NATIONAL BUREAU OF STANDARDS REPORT

This-report has, been prepared

for fntcTmatTon and record

Twrpwea iwtft ’iS“rr0H0' be referee:

8622 iir^f-poblteatfoft.

A FLAMMABILITY TEST FOR WALK-OFF MATS

by

Marjorie W. Sandholzer

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards is a principal focal point in the Federal Government for assuring

maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. Its responsibilities include development and maintenance of the national stand- ards of measurement, and the provisions of means for making measurements consistent with those standards; determination of physical constants and properties of materials; development of methods

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listing of its four Institutes and their organizational units. Institute for Basic Standards. Electricity. Metrology. Heat. Radiation Physics. Mechanics. Applied Mathematics. Atomic Physics. Physical Chemistry. Laboratory Astrophysics.* Radio Standards Laboratory: Radio Standards Physics; Radio Standards Engineering.** Office of Standard Ref- erence Data. Institute for Materials Research. Analytical Chemistry. Polymers. Metallurgy. Inorganic Mate,

rials. Reactor Radiations. Cryogenics.** Office of Standard Reference Materials. Central Radio Propagation Laboratory.** Ionosphere Research and Propagation. Troposphere

and Space Telecommunications. Radio Systems. Upper Atmosphere and Space Physics.

Institute for Applied Technology. Textiles and Apparel Technology Center. Building Research.

Industrial Equipment. Information Technology. Performance Test Development. Instrumentation.

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* NBS Group, Joint Institute for Laboratory Astrophysics at the University of Colorado. Located at Boulder, Colorado.
NATIONAL

NBS PROJECT

42102 - 30-4210627

NATIONAL BUREAU OF

for use within the Govemmei

and review. For this reason, whole or in part, is not au Bureau of Standards, Washir

the Report has been specific

BUREAU OF STANDARDS REPORT

January 15 , 1965

NBS REPORT

8622

A Flammability Test for Walk-Off Mats

by

Marjorie W. Sanholzer

for

Public Buildings Service

General Services Administration

Fund Symbol CO. 256 . 501 . 72140 . 256 .

IMPORTANT NOTICE

gress accounting documents intended Approved for public release by the is subiected to additional evaluation

I—* • , r-,1 \t , • it , r ure listing of this Report, either in Director of the National Institute of

(he otfjce of the Director Natl0na i Standards and Technology (NIST) r , by the Government agency for which on October 9, 2015. 11 c°P' es tor its own use <NBS>

U.s. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

A FLAMMABILITY TEST FOR WALK-OFF MATS

by

Marjorie W. Sandholzer

ABSTRACT

A study of a timed-burning fuel pellet test for

determining tbe flammability of waltc-off mats is

reported. The effects of varied test conditions and

techniques 5 and the selection of appropriate performance

criteria, were investigated. The resulting proposed test

procedure is considered suitable for general laboratory

use on a field basis.

A Flammability Test for Walk-Off Mats

1. Introduction

As the use of walk-off mats at the entrances of public buildings

increased, it was found that, unless a flame retardant treatment had been

applied, the pile surface of the mat might be in a hazardously flammable

condition. Although the backing of the mat would not easily become involved, the brush of a match or other flame might be sufficient to touch

off flames which spread over the whole pile surface in a matter of seconds.

Inasmuch as such mats were a regular procurement item of the General Services Administration, it was necessary for that agency to adopt a method of

measuring the flammability and to establish performance requirements. After

some preliminary trials of standard flame spread test methods, it appeared

that a methenamine fuel pellet test suggested by a commercial concern might

prove satisfactory for the particular purpose. The test had been presented

in outline form, however, and the GSA requested a study of tire method to

determine its general usefulness and to provide a more completely defined

procedure. It was desired that the test be kept sufficiently simple to permit its use o.i. a field basis in various conveniently available laboratories.

