Wildfire

Report

Series

National Fire Data Center

16825 S. Seton Ave.

Emmitsburg, MD 21727

usfa.fema.gov

Analysis of NFIRS Incidents in 

the Wildland Urban Interface

An Analysis of California NFIRS Data, 2009-2011 

April 2021

Summary

The wildland urban interface (WUI) is the area where housing and natural vegetation meet or intermingle. In the 

coterminous United States, between 1990 and 2010, the size of the WUI increased by 33% to 770,000 km2 (190.3 

million acres), and the number of homes in the WUI increased by 41% to 43.4 million (Radeloff et al., 2018). WUI 

areas may be the subject of increased attention due to the challenges posed by wildfires and because of recent 

increases in the number of structures destroyed, area burned and estimated damages annually by wildland fire.

Using National Fire Incident Reporting System (NFIRS) data, this paper examines the fire incidents in WUI 

areas in California in terms of travel time, loss measures and fire cause for the years 2009 to 2011 and 

compares those incidents to those outside WUI areas. California was chosen as the methodology test set as 

it experiences high levels of both wildfires and fires in the WUI, especially in recent years. Additionally, this 

paper presents a novel method for identifying incidents that occur in the WUI that has subsequently been 

adopted by the National Fire Data Center (NFDC): NFIRS data was geocoded and combined with existing U.S. 

Forest Service (USFS) WUI shapefiles to identify incidents that occurred in the WUI. This dataset creates a 

substantial new opportunity for linking local fire department incident responses and wildland fires.

The goals of the study were twofold: first, to develop a method to identify fires in the WUI, and second, once 

identified, to use NFIRS fire data to identify substantive differences, if any, between WUI and non-WUI areas 

to better understand how the risk from fire in the WUI may be mitigated. It is important to note that the 

WUI is a geographic area; a fire in the WUI can be any type of fire and not necessarily related to a wildfire 

or wildland fire. The analysis examines all types of fire incidents, including, but not limited to, wildland fires. 

Some of the conclusions drawn about fires in WUI areas may shape recommendations for how to mitigate 

the risk from fire in the WUI.

NFIRS-reported losses in the California WUI are substantial. California averages almost $154.6 million per year 

in building and structure losses in WUI areas. Mobile structure fires, such as mobile homes, in the WUI incur an 

additional $3 million per year in property damage; vehicle fire incidents in WUI areas add $19.4 million per year.

Analysis showed:

ĵ Overall, travel times are higher in WUI areas than in urban areas. Median travel times are 20% to 40% 

higher depending on the incident type, and mean travel times are 24% to 53% longer.

ĵ Increased travel times may have an impact on the losses in WUI areas, which are generally higher on a 

per-incident basis than in urban areas. 

Ý Imputed dollar loss per incident is 12% higher in WUI areas than urban areas for building and other 

structure fires (excluding contained fires), 9% higher for mobile structure fires, and 15% higher for 

vehicle fires. 
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 2

Ý Casualty rates for both firefighters and civilians appear to be higher in WUI areas than in urban areas. 

For building and other structure fires, firefighter injury rates are 14% higher in WUI areas than in urban 

areas. For the same fires, civilian death rates are 20% higher. While not as pronounced, casualty rates for 

mobile structure fires are also higher in WUI areas than in urban areas.

ĵ Fire cause in WUI areas is more likely to be heating, cooking, appliances and open flame than in urban 

areas for building/non-building structures and mobile structures. Interestingly, among fires confined to their 

noncombustible container, heating is more likely to be the cause of fire in WUI areas than in either urban or 

rural areas. While more analysis is needed, this may suggest that heating fires in WUI areas are more likely 

to breach their noncombustible container while awaiting a fire department response.

ĵ Although the data examined did not include a large number of exposure fires (fires caused by another fire), 

an exposure fire in the WUI area is twice as likely to have been sparked by a vegetation fire than in urban 

areas. Exposure fires sparked by vegetation fires are also twice as common in rural areas as urban areas.

National Fire Incident Reporting System incidents

NFIRS represents the world’s largest national annual database of fire department incident information. Each year, 

approximately 24,000 fire departments from all 50 states, the District of Columbia, many Native American tribal 

authorities and the Department of Defense voluntarily report data on over 1 million fires and over 28 million other 

fire department-responded incidents such as hazardous material incidents or smoke scares.1 NFIRS is not a census 

of all fire department-responded incidents, and it is not based on a statistically derived sample. Among other issues 

that prevent NFIRS from being a complete source for fire department incident data are reporting deadlines, data 

access and budgetary considerations.

For fire incidents, as with other NFIRS fire department-responded incidents, NFIRS raw totals do not reflect the whole 

of the U.S. fire problem; NFIRS contains incident data derived from voluntary reporting of fire incidents in the U.S. 

With the wealth of fire incident data contained in NFIRS, however, the U.S. Fire Administration (USFA) believes it is 

possible to harness NFIRS data for analyses of WUI-related fire incidents.

National Fire Incident Reporting System

The Federal Fire Prevention and Control Act of 1974 (P.L. 93-498) authorizes the USFA’s NFDC to gather and analyze 

information on the magnitude of the nation’s fire problem as well as its detailed characteristics and trends. The Act 

further authorizes the USFA to develop uniform data reporting methods and to encourage and assist state agencies 

in developing and reporting data. In order to carry out the intentions of the Act, the NFDC established NFIRS.

About the National Fire Incident Reporting System 

NFIRS has 2 objectives: to help state and local governments develop fire reporting and analysis capability for their 

own use, and to obtain data that can be used to more accurately assess and subsequently combat the fire problem 

at a national level. To meet these objectives, the USFA has developed NFIRS data collection standards. This NFIRS 

package, maintained by USFA, includes forms, a coding structure for data processing purposes, a standard system 

specification, manuals, computer software and procedures, and documentation for using the system. 

Generally, NFIRS collects fire incident data from state fire data systems. The state systems, in turn, collect data from their 

individual fire departments. State participation in NFIRS is voluntary and the guidelines for departmental participation 

within each state are determined by the state fire marshal’s office or the equivalent agency. These guidelines can vary 

significantly from state to state. In most states, reporting by local departments is not mandatory; the departments that 

report are willing to participate and can afford the additional commitment necessary to collect the data. 

Participating local fire departments fill out the incident reports as emergency responses occur. They forward the 

completed incidents via paper forms or digital transactions to their state reporting authority and to the USFA where 

the data is validated and consolidated into a single computerized database. 

1

National Fire Incident Reporting System (NFIRS) data from the Department of Defense is not released in the NFIRS Public Data Release.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 3

The database is used to answer questions about the nature and causes of injuries, deaths and property losses 

resulting from fires. This information is disseminated through a variety of means to the public as well as to 

government and private organizations. 

Representativeness of National Fire Incident Reporting System data

The percentage of fire departments participating in NFIRS varies from state to state, with some states not participating 

at all in some years. Even in this case, individual fire departments are currently able to submit incident data directly 

to the USFA. Thus, all fire departments in the country can participate, regardless of whether the state in which they 

are located participates. As the USFA has determined in past studies for the Office of Management and Budget 

(Federal Emergency Management Agency, 2011), the distribution of participants is reasonably representative of the 

entire nation, even though it is not a scientifically selected sample. The data set is so large and reasonably distributed 

geographically and by size of community that fire data analysts use the data to analyze the U.S. fire problem on a 

national level. 

Most of the NFIRS data exhibit stability from one year to another without radical changes. Results based on the 

full data set are generally similar to those based on part of the data, another indication of data reliability (U.S. Fire 

Administration [USFA], National Fire Data Center [NFDC], 2014).

The wildland urban interface

The WUI has received considerable attention because of recent increases in the number of deaths, structures 

destroyed, area burned and estimated costs by wildland fire as reported by the National Interagency Fire Center 

(National Interagency Fire Center [NIFC], 2019; NIFC, 2018). There have been a number of high-profile and costly 

wildland fires in recent years, including the 2019 Walker and Kincade fires in California that had a total estimated cost 

of $112.7 million (NIFC, 2019) and the 2018 Mendocino Complex, Carr, Camp, Woolsey, Ferguson, County and Delta 

fires in California that had a total estimated cost of $820.6 million (NIFC, 2018). 

These wildfires are frequently affecting areas beyond the traditional wildlands as residential growth has expanded 

into these areas. This area, the WUI, creates new challenges as the close proximity of houses and wildland vegetation 

increases fire risk to people, structures and firefighters (Calkin et al., 2014). Fires in the WUI are more difficult to fight 

(Radeloff et al., 2018), which may result in increased property loss. 

The problem is expanding quickly. Using U.S. Census data, National Land Cover Data and WUI definitions as stated in 

the Federal Register, researchers determined that the WUI has grown over the last several decades (Figure 1). From 

1990 to 2010, the WUI grew from 30.8 million to 43 million homes and increased from 143.6 million acres to 190.3 

million acres (Radeloff et al., 2018).2

2Data converted from km2

 to acres.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 4

Figure 1. Growth rate of homes in the WUI 1990-2010 by county (in percent) 

Source: USFS, https://www.nrs.fs.fed.us/news/release/wui-increase.

