NBSIR 80-2186

Combustion of Mattresses

Exposed to Flaming Ignition

Sources Part II. Bench-Scale

Tests and Recommended Standard

Test

Center for Fire Research

National Engineering Laboratory

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

October 1980

Final Report

Issued February 1 981

Sponsored in part by

sumer Product Safety Commission

apartment of Health and Human Services

c i 2
*
NATIONAL BUEIAU or BTAWttARDt UMI«tr

APR 7 193'

NBSIR 80-2186

I I 9 COMBUSTION OF MATTRESSES

EXPOSED TO FLAMING IGNITION

SOURCES PART II. BENCH-SCALE

TESTS AND RECOMMENDED STANDARD

TEST

Vytenis Babrauskas

Center for Fire Research

National Engineering Laboratory

U S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

October 1980

Final Report

Issued February 1981

Sponsored in part by

Consumer Product Safety Commission

Department of Health and Human Services

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director
. X -.1 ' . 1 / to

:'Sri
TABLE OF CONTENTS

Page

LIST OF TABLES iv

LIST OF FIGURES v

ABSTRACT 1

1. INTRODUCTION x

2. DESCRIPTION OF TEST MATTRESSES 2

3. FULL-SCALE EVALUATION 5

4. BENCH-SCALE TEST PROGRAM 6

4.1 Rate of Heat Release Tests in NBS-II Calorimeter 7 4.2 Rate of Heat Release Tests in Modified OSU Calorimeter 9 4.3 Smoke Density Tests 22 4.4 Heats of Combustion and Fuel Loads 26

4.5 Flame Spread and Ease of Ignition 26

5. ANALYSIS OF FINDINGS 17

6 . CRITERIA FOR PREDICTING FULL-SCALE BEHAVIOR 19

7. HAZARD FACTORS ASSOCIATED WITH USAGE CONDITIONS 20

7.1 Arson and Accelerants 2 q 7.2 Storage and Orientation Effects 2 q 7.3 Fuel Area Effects 2 2

8 . CONCLUSIONS 21

ACKNOWLEDGEMENTS 22 REFERENCES 23

APPENDIX A - Proposed Test Method for Institutional Mattress Flammability ... ^

APPENDIX B - Supplemental Data on Heat and Mass Flows in Full-Scale Tests ... B 2

iii
LIST OF TABLES

Page

Table 1. Mattress Sizes and Weights 25

Table 2. Physical Properties of Mattresses 26

Table 3. Properties of Bedding 28

Table 4. Full-Scale Evaluation Results 29

Table 5. Rate of Heat Release Measurements in NBS-II Calorimeter 30

Table 6. Effect of Specimen Size on Heat Release 31

Table 7. Comparative Rates of Heat Release 31

Table 8. Smoke Results 32

Table 9. Mattress Total Fuel 33

Table 10. Typical Heats of Combustion for Mattress Materials 34

Table 11. Effective Heats of Combustion and Mass Loss 35

Table 12. Summary Performance Groups 36

iv
LIST OF FIGURES

Page

Figure 1. Plan View of Full-Scale Test Room A 37

Figure 2. Elevation of Full-Scale Test Room A 38

Figure 3. Typical NBS-II Calorimeter Results 39

Figure 4. View of Smoke Density Chamber With Horizontal Holder Arrangement ... 40

Figure 5. Typical Curve for a Mattress Specimen 41

Figure 6. Specific Extinction Area Measurements for Specimen M05 42

Figure 7. Predictability of Ignition Times From Calorimeter Data 43

Figure 8. Relationship Between Peak Temperature and Peak Floor Flux 44

Figure 9. Relationship Between Peak C02 Concentration and Peak Floor Flux .... 45

Figure 10. Relationship Between Peak CO Concentration and Peak Floor Flux .... 46

Figure 11. Relationship Between Time to Peak RHR and Peak Floor Flux 47

Figure 12. Rate of Heat Release Performance, NBS-II Calorimeter 48

Figure 13. Rate of Heat Release Performance, OSU Calorimeter 49

Figure 14. Comparison of NBS-II and OSU Results 50

Figure 15. Smoke Performance (RHR data from NBS-II Calorimeter) 51

Figure 16. Smoke Performance (RHR data from OSU Calorimeter) 52

Figure Al. Details of Horizontal Specimen Holder and Load Cell for the

Smoke Density Chamber All

Figure Bl. Heat Release Rate and Mass Flow for Control Mattress B3

Figure B2. Heat Release Rate and Mass Flow for Mattress M01 B4

Figure B3. Heat Release Rate and Mass Flow for Mattress M02 B5

Figure B4. Heat Release Rate and Mass Flow for Mattress M03 B6

Figure B5. Heat Release Rate and Mass Flow for Mattress M04 B7

Figure B6. Heat Release Rate and Mass Flow for Mattress M05 B8

Figure B7. Heat Release Rate and Mass Flow for Mattress M06 B9

Figure B8. Heat Release Rate and Mass Flow for Mattress M07 BIO

Figure B9. Heat Release Rate and Mass Flow for Mattress M08 Bll

Figure BIO. Heat Release Rate and Mass Flow for Mattress M09 B12

Figure Bll. Heat Release Rate and Mass Flow for Mattress M10 B13

v

COMBUSTION OF MATTRESSES EXPOSED TO

FLAMING IGNITION SOURCES

PART II. BENCH-SCALE TESTS AND RECOMMENDED STANDARD TEST

Vytenis Babrauskas

Abstract

Ten mattress types were subjected to full-scale fire tests in the earlier

part of this project. Burning behavior was determined and hazard was assessed

by classifying into performance groups. In the present study bench-scale

test procedures were examined for suitability for classifying mattress com- bustion behavior when exposed to flaming ignition sources. Several tests were

examined, and a test protocol was developed based on two procedures —

measurement of rate of heat release and smoke production. These procedures

enable the performance classifications, as established by full-scale tests, to be reproduced by convenient laboratory tests. Details are given for conducting

the required tests and illustrative performance of some two dozen samples is

recorded.

Key words: Bedding; beds; compartment fires; fire tests; health care facilities; heat release rate; hospitals; mattresses; prisons; smoke production.

1 . INTRODUCTION

In mid-1976 work was started at the National Bureau of Standards (NBS) to characterize

the combustion of institutional mattresses when exposed to flaming ignition sources. The

initial report [1] was issued in 1977 as Part I and gave the results of the full-scale fire

tests and hazard analysis. Ten different mattress types were furnished with identical

hospital bedding (see Figure 1 and Table 1) and ignited from a small polyethylene wastebasket

filled with trash. The bedding acted as a continued flaming ignition propagator. All of the

mattresses passed the mandatory federal cigarette ignition standard [2], but showed substantially varying behaviors in these flaming ignition tests.

This work provided users with a certain amount of guidance, based on behavior simulations for different mattress construction types. Officials of hospitals, prisons, and

similar institutions, however, should have available to them a method for testing and

rating mattresses which is performance-based (rather than a prescriptive specification) and

which can be readily performed by independent testing laboratories. On the face of it, it

would seem that a suitable recommendation would be to use the same full-scale test procedure

as was defined in Part I [1]* This would not be satisfactory for the following two reasons:

(1) the costs of full-scale room tests tend to be very high, making such tests economically

1
a last resort option; (2) interlaboratory data agreement for full-scale room fire tests has been extraordinarily difficult to achieve, making the data gathered for such tests unsuitable for regulatory use. It is then preferable, if at all possible, to adopt a benchscale test procedure. Bench-scale fire tests by themselves are not meaningful for hazard

analysis unless a satisfactory correlation is available between bench-scale test performance

and well-controlled full-scale tests, in which case a sound basis for the utilization of such tests is provided.

The full-scale tests of Part I will be viewed as a proper data base against which to judge bench-scale procedures. The goal of the work in Part II was then to produce a set of

simple, reproducible, moderate cost bench-scale test procedures which would give results that

adequately correlated to the full-scale findings.

2. DESCRIPTION OF TEST MATTRESSES

A description of the ten mattresses tested in full-scale was given in Part I. An additional fifteen specimens were added for the bench-scale series. For convenience, a brief description of all 25 mattresses follows. Their physical properties are listed in

Tables 1 and 2

.

Mattress M01 was a hospital mattress with solid foam core and retardant treated polyvinylchloride (PVC) ticking (the ticking is the outermost mattresses layer, or cover). The

polyurethane core consisted of an inner layer and an outer enveloping layer. The inner core

foam was retardant treated. The outer core material showed only trace retardants, not at an effective level.

Mattress M02 was a hospital mattress with an innerspring construction and contained unretarded

polyurethane foam padding, an unretarded polypropylene interfacing fabric, and a ticking

identical to that of Mattress M01.

Mattress M03 was an innerspring hospital mattress with cotton felt padding, an interfacing

fabric same as in Mattress M02 and a vinyl ticking identical to that in Mattresses M01 and

M02. The cotton padding was retardant treated.

Mattress M04 used a latex foam core (untreated) and a retardant treated vinyl cover. The

foam was "pinned" by a regular pattern of holes. This mattress duplicated the mattress used

in an Osceola, Missouri, nursing home and which was identified as the principal fuel in a multiple-life loss fire in 1974.

2
Mattress M05 was a commonly available commercial mattress with a solid foam polyurethane

core. The ticking was composed of three layers — two rayon fabric layers with an intermediate layer of polyurethane foam. The mattress was asymmetrical in that the ticking

assembly on top was quilted while on the bottom it was not. None of the materials were

retardant treated.

Mattress MQ6 superficially resembled a cotton inner spring mattress in construction and

appearance, but the padding consisted to two layers: a cotton/polyester felt pad and an underpad comprised of cotton, nylon, and polyester fibers. A polyester ticking was used.

Only the underpad was retardant treated. (Note that by comparison, an unretarded cotton

batting mattress of conventional construction normally cannot pass the cigarette ignition

test. Mattress M06, of course, successfully passed the cigarette ignition test).

Mattress M07 was a prison mattress conforming to State of Connecticut Specification 3748-M-339

for mattresses. This specification was issued by the State in 1976 after several fires

occurred, involving two fatalities. The mattress was of innerspring construction, using boric

acid treated cotton felt batting and a jute pad and covered with a retardant treated cotton

ticking conforming Federal Specification CCC-C-436 (Type II).

Mattress M08 was a mattress conforming to U. S v Navy Specification MIL-M-18351, Type III,

size 2. Core material was neoprene (polychloroprene) foam and conformed to Specification

MIL-R-20092. The above specification references Standard MIL-STD-1623 which is based on the

ASTM E162 radiant panel test. The specified neoprene material is "Type II, Class 4," which

requires a flame spread index not greater than 10 on the radiant panel test. The ticking was

a retardant treated cotton fabric conforming to Federal Specifications CCC-C-436. The core consisted of three layers of black neoprene foam of different thicknesses and slightly

different densities glued together.

Mattress M09 was a prison mattress which was tested because of implication in a recent prison

fire. It was comprised of a polyurethane core and vinyl ticking with nylon fabric reinforcement. Only the ticking was retardant treated.

Mattress M10 was a prison mattress of current manufacture which used a black neoprene foam

similar to the one in M08 and was retardant treated. A vinyl ticking with nylon fabric

reinforcement was used.

Neoprene core material in all the test mattresses was retardant treated and could meet this

requirement

.

3
Mattress Mil was a used specimen removed from U. S. Coast Guard shipboard service. The

mattress consisted of a black neoprene foam core covered with a retardant-treated cotton

ticking.

Mattress M12 was considered by the U. S. Coast Guard for shipboard service. The specimen

consisted of a buff neoprene foam core covered with a ticking similar to Mil.

Mattress M13 was a stock U. S. Coast Guard item. Construction and the ticking were similar

to M12; the core material was, however, a black neoprene foam.

Mattress M14 was a prison mattress using a recently developed retardant treated polyurethane

foam. A vinyl ticking was used.

Mattress M15 was a pre-production sample of a newly developed mattress using a highly treated

and filled hydrophilic polyurethane foam. A vinyl ticking was used.

Mattress M16 was identical to Mattress M14 with the exception of the ticking, which was cotton cloth.

Mattress M17 represented a common commercial mattress construction. It was basically of

innerspring cotton batting type, but contained two layers of polyurethane foam underneath the

ticking. This use of polyurethane foam as an interliner permits the mattress to pass the

cigarette ignition test without need for retardant treated cotton batting.