2. Materials

Limited portions of treated mats, provided by the GSA for preliminary trials, were available, and in addition, several mats from the

regular GSA procurement with unidentified dust control and flame retardant

treatments were supplied. Untreated mats, mats treated with a dust con- trol compound only, and mats treated with both a dust control compound and

a flame 'etar lant treatment were procured from a commercial manufacturer.

3 - Expa r iment a 1 Wo ck

Using the test procedure suggested by th e commercial company as a basic outline, a schedule of experimental work was arranged to investigate

the need for more specific definition of certain parts of the procedure.

A. Source of Ignition

.

The suggested procedure specified methenamine timed-burning tablets

(Eli Lilly No. 1588) as the source of ignition, the tablet being ignited

by a match. No other type of ignition source was studied but different

ways of placing the methenamine pellet on the pile of the mat were tried.

The depth to which the pellet was embedded in the pile seemed of particular interest.

The burning of the pellet proved to be quite sensitive to any re- striction in air supply. When it was pushed down into the pile of the

mat it was not only difficult to ignite but would burn only briefly. If

it occasionally sank slightly into the pile as it burned, it might go out

with a small bead remaining unconsumed. It appeared best to place the

pellet as lightly as possible on the pile.

2

The time required for a pellet to burn out, as used in this particular application, varied widely. It usually fell in the range of U - 2 minutes, but instances outside that range in each direction were noted.

Whether the pellet lay flat on the pile or was tipped up on edge did not

appear to affect significantly the time or intensity of burning.

B . Sample Preparation.

The suggested procedure called for conditioning the 6-inch square

test specimens at 65% RH and 70 F for 24 hours and testing them within

15 minutes after removal from the conditioning room. Each specimen was fluffed by giving it three shakes before testing.

In the experimental program conducted, the following variations of

temperature and humidity were included in the conditioning procedures:

(1) Ambient laboratory conditions where, with the artificial

heating season in operation, the humidity was generally

low (15 - 25%),

(2) 65% RH and 70 F for 3 days or more, with testing immediately

upon removal from the conditioning room,

(3) 65% RH and 70° F for 3 days or more, followed by a 15-minute

exposure to ambient laboratory conditions before test, and

(4) one hour in an oven at 105° C followed by 5-10 minutes of

cooling in a desiccator over silica gel before test.

For fluffing the pile, the suggested shaking was used and, in

addition, a brushing procedure was tried. A plastic-bristle brush, of

the type sold in brush- scraper combinations for removing snow from automobile windshields, was passed once (or twice on badly flattened pile) over the surface of the specimen.

C. Conduct of the Test.

In conducting the tests, a comparison was made between placing the

specimen on a table in the open laboratory and placing it inside a ven- tilated cabinet, during exposure to the burning pellet. The pellet was placed at the center of the specimen.

The criteria used as a measure of flammability were basically the

"rate of flame spread and char diameter" specified in the suggested

procedure. Rate of flame spread has meaning only for materials which are relatively flammable and show continuing progress of flame travel over the

surface. For such specimens, however, it appeared the most suitable criterion, and was noted in terms of the time required for the flame to

spread over the entire surface of the specimen. For the most flammable

mats this was an easily determined endpoint, but where the flame spread was highly erratic, it became unduly variable and its definition a little

uncertain --one or more small islands of pile might remain untouched

- 3

-

while the surface all around was completely involved. In later trials, the

time at which the flame reached an edge of the specimen proved a more definite

and dependable endpoint and was incorporated in the suggested test procedure.

The additional endpoint of total involvement may often be of interest also,

however, as a further indication of the speed and ease of flame spread.

For specimens on which the flame did not cover a major part of the

specimen, the charred area offered the most convenient evidence of the ex- tent of flame travel. The longest straight-line dimension across the charred

area or areas was taken as an appropriate measure of the extent of flame

spread. On the specimens tested, the char was clearly defined and easily

measured after burning had ceased, and this would probably be the usual case,

inasmuch as plain black would be an unlikely color for the mats. However, some thought was given to a simple means of gaging the flame travel in the

possible situation where the char may not be clearly distinguishable. Twelve

straight pins, three on each of the diagonal lines from the center to the

four corners of the specimen, and set one inch apart starting one inch from

the center, provided a pattern of known points from which the flame spread

could be judged reasonably well as the burning progressed. As a guide in

placing the pins, a triangle of cardboard, cut to fit inside two adjacent

diagonals and suitably marked at one-inch intervals, was laid on the speci- men with the hypotenuse first along one side and then along the opposite

side of the specimen.

