Reference

NBS

Publications

Allios fia?PS3

NBSIR 81-2261

Review of Literature, Applicable

Test Methods, and Incident Data

for the Evaluation of the Fire

Performance of Central Telephone

Office Equipment

Emil Braun

Center for Fire Research

National Engineering Laboratory

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

May 1981

Final Report

Prepared for: GO 1 ural Electrification Administration

.S. Department of Agriculture

Washington, DC 20250

i 31-22G1

1931

NBSIR 81-2261

REVIEW OF LITERATURE, APPLICABLE

TEST METHODS, AND INCIDENT DATA

FOR THE EVALUATION OF THE FIRE

PERFORMANCE OF CENTRAL TELEPHONE

OFFICE EQUIPMENT

K'ATtOJVAL BUREAU

or rrAHDARoa

LIBRA**

JUL 2 0 1981

/}]£)/ OJLA - C c too

> U50

iS) a rsy, o

/ 1 0 t X/ w Z 7

Emil Braun

Center for Fire Research

National Engineering Laboratory

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

May 1981

Final Report

Prepared for: Rural Electrification Administration

U.S. Department of Agriculture

Washington, DC 20250

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

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
>r. «' HTA \ i--A \l'r

; .* t„: A t* IS t

?

i

[
TABLE OF CONTENTS

Page

LIST OF FIGURES iv

LIST OF TABLES iv

Abstract 1

1. INTRODUCTION 1

2. BELL SYSTEM FIRE PERFORMANCE REQUIREMENTS 2 2.1 Bell System Protocol - Small-Scale Tests 3 2.1.1 ASTM D 2863 3

2.1.2 ASTM E 136 3 2.1.3 ASTM E 84 6

2.1.4 UL 94 6 2.2 Bell System Protocol - Large-Scale Test 7

3. GENERAL FIRE TESTS 7 3.1 Ease of Ignition 8 3.2 Flame Spread 11

3.2.1 Sheet Materials 11

3.2.2 Wire and Cables 11

3.3 Rate of Heat Release 13

3.4 Ease of Extinguishment 13

3.5 Smoke Evolution and Toxic Gas Production 13

3.6 Fire Endurance 14

4. LITERATURE 14

4.1 Polymeric Materials 15

4.2 Wire and Cables 15

4.2.1 Cable "Poke Thru" 15

4.2.2 Flame Propagation 17

5. FIRE SCENARIOS 18

5.1 Incident Data 19

5.2 National Fire Protection Association 25

5.3 Bell System Statistics 29

6. CONCLUSIONS 29

7. REFERENCES 31
LIST OF FIGURES

Page

Figure 1. NFIRS classification of telephone exchange fires 20

Figure 2. Classification of telephone fires as reported in NFIRS

by area of origin 21

Figure 3. Distribution of telephone exchange fires as reported to

NFIRS by the equipment involved in the ignition 22

Figure 4. Description of the extent of flame damage caused by

telephone exchange fires as reported in NFIRS 23

Figure 5. Description of the extent of smoke damage caused by

telephone exchange fires as reported in NFIRS 24

Figure 6. Type of equipment failures in electronic rooms, service

facilities, and ducts as reported by NFIRS 26

Figure 7. NFIRS data on the form of energy release causing ignition

in electronic and electrical facilities of telephone

exchanges 27

Figure 8. NFIRS data on the form of material initially ignited in

electrical and electronic facilities of telephone

exchanges 28

LIST OF TABLES

Table 1. List of test methods used by Bell Systems for

procurement of central office equipment and cables 4 Table 2. List of compounds and typical values for the oxygen index

(based on reference 3) 5

Table 3. Summary of ignition tests 9

Table 4. Summary of flame spread tests 12
REVIEW OF LITERATURE, APPLICABLE TEST METHODS, AND

INCIDENT DATA FOR THE EVALUATION OF THE FIRE

PERFORMANCE OF CENTRAL TELEPHONE OFFICE EQUIPMENT

Emil Braun

Abstract

At the request of the Rural Electrification

Administration, a program was initiated to evaluate the

adequacy of current flammability specifications for

electrical equipment used in telephone company central

offices. The high reliance on telephone services for

emergency communications necessitates that measures be

considered to minimize the likelihood of fire related

interruptions of service. This report provides a review

of current test methods and specifications for central

office equipment; a review of available fire test

methods in various categories; a brief literature review

of relevant fire research and fire testing of wiring,

cables, and assemblies; and a review of fire incident

data

.

Key words: Central office equipment; electronic

equipment; fire test methods; incident data;

telecommunications; telephone exchanges.

1. INTRODUCTION

At the request of the Rural Electrification Administration (REA) , United

States Department of Agriculture, the Center for Fire Research (CFR) initiated

a program to evaluate the adequacy of current flammability specifications for

electrical equipment used in telephone company central offices. In addition

to preventing personal injury, the primary concern regarding fire incidents in

central telephone offices is the reduction of potential interruption of service

to subscribers for an extended period of time. The high reliance on telephone

services for emergency communications, particularly in rural areas, necessitates that measures be considered to minimize the likelihood of such an event.

1
The Rural Electrification Association has the federal authority to fund,

via a financial loan program, the construction of telephone central offices.

Along with this funding authority, REA has the obligation to ensure that standards and specifications for equipment and materials are met. Recent fire

incidents which have occurred in central telephone offices have indicated that

a need exists to review current flammability specifications for materials used

in central office equipment.

The Center for Fire Research's objective is to review the potential fire

problem associated with materials exposed to possible ignition sources in

central offices and to determine whether existing specifications and accepted

small-scale flammability test methods properly address these potential problems.

At the conclusion of the program, recommendations will be made to REA concerning the viability of existing test methods to provide the necessary level of

fire safety. If these test methods do not meet the minimum requirements for

fire safety, alternative test methods will be recommended.

This report represents the completion of the first phase of a multiphase

program. It provides a review of current Bell System test methods and specifications for central office equipment; a review of available fire test methods

in various categories; a brief literature review of relevant fire research and

fire testing of wiring, cables, and assemblies; and a review of fire incident

data

.

2. BELL SYSTEM FIRE PERFORMANCE REQUIREMENTS

The recognized authority in the field of telecommunications is AT&T's

Bell Laboratories. Over the years they have developed a series of product

material and purchase specifications that cover every aspect of telephone

system design. Included in these specifications are test methods and criteria

believed by Bell Laboratories to provide an adequate level of fire performance

in the design and assembly of new equipment and cabling. Bell System specifications and procedures for qualification fire testing appear to be followed

by all manufacturers of central office equipment.

Bell System specifications [ 1

]

1 are intended to provide a screening

procedure that will result in the selection of polymeric materials for new

equipment and cabling assemblies that exhibit fire retardant characteristics.

Numbers in brackets refer to the references at the end of this report.

2
The desired end-point in this testing program is that a fire originating in

the equipment racks of a central office be confined to the equipment rack of

origin and not spread to adjacent frame assemblies. Furthermore, the fire's

size should not grow beyond that which could be controlled by a hand-held

fire extinguisher. This goal is presumably achieved either by performing

several small-scale fire tests on equipment components or by conducting

assembly fire tests that duplicate actual material configuration and operating conditions. Four small-scale fire tests are quoted by Bell System specifications. Table 1 is a list of these test methods. The acceptance criterion

is also listed for each test method.

2.1

Bell System Protocol - Small-Scale Tests

The small-scale fire test protocol defined by the Bell System requires

that all materials be tested by ASTM D 2863-70, "Flammability of Plastics

Using the Oxygen Index Method" [2]. According to Bell System specifications,

materials tested by this method must exhibit a minimum oxygen index of 28.

The material must also meet the minimum requirements of one of the three

remaining tests.

