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PUBLICATIONS

NAT'L INST OF STANDARDS & TECH R.1.0

Furnishings - A Literature Review

With Commentary

John F. Krasny

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Fire Research

Gaithersburg, MD 20899

April 1987

U.S. DEPARTMENT OF COMMERCE

BUREAU OF STANDARDS

100

.U56

#87-3509

1987

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QC

NBSIR 87-3509

CIGARETTE IGNITION OF SOFT

FURNISHINGS - A LITERATURE REVIEW

WITH COMMENTARY

Research information Center

National bureau of Standards

Gaithersburg, Maryland 20899

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* LA Si C? m. ?7-5£b$

mi

John F. Krasny

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Fire Research

Gaithersburg, MD 20899

April 1987

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

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Director

Table of Contents

Page

List of Figures v

List of Tables vi

Abstract 1

1 . Introduction 2

2 . Cigarette Characteristics 5

2.1 Factors Which May Affect Cigarette Ignition Propensity 5 2.2 General Characteristics of Cigarettes 8 2.3 Free Burn Characteristics of Cigarettes 10

2.3.1 Cigarette Burn Temperature 11

2.3.2 Cigarette Burn Rate 15

3. Temperature and Burn Rate of Cigarettes Burning on Substrates ....... 23

3.1 Non-Combusting Substrates 23

3.2 Smolder-Prone Substrates 25

3.2.1 Investigators at the Massachusetts Institute of

Technology . . .• 26

3.2.2 Other Investigators 33

3.3 Ignition by Electric Heating Coils 37

3.4 Summary of Findings on Cigarette/Substrate Interaction ........ 39

4. Substrate Smoldering Mechanisms 41

4.1 Smoldering of Cellulosic Materials 42

4.2 Smoldering Flexible Polyurethane Foam 43

5 . Cigarette Ignition Behavior 46

5.1 Cigarette Ignition Behavior of Soft Furnishings ............... 46

5.1.1 Effect of Fabrics 49

5.1.2 Effect of Padding Material 53

5.1.3 Effect of Interliner or Barrier Materials 53

5.1.4 Effect of Welt Cord 54

5.1.5 Effect of Furniture Geometry 55

5.2 Cigarette Ignition Behavior of Wildlife Materials 55

5.3 Cigarette Ignition of Garments 56

6. Relative Ignition Propensity of Cigarettes

iii

57
Table of Contents (continued)

Page

7 . Conclusions 60

8 . Acknowledgements 61

9 . References . 62

Appendix A. Test Methods for Determining Cigarette Ignition Resistance

of Soft Furnishings

Appendix B. List of Patents

IV
List of Figures

Page

Figure 1. Temperature Distribution in a Cigarette During Free Burning ... 79

Figure 2. Test Arrangement for Crevice Tests 80

Figure 3. Time/Temperature Relationships Inside Cigarette Core in Air

and on Two Substrates 81

Figure 4. Time/Temperature Relationships Measured in Four Locations

Inside Cigarette Core 82

Figure 5. Time/Temperature Relationships at Fabric Surface and 20 mm

Inside Vertical and Horizontal PU - Printcloth ................ 83

Figure 6. Time/Temperature Relationships Inside Cigarette Core and 20 mm

Inside Vertical and Horizontal PU - Printcloth 84

Figure 7. Time/Temperature Relationships Inside Cigarette Core and 20 mm

Inside Horizontal and Vertical PU - Greige Duck Fabric ........ 85

Figure 8. Time/Temperature Relationships Inside Cigarette Core and 20 mm

Inside Vertical and Horizontal PU - Bleached Duck Fabric ...... 86

Figure 9. Time/Temperature Relationships at Various Locations Inside

Vertical and Horizontal PU 87

Figure 10. Arrangement for Inducing Ignition With an Electrical Heating

Coil 88

Figure 11. Time/Temperature Relationships Inside a Fabric Covered PU Block,

with Electric Heating Coil (Various Output) Embedded 89

Figure 12. Time/Temperature Relationships Inside a Fabric Covered PU Block,

with Electric Heating Coil (15.5 kW/m2

) Embedded 90

Figure 13. Schematic Drawing of Smolder Wave in Fabric Covered PU Block,

with Electric Heating Coil (15.5 kW/m2

) Embedded 91

Figure 14. Mini-Mockup Test Arrangement for Cigarette Ignition ........... 92

v
List of Tables

Pane

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Table 6.

Table 7.

Table 8

.

Data Bases Searched . . . 71

Summary of "Fire Safe" Cigarette Patents 72

Characteristics of Commercial Cigarette Packings. Cigarette

Packings Acquired about 1980 73

Characteristics of 32 Commercial Cigarette Packings. Cigarette

Packings Acquired About 1971 74

Cigarette Temperature and Heat Flux Results with the Cigarette

Resting on a Copper Plate 75

Upholstered Furniture Components Listed in Approximate Order

of Descending Cigarette Ignition Resistance 76

Typical Cigarette Ignition Test Results . 77

Cigarette Ignition Resistance of Typical Fabric/Padding

Material Combinations 78

vi
CIGARETTE IGNITION OF SOFT FURNISHINGS

A LITERATURE REVIEH HITH COMMENTARY

J ohn F . Krasny

Abstract

Literature pertinent to the ignition by smoldering cigarettes of

upholstered furniture and mattresses (soft furnishings) was searched through early 1986. This included literature on the

smoldering behavior of cigarettes in air; their behavior on a variety of substrates simulating soft furnishings; mechanism of

smoldering in substrates; relative cigarette ignition resistance of

substrates; and relative propensity of commercial cigarette

packings to ignite substrates. According to the reviewed

literature, the smoldering behavior of cigarettes on substrates

differs from that of cigarettes burning in air: on substrates,

cigarette temperatures tend to be lower, and burning rates slower . These differences seem to be larger for substrates which ignite

than for those which self-extinguish after the cigarette burns out.

The characteristics of soft furnishings which insure resistance to

cigarette ignition have been established, but those of cigarettes

with low propensity to ignite furnishings have not. No

mathematical model has been reported for the interaction of

cigarette and substrate, but some empirical data do exist.

Keywords: Cigarette combustion; flammability tests; ignitability

of soft furnishings; mattresses; smoldering combustion; upholstered

furniture

.

1
1 . INTRODUCTION

This literature survey was undertaken as part of the overall program

mandated by the Cigarette Safety Act of 1984 [1]. The Act seeks a reduction in

the losses from fires caused by cigarettes inadvertently dropped on mattresses

or upholstered furniture (soft furnishing substrates 1

) by modifying the

ignition2 propensity of the cigarette. The 1984 estimates for cigarette - caused

fire incidents in residences are as follows: 49,000 structural fires (7.9

percent of total), 1530 civilian deaths, 3950 civilian injuries, and 320

million dollars property loss (36, 19, and 9.3 percent of total, respectively)

[2,3]. While the number of cigarette-caused fires have decreased over the last

few years, they still represent the largest single cause of residential fire

death.

1 A soft furnishing substrate is a combination of cover fabric and padding

material, with or without welt cord, in either the flat or the crevice (juncture of a horizontal and vertical furniture member) area. For example, the

flat area of a piece of polyurethane foam covered with a cotton cover fabric;

the crevice from the same material will be considered another substrate for the

present purposes, as would be the same substrate but with the cigarette covered

with a piece of sheeting, as is often used in testing the cigarette ignition

propensity of soft furnishings (Appendix A)

.

2 Ignition in this review will mean self-sustaining smoldering of the

substrate; such smoldering may or may not lead to flaming. The term "selfextinguishing cigarette" has been widely used in many discussions of cigarettes

with a low ignition propensity [e.g., 5]. However, even cigarettes which

sometimes self -extinguish in air can ignite low cigarette ignition resistance

substrates, as can some hand-rolled cigarettes which also commonly selfextinguish when not smoked [6-8]. Conversely, some cigarettes may burn their

entire length without igniting high cigarette ignition resistance substrates.

Consequently, we shall use, instead, the term "low ignition propensity"

cigarettes in the following discussion. This term includes, but is not limited

to, cigarettes which self -extinguish on a substantial number of substrates.

2
About 600 billion cigarettes are presently consumed in the U.S. annually

[4]; this means that only about one in 12 million cigarettes causes a fire. It

is not often possible to identify the cigarette packing3 or substrates from the

accident reports. To identify specific properties that may be involved as

causative factors, one has to rely on laboratory simulations of cigarettecaused ignitions. Much more work has been done in the area of identifying soft

furnishing characteristics which increase their cigarette ignition resistance

(Section 6) than on identifying cigarette characteristics which reduce

cigarette ignition propensity. One study of the relative propensity of

selected commercial cigarette packings to ignite soft furnishings mockups has

been completed under the Cigarette Safety Act [6], A systematic investigation

of the effects of certain cigarette parameters on their propensity to ignite

soft furnishings is currently in progress.

The purpose of this literature survey is to provide a review of sources

dealing with cigarette properties, substrate properties, and their interaction

which may aid in the understanding of the mechanism by which cigarettes ignite

substrates. It was written for readers having some familiarity with the field.

Relevant patents are listed in Appendix B.

Thirteen data bases were searched as shown in Table 1, Also searched

were sources not included in these data bases, e.g., special reports dealing

with characteristics of cigarettes and soft furnishings and wildlife fires

.

Approximately 300 documents were initially identified; only about a third

A cigarette packing is usually defined as a commercial variety, described

by its name, length, diameter, whether menthol or non-menthol, whether with or without filter, and by its packing type.

3
turned out to be germane to even a broad interpretation of the objective of

this survey. Indeed, very little research has been published that directly

relates cigarette combustion to substrate ignition mechanisms.

One group of publications gathered for this survey was written by authors

associated with the tobacco industry. It contains substantial information on

such cigarette characteristics as burn rate and temperature of the burning

cigarette. Among the variables discussed are tobacco type, cigarette dimensions and packing density, filter parameters and paper porosity, and additives.

The major objective of these publications seems to be to obtain basic understanding of the burning cigarette, with emphasis on reduction of tar, nicotine,

CO, and other smoke components. Some of these papers are discussed below for

general information on the burn process of cigarettes. However, because of

their purpose, they have two major limitations for the present objective: (a)

most of the data were obtained during the puff, while furniture and wildlife

material ignition by a cigarette would be during the "free burning" period, and

(b) the results were obtained with the cigarette held in air, not in contact

with a substrate where oxygen exclusion, heat sink effects, re-radiation from

the substrate, etc. can affect the progress of the cigarette burn and its

energy transfer to the substrate.

Another large number of publications deals with the cigarette ignition

resistance of soft furnishings. Test methods used to determine the cigarette

ignition resistance of soft furnishings are listed in Appendix A. A discussion

of papers on such test methods and the relative cigarette ignition resistance

of various upholstery materials such as fabrics, padding, welt cords, decking,

4
etc., is included in a recent review of all aspects of soft furnishings

flammability [9] and is summarized in Section 6. However, most of this work

was performed with one "standard" cigarette, with only the substrates varied.

Relatively few reports describe experiments with more than one cigarette

packing [6,7,8,10-17] (commercial cigarettes), [18,19] (research cigarettes).

About 100 patents have been issued which claim to reduce ignition

propensity (Table 2 and Appendix B) . Concepts in these patents include

chemical modification of the tobacco column or paper by means of various

additives, insulating material around the cigarette, obstacles to smolder

progress in the tobacco column or on the paper, etc. Evaluation of these

patents is beyond the scope of the present survey.

In the following, some basic cigarette characteristics will be discussed

first, followed by the interaction between cigarettes and substrates. Then

models of substrate smoldering and the relative cigarette ignition resistance

of substrates will be discussed. This will be followed by a discussion of the

relative ignition propensity of cigarettes.

2. CIGARETTE CHARACTERISTICS

2.1. Factors Which May Affect Cigarette Ignition Propensity.

As an aid in understanding the general trend of this review, some of the

factors which the author thinks may affect the ignition propensity of

cigarettes are listed below. Some of these factors are interrelated.

5
• Cigarette length. The tobacco column length affects the time a cigarette

burns and thus the probability of it being dropped and causing ignition.

(Since it takes some conscious effort to light a cigarette, one may

assume that a short burn time reduces the probability that the smoker

becomes inattentive and drops the cigarette stub. Even if he does, the

time available for ignition of the substrate is likely to be shorter.)

• Burn rate: This is presented as a change in length or mass with time.

Whether a cigarette is burning in air or is being puffed, the burn rate

affects the remaining cigarette length and thus the probability of

dropping the cigarette and of ignition. In addition, burn rate of

cigarettes on a substrate, which may be lower than that in air, affects

length of exposure of the substrate and the probability of ignition.

• Cigarette diameter. A decrease in cigarette diameter reduces the contact

area between the cigarette and the substrate and reduces the available

fuel

• Packing density. Lower packing density (attained primarily by the use of

expanded tobacco but also affected by the tobacco blend and cut width,

i.e., the width of the tobacco strands) reduces the mass of available

fuel

6
• Tobacco type. The tobaccos used in various cigarette packings may vary

in heat yield and burn rate due to variations in tobacco blend

constituents and ratios, as well as in types and concentrations of

flavorings and humectants

.

• Paper parameters. Paper parameters cause differences in cigarette heat

yield and burn rate. The paper permeability affects the flow of oxygen

from the outside air to the combustion zone and the diffusion of

pyrolysis gases from this zone to the outside. Chemicals are added to

the cigarette paper as smolder accelerants or retardants and to modify

the appearance of the ash [20].

® Filter characteristics. The presence and nature of filter tips also

affects the flow of air through the cigarette [21]. Additional

perforation is often provided in the paper covering the filter, reducing

the flow of air through the tobacco column (ventilation; this is used to

reduce the exposure of the smoker to smoke components) . To compensate

for the resulting change in combustion product yield or taste, other

properties may be modified when a filter is added. Absence of a filter

causes an increase in heat yield at the butt end [22],

The following factors, while not cigarette properties, are integral to

any laboratory study of cigarette ignition of soft furnishings;

• Spatial time-heat flux profiles of the smolder front passing over a

substrate. There are no references to this profile in the literature.

7
® Contact of cigarette and substrate. This is at least partially determined by the cigarette diameter, as noted above. Other factors are the

substrate surface characteristics and any intumescent behavior of the

cigarette paper, its ash, or the fabric, which could have an insulating

effect

.

• Substrate characteristics. Only some soft furnishings containing

cellulose in either the fabric or the padding (cotton batting padding) or

both, some acrylic fabrics, and some wildlife materials are susceptible

to cigarette ignition. Both fabrics and wildlife materials must be of a

certain minimum thickness and be fairly tightly packed.

* Ambient conditions. Ambient wind speed, relative humidity, and temperature, as well as moisture content of the substrate and perhaps of the

cigarette may have an effect on ignition propensity.

2.2. General Characteristics of Cigarettes

Most commercial cigarette packings have been found to be quite similar in

cigarette and tobacco column properties, except for considerable variation in

length, paper properties and perhaps in tobacco type. The details are given

below

.

The largest study of the variability of some of the parameters of 128

commercial, U.S. cigarette packings was performed by Countryman of the U.S.

8
Forest Service about 1980 [23]. His original premise was that certain cigarette packings are less effective initiators of wildlife fires than others. The

length, diameter, weight, packing density, materials extractable with acetone

such as crude fat, waxes, and gums, heating value (measured in a Parr adiabatic

oxygen bomb) and ash content were determined. However, Countryman's work was

terminated before these findings could be related to the ignition propensity of

the cigarette packings.

Table 3 shows that most of the above cigarette and tobacco properties

varied over less than a factor of two for the various cigarette packings, with

much of that range due to the variation in cigarette length. The similarity of

most cigarette packings was also mentioned in tobacco industry communications

e.g., [5]. Acetone extractives are an exception; they exhibit both a wider

range and a higher coefficient of variation. (The relevance of acetone

extractives to burning characteristics is not obvious but they are listed here

to illustrate the differences in tobacco column characteristics)

.

