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 17)

June 2016
U.S. Fire Administration

Mission Statement

We provide National leadership to foster a solid foundation for 

our fi re 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 17)

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 22 million nonfire incident records 

are added to the database each year. In 2014, the most 

recent year of data available, 20,527 fire departments 

reported fire incidents to NFIRS. Across participating 

entities, 68 percent of U.S. fire departments reported fire 

incidents to NFIRS in 2014.1

 With at least 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 2012-

2014, NFIRS 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).

1

 For 2014, NFPA estimated that there were 29,980 fire departments in the U.S. Source: NFPA, U.S. Fire Department Profile 2014, http://

www.nfpa.org/research/reports-and-statistics/the-fire-service/administration/us-fire-department-profile, January 2016.

2

 From the fiscal year (FY) 2015 Assistance to Firefighters Grant (AFG) Notice of Funding Opportunity (NOFO) — 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, 

fire departments that receive funding under this program must agree to provide information to NFIRS for the period covered by the 

assistance. If a recipient does not currently participate in NFIRS and does not have the capacity to report at the time of the award, that 

recipient must agree to provide information to the system for a 12-month period commencing ASAP after it develops the capacity 

to report. Capacity to report to NFIRS must be established prior to the termination of the one-year performance period. 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 the FY 2015 AFG NOFO at https://www.fema.gov/media-library/assets/documents/110252.

3

 For detailed information regarding NFPA’s survey methodology, see NFPA’s report “Fire Loss in the United States During 2014,” 

September 2015, 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

The 2012-2014 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 2012 to 2014, the NFPA survey produced an 

annual average estimate of 384,800 residential structure 

fires resulting in 2,660 civilian fire deaths, 12,650 

civilian fire injuries, and $7.1 billion in property damage 

each year.4

 Of these NFPA residential structure fire and 

loss estimates, 68 percent of fires, 54 percent of deaths, 

56 percent of injuries, and 60 percent of dollar losses 

were reported to NFIRS during this three-year period.

Table 1. NFPA Estimates of Residential Structure Fires and Losses (2012-2014)

Year Residential 

Structure Fires

Residential 

Structure Fire 

Deaths

Residential 

Structure Fire 

Injuries

Residential 

Structure Fire 

Dollar Loss

(in $M)

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

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

2014 386,500 2,795 12,175 $6,992

Source: NFPA, “Fire Loss in the United States,” 2012-2014.

The 2012-2014 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 2012 to 2014, the NFPA 

survey produced an annual average estimate of 102,500 

nonresidential structure fires resulting in 65 civilian 

fire deaths, 1,425 civilian fire injuries, and $2.7 billion 

in property damage.5

 Of these NFPA nonresidential 

structure fire and loss estimates, 70 percent of fires, 101 

percent of deaths, 44 percent of injuries, and 92 percent 

of dollar losses were reported to NFIRS during this 

three-year period.

Table 2. NFPA Estimates of Nonresidential Structure Fires and Losses (2012-2014)

Year Nonresidential 

Structure Fires

Nonresidential 

Structure Fire 

Deaths

Nonresidential 

Structure Fire 

Injuries

Nonresidential 

Structure Fire 

Dollar Loss 

(in $M)

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

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

2014 107,500 65 1,250 $2,854

Source: NFPA, “Fire Loss in the United States,” 2012-2014.

National Estimates Overview

National estimates presented in USFA’s Topical Fire 

Report Series (Volume 17) are based on 2012-2014 

NFIRS data, structure fire loss estimates from 2012-2014 

NFPA’s annual surveys, and 2012-2014 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.

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 2014,” 

September 2015, 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 3

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 

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 directly from NFIRS data.

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 and budgetary 

considerations — 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 2012-2014 NFIRS structure fire 

data show that, by and large, the majority (97 percent) 

of structure fires occurred 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 2012 to 2014.

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.

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) to 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 “Fire in the United States 2004-2013,” 17th edition, March 

2016, https://www.usfa.fema.gov/downloads/pdf/publications/fius17th.pdf.
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 4

Table 3. Residential Building Fires and Losses Reported to NFIRS (2012-2014)

Year Residential 

Building Fires

Residential 

Building Fire Deaths

Residential 

Building Fire Injuries

Residential 

Building Fire 

Dollar Loss 

(in $M)

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

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

2014 267,224 1,481 7,071 $4,444

Source: USFA, 2012-2014 NFIRS.

Table 4 shows the raw numbers of residential structure 

fires and losses reported to NFIRS from 2012 to 2014. 

On average from 2012 to 2014, 98 percent of residential 

structure fires, 99 percent of associated deaths, 99 

percent of injuries, and 99 percent of dollar losses 

reported to NFIRS occurred in residential buildings.

Table 4. Residential Structure Fires and Losses Reported to NFIRS (2012-2014)

Year Residential 

Structure Fires

Residential 

Structure Fire 

Deaths

Residential 

Structure Fire 

Injuries

Residential 

Structure Fire 

Dollar Loss 

(in $M)

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

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

2014 272,129 1,496 7,134 $4,504

Source: USFA, 2012-2014 NFIRS.

