This report has been prepared

for information and record

purposes and is not to be referenced

in any publication.

NATIONAL BUREAU OF STANDARDS REPORT

V36hA NEW TEST METHOD

For

EVALUATING FLAMMABILITY

Of

INTERIOR FINISHES

By

A. Fo Robertson

D. Gross

J. L o f t u s

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Rureau of Standards is suggested in the following listing

of the divisions and sections engaged in technical work. In general, each section is engaged in

specialized research, development, and engineering in the field indicated by its title. A brief

description of the activities, and of the resultant reports and publications, appears on the inside

of the back cover of this report.

Electricity and Electronics. Resistance and Reactance. Electron Tubes. Electrical Instru- ments. Magnetic Measurements. Process Technology. Engineering Electronics. Electronic

Instrumentation. Electrochemistry.

Optics and Metrology. Photometry and Colorimetry. Optical Instruments. Photographic

Technology. Length. Engineering Metrology.

Heat and Power. Temperature Measurements. Thermodynamics. Cryogenic Physics.

Engines and Lubrication. Engine Fuels.

Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid

State Physics. Electron Physics. Atomic Physics. Nuclear Physics. Radioactivity. X-rays. Betatron. Nucleonic Instrumentation. Radiological Equipment. AEC Radiation Instruments. Chemistry. Organic Coatings. Surface Chemistry. Organic Chemistry. Analytical Chemistry.

Inorganic Chemistry. Electrodeposition. Gas Chemistry. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances.

Mechanics. Sound. Mechanical Instruments. Fluid Mechanics. Engineering Mechanics.

Mass and Scale. Capacity, Density, and Fluid Meters. Combustion Controls.

Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifications. Polymer Structure. Organic Plastics. Dental Research.

Metallurgy, Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion.

Mineral Products. Porcelain and Pottery. Glass. Refractories. Enameled Metals. Concreting Materials. Constitution and Microstructure.

Building Technology. Structural Engineering. Fire Protection. Heating and Air Conditioning. Floor, Roof, and Wall Coverings. Codes and Specifications.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics.

Data Processing Systems. Components and Techniques. Digital Circuitry. Digital Systems.

Analogue Systems.

Cryogenic Engineering. Cryogenic Equipment. Cryogenic Processes. Properties of Materials.

Gas Liquefaction.

Radio Propagation Physics. Upper Atmosphere Research. Ionospheric Research. Regular

Propagation Services.

Radio Propagation Engineering. Frequency Utilization Research. Tropospheric Propagation

Research.

Radio Standards. High Frequency Standards. Microwave Standards. • Office of Basic Instrumentation • Office of Weights and Measures
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT

1002 - 10-1029 October 12, 1955

NBS REPORT

^364-

A NEW TEST METHOD

For

EVALUATING FLAMMABILITY

Of

INTERIOR FINISHES

By

Ao Fo Robertson

Do Gross

J. Loftus

NBS

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication,

unless permisslor 25,D,C. Suchp

cal ly prepared It

Approved for public release by the

or ln pa,t| IS prohlbi,ed

Standards, Washington Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

report has been speclfireport for Its own use,
'
A NEW TEST METHOD FOR EVALUATING

FLAMMABILITY OF INTERIOR FINISHES

ABSTRACT

A new test method is described which permits use of

relatively inexpensive and compact equipment for evaluation of the flame spread behavior of interior building

finish materials by the use of specimens 6 by 18 in, in

size. Flame spread index data are presented for a number of

finish materials o Methods of construction and calibration

of the apparatus are described in sufficient detail to

permit duplication of the facility by others.

1. INTRODUCTION

The rate with which an accidental fire will develop into

a full fledged fire involving a whole building depends primarily upon three major factors. In the absence of fire detection and fighting facilities, these are: a) the flame spread

properties of the interior finish, b) the extent of compartmentation and degree of ventilation, c) the fuel contributed

by and the manner cf distribution of the building contents. It

is only the first two of these over which the builder and

approving agency has some control. In spite of a number of

full-scale burn-out tests, references 1, 2, 3? the complexity

of the problem has prevented more than a rather crude appreciation of the relative importance of the factors governing growth

and spread cf fires and the most practical methods of their

control. Because of this, rather arbitrary methods have been

adopted for evaluation of flame spread properties of finish

materials and for specification of the degree of compartmentation desirable. The present discussion will be confined to

methods of evaluating the flame spread properties of building

finish materials.
'
2 -

Test methods for evaluating this property have been developed and studied both at the National Bureau of Standards

