Fire Behavior of Upholstered Furniture and Mattresses

434 Pages·2000·3.782 MB·English

by  John F. Krasny, William J. Parker and Vytenis Babrauskas (Auth.)

Preface
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This book is a collection of the up-to-date science and engineering
knowledge in the field of furniture fire flammability. For continuity and
perspective, citations to older work are still maintained, even in cases where
newer research has brought forth improved methods or better knowledge.
Thus, the advancement of the state of the art can be seen in these pages.
In 1985, two of the present authors (Babrauskas and Krasny)
published the first monograph devoted to upholstered furniture flammability.
This was issued by National Bureau of Standards (now NIST, National
Institute of Standards and Technology) as “Fire Behavior of Upholstered
Furniture” (NBS Monograph 173). Many new concepts and experimental
results have been published since that time. The most comprehensive recent
research study in this area has been “Combustion Behavior of Upholstered
Furniture” (CBUF) which was sponsored by the European Union. Two of
the authors, Babrauskas and Parker, had the privilege of participating in
CBUF. This project, as well as many others, resulted in major improvements
in this field. Thus, it became opportune to revise the monograph.
To be most useful to its intended user, this book was reorganized and
structured more along the expected lines of enquiry from the user. This
involved a major reexamination of the literature, especially coverage of new
regulations and standard test methods. The review of regulations, however,
is selective. Discussions are focused only on US, UK, and EU activities in
this area. While numerous other countries have various regulations affecting
v
vi Preface
aspect of furniture flammability, little if any technical work making reference
to such regulations has ever been published in the English language.
In this book, the term upholstered item will sometimes be used to
include upholstered furniture as well as upholstered parts of bedding (solid
core and innerspring mattresses and upholstered bed frames). In many
cases, however, it is appropriate to consider that statements made about
chairs or about upholstered furniture also apply to various other types of
upholstered items. Bedding, such as blankets, sheets, pillows, etc., are
treated separately.
The book is arranged as follows:
• Chapter 1 provides a brief overview of the structure and
materials, fire safety design, fire statistics, and standards
development.
• Chapter 2 discusses some of the fundamentals of fire
which affect the fire safety of upholstered furniture.
These include smoldering and flaming ignition, flame
spread, heat release, inter-item fire spread, room-fire
interaction, flashover, smoke, and toxic gases.
• Chapter 3 describes the pertinent test methods and
regulations for smoldering and flaming ignition, flame
spread, heat release rate (HRR), and smoke and toxic gas
production for residential, public, and high risk occupan-
cies.
• Chapter 4 addresses smoldering and flaming ignition and
includes the historical development and the details of the
ignition tests.
• Chapter 5 compares results obtained by different test
methods, especially bench-scale and full-scale results,
and furniture calorimeter and room results.
• Chapter 6 covers fire safety design, considering the
effects of upholstered item construction and materials,
separately for smoldering (cigarette) and flaming ignition.
Emphasis is on thermal behavior, flaming or smoldering;
the relative rates of smoke and combustion products
release, which are, in the first approximation, related to
the HRR for flaming fires, are less extensively reviewed.
Preface vii
• Chapter 7 briefly discusses room fire zone and field
models as they pertain to furniture fires, furniture fire
models, and correlation formulas, and a method for
predicting the HRR of composites in the Cone calorim-
eter based on measurements of the individual compo-
nents.
• Chapter 8 discusses fire hazard analysis, and describes a
method of predicting the available escape time based on
the HRR of the burning furniture.
• Chapter 9 offers brief conclusions about the current state
of knowledge about furniture flammability.
July, 2000 Vytenis Babrauskas
Issaquah, Washington
Introduction 1
1
Introduction

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This book is a comprehensive revision of a 1985 monograph[1]
authored by Babrauskas and Krasny. The intervening years saw few
advances in the basic science of furniture combustion, but much work was
done in applied areas, both in empirical studies and in regulatory activities.
Thus, this edition is organized differently from the preceding book, and is
specifically intended to provide useful information to any individuals with
a responsibility for the fire safety of furniture.
Research from various parts of the world are encompassed in this
book, but focus on regulation is mainly from the US perspective, with
significant additional material on UK and EU activities, and more limited
coverage of other parts of Europe. Other, briefer, overviews of the uphol-
stered item fire situation in the UK and the US are found in Refs. 2–6.
A comprehensive report on the results and analysis of an extensive
European project on the post-ignition Combustion Behavior of Uphol-
stered Furniture (CBUF)[7] references many important literature sources.
This chapter contains an overview of the basics of upholstery
structure and fire safety design. Following this, fire statistics are presented.
