually heated by radiation from the upper walls,

ceiling and combustion gases, while being cooled by forced convection of the

inflowing cool air. Upper room gas and ceiling radiation thus play a major

role in heating the lower part of the room in a fire.

Figure 4 shows plots of the composite horizontal velocity and temperature

profiles of the combustion gas at the open doorway for a test with fir plywood

walls and acoustic tile ceiling. These are taken at the time when the flame

first emerges from the doorway (29 5 sec) and when the upper room gas temperature is maximum (420 sec). These experimentally determined gas temperatures

shown in the figure were not corrected for radiation effect. The temperature

profiles exhibit the vertical stratification as a result of the smoke and

combustion products venting from the fire room along the ceiling and cool air

coming in through the lower portion of the doorway.

The variation with time of the average upper room gas temperature for

fires involving several different types of lining materials is shown in figure

5. The curves have been smoothed to simplify the presentation of data; they

retain the major features and relative effects. The upper room gas temperature

data of a blank test in which 6 . 4 mm (1/4 in) thick asbestos-cement boards

were used as wall and ceiling finish materials are also plotted in the same figure for comparison. It can be seen that the maximum gas temperature increas

from 130°C for painted gypsum board walls and ceiling, to approximately 420°C

for Lauan plywood walls and gypsum board ceiling, 660 °C for melamine finished

hardboard walls and gypsum board ceiling, and 510 °C for Lauan plywood walls

and acoustic tile ceiling. During the test with melamine/hardboard walls and

gypsum board ceiling, all indicator specimens including newsprint, cotton and

plywood were found respectively to ignite at times ranging from 6 to 7 minutes.

As indicated in the figure, the gas temperature within this time interval rose rapidly and exceeded 550 °C which is an upper room gas temperature at which

newsprint ignites readily. The temperature of the upper room gas resulting

from the burning of the standardized wood crib in the room lined with asbestoscement board increased at a relatively constant rate of approximately 1°C per

minute after 3 minutes due to a decrease in heat dissipated into the enclosure

walls as shown in the data of the blank test.

Figure 6 shows comparison plots of the time sequence of convective and

radiative heat-transfer-rates from the test room through the doorway to the

outside, for fires with different combinations of interior finish' materials.

The energy transfer calculations were made with the assumptions that both the

velocity and temperature distributions can be approximated by a finite number

of linear segments, the doorway opening can be considered as a blackbody

emitter with a uniform temperature, and the flue gas behaves as an ideal gas

for temperature correction on velocity measurements by pitot tubes, and has

the same thermal properties as air. From the figure, it appears that the

radiative contribution comprised approximately 10 percent of the total available energy to the outside due to the relatively low gas temperature and the

small size of the doorway opening. The bulk of the convective energy was discharged to the outside by way of a hot turbulent jet or stream issuing from

the upper portion of the doorway and its magnitude strongly depended upon the

material type and arrangement of the interior linings involved.

16
LOCATION

CENTER OF ROOM

2.0

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NEAR DOORWAY

ALL WITH ACOUSTIC TILE

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ACOUSTIC TILE

CEILING

AT IGNITION OF PLYWOOD

1

200 400

TEMPERATURE (°C)

600

Figure 3. Vertical gas temperature profiles

at various locations within the fire room.

17
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TIME(MIN)

Figure 5. Effect of material combination of wall and ceiling

linings on spatial average upper room gas temperature.

Legends on curves indicate wall/ceiling materials.

19
150

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5£

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MATERIALS

Wall/Ceiling

A - P/G

B - F/A

C - V/G

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400 600

TIME (SEC)

Figure 6. Convective and radiative heat - transfer - rate

through the doorway to an adjacent compartment for different

combinations of wall and ceiling linings. The subscripts

C and R indicate convective and radiative component, respectively.

20
In figure 7, the maximum rates of convective and radiative energy pouring

out from the fire room were plotted against the peak upper room gas temperatures for all tests performed. As indicated in the figure, the magnitude of

sensible heat due to outward convective flow is more or less directly proportional to the upper room gas temperature level. This convective energy carried

by the vent gas constituted a large portion of total energy leaving. Thus,

the interior finish materials may be ranked for increasing fire hazard according

to increasing maximum upper room gas temperature and a physically meaningful

method for evaluating the hazard potential of lining materials can be attained.

As mentioned previously, one aspect of fire behavior which has a direct

bearing on life safety is the level of temperature and heat flux developed

from the burning of building materials and structures. As the material type

and arrangement of interior finish materials had pronounced effects on the

upper room gas temperature, the experimental temperature data presented in

table 3 were used to examine the interrelation of these three variables. A

relation has been derived using linear regression analysis to express the

individual temperature rise contributions of the wall and ceiling materials to

the combined maximum upper room gas temperature:

T = 0.94 9 + 0.38 + 122 (1) u w c where T is the combined maximum upper room gas temperature, in °C. 9 and

9 are the characteristic temperature rises assignable to the wall and ceiling

materials respectively, in °C. The value of 9 for each material is determined

by measuring the maximum upper room gas temperature when the material lines the

walls and painted gypsum board covers the ceiling, and then substracting 107°C

which is the maximum upper room gas temperature when both the walls and ceiling

are lined with asbestos-cement board. When the flames fail to reach the

ceiling, 9 should be taken to be zero. It is important to note that these

characteristic temperature rises depend significantly on the room corner test

parameters such as crib size, room size, ventilation conditions, and insulation

properties of the remainder of the room. The empirical correlation expressed

by equation 1 provides a close approximation to the data points, with a correlation coefficient of 0.99, computed by the Pearsonian formula [11]. In this

and succeeding cases, a linear correlation over a limited temperature range

has been assumed in order to simplify the initial approach.

