NBSIR 73-200

A Model Corridor for the

Study of the Flammability of

Floor Coverings

Wells Denyes

Research Associate

Man-Made Fiber Producers Association, Inc. Washington, D. C. 20036

and

James W. Raines

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

May 1973

Final Report

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 73-200

A MODEL CORRIDOR FOR THE

STUDY OF THE FLAMMABILITY OF

FLOOR COVERINGS

Wells Denyes

Research Associate

Man-Made Fiber Producers Association, Inc. Washington, D. C. 20036

and

James W. Raines

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

May 1973

Final Report

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent. Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts. Director
ACKNOWLEDGEMENT

The authors wish to thank the following people for their contributions

to this program.

Dr. James Quintiere and Mr. Philip Oglesby of the Combustion Section

for their design of the special thermal flux sensors.

Mr. William Zahavi of the Computer Services Division for computer

programming assistance.

Messrs. Clark and McKneely of the Plant Division for physical design

for the air control system.

Messrs. Spangenberg, Ruegg, and Allion of the Engineering Mechanics

Division for their help in designing the air flow system.

Mr. William Bailey and his staff of the Center for Building Technology

for their help in setting up the test facility.

il
PREFACE

This report describes the apparatus constructed for the study of one of several concepts examined at the National Bureau of Standards for

a floor covering f laramability test which could be related to performance

in real fire conditions. We believe that the work carried out in this

facility provides substantial support for the critical energy concept as

a measure of hazard potential for floor coverings. A test method based

on this concept but substituting a radiant panel as the energy flux source

is now being investigated in detail at NBS.

J. E. Clark

Chief, Fire Technology Division

June 1973

iii
CONTENTS

Page

1. INTRODUCTION 1

2. DESIGN OF FACILITY 1

3. CONSTRUCTION 2

4. INSTRUMENTATION 15

4.1 Data Collection 15

4.2 Data Reduction 15

4.3 Sensors 20

4.4 Other Measurements 25

5. TESTING PROCEDURE 25

6. TEST REPEATABILITY 29

7. CONCLUSIONS 33

8. REFERENCES ' 35

iv
1. INTRODUCTION

In April 1971 a mandatory carpet f lammabillty standard DOC FF 1-70

[1] became effective. This standard requires that all carpets entering

commerce in the United States pass the methenamine tablet test. This test was designed to ban from commerce those carpets which could be ignited by

relatively small sources such as cigarettes, matches, or embers from

fireplaces. At this same time many regulatory agencies of federal, state,

and local governments were expressing a need for a more severe flammability

test to control floor coverings to be used in public buildings, especially

floor coverings used in exits, corridors, and stairways.

Several test methods have been considered and a few are being used

on a limited basis to regulate carpet flammability. Among those considered

have been ASTM E84-68 Tunnel Test [2], UL Subject 992 Floor Covering

Chamber Test [3], ASTM E162-67 Radiant Panel Test [4], and Armstrong Cork

Company Flooring Radiant Panel [5]. At the present time, none of these

test methods provides repeatability nor has been shown to be a reliable

measure of the contribution of floor coverings to the hazards of building

fires.

In an effort to fill this need, a Research Associate program sponsored

by Man-Made Fiber Producers Association, Inc. was begun at the National

Bureau of Standards in July 1971. The objective of this program was to

develop a laboratory test procedure which would provide a high degree of

confidence in prediction of flammability and flame propagation characteristics of floor coverings in full-scale real-life situations.

It is the purpose of this report to summarize the design, construction, instrumentation and operation of the "model corridor" facility that was used for this program. A separate report, "Experimental and Analytical

Studies of Floor Covering Flammability With A Model Corridor" [6] discusses

the program that has been carried out.

2. DESIGN OF FACILITY

The site selected for the location of the facility was at the

National Bureau of Standards located in Washington, D. C. in the

basement room of Building 65.

A model corridor was designed in which a number of the parameters

expected to influence flame spread over floor coverings could be controlled

and their effects quantified. Variables selected for investigation

included:

1) Model dimensions (up to 8 ft in length, 4 ft in width, and

4 ft in height)

1
2) Input air velocity (50 to 300 ft per minute).

