United States 

Department of 

Agriculture Reporting of

Forest Service

Forest

Products

Fire Incidents in

Laboratory

Paper

Research Heavy Timber FPL 464 Structures

Robert H. White 
Abstract

This investigation of fire incidents in 

heavy timber construction is based 

solely on the 1977-1981 data files of 

the National Fire Incidents Reporting 

System (NFIRS) of the Federal 

Emergency Management Agency. 

Buildings of heavy timber construction 

usually consist of interior columns, 

beams, and floors of wood and 

exterior walls of noncombustible 

construction. About half of the 

reported incidents involved one of two 

types of fixed property use which 

present different types of fire 

problems: either one- and two-family 

dwellings or agricultural products 

storage structures (barns and 

stables). Both types of structure are 

likely not to meet the-building code 

definition of heavy timber or type IV 

construction, although they have 

heavy timber members. 

Our main conclusions are (a) there 

is a need to clarify and improve the 

coding both for type of construction 

and for extent of fire damage; (b) 

solid fuel heating systems are the 

major cause of fires in the residential 

“heavy timber” structures; (c) fires of 

incendiary or suspicious origin are a 

significant portion of the agricultural 

product storage fires. 

Keywords: Fire, heavy timber, 

dwellings, barns, stables. 

December 1985 

White, Robert H. Reporting of fire incidents in 

heavy timber structures. Res. Pap. FPL 464. 

Madison, WI: U.S. Department of Agriculture, 

Forest Service, Forest Products Laboratory; 

1985. 9 p. 

A limited number of free copies of this 

publication are available to the public from the 

Forest Products Laboratory, One Gifford Pinchot 

Drive, Madison, WI 53705-2398. Laboratory 

publications are sent to over 1,000 libraries in 

the United States and elsewhere. 

The Laboratory is maintained in cooperation with 

the University of Wisconsin. 
Reporting of 

Fire Incidents in 

Heavy Timber 

Structures

Robert H. White, Research Forest Products Technologist, 

Forest Products Laboratory, Madison, WI 

Introduction Methodology

Heavy timber construction is widely National Fire Incidents 

recognized as having a high level of Reporting System firesafety, based on its performance

in actual fires. The objective of the The investigation was based solely present study was to gain insight into on data obtained from the files of

the firesafety performance of NFIRS. The NFIRS is the collection of

buildings of heavy timber fire incidents, fire casualty data, and construction, as recorded in-the files other fire department responses of the National Fire Incidents established by the Federal Emergency Reporting System (NFIRS), and the Management Agency (FEMA) (Kraft frequency of fires in such buildings. and Collins 1960). The coded fire These buildings usually consist of incident and casualty reports are interior columns, beams, and floors of voluntarily filled out by local fire wood and exterior walls of departments and compiled at the noncombustible construction. As will state and federal levels.

appear in this report, attainment of For each fire, the incident reports our objective was not possible. consist of 59 items, including data on 

the building characteristics; the 

location, ignition and spread of the 

fire; the extent of flame, smoke, and 

water damage; the amount of dollar 

loss; and the number of casualties. 

Included in the building characteristics 

is the type of construction (fire 

resistive, heavy timber, etc.). For this 

study, we selected those incidents 

that involved structures classified as 

heavy timber construction. These we 

have analyzed as they relate to the 

NFIRS codings for selected items 

including fixed property use, type of 

structure, and extent of damage. 

The coding for the different items 

is found in the NFIRS Handbook 

(National Fire Data-Center 1978b) and 

is generally consistent with the 1976 

edition of the National Fire Protection 

Association (NFPA) No. 901, Uniform 

Coding for Fire Protection (NFPA 

1976).

We studied data files for the 

5 years 1977 to 1981. During this 

period, incidents were reported from 

fire departments in 9, 16, 23, 32, and 

33 states, respectively, and in 1981 

also from the District of Columbia. 

Incidents include structure fires, 

vehicle fires, and outdoor fires. The 

total number of incidents ranged from 

430,000 in 1977 to 680,000 in 1981. 

For each of the years, about 200,000 

of the incidents were from California. 

California uses a different coding for 

type of construction which does not 

permit the selection of heavy timber 

structures. As a result, California data 

were excluded from this study. 

