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NBSIR 79-1922

An Interlaboratory Evaluation of the

ASTM E 84-77a Tunnel Test Modified

c By the Consumer Product Safety

1 Commission for Cellulosic Loose Fill

Insulation

J. Randall Lawson

Center for Fire Research

National Engineering Laboratory

National Bureau of Standards

Washington, D.C. 20234

November 1979

Final Report

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79-1922

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Prepared for: U.S. Consumer Product Safety Commission

Textile and Mechanical Engineering Group

, Maryland 20202

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AN INTERLABORATORY EVALUATION OF THE

ASTM E 84-77a TUNNEL TEST MODIFIED ; BY THE CONSUMER PRODUCT SAFETY

COMMISSION FOR CELLULOSIC LOOSE FILL

INSULATION

J. Randall Lawson

Center for Fire Research

National Engineering Laboratory

National Bureau of Standards

Washington, D.C. 20234

November 1979

Final Report

Prepared for: U.S. Consumer Product Safety Commission

Textile and Mechanical Engineering Group

Bethesda, Maryland 20202

U.S. DEPARTMENT OF COMMERCE

Luther H. Hodges, Jr., Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director

TABLE OF CONTENTS

Page

LIST OF TABLES iv

LIST OF FIGURES iv

Abstract 1

1. INTRODUCTION 2

2. TEST METHOD AND APPARATUS . . . . 3

3. PARTICIPANTS 4

4. LABORATORY SURVEY 4

5. MATERIALS AND SAMPLE PREPARATION 6

6. EXPERIMENTAL DESIGN 7

6.1 Test Procedure 7 6.2 Laboratory Specimen Preparation 7

6.3 Test Density 7

6.4 Order of Testing 8

7. TEST RESULTS AND DISCUSSION 8

7.1 Statistical Procedures 8 7.2 Tunnel Test Data 8 7.3 Comparison of Fire Test Methods 10

7.4 Variability 10

8. SUMMARY AND CONCLUSIONS 11

9. ACKNOWLEDGEMENTS 12

10. REFERENCES 13

APPENDIX A A1

APPENDIX B B-l

APPENDIX C C-l

APPENDIX D D-l

iii
LIST OF TABLES

Page

Table 1. Characteristics of the ASTM E 84-77a tunnels 14

Table 2. Tunnel test data, flame spread classifications (FSC) .... 16

Table 3. E 84 Tunnel Test cell averages ordered from lowest

to highest flame spread classification (FSC) 17

Table 4. E 84 Tunnel Test results cell standard deviations ordered

lowest to highest flame spread classification (FSC) .... 17

Table 5. Precision estimates of flame spread classifications (FSC) . 18

Table 6. Comparison of precision estimates for fire test methods . . 18

Table 7. Screen wire comparison using the modified ASTM E 84-77a

test procedure 18

LIST OF FIGURES

Page

Figure 1. Example of E 84-77a tunnel used in the interlaboratory

program 19

Figure 2. Details of the E 84-77a tunnel 20

Figure 3. Cross section of tunnel at BB of figure 2 21

Figure 4. Screen wire test frames in place on tunnel ledges 22

Figure 5. Screen test frames filled with cellulosic insulation

before testing 23

Figure 6. Examples of char and flaming observed by laboratories

after test was completed 24
AN INTERLABORATORY EVALUATION OF THE ASTM E 84-7 7a TUNNEL

TEST MODIFIED BY THE CONSUMER PRODUCT SAFETY COMMISSION

FOR CELLULOSIC LOOSE FILL INSULATION

J. Randall Lawson

Abstract

An interlaboratory evaluation was conducted to

determine precision estimates for repeatability and

reproducibility of the American Society for Testing

and Materials (ASTM) E 84-77a tunnel test as modified

by the Consumer Product Safety Commission for cellulosic

loose fill insulation. Six laboratories participated

in this study by running tunnel tests on eight cellulosic

loose fill materials. Each laboratory was surveyed

during the project to examine its conformance with the

critical details of the test apparatus and procedure.

The results of the survey showed that none of the

tunnels completely conformed with the specifications

of the modified ASTM E 84-77a standard.

The within-laboratory coefficients of variation

for repeatability for the six fire-retardant treated

cellulosic insulations ranged from 11 to 23 percent

with an average of 16 percent. The between-laboratory

coefficients of variation for reproducibility for the

same materials ranged from 31 to 41 percent with an

average of 35 percent. There would be little assurance

that different laboratories would be able to distinguish

between insulations which do and which do not comply with

the CPSC mandatory level (FSC _< 25) on a consistent basis.

Key words: Cellulosic insulation; flame spread; interlaboratory evaluation; precision; test methods; tunnel

test

1
1. INTRODUCTION

The interim mandatory safety standard for cellulosic home insulation,

which became effective on September 8, 1978 [l]'*', requires that cellulosic

insulation materials meet a prescribed flame spread classification (FSC)

limit according to a specified standard fire test for flame spread. This

test procedure is a Consumer Product Safety Commission (CPSC) modified version

of the current ASTM E 84-77a test for surface burning characteristics of

building materials [2]

.

This report is to provide precision estimates of

2 3 repeatability and reproducibility associated with this fire test. Such

estimates are required for several reasons:

a) To determine the degree of confidence which may be

placed on numerical test results from a given number

of replicate tests from an individual test laboratory.

b) To determine the extent of variability assignable to

test results on "identical" specimens of a given

insulation material tested in any tunnel conforming to

the CPSC specifications.

An inter laboratory test program was conducted to evaluate the CPSC

modified ASTM E 84-77a test procedure.