Mattress M18 was a polychloroprene foam core prison mattress, similar to M08. The foam,

however, was buff-colored and was more highly retardant treated than that in M08.

Mattress M19 was a all-polyester batting innerspring unit with a cotton ticking. This was

an experimental mattress intended to be compared to all-cotton and mixed fibers batting

constructions

.

Mattress M20 was a hospital mattress from the same manufacturer and of the same basic size

and construction as M01. Here, however, only a single uniform layer of polyurethane foam

was used for the core, apparently as a cost-cutting measure.

Mattress M21 was a newly developed hospital mattress making use of an interliner for flame

barrier purposes. The construction consisted of a PVC ticking, then a highly retardant

treated neoprene interliner. Next a layer of polyurethane foam, then a small amount of

cotton batting and finally a jute insulator on top of the innersprings

.

4
Mattress M22 was a pilot production prison unit using a highly retardant treated hydrophilic

polyurethane foam of similar, but more recent formulation than M15. A vinyl ticking with

nylon fabric reinforcement was used.

Mattress M23 was an athletic mat, consisting of buff-colored PVC-nitrile foam with a skin

coat of PVC.

Mattress M24 was jail cell padding material, consisting of black PVC-nitrile foam, covered

with a hand laid-up surface covering comprising three fiberglass netting layers encapsulated

in a sprayed-on PVC skin coat.

Mattress M25 was the final production version of M22.

Control Mattress A control mattress which would not contribute to the fire was required in

order to isolate the effects of bedding combustion. For this purpose a 100 mm thick batt of

fiberglass, resting on cement-asbestos board was used. The organic content of the fiberglass

batt was burned out prior to testing.

The properties of the bedding used to cover the test mattresses are listed in Table 3.

3. FULL-SCALE EVALUATION

To evaluate the hazard, a set of criteria was evolved for the tenability of the room of

fire origin. The evaluation was accomplished in two steps. Any mattresses which, by themselves, led to room flashover were considered to be least safe. Flashover was defined as

2 the instant at which the heat flux exceeded 20 kW/m at the floor level. This heat flux is

sufficient to ignite many combustible materials. Specimens that did not lead to room flashover were then evaluated according to three tenability criteria. The values of the criteria

were associated with incipient incapacitation and are the following:

2 Heat Flux exposure >2.5 kW/m (Note that this

2 is substantially lower than the 20 kW/m set as flashover limit above)

Gas Concentrations

C0

2 > 8%

0

2 < 14%

COHb > 25%

Smoke Obscuration

extinction coefficient > 1.2 m

5
The carbon monoxide effects were evaluated using a formula from Stewart [3] for calculating predicted carboxyhemoglobin (COHb) levels. Details of the development of all the

criteria are given in [1]. The analysis of test results was based on the above criteria, and

led to establishing four performance groups.

Group A - Mattresses in this group did not exceed any criteria throughout the test.

Group B - Mattresses in this group exceeded the smoke obscuration limit, but did not exceed any

other criteria.

Group C - Mattresses in this group exceeded all the tenability limits but did not lead to room

f lashover.

Group D - Mattresses in this group led to room f lashover.

The results showed the following performance:

Group A: M03 and M07, both of cotton innerspring construction.

Group B: M08 and M10, both of neoprene foam construction.

Group C: M02, M05, and M09, all of polyurethane foam construction, and M06 of mixed fibers

construction.

Group D: M01, a polyurethane foam specimen, and M04, a latex foam specimen.

The full-scale results are summarized in Table 4.

4. BENCH-SCALE TEST PROGRAM

The performance of other mattresses could, in theory, be compared and ranked by con- ducting additional full-scale tests. Such a course of action cannot be recommended for two

reasons: (a) the costs of full-scale tests are very high; and, more importantly, (b) the

data may be meaningless unless extraordinary pains are taken to recreate the original test environment. The importance of the latter point was brought out in Part I tests. Reproducibility of tests conducted in the same room by the same operator was good; however,

correlation with data taken in a similar, but not identical, room was poor. Thus, it becomes

clear that unless a validated standard room fire test becomes available, or until our ability

to model room fires improves considerably and the effects of the important variables can be

predicted numerically, interlaboratory agreement in full-scale tests should not be expected.

Bench-scale tests, on the other hand are not only much simpler and cheaper to conduct,

but can usually be successfully controlled to obtain consistent reproducibility. The prime

drawback to bench-scale tests in fire hazard analysis has normally been that their results

6
were scaled on an arbitrary basis and no comparison with full-scale test data was attempted.

This would not be a problem in the present project since an adequate full-scale data base

had been established against which the bench-scale predictions could be compared. The

following goals were established for the bench-scale tests:

° The tests must be reproducible; their results

must duplicate the group ordering of the full-scale

tests. (Within - group differentiation was not

sought since it was not considered warranted by the

precision of the data).

° They should be based, as much as possible, on existing test methods, in order to minimize

development time and facilitate commercial testing.

0 They should not require specially constructed

samples. To the extent possible, specimens are to be cut, through the thickness, from production units

and to be tested as natural composites.

Five candidate tests were initially considered: rate of heat release (RHR) , smoke

density, fuel load (calorific value), flame spread, and ease of ignition. In all cases bench-scale tests were to be performed on mattresses complete with ticking — while fullscale tests had shown that the type of ticking has but minor effect, the absence of any

ticking would significantly change the burning behavior.

4.1 Rate of Heat Release Tests in NBS-II Calorimeter

In order to obtain data best amenable to analysis, it was considered desirable to utilize that calorimeter which can most thoroughly characterize the test specimens. The new

NBS-II calorimeter was thus selected. This instrument [4] is a larger, more flexible, and more fully instrumented version of the instrument first described by Parker and Long [5].

The operation of the instrument is based on constancy of heat output — a "substitution"

burner is used, the output of which is automatically decreased as specimen heat release

increases. Rate of heat release is thus the negative of the substitution burner rate change.

The instrument incorporates the following major improvements: (1) A 150 x 300 mm horizontal

specimen may now be accommodated, with a uniform radiant heat flux across its surface; (2)

the specimen is weighed continuously while under test; (3) an in-place heat flux gage is

mounted directly adjacent to the specimen edge, permitting a continuous measurement of the

total (external radiant panel + specimen flame) flux; (4) the specimen insertion cooling

7
transient has been reduced; (5) observation windows now permit viewing the specimens; (6)

noise and fluctuation levels in the output signal have been reduced. Details of calibration

and operation procedures are given in [4].

Test specimens were prepared by cutting them from the full-size mattresses. Throughthe-thickness specimens were cut out in an area away from the mattress edges. Innersprings,

if any, were excluded. The specimen size was 150 mm wide by 300 mm long, by approximately

50 mm thick. For mattresses where the total thickness, excluding innersprings, was 100 mm or

less, the top 50 mm was used. For mattresses thicker than 100 mm, the thickness of those

mattress material layers greater than 20 mm thick was adjusted so that a similar thickness

ratio would occur in the test sample as in the production mattress. Mattresses that included

interliners for fire barrier purposes were tested by cutting the interliner sufficiently

oversized to permit it to be turned over the edges and stapled down. Mattresses containing

highly compressed material, such that over 25% thickness expansion occurs when ticking

tension is released, were sewn through with metallic thread in sufficient places to attain

the production density. Each mattress sample was wrapped in a single sheet of aluminum foil

to cover the sides and bottom before testing.

Samples were tested in a horizontal position at three different irradiance values: 25,

2 50 and 75 kW/m . These values were chosen to approximately cover the range of irradiance

expected in a room fire. An electric spark ignitor located near the edge of the sample and

approximately 5 mm above the surface was used for ignition. This has the advantage of

negligible heating effects and is easier to maintain than a gas pilot. All specimens were

successfully spark ignited; however, certain retardant treated ones took a relatively long

time to ignite and then to reach their peak burning rate. Each test was conducted for a maximum of 10 minutes. The start of the test, t = 0, was considered to be the moment when

the release curve crosses the baseline, going in the positive direction (see Figure 3) . Most

samples burned to completion before the end of 10 minutes. Cotton and neoprene specimens,

however, tended to flame a short while and then switch to slow smoldering and were still

smoldering upon removal at the end of the test. Figure 3 illustrates typical rate of heat

release results. Most curves showed two peaks, an early one for ticking flaming and a later

one for core flaming. For the high rate of heat release specimens the second peak tended to

be dominant, while for better performing ones the second peak was smaller or absent. The net result is that times to (highest) peak tended to be inversely related to specimen rate

of heat release.

Table 5 summarizes the rate of heat release measurements in the NBS-II calorimeter.

Peak added flux values are derived from the peak heat flux gage reading, minus the specified

panel irradiance. In most cases three sample of each mattress were tested. For the 3-

2 minute average rate of heat release at 25 kW/m irradiance the average coefficient of variation was 0.178. This figure is disproportionately weighted by the very low heat release

8
specimens which showed a large amount of scatter. A more representative measure is the

median coefficient of variation, which was 0.088.

An investigation was next made to determine the effect of sample size on the measurements. Tests on six different specimens were run with smaller samples but under the same operating conditions. A specimen size of 100 mm by 200 mm by 50 mm thick was used. Only a

2 single irradiance value of 50 kW/m was applied. Table 6 shows a comparison between these

smaller samples and full 150 x 300 mm samples. The peak readings are substantially different

for the two conditions. This reflects, probably more than anything else, the difficulty in

obtaining reproducible peak height readings in combustion measurements. The three-minute

average values are, however, in substantially closer agreement. The peak added flux values

are, of course, scale-dependent. Their magnitudes help to explain why the peak rates for the

four specimens M06 through M10 are greater than for the other ones. For specimens M04 and

M05 the ratio of full to small specimen peak fluxes is nowhere near as great as for the other

mattresses. Increased fluxes would tend to boost the release rates for the small specimens.

It does not, however, answer the question why the small specimen rates would exceed those of

the full ones. Possibly convective effects are still important at the smaller size.

4.2 Rate of Heat Release Tests in Modified OSU Calorimeter

The NBS-II calorimeter is viewed as a research tool. Only one such instrument exists;

it is neither simple to construct nor to operate. For the present application, a rate of

heat release test is desired which would readily be commercially available and be simple to operate. The test apparatus developed at the Ohio State University (OSU) [6] answers that

description. The OSU calorimeter does not maintain a constant heat environment, instead,

the release rate is determined by a compensated thermopile measurement in the gas outflow

stream. While simpler, this apparatus has several shortcomings for mattress testing: — the thermopile sensing arrangement does not indicate the full amount of heat

liberated by specimens with more radiative flames (as compared to the methane

gas calibration standard). — sample size and construction are not fully defined. — the pilot burner produces more heat than is necessary for adequate ignition. — also, the smoke measurement system is not needed since a superior technique

(see Section 4.3) is available.

Modifications were made to the procedures described in [6] to overcome these shortcomings and are described in detail in Appendix A. These include the following:

9
(1) Replacement of the thermopile sensing method by an oxygen consumption technique.

The technique involves measuring the oxygen depletion in the exhaust stream as combustion

takes place. Once a calibration is made (with a metered supply gas burner) the rate of heat

release for any other fuel is proportional to the oxygen depletion. The chemical principle

this technique exploits is the near-constancy of the heat of combustion per unit oxygen

consumed for almost all fuels. For a device, such as the OSU calorimeter, where the air mass inflow rate is constant, the following expression can be obtained [7], provided CC^ and

H^O products are trapped out of the sampling line before the oxygen meter

; , [ 0

2 %]

Q = k

1 - 0.0127 [0 %]

(kW) ( 1 )

where [0

2 %] is the volume percent oxygen depletion, baseline minus actual. The calibration

constant k is obtained from methane calibration as

(1 + 0.0127 10

2 %] cal ) [°2«cal

(kW/0

2 %) ( 2 )

The calibration value Q is obtained from a measured methane flow rate and a known

C ^J. ^ lower heat of combustion (50.0 x 10 kJ/kg). In the present test series the calibration was obtained as in Eq. 2, but for simplicity of analysis the small nonlinearity over the expected

range of 0

^ depletion in the denominator of Eq. 1 was suppressed and the RHR expressed as

Q

“ k [0

2 %] (3)

The heat of combustion per unit oxygen consumed is assumed to be identical for methane

and for the test specimen (the methane value is about 4% lower than for "typical" plastics

[8]). To get the rate of heat release per unit area, Q is then divided by the exposed specimen area. Details of the theoretical principles of oxygen consumption calorimetry have been

described by Huggett [8],

The primary advantage of the method over a thermopile technique is its suitability for

flow-through measurements. The heat sensing technique depends on the assumption that the

heat radiated away is negligible and that the heat storage term can be empirically compensated. Unpublished measurements by the author and a study by Krause and Gann [9] both indicate that this problem in the OSU calorimeter is a serious one. Oxygen consumption measurements, on the other hand, are free of these errors since oxygen is neither stored nor radiated

away from the calorimeter.

