7.14-1

SECTION 7.14

STRUCTURE AND AUTOMOBILE FIRES

(Updated March 1999)

METHODS AND SOURCES

These categories are used to inventory the combustion emissions from structure,

mobile home, and automobile fires. The Structure fires category includes residential

and commercial structures as well as mobile home fires. The criteria pollutant

emissions for 1996 are presented in Table II (Structure Fires) and Table III

(Automobile Fires). Estimates of building, mobile home, and automobile fires in 1996

were based on data from an annual report generated by the California Fire Incident

Reporting System (CFIRS). 1

STRUCTURE FIRES

For structure fires, the average amount of structure and content material burned are first

estimated. An average percent structural loss per fire was calculated by dividing the

total monetary damage due to fires by the product of the average value of a residence in

California and the number of structure fires.2

 The average loss per fire is estimated to

be 7.3 percent. This estimate can be applied to structure loss and content loss.

Based on census data, the average size of existing homes in California is estimated to

be 1,649 square feet. 3 The average residence has approximately 11,000 board feet of

lumber in the structure, according to information provided by the National Association of

Home Builders. 4

ARB staff assumed an average of one ton of material per 1,000 board feet. Therefore,

an average residence has approximately 11 tons of combustible material. Assuming a

rate loss of 7.3 percent, the structure loss is estimated to be 0.80 tons per fire.

EMISSION INVENTORY SOURCE CATEGORY

 Miscellaneous Processes/Fires

EMISSION INVENTORY CODES (CES CODES) AND DESCRIPTION

 660-656-0200-0000 (47324) Structure Fires

 660-658-0200-0000 (57307) Automobile Fires
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Next, the amount of content material burned is estimated. The National Bureau of

Standards lists the combustible contents per square foot of the functional areas of the

average home. 5 These figures are then multiplied by the percent of fires estimated to

originate within each of these functional areas, 1

 and the products are then added to

obtain the weighted average of 7.91 pounds per square foot.

Origin of Combustibles Weighted Average

Functional Area fires(%) (lbs/sq. ft.) (lbs/sq. ft.)

Bedroom 28.96 10.4 3.012

Sleeping Area 0.20 10.4 0.021

Dining Area 2.20 7.2 0.159

Kitchen 53.92 6.8 3.667

Bathroom 6.32 7.0 0.443

Laundry 8.08 7.2 0.582

Office 0.17 7.9 0.013

Other 0.13 9.6 0.012

 7.909

With a 7.3 percent loss rate, an average of 7.91 pounds of combustible contents per

square foot, and assuming an average floor space of 1649 square feet, the content loss

for the average residential fire would be:

[(1649) x (0.073) x (7.91)] / 2000 = 0.48 tons/fire

Total amount burned per residential fire (fuel loading) = structure loss + content loss

 = 0.80 + 0.48

 = 1.28 tons/fire

Structure fire emission factors in pounds per ton of material burned for TOG, CO and

PM have been obtained from tests on the burning of model wood buildings. 6

 The

emission factor for NOx is assumed to be similar to that listed in AP-42 for municipal

refuse. 7

 These emission factors have been converted to units of pounds per fire using

the factor of 1.28 tons/fire.

 Emission Factors for Structural Fires

TOG CO NOx SOx PM

Pounds/Ton 13.9 168.0 4.0 0 10.8

Pounds/Fire 17.8 215.0 5.1 0 13.8

CFIRS structure fires data is available on the county level. For those instances where

an air basin splits a county, emissions estimates are apportioned based on total housing
7.14-3

units as estimated by the California Department of Finance (DOF).

AUTOMOBILE FIRES

The emission factors for automobile fires are taken from AP-42, Sections 2.2.2 and

2.4.2. Table 2.2-1 of AP-42 lists the emission factors for uncontrolled auto body

incineration. These are based on automobiles that have been partially stripped (tires,

seats, etc. removed). Table 2.4-1 of AP-42 lists the emission factors for open burning of

automobile components. These emission factors are for upholstery, belts, hoses, and

tires burned in common.

It has been assumed that tires are burned in 60 percent of the automobile fires. 