The purpose of the test procedure is to determine the comparative

burning characteristics of a material by evaluating the flame spread over

its surface when exposed to a standard test fire. The test should provide

a basis for comparing surface burning characteristics of different materials.

'"Numbers in brackets refer to the literature references listed at the

end of this report.

2 Repeatability precision - repeatability or within-laboratory precision is

defined in terms of the variability between test results obtained in the

same laboratory on the same material [3].

3 ... . . . . Reproducibility precision - reproducibility of between-laboratory

precision is defined in terms of variability between test results obtained

in different laboratories on the same material T-TH

2
2. TEST METHOD AND APPARATUS

The test procedure as specified by CPSC requires the use of the ASTM

E 84 tunnel (see figures 1, 2 and 3). CPSC made technical non-substantive

changes to the test method. These modifications were primarily the addition

of tolerances to a number of measurements on the tunnel. The purpose of

these tolerances was to reduce allowable variations in the procedure and

equipment. A list of these changes is presented in appendix A. Also, the

CPSC standard does not require the evaluation of smoke development or fuel

contribution for these materials.

To briefly describe the tunnel test for cellulosic loose fill insulation,

three metal frames 2.53 m (8 ft 3-1/2 in) long and 51 cm (20 in) wide covered

with steel wire screen, wires nominally 0.254 + 0.0254 mm (0.01 + 0.001 in)

in diameter with approximately 1.2 mm (3/64 in) openings, are placed end to

end on the ledges of the test chamber (see figure 4) . In this position the

test frames with the wire mesh become the interior top surface of the tunnel.

A sample of cellulosic loose fill insulation is spread at a relatively uniform

density on the wire screens (see figure 5). The first 35.6 cm (14 in) of the

specimen (that portion upstream of the burner) is covered with a piece of

sheet metal. The specimen length exposed in the tunnel is 7.3 m (24 ft).

The walls and floor of the tunnel are lined with fire brick. The tunnel has

an inside width of 44.5 cm (17.5 in), a height of 30 cm (12 in) and a length

of 7.6 m (25 ft). The tunnel is open at both ends; the "fire" and the "vent"

end. The specimen, in a ceiling position with material supported by and

exposed through the wire screen, is exposed to diffusion flames from two gas

burners extending from the tunnel floor and pointed upward 30 cm (12 in) from

the fire end. A forced draft induced by a blower and controlled by a damper

system at the vent end of the tunnel pulls air through the opening upstream

of the burners in the fire end. A prescribed average air velocity of 7.3

+1.5 m/min (240 + 5 ft/min) is measured at the vent end of the chamber prior

to igniting the exposure flame. After ignition, a constant negative pressure

(draft) is maintained and controlled by the damper system. The flame, which

extends 1.36 m (4.5 ft) from the burner, and draft serve to ignite the specimen

and to induce flame spread along the ceiling of the tunnel. Windows located

on the side of the tunnel allow an observer to record the extent of flame

spread as a function of time over the last 5.9 m (19.5 ft) of the 7.3 m

(24 ft) specimen. The test duration is 10 minutes. The flame spread

classification (FSC) is based on a scale which has 0 for asbestos-cement

board and 100 for a selected grade of red oak flooring. A correction factor

for the wire screen is determined by conducting tests on the red oak flooring

with and without the screen. The FSC for the unscreened flooring divided

3
by the value obtained with the screened flooring gives the screen correction

factor (SCF ) . The FSC calculation takes into consideration the total area

under the flame spread time-distance curve. The value developed from the

area under the curve is then multiplied by the SCF to give the reported

flame spread classification [2] . Fuel contribution and smoke development

are not considered in this modified test procedure.

3. PARTICIPANTS

Five commercial testing laboratories and one private laboratory

participated in this study. Appendix B lists the names of the participants.

Each laboratory possessed a minimum of one year's experience with the tunnel.

Several of the laboratories had experience that exceeded 20 years. However,

few of the participants had more than four months' experience with the modified

test procedure for cellulosic insulation. To maintain the participants'

anonymity as it relates to their test results, the laboratories are assigned

code numbers. In this report, the laboratory test data are identified only

by the participants' code numbers.

4 . LABORATORY SURVEY

Each participating laboratory was visited. Most of the visits were

made before the testing was under way; however, because of time restraints,

two visits were made while testing was in progress. The purpose of the

laboratory survey was to determine the characteristics of the tunnels and

to evaluate each laboratory's use of the test procedure. Table 1 lists the

tunnel characteristics that were measured, and information obtained from the

operators. As shown, the survey included an evaluation of tunnel dimensions,

controls and instrumentation. When items were found to deviate from the

specified value, the laboratories were informed so that changes could be

made. Upon completing the survey it was found that none of the tunnels

conformed completely with the CPSC or ASTM E 84-77a specifications. The

asterisks on table 1 indicate the items that did not conform with the standard. Most of the tunnels did not conform with the standard because the

turbulence bricks were not located where specified. Although it apparently

has not been documented, it is believed that the air flow pattern in the

tunnel is a critical factor in flame spread measurements and is affected by

the placement of the bricks. A second area where the tunnel was often out

of compliance was the placement of the end thermocouple. One laboratory did

not use the prescribed wire size for the wire screen support. (See the

discussion of wire mesh study in section 7.4). Another area of variability

which indicates the possibility of some basic problems in the control of

4
tunnel operating conditions is the wide heating rate range recorded by the

participants. The standard calls for an approximate 5.3 MJ/min (5000 BTU/min)

heating rate for the tunnel burner. With this flow rate and maintaining

other operating parameters such as air velocity, burner design and location,

and tunnel geometry, the flame from the gas burner should extend 1.37 m

+ 152.5 mm (4.5 ft + 6 in) downstream. As shown in table 1, the gas heating

rate ranged from a low of 5.1 MJ/min (4805 BTU/min) to 5.6 MJ/min (5290

BTU/min) . This represents a variation of almost 527 KJ/min (500 BTU/min)

which is approximately 10% of the recommended heating rate. This type of

variation could have a significant influence on the tunnel test results.