On the other hand, the cigarette paper varied considerably. The relatively large variation of paper weight as percentage of cigarette weight

indicates differences in thickness or density (some of it is caused by tobacco

column density variation) . The variability of paper heating value and ash

content per unit length indicates that the nature of the paper may also have

varied. Furthermore, the heating value of the paper was found to be only about

70 percent of that of the tobacco, and its percent ash content considerably

higher than that of the tobacco.

9
Countryman stated that the probability of wildlife matter ignition from a

single cigarette is low, as compared to that from other sources such as matches

and firebrands, (His reasoning also applies to soft furnishings). Reasons

given for this low ignition propensity are the low weight/volume ratio for

cigarettes, the fact that they smolder rather than flame, and that the contact

between cigarette and substrate is limited by the round configuration of the

former as well as the natural roughness of the substrate. The author also

states that the paper ashes first and may provide an insulating layer between

coal and substrate.

Loftus [22] published similar results for 26 filter and 6 non- filter

cigarettes purchased in 1972. They are summarized in Table 4. He found

somewhat different cigarette dimensions than Countryman found eight years

later, but again found relatively small differences among the commercial

cigarette packings he tested for the properties he measured.

2.3 Free Burn Characteristics of Cigarettes

Temperatures and burn rates of cigarettes in air have been widely

reported. The absolute results for temperature depend on details of the

measurement procedure, (location in coal, e.g., whether along the central axis

or periphery; thermocouple size and orientation) but about 850°C seems to be

the maximum reported for the period between puffs. It is not clear whether the

lower temperatures reported in many studies are due to differences in the

manner in which they were measured or are real results; the necessary details

for clarifying this are frequently lacking. Consequently, reported temperature

10
results obtained by various investigators can, at best, only be used for

comparisons within each study, not between studies.

Burn rates between puffs reported in the literature ranged from 4 to 6

mm/min in still air. It should, however, be kept in mind that cigarette burn

temperature and burn rate are greatly affected by presence of a substrate, as

will be discussed in Section 3. Work conducted under the Cigarette Safety Act

at the time of this writing attempts to clarify this phenomenon further.

2.3.1 Cigarette Burn Temperature

Laboratories connected with the tobacco industry have published some very

sophisticated studies of cigarette temperatures. The majority of their results

were obtained during the puff on smoking machines. For reasons given earlier,

this survey will concentrate on the measurements obtained during free burning

of the cigarettes, i.e., of cigarettes suspended in air between puffs. Some of

the studies from laboratories outside the cigarette industry use less sophisticated methods but are reported here because they contribute concepts of

possible interest [24-32]

.

A number of temperature measurement methods have been used: thermocouples

inserted into the cigarette, optical pyrometry, infrared photometry, and X-ray

scanning of beads embedded in the tobacco which melt at various temperatures.

Most of these experiments were carried out with thermocouples. The effect of

thermocouple size is discussed in a review article, as follows [24]. In one

series of experiments, a decrease in thermocouple wire diameter from 0.100 to

11
0.025 mm increased the measured peak temperatures in cigarettes by 127°C. In

another study, reduction of the thermocouple wire diameter from 0.20 to 0.05 mm

increased the peak temperature readings from 656 to 812° C; No further increase

in temperature was found with further decrease in thermocouple size. Based on

the first study, it appears that accurate measurements of coal temperature

require that thermocouples be no larger than 0.025 mm.

Presented below are the relative effects of various parameters on peak

temperatures reported by several authors. The absolute temperatures reported

by these authors may differ because of the differences in measurement methods

and thermocouple sizes. Temperatures were generally measured on the center

line of the cigarettes.

Table 3 contains Countryman's temperature data for some of the 128 >

cigarette packings, measured with 0.125 mm chrome 1/alumel thermocouples located

at the center of the cigarettes or touching their periphery [25]. The cigarettes were held horizontally in air flowing at 1.3 m/s in the direction of the

smolder front movement. The average temperature obtained with this size

thermocouple at the surface was 470° C, and in the center 770° C. Countryman

found that wood starts smoldering at or above 232°C. The time intervals over

which the thermocouples indicated temperatures above this value averaged 100

seconds for the center and 80 seconds for the surface of the cigarettes.

In 1956, another investigator measured free burning temperatures of

commercial cigarettes, and found an average center peak temperature of 730 °C

and an average periphery temperature of 565°C [26], With the cigarette

12
insulated with glasswool - to obtain maximum possible temperatures supposedlysimulating the cigarette inside, e.g., a waste basket - the temperatures were

620 and 570°C, respectively.

Egerton, et al. , using the optical records of beads with differing

melting points embedded in the tobacco, found a peak free burning temperature

at the apex of the core of 820° C, while the maximum at the periphery was about

616°C [27]

.

Boyd, et al.

,

reported free burning and puff temperatures for a number of

cigarettes in 1972 [29]. For (presumably British type) cigarettes, peak free

burning temperatures were about 785°C, and puff temperatures, 820 to 850°C.

The corresponding temperatures for hand rolled cigarettes were 620 and 780°C,

and for cigars, 600 and 680° C. A certain pipe tobacco free burned in the pipe

(with some puffing to keep it burning) at 640° C; the same tobacco free burned

in a cigarette at 790°C. Boyd also found that puff temperatures of cigarettes

from Australia, Great Britain, Denmark, France, Japan, and the U.S. were within

the range of 800 to 900° C.

Gugan calculated that tobacco combustion would occur at about 1200°C with

all the ash in place, and 820°C without the ash cover of the smolder cone [30],

His actual measurements produced lower values, about 820°C with the ash in

place. He ascribed this to cooling by conduction through the ash, to the

convective air flow pattern at the smolder cone, and to subsequent radiation

and convection losses

.

13
By use of infrared photometry, peak peripheral puff temperatures of

typical cigarettes were found to be 830-900°C, and free burning temperatures

about 700°C when the ash was partially removed from the smolder cone [31].

With the ash in place, the results were 830-900°C, and 500-600°C, respectively.

Peak peripheral puff temperatures for cigarettes made with 100 percent Bright,

Burley, and Turkish tobaccos varied only from 908-928°C.

Alteration of burn temperature was considered as a means to reduce the

polynuclear aromatic hydrocarbons in the smoke [32]. However, a wide range of

tobacco additives, in concentrations of up to 50 percent, including free

radical inhibitors and initiators, organic and inorganic salts, a number of

inorganic compounds including lead borate glass, certain catalysts and flame

retardants, had only minor effects on puff peak centerline temperature.

In contrast to the previous papers which contained temperatures measured

only in one or two locations, Baker published several profiles of temperature

distributions in British cigarettes [28], A free burn profile is reproduced in

Figure 1; it gives temperatures separately for the gaseous and solid phases in

the burn cone. The solid phase temperatures were measured by means of an

infrared probe, the gaseous phase temperatures by means of thermocouples. He

found relatively small differences between the solid and gaseous phase

temperatures at any location. The maximum temperature measured - at the center

of the cone, approximately 2 mm from its apex - was 775° C, at the periphery,

somewhat greater than 500° C. The distances between the isothermic zones at the

periphery are of interest. At the cigarette surface, the 500°C gas and solid

temperature zones extended from approximately the paper burn line to 2 mm into

14
the smolder cone. The corresponding distances for the 300° C or higher solid

phase zone were 3 mm from the paper burn line towards the butt end to 5 mm into

the smolder cone for the solid phase. For the gaseous phase, the corresponding

distances were 1 and 8 mm. As will be discussed later, burn cone geometry and

very probably temperature distribution change when the cigarette is in contact

with a substrate.

2.3.2 Cigarette Burn Rate

Burn rate is of interest to the cigarette industry because it affects the

number of puffs per cigarette, levels of smoke constituents, and other properties. A fast burn rate was also often hypothesized to correlate with

increased ignition propensity. However, results of experimental work conflict

with this concept [6,19], Ignition of a substrate requires not only a critical

heat flux but also a critical exposure time. As will be discussed in Section

4, below, the cigarette burn rate is altered by the presence of a substrate.

Free burn rate is briefly discussed here because it can be considered a basic

characteristic of cigarettes.

This discussion is based primarily on several major studies [33-37].

American and Hungarian type cigarettes are discussed. In three of these

studies, the burn rate was measured on horizontally suspended cigarettes.

Rice's study was conducted on Canadian cigarettes containing essentially all

bright tobaccos; vertical cigarettes were tested with the burn moving downwards

[37], The effects of various parameter changes were generally found to be

similar in all studies.

15
The basic device for measuring cigarette burn rate consists of a holder

for the butt end of the cigarette, trip threads touching the horizontal

cigarette (usually 40 mm apart) , and a timer to determine the interval at which

the threads break [33]. Burn rate measured without puffing is called the

"free" or "static" burn rate. Linear burn rate is usually expressed in mm/min

and mass burn rate in mg/min. The latter is usually calculated from the linear

burn length and the packing density.

Corbet and Schurer described an apparatus for measuring the burn rate of

cigarette paper separately, with bottom ignition of vertically held specimens

[38]. Burn velocities of 155 to 215 mm/min were observed; these velocities are

greatly in excess of those of cigarettes. Some of the papers did not burn.

The burn rate of 14 filter and three non- filter U.S. cigarettes, sampled

in 1980, varied from 4.1 to 5.9 mm/min [39], By contrast, rates of 1.8 to

3.6 mm/min were reported in 1930 [16,17]. With the coal ends down, the burn

rate of a 1980 cigarette packing increased by 30 percent, with the coal end up,

it decreased by 6 percent [39]. An increase in external air movement in the

direction of the burn from 3.2 to 9.0 km/hr increased the linear burn rate from

5.0 to 8.0 mm/min. A further increase in wind speed decreased it slightly to

7.5 mm/min. Wind perpendicular to or against the burn direction extinguished

some of the cigarettes.

Japanese investigators found no significant differences in horizontal and

vertical (coal end down) burn rates for cigarettes from three packings [14].

16
The method by which these somewhat unexpected results was obtained was not

described in detail. The burn rates of these cigarettes were not affected by

the packing densities indicating that other, non-disclosed factors affected the

burn rate. The ignition propensities of these cigarettes on a number of

upholstery substrates did not vary significantly.

Ninety- five cigarette packings available in Germany in 1982 had burn

rates from 2.1 to 5.1 mm/min [40], This is a lower range than that given for

U.S. cigarettes. This may be a true finding or may be due to a difference in

the measuring method, which is not described in the German paper. A specially

low burn rate was found for some oval cigarettes.

Rice found the mass burn rate to be directly proportional to the cigarette circumference for any one tobacco blend/paper combination [37]. Resnik,

et al .

,

reported that an increase in circumference from 23 to 26 mm decreased

the linear burn rate from about 5.5 to 4.7 mm/min and increased the mass burn

rate from 62 to 77 mg/min [33,34]. Arany-Fuzessery , working .with Hungarian

cigarettes, found similar effects of the diameter on the two burn rates [36].

Resnik, et al.

,

found that the mass burn rate was generally not affected

by packing density [33,34]. The linear burn rate was approximately inversely

proportional to packing density, with an increase in packing density from 0.22

to 0.36 g/cin3 producing a decrease in linear burn rate from 6.7 to 4.2 mm/min.

17
Resnik, et al. , also found that cigarettes made from three tobacco types

to the same firmness (which may have resulted in different tobacco column

weights) differed in burn rate, as follows [33]:

Burn rate

Tobacco mm/min mg/min

Turkish 3.3 52

Bright 5.3 69

Burley 6.2 77

Increasing the cut width from 0.4 to 1 mm resulted in a decrease of burn

rate from 6.0 to 5.2 mm/min [35]. For a Hungarian tobacco blend, an increase

in cut width from 0.57 to 1.19 mm decreased the linear burn rate by

approximately 8 percent and the mass burn rate by 17 percent [36]. Rice, et

al. , found that an increase in cut width from 0.35 to 0.61 mm decreased the

mass burn rate from 66 to 54 mg/min [37].

The paper characteristics can be adjusted to modify the cigarette burn

rate somewhat. The major variables used for this purpose are: fiber composition, weight and bulk density, the type of filler and its concentration and

distribution throughout the paper, air permeability*1 or porosity, and smolder

promoting chemical additives [20,41,42]. Permeability is generally expressed

as "CORESTA", in cm3 /min • cm2

• cbar ; it increases with increasing air

permeability. Alternatively, air permeability is often expressed in older

4 "Permeability" shall be used as a term for air passage due to both "inherent

porosity" which can be regulated in paper manufacture, and post-paper forming

(mechanical or electrostatic) perforation.

18
literature as a "Greiner" number, i.e., the number of seconds required for

50,000 mm3 of air to pass through 1,950 mm2 of paper5

. Consequently, the

higher the Greiner number, the lower the porosity.

Permeability can be increased by electrostatic, laser, or mechanical

perforation of the paper. Other means are used to vary the "inherent porosity"

such as manipulation of the fibers during paper forming, reduction of paper

weight, and/or use of paper fillers, e.g., CaC03 [20]. These methods have

different effects on burn rate: increasing the porosity mechanically does not

affect the mass burn rate, while increasing the inherent paper porosity

increases both the linear and mass burning rates [33-37,42], However, beyond a

permeability of about 80 cm3 /min- cm2

• cbar , no additional increase was found

[36]. These relationships held for widely varying cigarettes.

An empirical formula for computing the effects of the cigarette property

changes on the mass burn rate was proposed by Rice, et al . . [ 37 1 :

[Bw + 0.70 (Mw - M) + 0.34 (Pw - P) 0.17 (Tw - T)] ( 1 )

where B - "predicted" rate of burn, mg/min

Bw = rate of burn of "measured" cigarette, mg/min

C = circumference of "predicted" cigarette

Cw = circumference of "measured" cigarette

M = moisture content of "predicted" cigarette

Mw = moisture content of "measured" cigarette

P = paper porosity of "predicted" cigarette

Pw = paper porosity of "measured" cigarette

T - cuts per inch of tobacco of "predicted" cigarette

Tw = cuts per inch of tobacco of "measured" cigarette

5 CORESTA 10 corresponds roughly to a Greiner 45 reading; 30 to 18; 50 to

12.5; and 70 to 10.

19
By correcting for packing density, equation 1 can be readily modified to make

possible the prediction of linear rate of burn:

T r Bl = [Bw + 0,70 (Mw - M) + 0.34 (Pw - P) - 0,17 (Tw - T) ] (2)

where L = length of "predicted" cigarette (tobacco portion only)

W = weight of "predicted" cigarette (tobacco portion only)

Bl = linear rate of burn, as mm/min

These formulas were confirmed by actual burn rate measurements on experimental cigarettes with two levels of each of the following variables: cigarette

weight, circumference, cut width, moisture content, and paper porosity [37].

Other parameters also have been reported to have an effect on the burn

rate, including relative humidity and smolder promoters or retardants. Three

studies showed that burn rate decreases with increasing cigarette moisture

content, while cigarette temperatures are not found to be greatly affected

[15,35,43]. When conditioned at 20°C and 67 percent relative humidity, a

commercial cigarette burned at 4.8 mm/min; at 28°

C

and 25 percent relative

humidity, at 5.6 mm/min [39]. Another author reports a burn rate decrease of

12 percent with an increase in moisture content from 12 to 16 percent, and the

temperature constant [33]. Rice, e_t al. , showed that an increase in moisture

content of cigarettes from 4 to 20 percent caused a decrease in vertical mass

burn rate of 10 mg/min for three cigarettes varying in tobacco type and thus

burn rate [37]. However, increasing concentrations of two humectants added to

20
the tobacco, from 0.2 percent glycerol and 0.2 percent propylene glycol to a

1.4 percent concentration of both humectants produced the following small

effects: increase in moisture content from 11.3 to 11.9 percent, free burn rate

increase from to 4.9 to 5.3 mm/min, and mass burn rate increase from 61 to 66

mg/min[ 33 ]

.