NFIRS data offers a unique perspective in examining some of the specific challenges in addressing fire in the WUI 

because of its abundance of incident-level reporting. The data, however, comes with its own challenges as discussed 

in the section below, National Fire Incident Reporting System and wildland urban interface data challenges.

Terminology

One of the challenges in understanding and analyzing fire incident and WUI data is inconsistent or confusing 

terminology. In the fire community, there are no standardized definitions for the basic terms of wildfires, wildland 

fires, WUI fires and WUI areas. Each group or agency that works with wildland fires uses its own definitions, in large 

part based on the way it collects data and how the agency is involved in the wildfire arena. Various definitions exist, 

and a further exploration of this topic is included in the Appendix. Most definitions are qualitative and descriptive. 

While the data is taken from NFIRS data and USFA has its own definitions of WUI and WUI-related terms, the definition 

of WUI that is most suitable for geospatial analysis is based on housing and population density published by the U.S. 

Department of Agriculture and the U.S. Department of the Interior in the Federal Register (Urban Wildland Interface 

Communities Within the Vicinity of Federal Lands that Are at High Risk from Wildfire, 2001). It defines WUI as an 

area where housing density is greater than 1 home per 40 acres, either intermixed with or in proximity to wildland 

vegetation. It is the definition used in this report. With geospatial data, 2 additional terms are used: intermix and 

interface. Areas where houses and wildland vegetation intermingle are referred to as “intermix WUI”; areas where 
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 5

houses abut wildland vegetation are referred to as “interface WUI” (Radeloff et al., 2005). For purposes of analysis, 

this paper does not address any differences between interface or intermix WUI. Both groups are combined into the 

overall WUI dataset.

The following additional definitions have been adopted for this paper: Wildfires are a fire type involving vegetative 

or natural fuels, and wildland is a low-density population area where any kind of incident could occur. Wildlands 

may overlap with rural low-density population areas. Wildfires, as defined here, can occur in any land use area.

National Fire Incident Reporting System and wildland urban interface data challenges

There are many challenges in analyzing NFIRS data in the WUI, including missing incidents, data quality, the use of 

the data element “Area Type” to identify WUI fires, and missing loss data. These and other issues are explored more 

thoroughly in the USFA’s preliminary review of NFIRS wildfire data (USFA, NFDC, 2020).

Missing incidents. Many of the federal agencies and other groups that combat wildland fires do not report to NFIRS. 

For example, the USFS, one of the primary responders to wildland fires, does not report their data to NFIRS. This 

underreporting of wildland fires can be significant. Other federal nonreporting agencies include U.S. Bureau of Land 

Management, U.S. Fish and Wildlife Service, U.S. National Park Service and U.S. Bureau of Indian Affairs.

Local jurisdictions may underreport as well. A 2017 study of satellite-detected fires within areas of local jurisdiction 

in California found that only 32% of them could be identified in the NFIRS Public Data Release (PDR) file (Butry & 

Thomas, 2017). Further study by USFA of satellite-detected fires found that as many as 97% of them could not be 

matched to a fire (including prescribed fires and unauthorized burning) in NFIRS data (USFA, 2020).

Wildland data quality. The Wildland Fire Module, used to describe certain types of outside fires including wildfires 

more completely, is an optional module in NFIRS. It may be omitted if a department elects to record incident data via 

the Fire Module thereby leading to incomplete reporting of wildland-related fire data. In addition, for agencies that 

use the National Wildfire Coordinating Group Incident Status Summary Form (ICS-209) to report on wildfire incidents, 

there are data element differences between the NFIRS Wildland Module and the ICS-209, making a translation from 

one system to the other an imperfect fit.3

This incomplete reporting of wildland-related data is a primary reason that information in the Wildland Fire module 

is generally not reported in USFA annual statistics, and thus is not regularly reviewed for data quality. This results 

in occasional spectacularly incorrect entries in that module. For example, an incident from a department in Texas 

(TXWB701) on 12/9/2016 recorded 1,000,000,000 acres burned, and an incident from a department in Iowa (IA77008) 

on 7/6/2016 recorded 9,999,999 acres burned (USFA, 2016). These incidents are obvious incorrect entries. 

Area type. The Wildland Fire Module has a field (“Area Type”) that includes a selection of “Urban-wildland interface 

area” that could be used to help identify WUI incidents. But as the wildland module is typically only used to record 

wildfires, other incidents that occur in the WUI, such as structure and vehicle fires, will not be coded with this area type. 

For the reasons above, this analysis will use only data that is present in the Basic Module (required data) in NFIRS 

and will ignore the data present in the Wildland Fire Module (optional data). The approach combines incidents in the 

Basic Module with their geolocation and existing WUI shapefiles to identify WUI incidents. 

Dollar loss. There are further challenges in analyzing dollar loss data as reported to NFIRS. The NFIRS data on 

property and content losses are frequently underreported. Between 2009 and 2015, there were 6.4 million primary 

fire incidents4, but no loss data was reported for 24% of these incidents. Additionally, the loss reported for an 

additional 47% of primary fire incidents was zero (USFA, 2017). 

3The Incident Status Summary Form (ICS-209 WF) is intended to be used when an incident reaches a certain threshold where it becomes significant 

enough to merit special attention, require additional resource support needs, or cause media attention, increased public safety threat, etc. It 

is designed to provide a “snapshot in time” to effectively move incident decision support information where it is needed. It contains the most 

accurate and up-to-date information available at the time it is prepared. Multiple ICS-209 forms may be submitted during the course of an 

incident.

4NFIRS data distinguishes between “primary” and “aid” fire incidents. Primary incidents are those incidents where the reporting department has 

the primary or “first due” responsibility for the incident. “Aid” incidents are those where another department assists the primary department 

with additional manpower or equipment.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 6

To address this underreporting, USFA has developed a method for estimating dollar loss where the data is missing 

or suspected incorrect. The method involves identifying cohorts of incidents where dollar loss is reported and using 

characteristics of those cohorts to apportion estimates for similar incidents where dollar loss is not reported (USFA, 2017).

To develop a more complete understanding of the WUI impact, both reported and estimated loss are used as part 

of this analysis.

Casualties. Other sources may report or record casualties, e.g., USFA’s own annual firefighter fatality reports. The 

casualty data used in these analyses come exclusively from the fire incident data as reported to NFIRS.

Method

Wildland urban interface groups and classification

USFS shapefiles are the basis for the geographic description of the WUI. A shapefile is simply a file format for storing 

the “shape” or geometric location of geographic features. The USFS shapefiles not only store the shape (points, lines 

or polygons/areas) and location (latitude and longitude) of geographic characteristics, but they also classify each 

shape as belonging to an urban, WUI or rural area.

The USFS calculates WUI classifications by combining Census Block5, Land Cover6, and Protected Area datasets 

(Radeloff et al., 2017).7 Samples of these datasets are shown in Figure 2.

Figure 2. USFS Shapefile input datasets

Tiger Census Block

(Census)

National Land Cover Database

(U.S. Geological Survey [USGS])

Protected Areas Database

(USGS, Radeloff et al.)

The specific definition of the WUI used in this analysis was developed from census-block level data to assess housing 

density (left dataset in Figure 2) and land use maps to determine the type and size of vegetation within each census 

block (middle dataset in Figure 2). If a census block has at least 1 home per 40 acres and over half of the census block’s 

land use is wildland vegetation, the census block is labeled as “Intermix WUI.” If a census block has at least 1 home 

per 40 acres and is within 1.5 miles of an area (over 1,235 acres) comprised of at least 75% wildland vegetation, it is 

labeled as “Interface WUI” (Stewart et al., 2007). 

5https://www.census.gov/geographies/mapping-files/time-series/geo/tiger-line-file.html

6https://www.usgs.gov/centers/eros/science/national-land-cover-database?qt-science_center_objects=0#qt-science_center_objects

7https://maps.usgs.gov/padus/
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 7

Figure 3. The WUI definition

Is housing density > 1 housing unit per 40 acres?

Are > 50% of pixels in census block

wildland vegetation?

Intermix WUI

Yes No

Is it within 1.5 miles of large area with

> 75% wildland vegetation?

Interface WUI

Yes No

Yes No

Source: Stewart et al., 2007.

The USFS classifies census blocks into multiple categories (Radeloff et al., 2005). For this analysis, all intermix and 

interface classifications were combined as a WUI group; all high and medium density population, no vegetation 

classifications were combined as an Urban group; all low density population to uninhabited density no vegetation 

and all vegetation density classification were combined as a Rural group (Table 1).

Table 1. Grouping of WUI classifications

WUI classification Area type

High Density Interface

High Density Intermix

Medium Density Interface

Medium Density Intermix

Low Density Interface

Low Density Intermix

WUI

High Density No Vegetation

Medium Density No Vegetation Urban

Low Density No Vegetation

Very Low-Density No Vegetation

Very Low-Density Vegetation

Uninhabited Vegetation

Uninhabited No Vegetation

Rural
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 8

Approach to analyzing wildland urban interface and National Fire Incident Reporting System data

Combining wildland urban interface and National Fire Incident Reporting System data

USFS shapefiles are available for 1990, 2000 and 2010. The most recent shapefile, from 2010, was used for this paper. 

