A UNITED STATES DEPARTMENT OF COMMERCE

PUBLICATION NBS TECHNICAL NOTE 794

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NBS Corridor Fire Tests:

Energy and Radiation Models

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COMMERCE

National

Bureau

of Standards
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,

the Institute for Computer Sciences and Technology, and the Office for Information Programs. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

States of a complete and consistent system of physical measurement; coordinates that system

with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Nuclear

Sciences 2 — Applied Radiation - — Quantum Electronics " — Electromagnetics 3 — Time

and Frequency 3 — Laboratory Astrophysics 3 — Cryogenics '. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized

materials needed by industry, commerce, educational institutions, and Government; provides

advisory and research services to other Government agencies; and develops, produces, and

distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor

Radiation — Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote

the use of available technology and to facilitate technological innovation in industry and

Government; cooperates with public and private organizations leading to the development of

technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute consists of a Center for Building Technology and the following divisions and offices: Engineering and Product Standards — Weights and Measures — Invention and Innovation — Product Evaluation Technology — Electronic Technology — Technical Analysis — Measurement Engineering — Structures, Materials, and Life Safety * — Building Environment * — Technical Evaluation and Application * — Fire Technology.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effec- tiveness in the conduct of their programs through the selection, acquisition, and effective

utilization of automatic data processing equipment; and serves as the principal focus within

the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center consists of the following offices and divisions: Information Processing Standards — Computer Information — Computer Services —

Systems Development — Information Processing Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and

accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and

a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum

accessibility to the scientific information of the world. The Office consists of the following

organizational units: Office of Standard Reference Data — Office of Technical Information and Publications —

Library — Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted: mailing address Washington, D.C. 20234.

a Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.

• Part of the Center for Building Technology.
Nation.APR 2 3 1974 NBS Corridor Fire Tests:

Energy and Radiation Models

Francis C. W. Fung

Structures, Materials, and Life Safety Division

and

Miles R. Suchomel and Philip L. Oglesby

Fire Technology Division

Institute for Applied Technology

National Bureau of Standards Washington, D.C. 20234

t. -^L

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secrefary NATIONA1. BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued October 1973
National Bureau of Standards Technical Note 794

Nat. Bur. Stand. (U.S.), Tech. Note 794,127 pages (Oct. 1973) CODEN: NBTNAE

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. 03.46:794) Price $1.40
TABLE OF CONTENTS

Page

LIST OF FIGURES iv

LIST OF TABLES vi

LIST OF SYMBOLS vii

1. INTRODUCTION 3

2

.

EXPERIMENTAL FACILITIES 4

3. GENERAL DESCRIPTION OF EXPERIMENTS 6

4. EXPERIMENTAL OBSERVATIONS 7

5. ENERGY BALANCE CALCULATIONS 11

5.1 Energy Balance Equations 11

5.2 Results of Energy Balance Calculations 17

6. FLOOR COVERING EVALUATION BY ENERGY

CONSIDERATIONS 23

7. FLAME SPREAD AND CEILING RADIATION 26

8. CONCLUSIONS 32

9

.

FUTURE WORK 34

APPENDIX A - TEST OBSERVATIONS 39

APPENDIX B - FLAME SPREAD CALCULATIONS 57

REFERENCES 61

in
LIST OF FIGURES

1. Corridor Facility

2. Corridor Wall Sensor Locations

3. Corridor Floor Sensor Locations

4. Total Crib Rate of Weight Loss

5. Temperatures Near Corridor Doorway, Test 339

6. Temperatures Near Corridor Doorway, Test 340

7. Temperatures Near Corridor Doorway, Test 341

8. Temperatures Near Corridor Doorway, Test 342

9. Temperatures Near Corridor Doorway, Test 343

10. Temperatures Near Corridor Doorway, Test 344

11. Flame Spread on Floor Covering

12. Burn Room Heat Balance, Test 339

13. Burn Room Heat Balance, Test 342

14. Burn Room Heat Balance, Test 343

15. Burn Room Heat Balance, Test 344

16. Burn Room Heat Balance, Test 345

17. Total Crib Heat Release and Loss to Burn Room Walls,

Test 339

18. Total Crib Heat Release Rate and Loss to Burn Room

Walls, Test 343

19. Total Crib Heat Release Rate and Loss to Burn Room

Walls, Test 344

20. Total Crib Heat Release Rate and Loss to Burn Room

Walls , Test 345

21. Rate of Convective and Radiant Energy Release from Burn

Room, Test 339

22. Rate of Convective and Radiant Energy Release from Burn

Room, Test 342

23. Rate of Convective and Radiant Energy Release from Burn

Room, Test 343

24. Rate of Convective and Radiant Energy Release from Burn

Room, Test 344

25. Rate of Convective and Radiant Energy Release from Burn

Room, Test 345

26. Corridor Energy Comparison, Test 342

27. Corridor Energy Comparison, Test 343

iv
28. Corridor Energy Comparison, Test 344

29. Corridor Energy Comparison, Test 345

30. Cumulative Corridor Energy Input

31. Cumulative Corridor Energy Input

32. Cumulative Corridor Energy Output

33. Typical Corridor Preheating Temperature Just Prior to

Flameover (10 Ft. Location)

34. Typical Corridor Preheating Temperature Just Prior to

Flameover (20 Ft. Location)

35. Cas Temperature and Velocity Profiles at Exit Windows,

Test 339

36. Gas Temperature and Velocity Profiles at Exit Window,

Test 333

37. Sequencial Corridor Gas Temperature Profiles

38. Carpet Surface and Gas Temperature One Inch Above

Carpet at 7.5 Ft. Station, Test 344

39. Carpet Surface and Gas Temperature One Inch Above

Carpet at 12.5 Min. , Test 344

40. Carpet Surface and Gas Temperature One Inch Above

Carpet at 6 Min. , Test 345

41. Corridor Ceiling Surface Temperature History at 10 Ft.

Station

42. Corridor Ceiling Surface Temperature History at 10 Ft.

Station

43. Ceiling Radiation Calculation Illustration

44. Comparison of Calculated and Measured Radiation Incident

on Floor, Test 343

45. Comparison of Calculated and Measured Radiation Incident

on Floor, Test 344

46. Comparison of Calculated and Measured Radiation Incident

on Floor, Test 345

47. Incident Radiation on Floor Just Prior to Flameover
LIST OF TABLES

1. Summary of Corridor Flame Observations

2. Material Description

3. Smoke in Corridor Tests

4. "Flame Over" Initiation Time

5. Carpet Thermal Properties

6. Carpet Test Comparisons

7. Percentage Error Between Burn Time Value and Calculated

Values

VI
LIST OF SYMBOLS

A Area of burn room door or corridor exit window

A| Corridor ceiling surface

A2 Corridor floor surface

Aj (2/3)A/n, portion of burn room door or exit window

area associated with one pitot tube

a Thermal diffusivity

B Subscript for burn room

C Subscript for corridor

C Specific heat, or velocity calibration constant

o o Ib^Ic Rate of change of total internal energy of the burn

room or corridor

i Subscript i for pitot tube

8 Thermal layer in heat conduction calculations

K Thermal conductivity of solids

Kg Thermal conductivity of gases

o o [_b,Lc Surface heat losses in burn room or corridor

In Natural logarithm

N Number of cribs in burn room

n Number of pitot tubes above neutral plane and in

direction of gas flow

Ap Dynamic pressure

<f>\,4>2 Angles in radiation calculation

Q Heat release per unit mass by cribs

Qg Energy transfer from the burn room to the corridor

by convection and radiation

oQc Energy transfer from the corridor to outside by

convection and radiation

vii
r Distance between dA, , dA- in radiation calculation

o o Rb>Rc Heat release rates due to combustibles in burn room

or corridor

p Density of solids

p~

c Averaged volumetric heat capacity of gases

S Control surface area, or flame spread distance

o- Stefan-Boltzman constant

t Time

T Absolute temperature

Tp Carpet flame temperature

Tg Gas temperature

Tj Gas temperature at ith pitot station

7"o Averaged fuel bed temperature

Tp Carpet pyrolysis temperature

Ts Surface temperature

Tqq Initial or ambient temperature

V Velocity

V Control volume

Vp Carpet flame spread velocity

-tj- Measured rate of weight loss

X Distance measured along the ceiling

X Distance measured along the floor

oq Heat loss per unit surface area

t Thickness of carpet

X Distance along corridor floor

Vlll
NBS CORRIDOR FIRE TESTS : ENERGY AND RADIATION MODELS*

Francis C. W. Fung, Miles R. Suchomel**, and Philip L. Oglesby

The NBS corridor fire program is a continuing

program to investigate the growth and spread

of fire and smoke through a corridor when fire

is initiated in an adjoining room. Due to

recent fires involving floor coverings [1]

,

and controversies over current floor covering

flammability test methods, floor coverings

have received special attention during the

first phase of the corridor fire program.

Results of the NBS program on corridor fires

are presented under the unifying concepts of

energy and radiation models. The major findings are:

1. One type of carpet fire hazard has

been identified as the rapid flame

spread over pile surface.

%

Work sponsored by Department of Health, Education, and

Welfare, Health Services § Mental Health Administration,

Social Security Administration, Washington, D.C. 20201.