and at other laboratories for many years. The Cocoanut Grove

fire in 1942, however, was largely responsible for the impetus in the adoption by insurance underwriters, of the

tunnel test, reference 4, as the standard fire hazard test

method used by their laboratory., The method developed appears

to classify many materials in an order which empirical experience has shown to be desirable <> The cost of the test

specimens however has delayed if not prevented its use by

private manufacturers, testing, and government laboratories - Numerous smaller test methods have been developed and used

by such groups o Examples of these include the flame resistance

test method described in Federal Specification SS-A-ll8b,

reference 5 ? the spread of flame test method of British

Standard BS 4-76, reference 6, and the inclined panel test

described in Federal Specification TTP-26a, reference 7°

The fibst of these was developed for evaluating certain

combustible properties of acoustical tile but has frequently

been proposed and used in the formulation of building codes

„

When used for this purpose it is a very severe test and classifies materials in only a qualitative fashion., The British

test method was developed during the war as a result of their

first hand experience with fire „ The method suffers however

in providing too mild a test as indicated by recent studies

made at the Fire Research Station, reference 8„ The third? intended for evaluation of paint finishes, also utilizes a' comparatively mild fire exposure of the specimen, and consequent

ly it has not generally been considered suitable for evaluation

of flame spread properties of materials

»

Because of these difficulties it appeared desirable to

attempt development of a new flame spread test method which

would involve use of only modest size specimens, be relatively compact and inexpensive to reproduce and use, and last

but not least would evaluate the flame spread behavior

of materials in a manner consistent with their observed performance during fires „ This paper presoi ts a description of

the test method developed together with test data on representative building materials., Particular effort has been made to

provide sufficient equipment design and calibration data to

permit others to reproduce the test facility.
-
- 3 -

2. PRIMARY CONSIDERATIONS

During the flaming combustion of solids the combustible

gases which sustain the flaming are released from the solid

as a result of heat received by the solid itself. This heat

may be supplied by some external source but in most cases

where flaming occurs, it is largely supported by radiation

from the flames and convection from the hot gases „ The rate

with which a flame can spread along the surface of a material

with combustible content is thus largely determined by the

rate with which its surface may be heated. The thermal properties and dimensions of the specimen as well as the size and

character of the flames produced are therefore of considerable

importance in determination of its flame spread behavior.

The wavering or turbulent characteristics of flames

from a burning solid obscure the progress of volatilization

of gases from the solid and consequently the spread of flame

on its surface. In the past, it has therefore been considered

desirable to use test specimens having at least one dimension

large compared both to the length of the flames and to the

fluctuation in flame length produced during burning. If,

however, a controlled external source rather than flame radiation

is used to supply heat to the non-flaming portion of the specimen,

more accurate observations of the progress of the flame front

are possible when using much smaller sizes of test specimens.

Under these conditions, the rate of spread of this flame front

does not include the heating effect that the flaming portion

would normallly contribute to the unignited portion. Some

method must therefore be devised for measurement of the heatin

power of the flames and incorporation of this with the rate of

spread of flame measurement.

The apparatus to be described makes use of a test arrangement similar to that suggested above. The specimen is oriented

in front of a radiant heat source in such a manner that ignition

takes place at the top of the specimen and the flame front

travels downward. Flames rise away from the unignited portions

of the specimen. Thermocouples placed in a stack above the

upper end of the specimen furnish the necessary indication of

the rate at which the flames would supply heat to unignited

material under normal burning conditions.
.

'
- h -

3o TEST EQUIPMENT

Figure 1 presents a view of the experimental apparatus

developed for performance of this radiant panel flame spread

test. The essential components shown here include the radiant panel with its associated air and gas supply system, the

specimen holder and framework for its support, the stack with

thermocouples ? the smoke sampling tube with its gas metering

system, and the radiation pyrometer * Not shown are a hand

potentiometer, a recording potentiometer and a decimal minute

timer. A brief description will be given of each of these

components

.

3.1 Radiation Panel

The radiant panel consisted of a cast iron frame enclosing porous refractory material the assembly being imported

from England.* The panel was mounted in a vertical plane.

It was fed from, the rear with a pre -mixed gas -air supply,

combustion of which was nearly completed within its pores.

After warm-up, the only visible flames from the panel surface

were less than 1/8 in. in length. The panel approaches its

equilibrium temperature of approximately l4-72°F (800°C) in

about one half hour after ignition. This particular panel

was 'selected as being the only one available at the time

which could operate at temperatures as high as 1]+72°F» It

is quite possible that other types of burners or even electri

cal heaters would prove equally satisfactory. Electrically

heated panels were not considered because of the power consumption which amounted to about 2h kw based on the total

heating value of the gas supplied for combustion.