2.1.1

ASTM D 2863

This test method determines the minimum concentration of oxygen in a flowing mixture of O

2 /N

2 necessary to support flaming combustion on a polymeric rod of prescribed size. Oxygen Index (01) values can range from

approximately 14 to 70. A large number of polymeric compounds are available

that have 01 values in excess of 28. Many, however, are not suitable for

telecommunication applications. Table 2 lists several compounds that meet

or exceed the minimum requirements and may be used in the assembly of electronics equipment. Two common compounds found routinely in electronic equipment are polyvinyl chloride and epoxy. Both compounds can be formulated to

have an 01 greater than 28.

2.1.2

ASTM E 136

This test method [4] defines noncombustibility of materials in terms of

temperature rise, flaming, and weight loss criteria. Specimens of polymeric

materials are inserted into a vertical tube furnace at 750 °C. Two thermocouples are used to monitor the temperature response of the sample. A sample

passes the test if at least three of the four specimens do not exhibit a temperature rise in excess of 30 °C above the initial operating temperature of

3
Table 1. List of test methods used by Bell Systems for

procurement of central office equipment and

cables

Test Designation Title

Acceptance

Criterion

ASTMa

D 2863-70

ASTM E 136-73

ASTM E 84-74

ULb94

Flammability of Plastics Using

the Oxygen Index Method

Test for Noncombustibility of

Elementary Materials

Surface Burning Characteristics

of Building Materials

Test for Flammability of Plastic

Materials

>28

Noncombustible

I S ±25

S D <50

VE - 0

VE - 1

American Society for Testing and Materials

Underwriters Laboratories

4
Table 2. List of compounds and typical values for the oxygen index

(based on reference 3)

Materials Oxygen Index

Polyvinyl chloride 40

ABS 30

Teflon 95

Polyvinylidene fluoride 40

Polybenz imidazole 40

Aromatic polyamide 28

Nylon 28

Polyimide 36

Polycarbonate 30

Polysulfone 35

Phenolic 40

Epoxy 33

Alkyd >29

Silicone rubber >30

5
the furnace and there is no flaming from the specimen after the first 30

seconds. In addition, if the weight loss of the specimen exceeds 50 percent,

then the specimen cannot flame or have a temperature rise above the initial

furnace temperature.

2.1.3 AS TM E 84

This test method [5] measures the surface burning characteristics of a material by evaluating the flame spread over its surface when exposed to a test fire. Smoke density is also evaluated at the same time. Samples (7.3 m

long) are mounted face down on the ceiling of the horizontal test chamber. A

flame from the test fire is impinged on the specimen surface. The rate of

flame spread and smoke evolution are recorded. Flame spread classification

is proportional to the total area under the flame distance-time curve. For

smoke evolution, the area under the smoke density- time curve is computed.

This value is normalized by the smoke produced by red oak. Although E 84 is

intended for building materials and not for cables. Bell System has modified

the test and established acceptable fire performance for cables in this test

to be a flame spread rating less than 25 and a smoke developed rating of not

more than 50 (see section 4.2.2 and [4]). These are values commonly used in

building codes to regulate interior finish materials in exitways and in

critical areas of many types of occupancies.

2.1.4 UL 94

This standard [6] contains five test methods. The method cited in Bell

System purchase specifications is the vertical burning test for classifying

polymeric materials according to their ability to resist ignition — 94V-0

and 94V-1. This test method exposes a vertically supported specimen to a bunsen burner type flame. Two successive 10-second exposures are applied to

each 127 mm long specimen. A total of five specimens is tested. Dry absorbent surgical cotton is placed beneath the test specimen to determine the

ignitability of molten drips. In order to receive a 94V-0 classification, a sample must not have a total afterflame time exceeding 50 seconds or an individual specimen afterflame time greater than 10 seconds. Glowing combustion

is limited to 30 seconds or less for each specimen and no specimen can release

flaming drips that ignite the surgical cotton.

A 94V-1 classification differs slightly from the preceding in that longer

times are allowed for total afterflame, individual after flame, and glowing

combustion. They are 250, 30, and 60 seconds, respectively.

6
2.2 Bell System Protocol - Large-Scale Test

If materials are used that either have not been tested by the smallscale tests or have failed to meet the requirements of the small-scale

protocol, large-scale fire tests are required on actual equipment and

cable distribution assemblies. The assembly fire tests are intended to

duplicate actual material configurations and operating conditions. The

objective of the large-scale test is to ensure that if an ignition were

to occur in a system, it would be confined to a vertical section of equipment delimited by the vertical frame supports. The assembly should also

demonstrate that a large fire could not develop. A large fire is defined

as one that could not be extinguished by a handheld fire extinguisher

(Class 5B:C extinguisher, e.g., 10 lb. C0

2

)

.

Communications cable and distribution assemblies have the added

requirement that they must be able to limit flame spread to 6 inches

horizontally and 4 feet vertically before self-extinguishing.

3. GENERAL FIRE TESTS

While no federal agency has adopted fire performance requirements

for central telephone office equipment, there exists a large selection

of test methods that may be appropriate for the evaluation of central

office equipment. Many tests have been developed for electrical cable

insulation. Fewer test methods exist for the characterization of fire

properties of polymeric materials for electrical applications. The

National Materials Advisory Board [7] has compiled a general list of

fire test methods. They divided the various test methods into nine

categories

:

1 . Ease of ignition;

2. Flame spread;

3. Rate of heat release;

4. Minimum oxygen requirement;

5. Smoke evolution;

6. Ease of extinguishment;

7 . Toxic gas emissions;

8. Fire endurance;

9. Full- scale tests.

7
Specific tests in each of the first seven categories are intended to determine

a different material response under well defined exposure conditions. These

measurements, however, do not necessarily represent fundamental material properties. The test results are affected by the geometry of the sample (e.g.,

specimen size, thickness, surface orientation, etc.) and changes in the

sample's environment (e.g., airflow, humidity, etc.). The selection of appropriate test methods is governed by a need to maximize specific fire attributes

of a material. Specific fire attributes are chosen for maximization based on

a set of exposure conditions defined by a probable scenario for machine failures that could lead to ignition. At the present time, end-use conditions are

ill-defined for most applications of these tests. The exception is the recent

issuance of guidelines for conducting full-scale tests [8] and the development

of several full-scale test methods [9,10] that are intended to evaluate wallfinish materials and furnishing for residential use.

Fire endurance tests are normally designed to evaluate structural

components with regard to their ability to retain fire barrier integrity and

load carrying capacity. With the exception of cable penetration tests, these

tests will not be reviewed in this report.

The test methods reviewed in the following section represent those tests

that are currently available to measure fire properties of materials for electrical applications. The minimum oxygen requirement test will not be discussed

because only one exists and it has previously been described.

3.1 Ease of Ignition

The ignition of a material is the first stage in the development of a fire. The ease with which a material ignites when exposed to a source of

energy typically encountered in end-use conditions may determine the appropriateness of a material for the stated application. Several tests exist

for the measurement of the ease of ignition of materials used in electrical

applications. Some are listed in table 3. Ease of ignition tests are used

primarily to characterize the ignition times of sheet or rigid polymeric

materials

.

A test designed specifically for ignition measurements on insulated

electric cables does not exist. Some flame spread tests expose electric

cables to a standard heat source for fixed periods of time. These types of

tests have an implicit minimum ignition time.

8
Table

3.

