afci report - nasfm 2002

AFCI INQUIRY AND REPORT August 1, 2002

Consumer Product Safety Task Force National Association of

State Fire Marshals

October 1, 2002 The National Association of State Fire Marshals represents the most senior fire safety officials of each of the 50 states and District of Columbia. Our mission is to protect life, property and the environment from fire. Over the past year, we have heard concerns raised about the price, availability and effectiveness of a relatively new technology known as Arc Fault Circuit Interrupters (AFCIs), which are designed to prevent fires originating in electrical wiring. These concerns caused us to reconsider our endorsement of AFCIs. The attached report provides details of our inquiry and the resulting recommendations to our membership. Having conducted this inquiry, we are persuaded that the criticisms being stated are without merit and that AFCIs should be added to the electrical and fire safety requirements in all jurisdictions. The most recent editions of the National Electrical Code require AFCIs for residential bedrooms of new homes. If there is one valid criticism of AFCIs, it is that they are not required more broadly. This is a criticism we can and will address in the immediate future. We hope this report is helpful to you as you strive to protect the people of your state. Sincerely, Donald P. Bliss President Attachment

Executive Summary The purpose of this inquiry and report is to reconsider National Association of State Fire Marshals support of the technology known as Arc Fault Circuit Interrupters (AFCIs), which are designed to prevent fires originating in electrical wiring due to unwanted arcing. Our inquiry was prompted by concerns raised about AFCIs with electrical and building code authorities considering adoption of National Electrical Code requirements for AFCIs. To approach this matter in a fair and objective fashion, we contacted the three organizations on record against AFCIs: the National Association of Home Builders (NAHB) and two consultancies, Bernard Schwartz (who represents a group called the National Multi Housing Council) and Mike Holt, of Mike Holt Enterprises, Inc. The responses from NAHB and Messrs Schwartz and Holt are shown in Appendix B. Their concerns may be summarized as follows: AFCIs are unneeded, cost too much, are not yet available and do not work. In addition to seeking elaboration from NAHB, Schwartz and Holt, the Consumer Product Fire Safety Task Force conducted four separate inquiries, all of which are described in greater detail over the following pages. The first inquiry was a review of fire incident data pertaining to fires caused by arc faults, to determine need. The second inquiry was a survey of retail stores selling AFCIs, to determine the current retail price of these devices. The third inquiry was made of all four AFCI manufacturers to secure their assessment of supply. The fourth inquiry was made of technical experts familiar with the causes of electrical fires, and the various technologies available to address those hazards. This report is divided into several sections. Section 1 contains the assignment made by NASFM President George A. Miller that initiated this inquiry and report. It begins on page 3. Section 2 provides a brief history of the AFCI technology and the adoption of Section 210-12 of the 2002 National Electrical Code. It begins on page 5. Section 3 contains the conclusions of our various inquiries, beginning on page 7. Section 4 begins on page 12 and lists the recommendations of the Task Force based on the conclusions. Supporting appendices for all sections begin with Tab A and are referenced throughout the report.

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The overall conclusion we draw from this work is that AFCIs are the most promising fire protection technology since the advent of the smoke detector. The criticisms that have been raised are unsupported by the facts, and appear to be little more than yet another campaign to place the economics of housing above the safety of American families. Respectfully submitted, Donald P. Bliss, Chair Consumer Product Fire Safety Task Force

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M E M O R A N D U M ________________________________________________________________________ Date: May 30, 2002 TO: Donald P. Bliss, Dr. Margaret Simonson FROM: George A. Miller RE: Fact Findings: Arc Fault Circuit Interrupters ________________________________________________________________________ NASFM has received numerous reports from its members, the US Consumer Product Safety Commission technical staff and others regarding claims being made about the effectiveness of arc fault circuit interrupters (AFCIs). Last year, your respective two committees – the Science Advisory Committee and Consumer Product Fire Safety Task Force – advised NASFM that AFCIs are an important new fire safety technology that should be required in as many structures as possible. Since then, we have heard three broad criticisms of AFCIs. We should be in contact with those individuals who are making these statements. You will receive my file on this in the next few days. I would like to ask the Consumer Product Fire Safety Task Force to seek information and assess the first two:

1. That AFCI producers cannot meet the demand that will be created by changes to the National Electrical Code.

2. That AFCIs add too much to the cost of a home.

I also would ask that the Science Advisory Committee (SAC) concern itself with claims that arc fault circuit interrupters do not work. Given the sophistication of electrical code officials, one criticism of AFCIs surprises me. Reportedly, code officials are being told that AFCIs do not address all types of arcing. One would hope not – a standard electrical switch is a series arc and poses no harm.

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I am sure that no one knowledgeable in electrical engineering would make this claim. It is my understanding that AFCIs are designed to detect only the harmful types of arcs that could lead to a fire. Please give this matter your immediate attention. I would like a report by June 10. My fear is that code officials are being misled at a time when adoption of the code is in full swing in several states. If either of you sense that inaccurate information is being intentionally distributed to interfere with public safety, I would like to know immediately so that we might notify the Attorneys General in states so affected. cc NASFM Membership

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History of AFCIs and Their Inclusion in the National Electrical Code

Proposal to mandate low-instantaneous trip circuit breakers for dwelling units

made by Electronics Industry Association in 1993 for the 1996 Code. The objective was to enhance fire safety. The proposal was rejected based on considerations such as nuisance tripping, and the Panel Statement included recommendations for further analysis including electronic sensing.

In 1994, Underwriters Laboratories (UL) began working with all interested

parties involving AFCIs to develop the requirements for an AFCI safety standard.

Research sponsored by the U.S. Consumer Product Safety Commission

(CPSC) in 1995 studied ways to reduce home wiring fire risk with new technology.

Arc-Fault Circuit-Interrupter (AFCI) technology identified by CPSC as “a

promising new technology.” In March 1996, UL issued a Report of Research on Arc-Fault Detection

Circuit Breakers. First production AFCI devices appeared in 1997. CPSC electrical engineers

tested the new AFCIs on the market and found these products to be effective. The results of many years of research, development and technical meetings

at UL were used as the basis for development of UL 1699, Standard for Arc-Fault Circuit Interrupters, published in February 1999. The commercially available AFCIs were listed as Branch/Feeder AFCIs based on requirements in the standard.

The National Electrical Code (NEC) requirement for AFCIs was supported by

CPSC staff and adopted in the 1999 edition (§210-12), with a 2002 effective date.

Branch/Feeder AFCIs became readily available in stores in 1999.

NEC 2002 edition (§210-12b): AFCIs required for branch circuits providing

power to outlets in dwelling unit bedrooms (new construction). NEC 2005 edition: Deadline for proposals is Nov 1, 2002.

CPSC staff submitting AFCI proposal for existing homes that undergo

electrical service replacement.

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NOTE: The NEC is a model code for electrical wiring. It is up to individual states and other Authorities Having Jurisdiction (AHJs) to adopt the code according to their own initiative and schedules. Therefore, different states and AHJs may have different editions of the NEC in force at a given time, some have a different electrical code in place, and some do not have an electrical code at all.

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Conclusions In an effort to prevent or reverse adoption of Section 210.12 of the 2002 National Electrical Code in states and localities, certain individuals and organizations are raising concerns with state and local electrical safety and building code authorities regarding the cost, availability and effectiveness of arc fault circuit interrupters (AFCIs). Opponents of AFCIs have stated for the record, before electrical safety authorities and in response to NASFM’s inquiries, that: • AFCIs are not needed based on current fire losses. Finding: The data in support of AFCIs are compelling. While conventional circuit breakers are designed to detect overloads and short circuits, AFCIs are designed to protect against fire by continuously monitoring the electrical current in a circuit and shutting off the circuit when many unintended arcing conditions occur. According to the National Fire Protection Association and National Fire Incident Reporting System data, during the five-year period from 1994-1998, there were an average of 73,500 total electrical fires annually, which were responsible for 591 deaths, 2,247 injuries, and property damage totaling $1,047,900,000.1 The electrical problems that lead to these fires went undetected by conventional circuit breakers. Of these 73,500 electrical fires, 60,900 or 82% were caused by arcing and not by overloads or short circuits. Additionally, the US Consumer Product Safety Commission technical staff, after conducting a great deal of independent research on AFCIs, estimates that 50-75% of residential electrical fires can be prevented by employing AFCI technology. 2That means that of the 73,500 electrical fires annually, AFCIs could potentially prevent 55,125 fires and save more than 440 lives, 1,685 injuries, and $785,925,000 in property damage, when AFCIs work their way into electrical codes for installation throughout the house. (See Appendix C.) • AFCIs cost in excess of $125 per unit.

Finding: NASFM’s survey of the two largest hardware retailers, Home Depot and Lowe’s, in nine US cities was completed on June 14, 2002, and reveals retail prices that range from $34.97 to $39.97 for both 20- and 15-amp units

1 Custom tables on structure fires involving electrical arcing or improper operating electrical equipment in one-two family dwellings prepared by Marty Ahrens, NFPA, Quincy, MA, March 2001 and custom tables on structure fires involving electrical arcing in one-two family dwellings, prepared by Marty Ahrens, NFPA, Quincy, MA, May 2002. 2 King, William H., Jr., Chief Engineer for Electrical and Fire Safety, Division of Electrical Engineering, US Consumer Product Safety Commission, in discussion with the NASFM Science Advisory Committee, July 14, 2002.

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with contractor’s prices at typically discounted levels. (See Appendix D.) To meet the current NEC code, the CPSC estimates that two (2) AFCIs are needed per household. While the per-unit cost of an AFCI is greater than the $5 cost of a standard circuit breaker, cost-benefit analyses must also include an estimate of lives saved due to the technology and take into account the fact that, once AFCIs are installed, the benefits are cumulative for the life of the structure. The CPSC is finalizing a cost-benefit analysis of AFCIs that should be ready by Fall of 2002.

• AFCIs are not yet available in enough configurations and in enough markets

to allow for compliance with the NEC.

Finding: This statement may have been true at one time, but NASFM’s survey of three AFCI manufacturers indicates sufficient manufacturing capacity to satisfy the AFCI demand created by the NEC. Of the major electrical equipment manufacturers, all four manufacture AFCIs in every configuration required to meet the code. At least one manufacturer has developed and soon will market an AFCI that can be used in any of the three most common circuit box/breaker boards or panels. (See Appendix E.) Since 2001, Vermont has required AFCIs for all living spaces in homes, and State Fire Marshal Robert M. Howe reports that supply has not been a problem.