One potential problem that was observed which is not directly specified

by the standards, as it relates to running the test, are variations in test

room temperature and humidity. Some of the participating laboratories are

located in cold climates and some are not. While observing tests in progress,

it was noted that a number of tunnel operators were not able or did not

attempt to maintain uniform temperatures and humidity conditions in the test

room. In some cases, it is doubtful that consistent air supply temperature

and humidity were maintained. This variation would result in changing air

velocity in the tunnel. Significant variations were caused primarily by the

opening of outside doors to remove samples from the tunnel test room and to

vent smoke from the building. In one case it was snowing and the building

doors were left open until the tunnel floor temperature was down to the

prescribed 40.5 + 2.8°C (105° + 5°F) . At this time the building doors were

closed, the sample placed in the tunnel, and the test was started. By this

time, the 3.91 m (13 ft) floor thermocouple reading had dropped to 35.6°C

(96°F) . It is known that the moisture content of paper and wood base materials varies with humidity (and temperature) level and is a significant factor

in flame spread measurement.

In one laboratory, the tunnel air velocity was reset four times during

a single day's operation because of changes in barometric pressure as a storm

front approached the area. In other laboratories these adjustments are not

routinely made.

The effects of some of the factors identified in the survey may have

only a minor influence on the test results, but a combination of these

factors may introduce significant differences.

5
5. MATERIALS AND SAMPLE PREPARATION

Six loose fill cellulosic insulation materials currently being sold in

the home insulation market were chosen for the program. All of these materials

are typically installed in home attics and wall cavities by blowing machines.

In addition, two cellulosic materials without fire-retardant chemical

treatments were also chosen to provide a base line for comparative performance. Neither of these products are used as home insulation, but their

visible characteristics are similar to fire-retardant treated cellulosic

insulations. The materials were selected to provide a broad range of physical

and chemical characteristics. Of the fire-retardant treated materials, the

primary component of four materials was ground waste paper. The primary

components for the other two treated materials were cotton fibers and ground

wood chips. The processes for adding fire-retardant chemicals to the materials also varied. The chemicals for three of the waste paper materials were

applied by dry mixing, and chemicals for the remaining waste paper product,

the cotton product and the ground wood product were applied through wet

processes. The primary components of the untreated cellulosic products were

waste paper and ground wood.

Twenty-five bags of each material were obtained from the manufacturer.

Upon receiving each product a code letter was assigned to the material. The

code letters A through H were used for identification. Each material was

then blended using the following procedure. Twenty-five corrugated boxes

containing two large plastic bags each were set out and numbered consecutively.

Two plastic bags were used per sample box because a single bag was not large

enough to hold the quantity required for a single tunnel test. The plastic

bags were used to protect the specimens from moisture during shipment. A bag

of material from group A was selected at random, weighed, and a fraction of

the weight calculated which would produce an equal distribution of the product

to each of the sample boxes. Samples of equal weight were taken from the

material bag starting at the top and progressing to the bottom. The samples

were distributed in consecutive order so that each box being filled received

an equal portion. This procedure was followed until all of the samples from

group A had been distributed. To ensure that each laboratory sample would

represent an average cross section of the group, when the next bag within a product group was sampled the order of the laboratory sample boxes was indexed

by one. This placed the top sample of the second bag from group A in box

number two of the laboratory set and placed the last sample in box number

one. Each material group was prepared using the above procedure.

6
After the samples were mixed the boxes were weighed and the plastic bags

were sealed. The samples were then placed into laboratory groups, lot

numbers were recorded, and the boxes were prepared for shipment. Each box

contained the equivalent sample weight of one manufacturer's bag of insulation. The original bag weights, as obtained from the manufacturer ranged

from 11.4 to 18.2 Kg (25 to 40 lb). A total of 24 boxes of cellulosic

materials were shipped to each participant, providing three boxes, sufficient

for three replicate tests, for each of the eight materials.

6. EXPERIMENTAL DESIGN

6.1

Test Procedure

Each participating laboratory was shipped three samples of eight different

cellulosic materials. A letter of instruction was also sent with a copy of

the test procedure which was published in the August 8, 1978 Federal Register.

The instructions pointed out that technical non-substantive changes had been

made to the ASTM E 84-77a test procedure. The letter also requested that the

laboratories strictly comply with part 1209.4 (c) (9) regarding the attachment

of the wire screen to the red oak flooring and explicit instructions were

given for the procedure for developing the screen correction factor (SCF)

See appendix C which describes the procedure used.

6.2

Laboratory Specimen Preparation

The laboratories were informed that each box, containing two plastic

bags of insulation, represented one sample. It was requested that each

sample of cellulosic material be blended by dumping the two bags of material

into an insulation mixer/blower, mixed for a minimum of two minutes, and then

blown. The material was to be blown into a container and then conditioned

using the procedure specified in the standard.

6.3

Test Density

Since there was a significant difference in the physical properties of

one material as compared to the others, two different test densities were

specified. All specimens except material H were specified to be tested at

40 Kg/m 3 (2.5 lb/ft 3

) density with an allowable range between 38 and 42 Kg/m 3

(2.4 and 2.6 lb/ft 3 ). It was requested that material H be tested at a nominal density of 24 Kg/m 3 (1.5 lb/ft 3

) with an allowable range of 22 to

26 Kg/m 3 (1.4 to 1.6 lb/ft 3 ).

7
6.4 Order of Testing

Two red oak flooring reference tests were conducted first. The standard

select red oak flooring used for calibrating the tunnel was supplied by the

laboratory. One of the tests was conducted with the wire screen attached to

the red oak flooring and one was conducted without the screen. After the

initial tunnel calibration with the red oak, the cellulosic materials were

tested. When all of the cellulosic materials tests were completed, one

additional screen covered red oak test was run. As shown in appendix C, the

screen correction factor was calculated using the screened and unscreened red

oak test results.