National Bureau of Standards research associate from

Underwriters' Laboratories, Inc., 1970-1972.
2. The dominant mechanism that causes

this flame spread is energy transfer

from ceiling radiation. This is

substantiated by measurements and

calculations

.

3. Carpet evaluation by critical cumulative energy input into the corridor

has been found to be feasible and

informative in terms of heat transfer mechanisms

.

4. Finally, a radiant panel test

appears to be a promising approach

to simulate the corridor environment for second generation flooring

tests

.

Key words: Ceiling radiation; corridor fires:

critical energy input; flame spread, calculation,

and observations; floor covering evaluations:

heat balances; heat transfer mechanisms; models,

energy balance, radiation, and scaling.
1. Introduction

The NBS corridor fire program is a continuing program to

investigate the growth and spread of fire and smoke through

a corridor when fire is initiated in an adjoining room. The

program is designed to study the effects of configuration,

fuel loading, surface linings, ventilation, and other design

parameters on the spread of fire through corridors in

multiple occupancy buildings. Due to recent fires involving

floor coverings [1] , and controversies over current floor

covering flammability test methods, floor coverings have

received special attention during the first phase of the

corridor fire program.

In a preceding paper [2], presented as an introduction, the

NBS corridor fire program was discussed in the light of

available literature on corridor fires with regard to

objectives, facilities, and approaches. In addition,

qualitative discussions on effects of forced air draft, and

carpet with and without pad on corridor fire spread were

also presented.

Figures in brackets indicate the literature references at

the end of this paper.
Results of the most recent corridor fire experiements are presented in this report under the unifying concepts of

energy and radiation models. Before proceeding to present

our findings, it is necessary to review briefly the

experimental program.

2. Experimental Facilities

The corridor facility used in the NBS program is shown in

figure 1 . The corridor is 30 feet long by 8 feet wide by

8 feet high, with provisions having been made to increase

the width up to 12 feet and the height to 9 feet. The

adjustable width and height will permit the examination of

several aspect ratios. A doorway, measuring 6-1/2 feet

high by 30-1/2 inches wide, located in the side wall at

the near end of the corridor, connects the corridor to an

8 foot square by 9 foot high "burn room" where all the

fires are initiated. Two 14 inch by 6-1/2 inch vents are located near the floor level on opposite walls of the burn

room. Two access doors are located at the approximate

center of the corridor length. An exit window, measuring

70-1/4 inches high by 41-1/2 inches wide, is located at

the far end of the corridor.

The corridor is situated within a larger brick building,

with only the exit window connected to the outside. Air

4
conditioning equipment provides air flow for material

conditioning and for controlled draft whenever forced flow

is desired. The unit is capable of supplying a maximum air

flow of 7500 cfm at 75 °F, with the relative humidity at

30%. The basic construction of the corridor walls and

ceiling is 5/8-inch thick, Type "X" gypsum boards, attached

to a structure of metal studs, 16 inches on center. Between

the studs are 2-inch thick fiber glass batts for insulation.

A plywood or asbestos cement floor is placed over the brick

floor when desired. The ceiling and flooring materials to

be tested are then attached to the gypsum board ceiling and

brick subfloor, respectively.

To develop the energy and radiation models, the corridor is

equipped with thermocouples, pitot tubes, radiometers and

heat flux meters to study the corridor fires as a function

of air flow and heat transfer by radiation, convection, and

conduction.

Measurements were made of temperature, velocity, total and

radiant heat flux, weight loss of burning combustibles,

smoke density, continuous gas analysis and batch gas

sampling. Also 16 mm color motion picture coverage was provided by both a stationary camera and a roving camera. Specific sensor locations in the corridor and burn room

are shown in figures 2 and 3. In all, approximately 100

5
channels of data are recorded by high-speed data acquisition

equipment

3. General Description of Experiments

In all the experiments reported, the corridor walls were

lined with gypsum board and the corridor cross section was

8 feet by 8 feet. A typical experiment is initiated by

igniting four wood cribs, each weighing approximately

43-45 pounds, in the burn room. This yields a fire loading

of 2.7 lb/ft of burn room floor area. The cribs were

dried to a moisture content of approximately 10 per cent

before each test. (In Tests 331 and 332 crib moisture

measured 23% and 15% respectively. Energy release rates

from cribs for these tests were found to be significantly

lower.) The center crib is located on a load cell platform

so that the rate of burning can be measured and the rate of

energy release can be calculated.

The corridor ceiling materials used were gypsum, fiber, and

particle boards. The flooring materials used were brick,

carpet, vinyl asbestos tile and varnished oak floor. Where

flooring other than the brick was used an asbestos cement

board subfloor, covered with the flooring material to be

studied, extended 8 feet into the burn room. Table 1 summarizes the tests conducted, with the corridor material

6
linings and flame propagation observations listed. Table 2 describes the materials used.

Draft conditions in these tests were either by natural

convection or a forced draft of approximately 100 fpm. The

forced draft used is within the range of the air flow

encountered in corridors serving as return air plenums in

enclosed buildings.

4. Experimental Observations

While a variety of parameters have been tested in the

program, only the experiments which have the necessary and

sufficient data for analysis under the concepts of energy

and radiation models are presented for discussion in this

report. All of the experiments selected for these discussions will have the following standard conditions: ignition

by four wood cribs; walls and ceiling of gypsum board; no forced draft; and floor covering as the test material in

the corridor. Brick, a number of carpets, vinyl tile and

red oak have been used as floor coverings in experiments to

date. All of the carpets passed the pill test. A rubberized

hair felt pad used in some of the experiments did not pass

the pill test. It is important to note here that the

current federal standard does not require pads to pass the

pill test.

7
The sequence of events in an experiment involving floor

coverings usually follows the same pattern. After ignition,

cribs would be burning vigorously at about 3 minutes sending

hot gases and light smoke into the corridor along the ceiling. At about 4 to 5 minutes floor covering in the burn

room should be ignited. Smoke and gases in the corridor

would then greatly increase in intensity. If there were no floor coverings in the burn room, as in the case of reference

run Test 339 with brick floor, the crib burning rate would

reach a maximum at 7 minutes and stay at approximately that

level until 14 minutes at which time the crib fire would

begin diminishing (figure 4) . During the period of maximum

crib burning rate, the fire plume would extend from the

burn room and lick the corridor ceiling near the burn room doorway while light smoke continued to pour out from the

corridor. The air temperature at the burn room doorway

for the reference run are within about 200 °C of the ASTM

E-119 time-temperature history (figure 5).

When there are carpets in the burn room and the corridor,

the wood crib burning rate invariably has a higher initial

rate of climb and the burn room top doorway air temperature

generally climbs slightly faster than the ASTM E-119 curve

(figures 6, 7, 8, 9, and 10). The air supply to the burn

room is through the small vents in the burn room, and

through the burn room doorway. An interesting phenomenon

8
associated with carpet in the burn room is that the wood

crib burning rate invariably takes a sudden drop (figure 4)

indicating oxygen depletion in the burn room prior to flame

spread in the corridor. This is believed to be due to the

large volume of pyrolysis gases given off by the carpets,

resulting in a fuel rich atmosphere.

Table 3 compares the corridor gravimetric smoke data for a number of tests. Note the heavy smoke concentration for

Tests 340, 341, and 342 and the drop in the respective

burning rates in figure 4. Also note that Test 344 has

low smoke concentration. In fact, the level of concentration is of an order of magnitude lower than the other

carpet tests, and very comparable to the reference test.

If we go back to the burning rate plots (figure 4) , we find that Test 344 and the reference test are the only

two tests where the crib burning was not affected by the

choking or oxygen depletion phenomenon.

Shortly after the carpet ignited in the burn room a flame was observed to spread slowly over the carpet surface from

the burn room door and then to accelerate. Then the whole

corridor would "flame over" with flame following the entire

surface of the carpet. The term "flame over" has been used

to describe the observed rapid flame spread, since there is

a preferred direction in the corridor fire to distingc; ~,h

9
it from the more general flashover phenomenon. Table 4

lists the flame over initiation time for various tests.

Note with the exception of two tests, flame over initiation

times cluster around 4-1/2 to 7 minutes. Figure 11 illustrates the flame over phenomenon by plotting the carpet

surface flame spread distances against time. After a relatively slow flame initiation period, during which time

the first 5 feet of the carpets became involved, the carpet

flame would sweep to the end of the corridor. The slow

down of the flame spread over the last few feet can be

explained as an end effect. In Test 342 the smoke concen- tration is so high, choking took place inside the corridor

during flame over as shown by figure 11.

The flame over phenomenon was observed with all carpets

studied, including a wool carpet, an aromatic polyamide,

and other synthetics. However, quantitatively each carpet

fire burned differently when considering energy and flame

initiation rate. These and other findings will be discussed

in more detail in the following sections.

Examination of the carpet and combustible pad after tests

indicates that the rapid flame spread is strictly a surface

phenomenon involving only the top pile of the carpet. However, if the fire is allowed to continue to burn then the

10
pad and the subfloor become involved, contributing

additional smoke and fire.

Appendix A contains descriptive observations of significant

events that took place in the corridor for Test 330 to Test

345. Test 331 and Test 332 were omitted because of high

crib moisture content of 23% and 15% respectively.

5. Energy Balance Calculations

Due to the variation of the crib burning rates , caused by

variations of the available oxygen, and due to the narrow

spread of flame-over initiation times among some carpets,

it is felt that carpet hazard evaluation by flame spread

observation alone is not adequate.