Tobacco additives have been studied widely. Below we present summaries

of some of these studies. In one of these, the same concentration of cations

was added to all experimental cigarettes [41], The effects on free mass burn

rates were as follows, in descending order:

For Na-salts: bicarbonate = carbonate>nitrate>phosphate , dibasic

phosphate, chloride>sulfate>monobasic phosphate;

for nitrate and acetate, the order was Na>K>Li>Ca>Mg>NHA

. Ca, Mg, and

NH4 nitrates could not sustain the smolder of a model cigarette by

themselves

.

By the further addition of K-malate (K, 0.5 percent) or Na-malate (Na,

1.0 percent) as a coexistent salt, the order of the burn rate retarding

effect of NHA -salts was sulfate>chloride>nitrate>carbonate = acetate.

Chemical additives to the paper can be mixed with the cellulose slurry as

fillers or applied as coatings to the paper surface in the form of very fine

crystals [20]. Such chemicals can be used to affect burn rate or to affect the

21
nature of the ash, e.g., white or mottled appearance. Some that were tested in

the laboratory are listed below [20],

Burn Accelerators

Ash

Conditioners

Burn

Retardants

Alkali metal citrates

Alkali metal tartrates

Alkali metal acetates

Alkali metal malates

NH,H2 P0a UreaNaB03 Na2 B* 0 7 Na7 Mo07 AlCig

Alkali metal formates

Alkali metal phosphates

Alkali metal nitrates

Alkali metal sulfates

Alkali metal carbonates

Alkali metal halides

Citrates and phosphates are the most widely used additives to today's

cigarette papers. On paper which had burn rates of 4.0 mm/min and 53 mg/min

when untreated, a 2' percent concentration of sodium citrate raised the burn

rates of cigarettes to 5.5 mm/min. and 72 mg/min, while other citrates had less

effect. Similar burn rate increases were observed when certain phosphates (1

percent PO^ "

)

and sodium salts (0.5 percent Na+

) were added to the paper [34].

In summary, the effects of changing the inherent and mechanically or

electros tatically- induced paper permeability and of modifying chemicals on the

free burn process have been extensively studied empirically, but are not well

understood [20,42]. The effect of some of these factors on ignition propensity

has been investigated as part of the work under the Cigarette Safety Act and

will be reported in the near future.

22
The following is a qualitative summary of the effect of cigarette

construction variables on burn rate:

Increase in

Effect on Burn Rate

Linear, mm/min Mass

,

mg/min

Cigarette

circumference

moisture content

Tobacco3 packing density

cut width

Paper

permeability

inherent

mechanical

citrate content

decrease

decrease

increase

decrease

decrease no effect or decrease

decrease decrease

increase13 no effect

increase

increase13 no effect

increase

a Tobacco type and additive (humectants , etc.) content also affect burn rate,

b No effect beyond 80 CORESTA.

3. TEMPERATURE AND BURN RATE OF CIGARETTES BURNING ON SUBSTRATES

3.1 Non -Combusting Substrates

The temperatures at the center lines of 26 filter and 6 non- filter

cigarettes placed on asbestos board were measured in 1972 by Loftus [22] using

0.05 mm chrome 1/alumel thermocouples. The average results, along with some

physical property data, are shown in Table 4. Loftus reported that there were

no differences between peak, center line temperatures in the filter and nonfilter cigarettes when measured at 25 and 51 mm from the butt end. At 3.2 mm

from the butt end, the non- filter cigarette temperatures were on the average

36°C higher than the filter cigarette temperatures.

23
A similar study had been carried out in 1969 by Behnke . He used a highly

conductive, 0.075 mm thick, copper sheet (size not given) as the substrate,

with 0,25 mm chrome 1/alumel thermocouples attached to the copper plate [9-3],

Obviously, a copper sheet differs considerably in heat conductivity and ether

characteristics from fabrics used in upholstery, but Behnke ' s work may still be

valid for comparison of the properties of various cigarette packings. The

filter and non-filter cigarettes were preconditioned by drying at 110°C for 16

hours followed by desiccating at room temperature for 8 hours. Some were

tested dry, immediately after removal from the desiccator, and others after a

further conditioning at 24°C and 65 percent relative humidity. The cigarette

temperatures and heat flux (as measured by the temperature rise of the copper

plate) results for 16 cigarette packings are summarized in Table 5. The

temperatures were much lower than those measured by Loftus with the cigarettes

resting on the asbestos sheet with the thermocouples in contact with the

cigarette. For comparison, Behnke reported conditions at which a cotton fabric

(undefined) was found to ignite under several experimental conditions: in a

heated vessel at 385°C; on a hot plate at 465°C; and in contact with a hot wire

at 518°C. A radiant exposure of 28 kW/m2 for 30 seconds (equivalent to a black

body temperature of about 560° C) also ignited the fabric.

We conclude the following from Behnke ' s work:

* There were no consistent effects on burn temperature or heat flux due to

drying the cigarettes. This has also been reported by others for

temperatures inside cigarettes [15,35].

24
• There were no systematic differences between the filter and non- filter

cigarettes; since these were commercial packings, parameters other than

the presence or absence of a filter undoubtedly were also varied.

• The temperatures and the heat flux levels measured on the copper sheet

are sufficient to account for ignitions of cellulosic soft furnishings

and wildlife [2.5], even though the reported values are probably lower

than actual peak values.

3.2 Smolder- Prone Substrates

Below is a review of temperatures measured inside cigarettes, at their

interface with substrates, and inside polyurethane substrates. The core

temperatures of cigarettes were found to be lower when they burned on smolderprone substrates than when they were burned in air. Substrate ignitions were

shown to occur at cigarette centerline temperatures as much . as 250° C below

those of the cigarette burning in air. The cigarette centerline temperature

rose only after the substrate started smoldering and there was heat feedback.

One could question whether the time- temperature characteristics of cigarettes

obtained in air are relevant to their ignition propensity. A more detailed

summary of these findings is given in Section 3.4.

Several investigators [44-51] placed cigarettes on substrates consisting

of cellulosic (cotton or rayon) fabrics over glass fiberboard, polyurethane

foam, and other paddings. Both flat and crevice substrates were used.

Temperature measurements were carried out with thermocouples embedded inside

25
the cigarette, at the cigarette/substrate interface, on the fabric surface

under and at various distances from the cigarette, and inside the padding at

various distances from the cigarette. As will be seen, both the peak temperatures and the duration of the time - temperature peaks determine whether selfsustaining, smoldering ignition of the substrate occurs or whether the substrate self -extinguishes . Unfortunately, some of the papers which present

time- temperature curves did not differentiate between occurrence of selfsustaining ignition, or smoldering of the substrate in the vicinity of the

cigarette and self -extinguishment of the substrate when the cigarette went out.

Furthermore, the degree of contact between the thermocouple and the

substrate or the cigarette is a somewhat uncontrolled variable in such experiments. Cellulosic materials shrink and often visibly move during charring;

cavities bordered by molten material or char are formed in polyurethane foam.

These can affect the contact with the thermocouple and the resulting temperature readings .

•

3.2.1 Investigators at the Massachusetts Institute of Technology

The most extensive work in this area was carried out by Salig, et al.

[44], This was summarized and extended by Tesoro [45], The following

discussion will start with temperatures measured inside the cigarettes,

followed by those obtained at the fabric/padding interface and inside the

polyurethane foam. Both flat and crevice geometries and covered and uncovered

cigarettes were used, as well as a set of three fabrics, with one of them

finished in various ways.

26
Figure 2 shows Salig's experimental arrangement for the cigarettes on the

substrates. Figure 3 shows the time - temperature traces obtained by

thermocouples located about 25 mm from the tips of the cigarettes, at the

cigarette centerline. The highest, and by far the narrowest, peak at 700° C was

obtained with the cigarette burning in air. The relatively low peak temperature reported may have been due to use of large diameter thermocouples which

were not described in these papers. When the cigarette was placed on a

substrate consisting of a 120 g/m2 cotton printcloth over polyurethane foam6 in

a crevice configuration, with the cigarette covered with another piece of the

same printcloth, the substrate did not ignite. However, the cotton fabric

showed some localized char and the polyurethane foam showed a 10 mm deep

trough. The peak temperature inside the cigarette was about 620°C, i.e.,

somewhat lower than that inside the same cigarette burning in air. The

temperature peak was wider, indicating a lower burn rate. Explanations offered

by the authors are the heat sink effect of the substrate and competition for

the available oxygen by the substrate (which would be minimal if the substrate

did not ignite) ; slowing of the oxygen supply rate by the fabric on top is an

additional factor.

When the cigarette was placed on a polyurethane foam block covered with a

scoured and bleached, 320 g/m2

, cotton duck, ignition occurred. The temperature rose to a 500°C "plateau" (slightly descending in this case, essentially

6 Polyurethane was Grade 2715-27-ILD polyether/polyurethane foam from Olympic

Products Company, Greensboro, NC , density 24 kg/m3

, no flame retardant, 4.8

percent nitrogen, 61.3 percent carbon, 9.0 percent hydrogen, and 24.7 percent

oxygen.

27
level in others) and then ascended to a peak of about 620° C. During the

plateau time, smoke generation increased and the smoke assumed a yellow color,

indicating polyurethane foam pyrolysis and probable smolder. Thus, polyurethane ignition occurred at a cigarette core temperature of about 500° C.

After ignition, heat feedback from the smoldering polyurethane foam increased

the cigarette core temperature.

The sequence of events was as follows: the cigarette causes smoldering

of the fabric, and only if the fabric is sufficiently smolder-prone can it

ignite the polyurethane foam. Essentially none of the polyurethane foam types

presently used in furniture, including the polyurethane foam used in this work,

ignites from a cigarette alone unless they are covered by a smolder-prone

fabric [ 9 ]

.

Figure 4 shows time/temperature traces for four thermocouples embedded in

the cigarette core; the first traces ("1C") are the ones shown in Figure 3. In

the majority of the cases, the mid- column (second and third) peaks inside the

cigarettes were slightly higher than the first ones and the last peak was lower

than the others, perhaps due to higher heat losses near the cigarette butt.

The shapes of the sequential peaks inside the cigarette burning on the

bleached duck substrate differed considerably, indicating a complex interaction

between the fabric, polyurethane foam, and the cigarette during ignition of

first the fabric and then the polyurethane foam. The above-mentioned plateau

decreased in height and width with smolder progress through the cigarette.

This indicates that as the substrate smolder grew, the cigarette temperature

28
was at first lowered. When the polyurethane foam started smoldering about 20

minutes after cigarette placement, substantial heat feedback to the cigarette

core apparently occurred.

The cigarette glowing zone in air was reported to have been approximately

cylindrically shaped, with a 10 mm dimension along the cigarette axis. Covered

cigarettes on a printcloth substrate had a conical burn zone, with a 15 mm

length when the cigarette had burned about half its length, and 25 mm near the

butt. With heavier, more smolder-prone fabrics, cigarette smolder zone lengths

of up to 33 mm were observed. Without a cover over the cigarette, the smolder

region in contact with the substrate often precedes that in the center of the

cigarette

.

Additional Printcloth Experiments:

Salig [44] performed a number of other experiments with the printcloth/

polyurethane foam substrate with thermocouples at various locations on and in

the substrate. The embedded thermocouples were placed 20 mm below the surface

of the polyurethane foam. In general, ignition did not occur in these experiments;- however, Salig reported one ignition of the polyurethane foam even

though the fabric showed little evidence of smoldering. This appears to be a

rare occurrence, and is mentioned here for the record.

Figure 5A shows the traces obtained by thermocouples located at the

fabric surface where it contacts the cigarette lying in the crevice. There was

only localized charring in the fabric and a small cavity in the polyurethane

29
foam, indicating that no ignition occurred. The temperatures measured in this

manner were about 200°C lower than those measured on the cigarette centerline,

and the peaks were about the same width.

Figure 5A also shows that temperatures with cigarettes covered with the

printcloth were somewhat lower, and the peaks wider, than those for uncovered

cigarettes. (Covered substrates have a lower cigarette ignition resistance

than uncovered substrates, as will be discussed later.) The peak temperature

measured 20 mm below the cigarette in the horizontal polyurethane foam was

reported to be 100° C higher for the covered than the uncovered cigarette (not

indicated in the figure)

(Somewhat different effects of covering cigarettes were obtained in

another study in which chrome 1/alumel thermocouples (no size given) were placed

at the surface of glass fiberboard along, and 25 mm above, and below the

crevice line [46]. The peak temperatures shown by the eight thermocouples for

uncovered cigarettes, resting directly on the glass fiber board, ranged from

200 to 300°C, and the average time above 200°C registered by the eight

thermocouples was approximately 20 seconds. With one piece of sheeting

covering the cigarette, peak temperatures ranged from 240 to 350° C and average

time above 200°C was again 20 seconds. For two cover sheets, the corresponding

results were 270 to 350°C and 30 seconds. It is possible that more oxygen was

available to cigarettes on glass fiberboard than to those on a

fabric/polyurethane foam substrate, and that this, along with the heat containment by the cover, accounts for the higher temperatures with cover.)

30
Salig's Figures 5B and 5C show temperatures obtained with

printcloth/polyurethane foam/crevice/covered cigarette substrates, 20 mm inside

the horizontal and vertical polyurethane foam. No ignition occurred. The

traces for these two locations are similar, with peak temperatures of about

300°C. This is about 150°C less than in the fabric, and 300°C less than inside

the cigarette.

Figure 6 presents similar traces, but with two cigarettes placed endto-tip into the printcloth/polyurethane foam crevice. In this configuration,

ignition occurred at about the time when half of the second cigarette was

consumed, indicating the importance of time of exposure. At about 40 minutes

after ignition, peaks of approximately 700°C occurred inside the cigarette and

of 450°C 20 mm inside the polyurethane foam. The second thermocouple inside

the horizontal polyurethane foam reached a temperature peak at the end of the

experiment, indicating, most likely, that the smolder wave moved back through

incompletely pyrolyzed material. Thermocouples 5-7 exhibited the plateau which

occurs during substrate ignition.

Other Fabrics:

Figures 7 and 8 show temperatures inside the cigarette core and the

horizontal and vertical polyurethane foam for igniting substrates, both

containing the relatively heavy duck fabric. Figure 7 shows results for the

fabric in its "greige" (raw cotton, unscoured) state, Figure 8 after scouring

and bleaching. The greige fabric is expected to contain alkali metal ions,

primarily Na and K, which are known to be smolder promoters [48,52,53]. For

31
the greige fabric, the temperature inside the cigarette reached 650°C, 20 mm

inside the vertical polyurethane foam, 500°C, and inside the horizontal

polyurethane foam, 700°C. The temperatures observed for the industrially

scoured and bleached fabric were similar but the peaks were somewhat narrower

except inside the horizontal polyurethane foam. With many of the alkali metal

ions supposedly removed by home laundering, the substrate did not ignite, and

temperatures inside the polyurethane foam stayed below 450°C (no figure).

It is noteworthy that the temperatures inside the horizontal polyurethane

foam were considerably higher than those reached inside the vertical polyurethane foam. Similar observations were made by other investigators [46], who

warned that reliance on upward char length measured on the fabric surface as

the pass/fail criterion, as practiced by UFAC [54], may be misleading. In

fact, not only extensive smoldering but eventual flaming was reported for

horizontal substrates which could perhaps be rated "passing" on the basis of

the upward char length criterion.