1
2 Fire Behavior of Upholstered Furniture and Mattresses
The chapter concludes with a brief history and status of US and EU
regulations covering upholstered furniture and mattresses.
1.1.0 � UPHOLSTERED FURNITURE STRUCTURE AND
MATERIALS
Upholstered furniture has a complex structure, as shown in Fig.
1-1. One item can contain fifteen or more components. In the ignition
process, whether it be from a cigarette (smoldering ignition) or small flame,
the cover and interliner fabric, if any, and material immediately below them
(one or several different padding materials) are important. As the fire
progresses, other materials contribute, including the bulk of the padding as
well as the frame, staples, and springs, which can affect the manner in which
the burning item collapses. This in turn affects fire growth. Bedding
(pillows, blankets, sheets, etc.), mattresses, and bed frames contain a
different variety of materials and construction factors.
A large variety of component materials are used in upholstered
furniture and mattresses. Cover fabrics can be made from char-forming
fibers, such as cellulosic, acrylic, wool, and silk fibers, or from thermoplas-
tic fibers. Among the cellulosic fibers, cotton and rayon predominate but
flax, hemp, jute, etc. are also used. Thermoplastic fibers include nylon,
olefin (polypropylene or polyethylene), and polyester. Fabrics using blends
of more than one fiber type have become very popular in the last decade.
Fabrics often contain dyes and dye auxiliaries, print auxiliaries, and other
finishes, e.g., stain and water repellents, and softeners. Raw cotton fabrics
contain smolder promoting alkali metal ions, as do many of the fabric
finishing agents. Many fabrics have latex back-coatings.
Paddings today are predominantly polyurethane foams varying in
density and additives. Polyurethane may be used as a thin layer combined
with other paddings, or, more frequently, as the entire core. Cellulosic
batting (mostly cotton but also containing hemp, jute, etc.), both untreated
or flame retarded treated (FR), and cotton/man-made fiber blend batting are
also used. Polyester batting is popular for special comfort and appearance
effects.
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d
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Figure 1-1. Upholstered furniture construction details.
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4 Fire Behavior of Upholstered Furniture and Mattresses
Interliners (also often called barrier materials, fire blockers, or
blocking layers) are used between the cover fabric and padding to increase
ignition resistance and improve burning behavior. For cigarette ignition
resistance, thin layers of polyester batting are popular (paddings of 100%
polyester batting are less widely used; they tend to have excessive loft and
are mostly found in uses other than seats). Flame-resistant interliners are
FR-treated cotton, aluminized materials, glass fabrics, layers of FR foams,
aramid non-wovens, etc.
In addition, furniture and mattresses often contain innersprings,
frames (mostly wood or steel, but sometimes rigid polyurethane or high-
density polypropylene), springs, or straps to hold up cushions, bottom cover
fabrics (usually nonwoven or cotton fabrics), nails, and staples.
1.2.0 UPHOLSTERED FURNITURE AND MATTRESSES
Many aspects of flammability are similar for upholstered furniture
and mattresses. The similarities and differences pertinent to predicting the
fire performance have been analyzed in Ref. 8.
Upholstered items in residential or public occupancies, or air,
maritime, and ground transportation are all subject to different functional
requirements and regulations.
Upholstered items include a large variety of constructions: three-or-
two seat sofas, chairs, mattresses, and some bedframes. The furniture
geometry can have a large effect on progress of the fires. There are fully
and partially upholstered types, recliners, and lightly upholstered office and
stacking chairs. Chairs or sofas can have straight or curved sides, the seating
area can be square or rounded (barrel chairs), there may or may not be
upholstered armrests, etc. Loose or puckered cover fabrics have appeared
in recent times, and their effect on flame and cigarette ignitability has not
been established. There are also such features as open or padded seat sides,
open spaces between seat and backrest, etc.
Mattresses have predominantly flat, horizontal surfaces which are
not as easily ignited from flame ignition sources as the vertical surfaces.
Upholstered bed frames (divan bases) are more common in Europe than in
the US. Both mattresses and upholstered furniture may have depressions
at the welt cord and, due to tufting, these may affect cigarette ignition
propensity.
Introduction 5
Cigarettes on mattresses may be covered inadvertently with sheets,
blankets, and/or pillows. This increases the probability of smoldering
ignition. These intermediary materials may also ignite more readily than
mattresses from flames, and then expose the mattress to a much more severe
fire than the original ignition source, e.g., a match. Fire development is also
affected by the nature and materials of the bed frame. Consequently, it is
more difficult to develop relevant ignition tests and standards for bedding
than for upholstered furniture, which is not usually covered by extraneous
items.