4. Discussion of Results

The results of the tests made under varied conditions of procedure are shown in Table 1. Considering the effect of humidity, there was clearly the

usual trend toward an increase in flammability with increased drying of the

material. As might be expected, the effect was generally small with the more

flame resistant mats, although it became significant with the more flammable

types. The effect of heating at 105 C did not appear to be more than that of

pronounced drying, without loss of the flame retardant (at least for the particular treatments applied) . For the purpose of indicating the presence of an effective flame retardant rather than distinguishing between certain degrees

of flammability, a convenient means of establishing fairly reproducible humidity conditions would appear more important than the precise conditions selected.

Inasmuch as an oven is more commonly available than a conditioning room or cabinet maintained at higher humidities, we would suggest conditioning the

specimens in an oven at 60 C (140 F) . Although the humidity in the oven at

that temperature will vary somewhat with seasonal variations, the moisture

regain of cotton does not change greatly over the probable range of oven humidity

.

The results indicated little difference between the shaking and brushing methods of fluffing the pile for mats in the usual clean or freshly

treated condition. It was observed, however, that on heavily soiled or otherwise severely flattened mats, shaking was not sufficient to raise the

pile to a normal condition. As it appeared that it might be easier to describe and procure a reasonably standard comb than a brush, the suitability

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the

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5 of a combing procedure rather than brushing was considered. Trials on various

representative mats indicated that combing should be an effective and satisfactory procedure.

Testing inside the ventilated cabinet appeared to restrict the flame

spread significantly in some cases. While testing in the open laboratory would

therefore seem preferable, it should be noted that during this study the laboratory was quieter and more free from drafts than might usually be expected.

For this reason some study of wire screening, as a possible draft deterrent

which would not restrict the air supply, was made. The four-sided guard of

16-mesh galvanized window screen devised for the purpose proved reasonably

effective in protecting the pellet flame from ordinary minor disturbances,

such as those caused by the movement of personnel working near or walking by

the test site. It should be feasible to avoid strong drafts, such as that

from an electric fan, in selecting the test site.

To study the effect of soiling on the flammability of the mats, a com- posite mat was made up of the three types procured from a commercial manufacturer

and was placed at the entrance of a building where, after about ten days,

the soiling had become extremely heavy, amounting to about 1% on the untreated

portion and 5 - 6 % on the treated portions. In testing the segments of the

soiled mat the specimens were room conditioned and the pile raised by brushing. Six specimens of each segment were tested. The portion which had been

treated with both the dust control compound and the fire retardant showed an average char of 1.0 inch, practically the same as the 0.9 inch figure obtained before soiling. The average char values for the untreated segment and

the segment treated with dust control compound only were 2.1 in. and 1.6 in.,

respectively, whereas before soiling, the flame spread over the whole surface

of these two types in average times of 26 sec. and 7 sec., respectively

(Table 1) . Although the soiling in this trial was undoubtedly heavier than

is usually allowed to accumulate, the results suggest that tests made on mats in service may not indicate the full hazard presented when they are clean and freshly treated.

5. Proposed Test Procedure

From the testing experience and a study of the results of the experimental work, the following description of a suggested flammability test for

walk-off mats was developed.

Scope: This method is intended to determine the presence of hazardous

flammability in walk-off mats. It is designed to use equipment that is

easily portable or commonly available, to facilitate its use on a field

basis

.