3) Rate of heat input (up to 2000 Btu per minute).

Figure 1 is a schematic diagram of the model corridor. Crosssectional dimensions in the test section are varied by relocating the

movable wall and ceiling located within the section. Input air velocity

is varied by adjusting the pressure drop across the multiple hole orifice

plate. Rate of heat input is varied by changing the rate of natural gas

feed to the diffusion flame burner which impinges on the floor mounted

samples

.

A 20-channel data acquisition system with rapid response time was designed so that temperature gradients and energy fluxes could be

recorded. A computer program was developed which provided rapid data

conversion.

Both the construction of the test facility and the instrumentation

are described in detail in the following sections.

3. CONSTRUCTION

Construction of the model corridor was carried out in four parts:

(1) design and assembly of the test section.

(2) design and assembly of the air control section.

(3) design and assembly of the exhaust duct.

(4) assembly of the total system.

The overall test section is a 4 ft x 4 ft x 8 ft duct containing an inner movable ceiling and wall that allows the interior working dimension

to be reduced in both height and width. The framework is made of slotted

steel angle, mitered and butt welded at all corners. The top, back wall,

and bottom are made of 4 ft x 8 ft x 3/8 in asbestos board bolted directly

to the outside of the slotted angle frame. The door, also made of asbestos

board, is attached with a piano hinge at the top to allow easy accessibility to the test section. The framework of the door opening is covered

with asbestos paper attached with furnace cement to provide a gasket. The

exterior of the door is framed with slotted angle to give it strength and

ridigity. Three 95% silica plate glass windows were placed in the door

6 in above the floor level to allow viewing of tests. A lattice framework at the entrance and exit of the test section provide support for

the asbestos board movable interior wall and ceiling. Figure 2 shows

the test section with the door open and the movable wall and ceiling

installed. The actual dimension of the test section as shown in the

photograph is reduced to 24 in wide x 11 in high. Figure 3 shows the

test section with the door closed.

2
3
4 Ih
5
The burner is mounted in the center of the entrance of the test

section. When the test section width is altered the burner is always

placed in the center. It is adjustable vertically so that for varying

thicknesses of floor covering the burner is always 1/2 in above the

surface of the sample. Gas flow to the burner is indicated by a flowmeter, and measured by a totalizing meter (figure 4). The burner is

of the same design as used in the Underwriters' Laboratory Subject 992

Floor Covering Chamber Test [3]. It is a diffusion type burner and

impinges on the floor covering surface at an angle of 27° from the

horizontal. Experimentation has shown that this angle is not critical.

The burner is 6 in wide and the flame is approximately 8 in wide.

One of the parameters chosen for the test program was the rate of

heat input to the test section. Natural gas with an energy content of

1020 Btu/ft-^ was supplied to the burner. Table 1 shows the relationship

between the reading of the flowmeter used to monitor the gas flow and

the Btu input from the burner. The burner is ignited with an electric

spark generated by a transformer.

The air control section posed many design problems which had to be

solved before construction could be started. A stable, uniform, tempered

air flow that could be varied from 50 to 300 ft per minute was required.

This requirement calls for a maximum of 4800 cubic feet of air per minute.

The room in which the section was to be located was small, measuring

approximately 20 ft x 29 ft x 8 ft. This meant that additional air had

to be drawn from another source. A 4 ft x 6 ft access door in the ceiling,

which opened up into a large storage room containing some 50,000 cubic

feet of space, was utilized to provide the additional tempered, but not

conditioned, air for the system.

It was determined that because of the limited space available a 90

turn in air flow was necessary to provide a stable, uniform air flow.

Also, air should flow through the entire test section at all times, even when the movable interior wall and ceiling are in place. This would make

air velocity control easier.

The question of whether or not air flow would be uniform over a small

section arose. There was concern in the early design of the system that

a fire in the small test section would disrupt the air flow pattern, but

later experimentation showed this was not the case. The pressure drop

created by the fire was small compared to the pressure drop across the

rest of the system and air flow remained stable. This information was verified by checking the air velocity over the total cross-sectional area

of the test section with a hot wire anemometer before and during test runs.