Summary

of

ignition

tests

d

d o 0 •H

cd

dd P 44 0 rH o o O *H

a) o <u

d Q) (U 44

d *H o •H •H tH

d

CO 0 cu *H

u o u 0 d o 44

a 44 44 44

O 00

u •H 0 4-»

d *H P •H

m 0 d •HMH *H '—1

44 -H •H 4-J 4-1 4-J 44

O -H cd

a cd co

d

Cd

p

U

d Cd -H cd 44 44 00

d $3 00 00

U 44

co

a 00

dd

H

d

d rH CO •H 44

M

O *H •H 3 d

d o 00 •H <u oo <u o ud oo •H

O 3 -H 44

X •H

qa -H

a •H c > c CO

O CO 44

O

O rt

X 44 -H X 0 1 0 44 cd cd h d d 44 U O *H 44 44 V-4 CO •H d 0) <U MH a> •H x d d U 0 d p, a d cd a h cd 4-J rH 4-» d CO 44 U 1 -H d 43 X 00 d d Ph rH

00 3 rH

d 00 •hd

U 44 0 0 <U tH 0 0 0 «H

•H 43 44 CO •HX 43H •H

p •H *H

d

cd 44

d 44 44 44

C3

d

dd * > rH > *

CJ

Od o o

00 o T3

M o a co <J 44 0) V 44 CO

•H CN o WHO o <4-1 CN d O cd o cj O cd O (EJ r- d O -H r- U

•H i | 1 o (J

H 1 1 X | 44 CO I j 1 <2J 1 *H 1 1 <3J 1 CO 1 •H J4 3^ x) co co x u x X p 2 CO d m CO 01 3 2 a o CJ P H cj o o 43 ^ cd H o d cd M P &s° o O x) o x > x> O O oo m 4-1 O 44 O LIO vD <r rrH * ' * •

x)d LO

0)

X

a • cd

u

d Ph CN 0 M 0 cd d CO CJ 3 u<3 (J N—'' /-'s '—

CO o 0 H •H CO p> ^ a, /-S O C/3 rH C(j cd rH 00 CJ & 0 a > O CN uo

X

•H •H

dH LO

d cd

u o u vO CO

dO CJ <D

O rH Cd »H

H CO cd <r to ca> cd o a -h > d o p. •H CN C2J rH

•H

u •h

a Cj CHJ S x) o CJ > 44

44 00 4J 4-» Cd

M

X •Hd *H CHJ •H

X

M

•H

d

a o d

d

d

U cd

u P H

M CN cd

X

a •H cud

H *H Cd 44 0 d o 44 Ph 44 • rP

d

00

H rH > 3 44

a CJ <5 44u o 0 a lo 44

M cd

d (3 <4-1 cd co

d <f c0 cOd cd

d ^ 44 cd

d o d rH

d rH o d

X o X

dXd

d

X

X co rH <—1

rH

d *h rH rH cd cd cd rH rH

rH 44 cd cd 44 44 44 cd cd Cu aj a a d C d a a § t; •H 1 •H o O o *H •H 1 co c H I 44 N N N 44 44

C/3 CL)

M

H •H •H *H

uH

•H 0)

d

HH

M

d

d > > O O O > > o X X X

CO co CO

pp CO CO CO CN g d d d

LO (3

x

q 0/ CO CN X X x 3 X § N X • u a 0 CJ • • CN

•H

g | A 0 *H 0 *H i *H

d • C/3 0 0 0 X S rC O J3 N CO 0 00 co 44 44 CO 44 CO 44 CO 44

a* CO CO rH

d

d rH

m

x

rH 1—1 d

d

dd

d & 0 X 43 43 X rH X rH X x 0 X 0 Q cn x CO a P- P- 0 p

cd <r 0 0 u i s 0 0 1 S 0 <r

C/3 0 uo 0 co 44 -H 44 0 cd 0 cd 1 cd *H • 0 CN r» rH tO J2 cd co r- co c5 co x x CO CN rH 44 rH CN CN CO cd rH rH 4-1 4-1 rH rH r>« duP O O 44 x H H cd o <3 3 u X x: d O 44 44 d a x d co rH c 00 0 u H a CN d cd d

4!

H

O

O

H 44

H 44 vD CN d u

X CO

O

up o Hd

C7>

O CN

d x) X) o > cd 0

C/3 CN 43 C^

H

O o P3 •H

a» CN 44 rH

x jd

X 43

X 44

H 0) •H

U 44 44 <c 44 00 00 44 •H

Q 2 Q n) cfl

d

d

O •H •H o d

M nd

a

a 'd'

X 33

X 33 00 2 ^L| cu d H 44 H |H T3 CO CO

C/3 CO CU 44

X rJ

d

<J

C fa C/} d3

XH 9
ASTM D 229 Method II [11] and Federal Test Method Standard Number 406,

Method 2023 [12] describe comparable test procedures for testing the ignition

resistance time of rigid sheet polymers. The specimen is vertically centered

in a heating coil and, during the heating process, it is exposed to an electrical arc until ignition of the core material occurs. The length of time of

exposure is reported as the mean of five specimens. ASTM D 229 Method I also

tests for ignition resistance using a flaming exposure.

Underwriters Laboratories (UL) also has a heated coil ignition test [13]

.

In this method, however, the test material is wrapped with an electrically

heated wire and observed until visible flaming occurs on the test specimen.

This is taken as the ignition time. The physical contact made between the

heated wire and the test material and the lack of a secondary ignition source

distinguishes this method from the preceding two methods.

An alternative approach for measuring ignition resistance is to determine

the self-ignition temperature of a material that may be used in electrical

appliances. ASTM D 1929 [14] measures the minimum furnace temperature necessary to cause a specimen to release combustible gases which will ignite at

the furnace outlet either in the presence or absence of a small pilot flame

(flash ignition or self-ignition) . Electrical appliance designs could then

be reviewed to ensure that these temperatures are not exceeded under worstcase conditions. UL [15] employs a similar type of test as part of their

appliance certification program. The major difference is in how the sample

is heated. The ASTM test uses a controlled airflow while the UL test provides

for natural convection within the flask and conduction through the flask to

heat the specimen to ignition. This can, generally, be used to account for

differences in test results on similar materials.

In addition to the preceding ignition tests, there are so-called "arc

tracking tests" [15] listed in table 3. These tests subject a specimen to

either a high-current arc or a high-voltage arc. The high-current arc exposes

a specimen to repeated applications of a 32.7 amp electric arc. The highvoltage arc test is a low-current 5200 volt source. The length of damage

(e.g., charring) that an applied voltage and current will induce in an insulator is called the tracking distance. Maximum tracking distance is 50.8 mm

or a 5-minute exposure for high-current arcs and a 2-minute exposure for highvoltage. Federal Test Method Standard 406 Method 4011 [16] applies a stepwise

increasing current to 40 ma at approximately 15 KV. The time to initiate

tracking and the current setting are reported. This measurement may be an

indicator of dielectric performance under fault conditions.

10
3.2 Flame Spread

Flame spread tests, which measure the rate of flame propagation or the

extent of burning, can be divided into tests that measure flame spread on

polymeric sheet materials and tests that measure flame spread on wire and

cables. In either case, the intent is to design a test method that would

characterize materials to the extent they could contribute to the growth of

a fire. Any flame spread test presupposes the existence of a fire. The size

of the ignition source used in these tests is an indication of which stage in

a fire's development the test is measuring material performance. With the

exception of ASTM E 84, the tests summarized in table 4 measure material fire

performance at an early stage of fire development.

3.2.1 Sheet Materials

UL 94 [6] previously described represents one of the most complete

schemes for the small-scale testing of polymeric materials. The test methods

outlined in UL 94 measure burning rate in the vertical and horizontal configuration. The rating system developed by UL also recognizes a material's selfextinguishing characteristics. Analogous test methods are ASTM D 635 [17]

and Method 2021 [18] . They measure flame spread rate in a horizontal configuration, while ASTM D 568 [19] and Method 2022 [20] measure a vertical flame

spread rate. While no longer in use for cellular plastics, ASTM D 1692 [21]

is comparable to ASTM D 568 except that a larger specimen is tested.