• AFCIs are not reliable or effective.

Finding: A CPSC fact sheet on AFCIs states, “Several years ago, a CPSC study identified arc fault detection as a promising new technology. Since then, CPSC electrical engineers have tested the new AFCIs on the market and found these products to be effective.”

No device will ever prevent all of the fires it is intended to address. Consultations with the NASFM Science Advisory Committee, US Consumer Product Safety Commission, Underwriters Laboratories and SP Swedish National Testing and Research Institute all resulted in positive assessments of AFCI technology.3 AFCIs have undergone rigorous testing and have been

3 The following experts reviewed and commented on the documents shown in Appendix B: For NASFM: SP Swedish National Testing and Research Institute’s Margaret Simonson, PhD, Chair, Science Advisory Committee; Donald P. Bliss, State Fire Marshal and Director of Fire Safety and Emergency Management, New Hampshire; Walter Smittle III, retired West Virginia State Fire Marshal. For the US Consumer Product Safety Commission: William H. King, Jr., Chief Engineer for Electrical and Fire Safety, Division of Electrical Engineering; Douglas Lee, Engineer, Division of Electrical Engineering; Andrew Trottar, Engineer, Division of Electrical Engineering. For UL: Howard Hopper, Manager, Corporate Regulatory Services; David Dini, Senior Research Engineer; Arthur Mastromarino, Senior Associate Manager for the Industrial Control Power Distribution Division; Paul Notarian - Senior Staff Engineer, Industrial Control Power Distribution

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in use for several years. An AFCI installed at the circuit breaker level, which is known as a branch/feeder AFCI, protects against downstream and extension cord problems right to the point of the appliance. According to an article by UL Senior Research Engineer David Dini entitled "Arc-Fault Circuit Interrupters," “[The AFCI] functions by recognizing characteristics unique to arcing and de-energizing the circuit when an arc-fault is detected. By doing so, this device will safeguard persons and property by mitigating the unwanted effects of arcing, which can result in a fire." (See Appendix F.)

The following directly addresses some of the misstatements in the materials provided to us by the opponents of AFCIs.

Claim: AFCIs do not pass all of the tests required by UL.

Fact: The basic standard used to evaluate arc-fault protection devices is UL 1699, Arc Fault Circuit Interrupters. The UL 1699 Standard addresses several types of AFCIs, each intended for different applications and/or protection of the branch circuit and extension wiring. The performance requirements for these devices include the arc-fault detection tests as described in Section 56 of that standard. All manufacturers’ AFCI breaker devices pass all of the tests required for branch/feeder AFCIs. Some critics refer to a UL study for the CPSC, which involved research on five different technologies designed to detect and monitor conditions that could lead to residential electrical wiring fires. One of those technologies was AFCIs. However, not all of the 14 experimental tests described in the CPSC’s report were intended for AFCI technology.4

Claim: Arc faults will not ignite structural wooden members of a home [thus,

it is implied, there is no need to protect against arc faults].

Fact: To list the parts of a structure that arc faults do not ignite misses the point. Arc faults can easily ignite insulation and other polymeric materials commonly found within the walls of home. Those materials, in turn, can ignite the wooden structural members.

Claim: AFCIs do not protect against ground faults, high-resistance contacts and glowing contacts.

Fact: The AFCIs currently on the market (circuit breaker branch/feeder types) do protect against ground faults. While these AFCIs may not directly detect some electrical arcing and glowing that can occur at high-resistance contacts and other connection points, the devices respond to the secondary arcing and

Division. In addition, Dr. Joseph Engel, engineer for Eaton/Cutler-Hammer, was consulted to provide further technical clarifications. 4 Dini, David, “Arc Fault Circuit Interrupters,” IAEI News, September/October 2001.

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leakage currents to the ground that result from degraded insulation between conductors in proximity to the incipient fault condition. (The Task Force wishes to note that the ground fault protection afforded by a branch/feeder AFCI does not qualify as a ground fault circuit interrupter or GFCI, which is a device designed to protect against electrocution, unless the device is marked to indicate that it is both an AFCI and a GFCI. Such a combination AFCI/GFCI device is available from one manufacturer at this time.) (See Appendix G)

Claim: AFCIs have a history of nuisance tripping.

Fact: UL1699, Standard for Safety for Arc Fault Circuit Interrupters, addresses nuisance tripping and is far in excess of practical requirements. An AFCI manufacturer told us that an electrician participating in beta testing of an AFCI device complained about nuisance tripping, only to learn that the problem actually was a severe arcing condition involving a garage door opener. In this situation, the AFCI did what it was designed to do and prevented a fire. In a similar incident, an electrician complained about nuisance tripping although inspection revealed that he had incorrectly installed radon fans, and the tripping of the AFCI had served to prevent major fires in several new homes. The UL 1699 Standard currently addresses 15 different unwanted tripping tests.

Claim: AFCIs currently on the market (circuit breaker branch/feeder types) fail to protect against all arcing faults.

Fact: AFCIs currently on the market protect against all unwanted arcs to ground at any point in the circuit, and unwanted arcing in parallel with the load throughout the circuit including the branch circuit extension wiring. These branch/feeder AFCIs are tested to decrease the risk of fire from various types of arcing in accordance with the UL 1699 Safety Standard. These tests include unwanted arcing in series with the electrical load in typical nonmetallic sheathed cable (NM-B plus ground) installed wiring. In practice, this is accomplished by the detection of leakage prior to cable combustion. The tests also include the detection and interruption of the high-energy parallel arcs that are most likely to create a fire hazard. The parallel tests are performed for both NM-B and two-conductor SPT cords. Branch/feeder AFCIs do not detect series arcs in two-conductor extension wiring. These arcs are less hazardous than parallel arcs since they are typically low current and short duration. The subsequent energy content is low. These arcs are essentially indistinguishable from switching-arcs. Other types of electrical arcing (for example, arcs that ignite flammable gasses or vapors) are beyond the capabilities of an AFCI. The currently available branch/feeder AFCIs are expected to eliminate the risk of fire associated with a significant percentage of unwanted arcing conditions. (See Appendices H and I)

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In view of the Task Force’s findings, the prevalence of conflicting claims or misinformation about AFCIs does a disservice to the future safety of American families. Consequently, the Task Force reiterates its support of AFCI technologies and implementation throughout both old and new homes.

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Recommendations The Task Force recommends: 1. The prompt distribution of this report and its appendices, with permission to

cite this report as needed, to the following:

• All federal, state and local regulatory and procurement agencies with authority to adopt or otherwise utilize the National Electrical Code, or with an interest in electrical and fire safety. Special attention should be given to those jurisdictions that have chosen to exclude Section 210-12 from the 2002 National Electrical Code in the most recent cycles.

• The Governors of the States and the Mayors of the largest 100 cities.

• Appropriate Committees of the US Senate and House of Representatives.

• State and local Attorneys General in jurisdictions that utilize the NEC.

• UL, NFPA, IEC and other standards organizations.

• The major fire service organizations.

• National Electrical Manufacturers Association, International Association of Electrical Inspectors, National Electrical Manufacturers Association, International Brotherhood of Electrical Workers, Communications Workers of America, AFL-CIO Office of Worker Safety.

• The producers of AFCIs.

• The organization and individuals on record against AFCIs.

2. A formal, written request that the opponents of AFCIs retract past

misstatements and ensure that all future statements are in keeping with the facts.

3. A meeting of the respective officers of NASFM and the National Association

of Home Builders. 4. Consideration of this matter in light of 101 Wn. App. 845, MENEELY v. S.R.

SMITH, INC. (See Appendix I). We reserve the right to make further recommendations to NASFM in the event that these misrepresentations and misstatements of fact continue, or additional information comes to light.

The National Association of State Fire Marshals The National Association of State Fire Marshals (NASFM) represents the most senior fire official of each of the 50 United States and District of Columbia. State Fire Marshals' responsibilities vary from state to state, but Marshals tend to be responsible for fire safety code adoption and enforcement, fire and arson investigation, fire incident data reporting and analysis, public education and advising Governors and State Legislatures on fire protection. Some State Fire Marshals are responsible for fire fighter training, hazardous materials incident responses, wildland fires and the regulation of natural gas and other pipelines. Most NASFM members are appointed by Governors or other high-ranking state officials. Some are state police officers. Many are former fire fighters. Some are fire protection engineers, while others are former state legislators, insurance experts and labor union officials. NASFM’s mission is two-fold:

• To protect human life, property and the environment from fire.

• To improve the efficiency and effectiveness of State Fire Marshals' operations.

NASFM is a 501(c)6 not-for-profit corporation. NASFM's membership meets annually, elects a Board of Directors and Officers and is consulted whenever possible on crucial matters. The members are the ultimate authority in the organization.

NASFM's Consumer Product Fire Safety Task Force Most fire deaths and injuries occur in the home. Consumer carelessness is a significant factor. Consumer safety education is critical but imprecise and unreliable. Therefore, consumer products for use in the home must be made as safe as possible and anticipate the probability of human error. In pursuit of fire safety, products should not harm people in other ways. NASFM's Consumer Product Fire Safety Task Force addresses all ignition sources and fuels commonly found in the home. The Task Force focuses on priorities defined by fire incident data and on emerging trends in product design and manufacturing. The Task Force may recommend new methods and standards, as well as legislative, regulatory or market-oriented incentives to encourage safer products.

