U.S. Fire Administration/National Fire Data Center

Data Sources and National Estimates

Methodology Overview for the

U.S. Fire Administration’s Topical Fire 

Report Series (Volume 16)

July 2015
U.S. Fire Administration

Mission Statement

We provide National leadership to foster a solid foundation for our fire and emergency services stakeholders in 

prevention, preparedness, and response.
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 1

Data Sources and National Estimates Methodology Overview for the

U.S. Fire Administration’s Topical Fire Report Series (Volume 16)

Background

The topical reports produced as part of the U.S. Fire 

Administration’s (USFA’s) Topical Fire Report Series 

explore facets of the fire problem in the U.S. as depicted 

through data collected in USFA’s National Fire Incident 

Reporting System (NFIRS). Each topical report briefly 

addresses the nature of the specific fire or fire-related 

topic, highlights important findings from the data, and 

may suggest other resources to consider for further 

information. The national estimates presented in the 

topical reports are based on data from NFIRS and the 

National Fire Protection Association’s (NFPA’s) annual 

Survey of Fire Departments for U.S. Fire Experience.

This document addresses national estimates as well as 

the data sources used to derive the estimates, with an 

emphasis on the specific NFIRS data elements analyzed 

in the topical reports. “Unknown” data entries and missing data values are also discussed. Because the majority 

of USFA’s topical reports address fires and losses in buildings, this paper focuses on buildings.

Data Sources

National Fire Incident Reporting System

NFIRS is the world’s largest collection of data for incidents to which fire departments respond. About 1 million fire incident records and 21 million nonfire incident 

records are added to the database each year. In 2013, the 

most recent year of data available, 20,129 fire departments reported fire incidents to NFIRS. Across participating entities, 67 percent of U.S. fire departments reported 

fire incidents to NFIRS in 2013.1

 With two-thirds of all 

fire departments nationwide reporting fire incidents to 

NFIRS, the reporting departments represent a very large 

dataset that enables USFA to develop reasonable estimates of various aspects of the fire problem. Although 

some states do require their departments to participate 

in the state system, participation in NFIRS is voluntary. 

Furthermore, if a fire department is a recipient of a Fire 

Act Grant, participation is required.2

 For the years 2011-

2013, data were submitted by all 50 states, the District of 

Columbia and the Native American Tribal Authorities. It 

is important to note that not all fire departments within 

participating states report to NFIRS.

Because NFIRS incident reports are submitted voluntarily, the data do not represent a statistically selected 

sample. Additionally, the NFIRS data are not stand-alone. 

Therefore, USFA currently scales up raw NFIRS data 

or percentages to NFPA’s annual national survey estimates. This approach is discussed further in the National 

Estimates Overview section.

National Fire Protection Association Survey 

Estimates

The NFPA’s Survey of Fire Departments for U.S. Fire 

Experience is based on a stratified random sample of U.S. 

fire departments.3

 The sample of departments is stratified 

by size of community protected, and ratio estimation 

methodology is used to develop national level summary 

estimates on fire loss statistics (the total numbers of 

reported fires, fire deaths, fire injuries and direct dollar 

loss) as well as summary estimates of fires and losses 

by major incident types (i.e., structure, vehicle, outside 

and other).

The 2011-2013 NFPA estimates of residential structure 

fires and losses used to develop USFA’s national estimates 

of residential building fires are presented in Table 1. 

From 2011 to 2013, the NFPA survey produced an annual 

1

For 2013, NFPA estimated that there were 30,052 fire departments in the U.S. Source: NFPA, U.S. Fire Department Profile 2013, http://

www.nfpa.org/research/reports-and-statistics/the-fire-service/administration/us-fire-department-profile, November 2014.

2

From the fiscal year 2013 Assistance to Firefighters Grant (AFG) Program Funding Opportunity Announcement — While NFIRS reporting is strongly encouraged, NFIRS reporting is not a requirement to apply for or be awarded a grant within the AFG Program. However, 

any fire-based organization that receives an AFG must commence reporting to NFIRS prior to the beginning of its period of performance. 