Air was supplied to the panel by means of a small centri

fuga.l blower fitted with an air filter to prevent dust from

obstructing the panel pores. Gas was premixed with air in

a venturi mixer to which it was supplied at approximately

atmospheric pressure.

*The appendix includes a. list of components used and in cases

of special requirements or limited availability suggests a

possible source of supply. It is possible however that other

sources of supply while unknown to the writer do exist.

- 5 -

3-2 Specimen Holder

Figure 2 presents an assembly drawing of the specimen

holder used for support of the 6 by 18 in. specimens < It

comprised a simple device formed of sheet steelo Although

low carbon steel was used in the initial holders it would

probably be preferable to use a heat resisting chromium steel

in their fabricationo Figure 3 presents general arrangement

drawings of the radiant panel and support frame necessary for

proper positioning of the specimeno An attempt has been made

to show only those dimensions which should be maintained in

reproduction of the equipments The angle of the specimen and

its position with respect to the panel were found to be critical

and have been selected as a result of a series of tests

.

These drawings also show the position of the tip of the

pilot burner tube which was used to force ignition, when this

was possible, at the top of the specimens This burner consists

of a short length of 3/16 in. OD by 1/8 in. ID stainless steel

tubing the portion of which exposed to radiant energy from the

panel was protected by an outer porcelain tube 7mm OD by 7 mm

ID 0 It has been found necessary to replace this burner occasionally because of oxidation and residue deposits which collect on

Ito To cut down on the frequency of such replacement the pilot

has been arranged to swing out of position when not in use®

The pilot was fed with acetylene premixed with air

supplied from the radiant panel air supply blower . Use of

an aspirating type fitting might prove to be a more desirable

method of supplying the necessary air.

3-3 Stack and Thermocouples

Figure 3 shows the dimensions and position of the stack

with respect to the specimen and radiant panel. The location

of the eight thermocouple junctions are also shown. These

junctions were formed by fusing the end of a twisted pair

of Chromel and Alumel wires of No. 2kB&S gage. The junctions

were supported in position by means of porcelain insulators

as shown in figure k. The group of eight junctions were

connected in parallel, their output being recorded by an automatic potentiometer recorder.
.

$
- 6 -

3 A Smoke Sampling Device

The smoke sampling device consisted simply of a means for

support of a single layer of glass fiber filter paper at a

given position above the stacko An aspirator and rotameter

were used to maintain a constant air flow rate of ^0 ft/min

( 20*4cm/sec) at the face of the filter « The method of collecting and weighing the smoke deposit was used because of the

usual difficulties experienced with sampling techniques and

condensation problems experienced with optical methods of smoke

measurement

o

3.5 Associated equipment

A radiation pyrometer was used for standardization of the

thermal output of the panel. The electrical output of this

device was monitored by means of a portable hand balanced

potentiometer. An automatic recording potentiometer was used

for recording stack thermocouple temperature variations. The

instrument used had a range of 32 - 932°F (0-50Q°C)» A small

timer calibrated in minutes and decimal fractions to hundredths

was used for recording the time of occurrence of events during

the tests.

k. TEST PROCEDURE

The procedure which was developed for performance of the

flame spread test may be outlined as follows?

(a) Gas from, the radiant panel was ignited and the

unit allowed to heat for a one half hour period. At

the end of this time a check was made of the radiant

output by means of the radiation pyrometer placed in

such a manner as to view a central panel area of about

ten inches diameter. If necessary ? adjustment was

made in the rate of gas supply to maintain the radiant

output at that which would be obtained from a blackbody of the same dimensions operating at a temperature

of 1292°F (700°C). The radiating characteristics of

the panel used resulted in its operation at a surface

temperature of about l472°F (800°C).

(b) The recording potentiometer for measurement of

stack thermocouple temperature rise was turned on and

if necessary the thermocouples were cleaned by use of

a brush.

(c) . A new filter disk was placed in the smoke sampling

tube and the air flow rate adjusted.