7. TEST RESULTS AND DISCUSSION

7.1 Statistical Procedures

Six laboratories participated in the test program. Each laboratory ran

three replicate tests on each of eight materials. The data generated by the

participants were compiled and compared with the requirements of the CPSC

interim safety standard. The standard states that any cellulosic insulation

that is a consumer product must have a flame spread rating of 0 to 25 [1] . Also, the data were statistically analyzed using the methods presented in the

"Tentative Recommended Practice for Conducting an Inter laboratory Test Program

to Determine the Precision of Test Methods" which is being prepared by ASTM

Committee E 11 [3]. Appendix D is a brief presentation of the statistical

methods used in this report.

7.2 Tunnel Test Data

The data as received from the laboratories are presented in table 2.

This table exhibits the data cells 4 which are made up of three replicate

tests on each material. Of the materials tested, D and F were not treated

with fire-retardant chemicals. These products show test results with relatively wide ranges. One data unit located in cell 2 D was not used in the

statistical analysis. The laboratory reported that the test specimen did

not fill the length of the tunnel, and the flames spread to the end of the

specimen

.

Cell - each of p laboratories makes measurements on each of q materials.

This gives rise to p x q "cells". Each cell consists of n replicate

measurements [3].

8
Also shown on table 2 are the results obtained for the select red oak

calibration tests and the screen correction factors (SCF) used for calculating the flame spread classification numbers. The column of red oak

calibration tests shows results for the unscreened and screened samples. The

select red oak tested without the wire screen exhibits an FSC range of 93 to

116 with an average of 102 and a standard deviation of 8.8. The screen

covered red oak used for developing the correction factor has a range from 56

to 77 with an average of 68 and a standard deviation of 6.8. The screen

correction factors ranged from a low of 1.32 to a high of 1.63 with an

average of 1.49 and a standard deviation of 0.11. The data indicate that the

procedure for calibrating the tunnel and developing the screen correction

factor produced relatively uniform results.

Table 3 presents the mean values of each test cell with the materials

ordered from the lowest to highest flame spread classification. The average

flame spread classification for each material is shown at the bottom of the

table. To the right of the cell averages are two columns which show the

laboratory test results compared to the criteria set forth in the CPSC

interim standard. For a material to pass, it must have a FSC £ 25. As can

be seen, the number of passing materials ranged from 0 to 6 . At the extremes,

one laboratory passed all of the materials except the two untreated products,

and two laboratories failed all of the materials. As shown in the table, the

cell averages for materials F and D have a wide range. It is believed that

part of the variation is the result of materials' non-uniformity, even though

major efforts were made to blend materials from different bags. Part of the

variation may also be due to environmental variables (humidity, temperature)

which would be expected to be particularly sensitive for untreated cellulose.

Table 4 presents the cell standard deviations for each cellulosic

material and laboratory. The pooled standard deviations are shown at the

bottom of the table.

The precision estimates for the fire-retardant cellulosic materials

flame spread classifications are given in table 5. For each material the

table gives the average FSC and the coefficients of variation calculated

for repeatability and reproducibility. The precision estimates for materials

F and D which were not fire-retardant treated, are not included because the

test was not under control for these materials as can be seen by the cell

standard deviations in table 4.

9
Looking at fire-retardant treated materials, it is apparent that a significant degree of variation exists. The range for the repeatability

coefficient of variation is 11 to 23 with an average of 16. The reproducibility coefficient of variation ranged from 31 to 41 and exhibits an average of 35.

7.3 Comparison of Fire Test Methods

The author compared the precision of three test methods in a recent

study involving the attic floor radiant panel [4]

.

The comparisons were

made using data obtained from a report by Lee and Huggett concerning the

ASTM E 84-70 tunnel test [5]

,

results from a report by Benjamin and Adams

involving the flooring radiant panel test [6]

,

and data obtained from the

attic floor radiant panel study on thermal insulation [4]

.

The conclusion

from this comparison was that the attic floor radiant panel test precision

was reasonable when compared to other fire test methods. To carry this

comparison one step further, the precision of the data obtained from this

study on the fire-retardant treated materials is compared with the precision

of the other test methods (see table 6) . Table 6 indicates that the CPSC

modified ASTM E 84-77a test has a notably higher reproducibility coefficient

of variation when compared to the other test methods. The results when

compared with the attic floor radiant panel test show that the median

coefficient of variation for reproducibility of the modified ASTM E 84-77a

test method is 67% higher. It is also 30% greater than the median reproducibility coefficient of variation obtained with the ASTM E 84-70 test with

carpet. Some of this variability as compared to the carpet materials can

be attributed to the known random characteristics of the cellulosic

materials

.