In order to be compliant and close out the grant, the grantee may be asked by the Federal Emergency Management Agency to provide 

proof of compliance in reporting to NFIRS. Any grantee that stops reporting to NFIRS during the grant’s period of performance is subject 

to having the award(s) modified or withdrawn. See http://www.fema.gov/media-library-data/1382974632566-bf855cd302840cefcc3c849

3e9858d0c/2013+ASSISTANCE+TO+FIREFIGHTERS+GRANT+PROGRAM+-+FOA.pdf.

3

For detailed information regarding NFPA’s survey methodology, see NFPA’s report “Fire Loss in the United States During 2013,” 

September 2014, http://www.nfpa.org/~/media/Files/Research/NFPA%20reports/Overall%20Fire%20Statistics/osfireloss.pdf.
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 2

average estimate of 384,700 residential structure fires 

resulting in 2,580 civilian fire deaths, 13,375 civilian fire 

injuries, and $7.1 billion in property damage each year.4

Of these NFPA residential structure fire and loss estimates, 

70 percent of the fires, 56 percent of the deaths, 56 percent of the injuries, and 59 percent of the dollar losses 

were reported to NFIRS during this three-year period.

Table 1. NFPA Estimates of Residential Structure Fires and Losses (2011-2013)

Year Residential Structure 

Fires

Residential Structure 

Fire Deaths

Residential Structure 

Fire Injuries

Residential Structure 

Fire Dollar Loss

(in millions)

2011 386,000 2,550 14,360 $7,054

2012 381,000 2,405 13,175 $7,199

2013 387,000 2,785 12,575 $6,969

Source: NFPA, “Fire Loss in the United States,” 2011-2013.

The 2011-2013 NFPA estimates of nonresidential structure fires and losses used to develop USFA’s national 

estimates of nonresidential building fires are presented 

in Table 2. From 2011 to 2013, the NFPA survey produced an annual average estimate of 99,500 nonresidential structure fires resulting in 75 civilian fire deaths, 

1,425 civilian fire injuries, and $2.6 billion in property 

damage.5

 Of these NFPA nonresidential structure fire and 

loss estimates, 73 percent of the fires, 97 percent of the 

deaths, 48 percent of the injuries and 79 percent of the 

dollar losses were reported to NFIRS during this threeyear period.

Table 2. NFPA Estimates of Nonresidential Structure Fires and Losses (2011-2013)

Year Nonresidential Structure 

Fires

Nonresidential Structure 

Fire Deaths

Nonresidential Structure 

Fire Injuries

Nonresidential Structure 

Fire Dollar Loss 

(in millions)

2011 98,500 90 1,275 $2,639

2012 99,500 65 1,525 $2,577

2013 100,500 70 1,500 $2,557

Source: NFPA, “Fire Loss in the United States,” 2011-2013.

National Estimates Overview

National estimates presented in USFA’s Topical Fire Report 

Series (Volume 16) are based on 2011-2013 NFIRS data, 

structure fire loss estimates from 2011-2013 NFPA’s annual 

surveys, and 2011-2013 USFA’s building fire loss estimates.

Overall estimates of the fire problem come from 

NFPA’s annual Survey of Fire Departments for U.S. Fire 

Experience.6

 As previously noted, this survey produces 

national-level summary estimates on fire loss statistics 

(the total numbers of reported fires, fire deaths, fire injuries and direct dollar loss) as well as summary estimates 

of fires and losses by major incident types (i.e., structure, 

vehicle, outside and other). The summary estimates by 

major incident type are further broken down to the next 

tier (e.g., residential structures, highway vehicles and the 

like). The raw NFPA survey data are not available to the 

public, USFA or various other national fire data analysts.