A better definition of the hazard could be the ease with

which the carpet will ignite and start to propagate a

fire; and this brings us to the critical energy input

concept. Before proceeding with the critical energy

concept the energy balance calculation for the corridor

system must be derived.

5.1 Energy Balance Equations

To perform the energy balance calculations it is necessary

11
to conceive separately a control volume enclosing the

interior of the burn room, and a control volume enclosing

the interior of the corridor as follows:

I"-°~"~ "°~ ~~\ °

| XB RB |LB

cr

Of 4-

i B_i

Ir. Rr

I _ _ 1

LC.

| For the burn room,

o

I Qc

IB

= RB -Q

B-LB, or CD

RB

= IB+0B +LB For the corridor,

(2)

\rf www

IC =Rc+ 0b-0c-I-c (3)

Rc =Ic -Qb +Qc +Lc (4)

where subscripts B, C indicate burn room and corridor

respectively; and

r?R,Rr : heat release rates due to combustibles in

burn room or corridor.

heat losses through surfaces of walls,

ceiling, and floors by conduction,

energy transfer from the burn room to

corridor by convection and radiation.

12

V B,KC

o o Lb,L<

B
Qc

: energy transfer from the corridor to outside

by convection and radiation.

o o Ib,Ic : Tate ~f change of total internal energy of the

burn room or corridor.

The following general expressions, valid for both burn room

and the corridor, are used in the previous heat balance

equations. To avoid repetition, subscripts B and C have

been dropped in the following for more generality.

Rate of change of total internal energy is given by:

I'VR^ (5)

where

,

¥ = volume of the control volume

pi = averaged volumetric heat capacity of gases in

control volume

Tg = averaged gas temperature in control volume

75- = derivative with respect to time

To calculate the convective and radiant energy heat trans

fer through doorway and exit window the following assumptions are made:

1. Both the velocity and temperature profiles can

13
be approximated by a finite number of linear

segments

.

2. For the range of velocities encountered kinetic

energy of the gases can be neglected in the

energy balance.

3. Temperature correction on velocity measurement

behaves according to ideal gas law.

i.e. v= c7ApT (6)

where V = measured velocity

Ap = measured dynamic pressure

T = absolute temperature

C = velocity calibration constant

4. In radiation calculation blackbody emission will

be assumed. This is considered a good approximation for the net-radiation from an enclosure

fire [3] . Also no reradiation from the corridor

to the burn room will be considered.

5. In convective energy transfer the neutral plane

is taken to be at one-third of the height of the

door or window.

With these assumptions we can write down the expression

14
for convective plus radiant energy transfer.

Q = Z />iCiVj(Ti-Too)A,+<r(T

fl A-TcSA) (7)

where

A = area of burn room door or corridor exit window

n = number of pitot tubes above neutral plane and in

direction of gas flow

p\ = density of gases at a particular pitot station

Cj = specific heat of gases at a particular pitot

station (figures 2 and 3)

Vj = velocity of gas flow at a particular pitot

station (figures 2 and 3)

M = temperature of gases at a particular pitot

station (figures 2 and 3)

Aj = (2/3)A/n

cr = Stefan-Boltzman Constant

Tg = averaged gas temperature at door or window

Tq} = initial temperature

The heat release rate of wood cribs is calculated from the

measured weight loss data. Assuming that the burning rates

of the cribs are not significantly different due to the

rigorous interaction among cribs in the burn room, we can

15
write

RB

= NQ« (8)

where N= number of cribs in burn room Q= heat release per unit mass for wood, 5000 Btu/lb

[15]. This value is lower than bomb calorimeter

data due to incomplete combustion. — - measured rate of weight loss

dt

The conductive heat loss is calculated by integrating heat

loss per unit surface area over the entire control surface,

for example:

0q dS (9)

where q = the heat loss per unit surface

S = surface area of control volume

Applying integral method and assuming semi-infinite surfaces

we obtain [4] ,

and

8(t)

3K(Ts -Tcq)

S(t)

^^[/J^s-Tcp^dtl

(T

s -Tco)

ClO)

(ID

16
where K = thermal conductivity of solid

a = thermal diffusivity of solid

Ts = measured surface temperature

"!"cq = initial temperature

t = time

5.2 Results of Energy Balance Calculations

The previous expressions have been written into a Fortran

program to handle routinely energy balance calculations for

each test. The task of running the program is complicated

by the fact that, due to the wide spread of temperature and

velocity distributions spacewise and timewise throughout

the history of a corridor fire, the accuracy of the heat

balance is strongly dependent on the number of data points

included. Examples of heat balance calculations shown in

the following represent input data of approximately 100

channels at an interval of one-half minute per cycle.

Figures 12 to 16 present results of the burn room heat

balance calculations. For each test as shown the instantaneous and cumulative values of as given by equation (8) are plotted and labeled as experimental "crib energy release"

rate and cumulative curves, and the instantaneous and

cumulative sum of all the terms at right hand of equation (2) are plotted and labeled as calculated "burn room cumulative

17
energy and rate balance" curves. Agreement of cumulative

"crib energy release" and cumulative "burn room energy

balance" curves are good for Tests 339, 343, and 344. For

Tests 342 and 345 only partial load cell data were obtained.

For the initial periods where load cell data was available,

heat balance calculation and estimated energy release from

load cell data agree in trend. In Test 342 the center crib

fire went out after four minutes. Since the load cell was under the center crib and the estimated crib energy release

was based on data from that load cell, it was necessary to

terminate the crib energy calculation at approximately four

minutes. In Test 345 the instantaneous and cumulative crib

energy curves are also terminated at approximately four

minutes; this time due to load cell malfunction.

A quick inspection of figures 12 to 16 shows that all the

burn room instantaneous energy curves peak out at 60-80 x 10

Btu/minute between 4 and 6 minutes. For Tests 342, 343, and

345, the occurrence of early flame over invariably causes

the burn room energy level to drop rapidly from this peak.

This is due to the choking phenomenon discussed earlier.

For Tests 339 and 344 where flame over either did not occur

or occurred late, the burn room energy curves for both cases

3 leveled off to a steady value of 60 x 10 Btu/minute. It is

important to point out at this stage that the choking off of

the burn room energy supply does not imply a lessening of

18
fire hazards. On the contrary it means that the picking up

of activities in the corridor has added a new dimension to

the fire. As will be shown later, measurements of energy

and smoke output from the corridor indicates that when the

burn room is being choked off maximum amounts of smoke and

fire energy pour out from the corridor. Furthermore, tests

where burn room fire choke off occurred also had a comparatively higher energy output from the corridor, indicating

more intense fires. Due to the fair agreement of estimated

energy release and calculated energy transfers in the burn

room as shown by figures 12 to 16, it is felt that the

techniques for evaluating energy input and output from the

corridor as discussed in Section 5.1 yields results of

acceptable accuracy for carpet evaluation.

Figures 17 to 20 compare the burn room heat loss by conduction through walls, ceiling, and floor to the total crib

energy release rate. In all cases the burn room interior

was sprayed with a one-inch thick protective coating of

refractory material over basic masonry construction. This

monocoat refractory coating has the following thermal

properties

:

Density - p = 18.5 lb/ft 3

Thermal conductivity - K= .057 Btu/hr ft °F

Specific heat capacity - C = .2 Btu/lb °F

Thermal diffusivity - a= .0015 ft

2 /hr

19
With this refractory material as burn room interior coating

it appears that the heat loss to the burn room surfaces by

conduction is only of significant proportion during the

early phase of the burn. For the remaining interval of

the tests heat loss by conduction is roughly 15% of the

total heat release. Thus the bulk of the energy released

by the burning cribs is available as energy supply to the

corridor in the forms of convective and radiant energy

transport via the burn room doorway. Figures 21 to 25

compare the available energy to the corridor in the forms

of convective and radiant energies. For all tests compared

it appears that from an overall viewpoint the radiant

contribution to the energy supply to the corridor is

approximately 10% of the total energy transport into the

corridor. This is because the corridor only sees the

burn room fire through a small doorway. Thus apparently

the corridor receives the bulk of the heat energy from the

burn room in the form of convective heating. As discussed

in previous sections and also illustrated by the velocity

and temperature profile plots presented in Section 7, this

available convective energy from the burn room is delivered

to the corridor by way of a hot jet or stream along the

corridor ceiling.

Figures 26 to 29 present the corridor energy comparison

plots. In all cases the corridor walls and ceiling are

20
lined with 5/8-inch gypsum wallboards with fiber glass

insulation backing. The thermal properties of gypsum

board as used in heat loss calculation were as follows:

p = 60 lb/ft 3

C = .26 Btu/lb °F

a= .008 ft 2 /hr

K= .125 Btu/hr ft °F 0<T<200 °F

K= .075 Btu/hr ft °F 200 °F<T<400 °F

K= (.05 + T/16,000) Btu/hr ft °F 400 °F<T<2000 °F

Thermal properties of carpets used in heat loss and later

flame spread calculations are tabulated in table 5. It is

interesting to study the fire history by following the

corridor energy curves as shown in figures 26 to 29 in

conjunction with the observational remarks for a specific

test as presented in Appendix A. To facilitate this

comparison the flame initiation and extinguishment times

have been marked on figures 26 to 29. Heat balances of

the corridor have not been attempted due to lack of precise

information on endothermic reactions and heat release

estimates of affected carpets. This is due to a lack of

information on the rate of reaction as well as to the area

of carpet affected by the fire.

