!!

 	



   

 

  



 
	 
 
DISCLAIMER

As the Environmental Protection Agency has indicated in Emission Inventory Improvement

Program (EIIP) documents, the choice of methods to be used to estimate emissions depends on

how the estimates will be used and the degree of accuracy required. Methods using site-specific

data are preferred over other methods. These documents are non-binding guidance and not rules. 

EPA, the States, and others retain the discretion to employ or to require other approaches that

meet the requirements of the applicable statutory or regulatory requirements in individual

circumstances.
 	
 

ACKNOWLEDGEMENT

This document was prepared by Eastern Research Group, Inc. for the Area Sources Committee of

the Emission Inventory Improvement Program and for Charles Mann of the Air Pollution

Prevention and Control Division, U.S. Environmental Protection Agency. Members of the Area

Sources Committee contributing to the preparation of this document are:

Kristin Abraham, West Virginia Department of Environmental Protection

Kwame Agyei, Puget Sound Air Pollution Control Agency

Ray Bishop, Oklahoma Department of Environmental Quality

Dan Brisko, New York State Department of Environmental Conservation

Orlando Cabrera-Rivera, Wisconsin Department of Natural Resources

Andy Delao, California Air Resources Board

Laurel Driver, Emission Factor and Inventory Group, U.S. Environmental Protection Agency

Mark Eastburn, Delaware Department of Natural Resources

Charles Mann, Air Pollution Prevention and Control Division, U.S. Environmental Protection Agency

Sally Otterson, Washington Department of Ecology

Kenneth Santlal, Massachusetts Department of Environmental Protection

Walter Simms, Maryland Department of the Environment

Jack Sipple, Delaware Department of Natural Resources and Environmental Control

Karla Smith-Hardison, Texas Natural Resources Conservation Commission

Angel Thompson, South Carolina Department of Health and Environmental Control

Lee Tooly, Emission Factor and Inventory Group, U.S. Environmental Protection Agency

Also contributing to this document was Joy Bell of Maricopa County, AZ, Environmental Services Department.
 	
  

  			

iv  	
 

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 v


""

Section Page

1 Introduction ....................................................... 18.1-1

2 Source Category Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2-1

2.1 Process Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2-1

2.2 Factors Influencing Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2-1

3 Overview of Available Methods ....................................... 18.3-1

3.1 Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3-1

3.2 Available Methods and Data Requirements......................... 18.3-2

3.3 Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3-3

3.3.1 Application of Controls ................................... 18.3-3

3.3.2 Spatial Allocation ........................................ 18.3-3

3.3.3 Temporal Resolution ..................................... 18.3-3

3.3.4 Other Factors Influencing Emission Estimates ................. 18.3-4

3.3.5 Projecting Emissions ..................................... 18.3-5

4 Preferred Method for Estimating Emissions .............................. 18.4-1

4.1 Structure Fires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4-1

4.1.1 Activity Level Data Collection .............................. 18.4-1

4.1.2 Fuel Loading ........................................... 18.4-2

5 Alternative Methods for Estimating Emissions ............................ 18.5-1

5.1 First Alternative Method ....................................... 18.5-1

5.2 Second Alternative Method .................................... 18.5-2
vi  	
 


""#
""$%

Section Page

6 Quality Assurance/Quality Control ..................................... 18.6-1

6.1 Emission Estimate Quality Indicators ............................. 18.6-1

6.1.1 Data Attribute Rating System (DARS) Scores ................. 18.6-2

6.1.2 Sources of Uncertainty .................................... 18.6-3

7 Data Coding Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.7-1

7.1 Necessary Data Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.7-1

8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.8-1
 	
 vii

&

Tables Page

18.3-1 Summary of Available Methods for Structure Fires .................. 18.3-2

18.3-2 Occurrence of Residential and Non-residential Structure Fires in 1994,

 by Month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3-5

18.4-1 Emission Factors for Structure Fires .............................. 18.4-5

18.6-1 Structure Fires Preferred Method: Local Data ....................... 18.6-2

18.6-2 Structure Fires Preferred Alternative Method 1: Scaled Local Activity . . . 18.6-3

18.6-3 Structure Fires Alternative Method 2: Per Capita Activity ............. 18.6-3

18.7-1 Area and Mobile Source Category Codes for Structure Fires ........... 18.7-2
 	
  

  			

viii  	
 

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 18.1-1



"$
"

This chapter is one of a series of documents developed to provide cost-effective, reliable and

consistent approaches to estimating emissions for area source inventories. Multiple methods are

provided in the chapters to accommodate needs of state agencies with different levels of

available resources and skills; and different levels of needs for accuracy and reliability of their

estimates. More information about the EIIP program can be found in Volume 1 of the EIIP

series, Introduction and Use of EIIP Guidance for Emissions Inventory Development.