In considering the hazard of heat from building fires, the time to reach

full involvement of the room's combustible contents or room flashover is

important. This may determine the time available for safe evacuation of building

occupants and, further, rescue and firefighting operations begun prior to

flashover are far more effective than those begun later. Room flashover has

been simulated in our tests, by spontaneous ignition of the indicator specimens.

The elapsed times for spontaneous ignition of newsprint and plywood indicators

placed at the center of the floor have been correlated as a linear function of

the characteristic temperature rises of the wall and ceiling materials. The

results are:

t. = 11.3 - 0.011 9 - 0.00002 9 (2) l ,n w c

t. = 12.0 - 0.0094 9 - 0.0019 9 (3) i,p w c where t. and t. are the ignition times in minutes of newsprint and plywood

indicators respectively placed at the center of the floor. These two empirical

equations are least square data fits applicable for t. £ 9 minutes, and have cor- relation coefficients of 0.85 and 0.76, respectively.

Figure 8 illustrates the variation with time of the smoke density measured

at three locations. Similarly, figure 9 shows the concentrations of carbon

monoxide, carbon dioxide and oxygen within the fire room. The upper room gas

21
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24
temperature has also been plotted for comparison. Due to the circulation

pattern with cool air entering the fire room at low level and hot flue gases

vented out at the upper part of the doorway, the smoke density was stratified

with a maximum level near the ceiling and minimum near the floor especially in

the early part of a test. This is indicated in figure 8, where the smoke

density measured horizontally at the 1.5 m level was greater than that determined vertically. This difference is reduced after approximately 5 minutes.

The figure also suggests that smoke density closely paralleled the average

temperature of the gases within the upper half of the fire compartment. The

concentrations of carbon monoxide and carbon dioxide increased, and the oxygen

level decreased as the fire developed since the consumption rates of oxygen

for chemical reaction exceeded the inflow of oxygen into the compartment, (see

figure 9). It was found that at the peak of the fire, the oxygen concentration

and smoke density decreased sharply, and carbon monoxide and carbon dioxide

showed marked increases.

The smoke concentration near the fire and throughout a building is a major concern for safe evacuation during a fire. Although the weight concen- tration of smoke was not measured, the total amount of smoke produced can be

expressed in terms of a smoke quantity, which is defined here as the smoke

density multiplied by the volume in which the smoke particles disperse. The

total smoke quantity is equal to the sum of the quantity of smoke remaining

within the enclosure and that leaving the fire compartment. The measured

outflow smoke quantity adopted is the time integrated value of the product of

the smoke density and volumetric flow rate of the effluent gas at the open

doorway. The outflow smoke represents the major smoke component for this

experimental arrangement. The total rate of smoke production during fullscale tests with painted gypsum board ceiling and various types of finish

materials as wall linings are plotted as a function of time in figure 10. As

shown in the plots, particle board and melamine finished hardboard generally

had higher rates of smoke production, and vinyl-covered gypsum board, which

only burned partially, the least. The early increase in smoke production

during tests with particle board and Lauan plywood may be attributed to their

shorter times required for ignition. Also, the reduction in total amount of

smoke produced in the latter stage of the test reflects the lower smoke

density when the room temperature approaches a maximum.

Figure 11 presents cumulative smoke components within and outside the

fire compartment for the tests involving various combinations of wall and

ceiling lining materials. Inspection of figure 11 shows that the burn room

smoke quantity levels peaked out between 4 and 7 minutes and dropped off

gradually due to decreasing smoke density as a result of smoke particulate

coagulation or decomposition with continuous increase in the room temperature.

The amount of smoke within the fire room comprised approximately 5 percent of

the total smoke produced during the 8 minute period. Figure 12 shows cumulative smoke produced as a function of time for tests with different wall linings

5. COMPARISON WITH LABORATORY TEST METHODS

There are a variety of small-scale and medium-scale laboratory devices

presently available for measuring ignitability , surface f lammability , heat re- lease rate and smoke developed characteristics of materials. In order to

determine if a useful correlation could be established between laboratory and

full-scale test procedures, the results obtained by these room corner tests on eight different types of interior finish materials were compared with those

obtained by several new and established test methods. A possible application

of this information would be to help quantify the hazard characteristics of a total system involving the interaction of materials.

