A11101 31flm3 PUBLICATION®

NBS

NBSIR 83-2677

Analysis of Electrical Fire

Investigations in Ten Cities

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Washington, DC 20234

March 1983

Interim Report

Sponsored by:

Consumer Product Safety Commission

5401 Westbard Avenue

Bethesda, MD 20016

NATIONAL EU’.'.. au Of STAJ?DAiiL>8 UBRABT

NBSIR 83-2677

/ 3

'» .O' ANALYSIS OF ELECTRICAL FIRE

INVESTIGATIONS IN TEN CITIES

Alan Gomberg and John R. Hall, Jr.

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Washington, DC 20234

March 1983

Interim Report

Sponsored by:

Consumer Product Safety Commission

5401 Westbard Avenue

Bethesda, MD 20016

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 vl

Abstract 1

1. INTRODUCTION 1

2. DESCRIPTION OF WORK 3

3. OVERVIEW OF CHARACTERISTICS OF FIRE INCIDENTS 4

3.1 Fixed Property Use 5

3.2 Area of Origin 5

3.3 Equipment Involved In Ignition and Form of Heat of

Ignition 6

3.4 Detector Performance 8

3.5 Extent of Flame Damage 8

3.6 Time of Fire 8

3.7 Occupant Condition 9

3.8 Comparison with National Fire Data 9

4. OVERVIEW OF ELECTRICAL SYSTEMS 12

4.1 ElectrLcal Component Involved in Ignition....... 12

4.2 Alterations to Building Electrical System 12

4.3 Prior Problems with System 14

4.4 Fire Occurrence at Splice or Connection 15

4.5 Recent Alterations to Component Involved in Ignition 16

4.6 Panel Board Location, Shelter from the Elements and

Ambient Conditions 17

4.7 Wiring Method, Material and Size 17

4.8 Specific Component Failure Causing the Fire 18

5. CHARACTERISTICS AND PERFORMANCE OF OVERCURRENT PROTECTION

DEVICES 22

5.1 Performance of the Overcurrent Protection Devices 22

5.2 Overcurrent Protection Devices by Component

Involved in Ignition 28

5.3 Overcurrent Protection Device Rating by Minimum Wire

Size of Branch Circuit 28

6. THE ROLE OF BUILDING AGE 33

6.1 Edison Base Fuses and Circuit Breakers by Age

of Building 34

6.2 System Alterations by Age of Building 36

6.3 Components Involved in Ignition by Age of Building 37

6.4 Wiring Method by Age of Building 37

6.5 Separate Grounding Conductor 40

-iii-
7. THERMAL INSULATION 40

8. SERVICE COMPONENT FIRES 41

9. BRANCH CIRCUIT WIRING FIRES 41

10. CORD AND PLUG FIRES 42

11. SWITCHES, OUTLETS AND RECEPTACLES 44

11.1 Age of Building and Overcurrent Protection Devices 45

11.2 Problems with Splices and Connections 45

11.3 Grounding 46

11.4 Other Factors 46

12. LIGHT FIXTURE, LAMPHOLDER AND PORTABLE LAMP FIRES 47

13. CONCLUSIONS 47

14. ACKNOWLEDGEMENTS 48

15. REFERENCES 49

-iv-
LIST OF FICURES

Page

Figure 1. Performance of Overcurrent Protection Devices, by

Type of Device and with Reference to the Presence or Absence of Tampering and Unusual Panel Conditions 27

Figure 2. Tampering by Year Built and Type of Overcurrent

Protection Device 35

-v-
LIST OF TABLES

Page

Table 1. Electrical Fire Cases by City 2

Table 2. Area of Origin 6

Table 3. Equipment Involved in Ignition vs. Form of -Heat

of Ignition 7

Table 4. Time of Fire and Component Involved in Ignition..... 9

Table 5. Fixed Property Use Comparison 10

Table 6. Equipment Involved in Ignition Comparison 10

Table 7. Extent of Flame Damage Comparison 11

Table 8. Electrical Component Involved in Ignition 13

Table 9. Summary of Prior Problems.... 15

Table 10. Percent of Fire Involving Splices, Connections or Termination for Each Component Involved in Ignition 16

Table 11. Percent of Fires Involving Recent Alterations to

Component Involved in Ignition 16

Table 12. Percentage of System Alterations for Each Wiring Method.. 18

Table 13. Wiring Method and Component Involved in Ignition 19

Table 14. Branch Circuit Conductor Wire Sizes (A.W.G.) 20

Table 15. Failure Mode by Component...... 21

Table 16. Type of Overcurrent Protection Device 22

Table 17. Incidence of Unusual Conditions Found at Panel 24

Table 18. Miscellaneous Characteristics for Fires Where Circuit

Breakers Were Present 29

Table 19. Overcurrent Protection Devices for Each Component

Involved in Ignition.............. 30

Table 20. Wire Size and Overcurrent Protection Device Rating

by Type of Device 31

Table 21. Overcurrent Protection Device Performance by Type

and Rating of Device and Wire Size - Percentage of

Cases Where Device Interrupted Current 32

-vi-
Table 22. Ratio of Electrical Fires to Housing Units by Age of

Housing.... 33

Table 23. Ratios of Fire Rates for Post-1940 and Pre-1940

Housing by Type of Component Involved in Ignition 38

Table 24. Wiring Method by Building Age and Type of Overcurrent

Protection Device 39

Table 25. Details of Improper Location of Extension Cords 44

-vii-
r

*
Analysis of Electrical Fire Investigations in Ten Cities

Alan Gomberg and John R. Hall, Jr.

National Bureau of Standards

Washington, D.C. 20234

This interim report describes the progress and conclusions to

date on an analysis of electrical fire cases by the Center for

Fire Research, National Bureau of Standards for the Consumer

Product Safety Commission. The report describes the 110 detailed

electrical fire investigation reports from 10 participating

cities, and discusses preliminary findings resulting from analysis

of the computerized data from those reports. These preliminary

findings include factors which may cause overcurrent devices to

fail to operate, the role of extension cords misused as permanent

extensions of building wiring, and the problems of loose connections between receptacles and wiring. They are being used to

guide a follow-on effort, to be reported on at a later date, to

obtain, encode and analyze additional data from the original 110 cases. This second effort will better define and describe the most

significant failure modes of electrical components and the

sequences of events that lead to electrical fire ignition.

1 . INTRODUCTION

This report describes characteristics and patterns of 110 electrical

fires, with special attention to those patterns that suggest hypotheses on fire prevention programs and product design. Data for this initial analysis

were collected in 10 cities, as shown in table 1. The Consumer Product Safety

Commission (CPSC) sponsored the research and suggested an initial set of

issues to be examined. The U.S. Fire Administration (USFA) and its consultant, John Ricketts, collected the data and implemented a training program on

the identification of electrical fires for fire department personnel in these

10 cities. The resulting detailed electrical fire investigation cases were provided to the Center for Fire Research (CFR) for review, coding and

analysis. All electrical fires investigated occurred during the period of

March 1980 through December 1981, but the actual period of data collection

varied from city to city.

- 1 -
Table 1. Electrical Fire Cases by City

City No. of Cases

Akron, Ohio

Grand Rapids, Michigan

Long Beach, California

Oakland, California

Portland, Oregon

Sacramento, California

San Diego, California

San Francisco, California

San Jose, California

Toledo, Ohio

22

4

9

1 11

15

7 17

11

13

Total 110

NOTE: An additional four cases were provided but could

not be included in the analysis because of incomplete documentation and inadequate detail.

The intent of this initial analysis is to formulate questions and hypotheses, where possible, regarding the nature of significant electrical

failures, the electrical distribution components involved in fire origination,

and the identification of the mechanisms resulting in component failure. The

results will be used to direct efforts at further isolating and understanding

electrical fire problems and possible remedial actions. The small number of cases available, the wide variety of electrical failure modes and limitation

in the initial coding, permit only this kind of exploratory analysis. The

questions raised and the hypotheses brought forth by this interim report will

direct the coding of additional data in the existing and additional cases,

leading to identification of the key electrical failure modes producing fires

and finally to research on possible corrective actions. As a first step,

additional coding and analysis of the existing cases are being performed as a followup to this interim report and will be documented in a final project

report.
2. DESCRIPTION OF WORK

The detailed investigations used a fire incident report and a two part

questionnaire with one part containing general information on the electrical

system and the second part containing detailed information on the electrical

component involved. The questionnaire is not reproduced here due to its

length. Copies may be obtained from Linda Smith, Consumer Product Safety

Commission, Division of Hazard Analysis/Epidemiology, 5401 Westbard Avenue,

Bethesda, MD 20016. In addition, most of the cases included photographs and

detailed electricians reports, including schematics of the buildings'

electrical systems and other relevant details. Approximately one-third of the cases also contained samples of the damaged components.

The detailed investigations were made based on preliminary field determination of electrical origin by the responding fire company and subsequent

confirmation by fire investigators. After the completion of each investigation the completed questionnaires, photographs and samples were sent to the

USFA consultant Mr. Ricketts, who reviewed them and contacted the investigators as necessary to clear up questions and problems. The completed cases were then passed on to CFR, through CPSC, for coding and analysis.

The coding was screened by personnel skilled in electrical engineering,

according to the following procedure: The principal investigator coded each

case, using the investigator reports, photographs and physical samples where

available. The points on which he felt further input was needed were identified. An NBS electrical engineer then provided the needed input. (This

procedure of input only as deemed necessary was first tested on a random

sample of ten cases, with the electrical engineer reviewing all coding, not

just Items where input was requested.) Input from the electrical engineer

proved necessary in approximately one-third of the cases.

The computer coding was set up according to a three-part format which

also roughly corresponds to the organization of the material in this report.