In this exploratory analysis, the state of California was selected due to the prevalence of wildfires and the ability to 

compare to other published studies. To be consistent with the shapefile data, all NFIRS fire incidents in California for 

the years 2009 to 2011 were selected for analysis.8 This date range provides a sufficient population of data for further 

analysis. While all California fire incidents for 2009 to 2011 were included in the master dataset, subsets of the data 

were used where appropriate in the analyses.

Basic Module incident data in NFIRS includes address or location information but does not typically include geographic 

coordinates. This lack of location-specific coordinate data hampers the utility of NFIRS data in geospatial analyses. As 

a workaround, the GEOCODE Procedure in SAS 9.4 was used to identify the latitude and longitude for each incident.9

The precision of geographical coordinates returned by the geocoder is limited by the quality of the input information 

and the sophistication of the geocoding algorithm.

The USFS shapefiles were joined with NFIRS geocoded data to identify the WUI classification for each incident using 

an R-based “point-in-polygon” calculation.10,11 This approach to incorporating geographic data in NFIRS analyses has 

been subsequently employed by the USFA in its own analyses of NFIRS WUI data.

While NFIRS records location information for an incident, the incident locations are not always able to be geocoded 

accurately. Approximately 3% of NFIRS incidents did not contain sufficient information to be geocoded and were 

discarded. Some incidents that were geocoded were matched to USFS polygons with a WUI classification of “water,” 

such as rivers or lakes, or were not matched to any USFS polygons. These NFIRS incidents were also removed from 

the analysis. While better address and location data or more accurate geocoding would increase the number of 

incidents available for analysis, the measures of central tendency of the overall distribution would not be expected 

to change. Table 2 shows the final incident totals for the analysis dataset.

Table 2. Summary of NFIRS WUI-geocoded incidents by year, California 2009-2011, all primary fire incidents

Year Candidate fire 

incidents PDR

Fire incidents successfully

placed in WUI polygon

Fire incidents in land-based 

polygons

Incidents Percent Incidents Percent

2009 59,455 58,378 98.2 58,311 98.1

2010 62,469 60,063 96.1 59,979 96.0

2011 63,321 60,853 96.1 60,786 96.0

Total 185,245 179,294 96.8 179,076 96.7

National Fire Incident Reporting System data

NFIRS data distinguishes between “primary” and “aid” fire incidents. Primary incidents are those incidents where the 

reporting department has the primary or “first due” responsibility for the incident. “Aid” incidents, more properly called 

“aid given” incidents, are those where another department assists the primary department with additional manpower 

or equipment. This analysis only considers primary incidents to prevent the possible double counting of events.

8NFIRS classifies incidents according to type: fire, emergency medical service, hazardous materials and the like. Fires are defined as Incident 

Types 100-173. Prescribed and unauthorized burns (not in the Incident Type 100 Series) are not included. 

9SAS is a statistical software suite used in the analysis of data that can mine, alter, manage and retrieve data from a variety of sources and 

perform statistical analysis on it. Originally developed at North Carolina State University, it is now managed by the SAS Institute.

10R is a programming language and software environment for statistical computing and graphics. The R language is widely used among 

statisticians and others for data exploration and analysis.

11In computational geometry, the point-in-polygon calculation determines whether a given point in the plane lies inside, outside or on the 

boundary of a polygon. It is an important calculation in applications that deal with processing geometrical data, such as in this analysis.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 9

NFIRS data also distinguishes between larger fires in buildings and other structures and smaller building fires that 

are limited in extent, staying within pots, fireplaces or certain other noncombustible containers (“confined fires”). 

For structure fires, this analysis focuses primarily on the larger fires in buildings and other structures as these fires 

are where most property loss occurs.

Across all primary incidents grouped by major incident type groups, the most common incident type groups for 

the overall dataset are structure, rubbish, vehicle and vegetation fires. As well, structure fires are somewhat evenly 

divided between buildings and other structures and the smaller confined fires. For incidents in WUI areas, the most 

common incident type groups are similar although the order changes: structure, vegetation, rubbish and vehicle fires 

(Table 3). These 4 incident type groups account for an average of 90% of the fires in the dataset. 

Table 3. NFIRS incidents by incident type group and area type, California 2009-2011, primary incidents, 

Incident Types 100-173 

Incident type group

Urban WUI Rural Total

Incidents Percent Incidents Percent Incidents Percent Incidents Percent

11x - Structure 35,479 39.3 12,749 30.1 9,266 19.9 57,494 32.1

111, 112 Buildings 

and Other 

Structures 15,604 17.3 7,239 17.1 4,265 9.2 27,108 15.1

113-118 Confined 

Buildings 19,875 22.0 5,510 13.0 5,001 10.7 30,386 17.0

12x - Mobile 

Structure 495 0.5 513 1.2 413 0.9 1,421 0.8

13x - Vehicle 17,086 19.0 7,200 17.0 11,955 25.7 36,241 20.2

14x - Vegetation 9,532 10.6 9,948 23.5 11,503 24.7 30,983 17.3

15x - Rubbish 20,220 22.4 7,491 17.7 9,399 20.2 37,110 20.7

16x - Special 

Outside12 2,986 3.3 1,700 4.0 1,648 3.5 6,334 3.5

17x - Crop 401 0.4 215 0.5 528 1.1 1,144 0.6

100 - Other Fire 3,964 4.4 2,564 6.1 1,821 3.9 8,349 4.7

Total 90,163 100.0 42,380 100.0 46,533 100.0 179,076 100.0

Organization of the report

Structure fires, especially buildings and other structure fires, mobile structures, and vehicles are a primary source 

of loss (USFA, 2019a) and are of particular interest in the mitigation of fire incidents in the WUI. These groups are 

each analyzed in terms of their loss characteristics: number of incidents, incident travel time and losses (casualties 

and property loss). Overall, dollar loss is underreported in NFIRS and is not reported for over 70% of all primary fires 

reported to NFIRS (USFA, 2019b). During the 2009 to 2011 period, information on dollar loss was not reported in 

57% of California primary fires. To supplement this underreporting, losses for incidents are imputed using historical 

data informed by incident type and location data (USFA, 2019b).13 This imputed data was included in the analyses to 

analyze loss data more fully for incidents. 

Other aspects of interest within the WUI areas are the cause of the fire and exposure fires. Cause is available in NFIRS 

only for structure fires and is examined separately for buildings and other structures and for confined building fires. 

The distributions of exposure fires — fires that are the result of another fire — are analyzed as well as their source fire. 

Specific incident types for each incident type group are noted in the Appendix.

12The special outside fires category is outside fires with definable value such as outside trash compactors, outside heating, ventilating and air 

conditioning units, and irrigation pumps. It excludes crops and orchards which are under crop fires.

13Missing data imputation is a statistical method that replaces missing data points with valid, substituted values.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 10

Results

Building and other structure fires

There are a sizable number of building and other structure fire incidents in NFIRS California data as seen in Table 4. 

Almost 27% of the building and other structure fire incidents in the data for 2009 to 2011 occurred in WUI areas. Note 

that these figures do not include the confined fire Incident Types 113-118.

Table 4. NFIRS incidents by area type, California 2009-2011, building and other structure fires, primary 

incidents, Incident Types 111-112 

Area type Building Fire (111) Other Structure Fire (112) Total

Incidents Percent Incidents Percent Incidents Percent

Urban 14,712 58.0 892 51.7 15,604 57.6

WUI 6,750 26.6 489 28.3 7,239 26.7

Rural 3,919 15.4 346 20.0 4,265 15.7

Total 25,381 100.0 1,727 100.0 27,108 100.0

Travel time

Travel time was calculated for each incident by subtracting “arrival time” from “alarm time.” Any travel times over 

1,440 minutes (1 day) were disregarded as erroneous. The travel time to fire incidents in WUI areas was 20% (median) 

to 53% (mean) longer than in urban areas (Table 5). WUI areas’ travel time was on par with that of rural areas. The 

variation in these travel times can be visualized in the boxplot in Figure 4. In the boxplot, the mean is represented 

by the red horizontal line and the median value is represented by the blue dashed horizontal line, with the 25th and 

75th percentiles represented by the bounds of the light blue boxes. 

Table 5. Median and mean travel time for NFIRS incidents by area type, California 2009-2011, building and 

other structure fires, primary incidents, Incident Types 111-112 

Area type Median travel time 

(minutes)

Mean travel time 

(minutes) Standard deviation

Urban 5 5.3 18.1

WUI 6 8.1 33.8

Rural 6 7.9 19.6

Note: Any travel times in excess of 24 hours (1,440 minutes) were removed from analysis.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 11

Figure 4. Distribution of travel time for NFIRS incidents by area type, California 2009-2011, building and 

other structure fires, primary incidents, Incident Types 111-112 

Travel time x WUI analysis group

WUI Rural

WUI analysis group

Travel time (minutes)

Urban

0

20

40

60

80

100

120

Mean

Median

Note: Any travel times in excess of 24 hours (1,440 minutes) were removed from analysis. For ease of presentation, travel times greater than 2 hours (120 minutes) 

are not shown in this graphic.