25
200

150 -

oo

cj

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100

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ALL TESTS WITH PAINTED

GYPSUM BOARD

CEILING

WALL MATERIAL

MELAMINE/HARDBOARD

PARTICLE

BOARD

FIR PLYWOOD

/

«. N

VINYL /GYPSUM

BOARD

8 12 Figure 10. Rate of smo^pWuced as a function of

time during room corner tests with different types

of wall materials.

26
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TIME (MIN

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Figure 11. Cumulative smoke components within and

outside the fire room for different combinations

of wall and ceiling linings.

27
/

800

/

WALL

MATERIAL

/

PARTICLE

BOARD

i a

o

£ 600 L

a

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GYPSUM BOARD CEILING

400

200 -

MELAMINE/

HARDBOARD

LAUAN PLYWOOD

FIR PLYWOOD

VINYL /GYPSUM BOARD

12 TIME(MIN)

Figure 12. Cumulative smoke produced as a function of

time during room corner test for fires involving different types of wall linings.

28
5.1. Ease of Ignition

A laboratory test apparatus for ease of ignition by flame impingement,

recently developed at NBS [12], was used to determine the ignition time sus- tained burning for each of these finish materials. The results of small-scale

tests on ease of ignition along with surface f lammability , heat release rate

and smoke generation properties for each selected interior finish material are listed in table 1. A comparison plot of the laboratory test results versus

thf. ignition times obtained from full-scale room corner tests is presented in

figure 13. Excluding coated acoustic tile, and painted and vinyl covered

gypsum boards, which did not sustain ignition during the laboratory tests, the

correlation of ignition times between the laboratory method and the room corner test for the lining materials examined was generally fair. In the

laboratory test, the assumed criterion of sustained ignition was if the specimen continued to flame for at least 1 minute after removal of the exposure

flame. Table 5 summarizes the expressions for the regression line obtained

from the least squares method, residual standard deviation, and correlation

coefficient to describe the degree of linear relationship between the regression

line and the measured values of the variable involved.

5.2. Flame Spread

Both ASTM E84 and E162 standard test methods [13,14] are conventionally

used for rating and classifying materials according to their surface flanuria - bility. Although there is little corroboration on the relationship between

fire ratings or indices obtained from these tests and the actual level of fire

hazard, and although present technology is unable to assess the impact of the

environmental conditions which may also be important, it is commonly believed

that these standard tests can provide data indicating relative fire spread

hazard of the materials based on "simulated fire" conditions. For this research

program, the information which will assist in translating the hazard ratings

of these laboratory tests to performance criteria for safe use of the lining

materials is of prime interest and desirable. It has been stated here that

maximum upper room gas temperature is an important indicator of fire hazard--

hazard to flashover in the room of fire origin and hazard of fire extension or exposure beyond the room of origin. It would be useful to assess if there is

any correlation between the maximum upper room gas temperature and the numerical surface f lammability ratings of the two widely used standard test procedures,

E84 and E162. Since it is usually contended that the absolute numerical

rating obtained from these tests is less significant than the relative ranking

of the materials, it may be sufficient to find that the upper room gas temperature is a monotonic function of the respective ratings. A particular monotonic

functional relation, namely, a linear relationship between these variables has

been chosen to study possible correlations at the present time. The possible

correlations with other types of functions have not been explored, and attention has been focused on the special correlation with hazard quantified by the

upper room gas temperature.

Accordingly, the surface burning characteristics of these finish materials were measured using the tunnel furnace and the radiant panel in accordance with the ASTM E84 and E162 standard test procedures. The flame spread

ratings for the wall lining materials obtained as the results of these laboratory tests are plotted in figures 14 and 15 against the maximum average upper

room gas temperatures from room corner tests. For these 8 tests, painted

gypsum board was the common ceiling material. As shown in the figure, the

results of both laboratory tests are generally in fair agreement with those

from the full-scale test, although there are several reversals in ranking.

The regression line equations from correlation of these experimental data are:

T = 2.5 F + 122 (4) u w

T = 2.9 I + 178 (5)

29
150 _ CM COATED ACOUSTIC TILE

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MATERIAL o GYPSUM BD. A VINYL/ GYPSUM BD. a PARTICLE BD.

Ct FIR PLYWOOD V LAUAN PLYWOOD MELAMINE/HARDBOARD

ACOUSTIC TILE

o A

100

IGNITION TIME (SEC)

CORNER FIRE TEST

200

Figure 13. Comparison of ease of ignition measurements by laboratory and corner fire tests. An

arrow on the top of the symbol denotes no sustained

ignition for laboratory test. Dashed lines represent limits of one residual standard deviation.

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where T = the maximum upper room gas temperature, in °C.

F = the E84 flame spread classification for the wall material. w

c

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w

c As the temperature increases, a linear relation would no longer be expected

due in part to increased radiation heat losses from the fire room, and in part

to the non-linear effect of flame spread rate in the laboratory test.

Although there is considerable variability in the results based on these

tests, it may still be possible to use E84 or E162 ratings as a crude measure

of contribution to fire growth in a room. For the limited types of wall linings

tested and the particular set of test conditions (room size and geometry, ven- tilation, wood crib ignition, etc) , the critical E84 and E162 flame spread

classifications corresponding to an upper room gas temperature of 540 + 40°C

appears to be significantly below 200.

