NBSIR 78-1436

Flammability Testing for Carpet

I. A. Benjamin and S. Davis

Center for Fire Research

National Engineering Laboratory

National Bureau of Standards

Washington, D.C. 20234

April 1978

Final Report

U S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 78-1436

FLAMMABILITY TESTING FOR CARPET

I. A. Benjamin and S. Davis

Center for Fire Research

National Engineering Laboratory

National Bureau of Standards

Washington, D.C. 20234

April 1978

Final Report

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

CONTENTS

Page

Abstract 1

1 . BACKGROUND

1.1 Basic Building Materials

1.2 Floor Coverings ....

1

1

2

2. THE THREE STAGES OF FIRE 2

2.1 Stage 1

2.2 Stage 2

2.3 Stage 3

3. TESTING CARPET FOR ROOM USE

3.1 The Pill Test

3.2 Evaluation of Fire Incidents. .

4. TESTING CARPET FOR CORRIDOR USE... . 4.1 The Tunnel Test

4.2 The Chamber Test

4.3 The Flooring Radiant Panel Test

4.4 Critical Radiant Flux

4.5 Why Test?

4.6 Recommended Criteria

4.7 Sprinklered Buildings

5. REFERENCES 9

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FLAMMABILITY TESTING FOR CARPET

I. A. Benjamin and S. Davis

Abstract

As use of carpet has increased in recent

years, more and more attention has been focused

on different test methods for measuring its

flammability.

The carpet industry, as well as regulatory

agencies have been working on test procedures

which would provide consumer protection and not

be overly burdensome.

All carpet sold in this country must pass

the "pill test." The pill test provides "firstto-ignite" protection for carpet flooring systems

located within rooms or undivided building spaces.

Criteria have been proposed using the new

Flooring Radiant Panel Test which provide

equivalent safety to that level provided by the

Life Safety Code. The Flooring Radiant Panel

Test is both reproducible and related to "real

world" performance. This publication explains

the features of this test.

Key words: Carpet systems; criteria; fire growth;

flammability; flooring radiant panel test;

testing.

1. BACKGROUND

1.1 Basic Building Materials

Building regulations, including building codes, fire

prevention codes and the like, contain various restrictions

limiting the use of flammable materials on walls, ceilings,

and floors of buildings. This is essential because of the

way flammability characteristics of these interior materials

can affect the behavior of a fire. The less a fire spreads,

the less threat it becomes to life and property and the

easier it is to control and extinguish.

1
1.2 Floor Coverings

Floor coverings such as wood, vinyl asbestos tile,

terazzo, and linoleum, which have long been used, show little

tendency to affect the spread of fire.

In the late 1950'

s

and early 1960's, production techniques were developed within the carpet industry whereby carpet

became competitive in cost with conventional flooring and

offered certain advantages over other materials. Along

with this widespread usage came a few claims that carpet

aided in the spread of fire. Noting these factors, some

fire officials expressed concern that some carpet material

could react significantly different in a fire situation than

other commonly used flooring materials. As a result of this

concern, a first attempt was made in mid-1965 to regulate

the floor covering by a flammability test and much research

and development work was undertaken to better understand the

phenomenon of fire spread.

2. THE THREE STAGES OF FIRE

In order to understand the testing and measurement of

the behavior of flooring systems in a fire situation, it is

necessary to consider fire in three distinct stages.

2.1 Stage 1

Stage 1 is the "ignition and its initial growth." For

example, this could be the first sign of a flame in a wastebasket or overstuffed sofa. A fire will be considered as

being in Stage 1 while the fire remains in the area of the

ignition

.

2 . 2 Stage 2

Stage 2 is the growth to "full involvement" - or

flashover - of the room or space of origin. The fire has

progressed through Stage 2 when everything in the room is

burning

.

The test methods described herein do not pertain to

carpet used other than for floor covering.

2
2 . 3 Stage 3

Stage 3 is after the time of "flashover" when the fire

spreads beyond the room of origin and spills over into the

corridor and the fire begins to spread along the passageway.

3. TESTING CARPET FOR ROOM USE

Since the purpose of interior finish regulations is

to avoid rapid fire spread, the following question arises:

What level of flame spread resistance is necessary

to prevent involvement of carpet during a Stage 1

fire?

