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 15)

August 2014
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 15)

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 United States 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 firerelated 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 data collection of 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. Fire departments 

reporting fire incidents to NFIRS grew from 20,432 in 

2010 to 20,544 in 2012, the most recent year of data 

available. Across participating entities, 68 percent of U.S. 

fire departments reported fire incidents to NFIRS in 2012.1

With over 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 

1

 For 2012, NFPA estimated that there were 30,100 fire departments in the U.S. Source: NFPA, U.S. Fire Department Profile 

2012, http://www.nfpa.org/research/reports-and-statistics/thefire-service/administration/us-fire-department-profile, October 

2013.

NFIRS is voluntary. Furthermore, if a fire department is a 

recipient of a Fire Act Grant, participation is required.2 For 

the years 2010-2012, data were submitted by all 50 states, 

the District of Columbia and the Native American Tribal 

Authorities. It is important to note that all fire departments within participating states do not report to NFIRS.

Because NFIRS incident reports are submitted voluntarily, 

it is not a statistically selected sample. 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 2010-2012 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 

2010 to 2012, the NFPA survey produced an annual average estimate of 383,667 residential structure fires resulting 

2

 From the Assistance to Firefighters Grant Guidance and 

Application Kit (June 2012), if the applicant is a fire department, 

the department must agree to provide information, through 

established reporting channels, to NFIRS for the period covered by the assistance. If a fire department does not currently 

participate in the incident reporting system and does not have 

the capacity to report at the time of the award, the department 

must agree to provide information to the system for a 12-month 

period that begins as soon as the department develops the capacity to report. See http://www.fema.gov/library/viewRecord.

do?id=6007 (fg_2012_afg_program_guidance.pdf).

3

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

in 2,540 civilian fire deaths, 13,778 civilian fire injuries, 

and $7.1 billion dollars in property damage each year. Of 

these NFPA residential structure fire and loss estimates, 72 

percent of the fires, 58 percent of the deaths, 57 percent 

of the injuries and 58 percent of the dollar loss were 

reported to NFIRS during this three-year period.

Table 1. NFPA Estimates of Residential Structure Fires and Losses (2010-2012)

Year Residential 

Structure Fires

Residential 

Structure Fire Deaths

Residential 

Structure Fire Injuries

Residential 

Structure Fire Dollar Loss

(in millions)

2010 384,000 2,665 13,800 $7,079

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

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

Source: NFPA, “Fire Loss in the United States,” 2010-2012.

The 2010-2012 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 2010 to 2012, the NFPA survey produced an annual 

average estimate of 98,667 nonresidential structure fires 

resulting in 82 civilian fire deaths, 1,473 civilian fire 

injuries and $2.6 billion dollars in property damage. Of 

these NFPA nonresidential structure fire and loss estimates, 76 percent of the fires, 95 percent of the deaths, 

50 percent of the injuries and 73 percent of the dollar loss 

were reported to NFIRS during this three-year period.

Table 2. NFPA Estimates of Nonresidential Structure Fires and Losses (2010-2012)

Year Nonresidential 

Structure Fires

Nonresidential 

Structure Fire Deaths

Nonresidential 

Structure Fire Injuries

Nonresidential 

Structure Fire Dollar Loss 

(in millions)

2010 98,000 90 1,620 $2,637

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

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

Source: NFPA, “Fire Loss in the United States,” 2010-2012.

National Estimates Overview

National estimates presented in USFA’s Topical Fire Report 

Series (Volume 15) are based on 2010-2012 NFIRS data, 

structure fire-loss estimates from 2010-2012 NFPA’s annual 

surveys and 2010-2012 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.4

 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.

4

 For detailed information regarding NFPA’s survey methodology, see NFPA’s report on “Fire Loss in the United States,” http://

www.nfpa.org/~/media/Files/Research/NFPA%20reports/

Overall%20Fire%20Statistics/osfireloss.pdf.

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, structure, vehicle, outside and other fires.5

 Generally, these national estimates 

are 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.6

 This methodology is the 

accepted practice of national fire data analysts. 

5

 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/6906FADB2C

E149488FB5103F4A750A05.ashx.