Composite emission factors have been calculated as a weighted average of the

emission factors listed in Table 2.2-1 and 2.4-1 of AP-42. It has been assumed that the

average car body weighs 3,700 pounds and the components weigh 500 pounds. The

composite emission factors are listed below. Their derivation is presented in Table I.

Emission Factors for Automobile Fires (lbs/fire)

TOG CO NOx SOx PM

7.21 21.25 0.7 0 17

For automobile fires, sub-county splits between air basins are based on population

estimates from DOF.

ASSUMPTIONS

1. The emission factors that have been derived for structure fires are also valid for

mobile home fires.

2. An average residence is constructed with approximately 11 tons of combustible

material.

3. An average residence covers an area of 1,649 square fee.

4. The tires are burned in 60 percent of the automobile fires.

5. The average car body weighs 3,700 pounds.

6. The components on an average car weigh 500 pounds.

7. The estimates of structural loss rate (7.3%) and content loss rate (7.91 lb/sq. ft.)

continue to be applicable.
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COMMENTS AND RECOMMENDATIONS

Emission factors for mobile home and commercial structure fires may be significantly

different from those for residential fires. Little data are available; therefore, the emission

factors for mobile home fires and commercial structure fires are assumed to be the

same as for residential structure fires. The emission factors for oxides of nitrogen,

which are actually for open burning of municipal refuse, may not be the best estimate

for structure fires.

A more accurate estimate of the percentage of cars that burn completely (tires included)

needs to be determined, since most emissions are associated with automobile

component and tire combustion.

CHANGES IN METHODOLOGY

The estimate of the average size of a residence in California has been increased based

on census data. This increase resulted in a larger estimate of the amount of material

burned per fire (fuel loading). As a result, emission factors in pounds of pollutant per

fire have also been increased.

Emission estimates have been adjusted to account for the newly formed Salton Sea Air

Basin. 

DIFFERENCES BETWEEN 1995 AND 1996 EMISSION ESTIMATES

The differences between the 1995 and 1996 emission estimates for structure fires and

automobile fires are primarily due to the difference in the numbers of fire incidents. 

Increases in emission factors have also affected emission estimates.

TEMPORAL ACTIVITY

For both categories, the annual activity and the weekly activity are uniform. The daily

activity occurs primarily during daylight hours.
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SAMPLE CALCULATIONS

To calculate the emissions from Structural Fires (CES 47324), and Automobile Fires

(CES 57307) for Sacramento County in the Sacramento Valley air basin:

Number of Structural Fires = 1,546

Number of Automobile Fires = 1,877

Emissions = [Process Rate (# of Fires)] x (Emission Factor) / 2000 lbs/ton

The process rate and emissions for Sacramento County are summarized below:

Process Rate Emissions (tons/yr) 

 Type of Fires (# of Fires) TOG CO NOx SOx PM

Structural Fires 1,546 13.7 166.2 3.94 0 10.7

Automobile Fires 1,877 6.8 19.9 0.66 0 16.0
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REFERENCES

1. California State Fire Marshall, California Fire Incident Reporting System, 1996.

2. California State Fire Marshall, California Fire Incident Reporting System, 1991.

3. Sue Lord, American Housing Survey Branch, Census Bureau, 1999.

4. National Association of House Builders, http://www.nahb.com/mub.html.

5. National Bureau of Standards, Combustible Contents in Buildings.

6. Butler, C.P. and Darley, E.E. “Fires Dynamics of Model Wood Buildings,” Fire and

Flammability, Vol. 3, p. 336 (October 1972).

7. U.S. Environmental Protection Agency, Compilation of Air Pollutant Emission

Factors, AP-42, Section 2.2 and 2.4. (April 1973).

UPDATED BY

Carolyn Lozo

March 1999
7.14-7

Table I

Derivation of Emission Factors for Automobile Fires

The emission factors for uncontrolled auto body incineration (Table 2.6-1 of AP-42, 1/95) are:

Emission Factors for Auto Body (lbs/car)

TOG CO NOx SOx PM

0.91 2.5 0.1 0 2.0

The emission factors for automobile components (Table 2.5-1 of AP-42), including upholstery,

belts, hoses and tires, are listed in terms of lbs/ton of components burned and must be

multiplied by the weight of components per car. If the components per car are assumed to be

500 lbs, the emission factors for components in terms of lbs/car can be converted as show

below.