Loss measures

Dollar loss. Accounting for missing loss data, the total imputed losses for building and other structure fires in WUI 

areas total $463.9 million or an average of $154.6 million per year, as seen in Table 6.

Fire incidents in WUI areas tend to have more underreported loss data in NFIRS. The total imputed costs for fires in 

WUI areas is 9.7% higher compared to the reported losses, whereas the average imputed loss across all regions was 

6.1% (Table 6).

Table 6. Reported and imputed loss for NFIRS incidents by area type, California 2009-2011, building and 

other structure fires, primary incidents, Incident Types 111-112 

Area type Total reported loss

($M)

Total imputed loss

($M) % change

Urban 851.7 890.3 4.5

WUI 423.0 463.9 9.7

Rural 358.2 378.3 5.6

Total 1,632.8 1732.6 6.1
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 12

The median imputed loss for building and other structure fires in WUI areas is 33% higher than urban areas and 14% 

higher than rural areas (Table 7). 

Table 7. Median imputed loss of NFIRS incidents by area type, California 2009-2011, building and other 

structure fires, primary incidents, Incident Types 111-112 

Area type Median reported loss

($M)

Median imputed loss

($M)

Urban 5,000 6,000

WUI 5,000 8,000

Rural 5,000 7,000

There appears to be a relationship between longer travel times and increased dollar loss. Travel times to building 

and other structure fire incidents are longer in WUI and rural areas (Table 5) and the respective per fire dollar losses 

are greater (Table 8).

Table 8. Reported and imputed loss per incident for NFIRS incidents by area type, California 2009-2011, 

building and other structure fires, primary incidents, Incident Types 111-112 

Area type Average reported loss per fire Average imputed loss per fire

Urban $54,582 $57,059

WUI $58,427 $64,087

Rural $83,975 $88,699

Overall $60,233 $63,914

Casualties. The more densely populated urban areas have over 2 1/2 times the casualties (injuries and deaths) in 

building and other structure fire incidents as WUI areas and over 5 times the casualties as rural areas (Table 9). 

Table 9. Reported deaths and injuries for NFIRS incidents by area type, California 2009-2011, building and 

other structure fires, primary incidents, Incident Types 111-112 

Area type Firefighter 

deaths

Firefighter 

injuries

Civilian 

deaths

Civilian 

injuries Total casualties

Urban 0 249 119 653 1,021

WUI 0 132 66 196 394

Rural 0 55 18 119 192

When the number of incidents for each area type are considered, however, building and other structure fire incidents 

in WUI areas have higher rates of firefighter injuries and civilian deaths than urban or rural areas. Civilian fire injury 

rates in WUI areas, however, are the lowest of the 3 areas (Table 10). This may be a further impact of travel times 

where civilians are more likely to die from an incident that requires longer travel times than suffer an injury.

Table 10. NFIRS death and injury rates by area type, California 2009-2011, building and other structure 

fires, primary incidents, Incident Types 111-112 

Area type Firefighter 

deaths/100 fires

Firefighter 

injuries/100 

fires

Civilian 

deaths/100 fires

Civilian 

injuries/100 

fires

Total 

casualties/100 

fires

Urban 0 1.6 0.8 4.2 6.5

WUI 0 1.8 0.9 2.7 5.4

Rural 0 1.3 0.4 2.8 4.5
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 13

Mobile structure fires 

Mobile structures are defined in NFIRS as mobile property used as a fixed structure. The group includes mobile 

homes, motor homes, camping trailers and portable buildings. Mobile structure fire incidents are much less common 

than building and other structure fire incidents. There were 513 mobile structure fire incidents in WUI areas in 

California over the study period (Table 11). These incidents represent 36% of all mobile structure fire incidents.

Table 11. NFIRS incidents by area type, California 2009-2011, mobile structure fires, primary incidents, 

Incident Types 120-123 

Area 

type

Mobile, Other 

(120)

Mobile Home

(121)

Motor Home

(122)

Portable Bldg. 

(123) Total

Incidents Percent Incidents Percent Incidents Percent Incidents Percent Incidents Percent

Urban 43 30.9 194 29.6 182 40.0 76 44.2 495 34.8

WUI 44 31.7 275 42.0 149 32.7 45 26.2 513 36.1

Rural 52 37.4 186 28.4 124 27.3 51 29.7 413 29.1

Total 139 100.0 655 100.0 455 100.0 172 100.0 1,421 100.0

Travel time

Travel time to mobile structure fire incidents in WUI areas in California was 40% (median) to 53% (mean) longer than in 

urban areas and 13% to 6% shorter than in rural areas (Table 12). The variation in these travel times can be visualized 

in the boxplot in Figure 5.

Table 12. Median and mean travel time for NFIRS incidents by area type, California 2009-2011, mobile 

structure fires, primary incidents, Incident Types 120-123 

Area type Median travel time 

(minutes)

Mean travel time

(minutes) Standard deviation

Urban 5 6.0 3.9

WUI 7 9.2 8.8

Rural 8 9.8 7.1

Note: Any travel times in excess of 24 hours (1,440 minutes) were removed from analysis.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 14

Figure 5. Distribution of travel time for NFIRS incidents by WUI group, California 2009-2011, mobile 

structure fires, primary incidents, Incident Types 120-123 

Travel time x WUI analysis group

WUI Rural

WUI analysis group

Travel time (minutes)

Urban

0

20

40

60

80

100

120

Mean

Median

Note: Any travel times in excess of 24 hours (1,440 minutes) were removed from analysis. For ease of presentation, travel times greater than 2 hours (120 minutes) 

are not shown in this graphic.

Loss measures

Dollar loss. Total imputed losses for mobile structure fires in WUI areas, the highest of the 3 areas, totaled $8.9 

million over the 3 years, averaging $3 million per year (Table 13).

Table 13. Reported and imputed loss for NFIRS incidents by area type, California 2009-2011, mobile 

structure fires, primary incidents, Incident Types 120-123 

Area type Total reported loss

($M)

Total imputed loss

($M) % change

Urban 7.2 7.9 9.7

WUI 8.4 8.9 6.0

Rural 7.5 8.2 9.3

Total 23.2 25.0 7.8

Note: Totals may not add up to 100% due to rounding.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 15

The median loss for mobile structure fires in WUI areas is 25% (imputed) to 40% (reported) higher than urban areas 

and on par with rural areas for imputed loss (Table 14). Similar to building and other structure fires, there appears 

to be a linkage between longer travel times to mobile structure fire incidents’ dollar loss (Table 15).

Table 14. Median imputed loss of NFIRS incidents by area type, California 2009-2011, mobile structure 

fires, primary incidents, Incident Types 120-123 

Area type Median reported loss

($M)

Median imputed loss

($M)

Urban $2,500 $4,000

WUI $3,500 $5,000

Rural $2,500 $5,500

Table 15. Reported and imputed loss per incident for NFIRS incidents by area type, California 2009-2011, 

mobile structure fires, primary incidents, Incident Types 120-123 

Area type Average reported loss per fire Average imputed loss per fire

Urban $14,641 $15,909 

WUI $16,461 $17,388 

Rural $18,154 $19,858 

Overall $16,319 $17,591 

Casualties. Mobile structure fire incidents in WUI areas have slightly more casualties than those in urban and rural 

areas (Table 16). The numbers of reported casualties are small, and comparisons may not be fully valid.

Table 16. Reported deaths and injuries for NFIRS incidents by area type, California 2009-2011, mobile 

structure fires, primary incidents, Incident Types 120-123 

Area type Firefighter 

deaths

Firefighter 

injuries

Civilian 

deaths

Civilian 

injuries

Total 

casualties

Urban 0 4 7 12 23

WUI 0 1 5 19 25

Rural 0 1 3 14 18

When the number of fire incidents for each area type is considered, however, mobile structure fire incidents in WUI 

areas have higher casualty rates, collectively, than urban or rural areas. The firefighter injury rate for mobile structure 

fires is highest in urban areas as is the civilian fire death rate (Table 17). As the sample is small for these casualties, 

comparisons need to be made with caution.

Table 17. Death and injury rates by area type, California 2009-2011, mobile structure fires, primary 

incidents, Incident Types 120-123 

Area type

Firefighter 

deaths/

100 fires

Firefighter 

injuries/

100 fires

Civilian deaths/

100 fires

Civilian injuries/

100 fires

Total casualties/

100 fires

Urban 0.0 0.8 1.4 2.4 4.7

WUI 0.0 0.2 1.0 3.7 4.9

Rural 0.0 0.2 0.7 3.4 4.4
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 16

Vehicle fires

There are a sizable number of vehicle fire incidents over the study period (Table 18). There were 7,200 vehicle fire 

incidents in WUI areas, representing 20% of all vehicle fires (Table 19).