10
To implement oxygen consumption measurements a highly stable oxygen meter is required.

In practice this means that electrochemical units are not suitable and that a paramagnetic

unit is required. The meter should be preceded by traps for particulates, H^O, and CC^. To decrease transit time, a large sample flow is pumped from the calorimeter stack and a quantity

beyond that needed for the oxygen meter is wasted. An absolute back pressure regulator is

desirable at the oxygen meter outlet; otherwise, barometric fluctuations produce variations in

pressure which affect the calibration. For sampling in the exhaust duct of the calorimeter

to be successful, a location must be used where the stream is well mixed so that oxygen con- centration does not vary with small changes in probe positions. With the standard OSU

apparatus [6] no such location is available. To implement the technique, therefore, a modification was introduced which consisted of shutting off the air feed to the cooling

mantle, which is only needed for the thermopile technique. This eliminates stream-combining

turbulence and makes a steady measurement possible. The total flow rate in [6] is set at 40 ft/s, of which roughly 3/4 flows' through the cooling mantle. Since this air is now not

needed, a flow rate of 12 ft/s was set, all of which flows through the combustion chamber.

Further construction details are given in Appendix A. It should be noted that because of

the incompatible flow requirements oxygen consumption and thermopile measurements cannot be

made simultaneously in this apparatus in the same run.

(2) The smoke measurement attachment is not used. Smoke density measurements

are made, instead, with the technique described in Section 4.3.

(3) A 100 mm by 100 mm standard specimen size is adopted. Detailed specifications

are given in Appendix A.

(4) A pilot was desired which produced negligible irradiance to the specimen surface

and a negligible heat release rate, yet was stable in the chamber flow environment. A

small-diameter oxygen/methane pilot was constructed for this purpose.

One serious problem which could not be readily eliminated was the lack of control over

the irradiance. In the NBS-II calorimeter all internal surfaces of the instrument are relatively far away from the specimen. For moderate size specimens, if an irradiance of

2 25 kW/m is measured prior to test, a similar value holds also throughout the duration of a test. In the OSU calorimeter, however, the specimen flames impinge on portions of the

apparatus. These portions heat up and contribute an additional irradiance component. The

specimen is, thus, not tested under invariant external flux. Since no simple way of minimizing this effect was seen, no changes were made to the standard procedure [6] in this

regard

.

Results of measurements in the modified OSU calorimeter are shown in Table 7. Since

no zero-crossing benchmark is available with this procedure, time t = 0 was defined to be the

11
time when an depletion of 0.05% first occurred. The median coefficient of variation

was 0.111, with the average being 0.134. (The comparable measurements in the NBS-II calorimeter, the values were 0.088 and 0.178.) High coefficients of variation were again mostly

associated with low heat release rate specimens. The relative scatter of data with the OSU

and the NBS-II procedures, however, cannot be directly compared since the tests were con- ducted at different stages of instrument development and of operator familiarization.

4.3 Smoke Density Tests

Because of the customary difficulties in relating full-scale smoke measurements to small-scale test results, an attempt was made to obtain a smoke parameter which would be as much as possible only a function of the sample material and would be little influenced by

test apparatus or test conditions. In Part I of this report the concept of an extinction

coefficient was presented as the logical description of the attenuation with a given light

path. If a light intensity Iq is present over a smoke-free path of length L, then the

effect of smoke in reducing the intensity I to a value of I can be expressed as

and k, the extinction coefficient, has units of inverse length, or m An analagous quantity

using base-10 logarithms is the optical density per meter, D/L.

(5)

giving a conversion factor of

k = 2.303 -y- ( 6 )

Furthermore, at a given wavelength or wavelength mix, the extinction coefficient can be

factored out to be

k = (7)

3 3 where C is the smoke mass concentration (kg/m ) , p

g is smoke particulate density (kg/m )

,

and z is a constant for the smoke property of a given material and has the units of volume/

extinction area (m)

.

Consider now an almost-sealed chamber, such as the NBS smoke chamber [10]. The chamber

is initially free of smoke. At time t = 0 mass loss and smoke generation begin. A certain

fraction, X> of the specimen mass loss goes into particulates. Then the smoke mass concentration at any given time t^ is

12
c (t ±

) = _x

V

ch j>

dm dt _2

dt

( 8 )

dm

where V , is the chamber volume (m ) and 3— is the mass loss rate (kg/s) . From the above

ch at relations, the rate of change of k is

dk

dt zp V . s ch

dm

dt

The quantity — serves to characterize the material and will be useful if it turns out not to vary appreciably with time. Since this quantity is effectively an extinction area divided by a unit mass, it is appropriate to call it a "specific extinction area," a .

(9)

a = v , m ch

\

dVJ (m

2 /kg) ( 10 )

Seader and Chien [11] have defined a similar quantity, derived from base-10 logarithms,

called "Mass Optical Density," MOD. These quantities are related according to

a =2.303 (MOD) m (ID

A similar analysis can be made for the flow-through system comprising the full-scale

test room. It is reasonable to assume a two-reservoir model for the room — a clear, cold

lower layer and a warm smoky, stirred upper layer. Then a conservation of smoke mass

gives

[mass generated] = [flow out] + [settling + other losses] + [smoke stored]

= 4f) + [losses] + V

dC

r dt ( 12 )

where V is the room volume

r •tf) is the doorway volume air flow rate, and C is the doorway

outflow smoke concentration. If that flow rate is fast compared to the smoke generation

rate, then the last two terms become negligible and an expression for C can be obtained as

C =

(m/p) (13)

Fang [12] has treated in a similar manner some more complex flow geometries. If we

again assume a constant conversion, of pyrolysates into smoke particulates, then the

smoke generation rate m

s is

m = Y m

s P

( 14 )

13
Combining the above expressions allows us to determine the full-scale specific

extinction area,

a = k (m/p) m m

P

( 15 )

The doorway extinction coefficient k, the doorway volume flow rate, and the fuel

pyrolysis rate m^ are all readily experimentally measureable quantities.

To make the above calculations and compare the full-scale and the smoke chamber om

values in principle does not even require a steady-state room fire. It does require,

however, that the flow velocities be accurately measured, that the upper layer be well

stirred (or at least that an appropriate flow-weighted average of the doorway extinction

coefficients be available) , and that the G^ value be a constant of the specimen.

There would be little hope for a constant 0 in full-scale if it could not be reached m

in the small-scale chamber. Thus, we have to examine the type of results obtainable from

the chamber. For these tests the standard NBS chamber [10] was modified according to the

work of Breden and Meisters [13]. The modifications (Figure 4) consist of two changes —

a horizontal sample holder (requiring a new radiant source) and a load cell weighing

arrangement. The horizontal sample holder is considered appropriate for these tests since

some of the samples melt and drip. To test these in the vertical configuration would be

inappropriate since combustion in the vertical holder's dripping trough is very different

from that for a horizontal sample.

The test procedure was as follows: samples were prepared similarly to the heat release

rate samples, except that the size was 50 mm by 50 mm by 25 mm thick. (Preliminary testing

had shown that larger, 75 by 75 mm samples in some cased tended to "saturate" the chamber

and give erratic results) . The chamber was calibarated and operated according to the

standard method [10] , with the exception of the modifications mentioned above. A small

igniting pilot was used in all cases. The pilotless procedure would not be appropriate for

these tests since in the full-scale the burning bedding assures an ignition source. The

2 standard irradiance of 25 kW/m was used. A continuous record was taken of the weight loss

and the smoke obscuration. The analysis was done according to the equation above for c^.

This requires differentiation of the numeric data to obtain the derivatives. While easily

done, it results in erratic data, the customary difficulty of numeric differentiation. In view of the expected constancy of the G^ value, a different approach was taken. Secant,

rather than tangent slopes were obtained, i.e., the total slopes between the fixed starting

time (t = 10 s) and t = t. were evaluated. A typical a curve is shown in Figure 5. It

l m

can be seen that the value rapidly rises to a peak, then decays slightly in a shallow

plateau. All of the curves obtained had a similar basic shape. The initial low values have

two explanations. Moisture is initially driven off. This results in a weight loss but not

14
any significant obscuration. Also, it does take a finite amount of time after the particles

have been liberated for them to mix and fill the light path. The slight decrease in values

after the peak can be understood as wall loss and settling effects; these effects predominate in the later part of the test. The conclusion can be drawn from this that the peak

0 value is probably the most characteristic, in fact, of the entire pyrolysis process, m

Thus, the peak value, as determined by the secant slope method was adopted for this work.

A comparison between the full-scale results and the smoke chamber data is shown in

Figure 6. The full-scale specific extinction area was determined according to Equation 15

above. If accurate doorway flow velocities were available the extinction coefficient k

would best be determined as a velocity-weighted average over the outflow. However, with

the limited instrumentation used here accurate mass balances could not be obtained. (Outflow

generally exceeded inflow by about 40%. This difficulty of measurement has been discussed

by Tu and Babrauskas [14].) Thus, for the present experiments a simple arithmetic average

of the outflow extinction coefficients was taken. Since there is some reason to believe

the mass inflow readings may be more accurate than outflow, the m value used was based on

the inflow. Outflow density was obtained from temperature readings at thermocouple locations

58, 59, 60, and 61 (Figure 2), which were at 0.13 to 1.07 m below the top of the doorway.

2 The results (Figure 6) show that near the peak burning rate a - 120 m /kg, compared to

2 m

a value of 175 m /kg obtained from the smoke chamber. In view of the uncertainties associated

with the flow rate measurements, this can be considered moderately encouraging. Away from the

peak, the agreement is expectedly less good since the bedding and ignition source make up an increasing fraction of the burning rate. The calculated a for the control test is also shown m

in Figure 6 for comparison. The control test values cannot, however, merely be subtracted out

to obtain the mattress contribution since the burning of the mattress changes the time scale

of the bedding combustion. A summary of the smoke chamber average results for all the

specimens is given in Table 8; for most mattresses three runs were made. The median co- efficient of variation was 0.086, while the average was 0.130,

Finally, it is interesting to see whether any conclusions might be made about y, the

pyrolysate-to-smoke-particle conversion efficienty (Eqn. 14) . Noting that

am

„ _X_

zp

s (16)

one could determine y if Z P

S were known. Seader and Ou [15] reported the results of a study

based on smoke chamber and gravimetric measurements, showing that for piloted ignition con2 ditions and 25 kW/m exposure a constant value of zp is obtained for a wide range of

S -4 2 materials. In the units adopted here, zp = 1.316 x 10 kg/m . This gives

Om

= 7600 y (rn 2 /kg) (17)

15
2 The maximum a measured in this study was 1866 m /kg, for specimen M23. This equates m

2 to an efficiency of 25%. The lowest value was 39 m^/kg, for specimen M07, implying an efficiency of 0.5%.

4.4 Heats of Combustion and Fuel Loads

Each component material for the specimens was tested in the oxygen bomb calorimeter,

ASTM Method D3286 [16]. The gross heats of combustion have been multiplied by the fractional

weight of each component to yield the values in Table 9. A summary of the component heats

of combustion is presented in Table 10. Since in the NBS-II calorimeter a simultaneous

record of mass loss and heat release rate can be obtained, it becomes interesting to compute

effective heats of combustion from these measurements and to compare them to the oxygen bomb

value. Table 11 shows the results. Overall, an average of 56% of the upper heat of com- bustion value is developed. Certain specimens that tend to smolder slowly, primarily the

cotton batting and neoprene foam units, show much lower percentages than the remaining

specimens. A comparison of the results showed that fuel load alone could not be used to correctly group according to performance, while fuel load used in conjunction with rate of

heat release did not improve the characterization.