Another question that had to be answered was whether air should be

blown into the system, or whether an exhaust fan would be suitable. The

corrosive nature of the gases involved made it desirable to blow air into

the system, although this did require extra care in sealing the test

section. Additionally, with the forced air system it was possible to

control air flow at ambient conditions rather than at the varying temperatures and densities produced by a fire.

6
7

TABLE 1

GAS FLOW RATE*

Btu/min Flovmieter Setting

250 .32

300 .38

350 .44

400 .51

450 .58

500 .64

600 .76

750 .96

1000 1.27

1250 1.59

1500 1.91

Calibrated for natural gas with a content of 1020 Btu/ft .

The blower selected was a load limit fan with a single inlet. Air

intake was controlled by variable inlet vanes. The blower was designed

to operate at a 4 in water pressure drop. A D.C. motor driven fan would

have allowed simpler control of the air at the intake, but cost, delivery

time, and non-availability of D.C. power determined that the A.C. blower

assembly described above should be installed.

An orifice plate was determined to be the best method of controlling

air flow. It serves two functions. It creates a pressure drop upstream

from the test section which is very large compared to the pressure drop

created by the fire in the test section. This resulted in a constant air

flow rate to the test section during a test. Air flow measurements taken

during Carpet Flammability Tests (hereafter referred as CFT) 286-291

verified this flow behavior. An appreciable change in air velocity only

occurred well after "flameover" (i.e. a rapidly accelerating flame front

leading to total involvement of the sample) . These data are shown in

table 2. The other function served by the orifice plate is to control

the quantity of air flow. The orifice plate is a 4 ft x 4 ft x 1/4 in

aluminum plate containing 100 holes evenly distributed in a 10 x 10 array.

Hole diameters and spacing were calculated so that with a pressure drop

of 4 in of water the total flow of air would be 4800 ft^ per minute. When

translated across a 4 ft x 4 ft cross section the average air velocity is

300 ft per minute. The pressure drop is monitored with an inclined

manometer with a range of 0-6 in of water. Before the experimental program

began, the pressure differential around the perimeter of the orifice plate

was measured. These measurements showed a uniform pressure drop across

the entire surface. By plugging selected holes distributed uniformly over

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the orifice plate and adjusting the pressure drop by means of variable

inlet vanes of the blower, exact air velocities within the desired range

can be obtained. Table 3 contains information needed to calculate air

velocity.

With these conditions in mind, the air control system was designed

and built in the following manner. The first section consisted of a

6 ft X 6 ft X 7 ft box to act as a settling chamber for the intake air.

A baffle was placed immediately in front of the blower discharge to diffuse

the air. At the exit end of this settling chamber two galvanized wire

screens were installed to further diffuse the air. The second section is

a transition section (figure 1) which was installed to reduce the cross- sectional dimensions from 6 ft x 6 ft to the desired A ft x 4 ft. The

previously discussed orifice plate was installed at the end of this section.

The third section is used to make the required 90** turn. Double reflecting

turning vanes are used to move the air around this corner. There are also

four, fine mesh screens used to further diffuse the air so that lateral

pressure differences across the test section do not exist. The fourth

section has a 4 ft x 4 ft x 2 in piece of aluminum honeycomb that

functions as an air flow straightener . The cells are hexagonal, measuring

1/4 in across the flat surfaces. The output from this section empties

into the test section as described earlier. Figure 6 shows the

construction drawings of the completed air control assembly.

After completing the construction of the air flow system velocity

measurements were made at many locations. Some of the screens described

above were installed to correct various flow pattern problems. After

final construction a stable, uniform air flow was achieved. During the

experimental program air flow was not monitored continuously but was

checked at random intervals to insure good air flow.

Following the test section another reducing section was used to

further reduce the cross -sectional measurements to2ftx2ft. This

transition is 4 ft long and is made from 2 in x 2 in steel angle covered

with asbestos board.

The final section is a 2 ft x 2 ft steel duct which shuttles the

exhaust out of the model corridor and into the atmosphere. In order to

reach the outside of the building the duct has to make a 2 ft rise.