3.2.2 Wire and Cables

There are two types of wire and cable flammability tests. IEEE 383 [22]

represents a large-scale test protocol, while ASTM D 470 [23] is typical of

a small-scale test. The large-scale tests are conducted with multiple lengths

of cable distributed in a holder in a manner that represents actual end-use

configurations. The fire performance of the entire system of wires and cables

is evaluated. In addition to flame spread, these tests evaluate a cable's

circuit integrity during flaming conditions. Small-scale tests evaluate the

fire performance of a single cable assembly or wire.

Single cable tests such as MS HA 18.64 [24], ASTM D 470, and portions of

UL 44 [25] and J1S C 3005 [26] expose a small section of cable to a bunsen

type burner for a predetermined time period. Either a flame spread rate is

determined or the time to self-extinguish is measured. UL 83 [27], BSI 4066

[28]

,

BSI 6977 [29] , and portions of UL 44 use a vertical configuration and

a bunsen type burner to evaluate single cables.

11
Table 4. Summary of flame spread tests

Test Method Intended Use Sample Size Sample Orientation Ignition Source Conditioning Results

ASTM E 84 cable tray cable rack - 30cm x 594cm horizontal 88 KW burner (20 minutes) - .flame spread

.smoke generation

ASTM D 568 sheet polymer 45cm x 2.5cm x sample thickness vertical bunsen burner

40 hrs @ 23°C,

50% RH or

88 hrs @ 23°C

50% RH

.burn rate

.extent of burning

ASTM D 635 sheet polymer 12.5cm x 1.3cm x sample thickness horizontal bunsen burner - .burn rate

.extent of burning

ASTM D 1692 sheet polymer 15cm x 5cm x <1.3cm

thick horizontal bunsen burner 24 hrs @ 23°C, 50% RH .burn rate

BSI cable (dia <5cm) cable (dia >5cm) 60cm long vertical bunsen burner

two bunsen burners 4 hrs @ 60°C

.burn rate

.exposure time a function of sample weight

BSI 6977 cables 60cm long vertical bunsen burner (60 seconds) 4 hrs @ 60°C

.burn rate

.extent of burning

Federal Test Method

Standard 406

Method 2021 sheet polymer 13cm x 1.3cm x 1.3cm horizontal bunsen burner (30 seconds)

.burn rate

Method 2022 sheet polymer 46cm x 2.5cm x sample thickness vertical .pyroxylin fuse .Benzene drop 2 hrs @ 23 °C .time to burn

specimen

.extent of burning

IEEE 383 cable tray 244cm x >15cm multicables with 1/2 diameter space vertical

.ribbon gas burner

(20 minutes)

.oil soaked burlap -

.extent of burning

.time of burning

.circuit integrity

JIS C 3005 cable 30cm long horizontal bunsen burner (30 seconds).extent of burning

MSHA 30:18.64 cable 91cm long horizontal

Tirrill burner (60 seconds after con- ductor is heated

to 204°C) - .extent of burning

.burn rate

UL 44

cable 25cm long horizontal Tirrill burner (30 seconds)

.extent of burning

.combustible drops

cable 46cm long vertical

Tirrill burner (5-15 second exposures; wait for extinguishment) -

.time of burning

.charring of indicator

cable tray 244cm long, 6 sample lengths vertical ribbon gas burner

(20KW - 20 minutes)

.time of burning

.extent of burning

UL 83 cable 46cm long vertical Tirrill burner (5-15 second exposures)

.time of burning

.charring of indi- cator

UL 94 sheet polymer

horizontal bunsen burner

48 hrs @ 23°C,

50% RH

.burn rate

12.7cm x 1. 3cm x

<1 . 3cm vertical

bunsen burner (repeated 10-second exposure)

.48 hrs @ 23°C

50% RH

.168 hrs @ 70°C cooled 4 hrs

in desiccator

.time of burning

.time of glowing

.combustible drops

12
There is a Japanese standard [26] that measures the tracking resistance

for a vertically configured cable sample. A 4 KV sinusodal test voltage is

applied between the center core and a helically wound outer conductor.

UL 44, UL 83, and IEEE 383 all represent vertical cable tray tests. A

ribbon burner releasing approximately 74 MJ/hr is used as the ignition source.

Recently, Underwriters Laboratory has modified ASTM E 84 for cable testing

[30]. A horizontal cable tray assembly is inserted into the E 84 tunnel.

Modifications were made to the original burner to allow for proper flame

impingement on the underside of the cable tray. Test results are reported

for flame spread and smoke evolution.

3.3

Rate of Heat Release

A rate of heat release calorimeter defines the rate at which a material

contributes heat to a fire when exposed to carefully controlled fire conditions. If an ignition has occurred, this property of a material characterizes

its contribution to the rate of fire growth and thus is a good indication of

the hazard represented. There are several attempts currently underway at NBS

and elsewhere to develop a standard test apparatus and procedure for the measurement of heat release rate. However, no standards organization has yet

formally adopted any of the several test methods being developed. As of

November 1980, a heat release rate test method was tentatively included in

the gray pages of the 1980 Edition of Annual Standards of ASTM.

3.4

Ease of Extinguishment

While the Bell System large-scale test protocol makes provision for

determining that a system assembly will not quickly develop a large fire that

cannot be readily extinguished with a small fire extinguisher, no standard

test method exists to measure quantitatively the ease of extinguishment

characteristics of a material.

3.5

Smoke Evolution and Toxic Gas Production

Hazards due to smoke and toxic gas production have normally been confined

to considerations of occupant egress potential. Current test methods [5,32,

33] for smoke evolution measure either the optical density or the percent

light absorption for smoke produced by a material upon exposure to a standard

energy source. No standard protocol exists for determining the toxicity of

combustion products. Protocols are under development which evaluate animal

responses to the evolved combustion products. In addition, the problem at

13
hand may require the development of an evaluation scheme for determining the

deleterious effects combustion products have on electrical contacts as well

as people. If such a test could be developed for materials manufactured to

meet other test requirements, service interruption could be minimized.

3.6 Fire Endurance

Building codes across the country require that specific barriers within

a building be rated as fire resistive barriers. Barriers (walls, floors, or

ceiling assemblies) are rated without regard to the effects of openings such

as pipes, electrical outlets, or cable penetrations. Central telephone

offices routinely penetrate rated and nonrated barriers with cable "poke-thru."

Communication cables are passed through barriers that separate the cable vault

from the main distribution and switching facility. Within the main distribution facility cables are passed through interior barriers that may not be fire

i rated. Power cables also penetrate some of the same barriers.

In an effort to ensure that rated barriers are not compromised by cable

penetrations, IEEE issued a standard test [21] to qualify cable penetration

fire stops. This standard attempts to rate cable penetrations installed in

rated barriers. Cable penetrations in the test are constructed with the

intended barrier in the end-use configuration. Cable penetration fire stops

are not acceptable if the specified temperature limits are exceeded on the

unexposed side or ignition of the cable or fire stop materials occurs. The

presence of visible flame on the unexposed side within the fire rating time

also constitutes a failure. Ratings are given in terms of hours (or fraction

of hours) of endurance under a standard time-temperature exposure.

4. LITERATURE

The fire performance evaluation of electrical systems has generally been

confined to small-scale tests of polymeric components used in the construction

of these systems. A greater research and development effort has been directed

towards improving the fire performance of wires and cables as compared to

other polymeric components. Generally, wire and cable insulation has not been

identified as the cause of a fire. Insulation has been cited, however, as the

means for fire propagation once a fire has begun. The greatest effort has,

therefore, been directed to developing test methods to evaluate flame propagation potential along a wire or cable assembly. Methods have also been

developed to evaluate installation techniques that would limit flame propagation. The following sections represent a brief review of some of the pertinent

14
literature on fire performance testing; it is recognized that such a review

cannot be complete or exhaustive.

4.1 Polymeric Materials

The literature appears to be devoid of comparisons between full-scale

assembly tests of electrical equipment and small-scale tests conducted in the

laboratory. Thus, leaving the choice of distinguishing acceptable from nonacceptable performance in a small-scale test to extrapolations from other fire

scenarios

.