4.5 Flame Spread and Ease of Ignition

Flame spread is usually considered to be an important element of flammability. Likewise, ease of ignition can affect the rate of hazard development. To determine if either of

these properties must be considered for mattress hazards, some screening tests were conducted

on selected mattress samples. Flame spread behavior was measured on horizontal specimens

exposed to a uniform external radiation field. The apparatus used has been described by

2 Kashiwagi [17]. In experiments of this kind fluxes in the range of 0 to 20 kW/m can be

2 imposed (the latter limit arising due to flash ignition occurring at < 20 kW/m ) . Here

2 fluxes in the range of 4 - 8 kW/m were used. Specimens without any bedding were tested

first. The flame spread rate proved to be dominated by the ticking characteristics. Since

this was at variance with the full-scale findings, as determined in [1], additional tests were conducted using two bedsheet layers covering the specimen. Under those conditions the

ticking material no longer controlled the behavior. The results, however, then appeared to conform more to the rate of heat release findings. Flame spread investigations were not continued further because it was judged that such data would not materially aid in predicting

full-scale behavior.

Ease of ignition was tested using a conical radiant heater, patterned after a proposed

International Organization for Standardization (ISO) ignitability test [18] . Spark ignition

was used in our version of this procedure. An analysis of an exploratory series of tests

16
showed, however, that nearly the same Information that is given by the ignitability tests

could, for these mattresses, be obtained from the NBS-II calorimeter by using the time-topeak data (Figure 7). Thus, for this application a separate ignition test would not be

useful.

5. ANALYSIS OF FINDINGS

The time to exceed criteria could potentially have been used as the full-scale variable

to which bench scale results were to be compared. It was considered not desirable to do

this, however, since this variable does not strictly have a continuous scale; i.e., the

better performing specimens do not have a value for "time to exceed criteria" since they do

not exceed the criteria. For comparison purposes, therefore, the peak full-scale readings were selected. These readings would not have been as desirable for the initial rankings

since, as discussed in Part I, there is a fair amount of variability associated with peak

readings. For comparison to the bench-scale data, however, they constitute the best available variable.

Next to be resolved was the question of which full-scale variables should be used in the

comparison. Floor heat flux readings reflect directly the potential for flashover. They

are also obviously a good indicator of the radiant heat fluxes impinging at occupant level.

Also, not unexpectedly, a close correlation can be made to the average upper gas space

temperatures (Figure 8). Perhaps more unexpected is the close — although definitely not

linear — correlation between CC^ and floor flux (Figure 9) . Even for CO there is a modestly

good association with floor flux (Figure 10), although not as good as for CO2. Thus, it

becomes appropriate to consider the peak floor flux values as adequately representing flashover potential, heat flux, and gas concentration variables.

No special correlation between smoke obscuration and other measurements was sought

since smoke determinations were readily available in bench-scale. Two bench-scale tests,

rate of heat release and smoke evolution were thus selected for representing the full-scale

results

.

Rate of heat release tests in the NBS-II calorimeter yielded numerous data: varying

irradiance values, peaks, averages, and times to peak being some factors to be considered.

It was easily evident that time-to-peak-RHR would not be an appropriate variable (Figure 11).

Peak R.HR values were also seen to be of poor predictability. This left some form of

average RHR variable to be considered. Hitherto, vague and qualitative arguments [19, 20]

have been used to attempt to show that one or another form of averaging is best. For the

present study a purely operational approach was deemed best — that averaging technique was

to be selected which gave results best correlated with the full-scale measurements.

17
2 Averages were calculated for 25, 50, and 75 kW/m irradiance and for 1, 2, 3, 4, and 5 minute intervals (all starting at t = 0) . From this comparison it emerged that, the 3-

2 minute average values at a 25 kW/m irradiance produced the best prediction of full-scale

results. The criterion of adequacy was that the bench-scale results would correctly group

the mattresses into their full-scale groupings. Within-group ranking was not considered

material due to basic limits on precision. It is seen in Figure 12 that the procedure was

successful. Groups A/B, C, and D were adequately separated, with some margin available

between groups. (Note that the distinction between groups A and B comes only from smoke

performance.

)

The NBS-II calorimeter is, however, not being proposed as the standard device for

determining mattress RHR groupings. The important issue was to determine if the modified

OSU calorimeter would be successfully usable in classifying the performance. As a starting

2 point, the same nominal irradiance (25 kW/m ) and the same averaging period (3 minutes) were taken. Figure 13 shows that these were satisfactory choices and the modified OSU

calorimeter can be used to discriminate between groups A/B, C, and 1). Note that there are

no cross-overs across group boundaries and that the groups are well separated. Thus, the

chosen irradiance level and averaging period can be used for a standard test. Figure 14 shows a direct comparison of the results. Expected differences would stem from the decreased

specimen size in the OSU calorimeter (tending to lower the RHR) and the excess flux imposed

from apparatus surfaces (tending to raise the RHR). Since Figure 14 shows a fairly close

agreement, it appears that these effects are largely offsetting each other.

For smoke development, it was already established that o^, the specific extinction area, constituted the proper specimen descriptor. Yet, is essentially a measure of the pyrolysate to soot conversion efficiency. The smoke measurements in the test room, on the other

hand, essentially reflect a product,

(soot efficiency) x (rate of pyrolysis)

The rate of pyrolysis is established as:

pyrolysis rate , . , ,

.

x (area involved)

,

unit area

II M which schematically is m A . The complete product then becomes a m A and has the units

2

; PP mpp

m /s. Realistically, the mattress area involved in combustion is not a quantity that is

ii readily determinable. Thus, we undertake to substitute for G m A some simpler expression m p p which can be gotten from the bench-scale tests. An appropriate candidate is x RHR. Since this is a large number, for convenience we define a "smoke parameter" SP as

a x (RHR) m

18
Because of the variable choices taken, the units for SP become kW/kg.

2 The RHR Factor is taken to be the same 25 kW/m irradiance, 3-ininute average value as was earlier found suitable for predicting the full-scale heat flux results. This entire

expression, while based on proper physical considerations, has to be justified empirically

because of the approximations and simplifications involved. Figures 15 and 16 show the

results for the SP when the RHR factor in it is based, alternatively, on NBS-II and OSU

data. A satisfactory agreement is seen to be achieved in both cases. The Figure 16 results,

based on OSU data, can then be used for testing and evaluation.

6. CRITERIA FOR PREDICTING FULL-SCALE BEHAVIOR

The RHR and smoke measurement techniques utilized were shown to be suitable for predicting full-scale behavior from bench-scale test procedures. Thus it is recommended that a suitable test method for grouping the performance of institutional mattresses when exposed

to flaming ignition sources is one utilizing the procedure given in Appendix A and based on the following criteria.

Group A -- specimens in this group shall have RHR < 100 and a smoke parameter SP < 0.25.

Group B — specimens in this group shall have RHR < 100.

Group C — specimens in this group shall have 100 < RHR 200.

Group D — specimens which have RHR > 200 shall be placed in this group.

It is seen that the smoke parameter is needed only to distinguish between Groups A and

B. No limits on the smoke parameter, per se, need to be placed for Groups B, C, and D,

although, in practice. Figure 16 illustrates that these groups do exhibit successively poorer

smoke behavior

Table 12 shows the over-all performance results of all the mattresses, including the

supplemental ones.

Group A includes, in addition to the original cotton batting specimens, three neoprene

mattresses, an all-polyester batting mattress, a neoprene interliner protected mattress, and

the latest version of hydrophilic polyurethane foam type unit.

Group B includes, in addition to the original neoprene mattresses, an earlier version

of a hydrophilic polyurethane foam type.

19
Group C includes, in addition to the original polyurethane and mixed fibers mattresses,

an ordinary polyurethane foam mattress, a cotton batting mattress with polyurethane topper

and some foam mattresses claimed to be retardant treated and highly flame resistant. Also

included in this group is a PVC-nitrile foam jail cell padding.

Group D includes a latex foam and a high density polyurethane foam mattress from the

original series and also a PVC-nitrile foam athletic mat.

7. HAZARD FACTORS ASSOCIATED WITH USAGE CONDITIONS

The minimum group requirements for any given application cannot be properly determined

without considering the entire collection of hazards and defense mechanisms. In other words,

a fire safety engineering analysis is the context within which furnishings hazard components

should be assessed and minimuras prescribed. Several specific points of interest, however,

merit some discussion.

7.1 Arson and Accelerants

Arson and accelerants will, by definition, increase burning rates and hazards

associated with mattresses. For this reason it is sometimes suggested that full-scale

testing be done under conditions simulating arson, rather than incidental fires. This is

appropriate if the goal is to determine the maximum hazard associated with an arson fire,

but is not appropriate if, as here, the goal is to evaluate and rank the relative performance

of a piece of furnishing. Under the limiting conditions of a large amount of effective

accelerant, the accelerant alone is being evaluated. For lesser but still substantial

accelerant usages the differences between the furnishings items are simply diminished. On

the other hand, the ignition source has to be strong enough to ensure satisfactory and

continued ignition. The bedding/wastebasket combination in the full-scale tests and the

2 25 kW/m irradiance in the bench-scale procedures were designed to meet this objective.

Thus, the relative ranking of performance will stay similar as the fire scenario threat

level is increased, even though all specimens will perform worse. A special consideration

may be required in those cases where a specimen uses a barrier interliner to decrease the

rate of heat release from the core materials. A decision has to be made whether such units

are likely to be stripped prior to being burned.

7.2 Storage and Orientation Effects

The full-scale test scenario involved single mattresses placed and oriented in a normal

sleeping configuration. Parker [21] found that increased burning occurred when mattresses

were tested in a vertical position. A different environment again is involved in storage

20
rooms, where numerous mattresses may be stored. A specific fire engineering study is needed

to assess the adequacy of fire safety in those situations; however, it can again be presumed

that mattresses classed by the recommended test into higher groups will perform better.

7.3 Fuel Area Effects

The test specimens in the present study were primarily twin-size mattresses, all of

similar widths and lengths. Mattress area effects, in consequence, were not relevant. In

a given application it can happen that areas are significantly larger or that numerous units

are located close to one another, permitting the possibility of continued flame spread. The

expected mattress behavior in these circumstances falls into two categories. Mattresses in

Group A or B do not spread flame easily. (In full-scale tests their steady, continued

burning was ensured by the bedding used.) Thus, if Group A or B mattresses of significantly

larger sizes than the test specimens are placed in a room the fire development rate would

not be greatly affected. Mattresses in Groups C and D, on the other hand, spread flame much

more easily and readily build up an intense fire. Increasing the mattress area in those

cases would directly increase fire development rates and, therefore, the hazards.

8. CONCLUSIONS

The performance of institutional mattress specimens, when evaluated in bench-scale

laboratory tests showed that:

(1) Flame spread and ignition properties do not characterize mattress behavior

consonant with full-scale tests.

(2) Rate of heat release and smoke production are the two bench-scale measurements

necessary and sufficient to reproduce full-scale findings.

(3) For determining the rate of heat release, both the irradiance level and the

averaging period can affect relative performance ranking. Proper conditions are determined by comparison to full-scale results.

(4) Either the NBS-II or a modified OSU calorimeter can be used to obtain suitable

rate of heat release data. The NBS-II calorimeter has the advantage of better control

while the modified OSU calorimeter is less costly and simpler to operate.

(5) Bench-scale smoke measurements can provide a useful estimate of expected fullscale results if a procedure based on a modified NBS smoke density chamber is used.

21
(6) Specimen fuel load values can be used to roughly rank performance only (a) within

a single specified material type and (b) provided burning rate is relatively high,

i.e., not in Groups A or B.

(7) A procedure for proposed standard test has been developed which allows suitable

prediction of mattress performance groups.

(8) A large number of additional samples, not tested in full-scale, were evaluated in

the bench-scale test procedures. Neoprene foam mattresses are now available with

Group A performance, and, for the first time, a special polyurethane foam formulation

was seen which gives Group A performance.

It is emphasized that the test procedures developed are for additional flaming

resistance requirements and do not replace the mandatory cigarette ignition standard [2].