All nationally based estimates on subsets of fire data are 

derived by scaling up the raw NFIRS data. These estimates are based on a method of apportioning the NFPA 

estimates for total fires and structure, vehicle, outside 

and other fires.7

 Generally, these national estimates are 

4

Fires are rounded to the nearest 100, deaths to the nearest five, injuries to the nearest 25, and dollar loss to the nearest $100 million.

5

Fires are rounded to the nearest 100, deaths to the nearest five, injuries to the nearest 25, and dollar loss to the nearest $100 million.

6

For detailed information regarding NFPA’s survey methodology, see NFPA’s report “Fire Loss in the United States During 2013,” 

September 2014, http://www.nfpa.org/~/media/Files/Research/NFPA%20reports/Overall%20Fire%20Statistics/osfireloss.pdf.

7

The foundation of computing national estimates is based on “The National Estimates Approach to U.S. Fire Statistics” by Hall, J. and 

Harwood, B., http://www.nfpa.org/~/media/6906FADB2CE149488FB5103F4A750A05.ashx. 
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 3

derived by computing a percentage of fires, deaths, 

injuries or dollar loss in a particular NFIRS category 

and multiplying it by the corresponding total estimate 

from the NFPA annual survey.8 This methodology is the 

accepted practice of national fire data analysts.

One problem with this approach is that the proportions 

of fires and fire losses differ between the large NFIRS 

dataset and the NFPA survey sample.9

 Nonetheless, to be 

consistent with approaches being used by other fire data 

analysts, the NFPA estimates of fires, deaths, injuries and 

dollar loss are used as a starting point. The details of the 

fire problem below this level are based on proportions 

from NFIRS. Because the proportions of fires and fire 

losses differ between NFIRS and the NFPA estimates, 

from time to time, this approach leads to inconsistencies. 

These inconsistencies will remain until all estimates can 

be derived from NFIRS data alone.

Ideally, one would like to have all of the data come from 

one consistent data source — NFIRS. One of the critical 

pieces of data necessary to do so is missing: the overall 

population protected by all reporting fire departments. 

This “residential population protected” is not reported to 

NFIRS nor is the data easy to come by, especially where 

a county or other jurisdiction is served by several fire 

departments that each report their fires independently.

Other issues — such as full reporting because of reporting deadlines, data access, budgetary considerations 

and the like — add a layer of complexity to using the 

NFIRS data to create estimates. Nonetheless, with such a 

large wealth of fire incident data, the USFA believes it is 

possible to harness the NFIRS data to produce national 

estimates of the U.S. fire problem.

Through the years, a number of ad hoc studies have been 

undertaken to identify NFIRS nonresponse bias, none of 

which have identified major reporting issues. Most of the 

NFIRS data exhibit stability from one year to the next, 

without radical changes. Results based on the full dataset 

are generally similar to those based on part of the data, 

another indication of data reliability. In short, the NFIRS 

data is a very large and reasonably stable dataset that is 

used as input to develop national estimates.

Structures Versus Buildings in the National Fire 

Incident Reporting System

NFIRS allows for the differentiation between buildings 

and nonbuildings. In NFIRS, a structure is a built object 

and can include nonbuildings, such as platforms, tents, 

connective structures (e.g., bridges, fences), telephone 

poles and various other structures, in addition to buildings. Analyses of 2011-2013 NFIRS structure fire data 

show that, by and large, the majority (96 percent) of 

structure fires occur in buildings.

The distinction between buildings and nonbuildings 

is particularly important when determining the effectiveness of nonbehavior-based fire safety mechanisms, 

such as smoke alarms and residential sprinklers. These 

important components of early fire detection apply to 

buildings and not necessarily to these other types of 

structures. To facilitate analysis of these components 

and to acknowledge that prevention efforts generally are 

centered on buildings, USFA separates buildings from 

the rest of the structures. For these reasons, USFA focuses 

on producing building fire and loss estimates separately 

for residential and nonresidential buildings.