First, the incident report data were coded using the data elements and

- 3-
conventions employed in the National Fire Incident Report System (NFIRS)

[ 1

1

. (Most cities included incident reports prepared for NFIRS or using a similar format.) Analyses of this information are contained in section 3 of

this report. Second were the general descriptions of electrical systems,

based on Part 1 of the questionnaire. Analyses of this information are contained in section 4 of this report. Third were the detailed descriptions

of the particular electrical components involved in the fires. Analyses of

patterns for each major type of component are contained in sections 8 through

12 of this report. Sections 5 through 7 of this report deal with issues that

need to be examined both relative to all components and relative to each majo

type of component involved in ignition. These issues are characteristics and

performance of overcurrent protection devices, the role of building age, and

the role of thermal insulation.

3. OVERVIEW OF CHARACTERISTICS OF FIRE INCIDENTS

This section presents some major patterns based on tabulations of key

Incident Report parameters. Subsequent sections present an overview of some electrical report information and more detailed examinations of failure modes

and key characteristics and present significant findings and hypotheses.

Following are brief definitions of the Incident Report parameters

examined.

Fixed Property Use - The type of property that the fire occurred in.

Area of Origin - The room or space where the fire originated.

Detector Performance - The presence or absence of smoke detector(s)

and their functioning.

Extent of Flame Damage - The final extent of flame and heat damage

due to the fire.

^Numbers in brackets refer to the literature references listed at the end of

this paper.
Time of Fire - Usually the time (often shortly after ignition) that

the fire was reported to the fire department.

Occupant Condition - A description of the occupancy of the structure

just prior to the fire (all occupants asleep, at least one occupant

awake, etc.).

Equipment Involved in Ignition - The equipment which provided the

heat which started the fire (fixed wiring, cord, plug, etc.).

Form of Heat of Ignition - The form of the heat energy igniting the

fire (water caused arc, arc from mechanical damage, etc.).

3.1 Fixed Property Use

Most cases (84%) were single family dwellings, with the remainder either

duplexes (9%) or small apartments (up to six units) (7%). By design, no fires

in large apartment complexes (containing over six units) were investigated.

This distribution compares well with national Census estimates of occupied

housing units for 1978, which indicate that 84 percent of the occupied housing

that contains four or fewer individual units are single unit and 16 percent

are structures containing two to four dwelling units [2]. In other words,

there was no indication that some types of housing, within this limited set, were more prone to electrical fires than others.

3.2 Area of Origin

The area of fire origin was coded in NFIRS format. The results are

tabulated in table 2. Concealed spaces - within ceiling, walls and attics - were the leading Areas of Origin, totaling 43 percent of all fires. Only

34 percent of the fires started in normally occupied living areas (living

rooms, bedrooms, etc.).

- 5-
Table 2. Area of Origin

Area Percent of Total

Basement

Kitchen

Carage

Bedroom

Living Room

DLning Room

Closet

17.3%

7.3%

7.3%

7.3%

4.5%

1 . 8 %

0.9%

Concealed Space - Wall

Concealed Space - Attic

Exterior Wall Surface

Concealed Space - Ceiling

Crawl Space

Other

21 . 8 %

15.5%

7.3%

5.5%

0.9%

2 . 6 %

Total 100.0

As would be expected, the majority (72%) of branch circuit wiring fires

occurred in concealed spaces. In addition, 60% of the fires involving receptacles were in concealed spaces. Together these two components accounted for

74% of the concealed space fires. For fires in living areas, the dominance of

bedroom fires is accounted for by cords and plugs, which were involved in 68%

of the bedroom fires. Almost half (46%) of the cord, plug fires in the data

base occurred in bedrooms.

3.3 Equipment Involved in Ignition and Form of Heat of Ignition

These data elements are compared in table 3.

Several combinations of Equipment Involved and Form of Heat stand out in

table 3. Loose and faulty connections (35%) are the leading known Form of

Heat for fixed wiring, although mechanical damage (24%), defective or worn

insulation (18%) and overloaded equipment (18%) are well represented. Loose

and faulty connections (64%) also dominate the Equipment Involved category of

switch, receptacle, outlet. The cord and plug Equipment Involved category is

dominated by mechanical damage (50%) and overloaded equipment (33%).

- 6 -
Table

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wiring.
The other equipment categories have no dominant Form of Heat. Further

analysis of some of these patterns, using the more detailed data in the Part 1 and Part 2 reports, can be found in the subsequent sections, which address the

primary electrical components involved in ignition. The breakdown of this

more detailed data is not directly comparable with the NFIRS type coding for

equipment involved, however, due to differences in the coding formats.

3.4

Detector Performance

The presence or absence of detectors was established in 95 of the 110 cases. They were present in 14 percent of the 95 cases. This compares with

the 1980 national estimates, which shows detectors present in 20 percent of

all fires in one- and two-family dwellings and small apartments. The fact

that detectors are known to have been present in about one-half of all households in the country in 1980 [3] and were present in only 14 percent of the

fires in this data base indicates that homes with smoke detectors may be less

likely to have a reported electrical fire than homes without.

3.5

Extent of Flame Damage

The final extent of flame damage was known in all but two cases, and

flame damage was confined to the object of origin in 41 percent of the cases. Flames spread beyond the room of origin in only 8 percent of the cases.

3.6

Time of Fire

As table 4 indicates, the time of fire is distributed differently for

each component involved in ignition. Some patterns, such as light fixture

fires occurring predominantly in the 6:00 p.m. to midnight timeframe, are expected, but others, including the frequent occurrence of receptacle/outlet

fires in the morning hours and of branch circuit fires in the afternoon and

evening hours, are not so readily explainable. Initial attempts at examining

these distributions have not produced promising hypotheses. Further attempts

will be made to understand the factors behind these time distributions, such

as examining detailed causal patterns and obtaining typical load profiles of

residential power consumption. Comparisons with national estimates on time

distribution of electrical fires will also be made.

-8 -
Table 4. Time of Fire and Component Involved In Ignition

Midnight

- 6 a.m.

6 a.m. - Noon

Noon -

6 p .m

.

6 p.m. - Midnight

All

Hours

Service Components 20% 20% 27% 33% 14%

Branch Circuit Wiring 13% 16% 34% 38% 29%

Receptacles and Outlets 21% 36% 25% 18% 26%

Cords and Plugs 15% 15% 35% 35% 18%

Light Fixtures 14% 7% 29% 50% 13%

All Components 17% 20% 30% 33% 100%

3.7 Occupant Condition

Occupant Condition at the time of ignition, while not an NFIRS data

element, was included on the incident report, and was known in 85 of the 110 cases. In 69 percent of these cases at least one occupant of the dwelling was awake and alert at the time of ignition. All occupants were asleep or impaired in 14 percent of the cases, and no one was home in 17 percent of the cases.

3.8 Comparison with National Fire Data

National fire cause distributions can be estimated from data in the

National Fire Incident Reporting System (NFIRS), which contains computerized

fire incident reports on fire causes and fire losses from over 30 states. An

attempt was made to compare the distributions of several key elements with

national estimates calculated from the NFIRS. Good correlation between

natLonal estimates and the study data was noted for the elements Fixed

Property Use, Detector Presence and Equipment Involved in Ignition.

Substantial differences were noted for the element Extent of Flame Damage.

Finally, substantial differences found in two other key elements, Area of

Origin and Form of Material Ignited, are believed to be due to differences in

the application of the coding methodology. A discussion of each element

follows.

- 9-
Fixed Property Use in the study data base was divided into three

categories, single family dwellings (excluding mobile homes), duplexes and

small apartments (up to six units). The distribution of Fixed Property Use in

the study data base was compared with the estimated national distribution of

similar categories from NFIRS, and the results are illustrated in table 5. No

major differences between the two data bases are noted.

Table 5. Fixed Property Use Comparison

Fixed Property Use CPSC National Estimate

Single Family 83.5% 88.5%

Duplex 9.2% 5.0%

Apartment (up to six units) 7.3% 6.5%

Equipment Involved in Ignition, as indicated in table 6 (with unknowns

excluded) did not show large variances between the study data base and

national estimates. The nine Equipment Involved categories were generally in

the same proportions for both, and their rank order is the same. This indicates that the electrical components studied in detail here are represented in

a similar manner to their relative national distribution as estimated from

NFIRS.

Table 6. Equipment Involved in Ignition Comparison

Equipment CPSC Rank

National

Estimate Rank

Fixed Wiring 37.3% 1 39.3% 1 Cord, Plug 25.4% 2 18.6% 2 Switch, Receptacle, Outlet 18.2% 3 11.8% 3

Lighting Fixture, Lampholder 9.1% 4 11.5% 4

Lamp, Light Bulb 3.6% 5 6.9% 5

Overcurrent Protection Device 2.8% 6 5.5% 6

Other 1.8% 7 3.5% 7 Meter 0.9% 8 1.5% 8

Total 100.0% 100.0%

As noted in section 3.4, Detector Presence was compared for the study

data and national estimates and was found to be similar.

- 10-
A substantial difference between national estimates and study data was noted when Extent of Flame Damage was compared, as indicated by table 7.

Table 7. Extent of Flame Damage Comparison

National

Extent of Flame Damage CPSC Rank Estimates Rank

Object 41.1% 1 31.5% 1 Part Room 35.5% 2 19.8% 4

Room 15.0% 3 19.9% 3

Floor 6.5% 4 5.9% 5

Building 0.9% 5 20.9% 2 Outside Building 0.9% 5 2.1% 6

It is obvious from both the percentage distributions and the rankings of

Extent of Flame Damage that the study data base tends toward the smaller fire

much more than those in the NFIRS. This may be an artifact of the case selection process. In this study, emphasis was placed on detailed investigation,

and larger fires may not have been considered as the extensive destruction of

the site often precludes detailed investigation. On the other hand, all fires

are supposed to be reported to NFIRS. This suggests that property loss

figures from this study cannot be directly compared with national estimates.