Figure 9 shows traces obtained from thermocouples spaced every 20 mm

along lines 20 mm inside the vertical and horizontal polyurethane foam covered

with the bleached duck. It seems noteworthy that all peaks inside the horizontal polyurethane foam occurred at almost the same time, regardless of the

distance from the crevice. The peak height decreased with increasing distance

from the crevice line. In the vertical polyurethane foam, time to peak

increased with increasing distance from the crevice line. Again, the temperatures were higher inside the horizontal than inside the vertical polyurethane

foam

.

32
3.2.2 Other Investigators

In a recent study by Ihrig, et al. , four experimental cigarettes were

allowed to burns on a variety of substrates [19]. The cigarette variables were

circumference (21.8 and 24.8 mm) and packing density (0.15, 0.20, and 0.28

g/cm3

) ; the lower values are claimed to be the lower practical limits which can

be produced. Other variables which may affect cigarette ignition propensity

(e.g., paper porosity and smolder accelerant or decelerant content [5]) were

not included in this study. The substrates consisted of 33 cellulosic fabrics,

ranging from 135 to 775 g/m2

, which covered the range available in local retail

stores in 1984. Each fabric was used over a polyurethane foam and over cotton

batting padding, in three configurations; flat, rectangular crevice, and acute

angle crevice. The fabric ignition temperature, air permeability, * moisture

content, density, and sodium and potassium ion contents were determined, as

were burn rate and heat output characteristics of the four cigarettes. In

addition, a method was developed to measure the smoldering proclivity of the

individual yarns sampled from the fabrics.

We draw the following conclusions from this work:

• Differences in the propensity of the cigarettes to ignite was shown on 29

of the 181 substrates (some tests were not performed due to shortage of

fabric)

.

33
The results indicate that a combination of low diameter and low packing

density may further decrease the ignition propensity of cigarettes. This

is in agreement with earlier findings on commercial cigarettes (which,

however, may also have varied in other parameters) [6,7,8,10-13].

» The ignition propensity of the cigarettes was correlated to the heat

output from the cigarettes, in calories/cigarette.

• The cigarette ignition resistance of polyurethane foam and cotton batting

mockups decreased with increasing alkali metal ion concentration in the

fabrics. Among the polyurethane foam mockups; increasing fabric weight

and decreasing fabric density also were found to reduce cigarette

ignition resistance. Most cotton batting crevice mockups ignited; among

the flat cotton batting mockups, cigarette ignition resistance seemed to

decrease with decreasing fabric weight, perhaps due to the generally high

alkali metal content of cotton batting which may come into play earlier

if the fabric is light.

o Over the range studied, cigarette variables were less important than

fabric or padding variables in predicting probability of ignition.

• The smoldering proclivity of the yarns increased with increasing alkali

metal content of the fabrics. This test, causing the yarn to smolder and

observing the distance and duration of smolder, could perhaps be adopted

by UFAC or the fabric industry as a simple, predictive method for the

efficacy of final rinsing of fabrics. In yarns which have been immersed

34
in soft water and dried smolder less than the yarns tested as taken from

the fabric, the final rinse probably has not removed the alkali metal

ions efficiently and the cigarette ignition resistance of the fabric

could be improved by further rinsing.

• The total number of ignitions for rectangular and acute angle crevice

mockups were similar. The rectangular configuration is the one chosen

for most tests of upholstered furniture substrates.

Most other investigators were interested mainly in substrate behavior,

with the objective of producing more smolder-resistant furniture, rather than

defining cigarette/substrate interaction. One laboratory measured fabric

surface temperatures with thermocouples in contact with the upholstery fabric

surface at various distances from a smoldering cigarette placed on the fabric

with the coal end down [47,48]. In this configuration, both peak temperatures

and peak widths increased with increasing cotton fabric weight. The smolder

propagation rate measured on the fabric surface was inversely related to fabric

weight but the mass burning rate remained constant. For a 542 g/m2 cotton

fabric, the smolder rate varied from 2.7 mm/min for polyurethane foam padding

to 4.5 mm/min for glass fiberboard. The following paddings produced results

within the 3.5 to 4.0 mm/min range: 25 mm thick polyester batting, polyurethane foam covered with this batting, polyurethane foam covered with flame

retarded cotton batting, 50 mm thick polyester batting, and flame retarded

cotton batting.

35
Decreasing the fabric air permeability by a factor of eight by backcoating decreased its smoldering rate by only 14 percent, and decreased the

peak temperature by about 50°C [48], (Washing the fabric in distilled water

again prevented ignition.) Other investigators increased air permeability of

the cover fabric by cutting slits in it [49]. They found that air permeability

changed in this manner did not affect smoldering temperatures measured at the

crevice; however, temperature peak width decreased with increasing fabric air

permeability. Higher temperature peaks and narrower peak widths were found

for a lighter than an heavier fabric; this agrees with Salig's results [44],

Olsen and Bollinger reported generally higher peak temperatures in the

crevice with the fabrics over polyurethane foam than over glass fiberboard

[50]. The lowest temperatures and the fastest burn rates were found with

cigarettes placed in glass fiberboard crevices, without fabric cover. When the

board was covered with fabrics varying in weight from 380 to 530 g/m2

, Olsen

found, unlike most others, no consistent relationship of temperature and burn

rate to fabric weight, indicating that fabric finish and other factors dominated in this case. In these glass fiberboard experiments, covered cigarettes

produced higher temperatures and wider peaks than uncovered cigarettes. Filter

and non- filter cigarettes of the same brand gave similar results.

The effect of fabric weight and padding material was investigated with

thermocouples placed in the crevice and above and below it at the

fabric/padding interface of the vertical member of the crevice [46]. The

fabric weight was varied by using one, two, or three layers of each of two

cotton fabrics. The padding materials were glass fiberboard, polyurethane

36
foam, and cotton batting. With polyurethane foam substrates, and when the

fabric mass was low, e.g., one layer, the initial temperatures were higher

below the crevice than above it. With three layers, the temperatures were

reported to be higher above the crevice. In the case of the cotton batting,

temperatures above and below the crevice were similar. These experiments were

apparently discontinued when obvious ignition occurred, so the above findings

are only for the initial stages of smoldering.

3.3 Ignition by Electric Heating Coils [44,45]

For research purposes, there has been some interest in replacing cigarettes by using better-defined heat sources, such as electric heating coils. In

this manner, the ignition of polyurethane foam and other substrates could be

more easily modeled. Salig's attempts in this area are described below [44].

Figure 10 shows the experimental arrangement: a 40 mm long, 6 mm diameter, electric heating coil was inserted into polyurethane foam blocks covered

with fabrics. This is obviously quite different from a cigarette ignition

situation but may be appropriate to study smoldering in foam. The smolder wave

progress was characterized by thermocouples embedded inside the polyurethane

foam. Figure 11 shows the results. A heat flux stated by the author to be

about 16 kW/m2 initiated smoldering; the method of inferring this flux is not

described.

37
With a dyed cotton duck covering the polyurethane foam, the smoldering

continued for about 50 mm and then extinguished; temperatures at the polyurethane foam center were about 380°C and considerably lower at the edges. The

smolder self -extinguished even when the heating coil delivered as much as 30

kW/m2

.

When the polyurethane foam was covered with a heavier diamond weave

cotton fabric, both polyurethane foam and fabric smoldered to completion

(Figures 12 and 13) . Peak temperatures inside the polyurethane foam reached

550° C, and at the top and bottom surfaces, 500° C. These peaks were first

reached at the top, then at the bottom, and only then at the center thermocouples. The condition of the substrate 18 minutes into the experiment is

shown in Figure 13; Salig stated that the bulging of the fabric ahead of the

smolder may be due to expansion of the hot, gaseous combustion products from

the polyurethane foam.

This experiment indicates the importance of a "critical fabric weight per

unit area" in the polyurethane foam ignition process, in this case, with the

electric heating coil as the ignition source. The same need for a critical

fabric weight per unit area has been found for cigarette ignition sources, as

discussed above and in Section 6. It also provides insight into the manner in

which gaseous combustion products move inside fabric covered polyurethane foam.

On the other hand, the heating coil experiments clearly point out the

differences between a transient and a steady heat source. Thus, the cigarette

burn cone with its small area does not ignite polyurethane foam without the

38
intermediate smolder front of critical weight per unit area (medium to heavy)

cellulosic fabrics. The static heating coil, with its larger surface, ignited

polyurethane foam directly, but the continuation of the smolder process again

depended on the fabric cover ignitability . It is also noteworthy that polyurethane foam smolder was reported to be initiated by a coil heat flux of 16

kW/m2 while cigarette total heat fluxes were reported to be 40 kW/m2

, obviously

distributed over a much smaller area. While the heating coil experiments are

of some modeling interest for polyurethane foam ignition, they seem to be only

of limited relevance for the present purposes.

3.4 Summary of Findings on Cigarette/Substrate Interaction

No complete model can be constructed from the above survey of observations on cigarette/substrate interactions. However, common threads can be

found among these studies, which vary greatly in methodology and purpose:

Placing a cigarette on a substrate can significantly lower the cigarette

temperature and burn rate. These reductions seem to be larger for

substrates which subsequently ignite than for those which smolder along

with the cigarette but self -extinguish when the cigarette burns out. For

example, the peak core temperature of cigarettes burning in air was

measured to be about 700°C, of cigarettes burning on substrates which

smoldered but self -extinguished, about 600°C, and of those measured

during ignition of the substrate, about 500° C. After ignition of the

substrate, heat appears to be fed back into the cigarette, raising the

core temperature to 600 to 700° C. One could question whether the study

39
of the burning of cigarettes in air is relevant to their behavior on

substrates prior to any substrate ignition. Experiments to investigate

this phenomenon are presently under way as part of the work under the

Cigarette Safety Act.

• Cigarette core temperatures reach a plateau during smoldering ignition of

the substrate; this appears to be due to competition of the smoldering

fabric for available oxygen. Some time after full ignition of the

substrate (foam involvement) , the cigarette temperature is further

increased evidently by feedback from the substrate.

* Cigarettes do not ignite most present-day polyurethane foam substrates

unless they are covered by a smolder-prone fabric: it takes the critical

weight per unit area of a medium to heavy weight, cellulosic or acrylic

fabric to obtain polyurethane foam ignition. Cotton batting smolders

readily, with and without cellulosic fabrics.

» In crevice ignitions (with the two members at right angles), the temperature inside the horizontal polyurethane foam generally reaches higher

peaks earlier than the temperature inside the vertical polyurethane foam

slab. The temperature traces inside the polyurethane foam show less

pronounced plateaus before ignition than do the traces obtained at the

cigarette core.

® Experiments with electric heating coils placed inside the polyurethane

foam cannot be substituted for cigarette experiments. While a Japanese

40
worker developed a "standard cigarette" ignition source consisting of a

series of small electrical coils heating consecutively, the correlation

between results obtained with this apparatus and results with cigarettes

of varying ignition propensity was not proven [55].

4. SUBSTRATE SMOLDERING MECHANISMS

This section is a brief review of the literature on smoldering of the

major padding materials in upholstered items: cellulosic materials and

polyurethane foams. While cellulosic padding - cotton batting - ignites

readily in contact with a cigarette (because of its favorable packing density

and abundance of alkali metal ions) , polyurethane foam as currently manufactured needs a smoldering cellulosic fabric cover before it ignites on exposure

to a cigarette.

The tobacco column and the paper covering a cigarette are chosen so they

will continue to smolder even if not puffed. The paper and tobacco column

smolder at the same rate. This smolder spreads readily from cigarettes to

medium and heavy weight cellulosic and acrylic fabrics and from them to many

commercial padding materials, especially cotton batting and polyurethane foam.

Certain materials, such as thermoplastic fabrics and batting, wool fabrics, and

halogen- containing materials (vinyl -coated fabrics, vinyl -vinylidene backcoatings, or polyurethane foam with smolder resistance (SR) treatment) interfere with this transfer. This will be discussed in more detail in Section 6.

41
4.1 Smoldering of Cellulosic Materials

There is a wealth of analyses of cigarette (mostly tobacco column)

smoldering behavior, as discussed earlier, and a series of papers analyzing the

smoldering behavior of shredded cellulose insulation and polyurethane foam

[53,56-59]. No model of smoldering of cotton fabric or batting was found, but

the general degradation behavior of cellulosic materials can be approximately

described by the following simplified overall reaction scheme:

char + vapors/gases

(absence of air)

fue' 2h + gases

char + vapors/gases

The gases and chars produced by the two different paths may differ in their

chemical nature [56],

The above diagram shows that initially there are competing oxidative and

pyrolytic reaction pathways; the oxidative pathway can be moderately exothermic

(several hundred calories per gram of fuel) . Both initial pathways may form a

high carbon-containing material (char) ; the two chars are probably not identical in reactivity or in other properties. These chars are typically somewhat

42
more resistant to oxidation than the initial fuel but ultimately can be

completely gasified, releasing a few thousand calories per gram of char. This

second oxidation wave can often be visually observed as a glow moving over a

previously charred area.

There appear to be no descriptions of basic smoldering experiments with

cotton batting or fabrics in the literature. However, in experiments involving

shredded cellulosic insulation on a heated plate, smoldering could be initiated

at temperatures as low as 220°C, especially in thick smolder beds [57,58].

(This compares with coal temperatures measured in cigarettes between puffs of

up to 750°C (Section 3.1), albeit spread over a much smaller area.)

Smoldering rate increased with: denser packing of the cellulose insulation,

thicker insulation beds, increased oxygen supply, and favorable air current

direction. Alkali metal ions have been shown to be smolder promoters in other

types of cellulosic materials [48,52,53]. The role of smolder retardants,

primarily boric acid, is to interfere with the char oxidation process; they do

not necessarily reduce temperatures in the initial smolder wave.

4.2 Smoldering of Flexible Polyurethane Foam

Few, present-day, commercial polyurethane foam upholstery or mattress

foams could be expected to smolder in contact with burning cigarettes (unless a

fabric cover was present) even though such foams vary widely in density, air

permeability, chemical composition, etc., [e.g., 44,60,61]. Peak smolder

temperatures in polyurethane foam were about 400° C or higher, and smolder

front progress in those foams which smoldered was about 6 mm/min. The overall

43
foam degradation process during smolder again can be divided into two major

competing pathways; formation of non- smoldering tar and formation of smoldering char. A simplified model of the smoldering process in polyurethane foam is

given below [62-68]:

Ignition

source

or fabric

smolder

Foam

air

(I)

Air

Heat + char II *

(5)

02 Degraded

foam

I Air (3)

I — Char I

depleted

air

( 2 ) Tar

N2 (4)

Gas

Step (1)

The first phase of polyurethane foam pyrolysis involves 10-15 percent weight

loss. The product is colored but still has some of the resiliency of the

original foam.

Step (2) and (3)

In the absence of air, or when the rate of Step (3) is prohibitively slow, the

degraded foam is converted to tar with the loss of extended surface/unit volume

essential for smolder. In air, char is formed.

Step (4)

In the absence of air the tar is completely gasified leaving a small residue

(1-3 percent) at 500°C.

Step (5)

The black cellular char (which retains much of the foam structure) formed in

Step (3) undergoes further oxidation in air and provides heat to drive the

smolder wave. If Step (5) is sufficiently fast, then the rate of heat production may be adequate to replace the outside ignition source so that it recedes

so far from the external heat source (e.g., smoldering fabric or cigarette)

that its own heat generation can no longer overcome heat losses; it will then

extinguish.

Two possible approaches to making polyurethane foam smolder resistant

have been suggested [63]. One is the use of agents which would interfere with

44
Steps 3 and 5, above, and, if sufficient volatile agent becomes available, also

reduce fabric smoldering. The second is promotion of tar formation by

weakening the polyol chain and urethane links. The latter, however, may

increase flaming combustion.