Throughout this chapter and other EIIP area source methods chapters, we stress that area source

categories should be prioritized by the inventory planners so that resources can be spent on the

source categories that are the largest emitters, most likely to be subject to regulations or are

already subject to regulations, or require special effort because of some policy reason. 

Prioritization is particularly important for area source inventories, because in some cases, a

difficult to characterize source category may contribute very little to overall emissions and

attempting a high quality estimate for that source category may not be cost effective.

EIIP chapters are written for the state and local air pollution agencies, with their input and

review. EIIP is a response to EPA’s understanding that state and local agency personnel have

more knowledge about their inventory area’s activities, processes, emissions, and availability of

information; and require flexible inventory methods to best use their sometimes limited

resources. These EIIP area source chapters are written as a set of options presented to inventory

professionals capable of using their own experience and judgement to apply the method that best

fits their overall needs and constraints.

This chapter describes the procedures and recommended approaches for estimating emissions

from structure fires. Section 2 of this chapter contains a description of this category. Section 3

of this chapter provides an overview of available emission estimation methods. Section 4

presents the preferred emission estimation methods for structure fires, and Section 5 presents

alternative emission estimation techniques. Quality assurance and quality control procedures are

described in Section 6. Data coding procedures are discussed in Section 7, and Section 8 lists all

references cited in this chapter. 
 	
  

   			

18.1-2  	
 

This page is intentionally left blank.
 	
 18.2-1

 



'($

"

Accidental structure fires result from unintentional actions, arson, or natural events. Structure

fires covered in this chapter are accidental fires that occur in residential and commercial

structures. Accidental industrial fires are not included in this chapter because detailed emission

estimates are required that depend on the materials burned in each fire. Discussions about this

source can be found in two EPA documents (EPA, 1991 and EPA, 1993). A method for

estimating emissions from firefighters’ practice fires is not defined in this chapter, but if it is

necessary to estimate fires from this source, the emission factors and the approach used in this

chapter to determining fuel loading may be useful.

Prescribed fires, agricultural fires, and other forms of open burning are discussed in Chapters 16,

19, and 20 of this volume. Fires covered in these chapters are those that occur because of

intentional actions (excluding arson) and are used to reduce or remove waste materials.

 ) 

$

"

Structure fires covered in this chapter are only those affecting residential or commercial

structures. Accidental fires in yards, of vehicles and telephone poles are not included in this

chapter. Emissions from these types of fires are assumed to be very small.

Structural materials such as insulation and wood, and the contents of structures such as

furniture, carpets, clothing, paper and plastics, can burn in a structure fire. Not all of the

contents and structural materials burn in a fire, rather, the fire burns a portion of the contents and

structural material in the rooms where the fire originates and spreads. The average total material

burned (fuel loading) in a residential fire is estimated to be 1.15 tons (CARB, 1994). The

emission estimation methods discussed here are not valid for industrial fires where chemicals or

industrial materials are burned. Emission estimates for industrial fires should be based on the

type of industrial chemicals burned in each fire.

 ) 
""
"'"

Emissions from structure fires depend on the structure type, physical properties of combustible

materials, and amount of material combusted. Residential and commercial structures will tend

to have differences in mixtures and quantities of combustible materials that will cause
 	
  

   			

18.2-2  	
 

differences in structural fire emissions. The portion of the structure and contents that are burned

is a function of the extent of the fire as well as the available fuel loading.

Process control mechanisms do not exist for accidental structure fires. Programs that improve

public awareness may reduce the number of accidental structure fires. However, the correlation

between such programs and reductions in structure fires is difficult to determine. Fire codes also

serve to reduce emissions from structure fires by requiring reductions in available fuel,

installation of sprinkler systems, and warning systems that improve emergency response time.
 	
 18.3-1

*

+&$

Calculations for estimating emissions for structure fires use an equation based on emission

factors, fuel loading, and activity data. Area source methods can not address all of the

complexity involved in this source category. This section provides an overview of inventory

planning issues for the structure fire source category, outlines the preferred and alternative

methods, and discusses temporal adjustments and emission projection issues.

One of the particular difficulties in estimating emissions from the structure fire source category

is the lack of activity data, in terms of the number of incidents and the quantity of material

burned. When parameters have poorly defined or unavailable information, inventory preparers

will need to make well-educated assumptions.