3.1 The Pill Test

Since April 1971, Federal regulations have required that

all carpet sold in the United States pass the Pill Test [ 1

]

2 . The test will screen out carpet easily ignited by a small

incendiary source; it measures the response of carpet exposed

to a timed burning tablet in the absence of an imposed

external radiation field. Carpet which passed the Pill

Test will not spread flame during a Stage 1 fire. This was

further demonstrated in a series of room tests conducted by

the National Bureau of Standards [2]. This series of

experiments reconfirmed the conclusion that:

"Carpet systems, used in rooms, will not normally

spread fire provided they meet the requirements

of the DOC FF 1-70 (The Pill Test)."

3.2 Evaluation of Fire Incidents

The National Bureau of Standards conducted an evaluation

of fire incidents [3] in which flame spread was reported to

have occurred in, or to have involved, carpet. In all but

seven cases, the analysis showed either that the carpet was

excessively flammable and would not pass the Pill Test, or

that the available data did not clearly show that carpet was

a significant contributor. Further analysis of the seven

cases revealed that in none did carpet which passed the Pill

Test propagate flame during a Stage 1 exposure. The study

did reveal that when a very large fire source exists it

Numbers in brackets refer to the literature references

listed at the end of this paper.

3
could result in carpet burning. Therefore, the analysis

clearly showed that flame propagation was only produced in

carpet when exposed to a fully-developed room fire and then

only when the carpet was located in a corridor (Stage 3)

.

4. TESTING CARPET FOR CORRIDOR USE

The following question must now be addressed:

What level of flame spread resistance is necessary

to prevent a Stage 3 fire from spreading to other

parts of the building?

To answer this question, extensive research has been carried

out at the National Bureau of Standards, as well as at other

organizations. This research involved model corridor [4]

and full-scale corridor [5-9] experiments. The studies were

conducted to develop an understanding of the mechanisms by

which fire spreads within carpeted corridors under the

influence of a large fire source, a Stage 3 fire. In these

studies, fire from a room which has passed flashover extended

into a corridor through an open door. The test program led

to the following three conclusions:

• The amount of energy radiated onto the flooring

system is a significant determinant as to whether

or not a carpet system will propagate flame.

• To radiate sufficient energy onto the floor to

propagate flame, the fire source (in the room)

must be large enough to intensely heat the air

and ceiling in the corridor.

• Flammable materials mounted on walls or ceilings

have a greater effect on flame spread than similar

materials installed on the floor.

The assumption that carpet systems located within corridors

should be regulated, raises several questions:

• Which test method provides the best information

for judging relative fire hazard?

• Which test is most suitable for evaluating floor

covering assemblies (such as carpet and separate

underlayment)

?

• Which test method provides reasonably reproducible

data correlated to the "real world?"

4
4.1

The Tunnel Test

The ASTM E-84 "Tunnel Test" was originally developed to

evaluate the fire hazards of wall and ceiling materials.

When this method is used for carpet, a conditioned sample

is mounted upside down on the "roof" of the tunnel. As a consequence, this method does not provide meaningful reallife information for judging the relative fire hazards of

carpet. There is agreement within the technical fire

protection community that the tunnel test does not yield

data which predict the probable performance of flooring

systems in actual building fires.

4.2

The Chamber Test

The Chamber Test (UL-992) was developed to evaluate

fire behavior of flooring systems. The test is a variation

of the Tunnel Test in that the sample is exposed to a high

intensity burner in a tunnel. The specimen is placed on the

floor, enabling floor covering assemblies, including carpet

with separate under layment , to be evaluated in this apparatus.

In this test the forced draft supplying air to the flame

sweeps the carpet in the opposite direction to that observed

on the floor in full-scale corridor fires.

This test has technical shortcomings [3,11] in that:

• The Chamber Test generates an index which has

an undetermined relevance to fire hazard.

• The degree of reproducibility of data resulting

from the Chamber Test is not established.

• Indices produced by tests conducted in the

Chamber tend to divide materials into two

polarized groups; therefore, a continuous

classification scale is not provided to categorize materials.

4.3

The Flooring Radiant Panel Test

Since neither the existing Tunnel Test nor the

Chamber Test adequately evaluates flooring materials, a new

test was developed, called the Flooring Radiant Panel Test

[10] . This test is designed to simulate a likely set of

conditions which may lead to fire spread in a carpet system.