Structure Fires in One- and Two-Family Dwellings

in which the Form of Heat of Ignition was the Heat from Electrical Equipment Arcing or Overloaded

or Improperly Operating Electrical Equipment, by Area of Origin

1994-1998 Annual Averages Direct Civilian Civilian Property Damage Area of Origin Fires Deaths Injuries (in Millions)

Kitchen 15,900 (21.7%) 95 (16.0%) 479 (21.3%) $144.2 (13.8%)Bedroom 11,200 (15.2%) 131 (22.1%) 597 (26.6%) $198.6 (18.9%)Laundry room or area 6,600 (9.0%) 24 (4.0%) 130 (5.8%) $59.3 (5.7%)Living room, family room

or den 6,200 (8.5%) 141 (23.9%) 351 (15.6%) $133.0 (12.7%)

Attic or ceiling/roof assembly or concealed space

4,600 (6.3%) 18 (3.0%) 60 (2.7%) $82.5 (7.9%)

Crawl space or substructure space

4,000 (5.5%) 24 (4.0%) 88 (3.9%) $55.7 (5.3%)

Heating equipment room 3,200 (4.3%) 7 (1.1%) 63 (2.8%) $24.0 (2.3%)Garage* 2,900 (4.0%) 12 (2.0%) 75 (3.4%) $80.0 (7.6%)Wall assembly or

concealed space 2,400 (3.2%) 13 (2.2%) 47 (2.1%) $37.1 (3.5%)

Lavatory 2,200 (3.1%) 15 (2.6%) 40 (1.8%) $24.2 (2.3%)Exterior wall surface 2,100 (2.8%) 3 (0.6%) 21 (0.9%) $17.0 (1.6%)Ceiling/floor assembly or

concealed space 1,200 (1.7%) 18 (3.1%) 22 (1.0%) $27.9 (2.7%)

Closet 1,200 (1.6%) 3 (0.4%) 25 (1.1%) $17.2 (1.6%)Supply storage room or

area 1,000 (1.3%) 2 (0.3%) 16 (0.7%) $14.6 (1.4%)

Hallway, corridor or mall 900 (1.2%) 8 (1.3%) 18 (0.8%) $9.1 (0.9%)Dining room 900 (1.2%) 18 (3.0%) 31 (1.4%) $13.4 (1.3%)Unclassified structural

area 900 (1.2%) 11 (1.9%) 25 (1.1%) $16.1 (1.5%)

Unclassified area of origin

700 (1.0%) 7 (1.2%) 23 (1.0%) $12.1 (1.2%)

Unclassified storage area 600 (0.8%) 3 (0.6%) 19 (0.8%) $10.2 (1.0%)Exterior balcony or open

porch 500 (0.7%) 4 (0.7%) 13 (0.6%) $8.5 (0.8%)

Exterior roof surface 400 (0.5%) 0 (0.0%) 3 (0.1%) $3.1 (0.3%)

Source: Custom tables on structure fires involving electrical arcing or improper operating electrical equipment in one- and two-family dwellings, prepared by Marty Ahrens, NFPA, Quincy, MA, March 2001.

* This does not include dwelling garages coded as a specific fixed property use.

Source: Custom tables on structure fires involving electrical arcing or improper operating electrical equipment in one- and two-family dwellings, prepared by Marty Ahrens, NFPA, Quincy, MA, March 2001.

Structure Fires in One- and Two-Family Dwellings in which the Form of Heat of Ignition was the

Heat from Electrical Equipment Arcing or Overloaded or Improperly Operating Electrical Equipment,

by Area of Origin 1998-1998 Annual Averages

(Continued) Direct Civilian Civilian Property Damage Area of Origin Fires Deaths Injuries (in Millions)

Other service or equipment area

1,100 (1.6%) 1 (0.1%) 17 (0.7%) $10.5 (1.0%)

Other function room or area

800 (1.1%) 9 (1.5%) 29 (1.3%) $14.3 (1.4%)

Other means of egress

500 (0.7%) 16 (2.7%) 13 (0.6%) $10.6 (1.0%)

Other known area of origin

1,300 (1.8%) 9 (1.5%) 42 (1.9%) $24.7 (2.4%)

Total 73,500 (100.0%) 591 (100.0%) 2,247 (100.0%) $1,047.9 (100.0%) This table shows structure fires (incident type 11) in one- and two-family dwellings (fixed property use 410-419) in which the form of heat of ignition was one of the following:

21-Water caused short circuit arc; 22-Short circuit arc from mechanical damage; 23-Short circuit arc from defective or worn insulation; 24-Unspecified short circuit arc; 25-Arc from faulty contact, loose connection or broken conductor; 26-Arc or spark form operating equipment or switch; 27-Heat from overloaded equipment, including wiring and motors; 28-Fluorescent light ballast; 29-Unclassified electrical equipment arcing or overloaded; 20-Unknown-type electrical equipment arcing or overloaded; or 57-Heat from improperly operating electrical equipment.

These are fires reported to U.S. municipal fire departments and so exclude fires reported only to Federal or state agencies or industrial fire brigades. Fires are rounded to the nearest hundred, civilian deaths and civilian injuries are expressed to the nearest one and property damage is rounded to the nearest hundred thousand dollars. Sums may not equal totals due to rounding errors. Property damage figures have not been adjusted for inflation. A proportional share of fires in which the form of heat of ignition was unknown has been included in this table. Fires in which the area of origin was unknown were allocated proportionally among fires with known area of origin. Source: National estimates based on NFIRS and NFPA survey.

Table 1. Structure Fires in One- and Two-Family Dwellings

in which the Form of Heat of Ignition was the Heat from Electrical Equipment Arcing

Including Unclassified or Unknown-Type Arcing or Overload, by Area of Origin

1994-1998 Annual Averages Direct Civilian Civilian Property Damage Area of Origin Fires Deaths Injuries (in Millions) Kitchen 12,800 (21.1%) 82 (16.7%) 364 (20.0%) $118.1 (13.1%)Bedroom 9,500 (15.7%) 112 (22.8%) 499 (27.4%) $170.9 (18.9%)Living room, family room

or den 5,400 (8.8%) 121 (24.6%) 286 (15.7%) $116.3 (12.9%)

Laundry room or area 4,500 (7.4%) 23 (4.7%) 90 (5.0%) $45.2 (5.0%)Attic or ceiling/roof

assembly or concealed space

4,100 (6.7%) 12 (2.4%) 50 (2.7%) $73.9 (8.2%)

Crawl space or substructure space

3,400 (5.5%) 15 (3.1%) 74 (4.1%) $50.4 (5.6%)

Garage or vehicle storage area*

2,500 (4.1%) 11 (2.2%) 65 (3.6%) $70.3 (7.8%)

Heating equipment room 2,500 (4.0%) 5 (1.1%) 47 (2.6%) $19.6 (2.2%)Wall assembly or concealed

space 2,200 (3.6%) 10 (2.0%) 41 (2.2%) $32.8 (3.6%)

Exterior wall surface 1,900 (3.2%) 3 (0.5%) 21 (1.1%) $16.0 (1.8%)Lavatory 1,900 (3.1%) 7 (1.4%) 32 (1.8%) $20.9 (2.3%)Ceiling/floor assembly or

concealed space 1,100 (1.8%) 16 (3.2%) 20 (1.1%) $25.1 (2.8%)

Closet 1,000 (1.7%) 3 (0.5%) 25 (1.4%) $16.0 (1.8%)Supply storage room or area 800 (1.3%) 2 (0.3%) 13 (0.7%) $12.6 (1.4%)Unclassified structural area 800 (1.3%) 4 (0.9%) 22 (1.2%) $14.1 (1.6%)Dining room 800 (1.3%) 16 (3.3%) 28 (1.5%) $11.6 (1.3%)Hallway, corridor or mall 800 (1.3%) 8 (1.6%) 14 (0.8%) $8.1 (0.9%)Unclassified area of origin 600 (1.0%) 6 (1.2%) 16 (0.9%) $11.0 (1.2%)Other service or equipment

area 900 (1.5%) 0 (0.0%) 13 (0.7%) $9.2 (1.0%)

Other structural area 800 (1.3%) 4 (0.9%) 14 (0.8%) $10.2 (1.1%) * This does not include dwelling garages coded as a specific fixed property use.



Including Unclassified or Unknown-Type Arcing or Overload, by Area of Origin

1994-1998 Annual Averages (Continued)

Direct Civilian Civilian Property Damage Area of Origin Fires Deaths Injuries (in Millions)

Other storage area 700 (1.2%) 4 (0.8%) 25 (1.4%) $13.2 (1.5%)Other function room or area 700 (1.1%) 7 (1.4%) 26 (1.4%) $12.3 (1.4%)Other known area

1,300 (2.2%) 22 (4.5%) 39 (2.1%) $26.7 (3.0%)

Total 60,900 (100.0%) 490 (100.0%) 1,822 (100.0%) $904.6 (100.0%) This table shows structure fires (incident type 11) in one- and two-family dwellings and manufactured housing (fixed property use 410-419) in which the form of heat of ignition was one of the following:

21-Water caused short circuit arc; 22-Short circuit arc from mechanical damage; 23-Short circuit arc from defective or worn insulation; 24-Unspecified short circuit arc; 25-Arc from faulty contact, loose connection or broken conductor; 26-Arc or spark form operating equipment or switch; 29-Unclassified electrical equipment arcing or overloaded; 20-Unknown-type electrical equipment arcing or overloaded; or

These are fires reported to U.S. municipal fire departments and so exclude fires reported only to Federal or state agencies or industrial fire brigades. Fires are rounded to the nearest hundred, civilian deaths and civilian injuries are expressed to the nearest one and property damage is rounded to the nearest hundred thousand dollars. Sums may not equal totals due to rounding errors. Property damage figures have not been adjusted for inflation. A proportional share of fires in which the form of heat of ignition was unknown has been included in this table. Electrical equipment arcing fires in which the area of origin was unknown were allocated proportionally among fires with known area of origin. Source: National estimates based on NFIRS and NFPA survey.