7.4 Variability

Through test observations and data analysis, sources of variability

that could influence the test results have been identified. The most

significant variable influencing test results appears to be the two joints

between the wire screen specimen frames. These joints are located at

approximately 2.53 m (8 ft 3-1/2 in) and 5.06 m (16 ft 7 in) as measured

along the tunnel length from the fire end of the test chamber. Five

laboratories reported the flame spread distance during the test, and the

observed char distance and presence of flaming after the test. Out of 120

tests, 57% indicated that these phenomena occurred within 30 cm (1 ft) of

the test frame joint. Figure 4 shows a picture of the test frames with the

screen wire joints open and sagging. Figure 6 shows examples of charring

10
and flaming observed by laboratories after the tests were completed. In

one case a laboratory reported that the screen joint appeared to interfere

with the flame travel. Observation of the joints showed that the wire screen

was generally loose and sagging after conducting two or three tests. One

laboratory recognized this problem before starting the test program and

reported bridging the test frame gaps with small pieces of wire screen. The

test results from this laboratory showed the least variations associated with

the test frame joints. Most of the laboratories used the same test frames

throughout the entire program. Another problem also associated with the wire

screen is its tendency to develop deep and random sags which alter the air

flow patterns and localized radiation characteristics in the tunnel. Some

sags in the wire screen were measured to be 3.8 cm (1.5 in) deep (below the

normal plane of the specimen surface) and 25.4 cm (10 in) along the tunnel

lengths

.

Laboratory 3 attempted to avoid wire sag by using a stainless steel wire

screen with a wire diameter of 0.508 mm (0.020 in). This screen does not

meet the specifications but reduced the extent of sagging. A limited study

was conducted to ascertain the effect on the FSC. Two sets of identical

cellulosic insulation specimens selected consecutively from a manufacturer's

production line were tested. The bags of insulation were randomized and

shipped to the laboratory. The laboratory followed the test procedure as specified in the interlaboratory program except that one set of three specimens was tested with the large diameter stainless steel screen wire and the

other tested using galvanized steel screen as specified in the standard (see

table 7) . As shown in the table, the large diameter stainless steel wire

screen produced slightly lower but more uniform flame spread classification

values than that obtained from the standard galvanized screen. At the

completion of testing, it was noted that the galvanized screen wire had

developed numerous irregularities while the stainless steel remained relatively flat and straight. This limited study supports the conclusion that

wire screen sag increases test variability.

8. SUMMARY AND CONCLUSIONS

Six laboratories participated in an interlaboratory test program

designed to determine the repeatability and reproducibility of the CPSC

modified ASTM E 84-77a test procedure for cellulosic insulation as published

in the August 8, 1978 Federal Register. Eight loose fill cellulosic materials

were tested. For the six fire-retardant treated insulations the withinlaboratory coefficients of variation for repeatability ranged from 11 to 23

percent with an average of 16 percent, and the between-laboratory coefficient

11
of variation for reproducibility ranged from 31 to 41 percent with an average

of 35 percent. There would be little assurance that different laboratories

would be able to distinguish between insulations which do and which do not

comply with the CPSC mandatory level (FSC <_ 25) on a consistent basis. Part

of the variability may be attributed to variability in the cellulose insulation

material, including dispersion of the chemical fire retardant, and part can be

attributed to problems with the wire screen specimen frames, such as sagging

and irregular joints. Also, laboratory procedures for maintaining test room

temperature, humidity, and exposure flame gas flow rates may have contributed

to the variability. The coefficients of variation were significantly higher

than those for the attic floor radiant panel.

9 . ACKNOWLEDGEMENTS

Appreciation is extended to the cellulosic insulation manufacturers who

provided material for the test program. Mr. Bernard Schwartz of the Consumer

Product Safety Commission and the field offices assisted in obtaining the

materials and arranging for their delivery to NBS . Mrs. Mary G. Natrella,

Statistical Engineering Division, National Bureau of Standards, provided

statistical consultation and Mr. Sanford Davis, Furnishings Flammability

Research, National Bureau of Standards, provided assistance throughout the

project. Messrs. Dennis Sullivan, Lee Dunlap, and Tom Prather of the Center

for Fire Research, National Bureau of Standards, prepared the test specimens

used in this project.

12
10. REFERENCES

[1] Consumer Product Safety Commission/ Interim Safety Standard for

Cellulose Insulation Part 1209, Federal Register, Vol. 43, No. 153,

August 8, 1978.

[2] Standard Test Method for Surface Burning Characteristics of Building

Materials, ASTM E 84-77a, American Society for Testing and Materials,

Philadelphia, Pa. (1978)

.

[3] Tentative Recommended Practice for Conducting an Inter laboratory

Test Program to Determine the Precision of Test Methods, ASTM

Committee E 11, American Society for Testing and Materials,

Philadelphia, Pa. (1978).

[4] Lawson, J. R. , Interlaboratory evaluation of the attic floor radiant

panel test and smoldering combustion test for cellulose thermal

insulation, Nat. Bur. Stand. (U.S.), NBSIR 79-1588 (February 1979).

[5] Lee, T. C. and Huggett, C., Interlaboratory Evaluation of ASTM

E 84-70, Tunnel Test Applied to Floor Coverings, Journal of Testing

and Evaluation, Vol. 3, No. 1, American Society for Testing and

Materials, Philadelphia, Pa. (1975).

[6] 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)

.

13
Table 1. Characteristics of the ASTM E 84-77a tunnels

Characteristic Standard 1 2 Laboratories

3 4 5 6

Tunnel

Air inlet slit height,

(in) 3 + 1/16 3 3 3 3 1/16 3 2 15/16

Slit to center line of burner (in) 54 + 5 57 1/2 56 54 3/4 52 1/4 52 50 5/8

Overall tunnel length

(ft, in) 25 + 3 25-1/2 25-1/2 25-1 5/8 25 25 25-1 1/2

Number of turbulence bricks 6 6 6 6 6 6 6

Location of bricks frcm 7 + 0.5 6.50 3.25* 7.50 6.42* 6.50 4.67* center line of burner 12 + 0.5 11.67 8.33* 12.50 11.50 11.50 7.29*