Nonresidential Buildings

Table 5 shows the raw numbers of nonresidential building fires and losses reported to NFIRS from 2012 to 2014.

Table 5. Nonresidential Building Fires and Losses Reported to NFIRS (2012-2014)

Year Nonresidential 

Building Fires

Nonresidential 

Building Fire 

Deaths

Nonresidential 

Building Fire 

Injuries

Nonresidential 

Building Fire 

Dollar Loss 

(in $M)

2012 64,926 53 608 $1,859

2013 66,592 65 576 $2,114

2014 69,025 71 631 $2,926

Source: USFA, 2012-2014 NFIRS.

Table 6 shows the raw numbers of nonresidential 

structure fires and losses reported to NFIRS from 2012 to 

2014. On average, 93 percent of nonresidential structure 

fires, 94 percent of deaths, 95 percent of injuries, and 94 

percent of dollar losses reported to NFIRS from 2012 to 

2014 occurred in nonresidential buildings.

Table 6. Nonresidential Structure Fires and Losses Reported to NFIRS (2012-2014)

Year Nonresidential 

Structure Fires

Nonresidential 

Structure Fire 

Deaths

Nonresidential 

Structure Fire 

Injuries

Nonresidential 

Structure Fire 

Dollar Loss

(in $M)

2012 69,611 54 634 $1,939

2013 71,450 70 611 $2,197

2014 74,556 78 657 $3,178

Source: USFA, 2012-2014 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 (2012-2014)

Year Residential 

Building Fires

Residential 

Building Fire

Deaths

Residential 

Building Fire 

Injuries

Residential 

Building Fire 

Dollar Loss — 

Adjusted to 

2014 Dollars

(in $M)

2012 374,000 2,385 13,050 $7,324

2013 380,300 2,755 12,450 $6,987

2014 379,500 2,765 12,075 $6,900

Source: USFA, Fire Estimate Summary Series (2005-2014).

Table 8. USFA’s National Estimates of Nonresidential Building Fires and Losses (2012-2014)

Year Nonresidential 

Building Fires

Nonresidential 

Building Fire 

Deaths

Nonresidential 

Building Fire 

Injuries

Nonresidential 

Building Fire 

Dollar Loss — 

Adjusted to 

2014 Dollars

(in $M)

2012 92,800 65 1,450 $2,549

2013 93,700 65 1,425 $2,501

2014 99,500 60 1,200 $2,628

Source: USFA, Fire Estimate Summary Series (2005-2014).

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, https://www.usfa.fema.gov/downloads/pdf/statistics/

national_estimate_methodology.pdf.

11 USFA’s Fire Estimate Summary Series as well as 2003-2014 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 

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

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

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, 47 

percent of fatal fires in residential buildings reported 

from 2012 to 2014 did 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. Reporting 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 41.3 percent of reported residential building fires from 

2012 to 2014; another 16.4 percent of reported fires had 

cause unknown. Thus, the percent of fires that had their 

cause reported was 100 minus 16.4 which equals 83.6 

percent. With the unknown causes apportioned like the 

known causes, the adjusted percent of cooking fires in 

residential buildings can then be computed as 41.3 divided 

by 83.6 which equals 49.4 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. For 2012 to 2014, the percentages of 

unknown values for each data element in Tables 10 and 

11 are relatively consistent from one year to the next.

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 8

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

Building Fires Reported to NFIRS (2012-2014)

Data Element

2012 2013 2014

Percent Unknown Percent Unknown Percent Unknown

Area of fire origin 13.6 12.7 13.1

Heat source 39.2 37.7 37.6

Item first ignited 37.8 37.1 37.7

Factors contributing to 

ignition 28.4 28.4 28.6

Presence of detectors 30.5 30.0 30.2

Presence of AES 9.0 8.4 8.7

Fire cause 17.0 16.1 16.1

Source: NFIRS.

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

Fires Reported to NFIRS (2012-2014)

Data Element

2012 2013 2014

Percent Unknown Percent Unknown Percent Unknown

Area of fire origin 18.9 18.3 18.9

Heat source 45.2 43.3 42.7

Item first ignited 43.9 43.1 44.1

Factors contributing to 

ignition 31.2 30.8 30.8

Presence of detectors 20.0 19.4 19.9

Presence of AES 10.5 10.2 10.4

Fire cause 35.9 35.2 34.1

Source: NFIRS.

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 
Data Sources and National Estimates Methodology Overview for the U.S. Fire Administration’s Topical Fire Report Series Page 9

assurance 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 “Fire in the United States 2004-2013” is a 

statistical portrait of the national fire problem and 

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 databased analyses.

Resource List

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

publications/fa-266.pdf.

“Fire in the United States 2004-2013,” 17th edition, USFA, March 2016, https://www.usfa.fema.gov/downloads/pdf/

publications/fius17th.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, https://

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.