Preferred and alternative methods in this chapter differ mainly in the level of detail and

area-specificity of the collected fuel loading and activity data. Each method has advantages and

disadvantages in terms of the expense and labor required for the method and the resulting quality

of the emission estimate. The inventory preparer must select a method based on the desired

accuracy of the emissions inventory, the resources available to develop the inventory, and the

potential for the source to contribute to the emissions inventory.

*) 
"""'

The first step in planning for structure fire estimation is to determine if enough fires took place

in the inventory area during the inventory time period to warrant including this source category

in the inventory. Refer to the second alternative method for ways to estimate the scale of

potential emissions from this source.

If it is determined that this source category should be included in the inventory, then the next

step is to choose an emission estimation method. This choice is based on the inventory data

quality objectives (DQOs), the estimated scale of the emissions relative to other area sources,

and availability of the information needed to make the calculations. The available information

and the amount of time and resources needed to collect it should be balanced with the priorities

and DQOs of the inventory to select the appropriate method for the inventory. Refer to EIIP

Volume VI, Quality Assurance Procedures, Sections 2.1 and 2.4 for discussions of inventory

categories and DQOs. Detailed information about this source category should be available from

local fire marshals and public safety departments, or state agencies that oversee public safety. 
 	
  

   			

1 The United States Fire Administration can be contacted at: 16825 South Seton Ave.,

Emmitsburg, MD 21727, phone: (301) 447-1000, or on the Internet:

http://www.usfa.fema.gov/

2 The National Fire Protection Agency can be contacted at: 1 Batterymarch Park,

Quincy, MA, 02269, phone: (617) 770-3000, or on the Internet: http://www.nfpa.org/

18.3-2  	
 

National summary statistics on structure fires are available from the United States Fire

Administration and the National Fire Protection Agency (NFPA).1,2

*) &$"$$,"

The preferred and alternative methods for estimating emissions from structure fires are

summarized in Table 8.3-1. Emission factors are available to estimate particulate matter (PM),

total organics (TOG), methane (CH4), sulfur oxides (SOx), carbon monoxide (CO), hydrogen

cyanide, formaldehyde, acrolein, and nitrogen oxides (NOx) (Butler, 1972; EPA, 1995). To use

these emission factors, the total tons of material burned must be obtained from the activity and

the fuel loading. Calculation parameters to determine the quantity of material burned are

provided with the description of each estimation method.

 )*-

	 
 
 
 
  


Method Description Activity Data

PREFERRED

Collect data for the number of residential and

non-residential structural fires. Use the fuel loading and

emission factors provided.

Calculation: 

Number of fires * Fuel Loading Factor * Emission Factor

 - Number of fires occurring within inventory area

ALTERNATIVE 1

Collect data on the number of fires for a representative

portion of the inventory area and scale to the entire

inventory area based on population. Use the fuel loading

and emission factors provided.

 - Number of fires for superset or subset area

 - Inventory area and subset area population

ALTERNATIVE 2

Use the fires per capita factor provided with the method,

fuel loading and emission factors provided.

 - Inventory area population
 			  	
  

 

 	
 18.3-3

The preferred method uses activity data collected for the entire inventory area. The first

alternative method uses activity data for either a subarea or a similar area that is scaled or

apportioned to the entire inventory area. A similar area is one that has the same population 

density and housing characteristics. The second alternative is based on default per capita

activity.

*)* $"

*)*) 


 
 




No controls are available for this sources. The number of structure fires may be reduced as a

result of public awareness programs. The activity may reflect the impact of such programs.

*)*) 
 




Spatial allocation of the activity data is necessary for the alternative estimation methods. In

those cases, the data must be extrapolated or scaled to the inventory area using a spatial

surrogate. In addition to scaling or extrapolating emissions or activity from one area to another,

emissions or activity may need to be allocated within the inventory area. The recommended

spatial allocation surrogate for structure fires is population.

*)*)* 
 




Seasonal Resolution

Structure fires vary seasonally. Structural fires may increase during cold weather for some

inventory areas due to careless open burning, Christmas lights, or space heater or fireplace use. 

For this reason, it is emphasized that the inventory preparer should investigate the time of

occurrence for these fires relative to the time period of the inventory during the inventory

planning stage.

The preferred method for apportioning structural emissions by season is to use local seasonspecific activity data. The preferred emission estimation method is detailed enough to collect

season-specific data. In this case, information is collected on an incident-by-incident basis, and

emissions are either calculated for each incident or can be apportioned according to locally

specific activity levels.
 	