Miner [34] in reviewing several test methods used to evaluate polymeric

materials noted that a material which exhibited superior fire performance in

one test method would not necessarily perform as well in another test method.

Since material performance is dependent on the test method, the selection

of appropriate test methods must be guided by an understanding of potential

failure modes of the finished product.

Wiktorek [35] characterized the flammability of polymeric materials for

computer application using four different flammability test methods. The

tests were: hot wire ignition test, radiant panel test, oxygen index test,

an IBM in-house test similar to ASTM D 568. He found that, with the exception of the hot wire ignition test, materials maintained their ranking in the

other three tests.

Recent tests on television receivers [36] showed that overload failures,

while producing hot spots in excess of 500 °C, did not result in any ignitions.

Fire tests on the enclosure materials, printed circuit boards, or wires were

not conducted.

4.2 Wire and Cables

The research associated with wire and cable fire performance has been

divided into two parts. First, consideration of flame propagation along wires

and cables, both individually and in bundles. Second, the performance of a firestop (e.g., concrete wall or floor) penetrated by wires and cables.

4.2.1 Cable "Poke Thru"

Cable penetration of a wall is a necessary requirement for moving power

and information from one location to another. Numerous methods have been used

for sealing penetrations in walls and floors. Although sealing with concrete

15
appears to provide an excellent fire barrier, expansion of services and cable

replacement becomes difficult and costly. Work has been conducted on alternate means of sealing "poke thru" holes around cables. Quigg and Orals [37]

performed fire tests on 4-inch and 6-inch thick floor slabs. Using different

hole and slot sizes, they evaluated different sealing methods. They found

that a 1-hour floor rating could be obtained using a gypsum concrete and mineral fiber insulation combination or a Silicone, granular gypsum, and mineral

fiber insulation combination.

McGuire [38,39] found that a small-scale test furnace could be used to

evaluate various penetration schemes for a 6-inch concrete wall. He found

that sleeving cables with thin steel (26-gage) provided better resistance to

heat transfer to the unexposed surface than a 2-inch thick electrical conduit.

It was also noted that the fire performance of larger cables was not as good

as the smaller cables for a 2-hour exposure.

Kita, et al. [40] , describe two sealing methods for cable penetrations in

telephone office buildings. The sandwich sealing tests and the box sealing

tests both proved effective in providing a 2-hour rating in floor furnace

tests. Both methods appear to have the disadvantages of high installation

costs and lack of flexibility.

Kruczek and Cascio [41] developed alternative design standards for cable

vaults that would limit fire and smoke movement. The design standards are

intended for new installations. Fire protection is provided by a perforated

underframe block cast into the floor under the main frame. Each block contains 10 small holes that permit passage of one cable assembly. Because the

smaller holes are limited to one cable, sealing around the cable is easier

and cable bundles are minimized. In addition, shafts, ducts, or sleeves are

recommended for riser cables.

An alternative to standard wall penetrations by cables is suggested by

Peverill [42]

.

His work involved the evaluation of electrical connectors

installed in a fire wall of an aircraft. He showed that a 20-minute fire

resistance connector could be developed with existing technology. These connectors did not degrade the wall's fire stopping capabilities. More improvements in connector design would be necessary before this concept could be

implemented in central office applications.

16
4.2.2 Flame Propagation

The majority of recent research attention has been directed to developing

improved polymers and cable assemblies. These materials and assemblies have

been evaluated by several of the tests previously described. Investigations

of the usefulness of modifications or appropriateness of some test methods

have been conducted as well. Woolerton's [43] work on the use of a heat

release rate test to evaluate the flammability of communications cable is an

example of the latter type of work. Woolerton found that the Ohio State

University Release Rate Apparatus could be modified to measure circuit integrity under fire exposure conditions. Using a mathematical simulation of the

ASTM E 84 test, flammability performance of cables in the tunnel could be

predicted from rate of heat release data.

Beyreis, et al. [44], have modified ASTM E 84 to allow for the

characterization of flame spread and smoke production of cables in a horizontal rack configuration. A cable rack is mounted in the upper part of the

tunnel and exposed to the test burner for 20 minutes. The test sample was a uniform single layer of cable filling the tray width. Kievan, et al. [45],

discusses the difference between a fully loaded cable tray and a single layer

of cables. Kievan concludes that the rate of flame propagation would be much

greater for the fully loaded tray.

Clarke [46] presented an analytical model for cable tray fires. He

concluded that the current tray separation criteria of 5 feet vertical and 3

feet horizontal [22] are marginal for local fires and too small to prevent

fire spread for extended tray fires. Klamerus [47] verified this finding

when he conducted cable tray fire tests using a multiple tray configuration.

He found a fully developed cable fire could propagate across the vertical

separation distance between trays and that installing a shield between trays

effectively reduced the burn area in the upper tray to zero.

Most of the cable and wire flammability tests previously cited are

conducted with no current flowing in the wire or a minimal current for those

cases in which circuit integrity is of concern. (The MSHA cable test is performed with the conducting core at 204°C.) Lupton, et al . [48], demonstrated

that flame propagation and char zone as well as flame time increase with

increasing cable temperature. They suggested that end-use temperature conditions be simulated in any evaluation of cable fire performance.

17
Reports of the development of improved polymers and cable assemblies are

periodically published. New PVC cable systems [49,50] as well as other crosslinked polymers [51] and f luoropolymers [52] have been evaluated. Numerous

test procedures are used to evaluate specific products. Maezawa, et al. [53],

affixed cables to a heat-resistant board and exposed the reverse side of the

board to a standard heating curve. Matsubara, et al . [54], employ a similar

test procedure to evaluate a 0.6 KV and a 6.6 KV cable assembly. Kaufman and

Laudreth [55] used a modified E 84 test to evaluate a flexible PVC cable jacket.

In 1972, the Electrical Research Association [56] reviewed the cable fire

problem and concluded that a set of small-scale fire test methods that are

correlated to full-scale fire performance is required by manufacturers of materials and cables to assess their progress in developing flame-resistant wires

and cables. ERA determined that three aspects of a wire or cable relate to

fire safety: First, the ease with which fire propagates through an installation; second, the production of smoke, corrosive, and toxic fumes; and, third,

the integrity of the circuit. Few wire and cable fire tests measure circuit

integrity. Circuit integrity has been a critical evaluation criterion for

nuclear power plants [45,47]. Nuclear power plants require a minimum time to

sequentially shut down in the event of an emergency. Control circuit integrity

must be maintained throughout this process. The Nuclear Regulatory Commission

has adopted test methods [22] that measure circuit integrity.

Circuit integrity during a fire exposure has also been the concern of

transportation system designers [57]. In an effort to measure and rate electrical wires and cables for circuit integrity, recommendations [58] have been

made to the Department of Transportation that IEEE 383 be modified and used

to evaluate wires and cables for use in rapid transit systems. Circuit integrity is also of concern in central telephone stations due to the strategic

importance of maintaining communications links in the event of an emergency.

5. FIRE SCENARIOS

Appropriate test methods are best determined after an analysis of

incident data and the development of fire scenarios. A fire scenario is a sequence of critical events (e.g., component failure, ignition, growth, and

spread of a fire) that can result in a fire loss. Fire scenarios are generally but not exclusively developed after an analysis of incident data. While

currently available sources of incident data are incomplete for a detailed

description of a fire scenario, approximate models can be developed.

18
The primary source of the following information on fire incidents in

telephone exchanges was the National Fire Data Center of the U.S. Fire

Administration. Additional information was obtained from a review of fire

reports in various fire journals and from previously mentioned reviews of

fire incidents in telephone related buildings.