6

 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. 
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 3

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.7

 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 2010-2012 NFIRS structure fire data 

show that, by and large, the majority (94 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. 

Residential Buildings 

Table 3 shows the raw numbers of residential building 

fires and losses reported to NFIRS from 2010 to 2012.

Table 3. Residential Building Fires and Losses Reported to NFIRS (2010-2012)

Year Residential 

Building Fires

Residential 

Building Fire Deaths

Residential 

Building Fire Injuries

Residential 

Building Fire Dollar Loss 

(in millions)

2010 271,085 1,472 7,899 $3,966

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

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

Source: USFA, 2010-2012 NFIRS. 7

7

 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

Table 4 shows the raw numbers of residential structure 

fires and losses reported to NFIRS from 2010 to 2012. 

On average from 2010 to 2012, 96 percent of residential 

structure fires, 97 percent of associated deaths, 97 percent of injuries and 96 percent of dollar loss reported to 

NFIRS occurred in residential buildings.

Table 4. Residential Structure Fires and Losses Reported to NFIRS (2010-2012)

Year Residential 

Structure Fires

Residential 

Structure Fire Deaths

Residential 

Structure Fire Injuries

Residential 

Structure Fire Dollar Loss 

(in millions)

2010 287,476 1,536 8,207 $4,224

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

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

Source: USFA, 2010-2012 NFIRS.

Nonresidential Buildings

Table 5 shows the raw numbers of nonresidential building fires and losses reported to NFIRS from 2010 to 2012. 

Table 5. Nonresidential Building Fires and Losses Reported to NFIRS (2010-2012)

Year Nonresidential 

Building Fires

Nonresidential 

Building Fire Deaths

Nonresidential 

Building Fire Injuries

Nonresidential 

Building Fire Dollar Loss 

(in millions)

2010 67,426 76 669 $1,636

2011 67,885 83 702 $1,856

2012 64,926 53 608 $1,859

Source: USFA, 2010-2012 NFIRS.

Table 6 shows the raw numbers of nonresidential 

structure fires and losses reported to NFIRS from 2010 

to 2012. On average, about 89 percent of nonresidential 

structure fires, 91 percent of deaths, 89 percent of injuries and 93 percent of dollar loss reported to NFIRS from 

2010 to 2012 occurred in nonresidential buildings.

Table 6. Nonresidential Structure Fires and Losses Reported to NFIRS (2010-2012)

Year Nonresidential 

Structure Fires

Nonresidential 

Structure Fire Deaths

Nonresidential 

Structure Fire Injuries

Nonresidential 

Structure Fire Dollar Loss

(in millions)

2010 77,790 84 783 $1,796

2011 78,323 94 810 $2,011

2012 69,611 54 634 $1,939

Source: USFA, 2010-2012 NFIRS.

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.8

 USFA uses these 

8

 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.

national building fire estimates in the Topical Fire Report 

Series, Fire Estimate Summary Series, and various other 

fire data reports.9

 Tables 7 and 8 present USFA’s national 

estimates for residential and nonresidential building fires 

and losses, respectively.

9

 USFA’s Fire Estimate Summary Series as well as 2003-2012 

national estimates of residential and nonresidential building fires 

and losses are published at http://www.usfa.fema.gov/statistics/

estimates/index.shtm. USFA’s Topical Fire Report Series and various other fire data reports are available at http://www.usfa.fema.

gov/statistics/.
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 5

Table 7. USFA’s National Estimates of Residential Building Fires and Losses (2010-2012)

Year Residential 

Building Fires

Residential 

Building Fire Deaths

Residential 

Building Fire Injuries

Residential 

Building Fire Dollar Loss 

— Adjusted to 

2012 Dollars

(in millions)

2010 362,100 2,555 13,275 $6,999

2011 364,500 2,450 13,900 $6,789

2012 374,000 2,385 13,050 $7,103

Source: USFA, 2010-2012 Fire Estimate Summary Series.