  

   			

3

 Fire in the United States 1985 - 1994, Ninth Edition, FA - 173/July 1997, or a similar

and more recent publication can be ordered from: United States Fire Administration,

Federal Emergency Management Agency, Publications Center, Room N310, 16825

South Seton Avenue, Emmitsburg, MD 21727, or ordered through the Web site:

http://www.usfa.fema.gov/

18.3-4  	
 

Alternative apportioning methods for structure fires are, in order of preference:

 Collect data from another area, either a subset, superset, a similar area, or from a

year other than that of the inventory for the inventory area. Using this approach

should include an effort to match the surrogate area or year to the inventory area

and year in terms of the factors that influence the frequency and severity of

accidental fires;

 Use estimates of activity from a local expert, such as the fire marshal or public

safety office; or

 Use the seasonal distribution reported in the National Fire Data Center’s report, 

Fire in the United States.

3

 An example for 1994 of the monthly distribution of

residential and nonresidential structure fires is provided in Table 18.3-2. Please

note that this distribution represents national averages, and the distribution of

occurrences within a particular inventory area may differ. Non-residential fires

for this report are classified as industrial and commercial properties, institutions,

educational establishments, mobile properties, and properties that are vacant or

under construction.

Daily Resolution

Structure fires can be expected to take place seven days a week. Structure fire occurrences are

consistent through the week.3 The preferred and alternate methods discussed above for attaining

seasonal resolution apply for daily resolution as well.

*)*).  
 
 


 


Natural disasters may affect structure fire activity and the resulting emissions. Natural disasters

such as hurricanes, tornadoes, ice storms or floods may cause electricity outages which 

increases the use of fire in residences and increase the risk of structure fires. If the per capita

activity factor is used to develop the inventory, expert opinion may be required to estimate the

impact of natural disasters on structural fire activity.
 			  	
  

 

 	
 18.3-5

 )*- 

 
 

  "
-

  
 
 //.0

	 
a

Month

 Residential Structure Fires

%

Non-Residential Structure Fires

%

January 12.6 9.0

February 9.8 7.8

March 9.1 9.0

April 8.2 9.3

May 7.4 8.6

June 7.5 8.9

July 7.4 8.5

August 6.9 7.8

September 6.6 7.4

October 7.5 8.1

November 8.0 7.8

December 9.0 7.7

Total 100 99.9

a

 Source: FEMA, 1997. 

*)*)1 


 




A discussion about developing growth factors and projecting emission estimates can be found in

Section 4 of Chapter 1 of this volume, Introduction to Area Source Emission Inventory

Development.

Projecting emissions for structure fires usually will take into account only changes in activity

levels. Sources of variation in structural fires include:

 Changes in population, either in total population or population shift in residential

housing types; and 
 	
  

   			

18.3-6  	
 

 Changes in fire codes, building codes, or inspection policies that reduce the risk

of fires.
 	
 18.4-1

.


$$

"'"

Emissions from structure fires are determined by the incidence of fires and the amount and the

type of material burned. The preferred method presented here is a set of guidelines for

identifying the parameters that need to be collected, where the information can be located, and

the assumptions that can be used in order to develop reasonable estimates. There is no universal

data source that can be used for every inventory to estimate emissions for this source category. 

When lists of potential data sources are given as part of a method, one or more of these data

sources may need to be contacted.

As with all area source inventory categories, documentation should be maintained for data

collected, assumptions, information contacts, and calculations. Because preparation of an

inventory for this source category requires making assumptions in order to develop activity

levels, the basis for all assumptions must be well documented.

For structure fires, costs and labor efforts are highest the first time that the preferred method is

used. Subsequent updates to the inventory can be done using a local activity adjustment factor,

if a suitable scaling surrogate can be identified. Subsequent inventories should take advantage

of the data handling and quality assurance/quality control (QA/QC) routines put into place the

first time the method was used. See discussions of surveys for area sources in Volume 1 of the

EIIP series and in Chapter 1 of this volume for more information.

.) 


The preferred method for estimating emissions from structure fires should be used if more

detailed emission estimates are needed for planning, or the source category is a high priority. If

the information needed for this method can be easily compiled, then it may be worthwhile to

develop locality-specific activity surrogate factors and fuel loadings. 

.)) 

	  $ 





The preferred method for structural fires uses the statistics for the total number of fires in an

inventory area. Structure fire statistics by month are preferred for seasonal inventories such as
 	
  

   			

18.4-2  	
 

ozone or CO inventories. If the default fuel loading factor is being used, then data on the

structure types that are involved in the fires need not be collected. 

Potential information sources for locality-specific structure fires activity data are local or state

fire marshals or local or state fire and public safety departments. Reporting and availability of

information about structure fires will vary by locality. These contacts may also be able to

provide estimates of material loss for the inventory area, either as a portion of the structure or as

tons burned per fire.