Weight of components = 500 lbs/car

 = 0.25 tons/car

PM emission factor = (100 lbs/ton components) x (0.25 tons components/car)

 = 25 lbs/car

 Emission Factors for Components (lbs/car)

TOG CO NOx SOx PM

10.5 31.25 1.0 0 25

Composite emission factors, assuming that tires are burned in 60% of automobile fires, were

calculated as follows:

Composite EF = [EF (body) + EF (components)] x 0.6 + [EF (body)] x 0.4

The weighted composite emission factors are listed below:

 Composite Emission Factors (lbs/fire)

TOG CO NOx SOx PM

 7.21 21.25 0.7 0 17.0
7.14-8

Table II

1996 Area Source Emissions

Activity: Unspecified Activities

Process: Structure Fires

Entrainment: Solid Material Combustion

Dimn:

CES: 47324

Process Rate Unit: Fires

AB County Process

Rate

TOG Emis.

(Tons / Year)

CO Emis.

(Tons / Year)

NOX Emis.

(Tons / Year)

SOX Emis.

(Tons / Year)

PM Emis.

(Tons / Year)

GBV ALPINE 1 0.01 0.16 0.00 0.00 0.01

INYO 2 0.03 0.33 0.01 0.00 0.02

MONO 0 0.00 0.00 0.00 0.00 0.00

LC LAKE 44 0.60 7.21 0.17 0.00 0.46

LT EL DORADO 17 0.23 2.78 0.07 0.00 0.18

PLACER 2 0.03 0.33 0.01 0.00 0.02

MC AMADOR 9 0.12 1.47 0.04 0.00 0.09

CALAVERAS 30 0.41 4.91 0.12 0.00 0.32

EL DORADO 62 0.84 10.16 0.24 0.00 0.65

MARIPOSA 52 0.70 8.52 0.20 0.00 0.55

NEVADA 50 0.68 8.19 0.20 0.00 0.53

PLACER 8 0.11 1.31 0.03 0.00 0.08

PLUMAS 3 0.04 0.49 0.01 0.00 0.03

SIERRA 0 0.00 0.00 0.00 0.00 0.00

TUOLUMNE 90 1.22 14.74 0.35 0.00 0.95

MOJ KERN 92 1.25 15.07 0.36 0.00 0.97

LOS ANGELES 169 2.29 27.68 0.66 0.00 1.78

RIVERSIDE 17 0.23 2.78 0.07 0.00 0.18

SAN BERNARDINO 355 4.81 58.15 1.38 0.00 3.75

NC DEL NORTE 29 0.39 4.75 0.11 0.00 0.31

HUMBOLDT 58 0.79 9.50 0.23 0.00 0.61

MENDOCINO 74 1.00 12.12 0.29 0.00 0.78

SONOMA 173 2.34 28.34 0.67 0.00 1.83

TRINITY 1 0.01 0.16 0.00 0.00 0.01

NCC MONTEREY 197 2.67 32.27 0.77 0.00 2.08

SAN BENITO 25 0.34 4.10 0.10 0.00 0.26

SANTA CRUZ 162 2.20 26.54 0.63 0.00 1.71

NEP LASSEN 13 0.18 2.13 0.05 0.00 0.14

MODOC 2 0.03 0.33 0.01 0.00 0.02

SISKIYOU 8 0.11 1.31 0.03 0.00 0.08

SC LOS ANGELES 5119 69.36 838.49 19.96 0.00 54.01