The NFIRS data have previously 

been used to examine the fire 

experience of building material 

distributors and dealers (Penoyar 

1980) and the solid wood products 

industry (Penoyar 1981). The data 

have also been used to study mobile 

home, wood roof, and garden 

apartment fires (Glowinski 1980). 

Annual reports based on the data 

have been published (Federal 

Emergency Management Agency 1982 

and later, National Fire Data Center 

1978a). The NFIRS data and software 

are available from the National 

Technical Information Service (NTIS) 

Computer Products Division. 
Data Selection 

We selected records from the 

master files referring to one type of 

situation (structure fires (11)1 ) and one 

type of construction (heavy timber (2)). 

Structure fires include any fires inside 

a building or structure, whether or not 

the fire causes structural damage to 

the building or is out on arrival of 

firefighters. Heavy timber is described 

as a typical mill-constructed building 

in which the load-bearing walls or 

columns are masonry or heavy 

timber, and all exposed wood 

members have a minimum dimension 

of 2 inches (National Fire Data Center 

1978b). The three model codes 

include heavy timber in the following 

categories: Basic Building Code type 

3A, Standard Building Code type III, 

and Uniform Building Code type III

(HT). Construction types not selected 

are: fire resistive (1) protected 

noncombustible or limited combustible 

(3) unprotected noncombustible or 

limited combustible (4) protected 

ordinary (5), unprotected ordinary (6) 

protected wood frame (7), unprotected 

wood frame (8) not classified above 

(9) and undetermined or not reported 

(0). These categories are based on 

the editions of the model codes 

current in 1976. Different names and 

categories are used in the current 

editions of the codes and the 1981 

edition of NFPA 901. 

An exposure fire occurs as a result 

of another fire. When exposure fires 

occur, separate incident reports are 

made out for each exposure. In the 

analysis of the data, we treated each 

exposure as a separate occurrence. 

Thus, exposure fires may possibly 

have resulted in our inclusion of 

multiple records for the same incident. 

For selected items, including fixed 

property use, structure type, and 

extent of damage, we calculated the 

number of occurrences, total number 

of injuries, total number of deaths, 

and total dollar loss for each of the 

5 years (table 1). 

1

Number in parenthesis is the numerical code for 

the item (e.g., the type of situation found or type 

of construction) given in the NFIRS incident 

report.

2

Dollar loss is recorded in two ways: 

as an estimated dollar loss and/or by 

property damage classification. There 

are 10 classes of property damage: 

$1 to $99 (1) $100 to $999 (2), $1,000 

to $9,999 (3), $10,000 to $24,999 (4) 

$25,000 to $49,999 (5) $50,000 to 

$249,999 (6). $250,000 to $999,999 

(7) $1 million or more (8) no dollar 

loss (9) and undetermined or not 

reported (0). Our summary of dollar 

loss was based on the estimated 

dollar loss. When no estimated dollar 

loss was given, an average value 

based on the property damage 

classification was used instead, 

except for class (8) ($1 M or more) for 

which $1 million was used. 

In the statistical analysis of the 

data, we considered the data for each 

year as an independent data set. We 

calculated the rate of occurrence for 

each division of the item, coded 0 

through 9, omitting class (0) 

(“undetermined or not reported”) from 

the denominator (table 2). This 

assumes that incidents in class (0) 

were distributed proportionately over 

the other classes. The omission was 

made to minimize the effect of 

variations in class (0) on the 

percentages reported for the different 

years. We calculated the means and 

standard error of the means and 

evaluated the significance of 

differences in the means. The 

percentage of all incidents that were 

“undetermined or not reported” was 

also calculated. 

Table 1.—Overall summary of all fire incidents 

Yearly total Total Number per 1,000 incidents

1977 1978 1979 1980 1981 Mean1

 Standard 1 error

Incidents

Exposures

Fire service injuries 

10

87

34

86

27

76

50

122

76

143

197

514

24.9

73.3

4.3

7.6

Other injuries 28 3 4 38 51 50 201 28.3 1.3

Fire service deaths 3 0 1 0 1 5 1.0 0.7

Other deaths 4 8 3 18 6 39 5.3 1.4

Dollar loss 

(records) 2

851 1,248 1,331 1,804 2,031 7,265 — —

($1,000,000's) 13.00 16.77 26.41 37.28 39.71 133.17 17.75 1.43 1

Mean and standard error of the five yearly data sets. 