The relatively high proportion (69 percent) of cases where occupants were

awake and alert at ignition may also account in part for the relatively low

level of fire damage in the subject cases.

Significant discrepancies between the study data and national estimates

were found when Area of Origin and Form of Material Ignited were compared.

They are believed to be artifacts of the coding procedure, however, resulting

from a combination of more detailed and thorough investigation and analysis of

the study cases than is usual for the fire incidents in NFIRS, and the

resulting ability to use a more exacting application of the coding procedures

in the study cases.

- 11 -
4. OVERVIEW OF ELECTRICAL SYSTEMS

This section contains overview information from the detailed electrical

fire investigation reports. Subsequent sections present more detailed information on selected parameters. These parameters are discussed separately from

the incident report elements because, in some cases, similar parameters coded

separately in the two reports are not directly comparable.

4.1 Electrical Component Involved in Ignition

Table 8 shows the Components Involved in Ignition for the 110 cases.

The first four categories (15 incidents) refer to utility system components tied to the particular building; they are usually located between the

building's final overcurrent protection device and those utility system components not tied to a particular building. The four categories are referred to

collectively as service components. In general, analysis of service components was done on the group as a whole, as the limited number of fires

involving each individual component precluded more detailed analysis even at an exploratory level.

Of the remaining components, branch circuits provided the most cases,

with nonmetallic sheathed cable and knob and tube dominating. Cords and

plugs, in particular extension cords, contributed significantly to the total.

Receptacles and outlets dominated their category, as did incandescent lighting. Some light fixture incidents were not electrical system breakdowns but were due to combustibles placed too close to otherwise normally operating

light Lng equipment; this will be discussed further in subsequent sections.

4.2 Alterations to Building Electrical System

Overall, 72 percent of the electrical systems in this study had been

altered to some extent prior to the fire. These alterations ranged from minor

(such as extension of a circuit) to major replacement or modification of

system components. Some were system upgrades, such as replacement of deteriorated wiring or modernizing and upgrading system capacity, while others, such

- 12-
Table 8. Electrical Component Involved in Ignition

Component No. of Incidents

Utility Supply Conductors _3

Overhead Utility Wires 3

Service Entrance Wiring _7

Service Entrance Cable 4

Service Entrance Conductors in Conduit 2

Meter, Meter Box, Meter Mounting 1

Service Equipment _4

Service Entrance Conductor Termination 1 Grounding Electrode Conductor 1 Service Disconnect 2

Distribution Panel _1_ Feeder Wiring 1

Branch Circuit Wiring 32

Armored Cable (BX) 5

Nonmetallic Sheathed Cable (Romex) 16

Knob and Tube 9

Multiple Types 2

Cords and Plugs 28

Extension Cord 15

Cord on Appliance 8

Cord on Portable Lamp 2 Christmas Tree Wiring 1 Plug Adapter 1 Cord-Heating Device 1

Switch, Receptacle, Outlet 20

Wall Type Switch 1 Receptacle, Outlet 18

Baseboard Heater Thermostat 1

Lighting Fixture, Lampholder 14

Fluorescent Lighting Fixture 1 Incandescent Lighting Fixture 7 Lampholder 3

Portable Lamp 3

Low Voltage Transformer

Low Voltage Transformer 1

Total 110

- 13-
as addLtion of bootleg circuits, splicing improper wiring into circuits, or bypassing overcurrent protection devices had the effect of downgrading the

system. More than half of the alterations had been made less than 5 years

before the fire.

The relationship of system alterations to various fire attributes Is

discussed in subsequent sections. There is no information in the currently

coded data, however, on the relevance of the alterations to the fire,

including specific nature and extent of the alterations performed. In particular the characterization of alterations as improvements or downgrades was

not coded for this initial analysis, although the information needed to make

those determinations was often collected. The addition of selected factors

relating to system alterations will be done in the followup to this report,

and the analyses will be documented in the project Final report.

4.3 Prior Problems with System

Information on any problems involving the electrical system prior to the

fire incident was recorded by the investigator through discussion with the

building occupant. Some problems were noted immediately prior to (or simultaneous with) the ignition, while other problems appear to have occurred over extended periods of time.

Information on the presence or absence of prior problems was obtained in

97 percent of the cases; of these the existence of one or more prior problems

was noted 44 percent of the time. Of the 47 cases with at least one prior

problem, 70 percent had one, 21 percent had two, 4 percent had three, 2 percent had four, and 2 percent had five or more prior problems. Overall, in

these 47 cases, a total of 67 specific problems were noted. Of the 18 differ1

ent types of problems noted, the most common manifestation of a problem was fuses blowing, followed closely by lights flickering.

The noted prior problems undoubtedly represent a lower bound of those

actually occurring, because some respondents may not have remembered or may

have omitted reference to prior problems. One indication that this may be

occurring is that, although fuses blowing was noted as a problem in only 18

cases, overfusing was noted in 34 cases.

- 14 -
Table 9 lists the categories of prior problems noted and their frequen

cies. Some occurred singly, and others, as indicated earlier, occurred in

combination.

Table 9. Summary of Prior Problems

(Prior Problems Noted in 44% of the Cases)

Problem Description Number of Times Cited

Fuses Blowing 18

Lights Flickering 15

Lights Dimming 8

Breakers Tripping 6

Appliances Operating Slowly 3

Bulbs Burning Out Prematurely 3

Radio Sounding Scratchy 2

Sparking, Arcing at Outlet 2

Lights Going Out 1 Previous Similar Fire 1 Unable to Turn Off Light 1 Smoke & Heat at Receptacle 1 Hot Cord 1 High Electric Bills 1 Lights Failing to Turn On 1 Range Burners Burning Out 1 Lights Turning On and Off Due to Vibration 1 Unspecified 1 Total 67

Initial efforts were made to correlate the most frequent prior problems

with the component involved in ignition, but no significant results were

obtained. Further efforts will be made in the followup, with special attention to grouping of similar prior problems into a smaller number of categories. This is more likely to reveal any significant correlation between

prior problems and electrical failure mode if one exists. An attempt will

also be made to compare prior problems with system age if that information is

obtained in the followup.

4.4 Fire Occurrence at Splice or Connection

The fire occurred at a wire termination, connection or splice in 38

percent of the cases. Of these, 95 percent were copper wiring, and the

remaining 5 percent were aluminum wiring. As indicated in table 10, receptacles and outlets were the components where fires most often occurred at a

- 15-
wire termination, connection or splice. Also, 42 percent of the branch

clrcult/spllce fires involved knob and tube wiring.

Table 10. Percent of Fires Involving Splices, Connections or Termination for Each Component Involved in Ignition

Component

Service Components

Branch Circuit Wiring

Cords and Plugs

Receptacles and Outlets

Light Fixtures

Transformer

Percent of Fires at Splice,

Connection, Termination

20%

40%

33%

55%

43%

0%

4.5 Recent Alterations to Component Involved In Ignition

In 20 percent of the cases, the component involved in ignition had been

recently altered, rewired, replaced or installed. (Note that this is not the same question as the alterations to system code discussed in section 4.2.

This code refers to alterations to the involved component, not to the overall

electrical system.) As table 11 shows, light fixtures were most frequently

found to have been recently altered, rewired, replaced or installed. This

information, combined with table 10 information that 43 percent of light

fixture fires occur at splices, indicates further evaluation of characteristics of recently made splices in light fixtures Ls needed. This will be

further addressed in a subsequent section.

Table 11. Percent of Fires Involving Recent Alterations to

Component Involved in Ignition

Component Percent Recently Altered, Etc.

Service Components 20%

Branch Circuit Wiring 16%

Cords and Plugs 22%

Receptacles and Outlets 10%

Light Fixtures 36%

i - 16 -
Conversely, while table 10 shows that splices and connections are a major

problem wLth receptacles and outlets, only 10 percent of the receptacle fires

showed recent alterations. The indication here is that while splices and

connections (actually these are most likely wire terminations) are a problem

for receptacles and outlets, the problem may not be related to recent installation or alteration. This question will be further addressed in the followup.

4.6 Panel Board Location, Shelter from the Elements, and Ambient Conditions

The final overcurrent protection device for the branch circuit was in a panel board located on the exterior of the building in 32 percent of the 95

fires that did not involve service components. A panel board installed in the

interior of the building was provided in the other 68 percent of these cases. Fused systems were located inside the building slightly more often than circuit breakers. Shelter from the elements was provided in 87 percent of the 30 cases with a panel board located on the exterior of the building.. No shelter

was provided in 10 percent of the cases and in 3 percent the presence or absence of panel board shelter was unknown.

In 95 percent of the 95 fires not involving service components, the

ambient conditions at the panel board were judged to be normal for the area

and time of year. Two cases (2 percent) were judged unusually hot, and three

cases (3 percent) were judged unusually damp.

4.7 Wiring Method, Material and Size

Of the 95 fires not involving service components, nonmetallic-sheathed

cable (type NM,"Romex") was used in 49 percent of the cases, knob and tube in

25 percent, electrical metallic tubing (EMT) and armored cable (type AC "BX")

each in 6 percent, and the remaining types of wiring, including multiple types

in a single circuit, in one or two cases each. Copper wiring was used in 95

percent of the cases, aluminum wiring in 4 percent and steel wiring in 1 percent. Nonmetallic-sheathed cable was used in the steel wiring case and 3

of the 4 aluminum wiring cases; the fourth aluminum wiring case used service

entrance cable (type SE).

- 17 -
Table 12 shows how the presence or absence of system alterations varies

by type of wiring method.