ACKNOWLEDGEMENTS

This project was sponsored, in part, by the Consumer Product Safety Commission and by

the Department of Health and Human Services. It would not have been possible without the

continued guidance and support of Sanford Davis. Robin Breese, William Twilley, David

Swanson, and Dennis Sullivan assisted in the bench-scale tests.

22
REFERENCES

[1] V. Babrauskas, Combustion of Mattresses Exposed to Flaming Ignition Sources, Fart I. Full-Scale Tests and Hazard Analysis, Nat. Bur. Stand. (U.S.), NBSIR 77-1290 (1977).

[2] Standard for the Flammability of Mattresses and Mattress Pads (FF4-72) , 40 FR 59940,

CFR Part 1632.

[3] R. D. Steward, et al.. Experimental Human Exposure to High Concentrations of Carbon

Monoxide, Arch. Environ. Health , 26 , 1-7 (Jan. 1973).

[4] J. Tordella, Development of a Calorimeter for Simultaneously Measuring Heat and Mass

Loss, Nat. Bur. Stand. (U.S.), to be published.

[5] W. J. Parker, M. E. Long, Development of a Heat Release Rate Calorimeter at NBS, pp. 135-151 in Ignition , Heat Release and Noncombustibility of Materials (STP 502)

American Society for Testing and Materials, Philadelphia (1972).

[6] Proposed Test Method for Heat and Visible Smoke Release Rates for Materials. American

Society for Testing and Materials (1980)

[7] J. R. Lawson, et al. , Development of a Heat Release Rate Calorimeter Using Oxygen

Consumption, Nat. Bur. Stand. (U.S.), to be published.

[8] C. Huggett, Estimation of Rate of Heat Release by Means cf Oxygen Consumption Measurements. Fire and Materials , 61-65 (1980).

[9] R. F. Krause, R. G. Gann, Rate of Heat Release Measurements Using Oxygen Consumption,

J. Fire and Flammability , 11 , 117-130 (April 1980)

[10] Smoke Generated by Solid Materials (No. 258). National Fire Protection Association,

Boston (1976).

[11] J. D. Seader, W. P. Chien, Mass Optical Density as a Correlating Parameter for the

NBS Smoke Density Chamber, J^_ Fire and Flammability , 5_, 151-163 (April 1974) .

[12] J. B. Fang, Fire Buildup in a Room and the Role of Interior Finish Materials, Nat. Bur. Stand. (U.S.), Tech. Note 879 (1975).

[13] L. H. Breden, M. Meisters, The Effect of Sample Orientation in the Smoke Density

Chamber, J. Fire and Flammability , ]_, 234-247 (April 1976).

23
[14] K. M. Tu, V. Babrauskas, The Calibration of a Burn Room for Fire Tests on Furnishings,

Nat. Bur. Stand. (U.S.), Tech. Note 981 (1978).

[15] J. D. Seader, S. S. Ou, Correlation of the Smoking Tendency of Materials, Fire

Research , 1., 3-9 (1977).

[16] Standard Method of Test for Gross Calorific Value of Solid Fuel by the IsothermalJacket Bomb Calorimeter (D3286) . American Society for Testing and Materials,

Philadelphia.

[17] T. Kashiwagi, Experimental Observation of Flame Spread Characteristics Over Selected

Carpets, JFF/Consumer Product Flammability , 1^, 367-389 (December 1974).

[18] Draft Proposal DP 5657, Fire Test-Reaction to Fire - Ignitability of Building Materials,

International Organization for Standardization (June 1977).

[19] E. E. Smith, Heat Release Rate of Building Materials, pp. 119-134 in Ignition , Heat Release , and Noncombustibility of Materials (STP 502). American Society for Testing

and Materials, Philadelphia (1972).

[20] S. B. Martin, Characterization of the Stanford Research Institute Large-Scale HeatRelease-Rate Calorimeter (NBS-CGR 75-54). Stanford Research Institute Project

PYU-3534 for the National Bureau of Standards (1975).

[21] W. J. Parker, Comparison of the Fire Performance of Neoprene and Flame Retardant

Polyurethane Mattresses. Nat. Bur. Stand. (U.S.), NBSIR 73-177 (1973).

[22] K. D. Steckler, Fire Induced Flows Through Room Openings - Flow Coefficients.

Armstrong World Industries Special Report (September 1980)

.

[23] J. A. Rockett, Fire Induced Gas Flow in an Enclosure, Combustion Science and

Technology. 12, 165-175 (1976).

24
TABLE 1 Mattress Sizes and Weights

Mattress

Size (over-all)

Total

Weight

(kg)

Weight

of

Combustibles

(kg)

Weight

of

Innerspring

(kg)

Width

(m)

Length

(m)

Thickness

(m)

M01 0.89 2.03 0.17 14 14 —

M02 0.89 2.03 0.17 15 6 9

MO3 0.89 2.03 0.17 20 11 9

MO4 0.92 2.11 0.11 19 19

i MO 5 0.95 1.88 0.13 6 6

|

1 MO 6 0.99 1.91 0.18 20 12 8

MO7 0.99 1.91 0.18 25 13 12

i M08 0.88 1.93 0.15 18 18 —

MO9 0.66 1.84 0.08 3.2 3.2 —

MIO 0.66 1.84 0.08 6 6 —

Mil 0.71 1.91 0.10 11 11

1

i Ml 2

i 0.66 1.83 0.08 11 11

M13 0.66 1.83 0.08 6.5 6.5 —

Ml4 0.99 1.93 0.10 13 13 —

Ml6 0.99 1.93 0.10 13 13 —

Ml 7 0.96 1.90 0.17 19 9 10

Ml 8 0.69 1.87 0.08 14 14 —

Ml9 0.96 1.90 0.20 15 8 8

M20 0.89 2.03 0.15 6 6 —

M21 0.91 2.03 0.16 16 8 8

M2 2 0.73 1.84 0.18

j 4

17 17 —

25
TABLE 2. PHYSICAL PROPERTIES OF MATTRESSES

MATTRESS

INNER- SPRINGS LAYER

TOTAL NUMBER

COMPOSITION OF LAYERS THICKNESS

(mm) DENSITY

(kg/m ) PT

2 (kg/m ) FLAME RETARDANTS

M01 no Ticking Polyvinylchloride 2 0.34 1100 0.378 yes

Outer Padding Polyurethane, (TDI/polyether type)

2 36.8 25 0.921 slight

Inner Core Polyurethane, (TDI/polyether type)

1 86.9 64 5.561 yes

MO2 yes Ticking Polyvinylchloride 2 0.34 1120 0.385 yes

Padding Polyurethane, (TDI/poly- ether type)

2 37.5 19 0.712 no

Interfacing Polypropylene fabric 2 0.25 260 0.064 no

M03 yes Ticking Polyvinylchloride 2 0.34 1100 0.379 yes

Padding Cotton Felt 2 49.6 38 1.883 yes

Interfacing Polypropylene fabric 2 0.22 320 0.070 no

M04 no Ticking Polyvinylchloride with

cotton backing

2 0.56 730 0.410 yes

Core Latex (butadiene-styrene) 1 101.6 81 8.23 no

MO5 no Ticking Rayon fabric (outer)

2 0.25 620 0.154 no

Padding Polyurethane foam 2 0.71 110 0.078 no

Rayon fabric (inner) 2 0.10 200 0.020 no

Core Polyurethane foam 1 127. 20

M06 yes Ticking (2) Polyester 2 0.25 680 0.170 no

Padding Cotton/polyester felt 2 38.0 43 1.63 no

Insulator Cotton/nylon/polyester pad 2 7.0 90 0.63 yes

MO7 yes Ticking Cotton 2 0.46 650 0.300 yes

Padding Cotton felt 2 38.1 38 1.46 yes

Insulator Jute pad 2 6.4 120 0.788 no

MO8 no Ticking Cotton 2 0.46 550 0.253 yes

Core Polychloroprene foam IV.

' 152. 67 10.18 yes

M09 no Ticking Polyvinylchloride with nylon fabric reinforcement

2 0.36 790 0.284 yes

Core Polyurethane (TDI/ polyether type)

1 76.2 22 1.68 no

MIO no Ticking Polyvinylchloride with

nylon fabric reinforcement

2 0.33 1070 0.354 yes

Core Polychloroprene foam 1 76.2 50 0.253 yes

Mil no Ticking Cotton 2 0.46 550 0.253 yes

Core Polychloroprene foam 1 98. 82 8.04 yes

M12 no Ticking Cotton 2 0.46 550 0.253 yes

Core Polychloroprene foam 1 75. 113 8.48 yes

Ml 3 no Ticking Cotton 2 0.46 550 0.253 yes

Core Polychloroprene foam 1 75. 62 4.65 yes

Ml4 no Ticking Polyvinylchloride 2 0.40 895 0.36 yes

Core Polyvinylchloride 1 110. 52 5.67 yes

Ml 5 no Ticking Polyvinylchloride with

nylon fabric reinforcement

2 0.33 1070 0.354 yes

Core Hydrophilic polyurethane foam 1 187 yes

26
TABLE 2. (Continued)

MATTRESS

INNER- SPRINGS LAYERTOTAL NUMBER COMPOSITION OF LAYERS THICKNESS

(mm) DENSITY(kg/m ) PT

2 (kg/m ) FLAME

RETARDANTS

M16 no Ticking Cotton 2 0.50 350 0.18

Core Polyurethane foam 1 110. 52 5.67 yes

M17 yes Ticking (2) Cotton/polyester 2 0.40 495 0.20

Padding Polyurethane foam 2 7.9 22 0.17

Facing Rayon interliner 2 0.10 228 0.02

Padding Polyurethane foam 2 10. 21 0.21

Padding Cotton batting 2 20. 46 0.92

Insulator Scrap felt 2 6.0 88 0.53 no

M18 no Ticking Cotton 2 0.50 460 0.23 yes

Core Polychloroprene foam 1 80. 131 10.5 yes

M19 yes Ticking (2) Cotton/polyester 2 0.40 460 0.39 no

Padding Polyester batting 2 — — 0.78 no

Netting Polyolefin 2 — — 0.09 no

Padding Polyester batting 2 — — 0.85 no

Netting Polyolefin 2 — — 0.09 no

M20 no Ticking Polyvinylchloride 2 0.38 1020 0.39

Padding Polyurethane foam 1 152. 18.3 2.78

M21 yes Ticking Polyvinylchloride with

nylon fabric reinforcement

2 0.32 895 0.29 yes

Interliner Neoprene foam with

fiberglass backing

2 6.9 181 1.25 yes

Padding Polyurethane foam 2 17 21 0.36

Padding (3) Cotton batting 2 ~ 26 —

Insulator Jute 2 7.1 64 0.45

M22 no Ticking Polyvinylchloride with nylon fabric reinforcement

2 0.43 950 0.41 yes

Padding Hydrophilic polyurethane

foam

1 78. 150 11.7 yes

M23 no Skin layer

Foam

Polyvinylchloride

PVC-nitrile foam

1

1

31. 124 3.84

M24 no Skin layer Fiberglass with polyvinvychloride

1 22.8 151 3.44

Foam PVC-nitrile foam 1

M25 no Ticking Polyvinylchloride with

nylon fabric reinforcement

2 0.33 1028 0.34 yes

Padding Hydrophilic polyurethane

foam

1 76. 158 12.0 yes

(1) Top quilted, bottom not quilted.

(2) Top and bottom quilted.

(3) Only near center of mattress.