2

Excludes all of Michigan data since type of situation found was coded "Fire explosion; insufficient 

information available to classify further" (10). 

Table 2.—Major divisions of fixed property use 

Total Percentage of 

incidents1

Rank

incidents Mean Standard

error

1 Residential property (4)2 2,794 38.9 0.8

2 storage property (8) 2,078 30.5 2.4

3 Manufacturing property (7) 710 9.4 1.2

4 Special property (9) 418 5.5 0.6

5 Store, office property (5) 367 5.1 0.4

6 Public assembly property (1) 319 4.3 0.4

7 Basic industry, utility, 

defense property (6) 254 3.7 0.6

8 Educational property (2) 90 1.2 0.2

9 lnstitutional property (3) 89 1.4 0.4

Undetermined or not reported (0) 146 1.9 0.5

Fixed Property Use number of 

1

Values for ranked items are percentages of all incidents for which fixed property use was determined: 

and for class (0), unranked, are Percentages of all incidents. Mean and standard error values are 

based on the data for each of the 5 years. 

2

Numbers in parentheses are NFIRS codings for categories of fixed property use. 
Results and Discussion 

A total of 7,265 of the selected 

records, coded as heavy timber (type 

of construction 2), were obtained from 

the NFIRS 1977 to 1981 data files. 

Table 1 gives an overall summary of 

the data. The number of incidents 

increased with the years, as more 

states participated in NFIRS. Of these 

7,265 records, 3 percent were for 

exposure fires. 

Of the 715 injuries, 72 percent were 

suffered by firefighters. In contrast, 

89 percent of the 44 fatalities were 

civilians or other emergency 

personnel. On the average, there 

were 102 injuries and 6 deaths per 

1,000 incidents. 

The total dollar loss reported for 

the 5-year period was $133 million. 

On the average, each fire resulted in 

an $18,000 loss; 27 percent of the 

fires involved dollar losses less than 

$1,000, and about 1 percent resulted 

in dollar losses in excess of $250,000. 

The reported dollar loss is the total 

loss of contents and structure in 

terms of the cost of replacement in 

like kind and quality. The loss does 

not include indirect monetary costs 

such as medical costs and lost time at 

work nor the many nonmonetary 

costs of a fire. Indirect costs of 

medical care and temporary shelter 

can be substantial in residential fires 

Residential property and storage 

property account for 68 percent of 

injuries, about the same proportion as 

for incidents. Fires in residential 

property accounted for 65 percent 

and those on storage property for 

only 6 percent of the fatalities. In 

contrast, storage property accounted 

for 41 percent and residential 

property for about 18 percent of the 

total dollar loss. 

The nine major divisions for fixed 

property use are subdivided into 

divisions. These divisions are then 

subdivided (table 3). Over 50 percent 

of the incidents were either one- and 

two-family dwellings (41) or 

agricultural products storage (81). 

Eighty-eight percent of the agricultural 

products storage (81) were barns and 

stables (815). No other division had 

more than 5 percent of the incidents. 

Fires in agricultural products storage 

and one- and two-family dwellings are 

discussed in more detail in the 

appendix.

Type of Structure 

The NFIRS classification by 

structure type is coded from (1) to (9). 

In 97 percent of the incidents, the 

structure type was a building (1 or 2). 

In 12 percent of the buildings, there 

were two or more fixed property uses 

(2). The heavy timber structure was 

an open structure (3) in 2 percent of 

the incidents. Open structures include 

roofs with no walls, bridges, and 

trestles. The remaining 1 percent of 

the incidents include air-supported 

structures (4), tents (5), open 

platforms (6), and underground 

structures (7). 

The construction method for the 

structure in 97 percent of the 

incidents was site built (1). In 

2 percent of the incidents, it was a 

factory-built, site-assembled structure 

(2). The remaining 1 percent include 

factory-built modular structures (3), 

factory-built mobile structures (4), and 

those not classified above (9). 

Table 3.—Divisions of fixed property use reported most frequently 

Percentage of Number incidents1

Rank Fixed Property use of

incidents Mean Standard

error

(Munson and Ohls 1979). Our figures 

are based only on reported incidents. 

The per incident value is generally 

lower when estimates for unreported 

incidents are included. 