However, the significance of carpet energy contribution is

apparent when the corridor energy output curves are compared

21
with the energy input curves. In general, the following

remarks can be made about the magnitude of the various

energy levels in the corridor:

1. The peak level of corridor convective energy

output due to the carpet fire as measured at

the exit window, is typically between 80 and

100 x 10 Btu/min. This compares to 60 and

80 x 10 Btu/min of energy input into the

corridor as measured at the burn room door.

In other words, the corridor fires due to the

carpets are comparatively more intense than

the burn room crib fires during the flame

over period. From the previous approximate

range of fire intensities of energy outputs,

it would appear that the carpet fires tested

are typically 25 to 301 more intense than the

burn room fire with a fire loading of

2.7 lb/ft 2 of wood cribs.

The interactions between the corridor and burn

room fires are very well illustrated by figures

26 to 29. During the height of a corridor

carpet fire the burn room fire was invariably

choked off. Although not shown in the figures

in a less severe and slow fire, for example,

22
vinyl sheet or tiles, the burn room fire was not choked off.

3. The heat loss through corridor walls and ceiling

by conduction during the preheating and flame

initiation periods is sensitive to the rate of

energy input into the corridor. In general, heat

loss by conduction is approximately 151 of energy

input. During flame over when the energy release

in the corridor itself surges suddenly the heat

absorption by the corridor accelerates and reaches

significant proportions; during such times the

corridor energy output also surpasses the energy

input.

6. Floor Covering Evaluation by Energy Considerations

As mentioned earlier due to the variability of crib burning

rate, the narrow spread of carpet "flame over" time as well

as the "flame over" initiation time, it is felt that carpet

evaluation by flame spread observation alone does not seem

to be satisfactory. Furthermore, the flame spread phenomenon as observed in the full size corridor program and the

model duct fire experiments conducted at NBS tend to be

bimodal in nature [5] . The flame either flashed over rapidly or the flame did not propagate steadily at all.

23
In other words, the nature of flame spread observation is

either "go" or "no go". Looking for some logical way to

rank carpets studied so far in the corridor program, energy

input and output were the logical choices.

In figures 30 and 31 the cumulative convective energy inputs

from the burn room into the corridor are plotted for various

tests. Due to the corridor and burn room fire interaction

discussed previously, the shape of the energy curves behaved

differently indicating different burning behaviors. However,

from physical considerations one expects that the cumulative

magnitude of energy supply into the corridor should remain

a controlling factor. Thus if one puts down on these energy

curves the time when each carpet flame over was initiated,

one finds that each carpet did flash at a different critical

energy input. Thus by arranging the carpets according to

decreasing critical energy to flame over corresponding to

increasing fire hazard, a physically meaningful method of

evaluating carpet hazard can be arrived at.

Table 6 tabulates the results of carpet evaluation by

critical energy input concept. Some interesting observations are as follows:

1. Carpet ranking by the corridor critical energy

concept suggests a similar ranking with the

ASTM E-162 radiant panel test ranking. The

24
general trend is similar with an exception of

the order of ranking for wool and brown acrylic

carpets

.

2. Carpet ranking by the chamber critical energy

concept from model duct tests developed by

Denyes and Quintiere [5] ranks carpet in the same order as tests by the NBS rate of heat

release calorimeter.

3. On close examination, an interesting observation

is that the worst carpet on top table came out

good on bottom tests, and the worst carpet by

tests at bottom table came out rather good by

the test in top table. The differences between

the top and bottom groups of method of testing

appears to be due to the roles played by ceiling

radiation and carpet heat release. This will be

further elaborated in Section 9.

4. In the next section, it will be shown quantitatively that this good agreement of the corridor

test with the E-162 radiant panel test is not

accidental but can be explained readily in terms

of heat transfer mechanism.

25
5. Figure 32 presents comparison plots of corridor

cumulative energy outputs as measured at the

exit window. An interesting observation is

that the worst performing carpets by critical

energy input rankings also are the worst

carpets in terms of energy outputs, despite

the fact that the worst carpets also produced

the largest quantities of smoke which tended

to choke off the burn room fire. Note that

all curves are terminated at the time near

flame over.

7. Flame Spread and Ceiling Radiation

Figures 33 and 34 show some typical preheating gas temperature profiles prior to flame over inside the corridor, both

as a function of height and at 10 feet and 20 feet from

the burn room respectively. All temperature profiles

shown exhibit the same vertical stratification as a result of the hot gases leaving the corridor along the

ceiling and the cool air coming in from the far end of the

corridor. The spread in the curves are mainly due to

different flame over times in the various tests. The

next three figures, figures 35, 36, and 37, illustrate

this natural convection pattern very well. Figure 35

shows composite temperature and velocity profile plots for

26
a test where no flame over took place. Figure 36 shows

the same type of profiles for a test where flame over did occur at 11 minutes. Figure 37 shows typical sequential

temperature profile plots at the 20 foot station of the

corridor illustrating the flame over phenomenon. We see that the vertical temperature stratification persisted

during the entire preheating period, due to the cooling

draft along the floor, the air temperature immediately

above the floor surface is lower than the floor surface

temperature as shown in figures 38, 39, and 40. This

indicates that the floor is actually heated by exposure to

ceiling radiation and cooled by convection inside a corridor.

In other words, ceiling radiation plays an important role

in preheating the corridor floor in a fire.

A study of the corridor ceiling surface temperature history

as shown by figures 41 and 42 clearly indicates the intensity

of ceiling radiation. In order to demonstrate that ceiling

radiation is indeed important in carpet flame spread we performed the following radiation and flame spread

calculations

.

Consider an elemental area, dA. on the ceiling with temperature T (x' ,t) as illustrated by figure 43, we shall assume

that the ceiling temperature is uniform across the width but

not along the length and the emmissivity of ceiling is close

27
to that of a blackbody. The incident heat flux at the point

dA located at X ai ceiling is given by:dA located at X and at a given time t due to the entire

°i » ti //C^V COS <£, COS <f>~ Jft q(x jt) =($ —

y' r2 *2 dA, (12)

A|

where q(x Tt) = incident radiation at and time t

a- = Stefan-Boltzman Constant

r = position radius from dA2 to dA.

<£l,<£2

= angles shown in figure 43

Note that q(x ,t) is a function of both time and location

on the floor. For a given x and t, the above integration

is performed for a finite number of segments on the ceiling.

Given the measured experimental ceiling temperature data a numerical program [5] is written to repeat the above basic

calculation to obtain the incident radiation on the carpet

for a finite number of time intervals and a specific number

of stations along the floor. Incident radiation calculated

by this crude model agrees surprisingly well with measurements made by Gardon type radiometers as shown by figures

44, 45, and 46. In figure 47 some interesting calculated

incident radiation comparison plots are presented for a number of flooring tests. The curves are radiation versus

distance along the floor for different tests just prior

to flame over. Note that the curves follow the same general trend, the difference in magnitude is primarily

28
due to different carpets flashing at different times. If one would use results shown in figure 47 to rank carpet

according to its incident threshold radiation leading to

flame over, one would find this ranking agrees with the

rankings by critical cumulative energy input concepts.

Presumably, a laboratory test for evaluating flooring

materials should simulate a radiant distribution of this

type along the specimen.

Integrating the threshold ceiling radiation curves shown

on figure 47 along the corridor length and then dividing

by the length we obtain as averaged threshold ceiling

2 radiations 0.21, 0.39, 0.47, and .58 watt/cm for Tests

342, 340, 333, and 344 in that order. This ranks carpets

in the same order as by the corridor critical energy input

concept shown in table 6.

To further illustrate the dominant nature of ceiling radiation in causing carpet flame spread, a simple flame spread

calculation was performed by assuming that flame spread is

governed by a simple flame spread formula given by [6 and 7]

. K g (TF -Tp) vF __ (13)

per (TF -Tp)

where Vp = surface flame spread velocity

Kg = thermal conductivity of gas phase

29
/j,C,t = density, specific heat and thickness of

carpet

Tp = flame temperature

Tp = carpet pyrolysis temperature

Tq = average fuel bed temperature

Note that both the carpet thermal properties and the carpet

pyrolysis properties are involved. This formula has been

advanced both by Parker [6] and deRis [7] in their diffusion

flame theories, and has been successfully applied to correlate experimental observations by a number of authors. In

the present application only correlation with flame-over

initiation time will be considered.

For a thin fuel bed model T is assumed to be governed by:

dT (x,t)

per —— = q(x,t) , x is along corridor floor, (14)

t = 0, T =Tco

where q(x,t) is the incident radiation on the floor calculated from the radiation program. For a thick fuel bed model

T is assumed to be given by: [Appendix B]

T(x,t)=^JY[aa/

, qdt]

2 (15)

where K,a are the carpet thermal conductivity and diffusivity, respectively. Note the difference between the thick

30
and thin fuel bed formulae. In the thick fuel bed model T

o

is calculated by assuming the fuel bed as a semi-infinite

solid and for any given time by integrating the temperature

profile across the "thermal layer." Thus both the thermal

conductivity and diffusivity of the carpet are involved and

the thick fuel bed model has a time constant proportional

to y/aT

This simple flame spread model is then programmed numerically

with time varying incident heat flux calculated from the

previous radiation program and with carpet thermal properties

measured by Suchomel and Kashiwagi (table 5) and carpet

pyrolysis data input from McCarter [8]. Table 5 also lists

the carpet pyrolysis and flame temperatures used, and their

definitions. Details of the flame spread numerical program

are presented in Appendix B. Flame spread time prediction

from this numerical program checks fairly well with experimental observation with a ±201 difference. This result is

tabulated on table 7. In general it seems that the thick

fuel bed model yields better results. In these calculations

the flame spread time is obtained by considering the first

5 feet of corridor as a critical region. Similar results

would be obtained if regions further down the corridor were

considered.