When collecting information about occurrences of structure fires, be certain that the definition of

a structure fire counted by the fire marshal is actual fires and not the number of emergency calls. 

Also, clarify the size of the fires if possible. Structure fires can be very small, such as electrical

wiring or cooking fires, or they can be large, consuming the entire structure. Most reported fires

will be small. Additionally, if fires that take place on residential property, such as garage fires,

are classified separately from other residential fires, then statistics for garage fires should be

obtained and included in the activity used to estimate emissions. Descriptions of the statistics

will also assist in determining if the majority of fires within the inventory area are accounted for

by the fire marshal.

.))  



Fuel loading estimates are necessary to convert the activity (number of fires) to units compatible

with the emission factors, which are based on the weight of material burned. The material

burned will be a function of the total material available and the duration of the fire. The total

combustible material depends on the intended use of the structure. Structures can be broadly

classified as residential and non-residential, which includes commercial and institutional

structures. Residential structures can be further classified as single family and multi-family

dwellings. The state or local fire marshal may be able to provide estimates of material loss for

the inventory area, either as a portion of the structure or tons burned per fire. However, losses

are usually reported in terms of the dollar value lost.

The most conservative fuel loading estimate will assume that all the combustible material is

burned. However, this is not likely for most structural fires. Locality-specific fuel loading

factors for different structure types would improve the emission estimate, but a fuel loading

factor of 1.15 tons per fire using a method developed by California Air Resources Board
 	
 
    

4 This method is derived from the CARB Emission Inventory Procedural Manual, Vol. III:

Methods for Assessing Area Source Emissions, developed by the California Environmental

Protection Agency: Air Resources Board. The latest version of the manual is available on

the internet at: http://www.arb.ca.gov/emisinv/areasrc/areameth.htm

5

 The U.S. Census Bureau maintains an Internet Web site at: http://www.census.gov/

 	
 18.4-3

Combustible Structural Materials  (Structural Mass Contents)  Loss Percentage (18.4-1)

Combustible Structural Materials (tons) 

Combustible

Structural Mass

lb/sq ft



Square Footage

per Residence

sq ft

÷ 2000 lb/ton (18.4-2)

Combustible Structural Materials = (16.3 lb/sq ft  1350 sq ft) ÷ 2000 lb/ton

= 11 tons

(18.4-3)

(CARB) is an acceptable default value for all types of structures.4

 The CARB approach to

developing a local fuel loading factor could be used for other inventory areas.

The fuel loading factor is based on an estimate of combustible structural content for a typical

residence, and an estimate of the average loss per fire. Combustible structural content is the sum

of the combustible structural materials and the building contents. Fuel loading is a percentage of

the total combustible structural content. Fuel loading is calculated:

Combustible structural mass is calculated by multiplying an estimate of combustible material

per square foot in the building structure by the average residence’s square footage:

CARB’s estimate for combustible structural mass is 16.3 pounds per square foot. Assuming an

average residence size is 1350 square feet, combustible structural materials would be:

Average residence size can vary from region to region. Inventory preparers are encouraged to

identify a local average residence size. The U.S. Census Bureau5 reports that the national 

median residence size in 1995 was 1732 square feet.

Combustible building contents are calculated by multiplying an estimate of contents per square

foot in the building structure by the average residence’s interior floor space:

      	


18.4-4  	
 

Combustible Building Contents (tons) 

Combustible

Building Contents

lb/sq ft



Floor Space

per Residence

sq ft

÷ 2000 lb/ton (18.4-4)

Combustible Building Contents = (7.91 lb/sq ft  1200 sq ft) ÷ 2000 lb/ton

= 4.7 tons

(18.4-5)

Fuel

Loading

tons/fire

=

Combustible

Structural Materials

tons



Combustible

Building Contents

tons



Loss

Rate

%

= (11 tons 4.7 tons)  0.073

= 1.15 tons/fire

(18.4-6)

CARB’s estimate for combustible building contents is 7.91 pounds per square foot. Assuming

an average floor space per residence is 1200 square feet, combustible building contents would

be:

CARB estimates that the average loss per fire is 7.3 percent of the combustible structural

content. The average loss is based on monetary losses reported by FEMA and the average value

of residences reported by the California Association of Realtors. The loss rate is applied to the

estimated total combustible structural content to obtain a fuel loading per fire:

The percent loss was estimated based on monetary losses. Fire marshalls typically report losses

as dollar loss statistics. There are, however, several weaknesses in using the dollar loss to

estimate the percentage of material combusted. First, material may be damaged by smoke or

sprinkler systems and counted as loss even though it is not combusted. Second, the value of

contents or structures is not directly proportional to the mass. Finally, the percent monetary loss

is the average loss divided by the average dollar value of structures. Since these two values do

not come from the same data source, there can be discrepancies in how they are determined. 