Fixed Property Use 

There are nine categories, called 

major divisions, of fixed property use 

(table 2). Percentages reported in 

tables 2 and 3 do not include 

incidents in which the fixed property 

use was undetermined or not 

reported. Percentages are the 

average of the percentages for each 

of the 5 years. We found two major 

divisions, together, accounted for 

69 percent of the reported incidents: 

residential property (4) and storage 

property (8). Manufacturing property 

(7) accounted for 9 percent of 

incidents, store or office property (5), 

and special property (9) for about 

5 percent each. Special properties are 

mainly outdoor properties such as 

construction, bridges, outbuildings, 

and railroad properties. 

1 One- and two-family dwelling 2,361 33.1 1.1

(41)2

2 Agricultural products storage 1,499 22.5 2.7

(81)

3 Apartments, tenements, flats 308 4.0 0.8

(42)

4 Construction, unoccupied 257 3.3 0.5

property (91) 

5 Wood, furniture, paper printing, 245 3.1 0.7

manufacturing (75) 

6 Vehicle storage (88) 240 3.3 0.2

7 Agriculture (65) 213 3.1 0.6

8 Metal, metal products 164 2.3 0.3

manufacturing (77) 

9 Eating, drinking places (16) 129 1.8 0.1

10 General item storage (89) 118 1.7 0.2

11 Special structures (92) 110 1.5 0.2

12 Care of the sick, injured (33) 32 0.6 0.3

Unclassified (00) 137 1.8 0.4

1

Values for ranked items are percentages of all incidents for which fixed property use was determined;

and for class (00), unranked, are percentages of all incidents. Mean and standard error values are

based on the data for each of the 5 years.

2

Numbers in parentheses are NFIRS codings for subcategories of fixed property use.

3
Classification of Heavy 

Timber Construction 

The large number of “heavy 

timber” fires in agricultural products 

storage and one- and two-family 

dwellings raises a question as to what 

are being classified as heavy timber 

structures. As mentioned above, the 

NFIRS Handbook (National Fire Data 

Center 1978b) describes heavy timber 

as “a typical mill-constructed-building 

in which the load-bearing walls or 

columns are masonry or heavy timber. 

and all exposed wood members have 

a minimum dimension of 2 inches.” 

Using this definition, many people 

classify such structures as log cabins 

and pole frame buildings as heavy 

timber. Most of the agricultural 

products storage buildings were barns 

and stables. Poles in farm service 

building construction amounted to 

approximately 72 million linear feet in 

1975 (Reid and Baumgartner. 1977). 

Based on a 1968 to 1970 survey, 

about one-third of all farm service 

buildings were of pole construction 

(Reid and Baumgartner 1977). Pole 

structures are also used for 

multifamily and single-family 

residences. It is estimated that 30,000 

to 40,000 log homes were built in 

1983 (Anonymous 1984). 

The definition of heavy timber 

construction in NFPA 220 (NFPA 

1979) is somewhat narrower. Type IV 

construction (formerly heavy timber) is 

defined as: 

. . . that type in which exterior and 

interior walls and structural members 

which are portions of such walls are 

of approved noncombustible or 

limited-combustible materials. Other

interior structural members including 

columns, beams, arches, floors, and 

roofs are of solid or laminated wood 

without concealed spaces and comply 

the provisions of 3-4.2 through 3-4.6. 

In addition, structural members have 

fire resistance ratings not less than 

those set forth in table 3. . . . 

Table 3 of NFPA 220 lists 1 and 2 

hours’ fire resistance requirements for 

the interior and exterior bearing walls. 

Provisions 3-4.2 through 3-4.6 give 

the minimum dimensions required for 

the structural wood members. Log 

homes and pole frame construction 

would not satisfy this definition of 

4

heavy timber construction. We 

consider it highly unlikely that there 

are sufficient agricultural products 

storage and one- and two-family 

dwelling structures meeting the 

NFPA 220 definition to result in the 

large proportion of fires recorded for 

these two fixed property uses. 

The data for the different states 

suggest that different definitions for 

heavy timber construction are being 

used in the various States 

participating in the NFIRS (table 4). 

For example, both Minnesota and 

Oregon reported about 

80,000 incidents in the 5-year period. 