Figure 7 shows how this was accomplished. There was some fear that a chimney effect might be created by even the small rise in the exhaust

duct, however, this was not the case. Air velocity measurements were

taken at the exit end of the test section both with and without the burner

ignited. No change in air velocity was noticed.

The first experiments demonstrated the need for some device that

would prevent edge burning of the test samples. Initially, tackless

stripping was used to hold the samples down. It did not prevent edge

burning, and had to be replaced after each test. Curbs, 1 in x 1 in,

made of asbestos board were also tried. They were clamped in place on

top of the carpet next to the walls. Edge burning was not completely

11
TABLE 3

AIR FLOW IN MODEL CORRIDOR

Pressure Across Orifice Plate (in. of Water)

Holes in Orifice Plate

100 80 60 20 10

300 1^"

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50

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25

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1.0"

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2.8"

Air flov (ft/min) = Holes x Pres. x 1.5

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inhibited and eventually these curbs were replaced with 1 in x 1 in

rectangular steel tubing which has performed satisfactorily. They

successfully held the carpet in place and inhibited edge burning.

Some tests were conducted with a sample adherred to the floor. This was done to determine the effect of whether carpets glued down would

perform differently in a fire environment than normally installed carpets.

In these tests a portable floor was constructed from asbes.tos board and

fitted into the test section. Correspondingly, the ceiling was raised

the thickness of this portable floor. Sixty grams per ft^ of either

latex or insulating adhesive was used to attach the sample to the portable

floor. This amount of adhesive satisfactorily holds the carpet in place

and is typical of commercial applications.

4. INSTRUMENTATION

In order to understand the phenomena of floor covering flammability

adequate instrumentation to make measurements , was necessary. These

resulting data then must be assembled and processed in some manner which

is fast and economical. It was decided to use available electronic

instrumentation, where feasible, that would allow quick data reduction

utilizing the central computing facilities at NBS.

4.1 Data Collection

Data are collected by a digital data acquisition system designed and

built at NBS. It consists of a digital clock, a reed relay scanner, a high speed analog to digital convertor, a system controller, and a high

speed paper tape perforator. The system accepts up to twenty analog

signals and scans them sequentially at a rate of 16 channels per second

when activated by the digital clock. Figure 8 shows the system setup.

4.2 Data Reduction

The data are processed with SPEED [7], a problem-oriented language

for computer use written in FORTRAN IV. The program was developed at

NBS for general purpose data processing. The program converts instrument

readings to engineering units and displays them in tabular and graphic

form. Figures 9 and 10 are sample data printouts.

Figure 11 is a flow chart' of d^ta from sensor to completion of the

data reduction program.-

15

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4.3 Sensors

Temperature gradients are measured during the test program with #24

gauge Type K chromel-alumel thermocouples placed at strategic locations

throughout the model corridor (figure 12) . The 20-channel capacity limit

of the data system makes necessary the many schemes of instrumentation

noted.

Thermal flux measurements are nade with three types of instruments.

The first type is an incident radiant heat flux transducer (radiometer)

.

Two of these were placed on the floor of the model at 18 in and 36 in

along the center line. They were chosen with a viewing angle of 90** and

with a sapphire window. They are water cooled and air purged, and have

a maximum rating of 5 BTU/ft^-sec. While much useful information was

acquired, it must be noted that some error does exist with these sensors

due to the opaqueness of the sapphire window beyond a wavelength of 5 urn and alsc- due to heating of the sapphire window from nearby flames.

During CFT 183-196, measurements were made of the heat losses through

the walls and out of the exit duct of the model corridor by using a second

type of heat flux meter which measures transmitted heat flow. It consists

of an aluminum oxide plate and a thermopile which measures temperature

difference across the thickness of the plate.