ORANGE 1470 19.92 240.79 5.73 0.00 15.51

RIVERSIDE 755 10.23 123.67 2.94 0.00 7.97

SAN BERNARDINO 1169 15.84 191.48 4.56 0.00 12.33

SCC SAN LUIS OBISPO 143 1.94 23.42 0.56 0.00 1.51

SANTA BARBARA 152 2.06 24.90 0.59 0.00 1.60

VENTURA 7 0.09 1.15 0.03 0.00 0.07

SD SAN DIEGO 1813 24.57 296.97 7.07 0.00 19.13

SF ALAMEDA 236 3.20 38.66 0.92 0.00 2.49

CONTRA COSTA 961 13.02 157.41 3.75 0.00 10.14

MARIN 201 2.72 32.92 0.78 0.00 2.12

NAPA 205 2.78 33.58 0.80 0.00 2.16

SAN FRANCISCO 408 5.53 66.83 1.59 0.00 4.30

SAN MATEO 346 4.69 56.67 1.35 0.00 3.65

SANTA CLARA 661 8.96 108.27 2.58 0.00 6.97

SOLANO 3 0.04 0.49 0.01 0.00 0.03

SONOMA 152 2.06 24.90 0.59 0.00 1.60

SJV FRESNO 1310 17.75 214.58 5.11 0.00 13.82

KERN 400 5.42 65.52 1.56 0.00 4.22

KINGS 146 1.98 23.91 0.57 0.00 1.54

MADERA 143 1.94 23.42 0.56 0.00 1.51

MERCED 209 2.83 34.23 0.82 0.00 2.20

SAN JOAQUIN 192 2.60 31.45 0.75 0.00 2.03

STANISLAUS 482 6.53 78.95 1.88 0.00 5.09

TULARE 592 8.02 96.97 2.31 0.00 6.25

SS IMPERAIL 82 1.11 13.43 0.32 0.00 0.87

RIVERSIDE 187 2.53 30.63 0.73 0.00 1.97

SV BUTTE 356 4.82 58.31 1.39 0.00 3.76

COLUSA 1 0.01 0.16 0.00 0.00 0.01

GLENN 4 0.05 0.66 0.02 0.00 0.04

PLACER 39 0.53 6.39 0.15 0.00 0.41

SACRAMENTO 1184 16.04 193.94 4.62 0.00 12.49

SHASTA 293 3.97 47.99 1.14 0.00 3.09

SOLANO 2 0.03 0.33 0.01 0.00 0.02

SUTTER 43 0.58 7.04 0.17 0.00 0.45

TEHAMA 102 1.38 16.71 0.40 0.00 1.08

YOLO 124 1.68 20.31 0.48 0.00 1.31

YUBA 29 0.39 4.75 0.11 0.00 0.31

TOTAL 

 

21466 290.86 3516.11 83.72 0.00 226.46

Fraction of Reactive Organic Gases (FROG): .7500 (Reactive Organic Gases (ROG) Emissions = TOG X FROG)

Fraction of PM10 (FRPM10): .9800 (PM10 Emissions = PM X FRPM10)
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Table III

1996 Area Source Emissions

Activity: Unspecified Activities

Process: Unplanned Fires

Entrainment: Solid Material Combustion

Dimn: Auto Body

CES: 57307

Process Rate Unit: Autos Burned

AB County Process

Rate

TOG Emis.

(Tons / Year)

CO Emis.

(Tons / Year)

NOX Emis.

(Tons / Year)

SOX Emis.

(Tons / Year)

PM Emis.

(Tons / Year)