Table 18. NFIRS incidents by area type, California 2009-2011, vehicle fires, primary incidents, 

Incident Types 130-138 

Area 

type

Mobile 

Prop 

Vehicle, 

Other 

(130)

Passenger 

Vehicle 

(131)

Transport 

Vehicle 

(132)

Rail 

Vehicle 

(133)

Water 

Vehicle 

(134)

Aircraft 

(135)

SelfPropelled 

RV

(136)

Camper 

(137)

Off-Road/ 

Heavy 

Equip 

(138)

Total

Urban 1,367 14,820 511 17 77 7 39 154 94 17,086

WUI 693 5,716 357 10 62 4 59 202 97 7,200

Rural 1,002 9,436 882 35 82 33 49 193 243 11,955

Total 3,062 29,972 1,750 62 221 44 147 549 434 36,241

Table 19. Distribution of NFIRS incidents by area type, California 2009-2011, vehicle fires, primary incidents, 

Incident Types 130-138 

Area 

type

Mobile 

Prop 

Vehicle, 

Other 

(130)

Passenger 

Vehicle 

(131)

Transport 

Vehicle 

(132)

Rail 

Vehicle 

(133)

Water 

Vehicle 

(134)

Aircraft 

(135)

SelfPropelled 

RV

(136)

Camper 

(137)

Off-Road/ 

Heavy 

Equip 

(138)

Total

Urban 44.6% 49.4% 29.2% 27.4% 34.8% 15.9% 26.5% 28.1% 21.7% 47.1%

WUI 22.6% 19.1% 20.4% 16.1% 28.1% 9.1% 40.1% 36.8% 22.4% 19.9%

Rural 32.7% 31.5% 50.4% 56.5% 37.1% 75.0% 33.3% 35.2% 56.0% 33.0%

Total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0%

Travel time

The median travel time to vehicle fire incidents in rural and WUI areas was similar to urban areas. However, the mean 

travel time to these areas was 24% longer for WUI areas and 30% longer for rural areas than for urban areas (Table 

20). The variation in these travel times can be visualized in the boxplot in Figure 6. The difference between median 

and mean in the urban, rural and WUI areas is due to the presence of more outliers or extreme observations in the 

rural and WUI areas. 

Table 20. Median and mean travel time for NFIRS incidents by area type, California 2009-2011, vehicle 

fires, primary incidents, Incident Types 130-138 

Area type Median travel time 

(minutes)

Mean travel time

(minutes) Standard deviation

Urban 5 6.0 16.2

WUI 6 7.5 15.7

Rural 6 7.9 11.5

Note: Any travel times in excess of 24 hours (1,440 minutes) were removed from analysis.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 17

Figure 6. Distribution of travel time for NFIRS incidents by WUI group, California 2009-2011, vehicle fires, 

primary incidents, Incident Types 130-138 

Travel time x WUI analysis group

WUI Rural

WUI analysis group

Travel time (minutes)

Urban

0

20

40

60

80

100

120

Mean

Median

Note: Any travel times in excess of 24 hours (1,440 minutes) were removed from analysis. For ease of presentation, travel times greater than 2 hours (120 minutes) 

are not shown in this graphic.

Loss measures

Dollar loss. Total imputed losses for vehicle fire incidents in WUI areas totaled $58.1 million over the 3 years, 

averaging $19.4 million per year (Table 21). Unlike losses for fixed or mobile structure fires, the median losses for 

vehicle fires in WUI areas are similar to both urban and rural areas (Table 22). As noted earlier, there appears to be 

a relationship between longer travel times and increased dollar loss. The loss per fire is greater in WUI areas than 

in urban areas. Rural incidents, however, have substantially higher per-incident losses (Table 23) as the result of the 

predominance of a small number of aircraft incidents (Table 24).

Table 21. Reported and imputed loss for NFIRS incidents by area type, California 2009-2011, vehicle fires, 

primary incidents, Incident Types 130-138 

Area type Total reported loss

($M)

Total imputed loss

($M) % change

Urban 111.7 119.8 7.2

WUI 52.4 58.1 10.9

Rural 187.2 195.8 4.6

Total 351.3 373.7 6.4
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 18

Table 22. Median imputed loss of NFIRS incidents by area type, California 2009-2011, vehicle fires, primary 

incidents, Incident Types 130-138 

Area type Median reported loss

($M)

Median imputed loss

($M)

Urban 2,600 3,000

WUI 2,000 3,000

Rural 3,000 3,000

Table 23. Reported and imputed loss per incident for NFIRS incidents by area type, California 2009-2011, 

vehicle fires, primary incidents, Incident Types 130-138 

Area type Average reported loss per 

incident ($M)

Average imputed loss per incident 

($M)

Urban 6,537 7,011

WUI 7,283 8,075

Rural 15,658 16,376

Overall 9,694 10,312

Table 24. Reported and imputed loss for aircraft and non-aircraft NFIRS incidents by area type, California 

2009-2011, vehicle fires, primary incidents, Incident Types 130-138 

Area 

type

Incidents

Average reported 

loss

per incident 

($M)

Average 

imputed loss 

per incident 

($M)

Median 

reported loss ($M)

Median 

imputed loss ($M)

Aircraft Nonaircraft Aircraft Nonaircraft Aircraft Nonaircraft Aircraft Nonaircraft Aircraft Nonaircraft

Urban 7 17,079 530,857 6,322 534,429 6,795 19,500 2,600 20,000 3,000

WUI 4 7,196 21,250 7,276 36,250 8,059 7,500 2,000 30,000 3,000

Rural 33 11,922 2,150,409 9,749 2,151,758 10,465 10,000 3,000 8,500 3,000

Overall 44 36,197 1,699,193 7,640 1,702,136 8,255 10,000 2,500 12,500 3,000

Casualties. Vehicle fire incidents in WUI areas have similar death or injury rates per 100 fires compared to those in 

urban and rural areas (Table 25).

Table 25. Reported deaths and injuries for NFIRS incidents by area type, California 2009-2011, vehicle fires, 

primary incidents, Incident Types 130-138 

Area type Firefighter 

deaths

Firefighter 

injuries Civilian deaths Civilian injuries Total injuries or deaths

Urban 0 17 33 71 121

WUI 0 6 12 25 43

Rural 0 11 28 27 66

When the number of incidents for each area type are considered, however, civilian injuries due to vehicle fires occur 

in WUI areas less frequently than in urban areas but more frequently than in rural areas (Table 26). Note, these 

numbers are small and inferences about rates should be considered with caution.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 19

Table 26. Death and injury rates by area type, California 2009-2011, vehicle fires, primary incidents, 

Incident Types 130-138 

Area type

Firefighter 

deaths/

100 fires

Firefighter 

injuries/

100 fires

Civilian deaths/

100 fires

Civilian injuries/

100 fires

Total casualties/

100 fires

Urban 0 0.1 0.2 0.4 0.7

WUI 0 0.1 0.2 0.3 0.6

Rural 0 0.1 0.2 0.2 0.6

Fire cause

Within NFIRS, the cause of fire is determined by using a hierarchical set of rules based on the reported fire-related 

data. Currently, this cause is only calculated for structure fires (Incident Types 111-123: buildings, other structures, 

building fires contained to noncombustible containers, and mobile structures). This data can be combined with the 

geographic classification methodology as described above to analyze fire incident cause within the WUI. NFIRS has 

a special classification for fires in buildings that are confined to noncombustible containers (Incident Types 113-118). 

The causes of these fires are examined separately below.

The primary causes for nonconfined structure fires within the WUI, other than unknown, are electrical malfunction; 

other unintentional, careless actions; and open flame (Table 27). Percentages for some causes stand out in the WUI. 

For nonconfined structures, fires in WUI areas are less likely to have a cause of intentional or exposure than incidents 

in rural or urban areas. Fires in WUI areas are more likely to be caused by heating, cooking, appliances, open flame 

and cause under investigation than those in rural or urban areas.

Table 27. NFIRS reported incidents by cause by area type, California 2009-2011, nonconfined structure 

fires, primary incidents, Incident Types 111-112 and 120-123 

Cause

Urban WUI Rural Total

Incidents Percent Incidents Percent Incidents Percent Incidents Percent

01-Intentional 1,327 8.2 453 5.8 406 8.7 2,186 7.7

02-Playing with Heat Source 124 0.8 54 0.7 21 0.4 199 0.7

03-Smoking 679 4.2 200 2.6 106 2.3 985 3.5

04-Heating 455 2.8 316 4.1 129 2.8 900 3.2

05-Cooking 451 2.8 261 3.4 78 1.7 790 2.8

06-Electrical Malfunction 2,179 13.5 1,075 13.9 693 14.8 3,947 13.8

07-Appliances 661 4.1 390 5.0 200 4.3 1,251 4.4

08-Open Flame 1,269 7.9 675 8.7 276 5.9 2,220 7.8

09-Other Heat 1,187 7.4 511 6.6 300 6.4 1,998 7.0

10-Other Equipment 360 2.2 196 2.5 147 3.1 703 2.5

11-Natural 281 1.7 175 2.3 108 2.3 564 2.0

12-Exposure 665 4.1 295 3.8 266 5.7 1,226 4.3

13-Unknown 3,286 20.4 1,674 21.6 1,099 23.5 6,059 21.2

14-Equipment Malfunction, Failure 1,208 7.5 575 7.4 339 7.2 2,122 7.4

15-Other Unintentional, Careless 1,800 11.2 797 10.3 463 9.9 3,060 10.7

16-Cause Under Investigation 167 1.0 105 1.4 47 1.0 319 1.1

Total 16,099 100.0 7,752 100.0 4,678 100.0 28,529 100.0

 Less likely14 More likely

14The relative likelihood of structure fire causes in the WUI area was determined by comparing the percentage of a given cause across the 3 

area types. The cause of fires in the WUI was deemed less likely if it had the lowest percentage of fires across the 3 area types; conversely, it 

was deemed more likely if it had the highest percentage of fires across the 3 area types.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 20

This data can be segregated to only examine building and other structure fires. The primary causes for building and 

other structure fires within the WUI, other than unknown, are electrical malfunction; other unintentional, careless 

actions; and open flame (Table 28).