More specific modeling equations for the smoldering of polyurethane foam

in a simplified configuration and reasonable experimental validation are found

in [62]. The difficulties caused by the fact that smoldering is very

incomplete combustion are discussed. Both conduction and radiation affect the

smoldering rate in open structures, such as flexible polyurethane foam.

Smolder intensity was found to be governed by oxygen supply rate, but smoldering can proceed at oxygen supply rates as low as 5 percent of the stoichiometric rate of oxygen supply to the smolder reaction zone. The threshold

oxygen concentrations at which self- extinguishment , continued smoldering, or

transition to flaming occurs were established for three polyurethane foams

[61]. This work was performed with an electrical heating coil embedded in the

substrate rather than with a cigarette on the sample surface. Such embedded

heating coils appear to give results different from cigarettes, and seem to

lead to faster transition to flaming than cigarette - induced smoldering as

discussed earlier [44]

.

Most polyurethane foam formulation variables had little effect on

smoldering [63]. A report on an interlaboratory test to establish reproducibility of results obtained with a "standard" polyurethane foam claims that

there were no differences between specimens sampled along the length and from

45
top to bottom of a polyurethane foam bun (a production lot) [65]. A significant effect of breathability of the polyurethane foam was found, and it was

suggested that samples be flexed before testing; this increases breathability

and would simulate conditions in actual use. On the other hand, experience has

shown that it is difficult to produce a "standard" foam which, combined with a

"standard" fabric, gives reproducible ignition or non-ignition results [69].

Among the reasons may be that foams are not quality controlled with respect to

cigarette ignition resistance, but rather to obtain approximate uniformity of

density and resiliency. The formulation of flexible polyurethane foam is not

considered a precise art.

Some flame retardants increased, others suppressed smoldering. Several

studies describe improvement in smoldering resistance of fabric/polyurethane

foam mockups due to use of proprietary smolder and flame retardants [e.g., 66-

68,72-74]

.

5. CIGARETTE IGNITION BEHAVIOR

5.1 Cigarette Ignition Behavior of Soft Furnishings

The papers discussed in this section reported primarily ignition or nonignition of the substrates [54,69-108]; papers in which time/temperature

relationships in the substrate or cigarette were explored were discussed

earlier [44-51]. The basic configuration of the mini-mockup shown in Figure 14

was used in most of the evaluations of upholstered furniture substrates

46
discussed in this section. The test methods used for the evaluation of the

cigarette ignition resistance of soft furnishings are listed in Appendix A.

A discussion of the cigarette ignition behavior of soft furnishings is

given in Sections 3.1, 3.2 and 5 of [9]. An earlier bibliography of papers on

cigarette and flame ignition of upholstered furniture contains 145 references

[75], Two general discussions of cigarette ignition resistance summarize the

state of the art up to 1984 [76,77]. The results are based on experiments with

mini-mockups , mockups , or full-scale furniture. No papers on ignition resistance of fabrics or padding materials alone are included because there is ample

literature showing that the ignition behavior of the individual mockup components does not provide reliable ignition information on the material combinations [22,69], A substantial part of the experimental work on cigarette

ignition was performed at the California Bureau of Home Furnishings

[60,79,80,91-97,105]. A discussion of the relevance of bench-scale mockup

tests to cigarette ignition behavior of full size furniture is part of an

ongoing study under the Cigarette Safety Act, and will be discussed in a future

report

Table 6 summarizes the findings of many such studies. The materials in

the table are listed from top to bottom in the approximate order of decreasing

cigarette ignition resistance. In many cases, there is considerable overlap

between the characteristics of materials listed near each other, depending on

such factors as smolder retardant finish in fabrics or padding, polyurethane

foam variables, alkali metal ion content, fabric finish and backcoating.

47
It should be emphasized that some materials which have good cigarette

ignition resistance do not necessarily have good small flame ignition resistance and vice versa . For example, substrates covered with thermoplastic

fabrics tend to resist cigarette ignition because some of the heat transferred

to the fabric is absorbed by fabric melting. However, the thermoplastics

shrink, curl and melt upon contact with an open flame and expose the padding.

On the other hand, cigarettes induce smoldering in medium to heavy weight

cellulosic fabrics, with consequent heat transfer to the padding, but in

contact with a small flame cellulosic fabrics char and, until the char breaks,

protect the padding. Similarly, some flame retardants for polyurethane foam

reduce resistance to smoldering, while others improve both flame and cigarette

ignition behavior [60].

To prevent ignition by cigarettes, it is not necessary to use only the

materials listed on top of each column in table 6. For instance, the combination of a light weight thermoplastic fabric with polyurethane foam may not

ignite. Similarly, the combination of a medium weight cellulosic fabric with

a layer of polyester batting enveloping a polyurethane foam slab may not

ignite. Many wool and medium- to -heavy PVC-coated fabrics with flame retarded

or ordinary polyurethane foam or mixed ( thermoplas tic/cellulosic fiber) batting

have satisfactory cigarette ignition resistance. Material combinations which

are, for all practical purposes, cigarette ignition resistant in a crevice

configuration, with the cigarette covered (the worst case conditions), can be

chosen on the basis of a few trials in a qualified laboratory. The number of

such trials can be kept small by using the information from the table.

48
Tables 7 and 8 are examples of data on which the following discussion

will be based. Table 7 compares results obtained with a number of fabrics

combined with untreated and flame retarded polyurethane foam [90]. Table 8

summarizes two studies by the California Bureau of Home Furnishings [91-93],

In one, conducted in 1976, over 80 upholstery fabrics popular in California at

that time were tested over 10 padding materials each in the mini-mockup

configuration. The other study covered 171 commercial furniture items sampled

in 1981-82 to check compliance with the California standard.

Below is a discussion of the effect of the individual substrate components on cigarette ignition. Because of the interaction between such

components, there is a certain amount of redundancy.

5.1.1 Effect of Fabrics

Fiber content and weight : Many studies indicate that increasing the amount of

cellulosic materials (cotton, rayon, linen, hemp in fabrics, cotton in batting)

in the substrate decreases cigarette ignition resistance. Increasing the

amount of thermoplastics (nylon, polyester, and polyolefin in fabrics and

thermoplastic fibers, usually polyester, in batting) increases the cigarette

ignition resistance.

The highest cigarette ignition resistance is obtained with wool and PVCcoated fabrics [22,76,82,90]; their efficacy increases with fabric mass per

unit area (fabric weight) and, in the case of PVC , thickness of coating.

Blending of thermoplastic fibers with cellulosic fibers increases cigarette

49
ignition resistance over that of pure cellulosic fabrics; the data shown in

Table 8 imply that fabrics with 20 to 50 percent thermoplastic content rarely

ignite from cigarettes [91-96]. However, no systematic study of such blends to

optimize the retention of the appearance and feel of cellulosic fabrics, as

well as cigarette ignition resistance, has been undertaken. Possible variables

in such a study would be: location of the thermoplastic fibers - e.g., by

placing them in the filling in weaves where such filling appears mostly on the

surface; amounts needed in intimate yarn blends to obtain cigarette ignition

resistance; type of thermoplastic - nylon, olefin, polypropylene, etc.

Finish: Permanent (non-water- soluble) flame retardant treatments of

fabrics do not necessarily increase cigarette ignition resistance and can, in

fact, exacerbate the smolder tendency of cellulosic fabrics [91]. Treatment of

cellulosic fabrics and cotton batting with some non-permanent materials, e.g.,

a combination of borax and boric acid, can increase both flame and cigarette

ignition resistance [47,93,98-103]. Higher concentrations are often needed for

cigarette ignition resistance than for flame resistance. Such treatments can

affect the color and feel of fabrics but have been recommended for batting for

prison mattresses, for example [47,101].

Proprietary spray products claimed to make possible reasonable cigarette

ignition resistance and flame ignition resistance of upholstered items by

retrofit have been promoted. Tests with three such sprays indicated that the

needed amount of spray is larger than one would expect a consumer to apply, and

that it caused the fabrics to appear discolored and harsh to the hand [107].

50
Most commercial backcoatings either did not affect the cigarette ignition

resistance or else seemed to improve it [79,85,91,93,97,106], A vinyl

vinylidene latex backcoating and certain organophosphorus flame retardants

added to the backcoating have been reported to improve furniture fabric

cigarette ignition resistance [104,106],

Contamination of cellulosic fabrics and battings : The presence of alkali

metal ions, such as sodium and potassium, decreases cigarette ignition resistance [19,48,52,53], This important effect has thus far hardly been considered

by industry in fabric design and finishing.

Alkali metal ions are always present in unscoured cotton. On finished

fabrics, they may be present as residual detergents, softeners, dyes, or dye

auxiliaries. Rinsing such fabrics in clean water or laundering often causes

dramatic improvements in cigarette ignition resistance [19,45,48,52], In spite

of the publication of these results, little seems to be done by industry to

remove these contaminants. A simple method to evaluate whether residual fabric

finish lowers the cigarette ignition resistance of fabrics is described in

Section 3.2.2 [19]

.

Since perspiration and other dirt likely to be deposited on soft

furnishings contain alkali metal ions, furniture may become more ignitable with

age. However, a study of the effect of use and aging on the cigarette ignition

resistance of chair cushions is not conclusive on this point [84],

51
Tension : No systematic study of the effect of fabric tension on cigarette ignition resistance is available, but a summary of personal observations

from our laboratories can be reported. When tension is low, as in old furniture or certain styles, air layers may form between the fabric and the padding,

and cigarette ignition will be determined entirely by the fabric. With higher

tension, intimate contact between the fabric and padding is achieved and the

padding can act either as a heat sink (e.g., smolder resistant polyurethane

foam) , absorb heat during melting (polyester batting) , or smolder along with

smoldering fabrics (cellulosic batting)

.

Miscellaneous construction factors : The effect of fabric weight has

already been discussed. No systematic studies of the effect of other fabric

parameters, such as weave, yarn size and density, pile vs. non-pile, etc., have

been carried out. In grass clippings and foam, denser packing has been shown

to increase the smolder tendency [16,17,61,109]. This indicates that not only

weight but dense packing of fibers and other cellulosic materials promotes

smoldering. Lowering air permeability has been reported to increase cigarette

ignition resistance, but in some of these experiments, this was achieved by

applying latex backcoatings . This process introduces extraneous materials and

increases the weight [48], Increasing the air permeability by making slits in

the fabric increased the smoldering rate, but not the smoldering temperature

and total char areas [49].

Sheets and blankets can increase the probability of mattress ignition

when they are placed on the top of a burning cigarette. These items generally

do not ignite from cigarettes [22,82].

52
5.1.2 Effect of Padding Material

The relative effect of padding material on cigarette ignition resistance

is summarized in Table 6. Smolder resistant neoprene and the combustion

modified, high resiliency (CMHR) polyurethane foams rank high. Polyester

batting absorbs heat as it melts. Many flame retarded treatments of polyurethane foam used some years ago did little to improve smolder resistance or

even reduced it. In the last few years, mainly in response to the California

requirements [110], flame retardant treatments which improve both smolder and

flame resistance of polyurethane foam have been marketed. The smolder resistance of the boric acid treated cotton batting depends on the boric acid

concentration; some of this can be lost in handling the batting since the

material does not stick well to the' fibers [102,103]. Untreated cellulosic

batting smolders readily [22,54,60,69-71,88-101,110].

5.1.3 Effect of Interliner or Barrier Materials

The UFAC program [54] requires that all cover fabrics be tested, and

those which are more ignition prone (called Class II by UFAC) must be used with

a barrier material. The most common barrier material is polyester batting.

However, many fabrics, especially heavy cellulosics, ignite even with such

polyester barriers [69,79], On the other hand, the use of aluminized barrier

or interliner materials between the cover fabric and padding was found to be

very effective in increasing cigarette ignition resistance [22,44,45,71].

53
UFAC also introduced a test for "interior fabrics", fabrics often placed

between the cover fabric and the padding [54]. The test generally fails

cellulosic fabrics but passes thermoplastic woven and nonwoven fabrics. Other

interliners which increase cigarette ignition resistance are neoprene and CMHR

polyurethane foam sheets.

5.1.4 Effect of Welt Cord

The cigarette ignition resistance of crevices and cushion edges can be

enhanced or reduced by the presence of a welt cord, depending on its type

[54,69-71]. The cigarette ignition resistance is reduced if the welt cord

contains a cellulosic material, usually in the form of twisted paper or cotton

cords. Aluminum foil twisted into welt cords has been shown to have better

cigarette ignition resistance than untreated and flame retarded cellulosic welt

cords [78]. UFAC has recently upgraded its welt cord standard to eliminate the

latter [54]. Some thermoplastic and PVC welt cords also conform to the

upgraded welt cord standard.

In addition to the direct effect of the welt cord, it is often enclosed

in a strip of fabric. This increases the fabric mass in the crevice. In the

case of cellulosic fabrics, this reduces cigarette ignition resistance, and in

the case of thermoplastics, it may increase it [54,69].

54
5.1.5 Effect of Furniture Geometry

For any combination of fabric and padding material, cigarette ignition

resistance is better in the flat areas than in the crevices

[6,19,23,44,45,69,77], Several factors may contribute to the greater hazard in

the crevice: re -radiation of heat from two, rather than one, surfaces; a

chimney effect in the crevice under the cigarette [22,44]; and, in the case of

cellulosic fabrics, an increase in the mass of cellulose because of multiple

seams at pillow edges. Crevices can be rectangular, or, if the top of the

cushion is rounded or pulled away from the vertical surface, form an acute

angle; Ihrig, et al. , have shown that there is little, if any, difference in

the cigarette ignition resistance of these two crevice configurations [19].

Tufted areas also tend to have lower cigarette ignition resistance than flat

areas and are usually tested separately, as are areas near the welt cord of

flat cushions [22].

5.2 Cigarette Ignition Behavior of Wildlife Materials

Some of the early investigations of the propensity of cigarettes to

ignite materials were conducted on wildlife materials. The effect of wind

velocity and direction and of the ambient conditions was also more intensely

studied on these materials than on soft furnishings. A summary of these

studies is presented because of the physical similarity of the ignition process

and the cellulosic nature of the wildlife fuels.

55
Wildlife material, including compacted conifer needles, grass, and punk

wood can be ignited by. cigarettes [16,17,23,25,109,111]. Conditions which

increase the probability of such ignition are: dense packing of material

(e.g., 100 kg/m3 for dried grass clippings), high ambient temperature and low

humidity, and modest winds, especially in the. direction of the burn cone travel

on the cigarette. Especially in winds of 4. 8-6.4 km/hr, these substrates seem

to burst into flames rather rapidly, without lengthy smoldering periods. The

optimum wind velocity for ignition by cigars was higher, about 12 km/hr.

In the late 1920' s, the National Bureau of Standards conducted an

investigation, (in response to Congressional interest in reducing cigaretteinitiated wildlife fires) into the feasibility of reducing the ignition

propensity of cigarettes [16,17]. A frequency distribution of the length of

discarded cigarette butts was established. The most frequent length was 33 mm,

and two thirds of the butts were under 38 mm. It was concluded that if

cigarettes could be treated so as to not ignite substrates while burning over

this length, the problem would be solved. A number of treatments were

suggested, including borax, borax/boric acid, and sodium silicate, as well as

additional layers of paper or cork at the butt end; the latter appeared

promising. Fortunately, the use of asbestos paper for this purpose was shown

to be ineffective.

5.3 Cigarette Ignition of Garments

Garment fires are often blamed on cigarette ignition. However, two

investigators established that the fabrics used in such items generally do not

56
ignite from exposure to cigarettes [26,112], Improperly used matches or

lighters are more likely ignition sources in such cases.

6. RELATIVE IGNITION PROPENSITY OF CIGARETTES

A number of laboratories have conducted experiments to determine the

relative ignition propensity of commercial cigarette packings [5,7,8,10-17].