- 7

-

(d) The pilot was ignited, adjusted to provide a flame two or three inches in length, and placed in

position in front of the radiant panelo

(e) A. 6xl8in 0 specimen previously conditioned to

equilibrium with an ambient of 75± 5°F and 50+ 5 percent

relative humidity was either (1) mounted in a cool

specimen holder in the conditioning room and brought

to the test equipment in a vapor barrier jacket, or

(2) wrapped in a vapor barrier jacket, brought to the

test equipment and quickly inserted in a cool specimen holder o In either case all but the thickest

specimens were backed with iin. thick asbestos millboard of 60 lb/ft3 density 0

(f) The smoke sampling tube was placed in position

above the stacko

(g) The specimen in the test holder was placed in

position on the radiant panel frame and the electrical

timer simultaneously started a The exposure of the

specimen took place as promptly as possible after

bringing it ot the test area» In most cases this was

accomplished within three minutes 0 In no case were

conditioned specimens allowed to stand in the test

room for more than five minutes prior to testo

(h) Observations were continuously made of the development and spread of flaming on the specimeno

Records were kept of the time of arrival of the flame

front at points 2, 3 5 6, 9* 12, 15 & 18 in° from the

upper edge of the specimen.o Notes were made of any

other specimen behavior characteristics which appeared

of interesto

(i) The test exposure was considered as completed

when either (1) the flame front had progressed the

full length of the specimen, or (2) the test exposure period of 15 minutes had elapsed „ The specimen holder was then removed from the supporting frame

and the specimen discarded,,

(j) Measurement was made of the increase in weight

of the smoke sampling filter paper disk and the

maximum temperature rise of the stack thermocouples

„

These data were recorded^
* .
- 8 -

(k) The flame spread index I s of individual samples

was calculated as the product of the flame spread

factor Fg and the heat evolution factor thus:

I = F Q s s Where

:

F = (1 + —— + i— HH —L + i + i— ) s t-3 t^-t

3

t 9~ t 6

t i2~t

9

t l5~ t i2

here: t^ -- t^j correspond to the times in

minutes from specimen exposure until arrival

of the flame front at a position of 3 ----- 15 in»

respectively along the length of the specimen.

here: A© is the observed maximum stack

thermocouple temperature rise in degrees

Fahrenheit over that observed with an asbestos

cement board specimen, and , a calibration

constant, is defined by the slope of the

calibration curve for the stack thermocouple

temperature versus heat input rate in units

of degrees F min./BTTJ,

5o CALIBRATION PROCEDURES

The calibration procedures used during development of

the test method were of two different types , First, certain

procedures were found to be necessary for standardization of

the test method to permit reproducibility of test results.

These will be designated as "standardization procedures".

Secondly, a series of tests were performed in an effort to

determine the sensitivity of the test method to small changes

in orientation or assembly of the test equipment. These

studies will be described under the title of "procedural

variations".

5,1 Standardization Procedures

The radiant output of the panel was monitored continuously between tests by means of the radiation pyrometer.

Adjustments in gas flow rate were frequently, though easily

made. As previously mentioned this radiant output rate was

maintained at that of a blackbody radiating at a temperature

of 1292°F (700°C),
,
- 9

The smoke sampling tube and associated connections were

checked periodically by use of an impermeable diaphragm in

place of the filter disko Any flow that could be measured

with the inlet thus blocked wasa sure indication of leakso

On several occasions leaks were detected by this means o Such

leaks are serious as the filter resistance to gas flow is

not negligible and leaks would therefore result in low recorded

smoke weight 0 Periodic checks were made of the temperature rise produced

by placement of an asbestos -cement board specimen in position

while both the radiant panel and pilot burner were in operation o

No test method was devised to check for objectional

deposits of combustion products on the thermocouples other

than periodic inspection For most ceilulosic materials

tested it was found that inspection and brush cleaning of

the thermocouples was desirable at least once every two weeks

of operation for eight hours a day Q When testing hardboard

specimens as well as plastics the smoke production rate

required much more frequent attention to this detail

»

Calibration of the stack thermocouples was only infrequently done o This calibration was performed by means

of a diffusion flame from, a multi ported burner 0 This burner

(ten Noo 50 drill holes spaced 5/8 in 0 on centers in a 1/4 in.

standard pipe) was placed in a horizontal position one inch

below the upper edge of an asbestos-cement board specimen

during normal panel operation From observations of the

maximum stack thermocouple temperature rise as a function of

heat supply rate to the test burner the value of/5 in the

flame spread index formula was measured » For the equipment

used here/? was found to be equal to 0 = 90 degrees F min/BTUi

Figure 6 presents a plot of data obtained, on the equipment

usedo There was no indication .that this measurement required frequent checking

One other calibration was performed to provide an

indication of the heat input rates at the specimen surface <> This involved radiometer measurements at various positions

along the specimen lengtho The measurement was made by the

use of a small copper disk radiometer fitted in one opening

at a time of a series of apertures on an asbestos millboard specimeno The radiant panel was in operation but the

pilot was not burning during these measurements » Figure 7

presents a calibration curve obtained in this way 0 It

should be noted that the energy flux measured and indicated

here was the sum of both the radiant flux and that arising

from convection effects

o

- 10 -

5°2 Procedural Variations

A number of tests were performed for the purpose of determining the extent to which design features of the equipment were critical