For structure and other building fires, the WUI is less likely to have intentional, other heat, other equipment, and 

exposure fire causes than incidents in rural or urban areas. For structure and other building fires, the WUI is more 

likely to have heating, cooking, appliances, open flame, equipment malfunction/failure, and cause under investigation 

fires than rural or urban areas.

Table 28. NFIRS reported incidents by cause by area type, California 2009-2011, buildings and other 

structures, primary incidents, Incident Types 111-112 

Cause

Urban WUI Rural Total

Incidents Percent Incidents Percent Incidents Percent Incidents Percent

01-Intentional 1,269 8.1 426 5.9 375 8.8 2,070 7.6

02-Playing with Heat Source 123 0.8 52 0.7 21 0.5 196 0.7

03-Smoking 672 4.3 186 2.6 98 2.3 956 3.5

04-Heating 449 2.9 287 4.0 106 2.5 842 3.1

05-Cooking 444 2.8 249 3.4 70 1.6 763 2.8

06-Electrical Malfunction 2,125 13.6 1,005 13.9 653 15.3 3,783 14.0

07-Appliances 644 4.1 374 5.2 183 4.3 1,201 4.4

08-Open Flame 1,241 8.0 643 8.9 250 5.9 2,134 7.9

09-Other Heat 1,169 7.5 478 6.6 288 6.8 1,935 7.1

10-Other Equipment 282 1.8 126 1.7 105 2.5 513 1.9

11-Natural 276 1.8 169 2.3 104 2.4 549 2.0

12-Exposure 631 4.0 272 3.8 230 5.4 1,133 4.2

13-Unknown 3,187 20.4 1,571 21.7 991 23.2 5,749 21.2

14-Equipment Malfunction, Failure 1,168 7.5 549 7.6 314 7.4 2,031 7.5

15-Other Unintentional, Careless 1,765 11.3 758 10.5 433 10.2 2,956 10.9

16-Cause Under Investigation 159 1.0 94 1.3 44 1.0 297 1.1

Total 15,604 100.0 7,239 100.0 4,265 100.0 27,108 100.0

 Less likely More likely

For confined fires, when only the known causes are considered, the 4 leading causes (intentional, smoking, heating 

and cooking) account for 92% of confined fires. In WUI areas, heating is more likely to be the cause of a confined fire 

than in urban or rural areas — the percentage for confined heating fires is 5 times that of urban areas and over 3 

times that of rural areas. Conversely, intentional and smoking are less likely to be the cause of a confined fire in WUI 

areas than in urban or rural areas (Table 29).
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 21

Table 29. Reported NFIRS incidents by cause by area type, California 2009-2011, confined building fires, 

primary incidents, Incident Types 113-118 

Cause

Urban WUI Rural Total

Incidents Percent Incidents Percent Incidents Percent Incidents Percent

01-Intentional 1,110 5.6 243 4.4 328 6.6 1,681 5.5

03-Smoking 630 3.2 72 1.3 256 5.1 958 3.2

04-Heating 871 4.4 1,193 21.7 295 5.9 2,359 7.8

05-Cooking 12,275 61.8 2,801 50.8 1,973 39.5 17,049 56.1

13-Unknown 3,691 18.6 930 16.9 1,680 33.6 6,301 20.7

All Other Causes 1,298 6.5 271 4.9 469 9.4 2,038 6.7

Total 19,875 100.0 5,510 100.0 5,001 100.0 30,386 100.0

 Less likely More likely

Exposure fires

An exposure is a fire that results from another fire incident.15 This exposure data can be combined with the geographic 

classification methodology as described above to analyze the characteristics of exposure fires within the WUI. 

Exposure fires are not common: in the analysis dataset, only 1% of fires were the originating fire and another 2% 

were the resulting exposure fire.

Of primary interest in analyzing exposure fires is the originating incident type to discover the root cause of the fire 

that spread to multiple incidents. To analyze this data, any incident that is marked as an exposure is joined by the 

state, fire department, fire department identification number, incident date and incident number with its “parent” 

or originating nonexposure incident. Instances where no parent could be identified are separated out in the analysis 

in the category of “Missing Originating Fire.”16

The distribution of the incident type of the originating fires is shown in Table 30. Across the area types, structure and 

vehicle fires are by far the most common source of exposure fires and, on average, account for 64% of the originating 

fires. These fires are slightly less likely to be the source of exposures in the WUI where they account for 61% of WUI 

area fires. Within the WUI, mobile structure fires and vegetation fires are more likely to be the originating incident 

type compared with rural or urban areas. Vegetation fires in the WUI are twice as likely to have been the exposure 

source than for urban areas.

15Exposure fires in NFIRS are fully defined as “A fire in a building, structure, vehicle, or outside property resulting from a fire outside that building, 

structure, vehicle, or outside property.” 

16Missing originating fires fall into 2 categories: those with insufficient address information to have been geocoded and included in the dataset 

and those that were not included in the public data.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 22

Table 30. NFIRS originating incident type for incidents with exposures by area type, California 2009-2011, 

primary incidents, Incident Types 100-173 

Originating incident type

Urban WUI Rural Total

Incidents Percent Incidents Percent Incidents Percent Incidents Percent

11x - Structure Fire 368 36.7 131 31.8 93 25.9 592 34.3

12x - Mobile Structure 13 1.3 21 5.1 11 3.1 45 2.9

13x - Vehicle 289 28.8 119 28.9 138 38.4 546 28.2

14x - Vegetation 81 8.1 71 17.2 57 15.9 209 12.3

15x - Rubbish 174 17.4 42 10.2 34 9.5 250 10.6

16x - Special Outside 41 4.1 20 4.9 18 5.0 79 4.9

17x - Crop 5 0.5 2 0.5 3 0.8 10 1.1

100 - Other Fire 31 3.1 6 1.5 5 1.4 42 2.1

Missing Originating Fire 68 3.6

Total 1,002 100.0 412 100.0 359 100.0 1,841 100.0

 More likely

The 1,841 originating fires generated 3,019 exposure fires. By identifying the origin exposure fire and the analysis 

group where it originated, the data can be further grouped by originating area (Table 31). Generally, the originating 

fire generates exposure fires in the same area: 92% of urban exposure fires originate in urban areas and 90% of WUI 

exposure fires originate in the WUI. Rural, though, appears to have a slightly different distribution: only 81% of rural 

exposure fires originate as a rural incident. Additional detail about the incident type of the exposure fire is included 

in the Appendix. 

Table 31. NFIRS originating and exposure incident area for incidents with exposures by area type, 

California 2009-2011, primary incidents, Incident Types 100-173 

Originating 

incident area

Exposure incident area

Urban WUI Rural Total

Incidents Percent Incidents Percent Incidents Percent Incidents Percent

Urban 1,475 91.8 17 2.5 57 7.8 1,549 51.3

WUI 28 1.7 613 90.1 50 6.8 691 22.9

Rural 49 3.0 24 3.5 596 81.4 669 22.2

Missing Originating 

Fire* 55 3.4 26 3.8 29 4.0 110 3.6

Total* 1,607 100.0 680 100.0 732 100.0 3,019 100.0

*The 68 missing originating fires from Table 30 generated 110 exposure fires.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 23

Conclusion

Using the method described, it is possible to identify NFIRS incidents in the WUI by combining their geographical 

coordinates with USFS shapefiles that identify their WUI classification. The use of this technique can be used broadly 

to analyze NFIRS data and draw a number of observations about NFIRS data and the WUI. Some of the conclusions 

drawn about fires in WUI areas may shape recommendations for how to mitigate the risk from fire in the WUI.

Important observations that result from this study are:

ĵ Median travel times to fire incidents in the WUI for structures and other buildings are 20% longer than those for 

urban fire incidents, appear to result in 33% higher median losses, and have higher rates of firefighter injuries 

and civilian deaths.

ĵ Median travel times to fire incidents in the WUI for mobile structures are 40% longer than those for urban incidents, 

appear to result in 25% higher median losses, and may have slightly higher casualty rates.

ĵ Median travel times to fire incidents in the WUI for vehicles are similar to those for urban fire incidents, appear 

to result in similar median losses, and may have slightly lower rates of deaths or injuries.

ĵ Overall, nonconfined structure fire incidents in WUI areas are caused by electrical malfunction; other unintentional, 

careless actions; and open flame. Nonconfined structure fires in WUI areas are less likely to have a cause of 

intentional or exposure than incidents in rural or urban areas. Nonconfined structure fires in WUI areas are 

more likely to be caused by heating, cooking, appliances, open flame and cause under investigation than those 

in rural or urban areas.