Despite these weaknesses in representing material combusted, percent dollar losses may be the

most practical way to represent the percentage of material burned in a fire.

Emission Factors

Emission factors for structural fires are presented in Table 18.4-1. The emission factors given

are assumed to apply to all structure types.
 	
 
    

 	
 18.4-5

Emissions  Emission factor Activity Fuel loading (18.4-7)

 

	
 	
 	
 	

 


Pollutant Factor (lb/ton burned) Reference

PM 10.8 CARB, 1994a

TOG 13.9 CARB, 1994a

Hydrogen cyanide 35.49 EPA, 2000

Formaldehyde 1.02 EPA, 2000

Acrolein 4.41 EPA, 2000

Hydrochloric acid 15.11 EPA, 2000

VOC 11 EPA, 1991

NOX 1.4 EPA, 1991

CO 60 EPA, 1991

a See footnote 4 in the text for more information about this document.

Emission Calculations

Emissions from structure fires are determined by multiplying the number of reported structure

fires by the fuel loading per fire and the emission factors from Table 18.4-1:

where: 

Emissions = Emissions for a given pollutant (lb emitted)

Emission factor = Emission factor for a certain pollutant (lb emitted/ton

burned)

Activity = Number of fires within the inventory area (fires)

Fuel loading = Fuel loading per fire (ton burned/fire)

      	


18.4-6  	
 

Example 18.4-1:

County A has had 115 structure fires reported for the inventory year. Information about the

structure types and the extent of the material burned in each fire was not collected, so the

default fuel loading of 1.15 tons per fire was used. The PM emissions for structure fires in

County A are:

Emissions = 10.8 lb/ton * 115 fires/year * 1.15 tons/fire

= 1,428 lbs/year

= 0.71 tons/year

If emissions are being calculated for an inventory season, and local season-specific activity is

not available, emissions can be apportioned using any of the three alternative apportioning

approaches from Section 3.3.3 of this chapter. Example 18.4-1 shows a typical calculation for

one county in an inventory area.
 	
 18.5-1

Fires in county  Fires in state county population/state population (18.5-1)

1

"$

"'"

Alternative methods require less effort and less cost, but may result in estimates that are less

detailed and/or less locality-specific. The choice of a preferred over an alternative method will

be determined by the DQOs and budget for the inventory. For this source category in particular, 

the significance of sources to the total area emissions should be considered when choosing

methods.

During the planning stage of the inventory, research should be done to identify data sources and

other factors that might influence emissions from the source category. See Section 3.1 of this

chapter for specific issues.

1) "$

The first alternative method for estimating emissions from structural fires uses the same

emission factors and same default fuel loading described in the preferred method for this

category. The first alternative method relies on activity data from a larger inventory area that is

apportioned to the inventory area, or on activity data from a subarea that is scaled to the

inventory area. Activity information may be available from state or local fire marshals and

public safety departments, neighboring inventory areas, or from a subset of the inventory area.

When activity data is available for the whole state, or an area larger than the inventory area, then

the number of fires for the state will need to be apportioned to the county level. Population can

be used to apportion the number of fires. The equation to apportion the number of fires is:

If activity data is scaled from a subarea or similar area, population is also used for scaling. 

When information is collected for a small area and scaled to the inventory area, the number of

fires that occurred in that subarea can be collected from the few fire departments that serve that

subarea. The area that is used as a source of activity data should be similar to the entire

inventory area. According to statistics in the report, Fire in the United States: 1985 - 1994

(FEMA, 1997), cooking and heating are the leading causes of residential structure fires. As a
 	
  

   			

6 Census data is available through the U.S. Bureau of Census, Commerce Department,

Washington, DC, or through the Web site: http://www.census.gov.

7 U.S. Bureau of Census Web site: http://www.census.gov.

18.5-2  	
 

Fires in county  Fires in subarea county population/subarea population (18.5-2)

result, heating types may have some influence on fire incidences, and structure fire activity from

an area that has distinctly different residential heating types than the inventory area may not be a

good match. The U.S. Bureau of Census can provide data on population and heating types.6

 

The scaling equation for structure fire activity from a subarea to a county in the inventory area

is:

After activity data is scaled or apportioned to the inventory area, the default fuel loading factor,

emission factors, and emission calculations are the same as those described for the preferred

method.

Use any of the three alternative seasonal apportioning methods listed in Section 3.3.3 of this

chapter. 