The combined contributions of wall and ceiling linings to the upper room

gas temperature may be formulated in terms of an equation of the form:

T = AF + BF + C u w c However, the derivation and justification for such a relation appears to require

more data than the limited number of experimental results reported here.

5.3. Heat Release Rate

The heat release rate calorimeter being developed at NBS [15] was used to

determine the heat release characteristics of these selected lining materials

under radiant exposure conditions simulating a fairly severe fire environment.

In this test, a 11.4 by 15 cm (4.5 by 6 in) specimen was mounted vertically

at the center of the calorimeter, and exposed its front face to a radiant flux

of 6 W/cm produced by gas-fired radiant panels. The heat release rate of the

specimen was measured from the decreased rate of flow of fuel to an auxiliary

burner so that the rise in temperature due to the burning of the specimen was compensated. The heat release rates and the total heat released, which was determined by integrating the heat release rate over the burning period, were

based on the average of three determinations. The results are given in table 1.

Figure 16 shows the comparison between the highest 1-minute average heat release

rates obtained from this laboratory test measurements and the peak upper room

gas temperatures derived from the room corner tests. Except for melaminefinished tempered hardboard, which liberated heat rapidly for approximately a 1-minute period during rapid burning of the entire melamine layer and then had

a considerably lower heat release rate throughout the remainder of the laboratory

test, the correlation between these two test parameters is reasonably good as indicated in the figure. This would be expected in a room fire, where a large

portion of the initial heat released is v

-.**?^. to raise the temperature of the

room gases and enclosure walls and ceiling. The test conditions in the calorimeter are somewhat similar to the fire environment developed in the full-scale

test. The regression line equation be d on figure 16 is:

T = 27.3 H + 31 (6) u w

2 where H = heat release rate of the wall covering material, in W/cm .

34
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35
5.4. Smoke Generation

Consider the smoke hazard to a person trapped in a dwelling where smoke

is being produced, and vented out from an adjacent room, and spreading along

the ceiling. In this situation it may be difficult for the dwelling occupant

to escape due to impairment of vision and/or eye irritation, and an understanding of the tolerable human smoke levels is essential. The criterion of a visible range of 13.7 m (45 ft) with a transmission of 20 percent between

light source and photocell, or an optical density/m of 0.051, was suggested in

the Los Angeles school burning experiments [16,117]. Wakamatsu [18], in

performing a computer study of smoke movement in buildings, chose a lower

limiting smoke level of 0.04 3 OD/m based on potential panic and unbearable eye

irritation from exposure in a smoke-filled enclosure. Gross et al [19]

defined a critical smoke density, which mainly relates the visibility of

objects to smoke obscuration and corresponds to a level of 0.26 OD/m, based on

16 percent light transmittance over a 3.05 m (10 ft) viewing distance in a room measuring 3.8 x 6 x 2.4 m (12.5 x 20 x 8 ft) high. Bono and Breed [20]

conducted an experimental study of the effect of smoke development from burning

materials in a tunnel furnace on visibility in a 9.6 x 3.7 x 3.1 m (31.3 x 12 x 10 ft) high room in which the smoke was collected. From their photographic

records, the visibility of the lighted exit signs in the smoke accumulation

room was vague at an optical density/m of 0.27.

In order to relate and interpret the results of smoke measurements from

room corner tests with those from standard test methods, a mathematical simulation of smoke movements in an enclosure with and without an opening has been

developed and is presented in Appendix B. Smoke density and time to reach a critical smoke level or obscuration

time are considered important parameters for safe evacuation. Using Gross'

assumption of 3m (10 ft) with a light transmission of 16 percent as a hazard

criterion, the limiting value of total smoke quantity for a small dwelling

with a floor area of 7.6

2m (25 ft) by 12.2 m (40 ft) and a 2.4 m (8 ft) high

ceiling would be 29 OD/m . The time to reach this smoke level for the selected

material combinations have been included in table 6 along with the cumulative

quantity of smoke produced in an 8 minute period. It can be seen that the

time taken to reach this smoke level ranged from 3 to 5 minutes, depending on

the material type involved. Combining the regression line equation on smoke

data as listed in table 5 where the total smoke quantity is evaluated at 8 minutes and equation B-10 in which a critical smoke density of 0.26 OD/m is

used to substitute for D/L, the critical levels of smoke ratings from the NBS

smoke density chamber test method can be expressed in terms of the dwelling

volume, Q* , as follows:

* flaming exposure condition: D , = 0.071 Q (7)

* non-flaming exposure condition: D = 0.14 Q

where D is the maximum specific optical density and the subscripts f and n refer to flaming and non-flaming exposures in the smoke chamber.

This visual threshold based on the potential light obscuration hazard of

smoke in the buildings represents an approach which may serve as a criterion

for selecting appropriate finish materials as interior linings. It should be

noted that the empirical coefficient relating the room volume to the smoke

ratings depends upon the time interval during which the smoke quantities of

selected finish materials were evaluated.