ĵ Small, confined fires in WUI areas are more likely to be caused by heating than in urban or rural areas. Confined 

heating fires are 5 times more likely in WUI areas than urban areas and over 3 times more likely than rural areas.

ĵ Fires in WUI areas that are exposures from other fire incidents are more likely to have resulted from vegetation 

or mobile structure fires than in urban or rural areas. Structure and vehicle fires still account for 61% of the 

originating fires in the WUI. 

ĵ Overall, originating fires generate exposure fires in the same area: 92% of urban exposure fires originate in urban 

areas, 90% of WUI exposure fires originate in the WUI and 81% of rural exposure fires originate as a rural incident. 

There appears to be little overlap in fire generation between areas.

Limitations

NFIRS does not record geographic coordinates (latitude and longitude) of an incident within the Basic Module, 

and incidents must be geocoded based on the address or location information provided by the fire department. 

Depending on the completeness and accuracy of the address/location information and limitations on the encoding 

algorithm, the geocoding algorithm may not be able to determine latitude and longitude for an incident with a high 

degree of precision. Some incident locations may only be identified at a broad level of accuracy and therefore be 

assigned coordinates that correspond to the center of a city or ZIP code if the information needed for a more precise 

determination is missing or inaccurate. Some incidents cannot be geocoded with any level of precision and are 

discarded from the dataset. This could affect conclusions about medians and means of the remaining population.

The study was focused on incidents exclusively in California as reported to NFIRS. Observations about populations, 

travel time and property loss may not be applicable to other states. 

The most recent USFS WUI shapefiles are from 2010. Observations about populations, travel time and property loss 

may have changed since that date. 
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 24

Future work

The inability to successfully geocode many NFIRS incidents is a constraint on many geographic-based analyses. More 

accurate geocoding of incidents could add a substantial number of additional incidents to the study. An outreach 

program to encourage NFIRS departments to correctly record address information and standardize input of other 

types of location information, or NFIRS modifications to allow fire departments to submit geographic coordinates 

would be beneficial. Enabling NFIRS to accept polygon-based geographic data in addition to the current point data 

would enable better analysis of geographically large incidents.

Expanding the study to additional states beyond California is suggested to see if observations about populations, 

travel time, and property loss are applicable to other states. California has unique geographic and climate 

considerations that may result in WUI fire patterns distinctive to California.

It may be possible to create custom WUI shapefiles using more recent data than that which is available from the 

USFS. These custom shapefiles would allow for observations about populations, travel time and property loss that 

are more current. 

Further analysis into the relationships between travel times and losses, in particular for building and structure fires, 

is warranted to see what factors may influence structure fire losses. For dollar loss, including real estate cost factors, 

if available, might be beneficial. Expanding the analyses to include Fire Module data for structures might also provide 

insight into losses in the WUI.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 25

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Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 27

Appendix

National Fire Incident Reporting System wildland fire definitions 

The NFIRS Wildland Fire Module has its own set of definitions for recording incidents (USFA, 2019). The term “wildland” 

as used by NFIRS is a bit of a misnomer relative to the definitions in this paper as, in practice, NFIRS Wildland Fire Module 

is used to record wildfires, not fires in the wildland.

ĵ Prescribed Fire. Any fire ignited by management actions to meet specific objectives. A written, approved prescribed 

fire plan must exist prior to ignition (Incident Type 632). A prescribed fire that escapes management is a hostile 

fire (Incident Type 141). 

ĵ Urban-Wildland Interface Area. The geographical area in which structures and other human development meet 

or intermingle with wildland or vegetative fuels. 

ĵ Urban-Wildland Interface Fire. Any fire, other than prescribed fire, where fire suppression tactics were influenced 

by a geographical area where structures and other human development meet or intermingle with wildland or 

vegetative fuels. 

ĵ Wildland. An area in which development is essentially nonexistent, except for roads, railroads, power lines and 

similar facilities. 

ĵ Wildland Fire. Any fire, other than a prescribed fire, involving vegetative fuels that occurs in the wildland. A 

wildland fire may expose and possibly consume structures (Incident Type 141).

National Fire Incident Reporting System incident groupings

For the purposes of this report, NFIRS incident types are grouped as shown in Table A-1.

Table A-1. NFIRS incident type groupings

Incident type grouping Incident Type Incident type description

Buildings and other 

structures

111 Building fire

112 Fire in structure other than in a building

Confined building

113 Cooking fire, confined to container

114 Chimney or flue fire, confined to chimney or flue

115 Incinerator overload or malfunction, fire confined

116 Fuel burner/boiler malfunction, fire confined

117 Commercial Compactor fire, confined to rubbish

118 Trash or rubbish fire, contained

Mobile structures

120 Fire in mobile property used as a fixed structure, other

121 Fire in mobile home used as fixed residence

122 Fire in motor home, camper, recreational vehicle

123 Fire in portable building, fixed location

Vehicle

130 Mobile property (vehicle) fire, other

131 Passenger vehicle fire

132 Road freight or transport vehicle fire

134 Water vehicle fire

133 Rail vehicle fire

135 Aircraft fire

136 Self-propelled motor home or recreational vehicle

137 Camper or recreational vehicle (RV) fire

138 Off-road vehicle or heavy equipment fire
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 28

Other wildfire definitions 

There are many definitions in the wildland arena. The definitions are often very similar, with each agency/report using a slight variation (Table A-2). The 

definitions often conflate the type of fire with the location of the fire. Some definitions, however, presuppose a common understanding of an undefined term(s). 

Table A-2. Wildland, WUI and wildfire terms

Source Wildland WUI Wildland fire WUI fire Wildfire

1. National 

Fire Incident 

Reporting System 

5.0 Complete 

Reference Guide, 

January 2015

An area in which 

development is 

essentially nonexistent, 

except for roads, 

railroads, power lines, 

and similar facilities.

The geographical area 

where structures 

and other human 

development meet 

or intermingle with 

wildland or vegetative 

fuels.

Any fire involving 

vegetative fuels, other 

than a prescribed 

fire, that occurs in the 

wildland. A wildland 

fire may expose and 

possibly consume 

structures (Incident 

Type 141).

Any fire, other than a 

prescribed fire, where 

fire suppression tactics 

were influenced by 

a geographical area 

where structures 

and other human 

development meet 

or intermingle with 

wildland or vegetative 

fuels.

2. Wildland Urban 

Interface Fire 

Operational 

Requirements and 

Capability Analysis, 

May 2019, p.1

...the area where 

houses and wildland 

vegetation meet 

or overlap, posing 

an increased risk 

for wildfires due 

to human-caused 

ignitions and a greater 

risk posed to lives and 

property where wildfire 

problems are most 

pronounced.

Any non-structure fire, 

other than prescribed 

fire, that occurs in the 

wildland.

...the amalgamation 

where structures and 

human development 

meet with undeveloped 

vegetative fuels and 

are differentiated from 

structure and wildland 

fires.

3. U.S. Forest Service ...where houses and 

other development 

meet or mix with 

undeveloped natural 

areas...
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 29

Table A-2. Wildland, WUI and wildfire terms — continued

Source Wildland WUI Wildland fire WUI fire Wildfire

4. National Fire 

Protection 

Association 1143, 

Standard for 

Wildland Fire 

Management, 2018 

edition

3.3.22 Locations 

in which the AHJ 

[authority having 

jurisdiction] determines 

that topographical 

features, vegetation 

fuel types, local 

weather conditions, 

and prevailing winds 

result in the potential 

for ignition of the 

structures with the 

area from flames and 

firebrands of a wildland 

fire.

3.3.21 An unplanned 

and uncontrolled 

fire spreading 

through vegetative 

fuels, including any 

structures or other 

improvements thereon.

5. National Fire Plan 

(2000)

...an area where 

structures and other 

human development 

meet or intermingle 

with undeveloped 

wildland.

6. National Wildfire 

Coordinating Group

An area in which 

development 

is essentially 

non-existent, except 

for roads, railroads, 

powerlines, and similar 

transportation facilities. 

Structures, if any, are 

widely scattered. 

The line, area, or zone 

where structures 

and other human 

development meet 

or intermingle with 

undeveloped wildland 

or vegetative fuels. 

Describes an area 

within or adjacent to 

private and public 

property where 

mitigation actions can 

prevent damage or loss 

from wildfire.

Any non-structure 

fire that occurs in 

vegetation or natural 

fuels. Includes wildfires 

and prescribed fires. 

An unplanned, 

unwanted wildland fire 

including unauthorized 

human-caused fires, 

escaped wildland fire 

use events, escaped 

prescribed fire 

projects, and all other 

wildland fires where 

the objective is to put 

the fire out (definition 

currently under review).
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 30

Table A-2. Wildland, WUI and wildfire terms — continued

Source Wildland WUI Wildland fire WUI fire Wildfire

7. Federal Register Federal agencies focus 

on two categories:

Interface and Intermix. 