8

The NFPA summary estimates are used for the overall U.S. fire losses; fire losses from structure, vehicle, outside and other fires; and as the 

basis for USFA’s estimates of residential and nonresidential building fires and losses. The alternative approach for these summary numbers is 

to use the relative percentage of fires (or other loss measures) from NFIRS and scale up (multiply by) the NFPA estimate of total fires. 

9

For additional information regarding the differences in proportions of fires and losses between NFIRS data and the NFPA survey, see 

the section titled Differences Between NFIRS Data and NFPA Survey Data in USFA’s “Data Sources and Methodology Documentation,” 

March 2014, http://www.usfa.fema.gov/downloads/pdf/statistics/data_sources_methodology.pdf.
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 4

Residential Buildings

Table 3 shows the raw numbers of residential building fires and losses reported to NFIRS from 2011 to 2013.

Table 3. Residential Building Fires and Losses Reported to NFIRS (2011-2013)

Year Residential Building 

Fires

Residential Building 

Fire Deaths

Residential Building 

Fire Injuries

Residential Building Fire 

Dollar Loss 

(in millions)

2011 270,164 1,459 7,990 $3,994

2012 248,666 1,388 7,191 $3,833

2013 259,283 1,397 6,844 $4,243

Source: USFA, 2011-2013 NFIRS.

Table 4 shows the raw numbers of residential structure 

fires and losses reported to NFIRS from 2011 to 2013. 

On average from 2011 to 2013, 97 percent of residential 

structure fires, 98 percent of associated deaths, 98 percent of injuries, and 97 percent of dollar losses reported 

to NFIRS occurred in residential buildings.

Table 4. Residential Structure Fires and Losses Reported to NFIRS (2011-2013)

Year Residential Structure 

Fires

Residential Structure 

Fire Deaths

Residential Structure 

Fire Injuries

Residential Structure 

Fire Dollar Loss 

(in millions)

2011 286,103 1,519 8,254 $4,236

2012 253,333 1,400 7,259 $3,885

2013 263,853 1,411 6,911 $4,300

Source: USFA, 2011-2013 NFIRS.

Nonresidential Buildings

Table 5 shows the raw numbers of nonresidential building fires and losses reported to NFIRS from 2011 to 2013.

Table 5. Nonresidential Building Fires and Losses Reported to NFIRS (2011-2013)

Year Nonresidential Building 

Fires

Nonresidential Building 

Fire Deaths

Nonresidential Building 

Fire Injuries

Nonresidential Building 

Fire Dollar Loss 

(in millions)

2011 67,885 83 702 $1,856

2012 64,926 53 608 $1,859

2013 66,592 65 576 $2,114

Source: USFA, 2011-2013 NFIRS.

Table 6 shows the raw numbers of nonresidential 

structure fires and losses reported to NFIRS from 2011 

to 2013. On average, about 91 percent of nonresidential 

structure fires, 92 percent of deaths, 92 percent of injuries, and 95 percent of dollar losses reported to NFIRS 

from 2011 to 2013 occurred in nonresidential buildings.

Table 6. Nonresidential Structure Fires and Losses Reported to NFIRS (2011-2013)

Year Nonresidential Structure 

Fires

Nonresidential Structure 

Fire Deaths

Nonresidential Structure 

Fire Injuries

Nonresidential Structure 

Fire Dollar Loss

(in millions)

2011 78,323 94 810 $2,011

2012 69,611 54 634 $1,939

2013 71,450 70 611 $2,197

Source: USFA, 2011-2013 NFIRS.
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 5

National Estimates of Building Fires and Losses

Based on the raw numbers of building fires and structure fires reported to NFIRS along with the NFPA survey 

estimates of structure fires, USFA developed a methodology for computing national estimates of residential 

and nonresidential building fires and losses.10 USFA uses 

these national building fire estimates in the Topical Fire 

Report Series, Fire Estimate Summary Series, and various 

other fire data reports.11 Tables 7 and 8 present USFA’s 

national estimates of fires and losses for residential and 

nonresidential buildings, respectively.