27
e>zH§wM

PpO

CPwH

piW

CMS

P-4 w

kJ«<H

X 4-1 o

X! cd 00 u> •H

CD o o vo av CM 3 60 <1- vO o VO i—

O X • • • rH ^

cd

4-> o o iH o o d

O

OH

/-s

CM <—

m

O o oom s vO CM o 1 CO o CM

H \ rH rH CM 1 CM rH rH

Q. 00 • • • • • x o o O o o o

4-J CO •h e in o m 1 m

mm

co—

ON n- CM l r- OV

a so

0) « m

mm

m r^. in

CO

CO

d) /—

CM oo o <r i—

e g

CM CM co i i—CM

x § • • • i • • • o ^

*H o o o o o O 4-J X p H oa

CD

CD

H

nd 6^ •H fiM? 4-J

C

O <r

UO

p o m i—

o m cd •H <D r- ,

Pi

4-> •*

u #*

u

aX •>p

*H

a 0) c CD cd o c (D c

CO o 4-J o 4-J

X rH o 4-J *H

O 4-J CO 4-J CO 4-J >4 4-J CO cx 4-J <D 4-J a) CD a 4-J (D in 0 c O >> o >4 P c •H o >4 o o u rH o 1 1 3 O > o rH CD U 4-) O o >4 4-1 >•> O rH

4-J Pi Ph rH 4-J rH P4 X o O vO O O O o cd u in 00 P-i c_> P< m H

CO

CD

/-s CO <r o\ Ov Ov i—

CD

X 00 vO IN vO vO Ov CO X • • • • • • 3 1—

CM CM

O o o CD N-' \ 1 P- 0 X X X 1 X X X 3

(U N—/ N vO CO CO 1 CM CM CMCO •H CO oo Ov m in m T3

CO • • • • • • e

rH rH rH o o o cd

COo

00 (D e O Vj •H U 4-J rH CD o O

/-s

X > (DO

O •H

O 4-J CD s 14-4 U o CO CD 4J 4-J u cd rH

0) N—' 1 1 X CJ

X CD cd X CO TJ E* & H CO 4-J Cd o o o 3 <D <D rH rH rH CO

cd <v

H i—1 1—1 rH •H

X O- •H •H •HX o CO CO Ph p. p. H II

28
TABLE

4.

FULL-SCALE

EVALUATION

RESULTS

ao x *H u a) 4-1 • • 03 CO /H DC dc

OO o o o o o o

<D o l CO • • co oo

m oo CO

O

DC E 3 w z z vO CNI <r <r CO CM CO co

C/0 o o CO u o

<uE co

0)

H 3

rH

X 1 CO 4-) 3 1 > c rH • • • • CO Pn /-v DC DC DC DC o O

O o O o

CO *—1

•H CO • • • • o oo o vO CO

*H CO T3 4J

w z z z z vO

m CO CO *<r CSI

La CO CO

0) od <U

4-1 4—< X H •H c

4-1 o

•H •H

iH 4-1 H CO • • • • CO u ^ dC DC DC DC

O o o m o o

CO CO 4J CO • • • • rH mt rH «'d- s& c o c w z z z z m <r CO CO

<u a) H uco

CJ

4J 3 c o <u *H E L X cu

(1)

u > 4-1 CO rH

•H 0) o

CJ c ^ PS DC DC PS PS PS pc pc

OO o M CO • • • • • CM

L 4—1 z z z z z z z z 0) E > (1) o o E o

.3

— DC

CO

H CO rH

rH rH

Ph 3

PH3o rH rH

*H CO CO

4-1 rH >.

H *H rH rH i—1 a CO L U O CO CO CO *H 4J 3 c CO 3 u V4 4-> 4J 4-1 H 0 O 4J O CD (U *H H H a CL CO CO *H CO g g CL CL CL

CO CO *H *H rH

H

gg CO CO CO

a;

O

L

L

L o o o o o Q EC CM PM z Cm o u EC * X

0) "s <D 0) 0) 3 o 3 e 3

<D CO rH

L CO CO co cc 0) -3 X X

a> 0) 4-1 z 4-1 4-» 4J 4->

H 3 3 V CO a; <D <D c 3 a> a) u 3 a) u U U

0) o o L

L 3 o 3 3 X 3 u 4-» 4-1 CL CL 4-1 rH « >> c 4-1 4J o O rH 4-1 o rH rH 4-> rH

CJ o o 0) (1) o 0 Cm o O CO

O

u o z CM

u (X CM

a Cm

CO

CO

0)

J-t co o oo ON vO

m CM rH

4-1 o O iH o o O o o o o

4-1 z z z 2 2 2 2 2 2 2

CO z

CL3O < CD o Q Li o

29 I

N.R. -

Not

Reached
TABLE

5.

RATE

OF

HEAT

RELEASE

MEASUREMENTS

IN

NBS-II

CALORIMETER

30
TABLE 6. EFFECT OF SPECIMEN SIZE ON HEAT RELEASE

(50 kW/m2 Irradiance)

t

Mattress

Peak RHR (kW/m

2

) 3-Min Avg. RHR (kW/m

2

) Peak Added Flux (kW/m

2

) Small

Specimens

Full

Specimens

Small

Specimens

Full

Specimens

Small

Specimens

Full

Specimens

M04 1400 1190 800 684 16.3 36.

MO5 1210 960 205 208 8.6 25.8

MO 6 306 555 192 257 1.7 12.6

MO7 204 640 83 88 0.8 12.1

M08 324 525 206 209 0.6 10.3

M10 313 470 208 204 0.5 3.8

TABLE 7. COMPARATIVE RATES OF HEAT RELEASE

(25 kW/m Flux, 3-Min. Averages)

Specimen

NBS-II

value

(kW/m

2

)

OSU

value

(kW/m )

OSU/NBS-II

M01 399 344 0.86

MO 2 138 144 1.04

MO3 60 45 0.75

M04 479 624 1.30

MO5 179 187 1.05

MO6 127 119 0.94

MO7 43 46 1.07

MO8 89 62 0.70

MO 9 152 153 1.01

M10 N.A. 83 —

Mil 43 50 1.16

Ml 2 22 16 0.72

Ml3 N.A. 66 —

M14 245 178 0.73

M15 51 52 1.02

Ml 6 211 132 0.63

Ml 7 112 102 0.91

Ml8 25 22 0.85

Ml 9 98 85 0.87

M20 175 170 0.97

M21 27 21 0.78

M2 2 21 72 0.79

M2 3 241 239 0.99

M24 124 104 0.84

M2 5 63 52 0.83

N.A. - not available

31
TABLE 8 SMOKE RESULTS

Average

0

2m

(m /kg)

Smoke Parameter SP*

With RHR Factor

Based on NBS-II

Smoke Parameter SP*

With RHR Factor

Based on OSU

M01 757 3.02 2.60

MO2 833 1.15 1.20

MO3 383 0.23 0.17

M04 1504 7.20 9.38

MO 5 175 0.31 0.33

MO 6 304 0.39 0.36

MO7 39 0.02 0.02

M08 924 0.82 0.57

MO 9 779 1.18 1.19

M10 1076 N. A. 0.89

Mil 450 0.19 0.23

Ml 2 258 0.06 0.04

M13 1150 N.A. 0.76

M14 1083 2.65 1.93

M15 N. A. N.A. N.A. Ml6 993 2.10 1.31

M17 306 0.34 0.31

Ml 8 236 0.06 0.05

Ml 9 249 0.24 0.21

M20 1159 2.03 1.97

M21 857 0.23 0.18

M2 2 978 0.89 0.70

M23 1866 4.52 4.46

M24 791 0.98 0.82

M2 5 385 0.24 0.20

* SP a x RHR

m

N. A. - not available

32
TABLE 9. MATTRESS TOTAL FUEL

Specimen Fuel

(MJ)

M01 415

MO2 184

MO3 225

M04 742

MO 5 175

M06 268

MO7 287

MO8 474

MO9 95

M10 149

Mil N. A

Ml 2 185

Ml 3 153

Ml 4 294

Ml5 N.A

Ml 6 296

Ml 7 171

Ml 8 219

Ml9 213

M20 180

M21 139

M2 2 186

N. A. - not available

33
TABLE 10. TYPICAL HEATS OF COMBUSTION FOR MATTRESS MATERIALS

Material Heat of Combustion, Gross (MJ/kg)

Average Range

Cotton 18.1 17.4-20.4

Cotton/Polyester 21.2 19.7-22.3

Jute 23.4

Latex 40.6

Neoprene, FR Black 25.8 24.8-26.8

Buff, Bulk 15.6 15.3-15.8

Buff, Interliner 9.7

Polyester 25.8

Polypropylene 48.5 47.5-49.5

Polyurethane

Non-FR 30.5 26.1-31.6

FR 24.2 24.0-24.3

Hydrophilic 11.5 10.1-12.8

Polyvinylchloride 25.1 22.8-26.0

PVC - Nitrile 20.5 17.3-23.6

Rayon 13.6-19.5

34
TABLE 11. EFFECTIVE HEATS OF COMBUSTION AND MASS LOST

(25 kW/m Flux, 3-Min. Averages)

Specimen

Measured m

(s/s)

Effective

Ah

c (MJ/kg)

Total

Ah

c (MJ/kg)

Effective

Total

%

Mass

Lost

After 600s

(%)

M01 0.72 24.9 29.6 84

1 89

MO2 0.25 24.8 30.7 81 94 MO3 0.36 7.5 20.5 37 73

M04 0.77 28.0 39.1 72 89

MO 5 0.35 23.0 29.2 79 95

MO6 0.50 11.4 22.3 51 89

MO7 0.33 5.7 22.1 26 76

MO8 0.43 9.3 26.3 35 70

MO9 0.31 22.1 29.7 74 92 M10 N. A. — 24.8 — N.A. Mil 0.28 6.9 — — 59

Ml 2 0.24 4.1 16.8 24 43

Ml3 N. A. — 23.5 — N.A. Ml4 0.87 12.7 24.3 52 85

Ml5 0.26 8.8 13.7 64 28 Ml 6 0.66 14.4 22.8 63 90

Ml7 0.42 12.0 19.0 63 93

Ml8 0.17 6.6 15.4 43 21 Ml 9 0.29 15.2 26.6 57 93 M20 0.41 19.2 28.0 69 91

M21 0.27 4.5 17.4 26 59

M22 N. A. 10.9 35

J

N. A. - not available

35
TABLE 12. SUMMARY PERFORMANCE GROUPS

(As determined by the proposed test method, Appendix A)

Group Specimen Heat Release Rate

RHR

Smoke Parameter

SP

A MO3 45 0.17

MO 7 46 0.02

Mil 50 0.23

Ml 2 16 0.04

Ml 8 22 0.05

Ml 9 85 0.21

M21 21 0.18

M2 5 52 0.20

B MO8 62 0.57

M10 83 0.89

M2 2 72 0.70

C MO2 144 1.20

MO 5 187 0.33

MO 6 119 0.36

MO9 153 1.19

Ml 4 178 1.93

Ml 6 132 1.31

Ml 7 102 0.31

M20 170 1.97

M24 104 0.82

D M01 344 2.60

M04 624 9.38

M2 3 239 4 . 46

36
w

SYMBOLS ALL DIMENSIONS IN METERS

+ LOAD CELL • THERMOCOUPLE -GAS O THERMOCOUPLE- SURFACE

HEAT FLUX METER

-©• GAS PROBE

Figure 1 , Plan View of Full-Scale Test Room A
93

SYMBOLS • THERMOCOUPLE -GAS

O THERMOCOUPLE- SURFACE

HEAT FLUX METER

V VELOCITY PROBE

SMOKE METER LIGHT PATH

©• GAS PROBE

Figure 2. Elevation of Full-Scale Tfest Room A

38
Figure 3. Typical NBS-II Calorimeter Results
Figure 4. View of Smoke Density Chamber with Horizontal

Holder Arrangement

40
Figure 5. Typical Curve for a Mattress Specimen

41
Figure 6. Specific Extinction Area Measurements for Specimen M05

42

MASS

LOSS

RATE

(kg/s)
1a —i—i—i i i r 1 1 1 1 1 1 1 1

00 600 Urn -

*—

<cocc

550 •4

o.