5
The Flooring Radiant Panel concept evolved from

information obtained from the full-scale corridor fire test

programs. The full-scale tests showed that the level of

energy radiating onto carpet significantly affected whether

or not progressive flaming occurred. This test method

determines a critical radiant flux, measured in watts per

square centimeter (W/cm 2 ). Critical radiant flux is the

lowest level of radiant energy necessary for a fire to

continue to burn and spread.

The Flooring Radiant Panel Test is different from most

other fire test methods in that it measures an actual property

of the carpet system and is not based on an arbitrary scale.

The test yields data correlated to the relative performance

of materials in actual installations. In this test, the

floor covering system in installed on the "floor" of the

test chamber similar to a "real world" situation. The test

can accomodate floor system assemblies, such as carpet with

a separate under layment

.

The Flooring Radiant Panel apparatus involves a horizontally-mounted floor covering test sample which receives

radiant energy from a gas-air fueled radiant panel mounted

above one end of the sample and inclined at an angle of 30°.

The sample and radiant panel are located within a test

chamber. Air is allowed to flow in the bottom of the test

chamber and exits via a stack located at the top of the

chamber at the opposite end from the radiant panel.

The radiant panel generates a radiant flux profile along

the length of the sample ranging from a maximum of 1.1 W/cm 2 immediately under the panel to approximately 0.1 W/cm2 at

the end of the test sample remote from the panel. A gasfired pilot burner is used to initiate the ignition on the

floor covering sample immediately below the radiant panel

and the test is continued until the flooring system ceases

to burn. The distance the flooring system burns to extinguishment is converted to watts per square centimeter from

a calibration graph and is reported as critical radiant flux.

4.4 Critical Radiant Flux

The result of the test is reported as the critical

radiant flux (W/cm 2 ). This is the minimum radiant energy

a fire needs to sustain flame propagation in the flooring

system. In this test, the lower the number, the greater is

the tendency of the system to spread flame. Conversely, the

higher the number, the more resistant is the material to

flame propagation. This number is the average of at least

three replicate burns.

6
The test apparatus is capable of accommodating materials

which have critical radiant flux values ranging from approximately 1.1 to 0.1 W/cm 2

. To relate these values to the

critical radiant flux value of a traditionally used material,

note that oak flooring has a critical radiant flux value of

approximatley 0.35 to 0.40 W/cm 2

. Carpet may have values

from less than 0.1 to greater than 1.1 W/cm 2

. Data from the test have been shown to be both reproducible and repeatable, based upon a round-robin test series

conducted under the supervision of the National Bureau of

Standards, involving ten carpet systems and twelve

laboratories

4.5 Why Test?

Experience has shown there is no way to predict the

performance of a carpet system without conducting a test.

The resistance of carpet to the spread of flame is a function

of

• The generic type of face yarns used,

m The type of construction, including yarn texture,

• The density of the pile, and

• The presence of an under layment , attached or

separate

Also, the presence of a separate underlayment may significantly affect the performance of carpet compared to tests

conducted on the same carpet without underlayment [10].

Therefore, carpet tested without an underlayment may not be

acceptable if used with an underlayment. Emphasis should

be given to conducting tests based upon the type of assembly

contemplated for use.

4.6 Recommended Criteria

The most widely noted fires in which carpet has been

reported as a contributor to early fire growth essentially

involve the Harmer House Nursing Home, the Baptist Towers,

and Pioneer Hotel fires. In each of these instances, carpet

taken from the buildings was determined to have a critical

radiant flux of less than 0.1 W/cm 2

. The minimum critical radiant flux limits (based upon

the average of three replicate tests) being recommended

[11,12] are:

7
• 0.45 W/cm 2 within corridors and exitways of hospitals

and nursing homes, and

• 0.22 W/cm2 within corridors and exitways of other

occupancies except one- and two-family dwellings.

These values should provide a level of safety for the

carpeted corridor which is equal to or in excess of that

now required in the NFPA 101 Life Safety Code [13]

.

These limits are based upon:

• Comparison to performance of traditionally used

materials

,

• Performance of flooring systems under full-scale

corridor tests, and

• Evaluation of carpet systems which have been

reported as significantly contributing to flame

spread in actual fires.