Table 7. USFA’s National Estimates of Residential Building Fires and Losses (2011-2013)

Year Residential Building 

Fires

Residential Building 

Fire Deaths

Residential Building 

Fire Injuries

Residential Building 

Fire Dollar Loss — 

Adjusted to 2013 Dollars

(in millions)

2011 364,500 2,450 13,900 $6,889

2012 374,000 2,385 13,050 $7,207

2013 380,300 2,755 12,450 $6,876

Source: USFA, Fire Estimate Summary Series (2004-2013).

Table 8. USFA’s National Estimates of Nonresidential Building Fires and Losses (2011-2013)

Year Nonresidential Building 

Fires

Nonresidential Building 

Fire Deaths

Nonresidential Building 

Fire Injuries

Nonresidential Building 

Fire Dollar Loss — 

Adjusted to 2013 Dollars

(in millions)

2011 85,400 80 1,100 $2,523

2012 92,800 65 1,450 $2,508

2013 93,700 65 1,425 $2,461

Source: USFA, Fire Estimate Summary Series (2004-2013).

National Fire Incident Reporting System 

Data Used in U.S. Fire Administration 

Analyses

Although NFIRS contains hundreds of data elements, 

only a few are used in producing USFA’s topical reports. 

Most of these elements are required to be completed for 

each fire incident type. For small, confined fires (i.e., 

Incident Types 113-118); outside rubbish fires with no 

value (i.e., Incident Types 150-155); and other unclassified fires, however, certain data elements are not 

required to be completed.

A complete list of NFIRS data elements is documented in 

the “NFIRS Complete Reference Guide.”12 Table 9 identifies 

the NFIRS data elements that are used most often in fire 

data analyses in the topical reports produced by USFA.

10

USFA’s methodology for computing national estimates of residential and nonresidential building fires and losses is detailed in USFA’s 

“National Estimates Methodology for Building Fires and Losses,” August 2012, http://www.usfa.fema.gov/downloads/pdf/statistics/

national_estimate_methodology.pdf. 

11

USFA’s Fire Estimate Summary Series as well as 2003-2013 national estimates of residential and nonresidential building fires and losses 

are published at http://www.usfa.fema.gov/data/statistics/. USFA’s Topical Fire Report Series and various other fire data reports are available at http://www.usfa.fema.gov/data/statistics/reports.html. 

12 “NFIRS Complete Reference Guide,” USFA, January 2015, http://www.usfa.fema.gov/downloads/pdf/nfirs/NFIRS_Complete_

Reference_Guide_2015.pdf.
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 6

Table 9. NFIRS Data Elements Used in USFA Analyses

Data Element Description

Required Data 

Element 

for all Fires

Incident Type The actual situation found on-scene when emergency personnel arrived. Yes

Property use The actual use of the property where the incident occurred, not the overall use of 

mixed use properties of which the property is a part. Yes

Incident date The month, day and year of incident. Yes

Alarm time The actual month, day, year and time of day (hour, minute and seconds) when 

the alarm was received by the fire department. Yes

Death

A civilian fire death resulting from the incident or occurring during the mitigation of 

the incident (includes emergency personnel who are not part of the fire department, such as police officers or utility workers).Yes

Injury

A civilian fire injury resulting from the incident or occurring during the mitigation of 

the incident (includes emergency personnel who are not part of the fire department, such as police officers or utility workers).Yes

Dollar loss The sum of the total property and contents dollar losses. Yes

Fire spread13 The extent of fire spread in terms of how far the flame damage extended. No

Area of fire origin The primary use of the area where the fire started within the property. No

Heat source The source of heat that ignited the “item first ignited” to cause the fire. No

Item first ignited

The use or configuration of the item or material first ignited by the heat source. 

The item that had sufficient volume or heat intensity to extend to uncontrolled or 

self-perpetuating fire.