The position of the specimen relative to the radiating

face of the panel was found to be criticalo This position

determines the energy flux at the specimen surface. While

measurements were not made on the effects of changes in

positioning, it appears likely that the dimensions indicated

in figure 3 should be maintained to a tolerance of less

than 1/8 in.

The technique used for calibration of stack thermocouples

was selected to reduce the effects of slight differences in

design or positioning of the parts of the apparatus. Figure 8

presents data on the effect of stack position on thermocouple

temperature rise for both a typical specimen (fiberboard No. 8)

and the calibration burner. It is evident that the observed

thermocouple termperature rise does not require exact maintainance of the selected two inch spacing. Although this behavior

of fiberboard is typical of all materials tested the same insensitivity is not observed when the calibration burner is

used as a heat source. This probably results from differences

which exist in the manner of heat release in the two cases.

Changes in vertical position of the stack and their effect on

thermocouple temperature rise measured during test of specimens

were not investigated. It is expected however that the data

would be quite similar to that shown in figure 8 for the calibration burner.

The importance of position of the pilot flame was studied.

It was shown that the size of this flame and its position

with respect to the face of the specimen were not critical

as long as the flame remained in contact or at most not more

than one half inch from the surface of the specimen.

Conditioning of the specimen prior to test was important

as evidence by data obtained for fiberboard specimen No. 8.

Flame spread index values of 353 ? 236 and 156 were measured

for specimens conditioned to have 1, 7 and 12 percent moisture

respectively. These moisture equilibrium contents correspond

to widely different ambient relative humidity conditions.

Because of this and the shape of the moisture equilibrium versus

relative humidity curve for materials such as these, the effect

of small changes from the standard conditioning temperature and

humidity would not be expected to result in flame spread index

changes proportional to those indicated above.

11

A study was made on the effect of variations in draft

conditions on the measured flame spread indexo Most of the

test results reported in this paper were obtained while the

furnace was operating under a 2tyb-fthood the exhaust

blower _ of which was in operation, The air flow rate was over

600 ft3,/min through this hood 0 Table I presents average flame

spread index data from tests of two specimens of each of four

different materials , These tests were performed both with and

without operation of the exhaust fan, It will be observed

that when proper calibration has been made and used in flame

spread index calculation, the test results are very similar

for the two test conditions » Even when the results are not

corrected for change of thermocouple calibration the flame

spread index is changed by a factor of only about ten percent

,

The apparent contradiction to this generalization, presented by the data for specimen 21 Is believed to have been

caused by nonuniformity of the specimens and the limited

number of samples tested.

6o DISCUSSION

The test method has been used to evaluate the flame spread

properties of more than 60 different materials. Data on the

behavior of 29 of these are included in table II, The materials are listed in order of decreasing flame spread index.

The constant in the flame spread index relation was arbitrarily chosen to yield a value of approximately 100 for red oak.

Included in this table are data on all materials thus far

studied for which Underwriter tunnel test data were available

as a result of tests performed on samples from the same

material batch. The flame front progression along the surfaces

of various specimens is shown in Figure 9° The numbers on the

curves correspond to specimens described in table II,

Brief study of the data presented indicates that the

method selected for calculation of the flame spread index

results in a numerical grading of specimens which is in

general accord with experience. Furthermore, for flame spread

index data above about seven and with the exception of data

for plastic materials, there appears to be a fair degree of

correlation between the classification of materials by both

the radiant panel and tunnel test methods, figure 10, The

flame spread index values resulting from tests of the three

plastic materials were only about one half the classification

figures assigned on the basis of tunnel tests. Specimen 32

(plastic A) did not exhibit sustained flaming and only periodic flashes were observed in the gases leaving the specimen.

12

The plastic samples tested had aged under normal ambient con

ditions for a period of 3 to Id- months subsequent to the

performance of tests at Underwriters’ Laboratories. A

num.ber of the materials were tested by the horizontal panel

test described in Federal Specification SS-A-ll8b with the

results shown 0 It is evident that this method of test does

not measure the same surface flame spread property as evaluated by the radiant panel or tunnel test methods.