D_<

500

o

1—

450 — —

cs 400

LkJ 350 - »9 —

OS1—

c

300

•6 —

0£UJ

Q_

250 •8

Point labels are

2:

Lkl I— 200 • 7 specimen numbers ~ <LU

CL

150 — Ot— 100 —

UJS 50 —

1—

1 1 1 1 1 1 i i i i i i i i 0

10 20 30 40 50 60

TIME TO PEAK RHR

70 80 90 100 110 120 130 140

|S) (25 kW/m2 IRRADIANCE)

Figure 7. Predictability of Ignition Times from Calorimeter Data

43
1200

1 1 1 r~“1 1 1 1 1 1

1100 — •4

oo 1000 •1

LkJ OC 900 —

az 800

CL. 700 — —

LU

600 • 2 — <

LU 5 #

Q- 500 Eg

LU

1 •6

o

CO

400 “ #9 Point labels are

1 —1 300 — specimen numbers

200

3

17,8

i 1 1 1

—

10

100

J I I I I _JI iI iI i1 iI Li 0

5 10 15 20 25 30 35 40 45 50

FULL-SCALE PEAK FLOOR FLUX (kW/m2

]

Figure 8. Relationship Between Peak Temperature

and Peak Floor Flux

44
o

LUo

o

o

CO

—1—1—

I

“1 1

1

1 1 1 1 22

•4

20 —

18 •1

16 - -

14 •5 —

12 * *2

•6 —

10 • 9 —

8

Point labels are 6 — specimen numbers

4 —

2

3 t

78,10, | , i i i i i i i 0

5 10 15 20 25 30 35 40 45 50

FULL-SCALE PEAK FLOOR FLUX |kW/m2

)

Figure 9. Relationship Between Peak C0

2 Concentration

and Peak Floor Flux

45
FULL-SCALE

PEAK

CO

CONCENTRATION

|%)

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

100

i i i

•4

•1

•2

•9

•6 *5

I

Point labels are specimen numbers

5 10 15 20 25 30 35 40 45 50

FULL-SCALE PEAK FLOOR FLUX (kW/m2

]

Figure 10. Relationship Between Peak CO Concentration

and Peak Floor Flux

46
CM

oc/>

t i i i—i—i—

r

1

1 1

50 —

45 —

Point labels are specimen numbers

•4 _

40 —

35

•1

30 —

25 —

20 —

15 • 2 #5 —

10 • 6 —

5 • 9 _

7 3 JL-t.!_.,?• 1 1 1 1 1 L 1 1 1 10 20 30 40 50 60 70 80 90 100

TIME TO PEAK RHR (s) [25 kW/m2 IRRADIANCEJ

Figure 11. Relationship between Time to Peak RHR

and Peak Floor Flux

47
SUPPLEMENTARY

SPECIMENS

CM

2

QOCO

12 11 25 22 17 20 16 23

18 2115 19 24 14

i i —i

“i 1 1 1 1 4

45 ~ Groups Group Group

A,B C 0

40

35

. 1 30

25

20

Point labels are

15 2

A « specimen numbers

5

10 « 6

5

•9 NBS-II DATA

7 3 8

0 L- Li I i i i i i 0 50 100 150 200 250 300 350 400 450

3- MIN. AVERAGE HEAT RELEASE RATE (kW/m 2

)

Figure 12. Rate of Heat Release Performance,

NBS-II Calorimeter

48
SUPPLEMENTARY

SPECIMENS

E

a

§

=i5

1 —r~

i

|

1 n 1 1

1

1 1 1 1 1 1

45

40

- Groups

A,B

1

1 Group C

1

i

1 Group 0 4

* ~

35 a

30

*1

25 -

20

Point labels are

15

10 6

2

. • 5

specimen numbers

5

* 9

i

OSU DATA

0 ,3 8 10

7 » * » _i i 1

i i i i i i 0 50 100 150 200 250 300 350 400 450 500 550 600

3-MIN. AVERAGE HEAT RELEASE RATE (KW/m2

)

Figure 13. Rate of Heat Release Performance,

OSU Calorimeter

49
I

Figure 14. Comparison of NBS-II and OSU Results

50
ELk. UJo

6 -

3

§ 2

0.01

Group D

J L

Point labels are specimen numbers

NBS-II DATA

J I I I I I I L

0.1 1.0 SMOKE PARAMETER

10

Figure 15. Smoke Performance (RHR Data from

NBS-II Calorimeter)

51
SUPPLEMENTARY

SPECIMENS

1 1 1—i—

|

25 17 12 18 21 • • • •

—i

11 • ••

19

-h 1 1

I13 •••

22 24

1

16 14 • •

20

1 1—i

23

•

Group A

1

1 Groups B, C Group D

4

•

6

1

1

1

»

\

5

2 -

h- • 5 6 « £

• 9

Irk M LU 4

- s

§

S3 8 z • 5 3

Lkl 5

“ 2 10 1

• 2 2 - O

Point labels are £

0•

specimen numbers

1 7 _ • OSU DATA

0

i i i i 1 _i _i i i L_ i_ i i i_

0.01 0.1 1.0 SMOKE PARAMETER

10

Figure 16. Smoke Performance (RHR Data from

OSU Calorimeter)

52
APPENDIX

TM

U±A A
PROPOSED TEST METHOD FOR INSTITUTIONAL MATTRESS FLAMMABILITY

1.

Scope

1.1 This method covers the procedures required to assign a performance classification for

the flammability of institutional mattresses. Mattress performance is limited to the

consideration of heat fluxes and smoke densities produced in a room containing an institutional mattress ignited by a flaming source. Mattresses are classified into one of four groups: A, B, C, or D, described in Section 3.

1.2 To determine the complete performance classification two tests are conducted — rate

of heat release and smoke production. To qualify mattresses for groups B or C only

the rate of heat release tests are required.

2.

Applicable Documents

ASTM Proposed Test Method for Heat and Visible Smoke Release Rates for Materials, ASTM

Annual Book of Standards, Part 18 (November 1980).

ASTM Standard ANSI/ASTM E662-79, Standard Test Method for Specific Optical Density of

Smoke Generated by Solid Materials.

3.

Significance

3.1 The test procedures described comprise bench-scale tests designed to correlate with

the fire behavior of institutional mattresses measured in full-scale tests. The fullscale conditions [1] consisted of instrumented rooms furnished solely with a test mattress, bedding, and a sustained flaming ignition source. The mattresses were

located in a typical sleeping use arrangement.

3.2 Hazard may be increased if mattresses are stored on end, stacked several high, shredded

or used in arrangements other than for sleeping use. Existing data suggest that in

many cases, however, the relative ranking may be preserved.

3.3 This method does not provide for test of resistance to ignition by cigarettes. Method

FF 4-72 [2] should be used to determine cigarette ignition resistance.

A2
3.4 Specimen performance is described primarily by categorization into four groups. The

groups have been determined from full-scale fire tests [1]. Appropriate performance

in bench-scale tests does not provide assurance that actual fire behavior will be

similar to that on which the categorization procedure was developed, due to differences

in actual use conditions.

3.5 The four performance groups, based on flashover potential and tenability limits for

carbon dioxide, carbon monoxide, oxygen depletion, heat flux, and smoke obscuration, are

Group A — Specimens in Group A did not cause any full-scale tenability limit to be

exceeded.

Group B — Specimens in Group B showed elevated smoke production in full-scale tests but

did not exceed other tenability limits.

Group C — Specimens in Group C exceeded smoke production and other tenability limits

but did not lead to room flashover.

Group D — Specimens in Group D exceeded all tenability limits and led to room flashover.

3.6 Repeatability has been determined in one laboratory for tests on the ten specimens

included in the full-scale tests and on an expanded set, augmented by an additional 15

specimens. The coefficients of variation for the initial set were 0.102 and 0.093 for

the rate of heat release and smoke production tests, respectively. For the augmented

set the values were 0.134 and 0.130.

4. Rate of Heat Release Tests

4.1 Apparatus. The apparatus shall be similar to that described in the document "Proposed

Test Method for Heat and Visible Smoke Release Rates for Materials," with the following

exceptions:

4.1.1 The smoke measurement portion of the method shall not be used.

4.1.2 The specimen shall be mounted in the horizontal position; millboard backing and

spring support shall not be used.

A3
4.1.3 A non- impinging gas pilot shall be used. A mixture of methane and oxygen shall be

fed to a burner tip located approximately 40 mm above the center of the specimen.

The burner tip shall have an orifice of 0.75 mm (Smith Welding Equipment 12-1401-05)

or equivalent and shall be oriented at approximately 45° to the specimen. The gas

mixture shall be adjusted to provide a small steady bright blue cone.

4.1.4 The radiation reflector shall be stainless steel foil, approximately 0.05 mm thick.

4.1.5 The thermopile measurement system shall not be used; instead, the heat release rates

shall be measured by oxygen consumption.

4. 1.5.1 An oxygen probe which consists of a stainless steel tube, 6.35 mm outside diameter,

0.89 mm wall thickness, shall be fitted horizontally 25 mm below the stack baffle.

The tube shall be approximately 120 mm long and will be attached to a bulkhead

fitting through the end chimney wall. Six equally spaced holes, 1.75 mm in

diameter, shall be drilled along the length of the top of the tube. The far end

of the tube shall be closed off.

4. 1.5. 2 The supplementary air supply to the top shroud of the apparatus shall be shut off.

The total air supply, all of which passes through the combustion chamber, shall be

12+2 Si/s. (This setting corresponds to approximately 340 mm H^O indication on

the standard orifice flow meter used with the instrument). Short term stability

shall be + 0.75 £/ s between time of calibration and time of test.

4. 1.5. 3 The oxygen sampling system shall consist of an oxygen meter, pump, filter, drying

device and carbon dioxide trap. A paramagnetic type oxygen analyzer has been

found suitable (Beckman 755 or equivalent). The instrument shall at least

encompass the range of 15% to 22% oxygen; a commonly available scale of 0-25% is

suitable. Electro-chemical or catalytic cells have not been found suitable.

Ascarite has been found suitable for trapping. To ensure rapid response the

sample line length should be minimized. A bypass (dumping) system should be used

to provide rapid flow through the sample line while staying within oxygen analyzer

flow rate limitation. A flow rate close to the maximum recommended by the manu- facturer is normally preferable.

Tescom Corporation, Minneapolis, MN

Beckman Instruments, Fullerton, CA

Arthur H. Thomas Co. , Philadelphia, PA

A4
4. 1.5.

4

If the oxygen analyzer is sensitive to the partial pressure of oxygen at the

outlet, tests shall not be conducted under conditions of rapidly varying ambient

barometric pressures. Oxygen analyzer calibration as specified in 4. 1.5. 5 should

be performed before and after each set of tests. Tests will not be considered

valid unless the second calibration is within 2% of the first one.

4. 1.5.5 Oxygen analyzer calibration. The oxygen analyzer shall be calibrated with ambient

air (21.0% dry volume basis oxygen) corresponding to zero depletion and with a bottled oxygen/nitrogen mixture for the second reference. This mixture shall be

in the range of 18.0 - 19.8% oxygen by volume. If the instrument response speed

is adjustable, it should be set using the calibration burner and adjusted for zero undershoot when gas flow is stopped.

4.2 Heat release rate calibration. Calibration shall be performed before each series of

tests and shall be made with a flow of methane through the calibration burner corres- ponding to a heat release rate of 4.0 to 8.0 kW. The calibration factor shall be

determined as

Ah pV

[C>2%] (1 + 0.0127 [02 %]) (kw/o2 %)

where Ah = lower heat of combustion of methane (50.0 x 10 kJ/kg)

c

p = density of methane at actual pressure and temperature (kg/in )

V = volume flow of methane (m

3 /s)

and [0

2 %] = percent oxygen reduction.

The given flow rate should be maintained for approximately 5 minutes to determine a steady value of the response.

4.3 Rate of heat release. The specimen rate of heat release shall be determined from the

measured oxygen reduction using the calibration factor determined in Section 4.2.

The release rate shall be expressed as

k[0„%]

, RHR = —y— (kW/m )

2 where A = exposed specimen area (m )

.

A5
4.4 Rate of heat release specimens. Specimens are to be cut from finished production

mattresses. Three specimens used, 100 mm by 100 mm along the exposed surface and

50 mm thick. Specimens are to be cut, through the thickness of the mattress, from an area least 20 mm away from any edge. If mattress construction is uniform over the

entire surface, then specimens may be removed from any convenient location. If con- struction is variable, three specimens shall be taken and tested from each different

area, with results being reported for that area showing the highest heat release rate. The arrangement of layers to produce a total specimen thickness of 50 mm shall be done

in the following way. Innersprings and other metal parts, if any, shall not be included

and their thicknessses not considered. If the remaining mattress thickness is less

than 100 mm, then the top 50 mm shall be used. (The top surface is that normally used

facing upward.) If the thickness is greater than 100 mm, then those layers which are thicker than 2 mm shall be trimmed in thickness to be in the same ratio as occurs in

the production unit. If the mattress construction incorporates an interliner or other

layer for flame barrier purposes, then that layer shall be cut sufficiently larger

than 100 x 100 mm to enable it to be wrapped completely down over the sides and stapled

underneath the specimen. The topmost layer (ticking) shall be 100 x 100 mm unless it is also included in a flame barrier construction. If the mattress contains highly

compressed filling material, such that more than 25% thickness expansion occurs when

the mattress is cut, the test specimen shall be sewn through with metallic wire in

sufficient places to allow it to assume its production density. The mattress specimen

shall be covered along the sides and bottom by a single sheet of aluminum foil,

approximately 0.04 mm thick, with the dull side in contact with the specimen.