The sensors were calibrated at several temperature levels, however

calibration problems exist at high temperatures due to the lack of a good

high temperature standard. Locations of these heat flux meters can be seen in figure 12c. These tests require modifications of the test section

to make neat loss measurements which would enable an overall heat balance

analysis to be done. Transported energy flow rate was measured bv using

an orifice plate with an opening of 29 in^ placed at the exit end of the

test section, and several baffles placed in front of this plate to get

thorough mixing of the air. Because of these system modifications the

bypass portion of the test section was blocked for these tests at the

inlet end. This was done to insure uniform and adequate air flow at the

entrance to the actual test section.

The third type of flux measurement was made by a total incident heat

flux meter placed across the floor center line at 25 in. This experimental

sensor consisted of length of metal tubing through which a metered flow

of water was passed. A differental thermocouple measured water temperature

rise. Tv:?o problems were encountered with this sensor. There was a time

lag, and boiling of the water at high heat fluxes. This heat flux meter

was used on CFT 293-294.

During CFT 190-191 oxygen concentration was monitored with an oxygen

cell installed at the exit end of the burning chamber, and recorded on

a strip cnart recorder. It was observed that the cell was temperature

sensitive and showed a definite time lag.

20
INSTRUMENT LOCATIONS

CARPET FLAMMABILITY TESTS 12 THRU No.31

TESTS 32 THRU No. 46

[— 18" — 2-

4' 8' O THERMOCOUPLE LOCATIONS ^ RADIOMETER LOCATIONS

Figure 12A. Instrument locations.

21
INSTRUMENT LOCATIONS

CARPET FLAMMABILITY TESTS 61 THRU No.69

TESTS 70 THRU 105

.17

mill inniinA

14

> CARPCr

19miniii

(unwittMiuxraa PAO

10

9

16 . ,2»/

18

''ill.

TESTS 106 a 107

J7

3'

N0.2 - NO. 22 WIRE 8- "26 M » 9 - • 24 " "le- " 2^1 (SILVER SHIELD)

N0.4 - Ml. 52 WIRE

II 1 9 - " 2 4- ••

r///i//////f//m// CARPET w

nmtmm pad

,,1111111) lll^lliilllllttlill

18'

2'

irt^ 4' 8

O THERMOCOUPLE LOCATIONS

^ RADIOMETER LOCATIONS

Figure 12B. Instrument locations.

22
INSTRUMENT LOCATIONS

CARPET FLAMMABILITY TESTS 108 THRU No.192

^3

04

0 8 D9

DI2 nmmiiii,

14

\lllU CARPET lll'^-'ll'llll

19

10 ^7

IS

,111111111 PAD

TESTS 193 THRU No. 211

TESTS 212 THRU No.285

8' O THERMOCOUPLE LOCATIONS

* RADIOMETER LOCATIONS

Figure 12C. Instrument locations.

23
INSTRUMENT LOCATIONS

CARPET FLAMMABILITY TESTS 286 THRU NO. 329

\

IS

,17

//////

i12

93

14

f

ilO 19 < J

.9 .3 Z

11nilmil.

I

////

TESTS 330 THRU No. 364

O THERMOCOUPLE LOCATIONS ^ RADIOMETER LOCATIONS

Figure 12D. Instriiment locations.

24
4.4 Other Measnrenents

Weight loss measurements of materials were used to determine heat

release rates. This was accomplished by cutting a three inch square

sample from the floor covering material, and weighing it before and after

burning. This procedure was followed generally throughout the test

program.

More thorough weight loss measurements were made during CFT 131 and

137. A grid of 3 in squares was dra^^m 18 in wide beginning at the burner

and extending 24 in down the model corridor. Forty-eight samples each

were taken from the carpet and underlayment . The weight loss calculations

were made based on weight before and after for each of the 3 in square

sa:nples

Flame spread was observed visually during the tests and elapsed time

recorded every 3 in burned. Carpet Flammability Tests 184-185 were run

to get some idea of area burned in relation to elapsed time. Once again

a grid was drawn on the sample and visual observation of the burned area

was made every 30 seconds and recorded graphically.

For each test air temperature and relative humidity measurements

were taken in the carpet storage area and at the air intake for the model

corridor with sling psychrometer . These data were recorded on the data

sheet as shown in figure 13. Outside temperature, relative humidity, air

velocity and direction, and barometric pressure readings were obtained

from the local weather information service before each test. This also

is recorded on the data sheet in figure 13.