1) 
"$"$

The second alternative method for estimating emissions from structural fires uses the same

emission factors and the same fuel loading that is described in the preferred method. However,

for this method, the activity is obtained by multiplying a national average factor of fires per

capita by the inventory area population. The number of fires per capita is based on an estimated

602,500 total fires reported for 1994 (FEMA, 1997) and a U.S. population of 260.4 million

(1994 U.S. population)7

, averaging 2.3 fires per 1,000 people. If more recent data on total fires

becomes available, then those data can be used to calculate a more recent per capita activity

factor. Inventory area population is multiplied by the per capita factor to get the estimated

number of structure fires in the area.

After the inventory area activity level is determined, emission calculations are the same as those

described for the prescribed method, using the default fuel loading of 1.15 tons per fire and the

emission factors in Table 18.4-1. Example 18.5-1 shows typical calculations. 
 			  	
  

 

 	
 18.5-3

Example 18.5-1:

County B’s population is 0.5 million people. The structure fire activity is determined to be:

Activity = population * fires/population

= 0.5 million people * 2.3 fires/ 1,000 persons

= 1,150 fires

PM emissions can then be calculated as: 

Emissions = emission factor * activity * fuel loading 

= 10.8 lb/ton * 1,150 fires/year * 1.15 tons/fire

 = 14,283 lbs/year

Use any of the three alternative seasonal apportioning methods listed in Section 3.3.3 of this

chapter. 
 	
  

   			

18.5-4  	
 

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 18.6-1

2

,("
3,(


"

Data collection and handling for the structure fire source category should be planned and

documented in the Quality Assurance Plan. Assumptions used and decisions made concerning

data sources should be documented. Refer to the Quality Assurance Quality Control (QA/QC)

section of Chapter 1, Introduction to Area Source Emission Inventory Development, of this

volume, and the QA volume (VI) of the Emission Inventory Improvement Program (EIIP) series.

Potential pitfalls when developing emissions estimates:

 Incomplete or inaccurate reports of the number of fires;

 Reporting that covers a geographic area that is either larger or smaller than that

for the inventory; and

 Inaccurate estimates of the material burned for each fire. 

Potential errors common to many area source methods are calculation errors, including unit

conversion errors and data transfer errors.

2) ",("$


In this chapter, three estimation methods are presented. The preferred method uses local data on

fire incidences collected for the entire inventory area, fuel loading factors developed from local

data or default factors from CARB, and a set of emission factors compiled from multiple

sources (see Table 18.4-1). The first alternative method uses local data on fire incidences

collected for a subset of the inventory area, the CARB default fuel loading factors, and the same

set of emission factors as the preferred method. The second alternative method uses the national

average factor of fires per capita to develop the activity, the CARB default fuel loading factor,

and the emission factors used for the preferred and first alternative methods. Using the most

accurate activity data, in the form of fire incidences and fuel loading, is the way to develop the

best emission estimates. However, inventory planners should consider the costs of data

collection versus the benefit of a more accurate estimate for a very small emissions source. 
 	
  

   			

18.6-2  	
 

2)) $ 
 
 	 #$% 


The Data Attribute Rating System (DARS) has been developed as a tool to rate emission

inventories. A description of the system and the EIIP recommendations for its use can be found

in Appendix F of EIIP Volume VI, Quality Assurance Procedures. The following discussion

uses the DARS rating system as a way to compare the estimation approaches presented in this

chapter and analyze their strengths and weaknesses. 

The DARS scores for the three estimation methods are summarized in Tables 18.6-1 through

18.6-3. Variation between scores depends on the activity data used. All scores assume that

good QA/QC measures were performed and that no significant deviations from the prescribed

methods were made.

 )2-

 



 
	 
 $

Attribute

Scores

Factor Activity Emissions

Measurement 0.5 0.6 0.3

Source specificity 0.7 0.4 0.28

Spatial congruity 0.7 0.7 0.49

Temporal congruity 0.7 0.9 0.63

Composite 0.65 0.65 0.43
 			  	
  

 

 	
 18.6-3

 )2- 

 



 
 	  
 

	

Attribute

Scores

Factor Activity Emissions

Measurement 0.5 0.5 0.25

Source specificity 0.7 0.4 0.28

Spatial congruity 0.7 0.6 0.42

Temporal congruity 0.7 0.9 0.63

Composite 0.65 0.6 0.4

 )2-*

 



 
 	
 

 

	

Attribute

Scores

Factor Activity Emissions

Measurement 0.5 0.4 0.2

Source specificity 0.7 0.3 0.21

Spatial congruity 0.7 0.5 0.35

Temporal congruity 0.7 0.8 0.56

Composite 0.65 0.5 0.33

2)) 
 
 
	

Another way to assess the emission methods is to examine the associated uncertainty. For the

preferred and first alternative methods, activity data is derived from local data, and can be

treated as survey data. Uncertainty for survey data can be quantified (see Chapter 4 of

Volume VI of the EIIP series). The uncertainty for the second alternative method, using fires

per 1,000 people, can be calculated by referring to the supporting documentation for the national

fire estimates (FEMA, 1997). This uncertainty will only pertain to the national estimate. 
 	