The higher level of critical radiant flux of 0.45 W/cm 2

, recommended for health care facilities, is based on the

assumption that non-ambulatory occupants (patients) require

a higher level of protection than do occupants who are mobile

and are capable of rapid escape.

4.7 Sprinklered Buildings

The radiant flux limits suggested for regulating floor

coverings are based upon the possibility of a Stage 2 and

Stage 3 fire. In a building completely protected by an

automatic sprinkler system, the likelihood of a Stage 2

fire developing becomes remote. The need for regulation

of floor coverings under these circumstances diminishes.

Therefore, the criteria suggested above could be reduced

or eliminated in the case where automatic sprinkler

protection is provided [12].

8
5. REFERENCES

[1] Standard for the Surface Flammability of Carpets and

Rugs, DOC-FF-1-7 0 ; Federal Register, Vol. 35, No. 74 , p. 6211 (April 16 , 1970) .

[2] Tu, K.-M. and Davis, S., Flame Spread of Carpet Systems

Involved in Room Fires, Nat. Bur. Stand. (U.S.),

NBSIR 76-1013 (June 1976) .

[3] Quintiere, J. and Huggett, C., An Evaluation of Flame

Spread Test Methods for Floor Covering Materials,

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

pp. 59-89 (Nov. 1974).

[4] Denyes, W. and Quintiere, J., Experimental and

Analytical Studies of Floor Covering Flammability with

a Model Corridor, Nat. Bur. Stand. (U.S.), NBSIR 73-199

(May 1973) .

[5] Fung, C. W. , Suchomel, M. R. and Oglesby, P. L.,

The NBS Program on Corridor Fires, NFPA Fire Journal

(May 1973) .

[6] McGuire, J. H., The Spread of Fire in Corridors,

National Research Council of Canada, Division of

Building Research (December 1967) .

[7] Christian, W. J. and Waterman, T. E,, Fire Behavior

of Interior Finish Materials, IIT Research Institute,

Fire Technology (August 1970) .

[8] Fung, C. W. , Suchomel, R. and Oglesby, P. L.,

NBS Corridor Fire Tests: Energy & Radiation Models,

Nat. Bur. Stand. (U.S.), Technical Note 794 (October

1973) .

[9] Quintiere, J., The Application and Interpretation of

a Test Method to Determine the Hazard of Floor Covering

Fire Spread in Building Corridors, International

Symposium, Fire Safety of Combustible Materials,

Edinburgh, Scotland, pp. 355-367 (October 1975).

[10] Kashiwagi, T., Experimental Observation of Flame Spread

Characteristics Over Selected Carpets, JFF/Consumer

Product Flammability, Vol. 1, pp. 367-689 (December 1974).

[11] Benjamin, I. A. and Adams, C. H., Proposed Criteria

for Use of the Critical Radiant Flux Test Method,

Nat. Bur. Stand. (U.S.), NBSIR 75-950 (December 1975).

9
[12] Benjamin, I. A. and Adams, C. H., The Flooring Radiant

Panel Test and Proposed Criteria, NFPA Fire Journal,

Vol. 70, No. 2 ("larch 1976).

[13] Life Safety Code 1976, NFPA No. 101, National Fire

Protection Association, Boston, Mass.

10
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 78-1436

2. Gov’t Accession

No.

3. Recipient’s Accession No.

4. TITLE AND SUBTITLE

Flammability Testing for Carpet

5. Publication Date April 1978

6. Performing Organization Code

7. AUTHOR(S)

I. A. Benjamin and S. Davis

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 4927677

11. Contract/Grant No.

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

)

Same as No. 9

13. Type of Report & Period Covered Final Report

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.) As use of carpet has increased in recent

years, more and more attention has been focused

on different test methods for measuring its

flammability.

The carpet industry, as well as regulatory

agencies have been working on test procedures

which would provide consumer protection and not

be overly burdensome.

All carpet sold in this country must pass

the "pill test." The pill test provides "firstto-ignite" protection for carpet flooring systems

located within rooms or undivided building spaces.

Criteria have been proposed using the new Flooring Radiant Panel Test which provide equivalent safety to that

level provided by the Life Safety Code. The Flooring Radiant Panel

Test is both reproducible and related to "real world" performance.

This publication explains the features of this test.

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

flooring radiant panel test; testing.

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