Laboratory tests were conducted to evaluate the smoke producing properties

of the interior finish materials using the smoke density chamber [21] . The

maximum specific optical density, D obtained from the smoke density chamber

test procedure (separate flaming ana non-flaming modes) , was plotted against

the total smoke quantity, derived from the room corner test measurements as

36
Table 6. Data on Cumulative Quantity of Total

Smoke Produced in Full-Scale Tests

Materials Cumulative Total

Smoke Quantity Time to

Cumulative

Smoke Quantity

= 29 OD-m 2 (min) Walls Ceiling

m . Smoke Time ! _ ...

/ . x Quantity (mln) (OD-m 2

)

Lauan Plywood Painted Gypsum

Board

8 203

!

: 3.53

Painted Gypsum

Board

Painted Gypsum 8 57

Board

4.23

Vinyl/Gypsum

Board

Painted Gypsum 8 8l

Board

!

4.93

Particle Board Painted Gypsum

Board

8 702

!

3.11

Melamine/

Hardboard

Painted Gypsum

Board

8 617 4.20

Coated Acoustic

Tile

I Painted Gypsum 8 96

Board

4.0

Fir Plywood Painted Gypsum 8 147

Board

4.3

Acoustic Tile Painted Gypsum 8 66

Board

5.45

Fir Plywood Acoustic Tile 7.3 457 4.1

37
shown in figure 17. For these materials, the rate of smoke generation was

higher under the non-flaming than under the flaming exposure in the smoke

density chamber. Equation B-12 derived in Appendix B suggests that a linear

relationship exists between total smoke quantity and the maximum specific

optical density if both open and closed enclosures have similar smoke source characteristics, i.e., smoke generation rate. The poor correlation between

the value of maximum, specific optical density in the smoke density chamber

method and full-scale test results may be attributed to several factors,

including differences in the levels of heat flux acting on the test material

and the temperature buildup within the fire compartment. These two variables

affect the rates of smoke production and particulate vaporization, coagulation

or deposition. It should be noted that the time intervals at which the optical

density reached maximum varied with the test materials in the smoke chamber

test. With the use of equation B-12 along with the regression line equations

listed in table 5, and an exposed surface area of 0.00422 m^ for Ac

, the

ratios of the total amount of smoke produced in the ventilated fire room to

that generated in the closed smoke chamber were found to be 440 for flaming

exposure and 220 for non-flaming exposure conditions, respectively.

6. SUMMARY AND CONCLUSIONS

The following conclusions are based on a limited series of full-scale

fire growth tests in a room and corresponding small-scale laboratory tests on

a series of wood and gypsum board-base wall and ceiling lining materials. The

objectives were (1) to evaluate the extent of fire growth attributable to the

interior finish materials when exposed to a typical low intensity fire source,

and (2) to assess possible correlations between fire behavior during the fire

buildup process and numerical values from standardized laboratory tests.

Additional data, involving tests on a greater variety of wall and ceiling

materials are needed.

While the conclusions reached are not applicable beyond the actual types

of materials and experimental conditions employed, it was the intent of this

work to outline techniques which might be useful in assessing to what extent

real fire hazards may be predicted by laboratory tests. The conclusions are necessarily limited to the particular test conditions selected for initial

study and the specific arrangements and values of the important variables

which include: room size and shape, single open doorway serving as source of

ventilation, exposure of wall and ceiling panels to a corner fire source, and

a wood crib simulating the fire intensity and flame height (not extending to

the ceiling) of a small chair or a large wastebasket.

1. A small fire which starts in a chair or wastebasket may result in

a room fire which is out of control in 6 to 9 minutes, or which is

limited in intensity and extent for 20 minutes, depending upon the

fire properties of the wall and ceiling lining materials.

2. Both temperature and heat flux measurements indicate that the downward radiation emitted by the hot gases and the heated ceiling and

walls in the upper half of the fire room play the dominant role in

causing ignition of the combustibles situated below.

3. A useful measure of the development of a compartment fire is the

average temperature of the gases within the upper half of the fire

room. This temperature provides a correlation with the ignition of

typical combustible contents such as newsprint and plywood, and

represents an index of fire hazard in terms of potential involvement

of all room combustibles (flashover) plus extension beyond the room

of fire origin. A temperature in the range of 450 to 650°C appears

to be the dividing region between limited and full involvement.

Under this test configuration, the upper room gas temperatures cor- responding to spontaneous ignition of newsprint and plywood placed

38
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39
at the center of the floor were found to be approximately 540 + 40

and 590 + 40°C, respectively, and the times at which recorded ignitions occurred ranged from 6 to 9 minutes.

4. The wall plays a slightly more important role than the ceiling in

fire growth in this test arrangement. A correlation analysis on

the maximum upper room gas temperature data from the tests with

selected combinations of interior linings indicates that the total

contribution to the upper room gas temperature level consists of

approximately 70 percent from the wall linings and 30 percent from

the ceiling lining.

5. The correlations between the maximum upper room gas temperature

and both the ASTM E84 flame spread classification and the E162

flame spread index, were generally fairly good, even though there

were several reversals in material rankings.