5. TESTING PROCEDURE

Before beginning tests each day it was found necessary to pre-heat

the test section and then allow it to return to room temperature. This

need arose because the room in which the facility was located was not air

conditioned and tests showed that the construction material (asbestos

board) was affected by moisture. This preheating might not be necessary

if the test facility was located in an area with good temperature and

humidity control.

Materials to be tested (carpet, underlay, etc.) are cut 1/4 in

narrower than the inside width of the test section and to the desired

length (up to a maximum of 94 in) . They vjere allowed to condition in

the test room for at least 24 hours. It would be desirable if this

conditioning were done under controlled temperature and humidity.

A run sheet is prepared for each test on which test conditions are recorded. A copy of this form is attached as figure 13.

25
CARIET FL/LMMBILTTY TEST NO.

TEST PARAMETERS

Carpet Tested: 3co>Zoz Active % /Lq

Underlay:

Model Dmensions:

Carpet Dinensions:

Air Flow: tOO

2^

Z

\4"

2 •(l)

Gas Input: Sop

Intake Air: Cfj °

F, Carpet Conditioning:

Outside Conditions:

ft/rain ( t-io holes 1.'? "

) BTU/min ( setting)

Of, _^3L^RH

4o °F, __S__$6RH

Date: 2^5

pressure

Ignition Time: {O'. 32«'.o«^

RESPONSES

Plame ^read

3" V.o^ 27" 51" 75"

6" •••23 30" 78"

9" :--45 33" 57" 81"

12" r.;Z3 36" 60" 81;" 1^" 3-.-.oy 39" 63" 87"

18" v. 31 U2" 66" 90"

21" 69" 93"

2ii" U8" 72"

Flame front self Extinguished:

Reignited:

final extinguishment:

Total Ignition Time: I 2^ niin Maximum flame spread:

length:

All Flame Out:

COMMENTS

VJidth:

I2L min

^min

rain

rain

Signed jj^

Figure 13. Sample data sheet.
Prior to the start of each test the movable wall and ceiling are positioned to provide the desired cross-sectional dimensions of the test

section. The proper number of holes in the orifice plate are opened so the desired air velocity can be obtained. The carpet assembly is placed

on the floor of the test section and vacuumed. The curbs, burner ignition

spark lead and instrumentation are positioned. The blower is then started

and the inlet vanes adjusted to provide the specified air velocity as indicated by the manometer pressure. With the blower running, the stopcock

on the gas line is opened and the valve adjusted to provide the proper gas

flow as indicated by the flowmeter.

The data acquisition system is activated before starting each test

and the first data scan is made 10 seconds before ignition. This first scan records ambient conditions in the system. A data scan is then

automatically recorded every 10 seconds during the entire run (figures 9

and 10).

To initiate a test the gas is turned on and a spark generated by an ignition transformer ignites the burner (at time 0::00). During the test

the position of the leading flame front (of the burning carpet) is observed

visually through the glass windows in the door, and the position of the

flame is lined up with distance markers placed every 3 in along the back

wall as measured from the burner. As the flame front passes these markers,

the time (in minutes and seconds from ignition) is recorded on the run

sheet. With these data the flame spread can be plotted as illustrated on figure 14.

In the experimental program it was found that, under most sets of

experimental parameters, one of two modes of flame spread would occur. Once the flame front moved beyond the immediate influence of the burner

flame either a decelerating flame front leading to self extinguishment

or a very slow burning rate, or a rapidly accelerating flame front leading

to total involvement of the sample, would occur. This latter phenomenon

has been termed "flameover". It is, therefore, necessary to record

sufficient information on the run sheet to identify the type of flame

spread that occurs. These data includes times at which extinguishment,

any subsequent re-ignition of the flame front, or flameover occur. The

time listed for flameover is that time when the flame front has reached

94 in. Additionally, any unusual burning conditions, such as edgeburning or carpet buckling, is noted.

The time selected for most tests was 12 minutes with the burner on plus an additional 12 minutes with the burner off. Flame spread is

recorded and data are acquired for this 24 minute period. Within the

first 12 minute period should flameover occur, or if the flame front

extinguishes the test is terminated 2 minutes after the burner is turned

off.