  

   			

18.6-4  	
 

Additional uncertainty will be introduced by scaling the activity estimate to an inventory area,

where average conditions of fire incidence may not exist. 

A source of uncertainty for all of the methods is the fuel loading factor. No two fires will burn

the same amount of material, and material types and structure sizes vary from region to region in

the United States, as well as within a single county. The default fuel loading factor provided

here is an average of a highly variable factor, and should be understood to represent a practical

way to estimate area-wide emissions.

Emission factors also contribute to overall uncertainty. Emission rates of any pollutant for this

source category will be highly variable, given that the process is uncontrolled combustion of

mixed materials, and is not well constrained. This uncertainty cannot be quantified.
 	
 18.7-1

4

$
$"'

$

The inventory preparer should check the EPA website (http://www.epa.gov/ttn/chief/) for the

latest information (codes) available to characterize emission estimates from structure fires. A

complete list of Source Classification Codes (SCC) can be retrieved at 

http://www.epa.gov/ttn/chief/codes/. Table 18.7-1 lists the applicable SCCs for structure fires. 

Available codes and process definitions influence and help guide the preparation of emission

estimates for this category. Data transfer formats should be taken into account when an

inventory preparer plans for data collection, calculation, and inventory presentation. Consistent

categorization and coding will result in greater continuity between emission inventories for use

in regional and national scale analyses. 

4)"
($"

If the category emissions data will be transferred to EPA for incorporation into the national

criteria and toxics air pollutant inventory, specific data transfer formats are acceptable. The

acceptable data transfer format(s) are described and available for download at

http://www.epa.gov/ttn/chief/net/. The acceptable data transfer formats contain the data

elements necessary to complete the data set for use in regional or national air quality and human

exposure modeling. The inventory preparer should review the area source portion of the

acceptable file format(s) to understand the necessary data elements. The EPA describes its use

and processing of the data for purposes of completing the national inventory, in its Data

Incorporation Plan, also located at http://www.epa.gov/ttn/chief/net/.
 	
  

   			

18.7-2  	
 

 )4-

  

 
 

	 

 
  


Process Description Source Category Code

Structure Fires - total 28-10-030-000
 			  	
  

 

 	
 18.7-3

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 18.8-1



"


CARB. 1994. Emission Inventory Procedural Manual, Vol. III: Methods for Assessing Area

Source Emissions. California Environmental Protection Agency: Air Resources Board.

EPA. 2000. National Toxics Inventory. U.S. Environmental Protection Agency, Office of Air

Quality Planning and Standards. Research Triangle Park, N.C.

EPA. 1998. National Air Pollutant Emission Trends, Procedures Document, 1900 - 1996. 

EPA-454/R-98-008. U.S. Environmental Protection Agency, Office of Air Quality Planning and

Standards. Research Triangle Park, N.C.

EPA, 1995. Development of Area Source Hazardous Air Pollutant Inventories, Volume 1: Air

Toxic Emission Inventories for the Chicago Area. U. S. Environmental Protection Agency,

Office of Air Quality Planning and Standards. Research Triangle Park, North Carolina.

EPA. 1994. AIRS Database. U.S. Environmental Protection Agency, Office of Air Quality

Planning and Standards. Research Triangle Park, NC.

EPA, 1993. Identification and Characterization of Five Non-Traditional Source Categories:

Catastrophic/Accidental Releases, Vehicle Repair Facilities, Recycling, Pesticide Application

and Agricultural Operations. EPA-600/R-93-045. U.S. Environmental Protection Agency, Air

and Energy Engineering Research Laboratory. Research Triangle Park, North Carolina.

EPA. 1991. Procedures for the Preparation of Emission Inventories for Carbon Monoxide and

Precursors of Ozone, Vol. I. EPA-450/4-91-016. U. S. Environmental Protection Agency,

Office of Air Quality Planning and Standards. Research Triangle Park, North Carolina.

FEMA. 1997. Fire in the United States: 1985-1994, Ninth Edition (FA-173/July 1997). Federal

Emergency Management Agency, United States Fire Administration, National Fire Data Center.

Emmitsburg, MD.
 	
  

   			

18.8-2  	
 

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