(ft ) windcw side 20 + 0.5 19.33* 14.25* 19.67 20.42 19.08* 14.04* Location of bricks frcm 4.5 + 0.5 4.50 5.50* 4.50 4.58 4.58 9.67* center line of burner 9.5 + 0.5 9.67 10.75* 9.50 9.58 9.83 11.88*

(ft ) back side 16.5 + 0.5 16.08 18.67* 16.17 15.67* 15.58* 18.00* Depth of tunnel floor,

(in) 12 + 0.5 11..50-11.75 12.25-12.50 12 12 11.75-12 11.75-12

Draft Control

Draft control auto/man auto auto auto auto auto auto auto

Manometer location frcm 21 minimum 21-6 25-10 21 25-10 23 22-8

(ft , in)

Typical manometer value,

(in H2 0) N/A 0.085 0.065 0.078 0.07 0.076 0.05-0.1

Air Velocity

Air velocity with lab anemometer, (ft/min) 240 + 5 237 240 240 237 242 238

Type of anemometer thermal HW HW K

V

HW HW K

V

Air temperature at measurement (°F)

anemometer

73.4 + 5°F 70 70 70 70 70 70

Temperature

Burner center line to centerlined thermo- couple (ft, in) 13 + 1/2 13-1* 13 13 13-1* 13-1/2 13

Burner center line to end thermocouple

(ft, in) 23 + 1/2 23-1* 23-4 * 23-3/4 * 23 23-1/2 22-11 1/2

Thermocouple post O.D.,

(in) N/A 1/4 3/8 5/16 11/16 11/16 1 5/32

Unshielded length of

thermocouple (in) 3/8 + 1/8 1/2 5/16 3/16* 1/4 1/4 1/4

Height of thermocouple

junction frcm tunnel top (in) 1 + 1/32 1 7/8* 3/4* 1 1 1/16* 7/8*

Junction type straight/

twisted OPT. S S S S S S

Type of thermocouple N/A CA CA CA CA CA CA

Ga. of thermocouple No. 18 AWG 18 18 18 18 18 18

Fuel

Gas type City or CG CG CG BM BM CG

Heating rate (Btu/min)

bottled

'v 5000 Btu/min 4870 4970 5290 4805 4835 4955

Type of preheat OPT CG

» CG CG CG CG CG

14
Table 1 (Continued)

Laboratories

Characteristic Standard l 2 3 4 5 6

Wire Screen

Type of metal steel GS SS SS GS GS GS

Mesh opening (in) ^ 0.0469 0.0591+ 0.0591+ 0.0534+ 0.0591+ 0.0591+ 0.0618+

Wire size (in) 0.01 + 0.001 0.009 0.020* 0.009 0.011 0.011 0.01

Miscellaneous

Smoke meter frcm end of tunnel (ft ) 16 to 40 22.5 34.7 28.9 39.7 31 27.9

Duct insulated yes/no y Y Y Y Y Y Y

Leakage test conducted

(no. /year) 6 SB 2 SB As needed 12 SB 12 SB 2 SB

‘These characteristics do not meet the standards specified in the ASM E 84-77a standard. tMeasurements made by microscopic means.

BM = Bottled methane CA = Chrcmel-alumel OG = City gas GS = Galvanized steel HW = Hot wire anenoneter RV = Rotating vane anemoneter SS = Stainless steel SB = Smoke bonta

15
Table 2. Tunnel test data, flame spread classifications (FSC)

Lab Material

Select Screen

Red Correction

A B C D* E F* G H Oak Factor

1 30.6 35.3 31.2 116.6 38.9 144.4 34.0 27.2 97.7

27.0 34.0 31.0 95.8 35.0 149.9 35.5 31.1 97.5 1.44

30.9 35.5 35.1 111.0 50.8 89.3 63.1 27.3 (s) 67.1

(s) 68.7

2 16.6 10.7 12.9 162.0 20.6 60.1 19.9 15.0 103.0

12.8 12.7 15.0 56.7 8.0 50.0 16.2 8.2 (s) 68.5 1.566

4.3 13.3 12.2 61.4 16.2 53.9 8.1 12.3 (s) 59.3

3 17 36 28 75 32 70 32 25 94 21 36 32 87 36 70 32 25 (s) 74 . 1.32

21 29 28 71+ 32 67 32 21 (s) 69

4 28.5 40.9 36.8 95.5 32.8 77.4 36.7 24.5 105.55

28.5 36.7 32.7 85.0 28.6 77.2 32.7 24.4 (s) 71.36 1.475

28.6 28.6 32.7 84.8 32.6 81.0 32.7 28.5 (s) 72.00

5 20.6 41.6 37.6 148.1 33.2 87.4 41.6 29.0 116.26

20.9 41.7 25.1 97.0 29.2 87.0 37.5 29.1 (s) 75.36 1.52

25.0 46.0 29.3 87.3 29.0 87.4 37.3 29.2 (s) 77.3

6 8 26 31 108 23 210 36 18 92.8

10 31 18 181 26 408 26 13 (s) 56.3 1.63

18 28 23 271 26 96 36 13 (s) 57.6

* Cellulosic materials that were not treated with fire-retardant chemicals.

t This value was not used in the analysis. It was reported that the material did not extend the full length of the tunnel and the flames spread to the end of the specimen.

(s) Red oak flooring tested with wire screen.