No

Factors contributing to ignition The contributing factors that allowed the heat source and combustible material to 

combine to ignite the fire. No

Presence of detectors The existence of fire detection equipment within its designed range of the fire. No

Presence of automatic 

extinguishing system (AES) The existence of an AES within the AES’s designed range of a fire. No

Source: “NFIRS Complete Reference Guide,” USFA, January 2015.

In addition to the data elements presented in Table 9, “fire 

cause” is a data characteristic included in almost every 

USFA topical report analysis; however, it is not directly 

collected in NFIRS. It is determined for all structure fires 

based on an algorithm using cause-related data elements 

from NFIRS, such as the heat source, item first ignited, 

cause of ignition, factors contributing to ignition, and 

equipment involved in ignition to name a few. The causes 

of fires are often a complex chain of events. To make it 

easier to grasp the “big picture,” 16 midlevel categories of 

fire causes, such as heating, cooking and electrical malfunction, are used by USFA to define structure fire causes.

Structure fires are assigned to one of the 16 midlevel 

cause groupings using a hierarchy of definitions. A fire 

is included in the highest category into which it fits on 

the list. If it does not fit the top category, then the second 

one is considered, and if not that one, the third and so 

on. Once a match is found, the cause is assigned, and no 

further checking of subsequent categories is done in the 

matrix. If no match is found, the incident is assigned a 

fire cause of “unknown.”14

13 Fire spread is not a required data element for all fires. Although not required for confined fires (i.e., Incident Types 113-118), the 

confined fire Incident Types were designed to reflect small, low-loss fires, typically with a fire spread that is limited to the object of fire 

origin. In addition, fire spread is only a required element in the fire module when the Structure Type is coded as an enclosed building 

or fixed portable or mobile structure. Therefore, when analyzing NFIRS building fire data only, fire spread is either required or could be 

inferred for confined fires, and essentially it contains no missing data values. 

14

 USFA’s detailed structure fire cause methodology and definitions are available in the document “National Fire Incident Reporting 

System Version 5.0 Fire Data Analysis Guidelines and Issues,” July 2011, http://www.usfa.fema.gov/downloads/pdf/nfirs/nfirs_data_

analysis_guidelines_issues.pdf.
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 7

Unknown Data Entries and Missing 

Values

On a fraction of the incident reports or casualty reports 

submitted to NFIRS, the desired information for many 

data elements either is reported as “unknown” or is not 

reported at all. The total number of unknown entries or 

missing (i.e., blank or null) values is often larger than 

some of the important subcategories. For example, 46 

percent of fatal fires in residential buildings reported 

from 2011-2013 do not have sufficient data recorded in 

NFIRS to determine fire cause. The lack of data, especially 

for these residential fatal fires, masks the true picture of 

the fire problem. Many prevention and public education 

programs use NFIRS data to target at-risk groups or to 

address critical problems, fire officials use the data in 

decision-making that affects the allocation of firefighting 

resources, and consumer groups and litigators use the 

data to assess product fire incidence. When the unknowns 

are large, the credibility of the data suffers. In some cases, 

even after the best attempts by fire investigators, the 

information is truly unknown. In other cases, the information reported as unknown in the initial NFIRS report 

is not updated after the fire investigation is completed. 

Fire departments need to be more aware of the effect of 

incomplete data reporting and the need to update the 

initial NFIRS report if additional information is available 

after investigation. Efforts have been undertaken at the 

national level to encourage fire departments to close the 

loop on fires after investigations are completed.

In analyses, the unknown and missing data values should 

not be ignored. The approach taken by USFA in presenting the data is to provide not only the “raw” percentages 

of each category, but also the “adjusted” percentages, 

computed using only those incidents for which data were 

provided. This calculation, in effect, distributes the fires 

for which the data are unknown in the same proportion 

as the fires for which the data are known, which may or 

may not be approximately right. Both the reported data 

and the adjusted data (if unknowns are present) are plotted on bar charts in USFA reports.