Table 12. Percentage of System Alterations for Each Wiring Method

Wiring Method

Nonmetallic sheathed cable

Knob and Tube

Electric Metallic Tubing

Armored Cable

Other*

Total

Number of Cases Percent

46 49%

24 25%

6 6%

6 6%

13 14%

95 100%

Percent with Alterations

67%

71%

50%

100 %

92%

73%

The category "other" includes individual conductors in both rigid and

flexible metal conduit, and those cases where more than one type of wiring was used within the involved circuit.

Table 13 shows the distribution of wiring method by component involved in

ignition.

Table 14 shows the relative frequency of wiring sizes of the involved

branch circuit conductors for all cases not involving service components, for

the smallest AWG size present in the circuit (Part A) and for the various

combinations found (Part B).

4.8 Specific Component Failure Causing the Fire

Table 15 shows the distribution of components whose failure caused the

fire by each of the major groups of components involved in ignition. For each

of these 94 cases (service components and the single transformer case are excluded), the description of the component whose failure caused the fire was provLded in a narrative, and the resulting 79 types of component failure

descriptions were organized into the 23 major groupings shown on the table.

Several analyses have been performed using these groupings, as described in

later sections, and the tabulation in table 15 provides some insights in

itself. (For example, over half of the lighting fixture fires - those

- 18 -
Table 13. Wiring Method and Component Involved in Ignition

Percentage of Wiring Methods

Nonmetallic

Sheathed

Cable

Knob and

Tube

Branch Circuit

Wiring 47% 25%

Cords and Plugs 32% 32%

Outlets and

Receptacles 62% 14%

Lighting Fixtures 64% 29%

Percentage of

Branch Cords

Circuit and

Nonmetallic sheathed

Wiring Plugs

cable 33% 20%

Knob and Tube 33% 38%

Armored Cable 0% 83%

Electric Metallic

Tubing 83% 0%

Other* 31% 38%

Armored

Cable

Electric

Metallic

Tubing Other*

Number

of

Cases

0% 16% 12% 32

tH 00 0% 18% 28

5% 0% 19% 21

0% 7% 0% 14

Components Involved in Ignition

Outlets Number

and Lighting of

Receptacles Fixtures Cases

27220% 46

12217% 24

17% 0% 6

0%17% 6

31% 0% 13%

The category "other" includes individual conductors in both rigid and

flexible metal conduit, and those cases where more than one type of wiring

was used within the involved circuit.

- 19-
Table 14. Branch Circuit Conductor Wire Sizes (A.W.G.)

A. Wire Size Distribution (Smallest AWG Size in Circuit)

Wire Size Number Percent

6 2 8 2

10 2 12 23

14 60

16 * 1 18 * 1 Unknown 4

Total 95

2 %

2%

2 %

24%

64%

1 %

1 %

4%

100%

B. Combinations of Wire Size

Number of Cases

6 only 2

8 only 2 10 only 1 12 only 22

14 only 53

10 and 8 1 12 and 10 1 14 and 12 7 16 and 12 1 18 and 14 1 Unknown 4

Total 95

These cases, where smaller than normal wire was found within branch

circuits, had power cord/lamp cord spliced directly into the involved

branch circuit.

- 20-
Table 15. Failure Mode by Component

A. Branch Circuit Wiring (34% of Total)

Mechanical damage or improper installation

(e.g., stapled, abraded, nailed, cut, other) 9 (28%)

Poor or loose splice (e.g., loose splice,

crimp, different wire types) 8 (25%)

Ground fault (e.g., water, ungrounded armored

cable, deteriorated insulation) 4 (13%)

Use of improper wiring in circuit

(e.g., steel, stranded) 3 ( 9%)

Knob and tube encapsulated 3 ( 9%)

Miscellaneous overload

(e.g., overloaded, short in range) 2 ( 6%)

Unknown 3(9%)

B. Cords and Plugs (30% of Total)

Mechanical damage or poor splice

(e.g., to extension cord or appliance cord) 11 (39%)

Overloaded extension cord 6 (21%)

Overloaded plug 2(7%)

Damaged plug (e.g., loose blade connector) 2 ( 7%)

Miscellaneous — plug (e.g., short, water) 2 ( 7%)

Miscellaneous — cord (e.g., deteriorated

insulation, electric blanket cord) 4 (14%)

Unknown 1(4%)

C. Receptacles and Outlets (21% of Total)

Loose or poor connection 8 (40%)

Mechanical damage (e.g., cracked, fire) 3 (15%)

Overloaded 2 (10%)

Miscellaneous (e.g., deteriorated, miswired,

plug inserted improperly) 3 (15%)

Unknown 4 (20%)

D. Lamp and Lighting Fixtures (15% of Total)

Loose or poor connection or splice, miswiring 5 (36%)

Combustibles too close (e.g., ballast, cloth

fixture, towel, insulation) 5 (36%)

Overlamped 3 (21%)

Miscellaneous (e.g., deteriorated insulation) 1 ( 7%)

Note that the failure mode descriptions are highly dependent on the main

component, that is, mechnical damage to branch circuit wiring may be of a different nature than mechanical damage to cords.

-21 -
involving overlamping or combustibles too close - do not involve failures

within the electrical system.) But it is also recognized that further refinement - aggregation, disaggregation or reaggregation - of these categories may

better reflect the important similarities in conditions. Suggestions are

invited, therefore, not only with regard to additional promising analysis of

fire characteristics versus component-failure scenarios but also with regard

to the groupings used to organize those scenarios for analysis.

5. CHARACTERISTICS AND PERFORMANCE OF OVERCURRENT PROTECTION DEVICES

The distribution of cases among the different types of overcurrent

protection devices are as shown in table 16. Edison-base fuses and circuit

breakers dominated, and most of the analyses in this section concern only

them.

Table 16. Type of Overcurrent Protection Device

Type of Device Number of Fires Percent of Fires

Circuit Breakers 54

Edison Base Fuses 39

Type "S" Fuses 1 Cartridge Fuses 0

No Device Present 1 Not Applicable* 13

Unknown 2 Total 110

49.1

35.5

0.9

0.0

0.9

11.8

1.8

100.0

In 13 of the 15 service component cases, the fire occurred outside the

building's overcurrent protection device, and so the type of device in use may not have been relevant. In the other 2 service component cases, there were two separate outside main breaker panels and the fire occurred in the

connection between them; therefore the types of devices used in these main

breaker panels were relevant for those cases.

5.1 Performance of the Overcurrent Protection Devices

Problems with the overcurrent protection devices were checked under two

headings - tampering and unusual conditions. Tampering generally referred to

conditions intended to defeat the overcurrent protection device, such as overfusing (or the analogous condition for circuit breakers, overamping),

- 22-
putting a penny or other metal insert behind a fuse, wrapping a fuse with

foil, or having no protective device at all. Unusual conditions included all

the conditions covered under tampering and other problem conditions, such as exposed wiring, poor workmanship, ground cut-offs, double taps, and bootleg or jackleg circuits.

Of the 39 Edison-base fuses, 15 (38%) interrupted the current, while 18

(46%) did not. For the remaining 6 fuses, 3 (8%) operated when the circuit

was interrupted by fire, and the other 3 (8%) had unknown performance. Of the

54 circuit breakers, 16 (30%) interrupted the current, while 26 (48%) did

not. For the remaining 12 cases, 2 (4%) operated when the circuit was damaged

by fire, and the other 10 (19%) had unknown performance.

Tampering and unusual conditions found at the panel were almost universal

for the Edison-base fuses. Of the 39 fuses, 32 (82%) were tampered with, 3

(8%) were not, and the tampering status was unknown for the other 4 panels

(10%). Similarly, unusual conditions were noted at the panel in 35 (90%) of

the cases, while 2 (5%) had none noted, and the other 2 (5%) were unknown. Of

the 32 cases of tampering, 31 (97%) involved overfusing; the other case

involved a penny behind the fuse. Two of the cases with overfusing also

involved a penny behind the fuse.

By contrast, unusual conditions at the panel were not found for most

circuit breakers and tampering was comparatively rare. Of the 54 circuit

breakers, 5 (9%) were tampered with, 46 (85%) were not. The tampering status

was unknown in the other 3 (6%) cases. Similarly, unusual conditions were noted in 14 (26%) of the cases and were not found in 39 (72%) of the cases.

The other one (2%) was unknown. All 5 cases of tampering involved overamping

(i.e., overfusing of circuit breakers). In 2 of these cases the circuit

breakers did automatically trip initially, but occupants reset them.

Of the 17 cases not cited as involving Edison-base fuses or circuit

breakers, one of the two cases with device cited as unknown was also cited as overfused and was stated to have been reset. The one case with no device was cited for tampering in that the circuit was left unprotected. Table 17 shows

the type of unusual panel conditions cited.