Interface is “where 

structures directly abut 

wildland fuels...The 

development density for 

an interface community 

is usually 3 or more 

structures per acre... An 

alternative definition 

of the interface 

community emphasizes 

a population density of 

250 or more people per 

square mile.” Intermix 

is “where structures are 

scattered throughout 

a wildland area...The 

development density 

in the intermix ranges 

from structures very 

close together to 

one structure per 40 

acres...An alternative 

definition of intermix 

community emphasizes 

a population density of 

between 28-250 people 

per square mile.”

Sources: 1. https://www.usfa.fema.gov/downloads/pdf/nfirs/NFIRS_Complete_Reference_Guide_2015.pdf

2. https://www.dhs.gov/sites/default/files/publications/wui_fire_report_of_findings_july_24_2019v2_508.pdf

3. https://www.nrs.fs.fed.us/data/WUI

4. https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=1143

5. https://www.doi.gov/sites/doi.gov/files/migrated/pmb/owf/upload/2000-Report-to-the-President.pdf

6. https://www.nwcg.gov/about-the-nwcg-glossary-of-wildland-fire

7. https://www.federalregister.gov/documents/2001/01/04/01-52/urban-wildland-interface-communities-within-the-vicinity-of-federal-lands-that-are-at-high-risk-from
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 31

Exposure fires by incident groups and incident types

The most common exposure fire incident type groups in the WUI are structure, vehicle and vegetation fires (Table A-3).

Table A-3. NFIRS exposure fire incidents by incident type group by WUI analysis group, 

California 2009-2011, primary incidents, Incident Types 100-173 

Incident Type Urban WUI Rural Total

11x - Structure Fire 634 249 218 1,101

12x - Mobile Structure 33 21 36 90

13x - Vehicle 573 202 306 1,081

14x - Vegetation 69 99 97 265

15x - Rubbish 121 21 27 169

16x - Special Outside 85 38 26 149

17x - Crop 9 2 9 20

100 - Other Fire 83 48 13 144

Total 1,607 680 732 3,019

Table A-4 presents the detailed breakout of exposure fires as percentages for each area type.

Table A-4. NFIRS exposure fire incidents by incident type group by WUI analysis group, 

California 2009-2011, primary incidents, Incident Types 100-173 

Incident Type Urban WUI Rural Grand total

11x - Structure Fire 39.5% 36.6% 29.8% 36.5%

12x - Mobile Structure 2.1% 3.1% 4.9% 3.0%

13x - Vehicle 35.7% 29.7% 41.8% 35.8%

14x - Vegetation 4.3% 14.6% 13.3% 8.8%

15x - Rubbish 7.5% 3.1% 3.7% 5.6%

16x - Special Outside 5.3% 5.6% 3.6% 4.9%

17x - Crop 0.6% 0.3% 1.2% 0.7%

100 - Other Fire 5.2% 7.1% 1.8% 4.8%

Overall 100.0% 100.0% 100.0% 100.0%

Table A-5 is the detailed breakout of exposure fire incident type groups (Table A-3) by their reported individual incident 

types. Basing further observations or conclusions on this data may be difficult as the exposure fire data is a small 

subset of the reported fire data. This subset combined with the large number of incident types results in very small 

numbers in some of the categories.
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 32

Table A-5. NFIRS fire incidents by incident type by WUI analysis group, California 2009-2011, primary 

incidents, Incident Types 100-173 

Incident 

Type Incident type description Urban WUI Rural Total

111 Building fire 550 224 189 963

112 Fire in structure other than in a building 49 22 17 88

113 Cooking fire, confined to container 5 5

114 Chimney or flue fire, confined to chimney or flue 1 1

117 Commercial Compactor fire, confined to rubbish 1 1 2

118 Trash or rubbish fire, contained 29 3 10 42

120 Fire in mobile property used as a fixed structure, other 3 2 3 8

121 Fire in mobile home used as fixed residence 7 10 19 36

122 Fire in motor home, camper, recreational vehicle 15 8 10 33

123 Fire in portable building, fixed location 8 1 4 13

130 Mobile property (vehicle) fire, other 45 8 27 80

131 Passenger vehicle fire 499 160 204 863

132 Road freight or transport vehicle fire 15 10 34 59

134 Water vehicle fire 3 4 7 14

135 Aircraft fire 1 1

136 Self-propelled motor home or recreational vehicle 2 3 4 9

137 Camper or recreational vehicle (RV) fire 6 14 17 37

138 Off-road vehicle or heavy equipment fire 3 3 12 18

140 Natural vegetation fire, other 20 15 7 42

141 Forest, woods or wildland fire 2 3 4 9

142 Brush or brush-and-grass mixture fire 12 37 36 85

143 Grass fire 35 44 50 129

150 Outside rubbish fire, other 27 2 3 32

151 Outside rubbish, trash or waste fire 64 10 14 88

154 Dumpster or other outside trash receptacle fire 29 9 10 48

155 Outside stationary compactor/compacted trash fire 1 1

160 Special outside fire, other 36 22 10 68

161 Outside storage fire 34 11 11 56

162 Outside equipment fire 15 5 3 23

163 Outside gas or vapor combustion explosion 2 2

170 Cultivated vegetation, crop fire, other 1 1 2 4

171 Cultivated grain or crop fire 1 3 4

172 Cultivated orchard or vineyard fire 1 3 4

173 Cultivated trees or nursery stock fire 6 1 1 8

100 Other fire 83 48 13 144

Grand total 1,607 680 732 3,019
Analysis of NFIRS Incidents in the Wildland Urban Interface — An Analysis of California NFIRS Data, 2009-2011 33

Table A-6 presents the detailed breakout of exposure fires from Table A-5 as percentages for each area type.

Table A-6. NFIRS fire incidents distribution by incident type by WUI analysis group, California 2009-2011, 

primary incidents, Incident Types 100-173 

Incident 

Type Incident type description Urban WUI Rural Total

111 Building fire 34.2% 32.9% 25.8% 31.9%

112 Fire in structure other than in a building 3.0% 3.2% 2.3% 2.9%

113 Cooking fire, confined to container 0.3% 0.0% 0.0% 0.2%

114 Chimney or flue fire, confined to chimney or flue 0.0% 0.0% 0.1% 0.0%

117 Commercial Compactor fire, confined to rubbish 0.1% 0.0% 0.1% 0.1%

118 Trash or rubbish fire, contained 1.8% 0.4% 1.4% 1.4%

120 Fire in mobile property used as a fixed structure, other 0.2% 0.3% 0.4% 0.3%

121 Fire in mobile home used as fixed residence 0.4% 1.5% 2.6% 1.2%

122 Fire in motor home, camper, recreational vehicle 0.9% 1.2% 1.4% 1.1%

123 Fire in portable building, fixed location 0.5% 0.1% 0.5% 0.4%

130 Mobile property (vehicle) fire, other 2.8% 1.2% 3.7% 2.6%

131 Passenger vehicle fire 31.1% 23.5% 27.9% 28.6%

132 Road freight or transport vehicle fire 0.9% 1.5% 4.6% 2.0%

134 Water vehicle fire 0.2% 0.6% 1.0% 0.5%

135 Aircraft fire 0.0% 0.0% 0.1% 0.0%

136 Self-propelled motor home or recreational vehicle 0.1% 0.4% 0.5% 0.3%

137 Camper or recreational vehicle (RV) fire 0.4% 2.1% 2.3% 1.2%

138 Off-road vehicle or heavy equipment fire 0.2% 0.4% 1.6% 0.6%

140 Natural vegetation fire, other 1.2% 2.2% 1.0% 1.4%

141 Forest, woods or wildland fire 0.1% 0.4% 0.5% 0.3%

142 Brush or brush-and-grass mixture fire 0.7% 5.4% 4.9% 2.8%

143 Grass fire 2.2% 6.5% 6.8% 4.3%

150 Outside rubbish fire, other 1.7% 0.3% 0.4% 1.1%

151 Outside rubbish, trash or waste fire 4.0% 1.5% 1.9% 2.9%

154 Dumpster or other outside trash receptacle fire 1.8% 1.3% 1.4% 1.6%

155 Outside stationary compactor/compacted trash fire 0.1% 0.0% 0.0% 0.0%

160 Special outside fire, other 2.2% 3.2% 1.4% 2.3%

161 Outside storage fire 2.1% 1.6% 1.5% 1.9%

162 Outside equipment fire 0.9% 0.7% 0.4% 0.8%

163 Outside gas or vapor combustion explosion 0.0% 0.0% 0.3% 0.1%

170 Cultivated vegetation, crop fire, other 0.1% 0.1% 0.3% 0.1%

171 Cultivated grain or crop fire 0.1% 0.0% 0.4% 0.1%

172 Cultivated orchard or vineyard fire 0.1% 0.0% 0.4% 0.1%

173 Cultivated trees or nursery stock fire 0.4% 0.1% 0.1% 0.3%

100 Other fire 5.2% 7.1% 1.8% 4.8%

Grand total 100.0% 100.0% 100.0% 100.0%

This report is submitted to the U.S. Fire Administration National Fire Data Center by PG Public Services, LLC in 

accordance with the Performance Work Statement under contract 70FA2019P00000035.