A . Test Equipment :

(1) Methenamine timed-burning tablets (Eli Lilly No. 1588) as the

ignition medium and matches to ignite the

o tablets,

(2) An oven for conditioning specimens at 60 C,

(3) A comb with 7 or 8 smooth rounded teeth per inch for raising

the pile of the mat,

(4) A four- sided draft guard, open at top and bottom and one foot

square on a side, made of 16-mesh window-screen fastened to a rigid frame of rod or heavy wire, to protect the flame from

minor drafts, and

(5) A stop watch to time the flame spread.

B . Test Specimens:

The mats shall be tested in a clean or freshly treated condition.

Three test specimens, each six inches square, shall be cut from each mat

under test.

C . Specimen Preparation:

The specimens shall be laid or hung in a preheated oven in such a way that there is free access of air all around each one. They shall be

conditioned at 60±3 C (140 F) for 1-1^ hours, then removed individually,

fluffed, and tested immediately. The fluffing shall consist of drawing

the comb once across the pile surface of the specimen with sufficient

pressure to raise the pile to an upright position. (If the pile is se- verely flattened two or three passages of the comb may be used.) The

specimen should be tested within 45 seconds after removal from the oven,

D . Test Procedure :

The test shall be conducted in the open laboratory but in a site

removed from strong wind or drafts. The prepared specimen shall be laid,

pile upward, on a flat flame-resistant surface, approximately centered

inside the four-sided screen draft guard. A methenamine tablet shall be

placed lightly on the pile surface at the center of the specimen and ignited with a match. Timing with the stopwatch shall be started at the

moment of ignition of the tablet. If the flame spreads over the surface

the time at which it reaches an edge shall be noted, but the timing shall

be continued until the whole surface has become involved, if the flame

spreads to that extent. If the flame does not reach an edge of the specimen, the test shall be stopped when all flame and glow have ceased. The

extent of flame spread shall be determined as the longest straight-line

dimension across the charred area or areas, measured to the nearest 0.1

inch. Figures 1 and 2 show a test in progress and some typical char patterns.

E . Report

:

The results shall be reported as the average time for flame to

reach an edge of the specimen and the average time for the flame to spread

over the total surface of the specimen (if it continues to that extent),

or the average char length, measured as the longest straight-line dimension across the charred area or areas.

6. Application of Proposed Procedure

To illustrate the type of data and possible problems of interpre£»t ion

which might be developed, samples of the various mats available were tested

by the procedure, as described above, with the exception that the oven con- ditioning was omitted.

7

The 15 - 207, humidity in the winter-heated laboratory was within the

seasonal humidity range of the oven at 60 C. The results of the tests are shown in Table 2.

Table 2

Results Obtained by Suggested Procedure

(Room conditioned)

Mat

identification

No. of Average time for flame to reach Average

Specimens edge total surface char length

Seconds Seconds Inches

Procured commercially

Untreated 10

Dust control 10

Dust control

flame retardant

Supplied by GSA

A

BD

E

F

4

4

5

3

6

13

6

NS

5 NS

NS

8

11

30

19

11 *

20

48

> 6

> 6

1 .

1

2 . 1 *

1 .

1

0.9

1.7*

2 . 5**

NS No significant spread of flame

* One specimen only. On Mat A, flame failed to reach an edge on one specimen,

and failed to cover total surface on two others. On Mat E, flame failed to

reach an edge on one specimen.

** Two specimens only (on which flame failed to reach an edge)

On the basis of such data there would clearly be no difficulty in

distinguishing between mats which had no flame retardant treatment and

those which were very well treated. Some treatments, however, would present problems of interpretation and definition. For three of the types of

mats tested, some specimens showed flame spread over the whole surface while

on others it was confined to a small area around the pellet. Although this

situation would have to be recognized in establishing performance requirements, it would appear than an adequately clear and useful definition of ac- ceptability should be possible. Perhaps the simplest definition might Le that

flame should not reach an edge of any specimen, but other definitions would

be feasible depending on the degree of flame resistance desired.

FR 3646 USCOMM-NBS-DC

Figure

2.

Specimens

after

test

showing

various

patterns

of

char.
4'f

Figure

1.

Methenamine

pellet

test

in

progress.

ii

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