Experimental results of tests by the British Spread of

Flame test are not available on the materials in table II,

However, reference 8 presents the results of a study of

flash-over times observed during a series of tests with

model rooms which were finished with a wide variety of

materials some of them apparently similar to those tested

here. These latter have been listed in ta.ble II, It will

be observed that the order in which the materials are classified Is similar to that achieved with the radiant panel

test method. The model test method however appears to show

little difference in unfinished fiberboards whereas the

method of interpretation of the radiant panel and tunnel

results shows flame spread indices varying from 121 to 338.

The flaming behavior of the specimens might be selected

as an Indication of low, intermediate and high flame spread

characteristic o Thus specimens with a flame spread index

of less than four rarely exhibited sustained surface flaming

In the index range of 4 to l4Q sustained flaming usually

occurred only over a portion of the specimen. For flame

spread Indices above 140 flaming occurred over the full

specimen length during the 15 min test period.

The flame spread characteristics evaluated are only

those of the exposed surface of the specimen. Evidence of

this Is provided by specimens 8, 13, 9, 12, 11, 14- and 15

which all incorpora.te essentially the same in. fiber board

backing and yet with the varying types of surface treatment

exhibit flame spread index values ranging from 244- down to

1.2. This should provide ample evidence that consideration

must be given to the maintenance of an unbroken protective

surface on the material when used as finish material. In

cases where materials such as the one in question are used

for application directly to studs or over other enclosed

open spaces it appears highly desirable that both surfaces

be treated in the same fashion. In cases such as this,

Underwriters' Laboratories handles the problem by specifying

that the classification assigned is only applicable when

the finish is applied over a solid backing.

- 13

Some appreciation of the reproducibility of the test

method may be derived from the data presented in table III,

Here, s, the coefficient of variation (the standard deviation

expressed as a percentage of the mean value of the flame

spread index) is shown for four different materials 0 The

value of s has been computed from the individual values of

the flame spread index for the replicate tests performed.

It will be noticed that s for specimen Ko= 8 is very nearly

of the same magnitude for a series of tests performed on

a single day as compared to the value for tests run over a period of time, in this case 120 days. Thus the major portion of the variability of test data appears to be a result

of variations , either between specimens, or in the test

method itself within a single day= The nearly constant

size of the coefficient of variation for the fiber board

specimens No= 8, 23, and 28 provides an indication of its

relative independence of flame spread index for such

materials over the range of 121 to 278, The value of

s = 18, 5 percent for red oak specimens which were selected

to cover a range of densities appears to indicate the increase

in variability of the samples themselves.

The data shown for both calibration burner and fiber

board specimen in figure 8 make it quite clear that the

calibration method used should not be considered as providing

an absolute calibration of heat output rates of materials.

The refinements necessary to achieve this objective were

considered imppropriate for the application intended.

Smoke measurements are also reported in table III,

These are reported as milligrams of smoke deposit for the

volume flow rate maintained during the period of test. The

results are also presented on a relative basis using a value

of 100 for red oak which is the standard used by Underwriters 1 Laboratories, There appears to be a general correlation

although big differences are observed in several instances.

For materials exhibiting low flame index data the radiant

panel test method appears to result in higher observed smoke

release rates than result with use of the tunnel test method.

The test method described appears to present a simple

reproducible method of measuring the flame spread behavior

of building finish materials. The method of presentation of

test results was arbitrairly selected to yield classification

numbers somewhat similar to those reported by Underwriters 1 Laboratories on the basis of tunnel tests. Because of the

lack of quantitative data on, and the intangible nature of,

the flammable "hazard" of materials, it is not at present

possible to define the exact relation which exists between

flame spread index and the actual hazard of the material.

CONCLUSIONS

The following conclusions seem justified on the basis

f the work reported;

lo A new flame spread test method has been devised

for evaluation of the flammability characteristics

of interior finish materials

.

2o The new test method involves the use of comparatively

inexpensive and compact test equipment and requires test

specimens of but 6 by 18 in„ size.

3o A method for expression of test results has been

devised which appears to classify materials in an order

similar to that indicated as desirable from experience

with such finish materials

»

4o With the exception of data on a few materials there

appears to be a general correlation between the flame

spread results as obtained by the radiant panel and

tunnel test method over the flame spread index range

of 10 to 280o

- 15 -

APPENDIX

List of components used with a possible source of supply

for those of special requirements or limited availability

.

lo Radiant panel -- 12 in c by 18 in. type 1 surface combustor, manufactured by Radiant Heating Ltd., Barnsbury

Park, London N„l, England

„

2. Radiation pyrometer -- Miniature Radiamatic, Series 939A*+,

with special extension tube, manufactured bv MinneapolisHoneywell Regulator Company, Philadelphia M+, Pennsylvania.