-23-
Table 17. Incidence of Unusual Conditions Found at Panel

(Unusual conditions were noted in 37% of the cases)

Fuses

Total Number of

A. Individual Conditions Conditions Cited % of Total

Overfusing 34 54%

Ground cut-off 8 11%

Bootleg/ jackleg circuits 7 11%

Double taps 6 9%

Poor workmanship 5 8%

Defeated 2 3%

Fused neutral 1_ 2%

63 100%

B. Combinations of Conditions Number of Cases % of Total

Overfusing alone 15

Overfusing and double taps 4

Overf using and ground cut-off 4

Overfusing and bootleg/ jackleg circuits 2

Overfusing and poor workmanship 1 Overfusing and defeating 1 Overfusing, double taps and

bootleg/ jackleg circuits 2 Overfusing, poor workmanship and

ground cut-off 2 Overfusing, bootleg/ jackleg circuits,

and ground cut-off 1 Overfusing, poor workmanship and

bootleg/ jackleg circuits 1 Overfusing, poor workmanship and

fused neutral 1 Defeated, bootleg/ jackleg circuits and

ground cut-off 1_ 35

42%

11 %

11 %

6 %

3%

3%

6%

3%

3%

3%

3%

3%

100%

-24-
Circuit Breakers

Total Number of

A. Individual Conditions Conditions Cited % of Total

Poor workmanship 7 29%

Ground cut-off 5 21%

Bootleg/ jackleg circuits 4 17%

Ove ramping 3 13%

Double taps 2 8%

Fused neutral 1 4%

Defeated 1 4%

Exposed wiring 1^ 4%

24 100%

B. Combinations of Conditions Number of Cases

Ove ramping alone 3

Poor workmanship alone 1 Fused neutral 1 Bootleg/ jackleg circuits 1 Poor workmanship and ground cut-off 2

Poor workmanship and bootleg/ jackleg circuits 1 Double taps and ground cut-off 1 Defeated and ground cut-off 1 Poor workmanship and exposed wiring 1 Poor workmanship, double taps and

bootleg/ jackleg circuits 1 Poor workmanship, bootleg/ jackleg

circuits and ground cut-off 1 14

% of Total

22%

7%

7%

7%

15%

7%

7%

7%

7%

7%

7%

100 %

Other

Unknown device: 1 with overfusing, poor workmanship and bootleg/ jackleg

circuits

1 with poor workmanship and bootleg/ jackleg circuits

No device present: 1 with unprotected circuits, exposed wiring and

bootleg/ jackleg circuits

-25-
Figure 1 shows the contrast in tampering and unusual panel conditions

between fuses and circuit breakers and shows the impact on the performance of

the devices. Both fuses and circuit breakers managed to interrupt current in some cases when they were tampered with or hampered by unusual conditions.

Fuses, however, always interrupted the current in those few cases when neither

of these conditions were present, but circuit breakers did not. This unusual

finding regarding circuit breakers stimulated several additional analyses

aimed at identifying the reasons for non-performance.

System alterations were present in the same proportion for fuses and

circuit breakers, and for both types of devices, interruption of current was more likely in a building that had had alterations than in one that had not.

This suggests that many alterations may have constituted improvements. Of the

39 fuse cases, 28 (72%) had had alterations and the other 11 had not. In the

54 circuit breaker cases, 39 (72%) of the electrical systems had been altered

and the other 15 had not. As for performance, 11 of the 28 fuses with system

alterations (39%) interrupted the current after the ignition, compared to 4 of

the 11 fuses without system alterations (36%). Thirteen of the 39 circuit

breakers with system alterations (33%) interrupted the current after the

ignition, compared to 2 of the 15 circuit breakers without system alterations

(13%). As noted earlier, further analysis of system alterations to determine

their effect will be done in order to determine the relevance of this factor

to this and other elements.

In summary, the pattern of performance for both major devices - circuit

breakers and Edison-base fuses - shows them failing to interrupt the current

in well over half the cases. For the fuses, the story is essentially one of

widespread tampering, but for the circuit breakers a promising explanation has

proved elusive in this initial analysis.

An attempt was made to classify the fires into cases where the overcurrent protection device should or should not have interrupted the current

with the classification made on the basis of a shorthand description of the

component and condition that caused the fire. This was done on the theory

that many of the circuit breaker cases might have been situations where

neither a fuse nor a circuit breaker would have been expected to work. This

-26 -
- 27 -

Figure

1.

Performance

of

Overcurrent

Protection

Devices,

by

Type

of

Device

and

with

Reference

to

the

Presence

or

Absence

of

Tampering

and

Unusual

Panel

Conditions
very preliminary review indicated that many fires involved circumstances where

neither a fuse or a circuit breaker would have been expected to work (e.g., a towel dropped on a portable lamp). An attempt will be made in the followup to

better classify this factor through additional review of each case, and will

be further discussed in the final report.

Table 18 shows some other characteristics that were checked for their

ability to suggest reasons why some circuit breakers failed to work. These

characteristics will be evaluated in more detail when the additional information on fuse and breaker operation is coded.

5.2 Overcurrent Protection Devices by Component Involved in Ignition

Table 19 shows how the type, problems and performance of overcurrent

protection devices varied across the four major types of components involved

in ignition. Fires involving switches and receptacles involved far more circuit breakers than did the other fires. This correlates with the fact

(noted later in this report) that switch and receptacle fires were much more

evenly distributed by building age than were other fires, and the newer

buildings, which tended to have lower rates of all other types of fires, were also much less likely to have fuses. Branch circuit wiring fires were more

likely in systems that had had alterations than were any other type of fire.

Tampering and unusual panel conditions were noted less often in cord and plug

fires than in other types of fires.

5.3 Overcurrent Protection Device Rating by Minimum Wire Size

of Branch Circuit

Table 20 compares the rating of the overcurrent protection device to the

smallest AWG size of the wire used in the branch circuit conductors supplying

current to the component involved in ignition.

Table 21 provides a further examination in terms of whether the overcurrent protection device operated, given the type of device, the rating of

the device and the size of the wire.

-28 -
Table 18. Miscellaneous Characteristics for Fires Where

Circuit Breakers Were Present

A. Extent of Flame Damage

**

Circuit Breakers

* Operated

Circuit Breakers

Did Not Operate*

B.

C.

Object of Origin 36% 69%

Area of Origin 14% 19%

Room of Origin 29% 8%

Beyond Room of Origin 21% 4%

Total 100% 100%

Number of Fires 14 26

Component Involved in Ignition

Branch Circuit Wiring 27% 19%

Cords and Plugs 40% 31%

Switches and Receptacles 20% 31%

Lighting Fixtures 13% 19%

Total 100% 100%

Number of Fires 15 26

Wiring Method

Nonmetallic sheathed cable 60% 65%

Knob and Tube 7% 12%

Electric Metallic Tubing 13% 12%

Armored Cable 0% 4%

Other 20% 7%

Total 100% 100%

Number of Fires 15 26

These figures exclude service component fires. Cases where the fire

damaged the circuit, causing the device to operate, or where it was not

known whether the device operated, are also excluded.

Note that one of the cases where the circuit breaker operated had unknown

extent of fire damage.

-29 -
Table 19. Overcurrent Protection Devices for Each

Component Involved in Ignition

Branch Circuit Wiring

Edison

Base

Fuses

Circuit

Breakers Combined

Number of fires 16 15 31

Percent of fires 52% 48% 100%

Percent with tampering 88% 14% (of 14) 53% (of 30)

Percent with unusual panel conditions 94% 27% 61%

Percent with system alterations 81% 80% 81%

Percent where device interrupted

current 69% (of 13) 44% (of 9) 59% (of 22)

(One case, not shown above, involved a type "S" fuse.)

B . Cords and Plugs

D.

Number of fires 11 16 27

Percent of fires 41% 59% 100%

Percent with tampering 88% (of 8) 0% (of 15) 30% (of 23)

Percent with unusual panel conditions 90% (of 10) 19% 46% (of 26)

Percent with system alterations 64% 69% 67%

Percent where device interrupted

current 40% (of 10) 43% (of 14) 42% (of 24)

(One case, not shown above, involved a device of 1unknown type.)

Switches and Receptacles

Number of fires 4 15 19

Percent of fires 21% 79% 100%

Percent with tampering 100% 20% 37%

Percent with unusual panel conditions 100% 33% 60%

Percent with system alterations 50% 73% 68%

Percent where device interrupted

current 50% 27% (of 11) 33% (of 15)

(One case, not shown above, had no overcurrent protection device.)

Lighting Fixtures

Number of fires 7 7 14

Percent of fires 50% 50% 100%

Percent with tampering 100% 0% 50%

Percent with unusual panel conditions 100% 29% 64%

Percent with system alterations 71% 57% 64%

Percent where device interrupted

current 0% (of 5) 29% 17% (of 12)

Note: The numbers in parentheses indicate that the percentages in question are based on less than the full number of cases. Such entries reflect exclusions of unknowns (i.e., unknown whether tampering was present, unknown

whether unusual conditions were present, or unknown whether device interrupted current) and exclusions of cases where the fire damaged the

circuit, causing the overcurrent protection device to operate.

-30-

k
Table 20. Wire Size and Overcurrent Protection

Device Rating by Type of Device

Edison Base Fuses

15 amp

20 amp

25 amp

30 amp

40 amp

50 amp

Total

Circuit Breakers

15 amp

20 amp

25 amp

30 amp

40 amp

50 amp

Total

Combined Data

15 amp

20 amp

25 amp

30 amp

40 amp

50 amp

Total

(Smallest AWG size in circuit)

AWG Wire Size

6 8 10 12 14

0

0

0

0

0

0_0

0

0

0

0

0

£

0

0 1 1 0 1 7 0 2 4

0 2 18

0 0 0

0 0 _0

0 6 30

0

0

0

0

0

2

_2

0

0

0

1

1£

2

0 5 26

1 12 2

0 0 0

0 0 0

0 0 0

0 0 0

1 17 28

0

0

0

0

0

2

_ 2

0

0

0

11£

2

0 6 27

1 13 9

0 2 4

0 2 18

0 0 0

0 0 0

1 23 58

16/18*

0

0

0

10

0_1

0

10

0

0

0_

1

0

10

10

0

2

Note: These figures exclude the service component cases. Also excluded are one case where the type of device was unknown, one Edison-base fuse case where the rating of the fuse was unknown, and 2 circuit breaker cases where the wire sizes were unknown.

These cases, where smaller wiring than normal was found within branch

circuits, had power cord/lamp cord spliced directly into the involved

branch circuit.