The following example illustrates distributing the fires 

for which the data are unknown using the cause of 

residential building fires: Cooking was determined as 

the fire cause for 39.7 percent of reported residential 

building fires from 2011 to 2013; another 17.2 percent of 

reported fires had cause unknown. Thus, the percent of 

fires that had their cause reported was 100 minus 17.2 

equals 82.8 percent. With the unknown causes apportioned like the known causes, the adjusted percent of 

cooking fires in residential buildings can then be computed as 39.7 divided by 82.8 equals 47.9 percent.

It is important to note that null and blank values are 

considered unreported data and differ in meaning and 

substance from “unknown” data. In data elements where 

information is required, a null or blank value may invalidate the record and cause it to be excluded from analyses. In addition, many fire data elements are not required 

for NFIRS confined fires (i.e., Incident Types 113-118) 

and, thus, contain missing or null values. Therefore, 

USFA excludes confined fires from the analyses of these 

nonrequired data elements for building fires.

The following section focuses on data elements where 

information is required for nonconfined fires (i.e., 

Incident Types 111 and 120-123); however, the data entries 

for these elements may contain valid “unknown” values. Tables 10 and 11 show the percentages of unknown 

data values for NFIRS data elements that are required for 

only nonconfined residential and nonresidential building 

fires (i.e., the percentages do not reflect confined fires) 

with the exception of “fire cause.” Although USFA’s fire 

cause, as previously discussed, is not a collected NFIRS 

data element per se but rather assigned based on an 

algorithm using cause-related data elements from NFIRS, 

it is included in these tables for ease of presentation. It 

is important to note that percentages of unknown data 

values for “fire cause,” unlike the rest of the required data 

elements for nonconfined fires presented in the tables, 

reflect both confined and nonconfined fires.
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 8

Table 10. Percent of Unknown Values by Specific Data Element for Residential Building 

Fires Reported to NFIRS (2011-2013)

Data Element 2011

Percent Unknown

2012

Percent Unknown

2013

Percent Unknown

Area of fire origin 11.8 13.6 12.7

Heat source 34.7 39.2 37.7

Item first ignited 35.2 37.8 37.1

Factors contributing to ignition 26.0 28.4 28.4

Presence of detectors 30.2 30.5 30.0

Presence of AES 8.5 9.0 8.4

Fire cause 18.4 17.0 16.1

Source: NFIRS.

Note: For 2012 to 2013, increases in the percentages of unknown values in the heat source and factors contributing to ignition fields from those of 2011 are likely the result of an NFIRS edit change (“NFIRS 

Version 5.0 Design Documentation,” January 2012, Relational Edit No. 181, Fire Module, Equipment Involved in Ignition, Page 111, http://www.usfa.fema.gov/downloads/pdf/nfirs/NFIRS_Spec_2012.pdf).

Table 11. Percent of Unknown Values by Specific Data Element for Nonresidential Building 

Fires Reported to NFIRS (2011-2013)

Data Element 2011

Percent Unknown

2012

Percent Unknown

2013

Percent Unknown

Area of fire origin 16.6 18.9 18.3

Heat source 40.4 45.2 43.3

Item first ignited 41.6 43.9 43.1

Factors contributing to ignition 28.0 31.2 30.8

Presence of detectors 20.2 20.0 19.4

Presence of AES 9.9 10.5 10.2

Fire cause 37.0 35.9 35.2

Source: NFIRS.

Note: For 2012 to 2013, increases in the percentages of unknown values in the heat source and factors contributing to ignition fields from those of 2011 are likely the result of an NFIRS edit change (“NFIRS 

Version 5.0 Design Documentation,” January 2012, Relational Edit No. 181, Fire Module, Equipment Involved in Ignition, Page 111, http://www.usfa.fema.gov/downloads/pdf/nfirs/NFIRS_Spec_2012.pdf).