Several packings with a somewhat lower ignition propensity than most others

were identified in the U.S. as well as Japan. Such identification can be made

on substrates which have borderline cigarette ignition resistance, e.g.,

crevices formed by the California or UFAC standard fabric and UFAC standard or

similar polyurethane foam types [11,13]. The majority of upholstery substrates

would, however, either not ignite with any or ignite with all commercial

cigarette packings, because of the small range of ignition propensity of

present, commercial cigarette packings.

In one study, a number of fabrics were used so that one fabric ignited

with all test cigarettes, one fabric with none, and several with some but not

all cigarette packings, allowing a ranking of the ignition propensity of the

cigarettes [ 7 ]

The same cigarette packings were also placed for 1, 2, or more minutes on

flat areas of the substrates of varying cigarette ignition resistance and then

removed [7]. If the substrate still smoldered 10 minutes after the removal of

the cigarette, ignition was recorded. Thus the propensity of cigarettes to

ignite substrates could be defined both by the number of substrates a given

57
cigarette ignited and the time it took to ignite any specific substrate.

Times to ignition varied from 2 to 7 minutes; Salig found ignition times of 1.5

minutes for low cigarette ignition resistance substrates [44]

.

Two means of quantifying the propensity of cigarettes to ignite substrates have been suggested. One is to place the cigarettes on rnini-mockups

made from standard fabric and foam as in the California upholstered furniture

test [110] (Figure 2), and measure the mass loss rate. The other consists of

placing the cigarette on a piece of a-cellulose chromatographic analysis paper

and again measuring the mass loss rate [7]\ The latter method was proposed in

the belief that the chromatography paper was more reproducible than fabric and

polyurethane foam, which have shown cigarette ignition resistance variations

even in so-called "standard" materials [69]. This concept was critically

discussed in [113]. Ihrig, et al . . found a positive correlation between

cigarette ignition propensity of four experimental cigarettes and cal/cigarette

of the cigarettes in air [19].

The studies of relative ignition propensity of commercial cigarette

packings can be summarized as follows:

1. Most cigarette packings investigated have similar ignition propensity.

However, a few packings have been found to have somewhat lower ignition

propensity. This was found for a variety of upholstered substrates, in

flat areas and crevices varying in fabrics and padding materials

[6,7,10,11,13-15], in mattresses [8,12], and in wildlife material

[7,16,17]

.

58
2. Propensity to ignite did not correlate with burning rate or burn cone

temperatures of the cigarettes [7].

3. While the commercially available cigarettes did not make it possible to

conduct an experiment in which such parameters were varied systematically, it appears that lowering the fuel content, by reducing packing

density and by reducing the diameter, may lower the ignition propensity

[6,7]. Making the burn time of cigarettes shorter, by either making the

tobacco column shorter or lowering the packing density (which increases

linear burn rate) would obviously reduce the time during which a smoker

may become sleepy and inadvertently drop the cigarette.

4. The differences in ignition propensity of the commercial cigarette

packings tested are small in the context of the cigarette ignition

resistance of the total population of soft furnishings in American homes

which may be subject to contact with inadvertently dropped cigarettes.

Perhaps one half of this population - a rough guess indeed - may not

ignite from any cigarette. This would include mattresses produced since

1973, when the U.S. mattress standard started to be enforced [114], as

well as most furniture made to the principles outlined above in Section

6. Another large portion may ignite with all commercially available

cigarettes. The percentage of soft furnishing substrates which ignites

with some but not all present day commercial cigarette packings is

probably quite low.

59
7. CONCLUSIONS

The literature pertinent to ignition of soft furnishings and of wildlife

materials by smoldering cigarettes was critically reviewed, with the objective

of presenting as much background material as possible which may assist in the

consideration of cigarettes with lower ignition propensity. Material was

included in this report which may be relevant to construction of a model for

cigarette ignition of soft furnishings, especially information on the burning

behavior of cigarettes.

Other material included discusses the cigarette ignition resistance of

upholstered furniture and mattresses. While there is a large amount of

literature in those two fields, the area of most direct interest - how cigarette parameters affect their ignition propensity - had not been well-studied,

and much more needs to be done

.

Perhaps the most important finding was that the smoldering behavior of

cigarettes on substrates is different from that of cigarettes burning in air.

Compared to the temperatures observed in free burning (in air), core temperatures of cigarettes before full ignition of fabric and polyurethane foam

ignition were distinctly lower. However, these temperatures were maintained

over longer periods. After both the cellulosic cover fabric and the polyurethane foam padding ignited, heat feedback from the smoldering substrate

increased the observed cigarette core temperature.

60
Studies of the interaction of cigarettes and igniting substrates have

been performed with commercial cigarettes. It was found that most of the

cigarettes used in these experiments behaved quite similarly; however, a few

cigarette packings with somewhat lower ignition propensity on certain

fabric/padding combinations were found in these studies. The specific factors

which led to the lower ignition propensity have not yet been clearly

established

8 . ACKNOWLEDGEMENTS

Dr. Richard G. Gann made numerous helpful suggestions and Ms. Paula

Garrett skillfully processed this manuscript.

The patents listed in Appendix B were provided by Drs . P. H. Leake of the

American' Tobacco Co., and A. W. Spears, III, of Lorillard. Richard Harris of

the Center for Fire Research compiled Appendix B. Ms. Nora Jason of the Center

for Fire Research performed the data base searches, and Dr. Peter Roussopoulos

Forest Fire and Atmospheric Research, U.S. Department of Agriculture, arranged

a search of the USDA reports.

61
9 . REFERENCES

[1] Cigarette Safety Act of 1984, Public Law 98-567 (Oct. 30, 1984).

[2] Courter, M.J., Fire Loss in the United States During 1984, Fire Journal,

49, (Sept. 1985).

[3] Harwood, B„, Consumer Product Safety Commission Internal Memorandum,

(July 1986).

[4] Maxwell, Jr., J.C., Maxwell Report - Revised 1985 Year-End Sales

Estimates for the Cigarette Industry, New York, NY (1985).

[5] Spears, A.W.

,

A Technical Analysis of the Problems Relating to

Upholstered Furniture and Mattress Fires Relative to Proposed Cigarette

Legislation Including a Review of Relevant Patents, Testimony, Subcommittee on Health and the Environment, Committee on Energy and

Commerce, U.S. House of Representatives (March 21, 1983).

[6] Krasny, J.F. and Gann, R.G., Relative Propensity of Selected Commercial

Cigarettes to Ignite Soft Furnishings Mockups , NBSIR 86-3421, [U.S.]

Nat. Bur. Stand. (1986).

[7] Krasny, J.F., Allen, P., Maldonado, A., Juarez, N., Development of a Candidate Test Method for the Measurement of the Propensity of Cigarettes to Cause Smoldering Ignition of Upholstered Furniture and

Mattresses (NBSIR 81-2363) [U.S.] Nat. Bur. Stand. (1981).

[8] Viau, R. and' Kasem, M.A. , Some Aspects of Fire Safety of Upholstered

Furniture and Mattresses, Presented at the Ninth International

Conference on Fire Safety, San Francisco, CA (Jan. 1984).

[9] Babrauskas , V. and Krasny, J., Fire Behavior of Upholstered Furniture,

Monograph 173, [U.S.] Nat. Bur. Stand. (1985).

[10] California State Department of Consumer Affairs, Bureau of Home

Furnishings, Connecticut Fire -Safe Cigarette Study, Final Report,

California Bureau of Home Furnishings, North Highlands, CA (June 1986).

[11] Ziolkowski, J., Upholstered Furniture Action Committee, personal

communication (1985) .

[12] Klancnik, A., Sealy, Inc., Presentation to the Technical Study Group of

the Cigarette Safety Act of 1984 (1985).

[13] Macaluso, C., Cigarette Ignition Studies, in Testimony, Subcommittee on Health and Environment, Committee on Energy and Commerce, U. S. House of

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.

62
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65
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,

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[66] Tesoro, G.C., The Fire Safety of Upholstered Furniture: An Evaluation

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66
[68] Eicher, W.J. and Szabat, J.F., Response of Polyurethane Foams to

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(1980).

[69] Upholstered Furniture Flammability Briefing Package; Reference 14:

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[70] Briefing Paper on Upholstered Furniture Flammability, Tab B: Fairall,

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and Data Summary, U. S. Consumer Product Safety Commission (1984).

[71] Upholstered Furniture Flammability Briefing Package, Reference 19:

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Consumer Product Safety Commission (1983) .

[72] Szabat, J.F., Combustibility Aspects of Polyurethane Foams for

Mattresses, J. Consumer Product Flammability, 5, 82-95 (June 1978),

[73] Keating, J.Z., Use of Hydrated Alumina as a Flame and Smoke Suppressant

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220 (Nov. 1982).

[74] Schuhmann, J.G., Improved Furniture and Mattress Fire Safety Through the

Use of Combustion Modifying Foam, Proc

of 6th International SPI

Technical/Marketing Conference, pp . 307-315, Technomic Publ., Lancaster,

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[75] Damant, G.H., A Bibliography of Published Information on Furniture

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[76] References to Literature on the Fire Hazards of Furniture and

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Borehamwood, England (1979) . Also supplement (June 1982)

[77] Fires in Furniture (Building Research Establishment Digest No. 285),

Fire Research Station, Borehamwood, England (1984)

[78] Report of 1982 Test Series to Evaluate UFAC Construction Modifications,

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[79] Damant, G.H., Williams, S.S. and Krasny, J.F., Cigarette Ignition

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Flammability, 9 , 31-46 (1982).

67
[80] Damant

,

G.H., California Upholstered Furniture Combustibility Standard:

1981 Update, J. Consumer Product Flammability, 8,, 209-220 (1981).

[81] A: Ingham, P.E., Goddard, J.M. and Grueber, A.L., The Influence of

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Furniture (1979); B: Ingham, P.E., The Flammability of Polyurethane

Upholstered Furniture, Part II. Tests with Larger Ignition Sources and

"Improved" Foams (1981); C: Ingham, P.E., The Flammability of

Polyurethane Upholstered Furniture, Part III. House Fire Tests (1981)

Wool Research Organization of New Zealand, Christchurch.

[82] Pakkala, L. , Ignitability of Beds and Bedding, Research Report No. 247,

Technical Research Center of Finland, Espoo, Finland (1984).

[83] Ramsay, G.C. and Cerra, A.P., A Progress Report on the Assessment of

Test Methods for the Ignitability of Upholstery Combinations by Small

Ignition Sources - Cigarette Ignition. ISO/TC136 document (April 1982).

[84] Harabin, D., Ostrander, E.R., and Stout, E.E., Properties of Textile

Upholstery Fabrics and Their Importance to Consumer Satisfaction,

(Bulletin 1032). Cornell University Agricultural Experiment Station,

Ithaca, NY (May 1973).

[85] [44Fesman, G., A Study in Smoldering Test Behavior Versus Air Flow

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Technical/Marketing Conference (Nov. 1983)

.

[86] Gill, J.T., Howerton, R.D., and Werner, P.M., Combustion Acceleration as

a Measure of Upholstery Fabric Flammability, Textile Chemist and

Colorist. 13, 3-33 (1981).

[87] Baitinger, W.F. and Konopasek, L. , Smoldering Combustion of Cotton

Fabric/Urethane Foam Composites, in Proc. of the 7th International

Conference on Fire Safety, 11-22, Stanford Research Institute, Menlo

Park, CA (1982).

[88] Braun, E., Krasny, J.F., Peacock, R.C., Paabo , M. , Smith, G.F., and

Stolte, A., Cigarette Ignition of Upholstered Chairs, J. of Consumer

Product Flammability, 9 , 167-183 (1982).

[89] Hafer, C.A. and Yuill, C.H., Characterization of Bedding and Upholstery

Fires, Southwest Research Institute, San Antonio, TX (1970).

[90] Pakkala, L. , Kortekallio, E.L., and Ulmanen, M. , Ignitability of

Upholstered Furniture, Nordtest Project 186-79, VTT Research Note

69/1982, Technical Research Center of Finland, Espoo, Finland (1982).

[91] Damant, G.H. and Young, M.A., Smoldering Characteristic of Fabrics Used

as Upholstered Furniture Coverings, J. Consumer Product Flammability, 4,

60-113 (1977).

68
[92] Damant, G.H. and Young, M.A.

,

Flammability Classification of Fabrics

Used as Upholstered Furniture Coverings, J. Consumer Product

Flammability, 4, 329-345 (1977).

[93] Damant, G.H., Williams, S.S. and McCormack, J.A., The Role of Fabric in

the Cigarette Ignition of Upholstered Furniture (Laboratory Report No.

SP-83-2) Bureau of Home Furnishings, Department of Consumer Affairs,

North Highlands, CA (1983).

[94] Damant, G.H., McCormack, J.A. and Williams, S.S., California Enforcement

Tests on Commercial Chairs, Proc . of the 7th International Conference of

Fire Safety, 2-10, Stanford Research Institute, Menlo Park, CA (Jan.

1982) .

[95] Damant, G.H., Home Furnishings Fire Retardant Requirements: The

California Experience, J. Consumer Product Flammability, 6, 95-104

(1979).

[96] McCormack, J.A., Damant, G.H. and Williams, S.S., Cigarette Evaluation

of 450 Pieces of Residential Furniture, California Bureau of Home

Furnishings, North Highlands, CA (1985).

[97] Williams, S.S. and Damant, G.H., Rate of Weight Loss as an Aid to

Evaluate the Smoldering Propensity of Upholstered Fabrics, J. Consumer

Product Flammability, 8., 89-104 (1981).

[98] Baitinger, W.F., Fire Retardance Treatment of Fabrics for the '80s;

Smolder Resistant Cotton Treated with Boric Acid, Textile Research J.,

52, 82-86 (1982).

[99] Knoepfler, N.B., Neumeyer, J.P. and Madasci, J.P., Meeting the Mattress

Flammability Standard FF 4-72 with Boron Treated Cotton Batting

Products, J. Consumer Product Flammability, 1, 240-264 (1974).

[100] Madasci, J.P. and Knoepfler, N.B., Upgrading Classification of

Upholstery Fabrics via Vapor-Phase Deposition of Boric Acid, Textile

Research J. 49, 176-190 (1979).

[101] Verburg, G.B. and Lambert, A.H., Smolder-Resistant, Oil-and WaterRepellent Cotton Upholstery Fabrics, J. Fire Retardant Chemistry, 2 . 136-153 (1980).

[102] Madasci, J.P. and Neumeyer, J.P., A Comparison of Smolder Resistance

Standards for Boric Acid Treated Cotton Battings, J. Consumer Product

Flammability, 9, 3-10 (1982).

[103] Madasci, J.P. and Neumeyer, J.P., Chemical Additives to the Boric Acid

Treatment of Cotton Filling Materials Used in Mattress and Upholstered

Furniture, J. of Fire Retardant Chemistry, 9 , 70-839 (1982).

69
[104] Leitner, G.J., Reactive Organophosporus Additives as Smolder Retardant

Agents in Furniture Fabric Backcoatings , J. Consumer Product

Flammability, 8., 158-168 (1981).

[105] Williams, S.S. and Damant, G.H., Evaluation of Three Methods of

Rendering Upholstery Fabrics Smolder Resistant, Laboratory Report No.

SP-82-2, Bureau of Home Furnishings, North Highlands, CA (1982).

[106] Knoepfler, N.B., Neumeyer, J.P. and Koenig, P.A., "Backcoated Mattress

Tickings as a Factor in Meeting Mattress Flammability Standard FF 4-72",

Part I. Polymer Backcoating. J. Fire & Flammability, Consumer Product

Flammability Supplement, 2 , 70-83 (1975), Part II. Compound Polymer

Backcoating 2, 123-139 (1975).