4.5 Conditioning. Specimens shall be conditioned to equilibrium (constant weight) at an ambient temperature of 23 + 3°C and a relative humidity 50+5%.

4.6 Test Conditions. Test conditions shall be basically as given in the reference document

2 and as modified above. An irradiance of 25 kW/m shall be used. Three samples each

shall initially be tested. If any result in any set of three replicates is such that

it exceeds the minimum by more than 50%, test an additional set of three replicates

and report the average of all six results.

4.7 Calculations. The rate of heat release (RHR) shall be determined as required in

Section 4.3 and recorded at least every 5 seconds. An average rate of heat release

shall be determined for the time period comprising the first 180 s after ignition.

Ignition shall be defined as the initial time when an oxygen depletion of _> 0.05%

above the baseline is recorded (the baseline is the undisturbed oxygen reading prior

to test).

A6
5» Smoke Production Tests

5.1 Smoke production apparatus. Smoke production shall be measured in the apparatus

described in ANSI/ASTM E662 with the following exceptions.

5.1.1 Specimens will be tested in a horizontal position, flaming mode, using a load cell

for mass loss measurement. Figure A1 shows the arrangement used for accommodating

1

* horizontal specimens (Aminco Dl-76000 or equivalent) . The development of this

modification is given in reference [3],

5.1.2 Specimen size and arrangement shall be as given in paragraph 5.2.

5.1.3 Irradiance shall be measured at the specimen center location with a water-cooled

Gardon-type heat flux gauge having a view angle of approximately 180°. The heat flux

gauge shall be calibrated for incident radiation at a flux level appropriate to use

conditions.

5.1.4 A single tip pilot shall be used, producing a small controlled flame impinging on

the specimen center.

5.1.5 Photometer transmission and load cell data should preferably be recorded continuously,

but shall be at least once every 10 s.

NOTE: It has been found useful to obtain transmission data with the use of a

* logarithmic photometer amplifier, Optronic Laboratories Model 733 or equivalent.

5.2 Smoke production specimens. Three specimens shall be prepared similarly as in paragraph 4.4 except specimen size shall be 50 x 50 x 25 mm thick. Thickness proportioning

shall be used if mattress thickness is greater than 50 mm.

5.3 Test conditions. Test conditions shall be basically as given in the reference docu2 ment and as modified above. An irradiance of 25 kW/m shall be used. Three samples

each shall initially be tested. If any results in any set of three replicates is such

that it exceeds the minimum by more than 50%, test an additional set of three replicates and report the average of all six results.

^American Instrument Co.

*Optronic Laboratories

A7
5.4

Calculations.

5.4.1

The quantity to be determined from the test is a , the specific extinction area. This quantity is a measure of the smoke obscuration developed per unit sample mass

pyrolyzed.

5.4.2

The starting time, t = 0, is defined to be the time that the specimen is inserted

into the apparatus. At each 10 s thereafter the transmission and the mass are recorded. The specific extinction area, a , is then determined at each 10 s interval m

according to the relationship

am

k - k

= V

10

ch m^Q - m

(m

2 /kg)

3 -1

where V , = chamber volume (0.510 m ), k is the extinction coefficient (m ) at a ch

given time, k^ is the extinction coefficient at 10 s after start of test, m is the mass remaining (kg), and m^ is the mass at 10 s. The extinction coefficient k is

defined as

k = 2.303

L

where L = light beam path length (0.914 m) , T is the percent transmission, and In is

the base-e (natural) logarithm. The results are to be tabulated for every 10 s interval from 30 s to 600 s, inclusive. The a value reported for each specimen shall be m

the maximum in this period.

6. Performance Classification

6.1 To qualify mattresses for Group B or Group C only the rate of heat release tests,

Section 4, are required. Performance group is determined according to the average RHR

value, computed for the lot of three or six test specimens according to paragraphs 4.5

and 4.6.

6.2 Specimens with RHR greater than 200 are classified into Group D.

6.3 Specimens with RHR less than or equal to 200 qualify for Group C.

6.4 Specimens with RHR less than or equal to 100 qualify for Group B.

6.5 To qualify mattresses for Group A, both the rate of heat release tests, Section 4, and

the smoke production tests, Section 5, are required.

A8
6.5.1 The average RHR is computed for the lot of three or six test specimens according to paragraphs 4.5 and 4.6.

6.5.2 The smoke parameter (SP) is defined as

SP = o x RHR/10 5 m

where RHR is determined in Paragraph 6.5.1. The a value used in determining the m

smoke parameter, SP, is the average for the lot of three or six test specimens.

6.6 Specimens with RHR less than or equal to 100 and SP less than or equal to 0.25 are classified into Group A.

7. Report

The report shall include the following:

7.1 Description of mattress, including type, manufacturer, size, weight, presence of innersprings and other appropriate identifying features. Include observation if top and

bottom constructions are different and if samples are not uniform over their surface area

.

7.2 Description of test procedures.

7.3 Number and description of specimens tested.

7.4 The RHR value for each specimen and the average for the lot.

7.5 If smoke production tests were performed, the a for each specimen and the average for m

the lot and the SP value for the lot.

7.6 The performance group.

A9
References

1. V. Babrauskas, Combustion of Mattresses Exposed to Flaming Ignition Sources, Part I. Full-Scale Tests and Hazard Analysis, Nat. Bur. Stand. (U. S.) NBSIR 77-1290 (1977).

2. Standard for the Flammability of Mattresses and Mattress Pads (FF 4-72), 40 FR 59940,

CFR Part 1623.

3. L. Breden, M. Meisters, The Effect of Sample Orientation in the Smoke Density Chamber,

Nat. Bur. Stand. (U. S.), NBSIR 76-1030 (1976).

A10
!

i

All dimensions in mm

ELEVATION SAMPLE HOLDER

Figure Al. Details of Horizontal Specimen Holder and Load Cell

for the Smoke Density Chamber

All

APPENDIX B - SUPPLEMENTAL DATA ON HEAT AND

MASS FLOWS IN FULL-SCALE TESTS

Data analysis on heat and mass flows in the full-scale tests was not available at the

time of the publication of the Part I report [1]. For completeness this analysis for Burn

Room A is presented here.

Initial analysis of mass flows was performed using the procedures discussed in detail

in [14]. This involves using a doorway velocity profile as measured by six bi-directional

velocity probes. This approach showed a poor mass balance, with outflows up to double the

corresponding inflows. The analysis in [14] showed two basic difficulties: (a) six probes

are insufficient for adequate precision, and (b) the positioning of probes among the flow

streamlines is critical (a location has to be established where there is a negligible

verticle velocity component)

.

Relying only on existing data, a different approach was taken instead. Work by

Steckler [22] has shown that a good estimate of doorway mass flows can be made by equating

the actual doorway temperature distribution to an equivalent two-layer model. It is assumed

that the inflow air is of a known temperature T^. To be determined are the typical hot upper

gas (outflow) temperature, T , and the neutral plane height, N. Below the height N in the

doorway there is only inflow, at the temperature Tm , while above N there is only outflow at the temperature T . Two equations are used to solve for the two unknowns N and T^.

(

p (h)dh = Np + (H - N)p

and

f* A

(T (h) - T )dh = (H - N) (T - T )

oo VI °°

where T(h) are doorway temperatures measured at height h, H is the doorway height, and the

T densities p are expressed as p = p . T

The integration is approximated by a summation over, in this case, nine temperature

measurement locations. Once T^ and N are obtained, the mass flow rate can be directly

obtained using the procedures developed by Rockett [23]. In these calculations a discharge

coefficient = 0.77 was chosen according to experimental determinations consonant with

this approach [22].

B1

f
Rate of heat release determinations were made using the oxygen consumption principle

[8]. Only a single oxygen probe measurement location, near the doorway top, was available.

Exploratory probing indicated, however, that oxygen in the upper gas space is quite well

mixed and that it is reasonable to assume that all the outflow is at the same concentration

as measured by the single probe.

Results for mass flows and rates of heat release are shown in Figures B1 through Bll.

It should be noted that according to the analysis method adopted mass conservation is

implicitly included and, therefore, separate mass inflow and outflow values are not derived.

B2
Figure Bl. Heat Release Rate and Mass Flow for Control Mattress

B3

i,

MASS

OUTFLOW

(kg/s)
q,

RATE

OF

HEAT

RELEASE

(kW)

i

i

Figure B2. Heat Release Rate and Mass Flow for Mattress M01

B4

i,

MASS

OUTFLOW

(kg/s)
q,

RATE

OF

HEAT

RELEASE

(kW)

2500

2000

1500

1000

500

200 400 600 800 1000 1200 1400 1600 1800 TIME (s)

Figure B3. Heat Release Rate and Mass Flow for Mattress M02

B5

i,

MASS

OUTFLOW

(kg/s)
Figure B4. Heat Release Rate and Mass Flow for Mattress M03

B6

i,

MASS

OUTFLOW

(kg/s|
Figure B5. Heat Release Rate and Mass Flow for Mattress M04

B7

m,

MASS

OUTFLOW

(kg/s)
q,

RATE

OF

HEAT

RELEASE

(kW)

Figure B6. Heat Release Rate and Mass Flow for Mattress M05

B8

i,

MASS

OUTFLOW

(kg/s)
q,

RATE

OF

HEAT

RELEASE

(kW)

Figure B7. Heat Release Rate and Mass Flow for Mattress M06

B9

i,

MASS

OUTFLOW

(kg/s)
q,

RATE

OF

HEAT

RELEASE

(kW)

Figure B8. Heat Release Rate and Mass Flow for Mattress M07

BIO

i,

MASS

OUTFLOW

(kg/s)
q,

RATE

OF

HEAT

RELEASE

(kW)

200 400 600 800 1000 1200 1400 1600 1800 TIME (s)

Figure B9. Heat Release Rate and Mass Flow for Mattress M08

Bll

i,

MASS

OUTFLOW

fkg/s]
Figure BIO. Heat Release Rate and Mass Flow for Mattress M09

B12

MASS

OUTFLOW

(kg/s)
q,

RATE

OF

HEAT

RELEASE

(kW)

3.0

2.0

1.0

200 400 600 800 1000 TIME Is]

1200 1400 1600 1800

Figure Bll. Heat Release Rate and Mass Flow for Mattress M10

B13

i,

MASS

OUTFLOW

(kg/s)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. Publication Date

SHEET (See instructions) NBSIR 80-2186 February 1981

4. TITLE AND SUBTITLE

COMBUSTION OF MATTRESSES EXPOSED TO FLAMING IGNITION SOURCES PART II. BENCH-SCALE

TESTS AND RECOMMENDED STANDARD TEST

5. AUTHOR(S)

Vytenis Babrauskas

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

S. Type of Report & Period Covered

Final

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City, State, ZIP)

Sponsored in part by: U.S. Consumer Product Safety Commission

Department of Health and Human Services

10. SUPPLEMENTARY NOTES

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

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bl iography or literature survey, mention it here)

Ten mattress types were subjected to full-scale fire tests in the earlier part

of this project. Burning behavior was determined and hazard was assessed by

classifying into performance groups. In the present study bench-scale test

procedures were examined for suitability for classifying mattress combustion

behavior when exposed to flaming ignition sources. Several tests were examined,

and a test protocol was developed based on two procedures — measurement of rate

of heat release and smoke production. These procedures enable the performance

classification, as established by full-scale tests, to be reproduced by convenient

laboratory tests. Details are given for conducting the required tests and illustrative performance of some two dozen samples is recorded.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Bedding; beds; compartment fires; fire tests; health care facilities; heat

release rate; hospitals; mattresses; prisons; smoke production.

13. AVAILABILITY 14. NO. OF

PRINTED PAGES

[IT] Uni imited Q3 For Official Distribution. Do Not Release to NTIS

\ | Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

82

15. Price

[~yl Order From National Technical Information Service (NTIS), Springfield, VA. 22161 $9.50

USCOMM-DC 6043-P80

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