Incomplete Loss Reporting

As troublesome as the fact that insufficient data for the 

various NFIRS data elements can mask the true picture 

of the fire problem and impact the credibility of the 

data, equally challenging is the apparent nonreporting of 

injuries and property loss associated with many fire incidents. For example, there are many reported fires where 

the flame spread indicates damage but property loss is 

not reported. It is notoriously difficult to estimate dollar 

loss, but an approximation is more useful than leaving 

the data element blank. Analysts need to be aware that 

this apparent lack of loss data affects the understanding 

of those fires that cause substantial loss.

Identifying Large Outliers

If the incident record clearly contains outliers, it is 

generally recommended to exclude the record from the 

analysis. Before excluding such records, however, it is 

suggested that a quick Internet search be conducted to 

see if some unusual fire did occur. Additionally, if time 

permits, following up with the fire department that 

submitted the incident record may be the best method to 

use for data verification.

National Fire Incident Reporting System 

Analytic Resources

Several resources are available that provide more detailed 

documentation on using the NFIRS system and NFIRS 

data. The “National Fire Incident Reporting System 

Complete Reference Guide” provides both instructions 

for reporting data to NFIRS and an understanding of the 

data elements collected by the system. It also serves as a 

reference for coding the data.

The document “National Fire Incident Reporting System 

Version 5.0 Fire Data Analysis Guidelines and Issues” discusses analytic considerations and methods of analyzing 

fire incident data using the NFIRS data. Topics include 

the NFIRS 5.0 data structure, general quality assurance 
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 9

issues, and definitions and parameters of common fire 

analyses (e.g., residential building fires or casualties), 

including the methodology for determining structure 

fire causes. The methods, techniques and considerations 

discussed are those used by USFA analysts, and they do 

not necessarily reflect methods, techniques and considerations used by fire data analysts from other agencies and 

organizations. NFIRS data partners may (and do) employ 

their own methods for analyzing the data and may make 

differing assumptions when encountering data issues.

“The National Estimates Approach to U.S. Fire Statistics” 

is the original methodology for creating estimates of 

the U.S. fire problem using the NFPA’s annual Survey of 

Fire Departments for U.S. Fire Experience and the NFIRS 

data. The authors present a detailed consensus procedure 

for such calculations and the supporting rationale. 

“National Estimates Methodology for Building Fires and 

Losses” is the USFA’s application of the national estimates approach to building fires and fire losses. It details 

USFA’s current fire data estimation methodology for 

all building (i.e., residential and nonresidential) fires 

and associated losses.

USFA’s “Data Sources and Methodology Documentation” 

provides an in-depth discussion of the data sources and 

the methodologies used to incorporate these data into 

fire analyses. Lastly, the “Fire Data Analysis Handbook” 

is a resource for those unfamiliar with basic data analysis techniques and their applicability to fire data-based 

analyses.

Resource List

“Data Sources and Methodology Documentation,” USFA, March 2014, http://www.usfa.fema.gov/downloads/pdf/

statistics/data_sources_methodology.pdf.

“Fire Data Analysis Handbook,” Second Edition, USFA, January 2004, http://www.usfa.fema.gov/downloads/pdf/

publications/fa-266.pdf.

Hall, J. and Harwood, B., “The National Estimates Approach to U.S. Fire Statistics,” Fire Technology, Vol. 25, No. 2 

(1989), 99-113, http://www.nfpa.org/~/media/6906FADB2CE149488FB5103F4A750A05.ashx.

“National Estimates Methodology for Building Fires and Losses,” USFA, August 2012, http://www.usfa.fema.gov/

downloads/pdf/statistics/national_estimate_methodology.pdf.

“National Fire Incident Reporting System Version 5.0 Fire Data Analysis Guidelines and Issues,” USFA, July 2011, http://

www.usfa.fema.gov/downloads/pdf/nfirs/nfirs_data_analysis_guidelines_issues.pdf.

“NFIRS Complete Reference Guide,” USFA, January 2015, http://www.usfa.fema.gov/downloads/pdf/nfirs/NFIRS_

Complete_Reference_Guide_2015.pdf.