-31-
Table 21. Overcurrent Protection Device Performance by

Type and Rating of Device and Wire Size - Percentage of Cases Where Device Interrupted Current

(Smallest AWG size in circuit)

AWG Wire Size

Circuit Breakers

6/8/10 12 14 16/18

Fuses

15 amp * 100% (of 1) 0% (of 1) * 20 amp * 0% (of 1) 67% (of 6) * 25 amp * 100% (of 1) 33% (of 3) * 30 amp * 50% (of 2) 40% (of 15) 0% (of 1)

40 amp * * * * 50 amp * * * *

15 amp * 60% (of 5) 40% (of 20) * 20 amp * 10% (of 10) 100% (of 1) 100% (of 1)

25 amp * * * * 30 amp 0% (of 1) * * * 40 amp * * * * 50 amp 50% (of 2) * * *

Combined

15 amp * 67% (of 6) 38% (of 21) * 20 amp * 9% (of ID 71% (of 7) 100% (of 1)

25 amp * 100% (of 1) 33% (of 3) * 30 amp 0% (of 1) 50% (of 2) 40% (of 15) 0% (of 1)

40 amp * * * * 50 amp 50% (of 2) * * *

* No such cases

Note: Excluded from this table are all the cases excluded :from table 20 and a cases where either the fire caused the device to operate or it was unknown

whether the device operated.

-32 -
6. THE ROLE OF BUILDING AGE

Older buildings accounted for a disproportionately large share of the fires

examined, but building age was highly correlated with several other factors, and

so there is no clear indication of which factor(s) was the leading element in

raising the risk of electrical distribution fire. Table 22 shows the increase in

fire rate as building age increased. The fire rate for housing constructed in

the 1950's is about equal to the fire rate for all housing which is nearly three

times the fire rate for housing built in the 1960's and 1970's and just over half

the fire rate for housing built before 1940.

Table 22. Ratio of Electrical Fires to Housing Units by Age of Housing

Year of

Construction

Age of

Housing

in 1980

Estimated Percentage3

of All Housing Units

with that Age

Percentage of^

Fires in Housing

of that Age

Index-Ratioc of Fires to

Housing Units

1970-79 1-10 yrs 21.8 8.6 0.39

1960-69 11-20 yrs 21.5 6.7 0.31

1950-59 21-30 yrs 14.7 14.3 0.97

1940-49 31-40 yrs 11.0 14.3 1.30

Pre-1940 Over 40 yrs 31.0 56.2 1.81

Total 100.0 100.0 1.0

3 The percentage distribution for housing units built before 1970 is based on Census figures for housing units in the cities used in the study, i.e., of

all housing built before 1970 in those cities, 27.4% was built in 1960-69,

18.9% in 1950-59, 14.1% in 1940-49, and 39.6% before 1940. Because similar

figures for those particular cities were not available for the period of

1970-79, the national Census figure of 21.8% was used, and then the study

cities' distr Lbut Lon of pre-1970 housing units was pro-rated over the 78.2%

of all housing built before 1970. A check of national figures for pre-1970

periods suggest the cities' distribution is not significantly different from

the national distribution [2].

k Based on 105 study fires. This total excludes four fires where building

age was not recorded and the only fire in Oakland. The latter was excluded

on the theory that it would not be appropriate to include all the housing

units in Oakland in the building-age just to accommodate one fire.

c The index indicates how much higher or lower than the overall fire rate was

the fire rate for a particular building-age cohort.

-33-
6.1 Edison-Base Fuses and Circuit Breakers by Age of Build Lng

Fuses were phased out of most housing after 1950, so the use of fuses

versus circuit breakers is correlated with building age. Of the 31 fires in

buildings built between 1950 and 1980, 25 buildings (81%) had circuit breakers

while only 4 (13%) had Edison-base fuses, and no building built after 1959 had

fuses. One had a type S fuse, and the type of device was unknown in the

remaining one. By contrast, of the 74 fires in buildings built before 1950,

33 (45%) had Edison-base fuses, 27 (36%) had circuit breakers. A total of 13

had power company fuses only, and one had no device. Thus, the housing stock

of the pre-1950 period shows slightly greater presence of fuses than circuit

breakers, while the housing stock of post 1950 shows fuses to be a minor

factor.

The problem noted earlier involving failures of untampered circuit

breakers to interrupt the current was slightly more prevalent in older

housing. In 7 of the 22 fires (32%) involving untampered circuit breakers in

housing built in or after 1950, the current was interrupted by the circuit

breakers. Correspondingly, in 5 of the 22 fires (24%) involving untampered

circuit breakers in housing built before 1950, the circuit breakers acted to

interrupt the current. (Included in the base are 7 cases where Lt was not

determined whether the circuit breaker had operated and 2 cases where the

fire, rather than the electrical failure, caused the circuit breaker to

operate. These 9 cases split fairly evenly, 5 before 1950 and 4 after.)

Tampering with the overcurrent protection device is correlated with

building age primarily because use of fuses is correlated with building age,

as figure 2 demonstrates. Of the 29 fires in buildings built in 1950 or after

and having Edison-base fuses or circuit breakers, 3 of the 4 buildings with

fuses were tampered with, while only 1 of the 25 buildings with circuit

breakers were tampered with. This gives an overall tampering rate of at least

14% (4 out of 29). (The qualification "at least" is needed because in two

circuit breaker cases the report did not Indicate whether tampering had

occurred.) Of the 60 fires in buildings built before 1950 and having Edisonbase fuses or circuit breakers, 27 of the 33 with fuses were tampered with

while only 4 of the 27 with circuit breakers were tampered with, producing an

-34-
%

OF

TOTAL

QJ

<J •H>

QJ Q -35-

Figure

2.

Tampering

by

Year

Built

and

Type

of

Overcurrent

Protection
overall tampering rate of at least 52% (31 out of 60). (Again, the result is

qualified because in 4 fuse cases and 1 clrcuLt breaker case Lt was not determined whether tampering had occurred.

)

Interestingly, many of the tampered fuses worked anyway, and this was somewhat truer for older buildings than for newer ones. Of the 11 fires Ln buildings built in 1940 or after and having tampered fuses, 3 fuses worked

anyway for a success rate of 27%. Of the 10 fires in buildings built in the

1930's and having tampered fuses, 5 fuses worked anyway for a success rate of

50%. And of the 9 fires in buildings built before 1930 and having tampered

fuses, 4 fuses worked anyway for a success rate of 44%.

The pattern for unusual conditions (overfusing, poor workmanship, double

taps, bootleg circuits, etc.) found at the panel closely paralleled the

pattern for tampering; both were correlated with building age primarily

because the most common unusual condition found, overfusing, is more common

for fuses than cLrcuit breakers and fuses are more common in older buildings.

Of the 29 fires in buildings built in 1950 or after and having Edison-base

fuses or circuit breakers, unusual conditions were found at the panel Ln 3 of

the 4 buildings with fuses, while they were noted in only 5 of the 25 cases with circuit breakers. This gives an overall unusual conditions rate of at

least 28% for buildings built in 1950 or later. (This qualification is needed

because in one of the circuit breaker cases, it was unknown if unusual conditions existed.) Of the 60 fires in buildings built prior to 1950 and having

Edison-base fuses or circuit breakers, unusual conditions were found in 30 of

the 33 cases with fuses compared to 8 of the 27 with circuit breakers. This

gives an overall unusual conditions rate of at least 63% for buildings built

prior to 1950, again, most likely due to the frequency of overfusing found.

(The qualification is needed because in one fuse case and one circuit breaker

case, it was unknown whether unusual conditions were present.)

6.2 System Alterations by Age of Building

As expected, system alterations were rare in newer buildings, common in

somewhat older buildings, and almost universal in very old buildings. Of the

16 buildings built in the 1960's and 1970's, only 5 (31%) had had altera-

- 36-
tions. Of the 55 buildings built in the 1930' s, 1940' s, 1950' s, however, 38

buildings (69%) had had alterations. And of the 34 buildings built prior to

1930, 32 (94%) had had alterations. The significance of this pattern is

unclear, however, because, as noted earlier, overcurrent protection devices -

both fuses and circuit breakers - were more likely to operate in properties

that had had alterations then in those that had not, and, as noted in section

4.2, the relevance of the alterations to the fire has not yet been determined.

6.3 Components Involved in Ignition by Age of Building

Table 23 shows how the involvement of different major classes of components differs for pre-1940 and post-1940 housing. The most notable pattern is

for service equipment, which has a much larger share of its fires in older

housing than do the other component groups. At the other extreme, branch

circuit wiring and switches and receptacles show the smallest differences in

fire rates between old and new buildings. (These figures may conceal an age

dependency for branch circuit wiring, however.) Ninety-three percent of these

fires occur in housing 20 years old or older. If the cutoff for checking age

effects had been made at 20 years rather than 40 years, the picture for branch

circuit wiring would have been much different. This will be further evaluated

for the final report, and correlated with system age if possible.

6.4 Wiring Method by Age of Building

Table 24 presents the distribution of wiring method by age of building as given in the cases, and type of overcurrent protection device; the figures

exclude service component fLres and the single low voltage transformer fire.

Nonmetallic sheathed cable was present in most of the fires in buildings

constructed in or after 1950 and is nearly as common in fires in buildings

constructed before 1950 as the leading wiring method, knob and tube. Circuit

breakers were used primarily with nonmetallic sheathed cable, while fuses were

used with nonmetallic sheathed cable and knob and tube wiring. When electric

metallic tubing was used, it was solely with circuit breakers, and when

armored cable was used, it was usually with fuses. The "other" category in

table 24 is primarily made up of hybrid wiring systems, that is a mix of

multiple wiring methods within the individual system.