3° Glass fiber paper -- Type 1106BH All-Glass Filter Media,

distributed by Mine Safety Appliances Co. , 201 No Braddock

Ave. , Pittsburgh 8, Pennsylvaniao

4- o Potentiometer recorder -- Range: 0 to 1000°Fo

5° Portable potentiometer -- Range: 0 to 5mv (corresponding

to temperature range: 0 to 1900°F with radiation pyrometer

listed above )

o

6o Flowmeter -- Capacity: 7000 cc air/min 0
—
- 16 -

REFERENCES

lo "Tests of The Severity of Building Fires", S. H. Ingberg,

Quarterly of the National Fire Protection Association, V22,

Nl, pp 43-61, July 1928.

2. "Fires in Houses", Anon., Fire Research, 1950 5 DSIR,

HUSO , London 1951

°

3° "Experimental Dwelling Room Fires", H. D. Bruce, United

States Department of Agriculture, Forest Service, Forest

Products Laboratory, Report No. D194l, June 1953=

4. "Fire Hazard Classification of Building Materials", A. J.

Steiner, Bulletin of Research, No. 32, Sept. 1944, Underwriters' Laboratories, Chicago.

5. Federal Specification, Acoustical Units; Prefabricated,

SS-A-ll8b, August 1954, U. So Government Printing Office,

6. "Fire Tests on Building Materials and Structures",

British Standard, No. BS 476, London 1953=

7° Federal Specification, Paint Interior White and Tints,

Fire Retardant, TT-P-26a, 13 January 1954, U. S. Government

Printing Office.

8. "Fire Hazard of Internal Linings", D„ Hird and C, F.

Fischl, National Building Studies, Special Report No. 22,

DSIR, HMSO , London 1954.

TABLE I

EFFECT OF EXHAUST DRAFT CONDITION

On

FLAME SPREAD INDEX RESULTS

Specimen

Noc

Material

ST*

Flame Spread Index

Fan On Fan Off

Corrected UncorrectedT

28 Fiberboard "A" 278 281 2 56

23 Hardboard Common "M" 114 116 105

21 Fiberboard "C" 61* 85 77

26 Gypsum Board "G" 4 o 7 * 4o 6 4.2

* * Average flame spread index for two specimens „ All tests run

on same day.

f Flame spread index based on calibration data for stack thermocouples with fan on o

* Differences between test results and data shown in Table II

result from limited number of samples tested and variations

between samples.


TABLE II RADIANT PANEL FLAME SPREAD DATA

No*

Material Property Flame Spread Data

Material Nominal

Thickness

Bulk

Density

Mo is - ture

No . of

Tests

Flame

Spread

Index

I s

Coeff * of

Variation

s

17

in * lb/ft3 % %

FbdoPerf cTile

,

Finish Removed 1/2 15-7 b*4 b 336 14*7

28 Fbd * "A” (FPL)' 1/2 20*0 8*0 6 278“ 5*1 “8" Fbd* "J" Unfinished 1/2 18*0 7*0 9 236 5*0

30 Plywood Unfinished

Exterior Fir lA 42.3 6*8 4 143 32.2

18 Hardboard Common "H" 7/32 59.8 3.8 b 136 12*4

23 Hardboard Common "M"

(FPL) 1/4 63 0 5 3*8 6 121 6 * 9

16 Fbd* Perf oTile 1/2 16*7 5* 8 5 116 13.6

13 Fbdo"J" + Paint A

250 ft 2 /Gal 1/2 18*3 6*5 5 107 A* 0

24 Red Oak (FPL) 3A 40*0 6 * 5 5 99 10*9

21 Fbd "C" (FPL) 1/2 19o7 6 * 0 b

”94“ 18.3

9 Fbd "J" Factory Finish 1/2 20*2 6* 6 “S3” 15.9

12 Fbd "J" + Paint B

250 ft 2 /Gal 1/2 17*0 6*2 5 59 17*2

34 Plastic "C" 1/8 81. b b b6 8*4

11 Fbd "J"+ Paint P

125 f

t

2 /Gal 1/2 17* 8 6*9 5 27 26.0

33 Plastic "B" 1/8 98*0 5 30 19* b

2b Gypsum Board "G" (FPL) ""3/8 80.5 “T~ IN *3 44*5 -4- Gypsum Board "K" 3/8 47 A 13.3 29*9