Excluding Unclassified or Unknown-Type Arcing or Overload, by Area of Origin

1994-1998 Annual Averages

Direct Civilian Civilian Property Damage Area of Origin Fires Deaths Injuries (in Millions) Kitchen 9,000 (18.4%) 52 (15.1%) 193 (14.1%) $88.0 (12.3%)Bedroom 8,000 (16.4%) 70 (20.2%) 415 (30.3%) $135.4 (19.0%)Living room, family room or

den 4,600 (9.4%) 97 (28.0%) 232 (16.9%) $94.4 (13.2%)

Attic or ceiling/roof assembly or concealed space

3,500 (7.2%) 9 (2.5%) 44 (3.2%) $61.1 (8.6%)

Laundry room or area 3,400 (7.0%) 19 (5.4%) 65 (4.7%) $35.6 (5.0%)Crawl space or substructure

space* 2,900 (5.9%) 10 (2.8%) 60 (4.4%) $42.2 (5.9%)

Garage or vehicle storage area 2,000 (4.2%) 6 (1.6%) 49 (3.6%) $54.8 (7.7%)

Heating equipment room 1,900 (4.0%) 5 (1.4%) 39 (2.8%) $15.5 (2.2%)Wall assembly or concealed

space 1,900 (3.9%) 4 (1.3%) 28 (2.0%) $26.8 (3.8%)

Exterior wall surface 1,700 (3.4%) 2 (0.5%) 18 (1.3%) $13.1 (1.8%)

Lavatory 1,600 (3.2%) 5 (1.5%) 26 (1.9%) $16.3 (2.3%)Ceiling/floor assembly or

concealed space 900 (1.9%) 15 (4.4%) 16 (1.2%) $20.4 (2.9%)

Closet 800 (1.7%) 2 (0.5%) 20 (1.5%) $12.3 (1.7%)

Supply storage room or area 700 (1.3%) 0 (0.0%) 10 (0.7%) $10.0 (1.4%)Dining room 600 (1.3%) 13 (3.9%) 23 (1.7%) $9.8 (1.4%)Hallway, corridor or mall 600 (1.3%) 3 (1.0%) 13 (0.9%) $6.8 (1.0%)

Unclassified structural area 600 (1.2%) 1 (0.4%) 16 (1.2%) $9.6 (1.3%)Other service or equipment

area 700 (1.5%) 0 (0.0%) 12 (0.8%) $7.5 (0.0%)

Other structural area 700 (1.3%) 3 (1.0%) 13 (0.9%) $8.3 (1.2%)

Other storage area 600 (1.2%) 4 (1.2%) 22 (1.6%) $10.7 (0.0%)Other function area 500 (1.0%) 2 (0.5%) 16 (1.2%) $8.6 (0.0%)Other known area

1,500 (3.1%) 24 (6.9%) 40 (2.9%) $26.6 (3.7%)

Total 48,800 (100.0%) 345 (100.0%) 1,371 (100.0%) $713.8 (100.0%)

* This does not include dwelling garages coded as a specific fixed property use.



Excluding Unclassified or Unknown-Type Arcing or Overload, by Area of Origin

1994-1998 Annual Averages (Continued)

This table shows structure fires (incident type 11) in one- and two-family dwellings, including manufactured housing (fixed property use 410-419) in which the form of heat of ignition was one of the following:

21-Water caused short circuit arc; 22-Short circuit arc from mechanical damage; 23-Short circuit arc from defective or worn insulation; 24-Unspecified short circuit arc; 25-Arc from faulty contact, loose connection or broken conductor; 26-Arc or spark form operating equipment or switch;

These are fires reported to U.S. municipal fire departments and so exclude fires reported only to Federal or state agencies or industrial fire brigades. Fires are rounded to the nearest hundred, civilian deaths and civilian injuries are expressed to the nearest one and property damage is rounded to the nearest hundred thousand dollars. Sums may not equal totals due to rounding errors. Property damage figures have not been adjusted for inflation. A proportional share of fires in which the form of heat of ignition was unknown has been included in this table. Electrical equipment fires in which the area of origin was unknown were allocated proportionally among fires with known area of origin. Source: National estimates based on NFIRS and NFPA survey.


by Form of Heat of Ignition 1994-1998 Annual Averages

Direct Civilian Civilian Property Damage Code Form of Heat Fires Deaths Injuries (in Millions) 10 Heat from unknown-

type fuel-fired object 1,300 (0.4%) 8 (0.3%) 47 (0.4%) $14.1 (0.4%)

11 Spark, ember or flame escaping from gas-fueled equipment

5,600 (1.8%) 53 (1.9%) 271 (2.2%) $65.0 (1.9%)

12 Heat from gas-fueled equipment

28,600 (9.3%) 249 (8.9%) 1,283 (10.4%) $210.5 (6.0%)

13 Spark, ember or flame escaping from liquid-fueled equipment

1,500 (0.5%) 20 (0.7%) 78 (0.6%) $22.7 (0.7%)

14 Heat from liquid-fueled equipment

4,900 (1.6%) 75 (2.7%) 225 (1.8%) $46.1 (1.3%)

15 Spark, ember of flame escaping from solid-fueled equipment

8,900 (2.9%) 38 (1.4%) 81 (0.7%) $64.6 (1.9%)

16 Heat from solid-fueled equipment

19,600 (6.4%) 68 (2.4%) 186 (1.5%) $136.6 (3.9%)

17 Spark, ember or flame escaping from equipment with unknown-type fuel

600 (0.2%) 6 (0.2%) 10 (0.1%) $12.1 (0.3%)

18 Heat from equipment with unknown-type fuel

1,400 (0.5%) 7 (0.2%) 40 (0.3%) $14.5 (0.4%)

19 Heat from unclassified fuel-fired or fuel-powered object

1,100 (0.4%) 10 (0.3%) 37 (0.3%) $18.7 (0.5%)

20 Unknown-type electrical equipment arc or overload

8,000 (2.6%) 100 (3.6%) 290 (2.4%) $132.6 (3.8%)

21 Water-caused short circuit arc

1,300 (0.4%) 3 (0.1%) 19 (0.2%) $8.3 (0.2%)

22 Short circuit arc from mechanical damage

4,200 (1.4%) 18 (0.6%) 99 (0.8%) $50.0 (1.4%)

23 Short circuit arc from defective or worn insulation

10,700 (3.5%) 77 (2.7%) 263 (2.1%) $132.1 (3.8%)

24 Unspecified short circuit arc

27,600 (9.0%) 217 (7.7%) 801 (6.5%) $458.3 (13.2%)

Structure Fires in One- and Two-Family Dwellings by Form of Heat of Ignition 1994-1998 Annual Averages

Direct Civilian Civilian Property Damage Code Form of Heat Fires Deaths Injuries (in Millions) 25 Arc from faulty contact 3,200 (1.0%) 14 (0.5%) 91 (0.7%) $39.4 (1.1%)26 Arc or spark from

operating equipment or switch

1,800 (0.6%) 16 (0.6%) 97 (0.8%) $25.7 (0.7%)

27 Heat from overloaded equipment

7,000 (2.3%) 68 (2.4%) 249 (2.0%) $90.5 (2.6%)

28 Fluorescent light ballast 400 (0.1%) 2 (0.1%) 5 (0.0%) $4.7 (0.1%)29 Unclassified electrical

equipment arc or overload

4,000 (1.3%) 45 (1.6%) 162 (1.3%) $58.2 (1.7%)

30 Heat from unknown-type smoking material

1,100 (0.4%) 58 (2.1%) 66 (0.5%) $18.5 (0.5%)

31 Cigarette 13,900 (4.5%) 565 (20.1%) 1,128 (9.2%) $177.0 (5.1%)32 Cigar 200 (0.0%) 7 (0.3%) 11 (0.1%) $2.5 (0.1%)33 Pipe 100 (0.0%) 15 (0.5%) 5 (0.0%) $1.4 (0.0%)39 Heat from unclassified

smoking material 700 (0.2%) 11 (0.4%) 32 (0.3%) $9.9 (0.3%)

40 Heat from unknown-type open flame or spark

6,100 (2.0%) 85 (3.0%) 257 (2.1%) $97.2 (2.8%)

41 Cutting torch 600 (0.2%) 1 (0.0%) 16 (0.1%) $7.6 (0.2%)42 Welding torch 700 (0.2%) 2 (0.1%) 26 (0.2%) $9.8 (0.3%)43 Torch, not cutting or

welding 2,100 (0.7%) 8 (0.3%) 67 (0.5%) $28.1 (0.8%)

44 Candle 7,500 (2.5%) 92 (3.3%) 756 (6.1%) $111.7 (3.2%)45 Match 14,700 (4.8%) 145 (5.2%) 778 (6.3%) $163.9 (4.7%)46 Lighter 8,600 (2.8%) 172 (6.1%) 1,031 (8.4%) $118.0 (3.4%)47 Open fire 5,900 (1.9%) 32 (1.1%) 143 (1.2%) $45.2 (1.3%)48 Backfire from internal

combustion engine 200 (0.1%) 0 (0.0%) 13 (0.1%) $4.5 (0.1%)

49 Heat from unclassified open flame or spark

4,100 (1.3%) 41 (1.5%) 166 (1.3%) $46.9 (1.3%)

50 Heat from unknown-type hot object

3,600 (1.2%) 39 (1.4%) 123 (1.0%) $41.6 (1.2%)

51 Heat or spark from friction

900 (0.3%) 1 (0.0%) 14 (0.1%) $5.1 (0.1%)


by Form of Heat of Ignition 1994-1998 Annual Averages

Direct Civilian Civilian Property Damage Code Form of Heat Fires Deaths Injuries (in Millions) 52 Molten or hot material 600 (0.2%) 3 (0.1%) 27 (0.2%) $5.3 (0.2%)53 Hot ember or ash 6,800 (2.2%) 27 (1.0%) 123 (1.0%) $76.9 (2.2%)54 Electric lamp 4,000 (1.3%) 23 (0.8%) 133 (1.1%) $56.2 (1.6%)55 Rekindle or reignition 3,900 (1.3%) 1 (0.0%) 4 (0.0%) $26.9 (0.8%)56 Heat from properly

operating electrical equipment

38,500 (12.6%) 189 (6.7%) 2,148 (17.5%) $234.9 (6.7%)

57 Heat from improperly operating electrical equipment

5,200 (1.7%) 31 (1.1%) 171 (1.4%) $48.1 (1.4%)

59 Heat from unclassified hot object

3,300 (1.1%) 26 (0.9%) 123 (1.0%) $37.0 (1.1%)

60 Heat from unknown-type explosive or fireworks

100 (0.0%) 0 (0.0%) 3 (0.0%) $1.0 (0.0%)

61 Explosive 100 (0.0%) 0 (0.0%) 8 (0.1%) $1.3 (0.0%)62 Blasting agent 0 (0.0%) 0 (0.0%) 0 (0.0%) $0.2 (0.0%)63 Fireworks 800 (0.3%) 2 (0.1%) 25 (0.2%) $8.7 (0.2%)64 Party cap, party popper 0 (0.0%) 0 (0.0%) 0 (0.0%) $2.2 (0.1%)65 Model rocket, not

amateur rocketry 0 (0.0%) 1 (0.0%) 2 (0.0%) $0.9 (0.0%)

66 Incendiary device 1,900 (0.6%) 12 (0.4%) 62 (0.5%) $27.7 (0.8%)69 Heat from unclassified

explosive or fireworks

100 (0.0%) 1 (0.0%) 1 (0.0%) $2.2 (0.1%)

70 Heat from unknown-type natural source

100 (0.0%) 0 (0.0%) 1 (0.0%) $1.0 (0.0%)