-37-
Table 23. Ratios of Fire Rates for Post-1940 and Pre-1940

Housing by Type of Component Involved Ln Ignition

Ratio of Fire Rate

Type of

Component

Housing Units Built Ln 1940 or After

Housing Units Built

Before 1940

for Pre-1940

Units to Fire

Housing

Rate

Involved in

Ignition

Number of

Fires

Percent of

Fires

Number of

Fires

Percent

of Fires

for Post-1940

Units3

Housing

Service

Equipment 3 21% 11 79% 8.4

Branch

Circuit

Wiring 16 53% 14 47% 2.0

Cords and

Plugs 10 37% 17 63% 3.8

Switches and

Receptacles 11 55% 9 45% 1.8

Lighting

Fixtures 6 46% 7 54% 2.6

All

Components 46 43.8% 59 b 56.2% 2.9

3 This is given by the ratio of the prior to 1940 and after 1940 percentages,

divided by .449, which is the ratio of housing units built prior to (31.0%)

and after 1940 (69.0%), as noted in table 22.

b The total includes one low-voltage transformer case, which does not fit

with any of the major component groups.

-38-
Table 24. Wiring Method by Building Age and Type

of Overcurrent Protection Device

(Excluding fires in service components or low voltage transformers)

A. All Fires

Wiring Method Circuit Breakers

Edison Base

Fuses Other/ Unknown Total

Nonmetallic sheathed

cable 60% 32% 33% 48%

Knob and Tube 11% 45% 33% 26%

Electric Metallic Tubing 11% 0% 0% 6%

Armored Cable 2% 13% 0% 6%

Other 15% 11% 33% 14%

Total 100% 100% 100% 100%

Number of Fires 53 38 3 94

(These totals include 4 fires not included below - 3 with age unknown and the one fire from Oakland, which is not included in any distribution by age for reasons given earlier.)

B. Fires in Housing Built Prior to 1950

Edison Base

Wiring Method Circuit Breakers Fuses Other/Unknown Total

Nonmetallic sheathed

cable 41% 28% 33% 34%

Knob and Tube 22% 47% 33% 35%

Electric Metallic Tubing 15% 0% 0% 6%

Armored Cable 4% 13% 0% 8%

Other 19% 13% 33% 16%

Total 100% 100% 100% 100%

Number of Fires 27 32 3 62

C. Fires in Housing Built in or After 1950

Edison Base

Wiring Method Circuit Breakers Fuses Other/Unknown Total

Nonmetallic sheathed

cable 88% 75% — 86%

Knob and Tube 0% 0% — 0%.

Electric Metallic Tubing 8% 0% — 7%

Armored Cable 0% 25% — 4%

Other 4% 0% — 4%

Total 100% 100% — 100%

Number of Fires 24 4 0 28

Note: Percentages may not total to 100% because of rounding error.

- 39 -
6.5 Separate Grounding Conductor

Of the 95 cases not involving system components, 25 (26%) had separate

grounding conductors, while 67 (71%) did not and 3 (3%) were undetermined.

This does not necessarily indicate that most circuits were ungrounded. An

attempt will be made in the followup effort to evaluate grounding of involved

circuits.

7 . THERMAL INSULATION

Information on thermal insulation, including type (cellulose, mineral,

etc.) and age was asked for in the questionnaire. Except for several cases involving cellulose insulation, however, the coding detail was insufficient

for further analysis.

Cellulose insulation was noted to be present in 9 cases in this study.

Of the 7 cellulose insulation cases for which the installation date was known,

all had had the Insulation installed within 2 years of the fire.

Of the 8 cellulose insulation fires not involving service components, 6

(75%) involved branch circuit wiring and 2 were light fixture fires. In 4 of

the 8 cases mechanical damage or a poor splice or connection was involved.

Encapsulation or combustible too close was given as the faLlure mode in 3 cases (2 involving knob and tube wiring). Most of the fires involving cellulose insulation resulted from an overheat condition rather than from arcing.

Although the data on cellulose insulation are very limited, the need for

further evaluation is suggested by this data. An evaluation of the percentage

of homes containing cellulose insulation in the subject cities to contrast

relative exposure to relative involvement in fires would be useful. The

dominant failure mode involving cellulose insulation for the cases available

appears to relate to encapsulation and/or proximity of combustible insulation

to wiring undergoing an overheat condition. As very little detailed information on the contribution of thermal insulation was coded, a more comprehensive

examination of the cases involving all types of thermal insulation will be

attempted in the followup.

-40-
8. SERVICE COMPONENT FIRES

As noted earlier, the category of service components consists of utility

supply conductors, service entrance wiring, service equipment and distribution

panels. Service components were cited as the component involved in ignition

in 15 cases, or 14% of the total. As noted in section 5, service component

fires were relatively rare in buildings under 40 years of age. None of the 6 cases involving service entrance wiring occurred in buildings less than 40

years old.

No consistent single failure mode or contributor was noted for service

components. A total of 5 fires were attributed to deteriorated insulation,

with water accumulation noted in 3 cases. In 4 cases the primary causal

factor was given as improper installation of a recently altered system,

resulting in a ground fault or overload condition. Alterations in progress

were responsible for 2 additional fires, one resulting from accidental contact

with high voltage lines, and one from the removal of support for the service

entrance cable. Finally, 4 cases were essentially unknown, including 2 ground

faults from unspecified failures.

9. BRANCH CIRCUIT WIRING FIRES

Several aspects of fires involving branch circuit wiring have been

discussed in earlier sections. Several additional tabulations are discussed

here.

A total of 68% of the involved branch circuits contained at least some

#14 AWG wire. This is consistent with the wire size distribution across all cases listed in table 14. A separate grounding conductor was present in 22%

of the branch circuit cases, slightly less than the overall 28%.

Most of the involved branch circuits were 120 volt (91%) and 75% were

general purpose (lighting and receptacle) circuits. The remainder were divided equally between small and large appliance circuits.

-41 -
In 12 cases (38%) one or more electrical components supplied by the

involved circuit were noted to be "on" at the time of the fire. In 6 cases

(19%) it was indicated that no electrical components were "on" at ignition,

and the remaining 14 cases (44%) were unknown. The connected circuit load on

the involved branch circuit was not known in 53% of the cases. In the 9 cases where a connected circuit load was provided, it ranged from 3 watts to 2,160

watts.

Overloading of the circuit was unknown in 9 of the cases. Of the

remaining 23 cases, 7 (30%) were noted to be overloaded. All of the involved

branch circuits had been damaged electrically, damaged by the fire, or both.

In addition, 7 were found to have been damaged mechanically, 2 were corroded

and one had multiple types of damage noted.

Finally, of the specific component failures causing the fire, mechanical

damage (most often by staples) and splice problems stand out.

10. CORD AND PLUG FIRES

Of the 28 fires involving cords and plugs, 16 (57%) involved extension

cords, 5 were permanently attached appliance cords, 5 were detachable appliance cords and 2 were Christmas tree light cords.

As indicated in section 5.3, cord and plug fires occurred more often in

older buildings than did any other non-service component fires. This may be

largely due to the use of extension cords to extend outmoded, inadequate or defective branch circuit wiring in older buildings. This hypothesis is

supported by the fact that a cube tap or other device was used to extend the

wiring of the building in 54% of the cases. Also in all 16 extension cord

cases, the cords were noted to be replacing permanent building wiring.

The involved cord was plugged into a grounded receptacle in only 6 cases,

4 of which were in buildings less than 15 years old. All of the ungrounded

receptacles were in buildings over 25 years of age, and 81% were in buildings

over 40 years old.

-42-
Since the dominant problem in cords and plugs appears to be the use of

extension cords to replace building wiring, the remaining analysis in this

section focuses on them. The misused extension cords were also heavily used,

compounding the problem. Of the 16 extension cords, 8 were being used daily,

24 hours per day; and another one was used daily 8 hours per day. A total of

3 were used daily, 3 hours per day; 1 was used daily, 2 hours per day; and one

was used about one hour per month; one had just been put into use; and one was used daily for an unknown time. This pattern of extensive operation contrasted with the pattern for appliance cords, where only 3 of 10 were in use

24 hours per day. In any event, appliance cords are often designed to stand

up to heavy use.

One-half of the appliance cord failures were at the plug, while only 1 of

the 16 extension cord failures occurred at the plug, possibly indicating that

the weak link in extension cords is the cord itself. A total of 10 of the 16

extension cords were noted as lamp cord, while 8 of the 10 cords used with

appliances were noted to be the generally heavier duty appliance or power

cords.

While all of the 7 appliance cords where cord age was known were over 7 years old, only 2 of the 12 extension cords of known age were over 7 years

old. The remaining 10 were under 5 years old, and 4 were one year old or less. This indicates that, unlike appliance cords, the effect of age in

extension cords may be a secondary issue relative to the issue of use, and

misuse, of the cords.

Except for the predominance of plugs and older cords, there was no clear

pattern of specific failure mode for appliance cords. A clear pattern of

misuse of extension cords is indicated, however. The specific failure mode

was given as mechanical damage in 44% of the cases, overloading in 44% of the

cases, and splicing in the remaining 12%. Although splicing was indicated as the specific failure mode in only 2 cases, 8 of the 16 extension cords had

been spliced (versus only 1 of the 10 appliance cords). The frequency of

overloading fires is most likely explained by the use of the cords to replace

or extend building wiring. The mechanical damage problem may be In part

explained by cord location, as in 14 of the 15 cases where location was known.

-43-
the extension cord was noted to be improperly located, often in multiple

ways. A summary of the ways in which extension cords were improperly located

is given in table 25.

Table 25. Details of Improper Location of Extension Cords

(Improper location noted in 93% of cases where location was known)

Nature of Improper Location Frequency Noted

On floor in traffic areas Attached to building surfaces with nails, staples

Through doorways, windows, etc.

Wrapped around objects

Through holes in walls, floors

Close to heaters, hot objects

754

3

2

1

NOTE: Some cords had more than one feature of improper location. The 22

location problems correspond to 14 cases.