GBV ALPINE 0 0.00 0.00 0.00 0.00 0.00

INYO 7 0.03 0.07 0.00 0.00 0.06

MONO 1 0.00 0.01 0.00 0.00 0.01

LC LAKE 38 0.14 0.40 0.01 0.00 0.32

LT EL DORADO 8 0.03 0.09 0.00 0.00 0.07

PLACER 3 0.01 0.03 0.00 0.00 0.03

MC AMADOR 20 0.07 0.21 0.01 0.00 0.17

CALAVERAS 37 0.13 0.39 0.01 0.00 0.31

EL DORADO 30 0.11 0.32 0.01 0.00 0.26

MARIPOSA 24 0.09 0.26 0.01 0.00 0.20

NEVADA 36 0.13 0.38 0.01 0.00 0.31

PLACER 13 0.05 0.14 0.00 0.00 0.11

PLUMAS 1 0.00 0.01 0.00 0.00 0.01

SIERRA 0 0.00 0.00 0.00 0.00 0.00

TUOLUMNE 87 0.31 0.92 0.03 0.00 0.74

MOJ KERN 83 0.30 0.88 0.03 0.00 0.71

LOS ANGELES 259 0.93 2.75 0.09 0.00 2.20

RIVERSIDE 22 0.08 0.23 0.01 0.00 0.19

SAN BERNARDINO 405 1.46 4.30 0.14 0.00 3.44

NC DEL NORTE 8 0.03 0.09 0.00 0.00 0.07

HUMBOLDT 38 0.14 0.40 0.01 0.00 0.32

MENDOCINO 44 0.16 0.47 0.02 0.00 0.37

SONOMA 13 0.05 0.14 0.00 0.00 0.11

TRINITY 3 0.01 0.03 0.00 0.00 0.03

NCC MONTEREY 181 0.65 1.92 0.06 0.00 1.54

SAN BENITO 28 0.10 0.30 0.01 0.00 0.24

SANTA CRUZ 132 0.48 1.40 0.05 0.00 1.12

NEP LASSEN 6 0.02 0.06 0.00 0.00 0.05

MODOC 1 0.00 0.01 0.00 0.00 0.01

SISKIYOU 17 0.06 0.18 0.01 0.00 0.14

SC LOS ANGELES 7826 28.21 83.15 2.74 0.00 66.52

ORANGE 1645 5.93 17.48 0.58 0.00 13.98

RIVERSIDE 963 3.47 10.23 0.34 0.00 8.19

SAN BERNARDINO 1335 4.81 14.18 0.47 0.00 11.35

SCC SAN LUIS OBISPO 142 0.51 1.51 0.05 0.00 1.21

SANTA BARBARA 104 0.37 1.11 0.04 0.00 0.88

VENTURA 5 0.02 0.05 0.00 0.00 0.04

SD SAN DIEGO 2189 7.89 23.26 0.77 0.00 18.61

SF ALAMEDA 292 1.05 3.10 0.10 0.00 2.48

CONTRA COSTA 872 3.14 9.27 0.31 0.00 7.41

MARIN 112 0.40 1.19 0.04 0.00 0.95

NAPA 153 0.55 1.63 0.05 0.00 1.30

SAN FRANCISCO 196 0.71 2.08 0.07 0.00 1.67

SAN MATEO 245 0.88 2.60 0.09 0.00 2.08

SANTA CLARA 837 3.02 8.89 0.29 0.00 7.11

SOLANO 6 0.02 0.06 0.00 0.00 0.05

SONOMA 93 0.34 0.99 0.03 0.00 0.79

SJV FRESNO 1485 5.35 15.78 0.52 0.00 12.62

KERN 359 1.29 3.81 0.13 0.00 3.05

KINGS 157 0.57 1.67 0.05 0.00 1.33

MADERA 210 0.76 2.23 0.07 0.00 1.79

MERCED 281 1.01 2.99 0.10 0.00 2.39

SAN JOAQUIN 117 0.42 1.24 0.04 0.00 0.99

STANISLAUS 388 1.40 4.12 0.14 0.00 3.30

TULARE 690 2.49 7.33 0.24 0.00 5.87

SS IMPERIAL 63 0.23 0.67 0.02 0.00 0.54

RIVERSIDE 238 0.86 2.53 0.08 0.00 2.02

SV BUTTE 256 0.92 2.72 0.09 0.00 2.18

COLUSA 1 0.00 0.01 0.00 0.00 0.01

GLENN 7 0.03 0.07 0.00 0.00 0.06

PLACER 66 0.24 0.70 0.02 0.00 0.56

SACRAMENTO 1148 4.14 12.20 0.40 0.00 9.76

SHASTA 226 0.81 2.40 0.08 0.00 1.92

SOLANO 3 0.01 0.03 0.00 0.00 0.03

SUTTER 32 0.12 0.34 0.01 0.00 0.27

TEHAMA 106 0.38 1.13 0.04 0.00 0.90

YOLO 129 0.47 1.37 0.05 0.00 1.10

YUBA 24 0.09 0.26 0.01 0.00 0.20

TOTAL 

 

24546 88.48 260.77 8.58 0.00 208.65

Fraction of Reactive Organic Gases (FROG): 0.7500 (Reactive Organic Gases (ROG) Emissions = TOG X FROG)

Fraction of PM10 (FRPM10): 0.9970 (PM10 Emissions = PM X FRPM10)