6. The heat release rate based on the highest one-minute average, for an exposure of 6 W/cm^ , provides reasonable correlation with the

upper room gas temperature. For comparing relative hazard characteristics of interior finish materials, particularly at different

radiation exposure levels, the heat release rate calorimeter method

appears to have good prospects as an evaluation tool.

7. With smoke measurement, there is no strong correlation between the

results of the room corner test where wall involvement and resultinc

exposure is variable, and controlled uniform laboratory test con- ditions. It is evident that the amount of smoke produced from the

burning of lining materials is highly sensitive to the levels of hee

flux imposed on the materials, and the gas temperature in the upper

part of the enclosure.

8. Since standard laboratory tests are not designed for evaluating fire

hazards of combinations of finish materials on walls and ceiling,

the room corner test can provide meaningful results and should be

further developed.

7 . ACKNOWLEDGMENTS

The author would like to thank Mr. C. F. Veirtz, Mr. T. F. Maher and

Mr. B. E. Ramey for their assistance in the experimental work, Mr. J. W. Raine

for his help in modifying the computer program to process the outputs of the

data acquisition system, and Dr. D. Hogben for his advice on the statistical

design and analysis. This work was sponsored in part by the United States

Department of Housing and Urban Development.

8 . REFERENCES

[1] Fires and Fire Losses Classified, 1972, Fire J., 6_7, 23-26 (1973).

[2] Surface Flammability as Determined by the FPL 8-Foot Tunnel Method,

U.S.D.A. Forest Products Laboratory Report 2257 (1962)

.

[3] Maroni, W. F., Fire J., 6_7, 24-29 (1973).

[4] Williamson, R. B., and Baron, F. M. , J. Fire and Flammability, 4_, 99-

105 (1973).

[5] Gross, D. and Fang, J. B. , The Definition of a Low Intensity Fire,

Joint RILEM-ASTM-CIB Symposium Proceedings, Performance Concept in

Buildings, Vol. 1, Nat. Bur. Stand. (U.S.), Special Publication 361 (1972

40
[6] Fang, J. B., Measurements of the Behavior of Incidental Fires in a Compartment, Nat. Bur. Stand., (U.S.), NBSIR 75-679 (March 1975).

[7] Fang, J. B. and Gross, D., Contribution of Interior Finish Materials

to Fire Growth in a Room, Fire Safety Research, Proceedings of a Symposium held at the National Bureau of Standards on August 22, 1973,

Nat. Bur. Stand. (U.S.), Special Publication 411 (Nov. 1974).

[8] Parker, W. J. and Lee, B. T. , Fire Buildup in Reduced Size Enclosures,

Fire Safety Research, Proceedings of a Symposium held at the National

Bureau of Standards on August 22, 1973, Nat. Bur. Stand. (U.S.),

Special Publication 411 (Nov. 1974)

.

[9] Fang, J. B., Analysis of the Behavior of a Freely Burning Fire in a Quiescent Atmosphere, Nat. Bur. Stand. (U.S.), NBSIR 73-115 (Feb. 1973)

[10] Youden, W. J., Experimental Design and ASTM Committees, Materials

Research and Standards, 1, 862-867 (1961).

[11] Mandel, B. J., Statistics for Management, Dangary Publishing Co.,

Baltimore, Maryland, p 359 (1966)

.

[12] Parker, W. J., The Development of a Test for Ease of Ignition by Flame

Impingement, based on studies conducted at NBS , to be published.

[13] Standard Method of Test for Surface Burning Characteristics of Building

Materials, ASTM E84-70, American Society for Testing and Materials,

Philadelphia, Pennsylvania (1970) .

[14] Surface Flammability of Materials Using a Radiant Heat Source, ASTM

E162-67, American Society for Testing and Materials, Philadelphia,

Pennsylvania (1968).

[15] Parker, W. J. and Long, M. E. , Development of a Heat Release Rate

Calorimeter at NBS, ASTM STP 502, 135-151, American Society for Testing

and Materials, Philadelphia, Pennsylvania (1972)

.

[16] Los Angeles Fire Department, Operation School Burning, National Fire

Protection Association (1959).

[17] Los Angeles Fire Department, Operation School Burning, No. 2, National

Fire Protection Association (1961)

.

[18] Wakamatsu, T. , Calculation of Smoke Movement in Buildings, BRI Research

Paper No. 34, Japan (Aug. 1968).

[19] Gross, D., Loftus, J. J. and Robertson, A. F., Method for Measuring

Smoke from Burning Materials, ASTM STP No. 422, 166-204 (1967).

[20] Bono, J. A. and Breed, B. K. , Smoke Ratings in Relation to Visual

Observations-A Study, Fire Technology, 2, 146-158 (1966) .

[21] Lee, T. G. , Interlaboratory Evaluation of the Smoke Density Chamber

Test Method, Nat. Bur. Stand. (U.S.), NBS Tech Note 708, Appendix II

(Dec. 1971).