Misuse of extension cords was responsible for most of cord and plug fires

in this data base. While such misuse is difficult to address, a more detailed

examination of extension cord failure modes will be attempted in the followup,

to determine possible alternatives, such as individually fused cords, a larger

wire size or improved insulation, which might minimize problems resulting from

overloading and some kinds of mechanical damage.

Fires in receptacles were more evenly distributed over building age than

fires in any other component involved in ignition, and this fact correlated

with a higher than usual percentage of fires occurring in homes with circuit

breakers. Splices and connections were notable as problems, suggesting that

loose connections between the receptacles and the wiring played a leading role

in ignition, and there was a notably low proportion of ungrounded receptacles.

11. SWITCHES, OUTLETS AND RECEPTACLE

-44-
11.1 Age of Building and Overcurrent Protection Devices

As noted in section 5, receptacle fires are much less concentrated among

older buildings than are other fires. For all fires, the fire rate in pre1950 buildings is nearly three times the fire rate in post-1950 buildings, but

for receptacles the fire rate in pre-1950 buildings is less than twice as great. Buildings built in or after 1960 account for 30% of receptacle fires

but only 12% of all other fires. This suggests that, relative to other parts

of the electrical system, receptacles have a larger share of problems that are

there from the beginning, as contrasted with problems that show up only after

the passage of decades.

Since fuses were largely phased out after 1950, the use of circuit

breakers is correlated with building age, and so receptacle fires show a significantly higher percentage of cases with circuit breakers present.

Receptacles were protected by circuit breakers in 75% of the cases versus 20%

by Edison fuses and 5% (one case) with no device. This compares with 51%

circuit breakers, 46% Edison fuses and 3% other devices in all other cases not

involving system components or low voltage transformers.

11.2 Problems with Splices and Connections

Receptacle fires accounted for a major share of fires at splices and

connections. For receptacle fires, 55% were at splices or connections,

compared to 38% of all other fires, excluding fires involving system components or low voltage transformers, where only 19% of fires were at splices or connections.

If this pattern of fires at splices and connections suggests a pervasive

problem with loose connections, the specifics of components whose failure

caused the fire strengthen that suggestion. Six of the 11 fires at splices or connections (10 of which were copper wiring) definitely involved loose connections. Three others had the component causing the fire listed as unknown or uncertain. The other two consisted of one case with an old, deteriorated

outlet and one case with poorly installed aluminum wiring.

-45 -
Of particular Interest is the pattern for the 4 fires involving backwired receptacles. First, there is the fact that 4 back-wired receptacle

cases appear to represent a larger than expected proportion of the 19 receptacle cases where it was known how the receptacle was wired. Second, 2 of

those 4 cases definitely involved a loose connection, and a third involved a fire at a splice or connection where the component causing the fire was uncertain.

11.3 Grounding

Of the 17 receptacle fires where it was known whether the receptacle was grounded, 8 were grounded (47%) and 9 were not. The 8 that were grounded

consisted of 4 with the grounding conductor going directly to the receptacle,

one each with the conductor going to an isolated screw in the outlet box or a grounding clip, and 2 involving some other arrangement.

Grounding was far more prevalent in newer buildings. In the 8 buildings

built in or after 1950, 5 (63%) had grounded receptacles - and it was 67% for

buildings built in or after 1960 - while only 3 of the 9 buildings built prior

to 1950 (33%) had receptacle grounding. (These calculations exclude the three

cases where it was unknown whether the receptacle was grounded.)

There were 12 cases involving metal outlet boxes where it was known

whether the box was grounded; it was not grounded in 67% of those cases. The

relationship to age was even more pronounced here. Of the 4 buildings built

in or after 1950, 3 (75%) had grounded outlet boxes, while only 1 of the 8

pre-1950 buildings (13%) did.

11.4 Other Factors

Several elements that had been considered likely to emerge as factors in

receptacle fires did not. Only one of the fires involved a receptacle located

near a heating unit and only one involved a receptacle surrounded by thermal

insulat ton.

-46-
Recent alterations, replacements, rewirLng or installation were less

often cited in receptacle fires (2 of 19 cases, or 11%) than in other fires

(15 of 70 cases, or 21%), excluding service components and low voltage transformers. (These figures also exclude 4 cases where recent changes were unknown and one case with recent fire damage.)

12. LIGHT FIXTURE, LAMPHOLDER AND PORTABLE LAMP FIRES

Of the 14 fires involving light fixtures, lampholders and portable lamps,

13 involved incandescent lights, and only one involved a fluorescent fixture.

The failure of the fluorescent fixture was due to the ballast being installed

too close to combustible material. Three of the remaining incandescent light

fires also were not electrical in nature, as 2 were caused by the ignition of

combustible material draped over lighted portable lamps, and the third was the

ignition of a home-made macrame fixture due to over-heating. Of the remaining

10 fires, one resulted from a loose cord connection in a portable lamp and the

other 9 involved light fixtures permanently connected to building wiring.

Of these last 9 fires, 3 were caused by overlamping of the light fixture,

and one related to the encapsulation of a light fixture by cellulose insulation. Two cases involved porcelain lampholders - one caused by deteriorated

insulation and the other by a loose connection - and one case was a juryrigged metal and plastic fixture attached to the building wiring by lamp cord

with taped splices. The remaining 2 fixtures were permanently connected, and

the failure mode was indicated as a loose splice in one and in the other an

improper crimp in the supply to the fixture which energized the fixture,

igniting Lnsulation. Of the last 5 cases (all electrical failures in permanently connected fixtures) 2 had been recently worked on, one had not, and the

other 2 were undetermined.

13. CONCLUSIONS

This initial analysis of 110 electrical fires has produced a number of

intriguing hypotheses on the factors that cause or exacerbate electrical

fires. Some of these hypotheses and subject areas will be the subject of

further investigation, either through refined analysis of these 110 cases or through analysis of additional cases.

-47 -
Among the hypotheses and areas that will be examined further are:

(1) the factors that cause overcurrent protection devices to fail to operate,

particularly explanations for the failures of untampered circuit breakers;

(2) the role of extension cords misused as permanent extensions of basic

wiring as the apparent dominant factor in fires involving cord and plugs; and

(3) the problem of loose connections between receptacles and wiring

(especially back-wired receptacles), which appears to be the leading failure

mode for receptacle fires.

Additional steps will include an examination of the size of the total

national fire problem associated with each of the major electrical components

and failure scenarios, using the NFIRS data base. Also, since system alterations are more the rule than the exception, and especially in light of some of

the correlations with alterations, the cases will be re-examined with the

intent of separating system improvements from system downgrades. A second

attempt will be made to establish workable groupings of the numerous component-causing-f ire scenarios according to physical similarities, likelihood of

activating overcurrent protection devices, and other criteria relevant to this

analysis. If further data collection is done, the basic questionnaires will

be re-examined to identify questions and answer formats that should be added,

dropped, or revised to improve the quality of information obtained on any

future cases. Finally, additional information contained in the electricians'

reports and summaries of overcurrent protection will be encoded, added to the

data files and analyzed.

These are leading examples, and this list of next steps is not intended

to be exhaustive. Reader response is encouraged on all aspects of the results

so far and the course of the research.

14. ACKNOWLEDGEMENTS

The authors gratefully acknowledge the substantial contributions of

Mr. Richard Bukowski, Center for Fire Research, who has provided his electrical engineering expertise to both the review of cases and to the analysis of case data. The efforts of John Ricketts in the review, clarification and

compilation of the cases has been invaluable to this project, as have the

-48 -
advice and suggestions of Linda Smith and Ed Krawiec of the Consumer Products

Safety Commission. Finally, the efforts of the numerous fire service and

electrical investigators in the cities of Akron, Grand Rapids, Long Beach,

Oakland, Portland, Sacremento, San Diego, San Francisco, San Jose and Toledo,

who provided the data for this study, are gratefully acknowledged.

15. REFERENCES

[1] Uniform Coding for Fire Protection, 1976, NFPA NO. 901, National Fire

Protection Assn., Boston, MA 02210, 1976.

[2] Statistical Abstract of the United States: 1980, U.S. Bureau of the

Census, December, 1980.

[3] Fire in the United States, Third Edition, Federal Emergency Management

Agency, Washington, DC 20472, p. 44.

- 49-
NBS-114A irev. 2-80

U.S. DEPT. OF COMM.

4.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR 2 REPORT NO.

NBSIR 83-2677

. Performing Organ. Report No.

TITLE AND SUBTITLE

ANALYSIS OF ELECTRICAL FIRE INVESTIGATIONS IN TEN CITIES

Publication Date April 1983

5. AUTHOR(S)

Alan Gomberg and John R. Hall, Jr.

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7. Contract/Grant No. national bureau of standards

DEPARTMENT OF COMMERCE S. Type of Report & Period Covered

WASHINGTON, D.C. 20234

Interim Report

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

Consumer Product Safety Commission

5401 Westbard Ave.

Bethesda, MD 20016

10.

SUPPLEMENTARY NOTES

Q2| 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)

This interim report describes the progress and conclusions to date on an analysis of electrical fire cases by the Center for Fire Research, National Bureau

of Standards for the Consumer Products Safety Commission. The report describes

the 110 detailed electrical fire investigation reports from 10 participating cities,

and discusses preliminary findings resulting from analysis of the computerized data

from those reports. These preliminary findings are being used to guide a follow

on effort, to be reported on at a later date, to obtain, encode and analyze

additional data from the original 110 cases, in order to better define and describe

the most significant failure modes of electrical components and the sequences of

events which lead to electrical fire ignition.

12.

KEY WORDS (Six to twelve entries ; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Electrical; electrical fires; fire cause; fire data; ignition.

13. AVAILABILITY

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| | For Official Distribution. Do Not Release to NTIS

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