5.1 Incident Data

The U.S. Fire Administration maintains the National Fire Incident

Reporting System (NFIRS) . NFIRS collects its information from numerous fire

departments throughout the country. While not a statistical sampling, the

data system contains information on various details of a fire's origin and

growth. Data such as the point of origin, the type of materials and equipment involved, and the form of energy that caused the ignition are collected

as well as the type of property and the number of deaths and injuries. The

data reviewed in this report were obtained from NFIRS for calendar years 1976

through 1979.

A total of 189 telephone exchange fires were reported to NFIRS during

this time period. These include central offices, telephone exchanges,

communications cable sites with associated repeater and terminal facilities.

The incidents can be divided into five categories, figure 1. It was found

that nearly 41 percent of the fires occurred within a building. Trash fires

accounted for 17 percent of the total incidents, while 24 percent involved

materials located outside of a building.

The distribution of the incidents by space utilization of the area of

fire origin is shown in figure 2. The data show that 35 percent of the fires

occurred in electrical or electronic related facilities: 24 percent in electronic equipment rooms, and 12 percent in service facilities (i.e., transformer

vaults, repair shops)

.

Figure 3 describes the distribution of telephone exchange fires by the

type of equipment initially involved in the ignition. While 46 percent of

the incidents did not involve equipment, 23 percent could be directly

attributed to electronic or electrical equipment failures.

Figures 4 and 5 describe the extent of flame damage and of smoke damage,

respectively. There were nine reported cases of smoke damage beyond the

room of origin and six of flame damage. Generally, smoke damage extended

far beyond the zone of damage caused by fire. In 54 percent of the reported

cases, flame damage was limited to the object initially ignited. In 30 out

19
Number

of

incidents 1\

20

Figure 1-

NFIRS

classification

of

telephone

exchange

fires
Number of Incidents

0 10 20 30 40 50

Office space

Electronic facilities

Service facilities

Ducts & shafts

Exterior surfaces

Trash areas

Open areas

Other areas

Undetermined

i

1 r

Figure 2 - Classification of telephone fires as reported in NFIRS

by area of origin

21
Number

of

incidents

22

Figure 3-

Distribution

of

telephone

exchange

fires

as

reported

to

NF1RS

by

the

equipment

involved

in

the

ignition
Number

o-f

incidents o

OJ

_ o a c g. c

*o> 'o> "o> ’o>

‘L- 'L- 'L- L_ o o o O o O o O

H—o o

CD E

i_o CD L- O o

loo c o

a: Li_

00

23

Figure 4-

Description

of

the

extent

of

flame

damage

caused

by

telephone

exchange

fires

as

reported

in

NFIRS
Object of origin

Area of origin

Room of origin

Floor of origin

Structure of origin

Beyond structure

No structure fire

No smoke damage

Undetermined

Number of incidents

Figure 5 - Description of the extent of smoke damage caused by

telephone exchange fires as reported in NFIRS

24
of 68 cases involving structure fires where smoke damage was reported, the

damage extended beyond the initial item involved.

The 71 incidents occurring in electronic equipment rooms, service

facilities, and ducts are analyzed in figures 6 through 8. Figure 6 is a breakdown of the incidents by the type of equipment involved in the ignition.

Only eight reported incidents involved the electronic telecommunications

equipment. Electrical distribution equipment accounted for 53 percent of the

incidents. Lighting accounted for eight of these incidents. Two were caused

by failing transformers and one was caused by a misplaced tarpaulin igniting

from contact with a light bulb. The others appear to have been caused by

overheating light fixtures. Figure 7 describes the form of heat of ignition

and figure 8 shows the distribution of initial materials ignited. Thirty

incidents were caused by electrical shorts or overloaded circuits. Electrical

wire failures appear to be the major form of electrical failure representing

31 percent of all failures.

5.2 National Fire Protection Association

The Fire Record Department of the National Fire Protection Association

(NFPA) publishes reports on selected groups of typical fires reported to them.

These fire reports are descriptions of causes of fires and fire department

responses. Since January 1960, five telephone exchange fires are described.

While the data does not represent a statistical data base, it provides additional information that can be utilized in the development of a fire scenario.

One fire, occurring in Pusan, Korea [55], was caused by careless smoking

and will not be discussed. The four remaining fire reports describe fires

caused by equipment failures. Two fires [60,61] were caused by ignition of

power supply cables. One fire [62] was caused by an electrical fault in an

equipment control board and one [63] was the result of a short in a battery

providing power to operate the telephone exchange. Because of the presence

of a detection and suppression system, the battery failure caused only minor

damage to the building and switching equipment. The other fires had flame

propagation along cable ways that penetrated interior walls, floors, or ceilings. In one case, the ceiling was made of a combustible material. In other

cases barrier penetrations were not completely sealed.

The 1975 telephone exchange fire in New York City [64] is an example

of the dangers of an incomplete seal of a cableway penetration of a barrier.

In this case, the fire originated in a basement cable vault. The fire spread

25
Number

of

incidents

-4— •+- o> -4— T3 T3 a £Z a c. d CD CD

CD CD CD CD > E e i

JZ E E

i-i- 'lA

LT) O

O

Cl Ol o> Q. a. >

*Z> ’zj Li *3 ‘o c cr

Or cr

CD CD CD O'CD o *4— d

L_

O o> CD o CD

CD£

*t=O c

'o>

Odn

21 E

Cl

O

CL

L_

*4— O

L-Or

d

CD *o

O'

CD

C l‘Vn O

-4— d

CD

U *o

O 2 Z

26

Figure 6-

Type

o-f

equipment

failures

in

electronic

rooms,

service

facilities,

and

ducts

as

reported

by

NFIRS
Number

of

Incidents

ID

OJ

o

OJ

LO

o

- I

o>

g

o

E

co

o

jC

GO

/~*N U) T3

L_ 13 CD

c O o C

‘o

L- T3

c

CDC £

o <Do

o L_

CD T3

a

c "cdo

if) a> T3

r— o is

L. ID

(D

>O

27

Figure

7

-

NFIRS

data

on

the

form

of

energy

release

causing

ignition

in

electronic

and

electrical

facilities

of

telephone

exchanges
Number

of

incidents

CD LO -4— JLO L_ JZ t/> o

L_ CD LO O CD £

O

o

CD £

CL

o

O

£

E

b

a

L_

1—

1_

JD

a

ELO

LOO

O

O

!Z

o

L_

O

<D Id

•Ni LOL_

CDCLO

CL

'zj

CF

CD

L_

CD£

a5 _cO

LOC

o

L. 1—

b_

28

Figure

8

-

NFIRS

data

on

the

form

of

material

initially

ignited

in

electrical

and

electronic

facilities

of

telephone

exchanges
to the first and second floors of the building by way of telephone cableways

penetrating the floors.

A typical occurrence of an equipment failure took place at Colton, Oregon,

in August 1979. The fire was most probably caused by an electronic component

failure on one of the circuit boards. The flames extended across frames. The

resulting smoke and heat virtually destroyed the telephone exchange. The major

flame path was the rows of printed circuit boards and not the wires and cables.

A similar type of circuit failure is reported by Harrison and Lewoc [65] to

have occurred in a computer system at Goddard Space Flight Center. The fire

had originated on a printed circuit board in an electronic clock. A carbon

resistor on the board failed and, because of the close spacing of circuit

boards, the fire propagated to several other cards. The fire was readily

extinguished by personnel at the facility before excessive damage occurred.

5.3 Bell System Statistics

Eckler [66] analyzed 1500 fire reports occurring in Bell System buildings

from 1971 through 1977. While the data as presented by Eckler cannot be used

to determine the number of fires that occur in a given type of Bell System

space, general information is available relating to fire frequency in telephone

buildings.

In general, Eckler found that the frequency of fire occurrence increased

with the number of people occupying a building. However, as the staff was

decreased the cost of a fire increased apparently because of a delay in

detecting the fire. The data show that the median damage of a fire in an unoccupied building is approximately 10 times as large as the median damage

of a fire in an occupied building.