If a facility of this type is used for test purposes without a need

to record temperature or heat flux data, the test could be stopped when

flameover occurs or when it is certain that no further flame spread would

occur.

27
o

CO — cy o

O

1

I

UJ

cx: <

Bm vj^ c^csj

'^o Qfc! X «

' 3 X > <i o

2E K>

^ ^

it,,

CK OO O O

o

28
Upon completion of a test, the blower is stopped and the test section

door is opened so that any flaming or smoldering can be extinguished.

Exact distance of flame spread is measured and recorded on the run sheet.

To approximate the total area burned ^ the maximum burnt width is also

recorded. Following many of these tests 5 photographs of the samples were

made (figure 15).

The final step in each test is to remove the burned sample, vacuum

the test section, and allow the walls ^ ceiling, and floor to return to room temperature before another test is begun. Because of the relatively

thin construction material (3/8 in asbestos board), this cooling can usually be accomplished in not more than 30 to 45 minutes, even following

a severe burn or flameover. Floor and ceiling surface thermocouples have

been used to check the test section temperature before proceeding with

the next test.

6. TEST REPEATABILITY

Since the model corridor was designed to be an experimental facility

and not a test apparatus, a statistical plan was not developed to determine

the repeatability or reproducibility of such a facility. However, as part

of the experimental program many tests were performed in replicate. A

brief review of these data should be useful in indicating the reliability

of results. Additionally, some of the replicate tests emphasize a few

variables where better control was necessary. Table 4 summarizes the

results of some of the tests that were replicated.

In series A and B, runs 62 and 63 were made immediately following

the installation of new construction material (movable wall and ceiling)

in the test section. In both cases flameover did not occur, whereas in

earlier tests with the same carpet assembly and test condition flameover

had resulted. The test section was then "conditioned" by heating for

about one hour, cooled, and then runs 64 and 68 gave results similar to

past experience. In series B, run 106 was made following a period of

cold, damp weather in which no tests were conducted for twelve days.

After preheating and cooling the system^ run 107 gave the result anticipated. A similar experience resulted in run 130 which was made early on

a cold, damp morning. Flameover did occur but required a longer time

than in previous tests. Runs 65 and 66 were conducted to determine the

effect of intake air temperature. Outside air was drawn directly into

the system on a cold (45°F) day. In both tests flameover did occur but

after longer time than had previously been experienced. These results

indicate the need to control both the condition of the test section and

the temperature (and relative humidity) of the intake air. The additional

data shown on table 4 indicate quite good repeatability. Flame spread

curves for Series A are plotted on figure 16.

Another example of the reliability of the test method was seen through

the experimental program. With any carpet assembly it was found that as the test conditions were increased in severity, an increasing flame spread

29

I

TABLE h

REPEATABILITY DATA

Series Carpet Test Conditions* Run No. Result^

A N-5/U 2h X 11, 500, 100 hi 8:: 50

63 35"

6h 10::07

65 ll+::30

66 1^::30

130 18:: 06

B A-4/U 2l+ X 11, 500, 100 h9 5:.-28

62 22"

68 U::25

106 2l|"

lOT 5::2U

129 6:: 50

C W-l/U 2h X 11, 500, 100 51 8"

139 10"

D A-h/]J 2h X ik, 750, 100 82 5::hO

126 5::08

E A-3/U 2l+ X IT, 500, 100 92 5 : : 06

96 11:: 57

F 0-k 2l+ X 11, 500, 100 201 31"

202 29"

G N-5/U -21+ X 11, 750, 150 301 29"

329 31"

Note: * Test conditions shown are model dimensions (W x H) in

inches, heat input in BTU/min. , and air velocity in

ft . /min.

** Results are shown in inches turned if flameover did

not occur or in time (min:: sec) to flameover.

31
0 4 8 12 16 20

BURN TIME (minutes)

Figure 16. Series A flame spread curves.