71 Sun's heat 200 (0.1%) 0 (0.0%) 1 (0.0%) $1.5 (0.0%)72 Spontaneous ignition or

chemical reaction 2,100 (0.7%) 3 (0.1%) 51 (0.4%) $35.9 (1.0%)

73 Lightning 5,700 (1.9%) 12 (0.4%) 52 (0.4%) $122.9 (3.5%)74 Static discharge 100 (0.0%) 0 (0.0%) 3 (0.0%) $0.6 (0.0%)79 Heat from unclassified

natural source 100 (0.0%) 0 (0.0%) 0 (0.0%) $0.7 (0.0%)

80 Unknown-type heat spreading from another hostile fire

700 (0.2%) 1 (0.0%) 10 (0.1%) $15.5 (0.4%)

Structure Fires in One- and Two-Family Dwellings by Form of Heat of Ignition 1994-1998 Annual Averages

Direct Civilian Civilian Property Damage Code Form of Heat Fires Deaths Injuries (in Millions) 81 Heat from direct flame

or convection current 5,900 (1.9%) 24 (0.8%) 88 (0.7%) $81.9 (2.4%)

82 Radiated heat 6,400 (2.1%) 17 (0.6%) 71 (0.6%) $53.2 (1.5%)83 Heat from flying brand,

ember or spark 700 (0.2%) 2 (0.1%) 4 (0.0%) $13.0 (0.4%)

84 Conducted heat 900 (0.3%) 2 (0.1%) 28 (0.2%) $8.7 (0.3%)89 Unclassified heat

spreading from another hostile fire

600 (0.2%) 3 (0.1%) 7 (0.1%) $8.1 (0.2%)

97 Multiple forms of heat 1,100 (0.3%) 9 (0.3%) 32 (0.3%) $34.9 (1.0%)99 Unclassified form of

heat

4,600 (1.5%) 55 (1.9%) 144 (1.2%) $80.1 (2.3%)

Total 306,800 (100.0%) 2,810 (100.0%) 12,288 (100.0%) $3,481.2 (100.0%) This table shows the form of heat of ignition in structure fires (incident type 11) in one- and two-family dwellings, including manufactured housing (fixed property use 410-419) These are fires reported to U.S. municipal fire departments and so exclude fires reported only to Federal or state agencies or industrial fire brigades. Fires are rounded to the nearest hundred, civilian deaths and civilian injuries are expressed to the nearest one and property damage is rounded to the nearest hundred thousand dollars. Sums may not equal totals due to rounding errors. Property damage figures have not been adjusted for inflation. A proportional share of fires in which the form of heat of ignition was unknown has been included in this table. Source: National estimates based on NFIRS and NFPA survey.

Appendix: How National Estimates Statistics Are Calculated

Estimates are made using the National Fire Incident Reporting System (NFIRS) of the Federal Emergency Management Agency's (FEMA's) United States Fire Administration (USFA), supplemented by the annual stratified random-sample survey of fire experience conducted by the National Fire Protection Association (NFPA), which is used for calibration. Databases Used NFIRS provides annual computerized databases of fire incidents, with data classified according to a standard format based on the NFPA 901 Standard. Roughly three-fourths of all states have NFIRS coordinators, who receive fire incident data from participating fire departments and combine the data into a state database. These data are then transmitted to FEMA/USFA. Participation by the states, and by local fire departments within participating states, is voluntary. NFIRS captures roughly one-third to one-half of all U.S. fires each year. More than one-third of all U.S. fire departments are listed as participants in NFIRS, although not all of these departments provide data every year. The strength of NFIRS is that it provides the most detailed incident information of any national database not limited to large fires. NFIRS is the only database capable of addressing national patterns for fires of all sizes by specific property use and specific fire cause. (The NFPA survey separates fewer than 20 of the hundreds of property use categories defined by NFPA 901 and solicits no cause-related information except for incendiary and suspicious fires.) NFIRS also captures information on the avenues and extent of flame spread and smoke spread and on the performance of detectors and sprinklers. The NFPA survey is based on a stratified random sample of roughly 3,000 U.S. fire departments (or just over one of every ten fire departments in the country). The survey includes the following information: (1) the total number of fire incidents, civilian deaths, and civilian injuries, and the total estimated property damage (in dollars), for each of the major property use classes defined by the NFPA 901 Standard; (2) the number of on-duty firefighter injuries, by type of duty and nature of illness; and (3) information on the type of community protected (e.g., county versus township versus city) and the size of the population protected, which is used in the statistical formula for projecting national totals from sample results. The NFPA survey begins with the NFPA Fire Service Inventory, a computerized file of about 30,000 U.S. fire departments, which is the most complete and thoroughly validated such listing in existence. The survey is stratified by size of population protected to reduce the uncertainty of the final estimate. Small rural communities protect fewer people per department and are less likely to respond to the survey, so a large number must be surveyed to obtain an adequate sample of those departments. (NFPA also makes follow-up calls to a sample of the smaller fire departments that do not respond, to confirm that those that did respond are truly representative of fire departments their size.) On the other hand, large city departments are so few in number and protect such a large proportion of the total U.S. population that it makes sense to survey all of them. Most respond, resulting in excellent precision for their part of the final estimate.

Projecting NFIRS to National Estimates To project NFIRS results to national estimates, one needs at least an estimate of the NFIRS fires as a fraction of the total so that the fraction can be inverted and used as a multiplier or scaling ratio to generate national estimates from NFIRS data. But NFIRS is a sample from a universe whose size cannot be inferred from NFIRS alone. Also, participation rates in NFIRS are not necessarily uniform across regions and sizes of community, both of which are factors correlated with frequency and severity of fires. This means NFIRS may be susceptible to systematic biases. No one at present can quantify the size of these deviations from the ideal, representative sample, so no one can say with confidence that they are or are not serious problems. But there is enough reason for concern so that a second database - the NFPA survey - is needed to project NFIRS to national estimates and to project different parts of NFIRS separately. This multiple calibration approach makes use of the annual NFPA survey where its statistical design advantages are strongest. There are separate projection formulas for four major property classes (residential structures, non-residential structures, vehicles, and other) and for each measure of fire severity (fire incidents, civilian deaths, and civilian injuries, and direct property damage). For example, the scaling ratio for 1998 civilian deaths in residential structures is equal to the total number of 1998 civilian deaths in residential structure fires reported to fire departments, according to the NFPA survey (3,250), divided by the total number of 1998 civilian deaths in residential structure fires reported to NFIRS (1,224). Therefore, the scaling ratio is 3,250/1,224 = 2.66. The scaling ratios for civilian deaths and injuries and direct property damage are often significantly different from those for fire incidents. Except for fire service injuries, average severity per fire is generally higher for NFIRS than for the NFPA survey. Use of different scaling ratios for each measure of severity is equivalent to assuming that these differences are due either to NFIRS under-reporting of small fires, resulting in a higher-than-actual loss-per-fire ratio, or possible biases in the NFIRS sample representation by region or size of community, resulting in severity-per- fire ratios characteristic only of the oversampled regions or community sizes. Note that this approach also means that the NFPA survey results for detailed property-use classes (e.g., fires in storage structures) may not match the national estimates of the same value. Calculating National Estimates of Particular Types of Fires Most analyses of interest involve the calculation of the estimated number of fires not only within a particular occupancy but also of a particular type. The types that are mostly frequently of interest are those defined by some ignition-cause characteristic. The six cause-related characteristics most commonly used to describe fires are: form of the heat that caused the ignition, equipment involved in ignition, form or type of material first ignited, the ignition factor that brought heat source and ignited material together, and area of origin. Other characteristics of interest are victim characteristics, such as ages of persons killed or injured in fire. For any characteristic of interest in NFIRS, some reported fires have that characteristic unknown or not reported. If the unknowns are not taken into account, then the propensity to

report or not report a characteristic may influence the results far more than the actual patterns on that characteristic. For example, suppose the number of fires remained the same for several consecutive years, but the percentage of fires with cause unreported steadily declined over those years. If the unknown-cause fires were ignored, it would appear as if fires due to every specific cause increased over time while total fires remained unchanged. This, of course, does not make sense. Consequently, most national estimates analyses allocate unknowns. This is done by using scaling ratios defined by NFPA survey estimates of totals divided by only those NFIRS fires for which the dimension in question was known and reported. This approach is equivalent to assuming that the fires with unreported characteristics, if known, would show the same proportions as the fires with known characteristics. For example, it assumes that the fires with unknown ignition factor contain the same relative shares of child-playing fires, incendiary-cause fires, short circuit fires, and so forth, as are found in the fires where ignition factor was reported. Rounding Errors The possibility of rounding errors exists in all our calculations. One of the notes on each table indicates the extent of rounding for that table, e.g., deaths rounded to the nearest one, fires rounded to the nearest hundred, property damage rounded to the nearest hundred thousand dollars. In rounding to the nearest one, functional values of 0.5 or more are rounded up and functional values less than 0.5 are rounded down. For example, 2.5 would round to 3, and 3.4 would round to 3. In rounding to the nearest one, a stated estimate of 1 could be any number from 0.5 to 1.49, a roughly threefold range. The impact of rounding is greatest when the stated number is small relative to the degree of rounding. As noted, rounding to the nearest one means that stated values of 1 may vary by a factor of three. Similarly, the cumulative impact of rounding error - the potential gap between the estimated total and the sum of the estimated values as rounded - is greatest when there are a large number of values and the total is small relative to the extent of rounding. Suppose a table presented 5-year averages of estimated deaths by item first ignited, all rounded to the nearest one. Suppose there were a total of 30 deaths in the 5 years, so the total average would be 30/5 = 6. In case 1, suppose 10 of the possible items first ignited each accounted for 3 deaths in 5 years. Then there would be 10 entries of 3/5 = 0.6, rounded to 1, and the sum would be 10, compared to the true total of 6. In case 2, suppose 15 of the possible items first ignited each accounted for 2 deaths in 5 years. Then there would be 15 entries of 215 = 0.4, rounded to 0, and the sum would be 0, compared to the true total of 6. Here is another example: Suppose there were an estimate of 7 deaths total in 1992 through 1996. The 5-year average would be 1.4, which would round to 1, the number we would show as the total. Each death would represent a 5-year average of 0.2. If those 7 deaths split as 4 deaths in one category (e.g., smoking) and 3 deaths in a second category (e.g., heating), then we would show 4 x 0.2 = 0.8 deaths per year for smoking and 3

x 0.2 = 0.6 deaths per year for heating. Both would round to 1, there would be two entries of 1, and the sum would be 2, higher than the actual rounded total. If those 7 deaths split as 1 death in each of 7 categories (quite possible since there are 12 major cause categories), then we would show 0.2 in each category, always rounding to 0, and the sum would be 0, lower than the actual rounded total. The more categories there are, the farther apart the sum and total can -- and often do -- get. Note that percentages are calculated from unrounded values, and so it is quite possible to have a percentage entry of up to 100%, even if the rounded number entry is zero.