In analyzing the various methods people use to extinguish a fire, Eckler

shows that in 58 percent of the fires the fire department is not even notified

of a fire occurrence. These fires would, therefore, not be included in the

NFIRS data base.

6. CONCLUSIONS

A review of applicable test methods, relevant literature, and incident

data has been conducted. It has been shown that many test methods exist for

measuring the flammability characteristics of polymers used in electrical

applications. Test methods used to evaluate the fire performance of grouped

29
(bunched) wire and cables have been limited to comparative flame propagation

measurements except for IEEE 383, which can measure circuit integrity, and a modified ASTM E 84, which measures smoke density.

Large-scale tests of central office equipment have been limited to

evaluations of fire propagation along wires and cables. The interaction of

system components in a fire environment has not been reported.

A review of NFIRS fire incident data on telephone exchanges has shown

that:

• A third of the fire incidents reported occurred in electrical or

electronic related facilities;

• A major cause of fire incidents in electrical or electronic related

facilities was the power distribution system in a building;

• Smoke related damage extended over a larger volume of space than fire

related damage;

• Electrical wire failures appear to be the major form of electrical

failure

.

Based on Eckler's data, fire reports to NFIRS may underrepresent the extent

of telecommunication equipment failures. These fires may be successfully

extinguished by telephone personnel before extensive damage occurred in which

case local fire departments are not notified.

The major path of flame spread from the source of ignition appears to be

cableways.

A single test method to assess the suitability of materials intended for

central office equipment does not exist. There appears to be appropriate test

methods that with some modification could be used to measure critical fire

properties. These results could be combined to reduce the likelihood of ignition and flame spread. A vertical self-extinguishing test may be suitable for

the evaluation of printed circuit boards and back planes. Cables could be

evaluated using IEEE 383 and barrier penetrations could be tested according to

IEEE 634. Materials used in power branch circuit may also have to be evaluated

to ensure that fire safety requirements which may be promulgated by REA for

telecommunications equipment are not compromised. However, additional fullscale test verification would be necessary.

30
7. REFERENCES

[1] Bell System Purchase Products Specifications, New Jersey (1977).

[2] Standard Method for Measuring the Minimum Oxygen Concentration to

Support Candle-Like Combustion of Plastics (Oxygen Index), D 2863,

American Society for Testing and Materials, Philadelphia,

Pennsylvania (1977)

.

[3] Hilado, C. J. , Flammability Handbook for Plastics, Technomic Publishing

Company, Incorporated, Westport, Connecticut (1974)

.

[4] Standard Test Method for Behavior of Materials in a Vertical Tube

Furnace at 750 °C, E 136, American Society for Testing and Materials,

Philadelphia, Pennsylvania (1979) .

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

Materials, E 84, American Society for Testing and Materials,

Philadelphia, Pennsylvania (1979) .

[6] Standard for Tests for Flammability of Plastic Materials for Parts in

Devices and Appliances, UL 94, Underwriters Laboratories, Incorporated,

Northbrook, Illinois (1980) .

[7] National Material Advisory Board, Fire Safety Aspects of Polymeric

Materials, Vol. 2, Test Methods, Specifications, and Standards, Technomic

Publishing Company, Incorporated, Westport, Connecticut (1979) .

[8] Guide for Room Fire Experiment, American Society for Testing and

Materials, E 603, Philadelphia, Pennsylvania (1977).

[9] Maroni, W. F., Rigid Cellular Wall Insulations, Fire Journal, Vol. 67,

No. 6 (1972) .

[10] Williamson, R. B. and Baron, F. M. , A Corner Fire Test to Simulate

Residential Fires, Journal of Fire and Flammability, Vol. 4 (April 1973).

[11] Standard Method of Testing Rigid Sheet and Plate Materials Used for

Electrical Insulation, D 229, American Society for Testing and Materials,

Philadelphia, Pennsylvania (1977).

31
[12] Federal Test Method Standard 406 , Method 2023, Plastics: Methods of

Testing, U.S. General Services Administration, Washington, D.C. (1961).

[13] Polymeric Materials - Short Term Property Evaluations, UL 746A,

Underwriters Laboratories, Incorporated, Northbrook, Illinois (1978).

[14] Standard Test for Ignition Properties of Plastics, D 1929, American

Society for Testing and Materials, Philadelphia, Pennsylvania (1978) .

[15] Kline, L. M. , Burning, Arcing, Ignition, and Tracking of Plastics Used

in Electrical Appliances, Underwriters Laboratories Research Bulletin,

No. 55 (February 1964) .

!

[16] Federal Test Method Standard 406, Method 4011, Plastics: Methods of

Testing, U.S. General Services Administration, Washington, D.C. (1961).

[17] Standard Method of Test for Rate of Burning and/or Extent and Time of

Burning of Self-Supporting Plastics in a Horizontal Position, D 635,

American Society for Testing and Materials, Philadelphia, Pennsylvania

(1977) .

[18] Federal Test Method Standard 406, Method 2021, Plastics: Methods of

Testing, U.S. General Services Administration, Washington, D.C. (1961).

[19] Standard Method of Test for Rate of Burning and/or Extent and Time of

Burning of Flexible Plastics in a Vertical Position, D 568, American

Society for Testing and Materials, Philadelphia, Pennsylvania (1977)

.

[20] Federal Test Method Standard 406, Method 2022, Plastics: Methods of

Testing, U.S. General Services Administration, Washington, D.C. (1961) .

[21] Standard Method of Test for Rate of Burning and/or Extent and Time of

Burning of Cellular Plastics Using a Specimen Supported by a Horizontal

Screen, D 1692, American Society for Testing and Materials, Philadelphia,

Pennsylvania (1976)

.

[22] IEEE Standard for Type Test of Class IE Electrical Cables, Field Splices,

and Connections for Nuclear Power Generating Stations, IEEE 383, Institute

of Electrical and Electronics Engineers, Incorporated, New York (1974) .

32
[23] Standard Method for Testing, Thermosetting Insulated and Jacketed Wire

and Cable, D 470, American Society for Testing and Materials,

Philadelphia, Pennsylvania (1975)

.

[24] Tests for Flame Resistance of Cables, Title 30 Part 18.64, Code of

Federal Regulations, Washington, D.C. (1979).

[25] Standard for Rubber-Insulated Wires and Cables, UL 44, Underwriters

Laboratories, Incorporated, Northbrook, Illinois (1977).

[26] Testing Methods for Plastic Insulated Wires and Cables, JIS C 3005,

Japanese Standards Association, Japan (1977)

.

[27] Thermoplastic Insulated Wires, UL 83, Underwriters Laboratories,

Incorporated, Northbrook, Illinois (1979) .

[28] Specification for Flame-Retardant Characteristics of Electric Cables,

BSI 4066, British Standards Institution, London, England (1969).

[29] Specification for Braided Travelling Cables for Electric and Hydraulic

Lifts, BSI 6977, British Standards Institution, London, England (1969).

[30] Underwriters Laboratories, Incorporated, Report on Telephone Cable,

Northbrook, Illinois (1978)

.

[31] IEEE Standard Cable Penetration Fire Stop Qualification Test, IEEE 634,

Institute of Electrical and Electronic Engineers, Incorporated, New York

(1978)

.

[32] Standard Test Method for Measuring the Smoke Generated by Solid Materials,

NFPA 258, National Fire Codes, Vol. 10, National Fire Protection

Association, Boston, Massachusetts (1977) .

[33] Standard Test Method for Density of Smoke From the Burning or

Decomposition of Plastics, D 2843, American Society for Testing and

Materials, Philadelphia, Pennsylvania (1977).

[34] Miner, R. J. , Flammability Tests and Smoke Generation, "Flammability and

Safety," Society of Plastics Engineers, Incorporated, Regional Technical

Conference, Newark Section, Newark, New Jersey (1971)

.