16
Table 3. E 84 Tunnel Test cell averages ordered from lowest

to highest flame spread classification (FSC)

Lab Material A H C E B G F* D* Pass Fail

1 29.5 28.5 32.4 41.6 34.9 44.2 127.9 107.8 0 8

2 11.2 10.8 13.4 14.9 12.2 14.7 54.7 93.4 6 2

3 19.7 23.7 29.0 33.0 33.7 32.0 69.0 81.0 2 6

4 28.5 25.8 34.1 31.3 35.4 34.0 78.5 88.4 0 8

5 22.2 29.1 30.7 30.5 43.1 38.8 87.3 110.8 1 7

6 12.0 14.7 24.0 25.0 28.3 32.7 238.0 186.7 4 4 Column

Average 20.5 22.1 27.3 29.4 31.3 32.7 109.2 111.4

* Cellulosic materials that were not treated with fire-retardant chemicals.

Table 4. E 84 Tunnel Test results cell standard deviations ordered

lowest to highest flame spread classification (FSC)

Lab Material

A H C E— —B G F* D*

L , — H —

1 2.17 2.22 2.31 8.23 0.81 16.39 33.51 10.66

2 6.30 5.06 1.46 6.40 1.36 6.04 5.09 58.48

3 2.31 2.31 2.31 2.31 4.04 0.00 1.73 8.48

4 0.58 2.34 2.38 2.37 6.25 2.31 2.14 6.12

5 2.46 0.10 6.36 2.37 2.51 2.43 0.23 32.66

6 5.29 2.89 6.56 1.73 2.52 5.77 157.87 81.65

Pooled

Standard

Deviation 3.74 2.88 4.12 4.62 3.43 7.63

* Cellulosic materials that were not treated with fire-retardant chemicals. The wide

range of cell standard deviations suggests that the test was out of control with these

materials which makes it inappropriate to include pooled standard deviations.

17
Table 5. Precision estimates of flame spread classifications (FSC)

Treated

Material

Overall

Laboratory

Average

Repeatability

Standard

Deviation

Repeatability

Coefficient

of Variation

Reproducibility

Standard

Deviation

Reproducibility

Coefficient

of Variation

A 20.5 3.74 18.24 8.41 41.00

H 22.1 2.88 13.03 7.95 35.99

C 27.3 4.12 15.09 8.34 30.57

E 29.4 4.62 15.71 9.67 32.90 B 31.3 3.43 10.96 10.83 34.64

G 32.7 7.63 23.33 11.74 35.88

Average 16.06 35.16

Table 6. Comparison of precision estimates for fire test methods

Repeatability Reproducibility

Test Coefficient of Variation Coefficient of Variation

Method Material Range Median Range Medi,

CPSC Modified

ASTM E 84-77a

Fire-Retardant Treated

Loose Fill Cellulose

11 to 23 15 31 to 41 35

ASTM E 84-70 Carpet 4 to 27 8 7 to 43 27 Attic Floor

Radiant Panel Loose Fill Cellulose 8 to 15 12 13 to 30 21

Flooring

Radiant Panel

Carpet 8 to 19 11 7 to 16 10

Table 7. Screen wire comparison using the modified

ASTM E 84-77a test procedure

0.254 mm (0.01 in)

Galvanized Screen

Wire

(FSC)

16.06

21.14

17.00

Average 18.07 + 2.70

0.508 mm (0.020 in)

Stainless Steel Screen

Wire

(FSC)

16.11

15.89

16.11

Average 16.04 + 0.13

18
19

Figure

1.

Example

of

E

84-77a

tunnel

used

in

the

interlaboratory

program
C-2

® I go

20

Figure

2.

Details

of

the

E

84-77a

tunnel
ASBESTOS

CEMENT

BOARD

CO

PQ

CQ

-P

(0

0)cG3

4-> mOGO

•Hpo

<Dw

U5tnouu

0)p3

tji •H

Pm

21

CASTABLE

REFRACTORY

(MAX

TEMP

1370°C/2500°F)
t 4

V

Figure 4. Screen wire test frames in place on tunnel ledges

22
Figure 5. Screen test frames filled with cellulosic

insulation before testing

23

WmW
24

Note:

Sketches

shew

screen

wire

test

frames

as

arranged

in

the

tunnel.

Three

frames

located

end

to

and

cover

the

tunnel

length.
APPENDIX A

Technical Non-substantive Changes Made to the

ASTM E 84-77a Standard by CPSC

The Commission made these changes in order to:

(A) Ease some of the restrictive specifications for the test apparatus

and test procedure,

(B) Simplify the test procedures,

(C) Eliminate provisions in the requirements that are unrelated to

cellulosic insulation, and

(D) Increase the likelihood that consistent test results will be

obtained

Changes

1. Added the following tolerances:

+ 1/16 inch to describe thickness of asbestos fabric gasket tape.

+ 3 inches to describe the fire test chamber length.

Replaced a nominal 2 inches with a tolerance 3+1 inch to describe

the insulation for the top of the tunnel.

+ 1 inch to describe the spacing of burners.

+ 1/4 inch to describe the diameter of the vent end flue pipe.

+ 1/16 inch to describe the depth of the embedded thermocouple.

- 0

+ 1/32 inch to describe the asbestos cement board thickness.

+ 1 inch to describe the distance from burner ports for recording

the air velocity.

+ 6 inches to describe the distance the test flame must extend

downstream.

+ 6 inches to describe the distance intervals for making observations

in calibration tests.

+ 1/4 inch and + 1/16 inch to describe the test frame supporting

the specimen holder.

+ 2 seconds to describe the duration of the test.

2. Added (or deleted) the following statements for clarity:

Provision that allows operators to use draft gage tap inserted

through top of tunnel fire end.

Added "nominal" to dimensions for steel test frame steel angles.

Added word "nominal" to describe pipe elbow at burner outlet.

A-l
APPENDIX A (Continued)

An alternate air velocity reading range used for draft gage taps in

top of tunnel fire end.

Corrected two typographical errors in the ASTM standard.

(a) Air velocity changed from "7.32" to "73.2" m/min.