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15 amp QO Home Depot online $39.97 $39.97 $39.97 Homeline Home Depot online $34.97 $34.97 $34.97 Murray Home Depot online $34.97 N/A N/A

84 IAEI NEWS

t is not often that a new safety device is introduced to protect individuals from thedangers that may be present in residential occupancies. Smoke alarms, carbonmonoxide detectors, and ground-fault circuit interrupters are recognized asessential life saving devices. In 2002, the National Electrical Code (NEC) will

require a new electrical safety device, the arc-fault circuit interrupter (AFCI), foradded protection in certain dwelling unit branch circuits. Currently being incorporatedinto both residential circuit breakers and outlet receptacles, AFCIs incorporate verysophisticated electronics to recognize characteristics unique to arcing, and function tode-energize the circuit when a potentially damaging arc fault is detected.

When devices intended to provide for safety are first introduced, it is not un-usual to find that there are differing viewpoints as to the added benefits these

safety devices may or may not provide. These differences in viewpoints oftencarry over into the development of proposals for revision of codes and stan-

dards. Proposals to adopt required use of the new AFCIs have raised suchdifferences in viewpoints. Various concerns have been expressed which ifleft unanswered, could give a false impression about the ability of AFCIs to

properly perform their intended function and provide the added safetybenefit for which they were designed. The following are responses to

specific concerns to help clarify the record.

Concern — NEC CMP-2 accepted adoption of this newrequirement based on inaccurate and misleading documen-

tation submitted by the manufacturers of these devices.Several documents were submitted to CMP-2 in sub-

stantiating the various proposals for the NEC Section210-12 requirement for arc-fault protection. Included was

a March 15, 1996, UL Report of Research on Arc-Fault DetectionCircuit Breakers. This extensive work included development

of arc-current versus time characteristics for ignition ofmaterials by arcing faults, unwanted operation andoperation inhibition considerations, and effects ofbuilding wire impedance. The results of UL’s research

The results of UL’s research were used as a basis for the developmentof the Standard for Arc-Fault Circuit Interrupters, UL 1699.

I

by David Dini

SEPTEMBER/OCTOBER 2001 85

ARC-FAULT CIRCUIT INTERRUPTERS

Figure 1. 210.12 Arc-Fault Circuit Interrupter Protection

To dwelingunit bedrooms

Typical dweling unit bedroom

Circuit run toAFCI device

Dwellingunit

panelboard

All branch circuits that supply125-volt, 15-and 20-ampere

Outlets installed indwelling unit bedrooms shall be

protected by anArc-Fault Circuit Interrupter(s).

were used as a basis for the development of the Standardfor Arc-Fault Circuit Interrupters, UL 1699. Proponentsprovided residential fire data provided by a major homeinsurance company that showed evidence of electricalarcing being common with many residential electrical fires.

Concern — At a recent meeting of NEC CMP-2, ULmade a presentation that demonstrated that the AFCIdevices would not detect all arcing faults. The ULrepresentative described the basic technical problemswith the device. It will not be able to detect all arcsthat may produce a fire. Asked if the device willdetect all arcs between the breaker and the first outlet,the answer was no. The answer was the same fordetecting arcs in an outlet, in the cord from the outletto the appliance, and the appliance itself. Asked whatthe percentage of arcs may be detected, the answerwas they do not know.

The UL 1699 Standard describes several differenttypes of AFCIs for different applications and areas ofprotection. For example, a branch/feeder type AFCI is

intended to be installed at the origin of the branch circuitto protect the branch circuit wiring against the unwantedeffects of arcing faults. There are also outlet branch-circuit AFCIs of the receptacle type that have been testedto protect the branch circuit wiring. AFCIs are tested tomitigate the effects of various types of arcing, includingboth contact and non-contact arcing, and series andparallel arcing. Surgical cotton is used as the fire indicatorin many of the tests. Some electrical arcing, such as thatwhich might ignite flammable gases or vapors, is beyondthe capabilities of an AFCI.

Concern — The UL Standard used to manufacture andtest this product has only been in existence a shorttime. It was rushed through development only to satisfythe needs of the manufacturers as it related to theirspecific product.

UL has been working with all interested partiesinvolving AFCIs since 1994 to develop the require-ments for UL 1699. The results of thousands of hoursof research, development, and technical meetings

86 IAEI NEWS

ARC-FAULT CIRCUIT INTERRUPTERS

culminated in the publishing of the UL 1699 Standardfor AFCIs in February of 1999. Prior to publishing UL 1699,UL classified several AFCIs involved in beta site testing.

Concern — Unfortunately, the devices can pass onlyfour of the tests, not the full 14 tests needed for thisproduct to protect residential occupancies as outlinedin a UL study for the U.S. Consumer Product SafetyCommission (CPSC).

The CPSC study referenced, “Technology for Detectingand Monitoring Conditions that Could Cause ElectricalWiring System Fires,” involved an in-depth study of fivedifferent technologies to detect and monitor precur-sory conditions that could lead to fires in residentialelectrical wiring systems. Arc-fault detection technologywas only one of the five technologies being studied.Not all of the 14 experimental tests described in thatreport were intended for arc-fault technology. Forexample, electrical ignition most frequently occursas the result of Joule heating or electrical arcing. Itshould not be expected that those ignition scenariosrepresenting Joule (I2R) heating would necessarily beprevented by an AFCI. The UL 1699 Standard currentlyaddresses four different types of arcing tests with dif-ferent types of wires and insulation cuts, 15 differentunwanted tripping tests, 9 different operation inhibi-tion tests, and 14 additional tests representing envi-ronmental conditioning, overloads, short circuits, andmechanical testing, among others.

Concern — The tests from the UL Standard only useNM cable with a grounding conductor, not the com-mon single conductor concealed wiring method (knoband tube) installed in older dwellings. Most of the wiringfires included in the fire studies used by the proponentsto support the requirement for AFCIs have occurred inolder dwellings.

The tests in UL 1699 for use with NM cable require NMcable with ground, as the NEC requirement in Section

210-12 would only apply to new construction wherebranch-circuit wiring with an equipment ground wouldbe required. The tests in UL 1699 that use SPT flexible

cord are conducted on cords without ground.Additional requirements are being proposed forUL 1699 for some types of AFCIs to be testedwith NM cable without ground, as may be foundin older homes.

Concern — The claims that annual propertylosses are more than $1.5 billion are unsub-stantiated.

According to the 1998 Residential Fire LossEstimates published by the CPSC and avail-able on their web site (www.cpsc.gov), totalresidential electrical equipment resulted in$1.68 billion in fire losses in 1998, the latestyear available. From this, electrical distribu-tion equipment resulted in $680 million in

losses. AFCIs are most effective in preventing fireswithin the electrical distribution system. This CPSCdata came from the U.S. Fire Administration’s (USFA)National Fire Incident Reporting System (NFIRS) andthe National Fire Protection Association (NFPA).

Concern — AFCIs are an unreliable product thatshould not be counted upon for public safety. Thecurrent requirements for smoke alarms are muchmore reliable and cost-effective in protecting occupantsfrom residential fires.

To compare AFCIs to smoke alarms would not becorrect. A smoke alarm is a signaling device intendedto warn people of a fire hazard that has already devel-oped. A smoke alarm is intended to protect people,and not necessarily property. An AFCI is not a signalingdevice; however, it is a safety protective device. It func-tions by recognizing characteristics unique to arcingand de-energizing the circuit when an arc-fault is detected.By doing so, this device will safeguard persons andproperty by mitigating the unwanted effects of arcing,which can result in a fire.

Photographs and drawings provided courtesy of the IAEI educa-tion department.

David Dini is a senior research engineer at Un-derwriters Laboratories Inc.’s (UL) Northbrook,Ill., office. As an electrical engineer with morethan 25 years of experience in product safetytesting, Dini is extensively involved in newtechnology research. Dini is a registered pro-fessional engineer (PE) in the state of Illinois; a

member of the National Electrical Code (NEC) making panels1 and 5; a senior member of IEEE; and an InternationalAssociation of Electrical Inspectors’ associate member.

According to the 1998 Residential

Fire Loss Estimates published by the

CPSC and available on their web site

(www.cpsc.gov), total residential

electrical equipment resulted in

$1.68 billion in fire losses in 1998,

the latest year available.

AFCI Types and Product Categories

The table below contains the current UL AFCI Product Categories as well as a similar product referred to as a leakage-current detection and interruption (LCDI) device. These product categories are tabulated by CCN (Category Control Number), product category name and AFCI or LCDI Type definition.

By clicking on the CCN you will be linked to the UL Online Certifications Directory database which will provide you with the UL Guide Information for the category and all current Listings under that Product Category.

AVYI is the main category that all AFCI sub-categories fall under. It contains the general information pertinent to all AFCI categories and sub-categories.

These following types of AFCIs are intended for permanent installation in a branch circuit (or feeder where noted).

Home AFCI Categories Web Links

UL.com - Regulators - AFCIs - Categories

CCN Product Category and Type Definition

AVYI (Main Guide)

Arc Fault Circuit Interrupters (AFCI) - A device intended to mitigate the effects of arcing faults by functioning to de-energize the circuit when an arc-fault is detected.


AVZQ Arc Fault Circuit Interrupters, Branch/Feeder Type - A device intended to be installed at the origin of a branch circuit or feeder, such as at a panelboard. It is intended to provide protection of the branch circuit wiring, feeder wiring, or both, against unwanted effects of arcing. This device also provides limited protection to branch circuit extension wiring. It may be a circuit-breaker type device or a device in its own enclosure mounted at or near a panelboard.

AWAH Arc Fault Circuit Interrupters, Combination Type - An

The following types of AFCIs are portable devices and may be incorporated into appliances or utilization equipment.

The following device is similar to AFCIs, they are referred to as leakage-current detection and interruption (LCDI) devices.