1.3.0 DESIGN AND FIRE SAFETY
While fire problems with upholstered furniture have been of
concern for some decades, it has been mainly since the 1970s that quanti-
tative data have been available for common materials used in upholstered
items. These efforts have made it possible to treat the subject as a design or
prediction problem. In a design problem, the designer is typically required
to come up with materials and configurations suitable to meet a set
objective, which may be resistance to ignition by cigarettes, resistance to
small or large flames, or, smoke and toxic pyrolysis product release rates
below some specified amount. Several means of solving such problems are:
1. � Test items made from the same materials, in the
same configuration, as the proposed line of
furniture in a full scale facility, e.g., a room or
furniture calorimeter;
2. � Test large-scale mock-ups of the fabric,
interliner, and padding;
3. � Test bench-scale composites of the materials in
item 1 and use the results in a full-scale model or
correlation formula;
4. � Test the fabrics and foams individually and use
the results in a composite model or correlation
formula to predict the results of tests of furniture
composites in the Cone Calorimeter. However,
the tests on the individual components require
6 Fire Behavior of Upholstered Furniture and Mattresses
modified test procedures in the Cone Calorim-
eter which are not, at this writing, generally
available in the testing laboratories; although
the testing protocols are described in the CBUF
report.[7]
In the last years, much progress has been made to eliminate the
burden of full scale testing of every material/configuration combination a
manufacturer may wish to produce, and to place greater reliance on strategy
3 and, possibly, strategy 4. At the end of this chapter, an overview is given
of the CBUF project which is the latest of such efforts. Details of CBUF and
other available literature on this subject are reviewed in Chs. 5, 6, and 8.
Briefly, it is now possible, within certain limits, to estimate from bench-
scale tests of both mattresses and upholstered furniture fabric/padding
composites whether the actual item will support a smoldering or a flaming
ignition and whether the flaming ignition will lead to a fully involved fire.
Such estimates can be used to decide whether certain regulatory pass/fail
levels can be met. Progress has also been made in predicting the heat release
rate (HRR) of propagating furniture and mattress fires.
1.4.0 UPHOLSTERED ITEM FIRE STATISTICS
During the 1991 to 1995 period, there was an average of 446,700
home fires, 3590 civilian deaths, 20,382 civilian injuries, and $4.5 billion
property damage.[576]–[579] This is a decrease of almost 150,000 fires from the
1983–1987 period, and of a 19% decrease in civilian deaths. However, the
number of deaths per 100,000 fires has not been decreasing. Furthermore,
the number of civilian injuries and property damage increased during this
period. Civilian deaths may be reduced by better medical treatment, and the
increase in property damage can perhaps be explained by the 1991 Oakland,
CA, firestorm.
The table below shows the number of fires, deaths, injuries, and
property damage due to upholstered item fires. As in earlier such compila-
tions, these fires were by far the largest cause of fire deaths; ranked high in
injuries and relatively low in property damage. While together they
represented only about 10% of the fires, they caused about 35% of the
deaths; this indicates that upholstered item fires are considerably more
likely to cause death than other categories.
Introduction 7
Death, Injuries, and Damage Due to Fires in Which
Upholstered Items Were The First Item to Ignite
Number Civilian Civilian Direct Property
of Fires Deaths Injuries Damage, Million$
Upholstered Furniture
1985–1989 14,600 658 1810 237
1989–1993 16,000/3.4* 742/19 1967/9.4 239/5.5
1992–1996 13,900/3.2 653/18 1721/8.7 228/5.3
Mattresses and Bedding
1985–1989 39,000 774 3050 283/
1989–1993 31,200/6.7 627/16 3232/16 331/7.6
1992–1996 28,900/6.5 578/16 2997/15 320/7.4
*The number after the slash indicates the percent of the total fires, deaths, injuries,
or property damage.
Note: The next lower first item-to-ignite category was electrical insulation, 7.7%
of fire deaths, followed by floor covering and cooking materials, 3.5% each.
Cigarettes or “discarded material,” presumably matches, account
for 39% of the upholstered item fires and 52% of deaths dues to upholstered
items. Incendiary fires were next in frequency. People falling asleep while
smoking accounted for 13% of the fires.
For mattresses and bedding, 56% of fires occurred on items with
cotton fabrics, 24% in man-made fiber items, while the fabric was
unclassified or classified “other known” in 20%. Children started 8700
(30%) fires, and smoking materials and matches or lighters, 5800 (20%).
People falling asleep again were a major factor in these fires, with 1700
(6%) fires.