(b) Red oak flooring thickness changed from "23/32 inch" to

"25/32 inch."

Changed description of screen wire from "galvanized steel" to

"steel" to allow stainless steel screen.

Loose fill insulation shall be placed on steel screening with wires

normally 0.01 + 0.001 in (0.254 mm + 0.0254 mm) in diameter with

approximate 3/64 in (1.2 mm) openings.

Steel screen correction factor (SCF)

A provision to allow the Commission to determine the density of

cellulose insulation for test if manufacturers do not specify.

Deleted terms "delamination" and "shrinkage" as observed burning

characteristics

Deleted paragraph 8.1 providing for analysis of products of combustion.

A-2
APPENDIX B

Participants

Factory Mutual Research Corporation

Norwood, Massachusetts

Hardwood Plywood Manufacturers Association

Arlington, Virginia

Southwest Research Institute

San Antonio, Texas

Underwriters' Laboratories, Inc.

Northbrook, Illinois

Underwriters' Laboratories, Inc.

Santa Clara, California

Warnock Hersey Professional Services Ltd.

Vancouver B.C., Canada

B-l
'

-
APPENDIX C

Calculation of Screen Correction Factor

1. Determine the FSC of the select red oak without the screen using

the method specified in ASTM E 84-77a sections 5, 6 and 7.

2. Determine the FSC of the select red oak with the screen using the

same method. Two (2) tests with the screen were conducted, one (1)

before insulation is tested and one (1) after.

3. Take the average of the FSC with the screen.

4. Divide the FSC of the red oak without the screen (step 1) by the

average of the values with the screen (step 3)

.

Example ;

\ value without the screen 9!5 _ ^ average of values with the screen 65

Note

:

FSC - Flame spread classification

SCF - Screen correction factor

C-l
, , .

. . . ; o j

.

•

’

r.

'

' .

'

|

•
APPENDIX D

STATISTICAL METHODS

(cv

r

)

(CV

d. . i: n . . 1 D

s . . id

< SL>j

' sr>j

(S R»j

( S _)

X j

X . ID

X . D

Nomenclature

Coefficient of variation for repeatability (within-laboratory)

Coefficient of variation for reproducibility (betweenlaboratories)

Cell deviations from average

Number of replicates per cell

Total number of laboratories

Cell standard deviation

Component of variance between laboratories

Pooled standard deviation for repeatability

Standard deviation for reproducibility

Intermediate variance quantity

Average for cell (i,j) where i represents the laboratory

and j the material

Average for jt*1 material for all laboratories

D-l
( 1 )

Pooled Standard Deviation for Repeatability for the . th

D material

:

;s )

. r j

Z .l

Equation (1) is applicable only when the number of replicates is the same for

each laboratory for a given material. Where there are missing replicates

in one or more laboratories use equation (la)

.

(s )

. =

r 3 V

Z . (n. .-1) s^ . 1 *3

Z. (n. .-1)

x 1J

(la)

Coefficient of Variation for Repeatability:

(CV ) = 100

r

Standard Deviation for Reproducibility:

First calculate the "deviations from average" for each cell (i,j)

:

( 2 )

d . . = x . . - x . 11 ID D (3)

Then calculate the intermediate standard deviation quantity where:

(s_)

X j

z

.

(a. .

)

i ij

P-1

(4)

Using (s_) and (s r

)

.

calculate the "component of variance" between laboratories,

x j

-1 where

:

‘"L’j V

(s _r

x j

(s ) 2

. r j n

(5)

i. t The variance of the total variability of a single test result on the j

material including both within and between laboratory variability is given by:
Coefficient of Variation for Reproducibility for the j material:

(CVR) j = 100 ( 7 )

D"3
NBi-1 1 -tA (REV. *-781

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 79-19222. Gov't Accession No. 3. Recipient's AcomloftNo.

||| ,/j§l

4. TITLE AND SUBTITLE

AN INTERLABORATORY EVALUATION OF THE ASTM E 84-77a

TUNNEL TEST MODIFIED BY THE CONSUMER PRODUCT SAFETY

COMMISSION FOR CELLULOSIC LOOSE FILL INSULATION

5. Publication Date November 1979

7. AUTHOR(S)

J. Randall Lawson

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

10. Project/Task/Work Unit No.

. , \ - I

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (street, City, state, zip)

U.S. Consumer Product Safety Commission

Textile and Mechanical Engineering Group

Bethesda, Maryland 20202

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

I | Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or leas factual aummary of moat significant information. If document includes a significant bibliography or

literature survey, mention it here.) An interlaboratory evaluation was conducted to determine precision

estimates for repeatability and reproducibility of the American Society

for Testing and Materials (ASTM) E 84-77a tunnel test as modified by the

Consumer Product Safety Commission for cellulosic loose fill insulation.

Six laboratories participated in this study by running tunnel tests on eight cellulosic loose fill materials. Each laboratory was surveyed during

the project to examine its conformance with the critical details of the

test apparatus and procedure. The results of the survey showed that none

of the tunnels completely conformed with the specifications of the modified

ASTM E 84-7 7a standard.

i The within-laboratory coefficients of variation for repeatability for

the six fire-retardant treated cellulosic insulations ranged from 11 to 23

percent with an average of 16 percent. The between-laboratory coefficients

of variation for reproducibility for the same materials ranged from 31 to 41

percent with an average of 35 percent. There would be little assurance that

different laboratories would be able to distinguish between insulations which

do and which do not comply with the CPSC mandatory level (FSC <_ 25) on a consistent basis.

17. KEY WORDS (aix to twelve entries ; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

asperated by aemicolona)

Cellulosic insulation; flame spread; inter laboratory evaluation; precision;

test methods; tunnel test.

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