[22] Foster, W. W. , Attenuation of Light by Wood Smoke, British Journal of

Applied Physics, 10, 416-420 (1959).

[23] Pilot, M. J. and Ensor, D. W. , Plume Opacity and Particulate Mass

Concentration, Atmospheric Environment, 4, 163-173 (1970).

41
APPENDIX A. A SENSITIVITY EVALUATION OF THE ROOM CORNER TEST PROCEDURE

An estimate of the standard deviation of the replication error for a single test based on the data in table 2 can be obtained by taking the single

root of the sum of the differences between the duplicate test results divided

by twice the number of combinations [10] . Thus,

for the maximum upper room gas temperature S= 27.1°C

for the maximum smoke density S = 0.0832 OD/m

These correspond to coefficients of variation for replication error of 6.0% and

11%, respectively.

The combined estimate of the standard deviation of a difference between

two averages of n measurements is sJ—. A comparison of the differences between

two averages for the capital letter conditions and the lower case letter conditions is given in table 7. The estimated standard deviations of the difference

between averages of two replicate tests for each of four combinations are:

for gas temperature

for smoke density

S d

= (27.1) V| =

S d

= (0.0832) VI

13.6°C

0.0416 OD/m

The multiple, t, of these standard deviations which will give a difference

not likely to be exceeded by chance depends on the level of probability or confidence desired, and the number of degrees of freedom available for estimating the standard deviations. At the 95 percent confidence level, with

eight degrees of freedom, the value for t is 2.31. The upper limits at the 95

percent confidence level was calculated as:

f

for gas temperature

for smoke density

A = t-Sd

= 31.4°C

A = t-S d

= 0.096 OD/m

Table 7. Comparison of the Maximum Values of the Upper Room Gas

Temperature and the Room Smoke Density with Change In Test Variables

Variable

Average for

Capital Letters

Average for

Lower-Case Letters

Difference Between

Average

Gas

Temperature

(°C)

Smoke ; Gas ; Smoke Gas j Smoke

Density Temperature; Density j Temperature' Density

(OD/m) (°C) (OD/m'. (°C) (OD/m)

Crib Size 388 0.56 523 135 0.32

Wall

Material 271 0.52 iiJO 0.92 369 0.40

Ceiling

Material 409 0.68 502 0.77 93 0.09

42
APPENDIX B. SMOKE MEASUREMENTS IN OPEN AND CLOSED ENCLOSURES

Based on experimental observations of the light obscuration of wood smoke,

Foster [22] reported that the optical density of a volume containing smoke is

directly proportional to the mass concentration of smoke particles. A general

theoretical analysis of the relationship between particulate properties and

plume opacity has been made recently by Pilat and Ensor [23]. The generalized

equation is given by

e

. Ko *ln

&)

(B-l)

3 where C is mass concentration of smoke particles, in g/m , K is specific particulate volume/extinction coefficient ratio, in cm^/m , p is density of smoke -\ s particles, in g/cm-5

, L is light path length, in m, I is intensity of incident

light, and I is intensity of transmitted light.

The parameter K is a function of the particle size distribution, the

particle refractive index, and the wavelength of light. By using the definition of optical density, D, this equation can be rewritten in the following

form,

D _ C

L

" 2.303 p K

s (B-2)

This equation states that for a given particle density, parameter K,

and extinction path length, optical density determination is directly related

to smoke mass concentration measurement.

In order to relate and interpret the results of smoke density measurements

between a ventilated and a closed enclosure, an analysis of smoke movement in

these systems is desirable. For derivation of the relevant equations describing

these systems, the following simplifying assumptions are made:

1. The enclosure can be divided into two separate regions (upper and

lower) . In each region, the fluids are perfectly mixed to insure

no variation in smoke concentration.

2. The velocity of air entrainment into the smoke layer is directly

proportional to local velocity.

3. The rate of loss in smoke caused by coagulation, settling, vaporizing, and condensing is proportional to local smoke concentration.

Consider a ventilated enclosure where the smoke being generated from a pyrolyzing source flows beneath the ceiling and vents through the upper part

Of an opening, and cool air is drawn into the system via the lower portion

of the same opening, and entrains upward into the smoke layer.

The equation of conservation of smoke mass for the upper region of the

enclosure is given by

dC , ( V + V , \ _ m"A EUC* ,„ ,. dT + ^"WSh— + k

)

C = WSh + —

h

(B_3)

where C is mass concentration of smoke in the upper region, t is time variable,

in sec V is volumetric flow rate of the exiting hot fluid, in m-vsec, V is

volumetric flow rate of hot fluid diffusing into the lower region, k is settling

coefficient, dimensionless, m" is smoke producing rate per unit surface area,

in g-OD/m^-sec, A is surface area of smoke producing source, in m , h is the

43
thickness of the upper layer, in m, E is entrainment coefficient, dimensionless,

U is bulk velocity, in m/sec, C* is mass concentration of smoke in the lower

region, in g/itH , w and S are width and length of the enclosure respectively,

in m.