[107] Krasny, J.F., Evaluation of the Effectiveness of Retrofit Products for

Increasing the Cigarette Ignition Resistance of Upholstered Furniture,

NBS Letter to the U. S. Consumer Product Safety Commission (1984).

[108] Palmer, K.N. , Paul, K.T. and Taylor, W. , Test Specifications for Fire

Properties of Bedding and Upholstered Furniture, Building Research

Establishment Report (ISBN 0 11670663) Her Majesty's Stationery Office,

London (1979).

[109] Countryman, C.M., Ignition of Grass Fuels by Cigarettes, Fire Management

Notes, 44:3 (1983).

[110] State of California, Department of Consumer Affairs, Bureau of Home

Furnishings, Flammability Information Package, North Highlands, CA

(1983).

[111] Blackmarr, W.H., Moisture Content Influences Ignitability , USDA Forest

Service Research Note SE-173, Southeastern Forest Experiment Station,

Asheville, NC (1972).

[112] Blackenbaker , S., Cigarettes and Electric Heating Elements as Ignition

Sources, Proceedings of the Thirteenth Annual Meeting, Information

Council on Fabric Flammability, Atlanta, GA (1979).

[113] Tesoro, G.C., Some Reflections on a Proposed Test Relating to Ignition

Hazard in Upholstered Furniture, Textile Chemist and Colorist, 15, 40-

44 , (April 1983)

.

[114] Code of Federal Regulations, Part 1632, Standard for the Flammability of

Mattresses (and Mattress Pads) , FF 4-72 (1983)

.

[115] Leake, P.H., American Tobacco Co., Presentation to the Technical Study

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70
Table 1. Data Bases Searched

From Year to Present

Chemical Abstracts 1967

Engineering Index Base Engineer ing Meetings 1979

Compendix (Engineering Information, Inc.) 1970

National Technical Information Service 1964

World Textiles 1970

Textile Technology Digest 1978

Paperchem 1967

CRIS/USDA 1983

BIOSIS Previews • 1969

AGRICOLA 1970

FIREBASE 1900

Tobacco Abstracts 1975

World Patents 1963

71
Table 2. Summary of "Fire Safe” Cigarette Patents [115]

CONTAIN ASH AND/OR REDUCE HEAT OUTPUT

- Paper treated with borates, silicates, chlorine containing

latex, fire proof paint

- Cigarette wrapped with aluminum foil, asbestos, fiber glass, etc.

- Aluminum trihydrate added to tobacco

EXTINGUISH AT SELECTED POINT

- Sliding or fixed non-combustible sleeve or band on cigarette

- Insertions in cigarette (barrier disc of porous non-combustible

materials such as asbestos, aluminum, etc.)

- Air gap in tobacco in cigarette

EXTINGUISH AT BUTT END AND/OR PREVENTION OF HOT COAL FALLING OFF

NO. OF Z OF PATENTS PATENTS

30 32

1613

1

17

14

1

26 27

19 20

6

1

6

1

21 22

- Non-combustible anchor or sleeve

- Addition of extinguishing materials between tobacco and filter

(capsules containing water, porous asbestos or metal discs, nylon band containing water) 18 19

ADDITIONS TO CIGARETTE HOLDERS TO CONTAIN ASH AND PREVENT CONTACT WITH

BURNING CIGARETTE 18 18 19 19

TOTAL 95 95 100 100

72
Table 3. Characteristics of Comnercial Cigarette Packings [22,25]

Cigarette Packings Acquired about 1980

Coefficient

Standard of variation

Characteristics Average Deviation (X) Range

Cigarette 3

Length of tobacco column (mm) 69.0 8.8 12.8 44.5-90.2

Diameter (mm) 7.9 0.3 3.3 6. 6-8.

5

Weight (g) 0.796 0.098 12.3 0.582-1.153

Heat (J/mm)k 188.7 14.7 8.0 143.3-230.7

Ash (g/nm) 0 0020 0.0002 10.0 0.0010-0.0024

3 ~3 Packing density (g/nm ) x 10 0.2237 0.0129 5.8 0.1954-0.2742

Tobacco 3

Weight (X of cigarette weight) 94.2 1.0 1.0 91.6-97.7

Heating values13 (J/g) x 10

4 1.6585 0.0456 2.8 1.5443-1.8677

( J/mm) 180.8 14.9 8 3 134.5-222.8

Ash (%) 16.3 1.3 8.1 11.8-19.4

(g/mm) x 10 3 1.78 0.19 10.9 0.97-2.21

Acetone extractives (%) 8.8 1.8 20.5 4.7-16.2

(J/Bm) x 10 3 3.128 0.556 17.8 1.555-5.304

Paper 3

Weight (X of cigarette weight) 5.8 1.2 20.2 2. 3-9.

9

Heating value13 (J/g) x 10

4 1.1737 0.0799 6.8 1.0288-1.4376

( J/rnn) 7.8 1.7 22.0 3.0-12.2

Ash (X) 26.4 5.6 21.3 11.9-35.4

(g/tnn) x 10

4 1.7 0.5 29. 4 0.7-13.6

Peak Temperatures, °C

Center of cigarettes 5 780 - — 763-802

Surface of cigarettes 01 442 85 19 394-510

Time above 232 "C, s e

Center of cigarettes 100 15 15 67-122

Surface of cigarettes 80 17 21 62-94

a - 128 cigarette packings

b - Heating values measured in bomb calorimeter

c - 35 cigarette packings

d - 90 cigarette packings

e - 8 cigarette packings

73
Table 4. Characteristics of 32 Commercial Cigarette Packings [23]

Characteristics

Cigarette Packings Acquired about 1971

Coefficient

Standard of variation

Average Deviation (Z) Range

A. 26 filter cigarette packings!

Cigarette

length (mm) 86 6.0 7.0 80-100

weight (g) 1.05 0.07 6.7 0,96-1.23

butt temperature (*C) 659 25 3.8 601-711

Tobacco

weight (Z of cigarette weight) 74.4 5.7 7.6 59.7-80.3

heat (J/mm3

) a 4.2 0.1 2.4 3. 9-4.

6

3 -3 packing density (g/nm ) x 10 0.27 0.01 3.8 0.254-0.294

B. 6 Non-filter cigarette packings

Cigarette

length (mm) 79 7.0 9.0 70-80

weight (g) 1.03 0.06 5.8 0.957-1.094

butt temperature (°C) 695 39.0 5.6 627-722

Tobacco

weight (Z of cigarette weight

)

94.76 0.33 0.4 94.24-95.20

3 packing density (g/nm ) x 10

-3 0.27 0.01 3.7 0.259-0.286

heat (J/mm3

) a 4.3 0.20 4.7 4. 1-4.

5

Paper

weight (Z of cigarette weight) 5.23 0.33 0.4 4.80-9.76

a Heating values measured in bomb calorimeter.

74
Table 5. Cigarette Temperature and Heat Flux Results with the Cigarette

Resting on a Copper Plate [43],

16 Commercial Cigarette Packings Acquired in 1969

Coefficient

Conditions Average

Standard

Deviation

of variation

(%)

A. Temperatures, °C

dry3 490 35 7.1

conditioned13 492 45 9.1

B. Heat flux, kW/m2

dry 40,6 6.7 16.4

conditioned * 40.6 6.4 15.7

a - b - dried at 110°C, cooled in

dried and cooled as above,

desiccator 8 hours,

conditioned for 8 hours at 24°C and 65 % r.h.

75
Upholstered

Furniture

Components

Listed

in

Approximate

Order

of

Descending

Cigarette

Ignition

Resistance

76
TABLE 7

Typical Cigarette Ignition Test Results [90]

Fabric Structure3

Fabric

Weight

(g/m2

)

Fabric*3 Burn

Time

(s)

PU C Foam

Type

Cigarette^

Ignition

Pass/Fail

100% cotton chenille 355 13 NFR F FR F

56 cot + vis/5pe/39 acr 400 26 NFR P plush FR P

52 linen/48 cot 430 41 NFR F

panama FR F

54 nyl/32 FR vis/14 pe 400 47 NFR P

plush FR P

34 wool/52 vis/14 nylon 450 56 NFR P panama FR P

65 wool/35 FR vis 540 SE NFR P twill FR P

52 wool/27 cot/21 nylon 575 SE NFR P twill FR P

100 wool reps 375 SE NFR P FR P

PVA/PVC twill 475 SE NFR P FR P

87 cot/13 FR vis. 200 SE NFR F FR P

a cot - cotton, vis - viscose , acr - acrylic. pe - polyester

^Modified CS-191 Test (flame ignition) , SE - self-extinguishing

CPU: untreated (NFR) 30 kg/

Q m , flame retarded (FR) 33 kg/m2

- fail, P - pass

77
TABLE 8

Cigarette Ignition Resistance of Typical Fabric/Padding Material Combinations [91-92]

A. Mini-mockup results (1977)

padding materials 3

Percent of Fabrics Igniting

' 100% Cellulosic/ 100% _

Cellulosics Thermoplastic Blends Thermoplastic

Batting:

100% cotton

Untreated 100 82 9 FR treated 76 43 0

70/30 cotton/polyester 79 32 0

100% polyester

Non-resinated 33 7 0

Resinated 19 4 0

Foam:

Polyurethane

Untreated 41 25 0

FR treated 1 86 54 0

FR treated 2 38 25 0

High resiliency 83 57 0

Neoprene interliner over cotton batting 19 14 0

Glass fiberboard 100 54 0

B. Results on 171 furniture items

(1983) [225

]

b

fabric weight

fabric weight

<270 g/m2

: 67

>270 g/m2

: 95

>70% cell: 6 <70% cell: 82

6

a Filling material specifications:

Materials Density kg/m3

1. Batting:

100% cotton, untreated 38

FR cotton (12-15% boric acid) 38

70/30 cotton polyester, bonded 37

100% polyester, resinated (28% acrylic resin) 8

100% polyester, non-resinated (with polyester scrim) 8

2. Foam:

Untreated PU 20

FR PU 1 (antimony trioxide and PVC) 37

FR PU 2 (brominated biphenyl) 32

High resiliency PU (brominated organophosphate) 42

2

3.

Neoprene interliner: 5 mm thick with cotton scrim backing 950 g/m

^Various filling materials.

78
HAEMAL

POSITION

RADIAL

POSITION

DIRECTION OF

TEMPERATURE OF SOLID GAS FLOW

TEMPERATURE OF GASES

Figure 1. Temperature distribution in a cigarette during free

burning (°C)

79
Polyurethane foam (PU) blocks cover*0

with upholstery fabric /

Figure 2. Test arrangement for crevice tests.

80
O.) sanivaidwii

/ 81

Figure

3.

Time/temperature

relationships

inside

cigarette

core

in

air

and

on

two

substrates.

Cigarette

burning

in

air.

Cigarette

in

crevice

of

printcloth

upholstery

fabric/PU

block

mockup;

cigarette

covered

by

small

piece

of

fabric

(printcloth/PU/crevice/covered)

Cigarette

in

bleached

duck/PU/crevice/covered

mockup.
c.

•te&otod duck / PU/cr#vie# /cov#r*d 740

§20

§00

S§0

2 §§

12 ®

0

Figure 4. Time /temperature relationships measured in four Inrat-ions

inside cigarette core. Conditions as in Figure 3.

82

TEMPERATURE

C*C)
C+earatte fabric Interface

c.

500

550

255

128

0

Figure 5. Time /temperature relationships at fabric surface and

20 mm inside vertical and horizontal PU- Printcloth

Pr in tcloth/PU/ Crevice

No ignition.

83
C40*r«tt« cor«

TIME (mimilM)

Figure 6„ Time/temperature relationships inside cigarette core and

20 ram inside vertical and horizontal PU - Printcloth

Ignition with two cigarettes, end-to-tip.

Pr in tcloth/PU/ Crevice/ Covered

.

84

TEMPERATURE

(*C)
B

740

•20

600

360

266

126

0

yj

§

h*<

£C

IU

ft.

LU

c.

46 40 35 30 25 20 16 10

TIME (minut**)

• 0

Figure 7. Time/temperature relationships inside cigarette core

and 20 mm inside horizontal and vertical PU - Greige Duck Fabric

Greige Duck/PU/Crevice/Covered

Ignition

85
Figure 8. Time/temperature relationships inside cigarette core and

20 mm inside vertical and horizontal PU - Bleached Duck Fabric

Bleached Duck/PU/ Crevice /Covered

.

Ignition

.

86
A.

TIME (mtnotos)

Figure 9. Time/temperature relationships at various locations

inside vertical and horizontal PU.

Thermocouples 20 mm inside PU at various distances from

crevice line.

Bleached Duck/PU/Crevice/Covered Cigarette.

Ignition.

87

TEMPERATURE

(*C)
B.

Figure 10. Arrangement for inducing ignition with an electrical

heating coil

88
M 1C 10 • 0

TMC CwfMt—

)

Figure 11. Time /temperature relationships inside a fabric covered PU

block, with electric heating coil (various output) embedded

Dyed Duck/PU/Flat

.

89

TEMPERATURE

(*C)
•20

too

240

264

12*

0

Figure 12. Time/temperature relationships inside a fabric covered PU

block, with electric heating coil (15.5 kW/m ) embedded

Diamond weave fabric/PU flat.

Ignition.

90

TEMPERATURE

CC)
Thermocouple j

Virgin

foam

00e

ra

01 x

i-i •u

CJ0) rH

<0 X

CJo3

CUT3

a»

i-i ai>oo 4Jc o 01 •H B H •H X 1-4 CO 0) 4h a* C 0) •H

4-4

01

O >

CO 4-1 3 1-4 • CO H u 4-4 0) Cfl CO to rH

t—1

<H 1-4 o 01 B ED 4-1 CO • Pj ch

-a CO

14-1 0)

u

O TJ •H CO 'V l-( 0) 00 01 X 4-1 C X CO 3

•H E 4-1

C 3 01 •H

(0 01 E H -~- >

XtN CO CO 6 0) --4 CJ ^ •H 3 3 C

4-1 ^ TO o

CO c rH B o 4-4 0) • s -H X LO CO C

<J —4 •H 00

in ^ a

M

aiu3

oo

91
Plywood

203x203

Cotton

batting

or glass

fiberboard

50

Fabric 305x305

Machine direction

Fabric 203x203

Glass fiberboard

All dimensions in mm

Figure 14. Mini-Mockup Test Arrangement for Cigarette Ignition

Cigarettes are generally placed into the crevice

92
APPENDIX A. Test Methods for Determining Cigarette Ignition

Resistance of Soft Furnishings

Code of Federal Regulations, Part 1633, Proposed Standards for the

Flammability (Cigarette Ignition) of Upholstered Furniture (PFF 6-81), U. S. Consumer Product Safety Commission (1981)

Important Consumer Information from UFAC , Upholstered Furniture Action

Council, High Point, NC (1985).

The Business and Institutional Furniture Manufacturer's Association First

Generation Voluntary Upholstered Furniture Flammability Standard for Business

and Institutional Markets, BIFMA, Grand Rapids (1984).

Flammability Information Package, State of California, Department of Consumer

Affairs, Bureau of Home Furnishings, North Highlands, CA (1983).

Standard Methods of Tests and Classification System for Cigarette Ignition

Resistance of Components of Upholstered Furniture. (NFPA 260 A) 1986 Standard

Method of Test for Determining Resistance of Mock-up Upholstered Furniture

Material Assemblies to Ignition by Smoldering Cigarettes (NFPA 260 B) , National Fire Protection Association (NFPA) (1983)

Fire Tests for Furniture, Part 1., Methods of Test for the Ignitability by

Smoker's Materials of Upholstered Composites for Seating by Flaming Sources

(1982). British Standard BS 5852, British Standards Institution, London.