AFCI which complies with the requirements for both branch/feeder and outlet circuit AFCIs. It is intended to protect downstream branch circuit wiring and cord sets and power-supply cords.

AWBZ Arc Fault Circuit Interrupters, Outlet Branch Circuit Type - A device intended to be installed as the first outlet in a branch circuit. It is intended to provide protection to downstream branch circuit wiring, cord sets, and power-supply cords against the unwanted effects of arcing. This device also provides protection to upstream branch circuit wiring. It is intended to be provided with or without receptacle outlets.

AWCG Arc Fault Circuit Interrupters, Outlet Circuit Type - A device intended to be installed at a branch circuit outlet, such as at an outlet box. It is intended to provide protection of cord sets and power-supply cords connected to it (when provided with receptacle outlets) against the unwanted effects of arcing. This device may provide feed-through protection of the cord sets and power-supply cords connected to downstream receptacles.


AWAY Arc Fault Circuit Interrupters, Cord Type - A plug-in device intended to be connected to a receptacle outlet. It is intended to provide protection to the power-supply cord connected to it against the unwanted effects of arcing. The cord may be integral to the device. The device has no additional outlets.

AWDO Arc Fault Circuit Interrupters, Portable Type - A plug-in device intended to be connected to a receptacle outlet and provided with one or more outlets. It is intended to provide protection to connected cord sets and power-supply cords against the unwanted effects of arcing.


ELGN Leakage-Current Detection And Interruption (LCDI) – This is a device provided in a power supply cord or cord set that senses leakage current flowing between or from the integral cord conductors and interrupts the circuit at a predetermined level of leakage current.

Copyright © 2001 Underwriters Laboratories Inc.

Arc-Fault Circuit Interrupters (AFCIs) -Type and Performance Considerations

In February of 1999, UL published the First Edition of the Standard for Arc-FaultCircuit-Interrupters (AFCIs), UL1699. According to the National Electrical Code(NEC), an AFCI is defined as a device intended to provide protection from theeffects of arc faults by recognizing characteristics unique to arcing and byfunctioning to de-energize the circuit when an arc fault is detected. The 2002NEC will require all branch circuits that supply 125-volt, single-phase, 15- and20-ampere outlets installed in dwelling unit bedrooms to be protected by an AFCIlisted to provide protection to the entire branch circuit.

Branch Circuits

A branch circuit is defined in Article 100 of the NEC as the circuit conductorsbetween the final overcurrent device protecting the circuit and the outlet(s). Thelength of a branch circuit can vary from several feet to several hundred feet, andinclude from one to several outlets. Figure 1 shows a pictorial representation ofa typical branch circuit that could be associated with a dwelling unit bedroom.

Figure 1 – Pictorial Representation of a Typical Branch Circuit (Not to Scale)


The branch circuit overcurrent protection is provided by a fuse or circuit breakerusually located in a centralized panelboard that is served with power by the localutility. As the name implies, overcurrent protection protects the branch circuitagainst any currents that are in excess of the rated current or ampacity of thebranch circuit conductors. Overcurrents can be the result of overloads, shortcircuits, or ground faults. Overcurrent protection is provided to open the circuit ifthe current reaches a value that will cause an excessive or dangeroustemperature in the branch circuit conductors or conductor insulation.

The branch circuit conductors are normally contained within a non-metallic cable(NM-B), armored cable (AC), or a metal or non-metallic raceway such as conduitor tubing. Non-metallic cables and raceway systems contain a separateconductor for equipment grounding purposes. Metal armor cables and racewaysmay contain an equipment grounding conductor, but in most cases the metalitself is permitted to serve as the equipment grounding path.

The branch circuit conductors extend throughout the building to outlets, whichmay be a receptacle outlet for connecting to cord- and plug-connectedappliances, or to fixed equipment, such as a lighting outlet for a wall or ceilingmounted lighting fixture (luminaire).

Receptacle outlets in the branch circuit provide for the connection of cord-connected appliances, which in a bedroom may include appliances such asportable lamps, clock-radios, and portable air heaters. The cords attached tothese appliances are generally referred to as power supply cords, as they supplythe power from the branch circuit to the cord-connected appliance. In somecases, a power supply cord is not long enough to reach from the intendedlocation of the appliance to the nearest receptacle outlet. In these situations, acord set, often referred to as an extension cord, is used to extend the length ofthe appliance power supply cord to the electrical outlet.

Cord sets and power supply cords are made from flexible cords that havedesignations such as SPT-2 which is often used on portable lamps and light dutyextension cords. Although flexible cords are not a substitute for fixed branchcircuit wiring, they are tested for mechanical impact and flexural strengthproperties that are suitable for their intended application. Flexible cords may ormay not be provided with an equipment grounding conductor depending on theapplication or appliance involved. Cord sets and power supply cords are not partof the branch circuit wiring, but since they extend power beyond the branchcircuit, they can be subjected to the same overloads, short circuits, and groundfaults as would the branch circuit wiring.

Branch Circuit Protection

The branch circuit overcurrent protective device (OCPD), (i.e. a fuse or circuitbreaker), is specifically designed to protect electrical circuits, including the


branch circuit conductors and flexible cords, against the unwanted effects ofovercurrents. For example, when too many products are plugged into the sameelectrical outlet, and the total load current exceeds the rating of the branch circuit(i.e. 15 or 20 amps), the OCPD will open the circuit before damage to equipmentor a fire occurs. However, an OCPD is not designed to protect the circuit againstarcing faults. Because of the time-current characteristics of the OCPD necessaryto provide effective protection against overcurrents, some arcing faults, includingdamaging arcing faults, may have time and/or current characteristics below thethreshold levels necessary to open the OCPD.

Arcing Faults

“Arcing” is defined as a luminous discharge of electricity across an insulatingmedium. The electrical discharge of an arc can involve temperatures on the orderof several thousand degrees Celsius. In general, arcing can be divided into twocategories: (1) non-contact arcing and (2) contact arcing.

“Non-contact arcing” is arcing that does not require direct physical contactbetween the conductors where the arcing is taking place. With arcing betweenconductors separated by insulation, the mechanism of initiating an arc betweenstationary conductors separated by insulation will depend on the type andgeometry of the conductors and insulation between them. “Contact arcing” isarcing that involves direct or indirect physical contact between the conductors or"electrodes" where the arcing is taking place, such as arcing between closing orparting conductors making or breaking a circuit.

Arcing faults can occur in one of two ways, series arcing faults or parallel arcingfaults. A series arcing fault can occur when one of the current-carrying paths(e.g. a single wire) in series with the load is unintentionally broken. For example,extreme flexing in an appliance power supply cord can cause one of theconductors to open and arc when flexed. Series arcing faults are limited incurrent to the load current of the connected appliance or appliances in thatcircuit. Parallel arcing faults occur when there is an unintentional conductingpath between two conductors of opposite polarity, such as between a black andwhite conductor, or between a line conductor and ground. Parallel arcing faultsgenerally involve high currents, as they are limited only by the available faultcurrent of the circuit.

AFCI Types

The UL1699 Standard addresses several types of AFCIs. Each type of AFCI isintended for different applications and/or protection of different aspects of thebranch circuit and extension wiring. Three types of AFCIs for permanentconnection to the branch circuit are identified in UL1699 as follows:


• Branch/Feeder AFCI – This device is installed at the origin of a branch circuitor feeder, such as at a panelboard, to provide protection of the branch circuitwiring, feeder wiring, or both, against unwanted effects of arcing. This devicealso provides limited protection to branch circuit extension wiring (e.g. cordsets and power supply cords). These may be a circuit-breaker type devicesor a device in its own enclosure mounted at or near a panelboard.

• Outlet Circuit AFCI – This device is installed at a branch circuit outlet, suchas at an outlet box, to provide protection of cord sets and power-supply cordsconnected to it (when provided with receptacle outlets) against the unwantedeffects of arcing. This device may provide feed-through protection of the cordsets and power-supply cords connected to downstream receptacles.

• Combination AFCI – This is an AFCI which complies with the requirementsfor both branch/feeder and outlet circuit AFCIs. It is intended to protectdownstream branch circuit wiring, cord sets and power-supply cords.

The NEC and AFCIs

During the revision process for the 2002 NEC there were several proposals torevise Sec. 210-12 to require both a branch/feeder and outlet circuit AFCIs inbranch circuits required to be protected (bedrooms). This would provideprotection to both the branch circuit wiring, as well as cord sets and power supplycords that extend beyond the branch circuit. The Code Panel did not acceptthese proposals. There was also a proposal for the 2002 NEC to permit either abranch/feeder AFCI located at the origin of the branch circuit, or a new type ofAFCI designated an “outlet branch circuit” type located at the first outletreceptacle. A proposed revision to UL1699 would include this new type of AFCIdefined as follows:

• Outlet Branch Circuit AFCI – A device intended to be installed as the firstoutlet in a branch circuit. It is intended to provide protection to downstreambranch circuit wiring, cord sets and power-supply cords against the unwantedeffects of arcing. These devices also provide protection to upstream branchcircuit wiring.

The final language agreed upon by the Code Panel for the 2002 NEC for Sec.210.12 will indicate the following: “All branch circuits that supply 125-volt, single-phase, 15- and 20-ampere outlets installed in dwelling unit bedrooms shall beprotected by an arc-fault circuit interrupter listed to provide protection to theentire branch circuit.”


AFCI Tests

As the UL1699 Standard continues to develop and address different producttypes and technology enhancements, it is important to understand how each typeof AFCI is suitable for protecting various regions of the entire circuit against arcfaults, and the extent and conditions under which this protection will be provided.Four different arc-fault tests are identified in UL1699 as shown in Figure 2.

Tests Branch/feederAFCI

CombinationAFCI

Outlet branchcircuitAFCI

Carbonized path arc ignition test <series>

NM-B insulation cut X X X(+)

<new> NM-B w/o gnd insulation cut X(+)

Carbonized path arc interruption test <parallel>

SPT-2 insulation cut X X X

NM-B insulation cut X X X

Carbonized path arc clearing time test <series>

SPT-2 insulation cut X X

<new> NM-B insulation cut X(+)

Point contact arc test <parallel>

SPT-2 insulation cut X X X

NM-B insulation cut X X X

(+) – also includes an upstream insulation cut

Figure 2 – AFCI Arc-Fault Tests

The Carbonized Path Arc Ignition Test is a non-contact arcing test conductedwith NM-B cable with a series insulation cut. Tests are conducted with arcingcurrents of 5 A, 10 A, rated current, and 150% rated current. TheBranch/Feeder, Combination, and Outlet Branch Circuit AFCIs are subjected tothe Carbonized Path Arc Ignition Test. The Outlet Branch Circuit AFCI issubjected to the Carbonized Path Arc Ignition Test with the arcing occurringupstream, to represent series arcing in the branch circuit wiring between theorigin of the branch circuit and the first outlet receptacle. The Outlet BranchCircuit AFCI is also subjected to the Carbonized Path Arc Ignition Test using NM-B cable without a grounding conductor, as may be found in some older homesbuilt over 40 years ago.