As a result of this flame spread calculation one can see that

31
ceiling radiation can cause the kind of carpet flame spread

that was observed in the full scale corridor. So it is not

surprising that the E-162 radiant panel test ranks carpets

in good agreement with the full scale corridor test. It

would thus seem that to simulate the corridor environment

for a carpet test a radiant panel type test would serve the

purpose well.

8. Conclusions

The following conclusions summarize the results obtained

thus far in the NBS corridor fire program:

1. As a result of studies of the involvement of

floor coverings in corridor fires we have

identified the primary flooring fire hazard

as the rapid flame spread over the pile

surface [10]

.

2. Results of heat balance studies in the burn

room indicate that the bulk of the heat

released from burning cribs is channeled

into the corridor in the form of convective

energy. Energy transfer by radiation through

the burn room doorway is of much lower proportion, typically only one- tenth of the convec32
tive energy transfer. Transient heat loss

by conduction through walls is also found

to play a somewhat minor role when compared

to the energy transfer by ceiling jet and is

only 201 of the total energy released by the

burning cribs in the burn room.

3. Instantaneous convective energy measurements

indicate that during corridor flame over, the

maximum convective energy output from the

carpet burning in the corridor exceeds the

maximum burn room convective energy output

by 25 to 301. The fire loading due to the

carpet alone, as measured by carpet density,

is significantly lower than the 2.7 lb psf

wood crib fire loading in the burn room. This illustrates the severity of the carpet

flame over hazard.

4. Carpet evaluation by cumulative energy output

is found to be not only feasible but also

informative in terms of heat transfer mechanisms

5. Both temperature and velocity measurements

indicate that radiation rather than convection

is the dominant heat transfer mode that causes

33
carpet flame over in the corridor. This is

further substantiated by a flame spread

calculation that predicts the observed corridor

carpet flame over phenomenon when the corridor

ceiling radiation is considered as the only

heat transfer mode.

6. Both calculated and measured carpet surface

incident radiation suggest that to simulate

the corridor environment for a flooring test a radiant panel type test appears to be promising.

9. Future Work

The conclusions presented in the previous section are arrived at from the series of full scale experiments. In

order for the conclusions to be acceptable under a wider

range of parameters it is felt that perhaps they need

substantiation with other variables. Our experience in

conducting the large scale studies indicates that the

controlling phenomena that take place in building fire

spread, for example, ceiling radiation and convection

plume under the influence of floor interaction, warrants

further study. An experimental program simulating corridor

fires of varying intensity was conducted by Hinkley, et

al [16] . As a result of the study useful experimental

34
measurements and empirical correlations were obtained to

characterize the ceiling radiation and the horizontal

deflection of a vertical fire plume. However, the corridor

ceiling and floor interaction was held to a minimum by

raising the gas flame vertically away from the floor and

by leaving out the sidewalls of a corridor. It was demonstrated in this report that the horizontal deflection

of a vertical fire plume by an incombustible ceiling

dramatically increases the radiation to combustibles away

from the fire. In a follow-up study [17] ceiling radiation

and horizontal flame deflection were characterized for a number of combustible ceilings. Again the corridor ceiling

and floor interaction was held to a minimum to avoid feedback from the floor. The report shows that a combustible

ceiling lining will cause an increase in the length of the

horizontal flames and a more rapid increase in the intensity

of downward radiation than an less combustible one. Differences between combustible ceiling linings are found to be in

the rate of increase of downward radiation rather than in the

length of the horizontal flames.

Recent publications in the fire research community indicate

a degree of optimism in developing successful scale models

[10] . Thus an attempt should be made to substantiate the

large scale studies with reduced scale models. A reduced

scale program not only is much more economical, it allows

35
more systematic study of the variable because of less set

up time; and it is also more akin to laboratory scale test

developments. In a proper scaling study there should

exist four major ingredients as shown by a number of

references [10 and 11] . The Grashoff number must be

sufficiently large so that the flow will be turbulent

convection and the vertical thermal stratification is

maintained. Consideration of energy balance requires that

,1/2

5/2

energy supply must scale as H , and consideration of

momentum balance requires that velocity must scale as H

where H is the ceiling height. In addition heat loss through

the walls must be scaled so that the characteristic time of

the model and full scale be close. Effect of forced draft

on surface heat loss remains to be investigated and may be

critical to carpet surface flame spread. Forced cooling

of the corridor interior surfaces during preheating

considerably delayed flame spread in two identical corridor

tests with and without forced draft.

Added fundamental studies need to be conducted to expand

the concepts developed in this paper. For example, basic

I The Grashoff number is typically 10 in the corridor

experiments. Since Gr H , a 1 foot ceiling puts Gr

7 down to 10 . A quick check indicates that a preferably

minimum ceiling height should be probably greater than

1 foot.

36
thermal property measurements, local heat transfer studies,

and surface flame ignition analysis, etc. Kashiwagi [12]

at NBS is currently conducting carpet basic thermal

measurements. Parker [13] has also made heat release

measurements. Currently Kashiwagi [10] is also studying

radiation ignition of carpet and one dimensional surface

flame spread. Information on local flame spread on a carpet as a function of carpet material and construction

should prove to be very useful added information.

A series of small scale duct fire experiments have been

conducted at the NBS [5] with the aim of studying some of

the variables in a tunnel type test. Information has been

obtained with regard to the effect of flame spread due to

air draft, duct heights, energy input and types of carpets.

As pointed out in Section 6 comparison of results indicate

that differences exist between the corridor and the model

duct. Results from the full scale corridor are in good

agreement with the ASTM E-162 radiant panel tests whereas

the model duct experiments are in agreement with heat

release tests in ranking carpets. It has been demonstrated

in Section 7 that corridor ceiling radiation is indeed the

dominant heat transfer mechanism that causes flame over in

the corridor. Thus convective and radiative heat transfer

from the corridor carpet flame near the doorway appears

to be secondary in the initial phase of corridor heat

37
build up. The agreement of the model duct experiments

with heat release tests on the other hand points to the

importance of carpet heat release in causing flame

spread. The roles played by ceiling and carpet flame

heat transfer during preheating have been discussed in

Reference 5. It is important to point out that the degree

of interaction between these two modes of heat transfer

and the role each plays in flame spread is strongly

dependent on the relative energy inputs. Thus in order

to establish meaningful carpet fire hazard tests the

relative importance of the aforementioned heat transfer

modes and their synergistic effects must be studied and

quantified. Initial attempts to study these interesting

and complex phenomena has been initiated at NBS with a program [14] for studying a second generation radiant

panel

38
APPENDIX A

TEST OBSERVATIONS

Test 333, Brown Acrylic Carpet

Time Remarks

Min :Sec

00:00 140 grams heptane were placed beneath

each crib . 00:02 Last crib ignited.

04:00 Cribs burning vigorously and flames reaching ceiling of burn room. 05:00 Carpets smoldering in center of burn room. 05:40 Carpet burning inside burn room. 06:00 Dense smoke in burn room. 06:15 Flaming reaching down to floor in corridor.

06:40 Smoke sample taken and sample of gas taken

at 8 foot height.

07:15 Gas sample no. 2 taken at 7 foot height.

07:45 Fire on carpet in corridor.

09:24 Gas sample no. 3 taken at 4 foot height.

11:40 Flaming up the exit window.

11:40 Flaming out of window and igniting louvers.

11:55 Hose stream applied; dense smoke continues

to come out in puffs

.

12:10 Fire on floor increasing in intensity.

13:20 Hose stream applied for second time. Black

smoke continuing to come out of window.

39
Time Remarks

Mm: Sec

14:00 Flaming still coming out of burn room

and touching ceiling.

It was observed after the test that the pad was smoldering

Doorknob of north exit was observed to have melted.

40
TEST OBSERVATIONS

Test 334, Brown Acrylic With Pad,

Particle Board Ceiling, Forced Draft

Time Remarks

Min:Sec

00:40 Last crib ignited by torch ignition to

tin cans. 02:00 Cribs burning moderately, flames about

3 feet high.

03:50 Smoke starting to build up.

04:15 Carpet beneath NW crib starting to burn.

05:30 Flames starting to progress down carpetinj

and coming out of the burn room. 06:00 Smoke sampling equipment started by

Dr. Birky. Twenty-two foot and location

5 feet height.

06:35 Gas sample no. 2 taken at 7 foot height

and 20 feet down corridor.

07:00 Gas sample no. 1 taken at 8 foot height

and 20 feet down the corridor. Much

smoke coming from corridor window.

07:50 Smoke continuing to come out of the burn

room but some clearing because flood

lights becoming visible.

09:00 End of smoke sampling.

09:20 Flames flashed over and coming out of

corridor window.