The Upholstered Furniture (Safety) (Amendment) Regulations, 1983, No. 519,

Consumer Protection, Her Majesty's Stationery Office, London (1983).

Upholstered Furniture -Burning Behavior- Ignitability of Upholstered CompositesMethods of Test, Part 1, Smokers Materials. Section 1, Cigarette, Section 2,

Small Flame 1, Part 3, Ignition Sources, Butane Flames, Part 4, Larger

Ignition Sources (ISO/TC136/SC1/WG4) Publ . by British Standards Institution,

Manchester, England (1982).

Draft Australian Standard Method of Test for the Ignitability of Upholstered

Seating (DR 80 123) North Sidney, N.S.W. (1980). Method of Test for the

Ignitability of Upholstered Seating of the Low Fire Hazard Type (DR 80-124)

Standards Association of Australia, North Sidney, N.S.W. (1980).

Austrian Standard 5410-A 1606, Part I. Specification for Furniture: Testing

Inflammability of Furniture Surfaces. Oesterreichisches Normungungsinstitut

,

Vienna, Austria.

Irish Standard Specification, Requirement for Smolder and Flame Resistant

Upholstery, I.S. 244; 1980, Institute for Industrial Research and Standards,

Dublin (1980).

Nordtest Fire 014, NordTest, SF 00340, Helsingfors 34, Finland.

1
Furniture Upholstered Seating Method of Test for the Ignitability (by a Smoldering Cigarette), Svensk Standard SS 83 91 30, SIS S tandardiseringgrupp

,

Stockholm, Sweden.

DOE/PSA Fire Retardant Specification, No. 3: Fire Barrier Standards for

Upholstery (Seating and Bedding); No. 4: (Composite Upholstery Ignition

Standard (Seating and Bedding); No. 5: Flammability of Beds and Bedding; No.

6: Ignition Standard for Seating. Department of the Environment/Public

Service Agency, London (Apr. 1978).

Code of Federal Regulations, 16 CFR, Part 1632, Standard for the Flammability

of Mattresses (and Mattress Pads), FF 4-72 (1983).

Method of Test for the Combustion Resistance of Mattress; Cigarette Test.

Canadian Government Specification Board, Ottawa, Ont . Canada, No. 27.7 (1977).

Behavior of Mattresses in Fire: Cigarette Test. Bulletin Official des

Services des Prix, Annexe a la Recommendation No. Dl-78 Direction General de

la Concurrence et de la Confirmation, Paris Dec. 1978).

V»

2
APPENDIX B LIST OF PATENTS

Most of these patents were furnished by Dr. P. H. Leake of the American

Tobacco Company and Dr. A. W. Spears, III of Lorillard, A Division of Loews

Theaters, Inc. A few additional patents were found by searching World

Patents. This list is believed to be reasonably complete.

1
A. U.S. PATENTS

Number Title Date

253,841

1 , 020,864

1 , 211,071

1 , 517,142

1 . 555.320

1 , 581,451

1 . 605.059

1 , 666,062

1 , 726,737

1 . 744.615

1 . 770.616

1 , 798,537

1 , 821,159

1 , 879,128

1 , 905,416

1 , 996,002

1 , 999,222

2 , 013,508

101,312

2 . 049.320

2 , 098,619

2 , 134,213

2 . 147.889

2 , 246,929

2 , 307,088

2 , 327,991

2 , 329,927

2 , 335,432

2 , 526,572

2 , 536,900

2 , 547,119

2 , 607,353

2 , 625,163

2 , 666,437

2 , 679,251

2 , 701,571

2 . 718.889

2 . 746.890

2 , 754,828

2 , 786,471

2 , 788,005

2 . 827.059

Cigar and Cigarette Wrapper

Cigarette

Ash Retaining Cigarette and the Like

Cigarette Holder and Extinguisher

Cigarette

Fire Safe Cigarette

Cigarette

Cigarette

Smoking Article

Cigarette

Cigarette

Cigarette

Attachment for Cigarettes

Cigarette

Cigarette

Decreasing Inflammability of Cigarettes

Cigarette

Difficultly Flammable Cigarette Wrapper

Design for a Combined Cigarette Holder,

Ashtray, and Extinguisher (Design Pat.)

Cigarette

Cigarette

Protective Cigarette Holder

Processing of Tissue or Paper and

the Product Obtained Thereby

Cigarette

Cigarette

Cigar and Cigarette

Method of and Composition for Treating

Cigarettes, Cigarette Paper and Tobacco

Cigarette Extinguisher

Combination Smoker's Mouthpiece and

Ash Receptacle

Snuffer

Cigarette

Cigarette Holder

Safety Cigarette Holder

Cigarette Extinguisher

Safety Cigarette Holder and Cleaner

Device for Smoking Cigarettes

Heat Absorbing and Transferring

Band for Cigarettes

Cigarette Device

Cigarette and Method of Making

the Same

Cigarettes

Cigarette Smoking Device

Cigarette Holder

2 / 21/1882

3 / 19/1912

1 / 2/1917

11 / 25/1924

9 / 29/1925

4 / 20/1926

11 / 2/1926

4 / 17/1928

9 / 3/1929

1 / 21/1930

7 / 15/1930

3 / 31/1931

9 / 1/1931

9 / 27/1932

4 / 25/1933

3 / 25/1933

4 / 30/1935

9 / 3/1935

9 / 22/1936

7 / 28/1936

11 / 9/1937

10 / 25/1938

2 / 21/1939

6 / 24/1941

1 / 5/1943

8 / 31/1943

9 / 21/1943

11 / 30/1943

10 / 17/1950

1 / 2/1951

4 / 3/1951

8 / 19/1952

1 / 13/1953

1 / 19/1954

5 / 25/1954

2 / 8/1955

9 / 27/1955

5 / 22/1956

7 / 17/1956

3 / 26/1957

4 / 9/1957

3 / 18/1958

2
Number Title Date

2,890,704

2,900,987

2,932,301

2,965,107

2,998,012

3,030,963

3,034,932

3,081,776

3,091,243

3,102,543

3,165,105

3,183,914

3,220,418

3,276,453

3,288,145

3,318,314

3,528,432

3,632,384

3,702,117

3,736,940

3,821,958

3,886,954

3,916,916

3,977,416

3,985,143

4,027,680

4,034,767

4,044,778

4,091,821

4,121,597

4,146,040

4,187,862

4,230,131

4,241,742

4,303,084

4,386,616

4,413,638

4,436,101

4,452,259

4,453,553

4,480,650

Cigarette

Ash-Retaining Jacket for a Cigarette

Safety Cigarette Holder Made from

Perforated Paper and Metal Foil

Cigarette Snuffer

Cigarette and Wrapper Therefor

Cigarette Construction

Tobacco Composition

Cigarette Coal Anchor for

Filter Cigarette

Self-Extinguishing Cigarette

Safety Tip Cigarette

Ash-Retaining Safety Cigarette

Cigarette

Cigarette

Cigarette Construction

Tobacco Article

Apparatus for Producing a Continuous

Tobacco Rod

Cigarette or the Like Having

Combustion Stop

Method of Making Cigarette Paper with

Ash-Retaining Means

Cigarette

Cigarette with Ash-Retaining Means

Fire-Proof and Ash-Proof Cigarette

Fire Safety Cigarette

Shield for Cigarettes and Cigars

Cigarette with a Snuffer

Self Extinguishing Cigarette

Safety Cigarette Holder and Ash

Retaining Device

Cigarette Holder

Cigarettes

Smoking Article Having an Ignition

Suppression Disk

Filtering Pipe with Extinguisher

for Cigarettes

Cigarettes

Treatment of Cigarette Paper

Self-Extinguishing Cigarettes

Ashtray to Control Burning Rate

of Cigarette

Self-Extinguishing Cigarettes

Cigarette Tube

Safety Cigarette Bottle

Self-Extinguishing Cigar or Cigarette

Smoking Articles Having a Reduced Free

Burn Time

Treatment of Cigarette Paper

Coated Self-Extinguished Cigarette

6/16/1959

8/25/1959

4/12/1960

12/20/1960

8/29/1961

4/24/1962

5/1V1962

3/19/1963

5/28/1963

9/3/1963

1/12/1965

5/18/1965

11/30/1965

10/4/1966

11/29/1966

5/9/1967

9/15/1970

1/4/1972

11/7/1972

6/5/1973

7/2/1974

6/3/1975

11/4/1975

8/31/1976

10/12/1976

6/7/1977

7/12/1977

8/30/1977

5/30/1978

10/24/1978

3/27/1979

2/12/1980

10/28/1980

12/30/1980

12/1/1981

6/7/1983

11/8/1983

3/13/1984

6/5/1984

6/12/1984

11/6/1984

3
Number

4 , 489,738

4 , 491,139

4 , 521,333

4 , 582,073

4 . 570.645

4 . 570.646

4 , 570,650

4 , 572,217

4 , 582,073

4 , 585,014

4 , 615,345

06 / 627,710

06 / 877,803

7045

Title

Self - Extinguishing Cigarettes

Self - Igniting Smoking Device

Intumescent Silicates Having Improved

Stability

Self - Extinguishing Cigarettes

Safety Holder for Cigarettes

Method and Apparatus for Smoking

Self -Extinguishing Cigarette

Fire-Safe Cigarette Holder System

Check Valve Type Cigarette Mouthpiece

Fire Inhibiting Tubular Safety Shield for

a Cigarette Type Smoking Device and

Combination Thereof

Self -Extinguishing Cigarettes

Reduced Ignition Proclivity Smoking

Article Wrapper and Smoking Article

NOTE: This is an application

Smoking Articles

NOTE: This is an application

Wrapper Constructions for Self-Extinguishing

and Reduced Ignition Proclivity Smoking

Articles ' NOTE: This is an application

Date

12 /25/1984

1 /1/1985

6 /24/1986

8 /17/1984

2 / 18/1986

2 /18/1986

2 /18/1986

2 /25/1986

4/15/1986

4/29/1986

10/ 7/1986

7 /11/1986

6 / 24/1986

9 / 26/1986

4
B. FOREIGN PATENTS

Country Number Title Date

Australia 149,216 Improvements in Cigarettes with

Filter Plugs or Other Internal

Mouthpieces and Methods and

Machinery Used in Their Production

1/24/1951

Belgium 659,839 Improved Cigarette 6/16/1965

France 1,040,981 Safety Devices for the Use of

Smokers

10/20/1953

France 1,402,088 Smoking Article 5/3/1965

France 1,446,152 Device for Automatically

Extinguishing the Burning

Ends of Cigarettes and Such

7/6/1966

France 1,517,262 Safety Process Designed to

Prevent and Reduce Damages and

All Types of Accidents Caused

by the Ashes from a Burning

Cigarette

3/15/1968

France 1,537,845 Cigarette with Ash-Retaining Paper

and Process for Its Manufacture

8/30/1968

France 1,553,960 Automatic Cigarette Extinguishing 1/17/1969

France 1,560,360 Cigarette Improvements 3/21/1969

France 1,590,223 Process and Means for the

Manufacture of Cigarette Papers

with a Perforated Flameproof

Network: Papers and Cigarettes

Obtained by These Processes and

Means

5/22/1970

France 2,044,336 Process and Means for the

Manufacture of Cigarette Papers

with a Perforated Flameproof

Network; Papers and Cigarettes

Obtained by These Processes and

Means

2/19/1971

France 2,177,138 Process for the Manufacture of

Cigarette Paper with a Perforated

Fireproof Network

11/2/1973

Germany 531,768 Medium for Extinguishing the

Remainder of a Cigarette

8/14/1931

5
Country Number Title Date

Germany 549,936 Extinguishing Cigarette 5/3/1932

Germany 608,407 Cigarette 1/23/1935

Germany 1,663,652 Cigarette Extinguishing Device 11/11/1967

Germany 1,959,684 Self -Extinguishing Smoking

Article

6/3/1971

Germany 2,906,417 Self -Extinguishing Filter

Cigarette

2/20/1979

Germany 3,429,275 Smoking Article 8/8/1984

Great

Britain

19,694 Improvements in Cigars

Cigarettes, or the Like

5/15/1913

Great

Britain

22,161 Improvements in the Manufacture

of Cigarettes, Cigars, and

Similarly Used Tobaccos

9/25/1902

Great

Britain

340,884 An Ash-Retaining Attachment for

Cigarettes

1/8/1931

Great

Britain

421,236 Improvements in and Relating to

Cigarettes

12/17/1934

Great

Britain

805,693 Improvements in or Relating to

Cigarettes

2/22/1956

Great

Britain

909,699 Improvements in or Relating to 10/31/1962

Tobacco, Reconstituted Tobacco, or Cigarette Paper and Products Thereof

Great

Britain

1,113,941 Improvements in or Relating to

Cigarettes and Like Smokable

Articles

5/15/1968

Great

Britain

1,214,319 Improvements in or Relating to

Mouthpiece Cigarettes and Like

Smoke Articles

12/2/1970

Great

Britain

2,175,189 Self Extinguishing Cigarette 11/26/1980

Japan 58-146,269 Self-Extinguishing Cigarette 8/31/1983

J apan 58-183,084 Self-Extinguishing Cigarette 10/26/1983

Japan 58-183,085 Self - Extinguishing Cigarette 10/26/1983

6
Country Number Title Date

Japan 59-14,781 Cigarette with Fire Extinguisher 1/1/1984

Switzerland 142,429 Cigarette 11/17/1930

Switzerland 240,987 Extinguishing Mechanism on Manufactured Smoking Articles

6/1/1946

Switzerland 348,094 Filter for Cigarettes, Cigars,

Pipes and the Like

9/15/1960

World Patent 8,604,488 Self-Extinguishing Cigarette 8/14/1986
FOAM NBS-1 14A (REV. 1 1-84)

2. Performing Organ. Report No. 3. Publication Date April 1987

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

repost wn NBSIR-87/3509

4. TITLE AND SUBTITLE

CIGARETTE IGNITION OF SOFT FURNISHINGS - A LITERATURE REVIEW WITH COMMENTARY

5. AUTHOR(S) John F. Krasny

I. PERFORMING ORGANIZATION (If joint or other than NBS„ see in struction s)

NATIONAL BUREAU OF STANDARDS

U.S. DEPARTMENT OF COMMERCE

GAITHERSBURG, MD 20899

7. Contract/Grant No.

8. Type of Report & Period Covered

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

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

bibliography or literature survey, mention it here)

\ Literature pertinent to the ignition by smoldering cigarettes of upholstered

furniture and mattresses (soft furnishings) was searched through early

This included literature on the smoldering behavior of cigarettes m air; their

behavior on a variety of substrates simulating soft furnishings; mechanism of

smoldering in substrates; relative cigarette ignition resistance of substrates,

and relative propensity of commercial cigarette packings to ignite . substrates

.

According to the reviewed literature, the smoldering behavior of cigarettes on substrates differs from that of cigarettes burning in air: on substrates,

cigarette temperatures tend to be lower, and burning rates slowe r. ese differences seem to be larger for substrates which ignite than for those whic

self -extinguish after the cigarette burns out. The characteristics of so furnishings which insure resistance to cigarette ignition have been

established, but those of cigarettes with low propensity to ignite furnishings

have not. No mathematical model has been reported, for the interaction of

cigarette and substrate, but some empirical data do exist.

12, KEY WORDS (S/x to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Cigarette combustion; flammability tests; ignitability of soft furnishings;

mattresses; smoldering combustion; upholstered furniture.

13, AVAILABILITY

X Ugl united For Official Distribution. Do Not Release to NTIS

Order From Superintendent of Documents, U.S. Government Printing Office, Washington, DC

"" 20402.

jr Oxder From National Technical Information Service (NTIS), Springfield, VA 22161

14. NO. OF

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108

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