Table 8. USFA’s National Estimates of Nonresidential Building Fires and Losses (2010-2012)

Year Nonresidential 

Building Fires

Nonresidential 

Building Fire Deaths

Nonresidential 

Building Fire Injuries

Nonresidential 

Building Fire Dollar Loss 

— Adjusted to 

2012 Dollars

(in millions)

2010 84,900 80 1,375 $2,528

2011 85,400 80 1,100 $2,486

2012 92,800 65 1,450 $2,472

Source: USFA, 2010-2012 Fire Estimate Summary Series.

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 (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 “National Fire Incident Reporting System Complete 

Reference Guide.”10 Table 9 identifies the NFIRS data 

elements that are used most often in fire data analyses in 

the topical reports produced by USFA.

10 “NFIRS Complete Reference Guide,” USFA, January 2013, 

http://www.nfirs.fema.gov/documentation/reference/.
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 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 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 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 spread11 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 2013.

11In 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 mid-level 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 mid-level 

cause groupings using a hierarchy of definitions. A fire 

11 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 contains no missing data values.

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.”12

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 2010-2012 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 

12 USFA’s detailed “Structure Fire Cause Methodology” is available at www.usfa.fema.gov/fireservice/nfirs/tools/fire_cause_

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

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 38.4 percent of reported residential 

building fires from 2010 to 2012; another 17.9 percent 

of reported fires had cause unknown. Thus, the percent 

of fires that had their cause reported was 100 minus 17.9 

equals 82.1 percent. With the unknown causes proportioned like the known causes, the adjusted percent of 

cooking fires in residential buildings can then be computed as 38.4 divided by 82.1 equals 46.8 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.

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

Fires Reported to NFIRS (2010-2012)

Data Element 2010

Percent Unknown

2011

Percent Unknown

2012

Percent Unknown

Area of fire origin 11.6 11.8 13.6

Heat source 34.4 34.7 39.2

Item first ignited 34.6 35.2 37.8

Factors contributing to ignition 25.5 26.0 28.4

Presence of detectors 29.8 30.2 30.5

Presence of AES 8.3 8.5 9.0

Fire cause 18.0 18.4 17.0

Source: NFIRS.

Note: For 2012, increases in the percent unknowns of heat source and factors contributing to ignition may be 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 108, https://www.nfirs.fema.gov/documentation/design/2012/NFIRS_5.0_Design_Documentation_1-2012.pdf).
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 8

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

Fires Reported to NFIRS (2010-2012)

Data Element 2010 

Percent Unknown

2011 

Percent Unknown

2012 

Percent Unknown

Area of fire origin 16.5 16.6 18.9

Heat source 39.8 40.4 45.2

Item first ignited 40.8 41.6 43.9

Factors contributing to ignition 27.9 28.0 31.2

Presence of detectors 19.5 20.2 20.0

Presence of AES 9.6 9.9 10.5

Fire cause 38.0 37.0 35.9

Source: NFIRS.

Note: For 2012, increases in the percent unknowns of heat source and factors contributing to ignition may be 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 108, https://www.nfirs.fema.gov/documentation/design/2012/NFIRS_5.0_Design_Documentation_1-2012.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 which cause substantial loss.

Identifying Large Outliers

If the incident record clearly contains outliers, it is generally recommended to exclude it 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 the NFIRS system and using the 

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 the coding of the data.

The “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. The topics include 

the NFIRS 5.0 data structure, general quality assurance 

issues, and definitions and parameters of common fire 

analyses (e.g., residential building fires or fires by a specific cause). The methods, techniques and considerations 

discussed are those used by USFA analysts and 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.

The USFA’s “Structure Fire Cause Methodology” provides 

a detailed description of the cause hierarchy methodology and the technical hierarchy itself. 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.
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 9

Resource List

1) “National Fire Incident Reporting System Complete Reference Guide,” USFA, January 2013, http://www.nfirs.fema.

gov/documentation/reference/.

2) “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.

3) 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.

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

downloads/pdf/statistics/national_estimate_methodology.pdf.

5) USFA’s “Structure Fire Cause Methodology,” http://www.usfa.fema.gov/fireservice/nfirs/tools/fire_cause_category_

matrix.shtm.

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

statistics/data_sources_methodology.pdf.

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

publications/fa-266.pdf.