09:35 Water on. 10:15 Ceiling starting to burn above burn room

door; carpeting continuing to burn.

13:00 Extinguishment continuing.

41
Time Remarks

Min:Sec

18:00 Data logger shut down. Fire fighting

efforts continuing.

End of test

42
TEST OBSERVATIONS

Test 335, Varnished Oak

Time Remarks

Mm: Sec

01:30 Flames on top of all cribs.

02:00 Flames 6 feet high.

02:45 Flames to ceiling.

03:15 Occasional flame licking out door.

03:45 Flames licking corridor ceiling.

04:45 Flames rolling down ~6 feet on ceiling.

05:00 Wood floor burning to middle of doorway.

05:30 Flames bending into burn room.

07:00 Left wall ignited, then right wall. Flames

extend down wall approximately to 3 feet

in height.

08:50 Flames out of exit window.

43
TEST OBSERVATIONS

Test 336, Vinyl Tile Floor

Time Remarks

Mm:Sec

00:20 Doors closed. All cribs burning.

02:00 Light grey smoke in corridor.

03:00 Flames to ceiling of burn room. 04:00 Occasional light ash flying into corridor.

04:40 Flames out doorway.

05:00 Floor beginning to smoke in burn room. Flames licking corridor ceiling.

05:20 Corridor ceiling flames to 8 feet distance

along corridor.

06:00 Heavy smoke, occasional sparks.

06:30 Flames on floor 1 foot out of doorway and

advancing but bent toward fire room. Flames past observation under No. 2 on ceiling. Flames to 3 feet distance on corridor floor. Mainly along joints

where tile cement vapors burning.

08:00 Flames two tiles (18") beyond E door edge

on floor. Gypsum board burning on wall

down to side doors.

09:00 Window No. 2 cracked.

13:00 Flames on floor at least to Window No. 2;

bending toward fire room. Flames still

emerging from burn room into corridor

ceiling.

44
TEST OBSERVATIONS

Test 337

Sample No. 1--Rug, No Pad

Gypsum Board Walls § Ceiling cfm Draft

Time Remarks

MinrSec

00:16 Fourth crib ignited.

05:22 Flames coming out of burn room door.

06:00 Flaming in corridor air near burn room

door. Gas sample no. 1 taken.

06:45 Gas sample no. 2 taken. Voluminous

quantities of smoke out of window but

no flaming.

24:36 Garden hose applied to cribs through

burn room vents.

29:50 Data logger shut down. End of test.

Postmortem shows burning to 5 feet and singeing to 15 feet

45
TEST OBSERVATIONS

Test 338

Brown Acrylic Carpet, No Pad, Particle Board Ceiling

Time Remarks

Mm: Sec

00:15 Last crib ignited. Small recorders 2 seconds behind dictated remarks. Data

logger 6 seconds behind dictated remarks

04:45 Flames coming out of burn room door and

hitting ceiling.

05:00 Floor in burn room starting to smoke and

charring from one crib.

05:15 Carpet ignited to the burn room. 05:31 Burn room doorway in flames (on floor).

05:39 Flaming in corridor air.

09:30 Firemen entering side of burn room and

applying garden hose.

13:55 Truck recording equipment shut down.

14:45 Data logger shut down. Carpet appears

to have burned entire length of corridor,

46
TEST OBSERVATIONS

Test 339, Reference Run, Brick Floor

Time Remarks

MinrSec

01:00 Dictation 5 seconds ahead of smaller

recorders. Dictation time same as data

logger time. Dictation time 3 seconds

ahead of movie clock.

03:45 The flames of the two cribs nearest the

door were higher than the flames of the

two cribs further from the door.

05:20 Flames starting to come out of burn room door.

06:00 Some charring of gypsum board nearest

the doorway (west wall).

08:25 Window opposite burn room door steaming

up on inside and smoke starting to come through edges of window.

09:30 Gypsum paper thoroughly charred around

burn room, but no flashover occurring.

10:15 Has sample no. 1 taken at 8 feet height

and 20 feet down corridor.

10:30 Light bulbs heard poping and flashing

in corridor.

10:50 Flashing sound continuing to be heard

from outside of corridor.

11:18 Gas sample no. 2 taken at 6 feet height

and 20 feet down corridor.

11:45 Movies commenced to be taken from window

of south wall looking into burn room.

12:20 Gas sample no. 3 taken at 4 feet height

and 20 feet down corridor.

47
Time Remarks

Mm : Sec

16:00 Minute hand of movie clock appears to be

1 minute faster than stop watch; i.e.

movie clock shows 17:00.

18:45 Movie clock corrected.

22:20 Water applied from garden hose to side of

burn room through vent hole in east wall.

25:45 Data logger shut down.

48
TEST OBSERVATIONS

Test No. 340, Blue Acrylic Carpet With Pad

Time Remarks

Min:Sec

02:00 Clock at continuous recording instruments

3 seconds behind dictation time.

03:00 Data logger 3 seconds behind dictation.

03:30 Movie ''lock coincides with dictation

time

.

04:30 Carpet ignited in burn room. 05:00 Flames on carpet reaching burn room

doorway.

05:05 Flaming in corridor air outside of burn

room. 05:27 Gas sample no. 1 taken at 8 feet height

and 20 feet down corridor (bottle marked

III). Flaming and smoke in corridor as seen through side window.

06*00 Has sample no. 2 taken at 8 feet height

and 20 feet down corridor.

06:30 Gas sample no. 3 taken at 7 feet height

and 20 feet down corridor. Flaming in

gas cloud at window.

07:05 Flames coming out of corridor window.

07:30 Initial extinguishment commencing from

outside exhaust window.

09:04 Garden hose extinguishment commencing

from side of burn room. This procedure

observed to be unnecessary because cribs

in burn room no longer burning. Wood

was blackened but still intact.

11:50 Data logger shut down.

49
Min

:Sec

00::20

02::00

04:;15

04::30

06::02

06::15

TEST OBSERVATIONS

Test 341

Wool Carpet w/Rubberized Pad; Gypsum

Board Walls and Ceiling w/Intumescent Paint

Time Remarks

Last of the four cribs ignited.

Movie clock 3 seconds behind dictation time,

Windows steaming up.

Condensation on observation windows

dissipating.

Carpet ignited in burn room. Fire on floor beyond burn room and much

smoke.

07:34 Gas sample no. 1 taken at 8 feet height

and 20 feet down corridor. Carpet fires

out; flaming on edge of pad in burn room.

08:00 Carpet in burn room reignited.

08:25 Flaming on corridor floor spreading throughout corridor.

08:50 Gas sample no. 2 taken at 8 feet height

and 20 feet down corridor.

09:11 Gas sample no. 3 taken at 7 feet height

and 20 feet down corridor.

09:27 Gas sample no. 4 taken at 4 feet height

and 20 feet down corridor. Flaming

observed to have spread across carpet

surface.

09:30 Flames out of window.

10:28 Garden hose extinguishment commencing

into side of burn room.

50
Time Remarks

Min:Sec

12:00 Extinguishment of flames on carpet surface

commencing from corridor access door.

13:54 Data logger shut down.

51
TEST OBSERVATIONS

Test 342

Gold Nylon With Integrated Rubber Pad

Time Remarks

Min :Sec

00:17 Last crib ignited.

01:00 Observation windows commenced to steam

over.

03:00 Steaming clearing up.

03:50 Some black smoke appearing in corridor

air

04:30 Flaming in upper part of corridor air.

04:45 Carpet on fire. Gas sample no. 1

04:50 Flaming in corridor air.

05:00 Gas sample no. 2 taken.

05:22 Gas sample no. 3 taken.

05:38 Gas sample no. 4 taken.

06:21 Flames commencing to extend beyond

corridor exhaust window.

08:10 Extinguishment commencing with 1-1/2 inch

hose line into corridor from exhaust

window.

10:15 Extinguishment commencing into side of

burn room by means of garden hose. Cribs

not burned down. Center crib already out,

52
TEST OBSERVATIONS

Test 343, Wool Carpet, No Pad

Remarks

Sample no. 1 taken (gas) 8 feet.

Rug in burn room ignited. Flames bending

inwards towards center of burn room. Flaming in corridor air.

Gas sample no. 2 taken (8 feet).

Flaming on corridor floor.

Gas sample no. 3 (7 feet).

Light bulbs commencing to "pop" in corridor,

Black smoke in corridor.

Gas sample no. 4 taken (4 feet).

Burning of walls and rug.

Smoke clearing but cribs continuing to

burn in burn room. 10:18 Extinguishment commencing from side of

burn room by means of garden hose.

Time

Min 'Sec

03 57

04 30

04 43

04 57

05 00

05 07

05 10

05 15

05 27

07 00

07 45

53
TEST OBSERVATIONS

Test 344, Aromatic Polyamide Carpet, No Pad

Time Remarks

Min:Sec

01:00 All cribs burning.

02:00 Light smoke in corridor.

03:00 Carpet burning in burn room. 05:00 Gypsum board burning and charring near

burn room. 06:00 Light smoke inside corridor.

08:10 Carpet burning outside burn room to a distance of 2 to 3 feet.

10:10 Ceiling flame continues to lick vigorously

opposite burn room. 10:45 Burning of gypsum paper and paint began

to spread.

12:00 Flames at top of window (?) D.G.