In the lower region where the hot fluid stream circulating downward within the enclosure mixes immediately with the entering air, its smoke concentration can be obtained by macroscopic mass balance and with the assumptions of no settling out of smoke particles and negligible smoke accumulation

C* = V

1 C

V +

a

V-! (B-4)

where V is volumetric flow rate of entering air,

a

^

Eliminating C* in equation B-3 with use of the above relation and integrating over a specified time interval, x, gives

C = o" IS SXP [ * (t " T)] dt (B-5)

where <J> =

(V + V

WSh

EUV

FT(v + v1

) a + k

For a closed enclosure, the volumetric flow rate of hot fluid circulating

into the lower region can be taken as equal to that of the cold fluid entrainment into the upper region as a reasonable approximation. With an additional

assumption of no settling out of suspending smoke 'particles , the mass concentration of smoke in a closed system at any time interval, t, is expressed as

_ r i m"A ,. C = / fTTTT" dt

o WSh

and the optical density is obtained from equation B-2,

L

D = f

T S3 dt 2.303Kp 6 WSh

s

(B-6)

(B-7)

For an open enclosure, the flow rate of hot fluid dispersing into the lower

region can be neglected in comparison with those of the exiting and the inflow

streams. The mass concentration of smoke in an open system for the case of no particulate settling out can be approximated by

= /

o m"A

WSh exp [(f)

1 (t--r) ] dt

and the expression for optical density is

D = 2.303Kp 6 s

m"A

WSh exp [(J)' (t-t) ] dt

(B-8)

(B-9)

where = V/WSh.

44
Assuming the smoke layer to occupy the upper half of the room height, a simple expression relating the smoke density to the quantity of smoke produced

and the volume of the room (or dwelling) in which the smoke is accumulating,

can be obtained by differentiating equation B-9 with respect to time, or simplifying equation B-3 with use of the preceding assumptions and equation B-2

,

and integrating over a specified time interval, x. This results in the relation

D 2 f r rVD ,. , WShD'l 2 r i .„._ ,. ,_ iri , L

= Q*[^ "L dt + ~^r-\ = 2.303Kp

s Q* f

o m A dt (B " 10)

where D/L is the average smoke density, in OD/m.

'

Q* is the total volume of the room or dwelling, in m

3

D/L and D'/L are the average smoke density measured at time t,

at the doorway and inside the fire room respectively, in OD/m.

Division of equation B-10 with the relation expressed by equation B-7 and

rearrangement of the resultant equation yields the relationship between the

total amount of smoke produced and optical density measurements in open and

closed enclosures.

/

T m"A dt

o o

'

/

T m"A dt

c c

dt /L \/W S h \ o __ I __c W _o_o_o\

,. ~ \L Aw S h / dt \ o' x c c c' D^ + W s'h D- T

V

o

D

odt

L c o o o o (B-ll)

where D is optical density, and the subscripts c and o denote the closed and

open systems respectively.

By introduction of the specific optical density, D , defined as

D = Q D'/L A , into equation B-ll, an expression relating smoke measurements

between full-scale room corner test and the NBS smoke density chamber method

can be obtained as

fQ D' V D "I o o , ,t o o -,. /

T m"A dt L^~ +

I IT- dt

o J o

u o o J

/

T m"A dt AD o c c c s

where Q0000..,,,. = W S h , the room volume containing the smoke particles

, ' c in the fire room, and

= W S h , the chamber volume in which the smoke particles

c c c c ,

.

disperse.

(B-12)

45

MBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS Tech. Note 8 792. Gov't Accession

No.

3. Recipient's Accession Nc

4. TITLE AND SUBTITLE

FIRE BUILDUP IN A ROOM AND THE ROLE OF

INTERIOR FINISH MATERIALS

5. Publication Date June 1975

6. Performing Organization Code

7. AUTHOR(S)

Jin B. Fang

8. Performing Organ. Report No. NBS TN- 879

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 49 06197

11. Contract/Grant No.

2. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Same as No. 9

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

Library of Congress Catalog Card Number: 74-600145

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) A variety of wall and ceiling panels in a full-scale room corner have been exposed

to a fire from a standardized wood crib, simulating the environment produced by the

burning of a single item of furniture, to evaluate their contribution to room fire growth

A total of twenty room corner tests were performed using selected combinations of

eight wood-base and gypsum board-base interior finish materials on the walls and

ceiling. Gas temperatures and velocities , surface temperatures, heat fluxes, smoke

densities, and concentrations of oxygen, carbon dioxide and carbon monoxide were

measured. Ignition times of newsprint, cotton fabric and plywood in the lower part

of the room were also recorded. The results of these full-scale tests were compared

with laboratory tests of the ease of ignition, surface flame spread, heat release rate

and smoke generation on the same materials. The maximum upper room gas temperature has been found to agree with the ignition of such indicators as newsprint and

plywood, and to represent a measure of fire hazard in terms of potential involvement

of all combustible contents or room flashover. A temperature range of 450 to 650 °C

appears to be the boundary between limited and full involvement.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Buildings; fire growth; flame spread; heat release; interior linings; material

ignitability ; performance criteria; room fires; smoke; wood crib.

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