6 Mineral Base Tile 3/4 -19.3 3 0 4 10*5 60*0

2b Gypsum Board "L" 1/2 bi*2 7*9 10bc0

' 32 Plastic 'A" 1/8 89*4 b 4*0 42*3

22 Fbd "I" Fire Retardant

Finish (FPL) 1/2 19 * 0 6 * 4 b 4*5 53*8 14 Fbd "<!" + Mineral Spray 1/2 21 * 9 7 * 7 b 3*4 28*9

Glass Fiber Batt 1 A, 8 1*2

l

178“ 60* b

2 Cellulose Mineral Board 7/8 47 <.8 7 . b b 1*3 ”40"'

b Glass Fiber Tile . 3/8 10*1 0*6 b 1.2 77*7

lb Fbd "J"+ 1/8" Mineral

Surface b/8 42*2 7° 5 b 1*2 50*7

81 Plywood Fir Ext* + Aluminum Foil lA 4l*6 6*3 3 0*9 65*7

H- Llass Fbd

2 11*0 oA b 0*6 37* 3 1 Asbestos Cement Board 3/16 11 7 • 0 0 * 6 b 0

(LPL) Designates materials received from Forest Products Laboratory Based on weight after drying at 221°F (105°C)

f Pests on same materials but samples from other batches* Fbd . Fiberboard

Perf. Perforated
TABLE II CONTINUED

Flame Spread Data Smoke Data No.

Flame

Spread

Index

Is

UL

Flame

Spread

Factor

SS-A-1181

Classification

Flashover

Time

(British)

Deposit Based

on

Red

Oak

UL

Smoke

Factor

min mg

.... .336 0.1 30

17

2 76 285 5 o 00 0.4 130 357 28

' 2^6 0.2 70 8

143 D 0.3 100

30

~^W~ 4.1 1400 18

121 113 D 6 o 15 5.2 1700 1900

23

116 0.3 100 16

107 0.4 130

13

~1T~ 160 D 0 o 3 100 100 24

77 D Hi 0 o 2 70 jEI 21

i 0.2 • 70 9

59 . D 0.6 200

12

56 130 9.7 3200 752 34

27 . 10.35 0 o 9 300

11

... . 3Q “FIT 5,7 ... 1900 ^65" 33’

14.3 10 C 0 o 0 6 0 26

Ool 30 3

10 o 5 10' OoO 0 8

7 = 9 12 o 8 16 o 36 Ool . 3 Q... 17 25

4„0 3°3 1100 3 2

14- D Oo 5 170 14

22

M 0,2 70 14

1 o 8 0 o 2 70 7

1.3 9-10 f 16.45 Ool 30 0

+

' 2

1.2 10-15+ Oo 3 100 5

1.2 C Oo 2 70

i5

0.9 D 0.1 30

31

Oo 6 B 0 o 2 70 4

0 0 A 17.10 OoO 0 1
>

.

•

.

'
TABLE III

Reproducibility, of Test Data

SdiEcimen Tests on one Day Tests of a Period of Month

No 0 Material Noo Sped- Coefficient a0 0 Coefficient

mens of variation Specimens of variation

2b Red Oak 5 10 0 9%

19 Red Oak* 19 I 80 %

23 Hardboard 6 6.9

28 ' Fiberboard "A" 8 8.8

8 Fiberboard mjm 8 5.1 9 5.0

* Includes data on samples covering a density range of 30° 7 to ^60 9 lb/ft3


Figure 1

Radiant panel flame spread test equipment
Figure 1

*


Figure 2

Specimen holder

Figure 4- Detail of thermocouple mounting arrangement.

Figure 5

Smoke sampling tube and parts.
in

Ld

cr

ZDO

h-322O3

(£> x<

croo

CD

C\J

l±J cr3O

Li_


Figure 3

Drawing of test equipment

showing important dimensions
o

ro

LU

cr3

e>

u_

FLOOR

LEVEL


Figure 6

Typical stack thermocouple calibration curve.

Figure 7

Energy flux incident at specimen surface.

Figure 8

Effect of position of stack on

thermocouple temperature rise.

Figure 9

Progress of flame along specimen length for

several materials. (Numbers correspond with

specimen number in table II).

Figure 10

Comparative data from two different

flame spread test methods.
STACK

THERMOCOUPLE

TEMPERATURE

RISE,

DEG.

F

CLEARANCE BETWEEN STACK AND PANEL, INCHES

FIGURE 8

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