32
distance would result up to the point at which flameover occurred. If

test conditions were further increased in severity, the time to flameover

decreased. An example of this is shown on table 5. In this experiment

the severity of test conditions was increased both by increasing heat

input and by lowering ceiling height.

These results indicate that test conditions must be carefully

controlled to produce reliable data. With good control repeatable results

have been obtained.

7. CONCLUSIONS

The design of the model corridor proved that good control of the

numerous variables encountered in the study of the flammability of floor

coverings could produce repeatable test results. The air handling system

permitted a wide range of velocities, while providing a uniform, stable

flow during a test. The 3/8 in asbestos board construction was durable,

yet thin enough to allow rapid cooling between tests.

The operating proceedure that was developed provided accurate and

repeatable results during the experimental program. The results of this

program are compiled in a separate report [6]. A complete file of all

experimental data obtained during the program is being maintained at the

National Bureau of Standards.

33
TABLE 5

EFFECT OF CEILING HEIGHT & HEAT INPUT

Ceiling Height

11" lU" 17" 23"

300 23"

Uoo Cl7: :08) 13"

•He 500 (11: :02) (19::03) 28" 25"

'

"DITIT

T)

600 (9: :^0) 19"

-P

•H 750 (6::32) 90"

Inpi 1000 (7::2M

Heat 1250

1500

1750

2000

38"

38"

UU"

65"

Carpet - N-5/U

Air Flow 100 ft/min

Model Width - 2h''

34
8. REFERENCES

1. "Carpets and Rugs" (Pill Test) Standard for the Surface Flammability

of Carpets and Rugs, DOC FF 1-70, Federal Register, Vol. 35, No. 74,

April 16, 1970, p. 6211.

2. "Standard Method of Test for Burning Characteristics of Building

Materials", ASTM E84-68, American Society for Testing and Materials,

Philadelphia, Pennsylvania (1968).

3. "Standard Method of Test for Flame-Propagation Classification of

Flooring and Floor-Covering Materials", Subject 992, Underwriters'

Laboratories, Inc., February, 1971.

4. "Surface Flammability of Materials Using a Radiant Heat Source",

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

Philadelphia, Pennsylvania (1968).

5. Memorandum from Z. Zabawsky to ASTM Subcommittee IV Task Group on Floor Covering, "Armstrong Cork Co. Flooring Radiant Panel",

May 17, 1971.

6. W. Denyes and J. Quintiere, "Experimental and Analytical Studies

of Floor Covering Flammability With a Model Corridor", NBSIR 73-199,

May 1973.

7. J. M. Smith, "Automatic Data Evaluation, Manipulation, Display,

and Plotting with SPEED", Computer Graphics , Vol. 4, No. 2, Fall

1970.

35

FORM NBS-114A (1-71) U.S. DEPT. OF COMM. 1. PU B LIC .M ION OR REPORT NO. 2. Gov't Accession

B.BLIOGRAPHiC DATA ^^^^^

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

A Model Corridor for the Study of the Flairanabllity of

Floor Coverings

5. Publication Date

6. Performing Organization Code

7. AUTHOR(S)

Wells Denyes and James W. Raines

8. Performing Organization

9. PERFORMING ORGANIZATION NANiE AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 490 0S72

11. Contract/Grant No.

12. Sponsoring Organization Nam^ and Address Man Made Fiber Producers Association, Inc.

iloU Seventeenth bt. N.W., Washington, D.C. zUUjd and

National Bureau of Standards

Washington, D.C. 20234

13. Type of Report & Period Covered

r inai

14, Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

6. 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 program was carried out to develop a laboratory test method that

would measure the flame propagation characteristics of floor covering

materials. A facility was designed which included a tloor mounted specimen

in a rectangular cross-sectional duct having a torced supply of air and a gas burner Ignition source. The effects of variations in duct size, ignition

source, and air flow were studied. Factors influencing repeatable test results were explored. Flame spread was measured by an observer and temperature and heat

flux measurements were recorded on an electronic digital data acquisition system.

7. KEY WORDS (Alphabetical order, separated by semicolons)

Air tlow, energy input; fiameover; flame spread; floor covering f lammability;

model corridor; test repeatability.

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