12:45 Ceiling, wall gypsum board completely

involved; beginning of decisive flashover.

14:40 Heavy smoke, flaming around exit window.

Carpet burning up to a few feet from

exit window. Extinguishment began.

54
TEST OBSERVATIONS

Test 345

Brown Wool Rug-No Pad-0 cfm- -Intumescent Fire Retardant

Paint on Gypsum Board Walls and Ceiling

Time Remarks

Mm: Sec

02:45 Slight smoke build-up in corridor air.

03:45 Cribs burning intensely- -no fire on

carpet.

04:10 Flames starting to come out of top of

burn room door.

04:20 Carpet in burn room starting to smolder.

04:25 Carpet in burn room ignited.

04:30 Intense flaming in burn room air.

04:42 Much light smoke in corridor.

04:45 Steam on corridor observation windows.

05:08 Gas sample no. 1 taken at 8 feet height

and 20 feet down corridor.

06:20 Light bulbs popping in corridor.

06:30 Much gray smoke pouring out of corridor

exhaust window.

06:45 Flaming observed in corridor air from

outside exhaust.

06:55 Flaming observed through smoke near corridor ceiling. No flaming pouring

out of exhaust window.

07:50 All flaming observed to be in air

above carpeting.

07:55 Much flaming in corridor air. Smoke

started to clear.

08:05 Carpet burning (in flames) in corridor.

55
Time Remarks

Min:Sec

08:10 Second gas sample taken.

08:20 Third gas sample taken.

08:30 Last gas sample taken.

09:15 Water applied to cribs in burn room

through vents in burn room walls.

10:10 Flaming subsiding appreciably in corridor

without applying water (except in burn

room)

11:30 <

T ood that supported clock in corridor

still burning. Extinguished with

garden hose spray.

14:00 VIDAR recording equipment shut down.

56
APPENDIX B FLAME SPREAD CALCULATIONS

B.l Flame Spread Calculations

From reference [4] the temperature profile inside a semiinfinite solid with one face exposed to a time varying

heat flux is given by

T(x,t)-Tco = ^(l-y)3

(Bi)

where

T(x,t) = the temperature distribution

T<X) = initial temperature

P

= the external heat flux

K = thermal conductivity of the solid

X = the x coordinate

8 = the thermal layer and is given by

1

a dtl

q Jo

where a is the thermal diffusivity,

8 = 273 [f/W

To obtain the average semi-infinite fuel bed temperature,

let

To= i Jo T(x> t) dx

(B2)

57
substituting (Bl) into (B2) and integrate one obtains

equation (15) in the following form,

To^-TTfv W'S dt F +Too (B3)

2-73 K

Equations (13) and (14) and equations (13) and (15) from

Section 7 can be solved simultaneously to obtain the flame

spread velocity. Integrating the velocity one obtains the

flame spread distance along the corridor. For thin fuel

bed model an explicit expression for the flame spread

distance can be obtained and is shown as follows,

Tp-T

5

L VpkD dt

S = ^(TF -TP

) ln[ 3dS}

] (B4)

For the thick fuel bed model, equations (14) and (15) are combined and integrated numerically in the following

Fortran program. Both equation (B4) and the numerical

calculation for the thick fuel bed flame spread distance

show that the flame spread distances will escalate and

exhibit "flame over" behaviors.

58
B.2 Flame Spread Numerical Program

A Fortran program was written to implement the flame spread

calculations. The program was broken down into five main

divisions. The first division was data input of the

thermal properties, radiation, heat flux, and various

timing data.

The second part was an algorithm to linearly expand the

radiation data into integer amounts of subdivisions in

order to increase the resolution of the flame spread

formulas. (This was necessary procedure in order to

detect the rapid change in velocity when TO approached

TV.)* The algorithms first computed the intercept and

slope of a linear curve between two half minute interval

input data. The half minute sampling interval was then

reduced to correspond to the finer interval size. A time

variable was then used in the linear equation to generate

the expanded data.

Part 3 was the primary integration routines, which generated

the integrated radiation flux (TQDOT) , the thin fuel

* The alphabetical symbols used in this section refer

to portions of the computer code.

59
temperature (TO) and the semi-infinite fuel bed temperature (TOSI). The integration algorithms were of the

backward difference trapezoidal form, for example,

integrated value between interval "j" "j-1" for the

function F(j )

Int(i) ;(F(i)+FlH))Vi

Control parameters MAX1 and MAX2 were defined to determine

the maximum time for TO and TOSI less or equal to TV,

after which the flame spread formulas have no meaningful

significance.

Part 4 and 5 were the final algorithms which computed the

flame spread velocities (VI) and (V1SI) , and the distances

for thin bed and thin fuel bed models.

Table 7 is a summary of the flame spread calculations

versus the observation burning times. The percentage is

based relative to the observation "flame over" initiation

time by:

(calculated - burn time value) , nf)! % error = burn time value x

The mean percentage error for the tests evaluated in Table

7 is approximately 20%.

60
REFERENCES

Sears, A. B. , Jr., Nursing Home Fire, Marietta, Ohio,

Fire Journal, 5, 1970.

Fung, F. C. W. , Suchomel, M. R. , Oglesby, P. L., The

NBS Program on Corridor Fires, Fire Journal, 1972.

Beyreis , J. R. , Monsen, H. W. , Abbasi, A. F. , Properties

of Wood Crib Flames, Fire Technology, 5, 1971.

Goodman, T. R. , The Heat Balance Integral-Further

Considerations and Refinements, Journal of Heat

Transfer, 2, 1961.

Denyes , W. , Quintiere, J., Experimental and Analytical

Studies of Floor Covering Flammability With a Model

Corridor, National Bureau of Standards Report No.

NBSIR 73-199, May 1973.

Parker, W. J., Flame Spread Model for Cellulosic

Materials, 1969 Meeting Central States Section, The

Combustion Institute, University of Minnesota,

March 1969.

deRis , J. N. , The Spread of a Laminar Diffusion Flame,

Twelfth Symposium (International) on Combustion, The

Combustion Institute, p. 241, 1969.

McCarter, R. , unpublished results, National Bureau

of Standards , 1972.

Fire Program, ASTM Symposium on the Flammability of

61
Textiles, Los Angeles, California, 6, 1972.

10. Heskestad, G. , Modeling of Enclosure Fires, FactoryMutual Research Corporation Research Report, September

1972.

11. Alpert , R. L . , Fire Induced Turbulent Ceiling-Jet,

Factory Mutual Research Corporation Serial No. 19722-2,

pp. 43-45, May 1972.

12. Kashiwagi , T. , unpublished results, National Bureau of

Standards, 1972.

13. Parker, W. J., Long, M. E. , Development of a Heat

Release Rate Calorimeter at NBS, ASTM STP 502, 1971.

14. Hartzell, L. G. , unpublished results, National Bureau

of Standards , 1972.

15. Kawagoe , K. , Sekine, T. , Estimation of Fire TemperatureTime Curve in Rooms, BRI Report No. 11, Ministry of

Construction, Japan, 6, 1963.

16. Hinkley, P. L. , Wraight, H. G. H. , Theobald, C. R.

The Contribution of Flames Under Ceilings to Fire

Spread in Compartments, Part I, Incombustible

Ceilings, JFRO, 1968.

17. Hinkley, P. L. , Wraight, H. , The Contribution of Flames

Under Ceilings to Fire Spread in Compartments, Part II,

Combustible Ceiling Linings, JFRO, January 1969.

62
The authors acknowledge the contributions of the following

NBS staff and laboratory personnel:

James S. Steel, physicist, was responsible for the installation of the instrumentation and the data acquisition

equipment.

William H. Bailey, supervisory technician, was in charge

of erection and dismantling of the corridor structure.

Thomas F. Maher, Melvin E. Womble, and Richard H. Zile,

engineering technicians, participated in the maintenance

and calibration of instrumentations and erection and

dismantling of the corridor structure.

J. Newton Breese, physical science aid, participated in

the preparation of the graphs.

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110
Table 1

Summary of Corridor Flame Observations

Test No. Corridor Test Conditions Observations

Fl ame* Traverse

Ceiling Floor Wall Airflow Time

329 Particle

board Brick Painted gypsum

board

6200 cfm Flame reached end of corridor

along ceiling at 12:00.

(tnin:sec

330 Particle

board Sample No. 1 rug & pad Painted gypsum

board

Ceiling ignited at 2:30; carpet

ignited at 2:35. Flame reached

end of corridor at 2:55.

0:25

332 Particle

board Brick Painted gypsum

board

Ceiling flame reached end of corridor at 9:20. Carpet

sample at 1 '8". Station

ignited at 10:15.

1:30

333 Painted gypsum

board

Sample No. 1 rug & pad Painted gypsum

board

Flaming in corridor air at 6:00; flaming on carpet at

7:45.

334 Particle

board

Sample No. 1 rug & pad Painted

gypsum

board

6550 cfm Heavy smoke in corridor at

7:00. Flaming in corridor

reached end of corridor at

9:20.

335 Painted gypsum

board

Varnished

oak Painted gypsum

board

Corridor qases ignited at 5:00; flame reached end of corridor

at 8:50.

3:50

336 Painted

gypsum

board

Vinyl asbestos

tile

Painted gypsum

board

Flaming on floor outside burn room door at 6:30; flame on floor spread to 10 ft station

at 8:40.