33
[35] Wiktorek, R. J., Technical Evaluation of Various Test Procedures as Applied to Materials for Computer Applications, Flammability and Safety

Conference, Society of Plastics Engineers, Incorporated, Regional

Technical Conference, Newark Section, Newark, New Jersey (1971)

.

[36] Rogers, G. J. and Evans, D. D. , Characterization of Electrical Ignition

Sources Within Television Receivers, Nat. Bur. Stand. (U.S.), Tech. Note

1109 (1975) .

[37] Quigg, P. S. and Orals, D. L. , Communication Cable "Poke Thru" Floor

Fire Test, Building Standards, Vol. 46, No. 2 (1977).

[38] McGuire, J. H., Small-Scale Fire Tests of Walls Penetrated by Telephone

Cables, Fire Technology, Vol. 11, No. 2 (1975).

[39] McGuire, J. H. , Small-Scale Fire Tests of Six-Inch Wall Penetrated by

Telephone Cables, National Research Council of Canada, No. 116 (1976).

[40] Kita, K., Suyama , N., and Kawabara, S., New Sealing Method on Cable in

Telephone Office Building, CIB, Systems Approach to Fire Safety in

Buildings, Proc., Vol. 2, Session 4, Japan (August 1979).

[41] Kruczek, F. W. and Cascio, C. R. , The Cable Vault Goes Modern, Bell

Laboratories Record (January 1978) .

[42] Peverill, W. L., Engineering a Fireproof Test for Conductors, Insulation

Circuits, Vol. 16, No. 8 (1970).

[43] Woolerton, G. R. , The Use of Release Rate Tests to Evaluate Flammability

of Communications Cable, J. Fire and Flammability, Vol. 9 (July 1978).

[44] Beyreis, J. R. , Skjordahl, J. W. , Kaufman, S., and Yocum, M. M. , A Test

Method for Measuring and Classifying the Flame Spread and Smoke

Generating Characteristics of Communications Cable, Proceedings of the

25th International Wire and Cable Symposium, Cherry Hill, New Jersey

(November 16-18, 1976).

[45] Kievan, J. , MacDougall, E. , and Hall, A., Fire Damage Data Analysis as Related to Current Testing Practices for Nuclear Power Applications,

Brookhaven National Laboratory, BNL-NUREG 23364, Informal Report (October

1977) .

34
[46] Clarke, R. K., An Analytical Model for Cable Tray Fires, Sandia

Laboratories, SAND 75-0288 (September 1975)

.

[47] Klamerus, L. J., Cable Tray Fire Tests, IEEE Power Engineering Society,

Winter Meeting, New York (February 4-9, 1979).

[48] Lupton, E. C., Tahlmore, C. D. , and Obsasnik, J. , Some Differences Noted

in the Flammability of Wire Constructions Between Testing at Room

Temperature and at Elevated Conductor Temperature, Proceedings of the

24th International Wire and Cable Symposium (AD-A017787) (November 18-20,

1975)

.

[49] Augustyn, E. J. and White, E. L. , New High Temperature, Flame Resistant,

Thermoplastic PVC Wire Insulations, Proceedings of the 21st International

Wire and Cable Symposium, AD752908 (December 1972) .

[50] Bilow, N. and Lehn, W. L., High Temperature Electrical Wire Insulation

Development, Proceedings of the 21st International Wire and Cable

Symposium, AD752908 (December 1972) .

[51] Hildreth, N. and Brooks, J., EXAR: A Flame-Resistant, High Temperature,

Cross-Linked Wire Insulation System, Proceedings of the 21st International

Wire and Cable Symposium, AD752908 (December 1972)

.

[52] Reed, J. C. and Perkins, J. R. , Tefzel ETFE Fluoropolymer : Temperature

Rating and Functional Characterization, Proceedings of the 21st

International Wire and Cable Symposium, AD752908 (December 1972) .

[53] Maezawa, T., Murayama, V., and Yoshizawa, A., Heat Resistant Cables for

Fire-Prevention Systems, Proceedings of the 24th International Wire and

Cable Symposium (AD-A017787) (November 1975)

.

[54] Matsubara, H., Matsunaga, C., Inoue, A., and Yasuda, N., The

Development of New Fireproof Wire and Cable, Proceedings of the 24th

International Wire and Cable Symposium (AD-A017787) (November 1975) .

[55] Kaufman, S. and Laudreth, C. A., Development of Improved Flame-Retardant

Interior Wiring Cables, Proceedings of the 24th International Wire and

Cable Symposium (AD-A017787) (November 1975)

.

35
[56] Electrical Research Association, Cables, and Fire, A Review of Some

Recent Literature With Commentary, The Electrical Research Association

(December 1972)

.

[57] Meyer, L. E., Taylor, A. M. , and York, J. A., Electrical Insulation Fire

Characteristics - Volume I: Flammability Tests, U.S. Department of

Transportation, UMTA-MA-06-0025-79-1 , I (December 1978).

[58] Taylor, A. M. , Wire and Cable Insulation for Rapid Transit Systems, Am.

Chem. Soc., National Symposium on Fire Safety of Polymeric Materials,

Washington, D.C. (June 6-8, 1977).

[59] Telephone Exchange Fire, Pusan, Korea, March 18, 1968, Fire Journal,

Vol. 62, No. 6, p. 60 (1968).

[60] Telephone Exchange Fire, Mebane, North Carolina, August 23, 1976, Fire

Journal, Vol. 71, No. 1, p. 42 (1977)

.

[61] Telephone Exchange Fire, Marshfield, Massachusetts, October 21, 1979,

Fire Journal, Vol. 74, No. 2, p. 21 (1980).

[62] Telephone Exchange Fire, Garland, Washington, December 3, 1968, Fire

Journal, Vol. 63, No. 3, p. 53 (1969).

[63] Telephone Exchange Fire, Granda Hills, California, August 3, 1975, Fire

Journal, Vol. 70, No. 5, p. 45 (1976).

[64] Lathrop, J. K. , Telephone Exchange Fire, New York, New York, Fire

Journal, Vol. 69. No. 4 (1975).

[65] Harrison, G. A. and Lewoc , D. G., Computer Fire and Resultant Circuit

Card Fire Tests, Fire Journal, Vol. 63, No. 2 (1969).

[66] Eckler, A. R. , A Statistical Analysis of Bell System Building Fires,

1971-1977, The Bell System Technical Journal, Vol. 57, No. 8 (1978).

36
NBS-114A (REV. 2-8C) U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

PUBLICATION OR

REPORT NO.

NBSIR 81-2261

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

May 1981

4. TITLE AND SUBTITLE

REVIEW OF LITERATURE, APPLICABLE TEST METHODS, AND INCIDENT DATA FOR THE EVALUATION

OF THE FIRE PERFORMANCE OF CENTRAL TELEPHONE OFFICE EQUIPMENT

5. AUTHOR(S)

Emil Braun

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

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

Final Report

9.

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

Rural Electrification Administration

U.S. Department of Agriculture

Washington, D.C. 20250

10.

SUPPLEMENTARY NOTES

_2) 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)

At the request of the Rural Electrification Administration, a program was initiated

to evaluate the adequacy of current flammability specifications for electrical

equipment used in telephone company central offices. The high reliance on telephone

services for emergency communications necessitates that measures be considered to

minimize the likelihood of fire related interruptions of service. This report provides a review of current test methods and specifications for central office equipment; a review of available fire test methods in various categories; a brief literature review of relevant fire research and fire testing of wiring, cables, and

assemblies; and a review of fire incident data.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Central office equipment; electronic equipment; fire test methods; incident data;

telecommunications; telephone exchanges.

13. AVAILABILITY

[)Q£ Unl imited

| | For Official Distribution. Do Not Release to NTIS

[ H Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

40

15. Price

$6.50

USCOMM'DC 6043-P80