The Carbonized Path Arc Interruption Test is a non-contact arcing test conductedwith NM-B cable and SPT-2 flexible cord with a parallel insulation cut. Tests areconducted with arcing currents of 75 A and 100 A. The Branch/Feeder,Combination, and Outlet Branch Circuit AFCIs are subjected to the Carbonized


Path Arc Interruption Test, however, the Outlet Branch Circuit AFCI is not testedwith this parallel arcing occurring upstream from the device.

The Carbonized Path Arc Clearing Time Test is a non-contact arcing testconducted with SPT-2 flexible cord with a series insulation cut. Tests areconducted with arcing currents of 5 A, 10 A, rated current, and 150% ratedcurrent. The Outlet Branch Circuit and Combination AFCIs are subjected to theCarbonized Path Arc Clearing Time Test. The Branch/Feeder AFCI is notsubjected to this series arcing test with flexible cord as found in many cord setsand power supply cords. The Outlet Branch Circuit AFCI is subjected to theCarbonized Path Arc Clearing Time Test with NM-B cable and the arcingoccurring upstream, to represent series arcing in the branch circuit wiringbetween the origin of the branch circuit and the first outlet receptacle.

The Point Contact Arcing Test is a contact arcing test conducted with NM-Bcable and SPT-2 flexible cord with a parallel insulation cut. Tests are conductedwith arcing currents of 75 A through 500 A. The Branch/Feeder, Combination,and Outlet Branch Circuit AFCIs are subjected to the Point Contact Arcing Test,however, the Outlet Branch Circuit AFCI is not tested with this parallel arcingoccurring upstream from the device.

Further Information

For more information on AFCIs, see the Regulators Page on the UL Web site at:

http://www.ul.com/regulators/afci/index.html

Arc Fault Circuit Interrupter(AFCI)

FACT SHEET

THE AFCIThe “AFCI” is an arc fault circuitinterrupter. AFCIs are newly-developedelectrical devices designed to protectagainst fires caused by arcing faults in thehome electrical wiring.

THE FIRE PROBLEMAnnually, over 40,000 fires are attributedto home electrical wiring. These firesresult in over 350 deaths and over 1,400injuries each year1. Arcing faults are oneof the major causes of these fires. Whenunwanted arcing occurs, it generates hightemperatures that can ignite nearbycombustibles such as wood, paper, andcarpets.

Arcing faults often occur in damaged ordeteriorated wires and cords. Some causesof damaged and deteriorated wiring includepuncturing of wire insulation from picturehanging or cable staples, poorly installedoutlets or switches, cords caught in doorsor under furniture, furniture pushed againstplugs in an outlet, natural aging, and cordexposure to heat vents and sunlight.

HOW THE AFCI WORKSConventional circuit breakers only respond to overloads and short circuits; so they do notprotect against arcing conditions that produce erratic current flow. An AFCI is selectiveso that normal arcs do not cause it to trip.

The AFCI circuitry continuously monitors current flow through the AFCI. AFCIs useunique current sensing circuitry to discriminate between normal and unwanted arcingconditions. Once an unwanted arcing condition is detected, the control circuitry in the

1 Ault, Singh, and Smith, “1996 Residential Fire Loss Estimates”, October 1998, U.S. ConsumerProduct Safety Commission, Directorate for Epidemiology and Health Sciences.

http://www.cpsc.gov/library/fire96.pdf

AFCI trips the internal contacts, thus de-energizing the circuit and reducing the potentialfor a fire to occur. An AFCI should not trip during normal arcing conditions, which canoccur when a switch is opened or a plug is pulled from a receptacle.

Presently, AFCIs are designed into conventional circuit breakers combining traditionaloverload and short-circuit protection with arc fault protection. AFCI circuit breakers(AFCIs) have a test button and look similar to ground fault circuit interrupter (GFCI)circuit breakers. Some designs combine GFCI and AFCI protection. Additional AFCIdesign configurations are anticipated in the near future.

It is important to note that AFCIs are designed to mitigate the effects of arcing faults butcannot eliminate them completely. In some cases, the initial arc may cause ignition priorto detection and circuit interruption by the AFCI.

The AFCI circuit breaker serves a dual purpose – not only will it shut off electricity in theevent of an “arcing fault”, but it will also trip when a short circuit or an overload occurs.The AFCI circuit breaker provides protection for the branch circuit wiring and limitedprotection for power cords and extension cords. Single-pole, 15- and 20- ampere AFCIcircuit breakers are presently available.

WHERE AFCIs SHOULD BE USEDThe 1999 edition of the National Electrical Code, the model code for electrical wiringadopted by many local jurisdictions, requires AFCIs for receptacle outlets in bedrooms,effective January 1, 2002. Although the requirement is limited to only certain circuits innew residential construction, AFCIs should be considered for added protection in othercircuits and for existing homes as well. Older homes with aging and deteriorating wiringsystems can especially benefit from the added protection of AFCIs. AFCIs should alsobe considered whenever adding or upgrading a panel box while using existing branchcircuit conductors.

INSTALLING AFCIsAFCI circuit breakers should be installed by a qualified electrician. The installer shouldfollow the instructions accompanying the device and the panel box.

In homes equipped with conventional circuit breakers rather than fuses, an AFCI circuitbreaker may be installed in the panel box in place of the conventional circuit breaker toadd arc protection to a branch circuit. Homes with fuses are limited to receptacle orportable-type AFCIs, which are expected to be available in the near future, or AFCIcircuit breakers can be added in separate panel boxes next to the fuse panel box.

TESTING AN AFCIAFCIs should be tested after installation to make sure they are working properly andprotecting the circuit. Subsequently, AFCIs should be tested once a month to make surethey are working properly and providing protection from fires initiated by arcing faults.

A test button is located on the front of the device. The user should follow the instructionsaccompanying the device. If the device does not trip when tested, the AFCI is defectiveand should be replaced.

AFCIs vs. GFCIsThe AFCI should not be confused with the GFCI or ground fault circuit interrupter. TheGFCI is designed to protect people from severe or fatal electric shocks while the AFCIprotects against fires caused by arcing faults. The GFCI also can protect against someelectrical fires by detecting arcing and other faults to ground but cannot detect hazardousacross-the-line arcing faults that can cause fires.

A ground fault is an unintentional electric path diverting current to ground. Groundfaults occur when current leaks from a circuit. How the current leaks is very important.If a person’s body provides a path to ground for this leakage, the person could be injured,burned, severely shocked, or electrocuted.

The National Electrical Code requires GFCI protection for receptacles located outdoors;in bathrooms, garages, kitchens, crawl spaces and unfinished basements; and at certainlocations such as near swimming pools. A combination AFCI and GFCI can be used tosatisfy the NEC requirement for GFCI protection only if specifically marked as acombination device.

Consumer Product Safety Commission Preventing Home Fires: Arc Fault Circuit Interrupters (AFCIs)

Problems in home wiring, like arcing and sparking, are associated with more than 40,000 home fires each year. These fires claim over 350 lives and injure 1,400 victims annually. A new electrical safety device for homes, called an arc fault circuit interrupter or AFCI, is expected to provide enhanced protection from fires resulting from these unsafe home wiring conditions. Typical household fuses and circuit breakers do not respond to early arcing and sparking conditions in home wiring. By the time a fuse or circuit breaker opens a circuit to defuse these conditions, a fire may already have begun. Several years ago, a CPSC study identified arc fault detection as a promising new technology. Since then, CPSC electrical engineers have tested the new AFCIs on the market and found these products to be effective. Requiring AFCIs AFCIs are already recognized for their effectiveness in preventing fires. The most recent edition of the National Electrical Code, the widely-adopted model code for electrical wiring, will require AFCIs for bedroom circuits in new residential construction, effective January 2002. Future editions of the code, which is updated every three years, could expand coverage. AFCIs vs. GFCIs AFCIs should not be confused with ground fault circuit interrupters or GFCIs. The popular GFCI devices are designed to provide protection from the serious consequences of electric shock. While both AFCIs and GFCIs are important safety devices, they have different functions. AFCIs are intended to address fire hazards; GFCIs address shock hazards. Combination devices that include both AFCI and GFCI protection in one unit will become available soon. AFCIs can be installed in any 15 or 20-ampere branch circuit in homes today and are currently available as circuit breakers with built-in AFCI features. In the near future, other types of devices with AFCI protection will be available. Should You Install AFCIs? You may want to consider adding AFCI protection for both new and existing homes. Older homes with ordinary circuit breakers especially may benefit from the added protection against the arcing faults that can occur in aging wiring systems. For more information about AFCIs, contact an electrical supply store, an electrician, or the manufacturer of the circuit breakers already installed in your home. Sometimes these components can be replaced with AFCIs in the existing electrical panel box. Be sure to have a qualified electrician install AFCIs; do not attempt this work yourself. The installation involves working within electrical panel boxes that are usually electrically live, even with the main circuit breakers turned off. The U.S. Consumer Product Safety Commission protects the public from the unreasonable risk of injury or death from 15,000 types of consumer products under the agency's jurisdiction. To report a dangerous product or a product-related injury, you can go to CPSC's forms page and use the first on-line form on that page. Or, you can call CPSC's hotline at (800) 638-2772 or CPSC's teletypewriter at (800) 638-8270, or send the information to [email protected]. Consumers can obtain this publication and additional publication information from the Publications section of CPSC's web site or by sending your publication request to [email protected]. If you would like to receive CPSC's recall notices, subscribing to the email list will send all press releases to you the day they are issued. This document is in the public domain. It may be reproduced without change in part or whole by an individual or organization without permission. If it is reproduced, however, the Commission would appreciate knowing how it is used. Write the U.S. Consumer Product Safety Commission, Office of Information and Public Affairs, Washington, D.C. 20207 or send an e-mail to [email protected].

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