NA

337 Painted gypsum

Doara

Sample No. 1 rug w/o pad Painted gypsum

board

Carpet near burn room door ignited at 7:00. Spontaneous

ignition of carpet up to 15 ft station. Fire on carpet went out at 8:00.

NA

Particle Sample No. 1 Painted

board rug w/o pad gypsum

board

Flaming in side corridor at

5:40. Flaming reached end

of corridor at 7:00.

Painted gypsum

Painted gypsum

board

No fire in corridor; slight charring of gypsum paper near burn room. Air and wall temperatures reached steady state at approximately 7 minutes

.

Mineral Sample No. 3 Mineral base rug & pad base board board

Flames on carpet near burn room door at 5:00. Flame reached end of corridor at 7:05.

Painted Sample No. 10 Painted gypsum (wool) w/ pad gypsum

board board

Flames on carpet beyond burn

room door at 6:15. Carpet

fire out at 7:34. Carpet reignited at 8:00. Flame reached end of corridor at 9:30.

Painted Sample No. 9 Painted gypsum (nylon) w/ gypsum

board integral pad board

Carpet on fire at 4:45. Flaming 1:30

in corridor at 4:50. Flame reached end of corridor at 6:20.

Painted gypsum

board

Sample No. 10 w/o pad Painted gypsum

board

Carpet ignited at 4:30. Flaming on corridor floor at 5:00. Flame reached end of corridor at 5:55.0:55

Painted Sample No. 12 gypsum rug, no pad Painted gypsum

5:00 gypsum board burning near

burn room. 8:10 carpet burning outside Durn room to a distance of 2 to 3 feet. 10:45 burning of gypsum paper oegan

spreading. 12:00 flame over. 13:50 flame readied end of corridor.

Painted gypsumSample No. 10 Painted

rug, no pad gypsum board

4:10 flame out of burn room. 4:25 carpet in burn room ignited. 7:00 fire in corridor

air. 7:50 flame reached end of

corri dor.

* Flame traverse time: time for flame to travel the whole length of the corridor {beginning of corridor involvement to flame reached end of corridor).

** Not fire-retardant paint.

*** Corridor flaming initiation not recorded. Ill
MATERIAL

Corridor Walls Gypsum board

Corridor Ceiling

Gypsum board

Sugar cane pulp board

Particle board

Mineral base board

Corridor Floor

Brick

Carpet No. 1 and pad

Carpet No. 3 and pad

Carpet No. 9

Carpet No. 10

Carpet No. 12

Oak floor, varnished

Vinyl asbestos

tile

Burn Room

Refractory coating

TABLE 2

MATERIAL DESCRIPTION

FLAME SPREAD

(by ASTM E162)

13

13

74(1) 222(2)

102

145 w/o pad

150 with pad

445 with pad

284 integrated pad

64 w/o pad

119 with pad

51.3 w/o pad

109

122

DESCRIPTION

5/8 inch, type X gypsum

wallboard, painted with

intumescent white paint

5/8 inch, type X gypsum

wallboard, painted with

intumescent white paint

(1) treated side

(2) untreated side

Pressed wood with resin

Ceramic ceiling material with tunnel flame spread

rating under 25

Brick set in sand as basic

subf loor

Brown, 100% acrylic carpet

1/4 inch low pile, 10-12 oz/sq yd. Pad /'rubberized"

surfaces with jute filler

0.46 inch thick.

Blue acrylic carpet 1/10- 5/16 inch low pile, 32 ozsq yd. Pad same as above.

Gold nylon, 1/8 inch low pile, pile weight 20 oz/yd

100% wool, 7/32 inch low pile, pile weight 38 oz/yd , pad same as above.

Red, 100% aromatic polyamide, 1/8" low pile, pile

weight 25 oz/yd 2

Tongue-and-groove hard oak

floor with two coats spar varnish, laid over 1/2 inch thick plywood.

Asbestos tile applied to plywood floor with black

tile adhesive.

1/4 inch high temperature

cement sprayed to basic

cement block walls and cement ceiling.

112
TABLE 3

Smoke in Corridor Tests

(Measured by Gravimetric Method at 150°C)'

Test No. Time

minutes

Concentration

mg/S,

339 (BLANK)

340 (Bl. Acryl. C/P)

341 (Wool/P)

342 (G. Nylon)

344 (Aromatic Polyamide)

5.0 - 6.0

14

19

5.0

7.0 - 8.0

8.0 - 9.0

4.0 _ 5

9 - 9.5

12 - 13

2.5 _ 3 4.2 - 4.7

6.0 - 6.5

8.5 - 8.9

3.5 _ 4.0

7 - 9 9 - 11.5

0.2

0.2

0.1

0.3

11.5

6.0

0.13

1.3

.07

0.1

0.3

5.1

11.2

0.24

0.13

0.13

1. Data provided by T. G. Lee, Building Fires and Safety Section, Center

for Building Technology, National Bureau of Standards.

2. Samples collected at mid-height of corridor exit window. Two parameters,

the time to reach maximum smoke and the level of minimum smoke, are of

interest.

113
TABLE 4

"FLAME OVER" INITIATION TIME

(All tests with FR painted gypsum walls and ceiling,

and natural draft except as noted)

Test No. Flooring Time

330 No. 1 Rug and Pad 2:35

(particle board ceiling)

333 No. 1 Rug and Pad 7:45

334 No. 1 Rug and Pad 7:00

(particle board ceiling,

100 fpm forced draft)

335 Varnished Oak 5:00

336 Vinyl Asbestos Tiles 6:30

337 No. 1 Rug, No Pad 7:00

338 No. 1 Rug, No Pad 5:40

(particle board ceiling)

340 No. 3 Rug and Pad 4:30

(mineral base board walls and

ceiling)

341 No. 10 Rug and Pad 8:00

342 No. 9 Rug, Integral Pad 4:45

343* No. 10 Rug, No Pad 4:30

344 No. 12 Carpet, No Pad 12:00

345 No. 10 Rug, No Pad 7:00

*Walls and ceiling painted with white rubber base paint.

114
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115
TABLE 6

Experiment

Number

340

342

335

345

343

341

333

344

Experiment

Number

333

340

342

343

CARPET TEST COMPARISONS

a. Ranking by Corridor

Flooring

Material

Blue acrylic w/pad

Nylon w/integral pad

Varnished oak

Wool, no pad

Wool, no pad

Wool w/pad

Brown acrylic w/pad

Aromatic polyamide, no pad

b. Ranking by Rate of Heat Release

Corridor Test

Critical Cumulative

Energy, Btu

ASTM

E-162

Rating

.65 X io

5 445

.75 X 10

5 284

1.2 X io

5 109

1.4 X io

5 64

1.4 X io

5 64

1.6 X io

5 119

2.1 X IO

5 145

5.4 X io 5 51

Flooring

Material

ASTM

E-84

Brown acrylic w/pad 298

Blue acrylic w/pad

Nylon w/integral pad 237

Wool, no pad 50

Heat Release

Joules /cm *

8200

6493

4901

3400

Flammability ** Test Model

Critical Heat,

Btu/min

300

400

600

1250

* As determined by the NBS Rate of Heat Release Calorimeter

** Chamber type carpet flammability test developed at NBS.

116
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117

FORM NBS-H4A (1-71) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN-7942. Gov t Accession No.3. Recipient's Accession No.

4. TITLE AND SUBTITLE

NBS CORRIDOR FIRE TESTS: ENERGY AND RADIATION MODELS

5. Publication Date October 1973

6. Performing Organization Code

7. AUTHOR(S)

Francis C. W. Fung, Miles R. Suchomel and Philip L. Oglesby

8. Performing Organization

10. Project/Task/Work Unit No. 4906401

9. PERFORMING ORGANIZATION NAME AND ADDRESS NATIONAL BUREAU OF STANDARDS DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

13. Type of Report & Period Covered Interim

July 1971 - Jan. 1973

I Soonsorinp Appncv fn^p

12. Sponsoring Organization Name and Address Department of Health, Education, and Welfare

Health Services & Mental Health Administration

Social Security Administration

Washington, D. C. 20201

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

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.) The NBS corridor fire program is a continuing program to investigate the growth and

spread of fire and smoke through a corridor when fire is initiated in an adjoining

room. Due to recent fires involving floor coverings [1], and controversies over

current floor covering flammability test methods, floor coverings have received

special attention during the first phase of the corridor fire program. Results of

the NBS program on corridor fires are presented under the unifying concepts of energy

and radiation models. The major findings are:

1. One type of carpet fire hazard has been identified as the rapid

flame spread over pile surface.

2. The dominant mechanism that causes this flame spread is energy

transfer from ceiling radiation. This is substantiated by

measurements and calculations.

3. Carpet evaluation by critical cumulative energy input into the

corridor has been found to be feasible and informative in terms

of heat transfer mechanisms.

4. Finally, a radiant panel test appears to be a promising approach

to simulate the corridor environment for second generation

flooring tests.

17. key words (Alphabetical order, separated by semicolons) Ceiling radiation; corridor f ires ; critical

energy input; flame spread, calculation, and observations; floor covering evaluations;

heat balances; heat transfer mechanisms; models, energy balance, radiation, and scaling

18. AVAILABILITY STATEMENT

|%1 UNLIMITED.

I I FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

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(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

127

22. Price

USCOMM-OC 66244-P71

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