In Minnesota, 0.49 percent of the 

incidents were classified as heavy 

timber structure fires. Of these 

397 heavy timber structure fires, 

38 percent were either one- and twofamily dwellings or agricultural 

products storage. In Oregon, 

0.14 percent of the incidents were 

heavy timber structure fires. None of 

the Oregon fires were one- and twofamily dwellings or agricultural 

products storage facilities. 

Demographic differences between 

Minnesota and Oregon are unlikely to 

account for the differences in reported 

heavy timber structure fires. Other 

States with 11 percent or less of 

heavy timber fires in one- and twofamily dwellings or agricultural 

products storage include Colorado, 

Hawaii, Massachusetts, Washington, 

and Wisconsin. States in which heavy 

timber structure fires in one- and twofamily dwellings or agricultural 

products exceeded 58 percent 

included Maryland, Michigan,

Montana, Ohio, North Carolina, 

Texas, and Tennessee. Clarification of 

the criteria for classifying a structure 

as heavy timber is needed to improve 

uniformity in future fire records. One 

possibility is to add subdivisions to 

construction-type coding. For heavy 

timber, the sub- divisions needed 

include type IV construction, pole 

structures, log cabins, and other 

structures with large wood members. 

Other Considerations 

Annual Variations 

The mean results presented in this 

paper assume that the data for each 

year represented the same 

population. Because States were 

added in the-later years and other 

things changed over time, this 

assumption is not completely 

accurate. In 1977, Ohio accounted for 

64 percent of the heavy timber 

incidents. By 1981, the contribution 

from Ohio had dropped to 20 percent, 

and the States of Michigan, Illinois, 

Minnesota, New York, Ohio, and 

Washington together accounted for 

63 percent of the incidents. Small 

standard errors in the means indicate 

that either the changes did not affect 

the results or that the changes tended 

to balance out. Large standard errors 

may represent true large random 

variations, trends in the results, or 

simply differences in the data base for 

the 5 years. Generally, the standard 

errors were large relative to the mean 

only when the number of incidents 

was small. 

Extent of Damage 

The classification of the extent of 

flame damage consists of 10 items: 

(1) confined to the object of origin, (2) 

confined to part of room or area of 

origin, (3) confined to the room of 

origin, (4) confined to fire-rated 

compartment of origin, (5) confined to 

floor of origin, (6) confined to 

structure of origin, (7) extended 

beyond structure of origin, (8) not a 

structure fire, (9) no damage of this 

type, and (10) undetermined or not 

reported. In 58 percent of the 

incidents involving one- and twofamily dwellings, the flame damage 

was confined to the room of origin 

(1,2,3), in 21 percent it was confined 

to structure of origin (6), in 13 percent 

to floor of origin (5), and in 3 percent 

to fire-rated compartment of origin (4). 
Table 4.—Numbers of heavy timber incidents by state 

Number of heavy timber incidents Dwelling or 

State1 Years Per 10,000 One- and Agricultural agriculturaI total

reported dwelling Storage storage2

Pct

AK 1977-81 8 2 57 41 2 52

AZ 1980 10 24 2 0 20

CO 1981 1 0 11 0 0 0

CT 1979-81 138 24 20 6 19

DC 1981 1 5 28 6 0 40

D E 1978-81 5 2 30 5 17 42

G A

1980-81

1979-80

100

13

23

17

39

5

10

0

4 9

38

reporting Total incidents two-family- Products products

HI

IA

IL

1981

1979-81

1978-81

13

175

217

18

39

30

1

31

36

0

53

45

8

48

37 KS 1980-81 56 22 16 5 38

LA

M A

MD

ME

Ml3

1981

1979-80

1977-81

1980-81

1978-81

26

20

293

76

1,028

38

32

83

46

35

7

1

138

2 6

429

2

0

46

6

210

35

5

63

42

62

MN

MO

MT

NC

1977-81

1977-80

1978-81

1979-80

397

220

9 9

77

49

30

60

109

102

143

38

37

51

18

8

8

38

73

46

58

NE 1980-81 1 5 0 0 0

NH 1980-81 1 5 66 1 2 20

NY 1977-81 839 47 205 212 50

OH 1977-81 2,385 72 805 757 65

OR

RI

1977-81

1978-81

113

107

14

24

0

23

0

2

0

23

S D 1978, 34 39 4 4 24

1980-81

TN

T X

1979-81

1981

75

98

80

102

36

61

8

3

59

65 UT 1978-81 73 32 29 6 48

VA 1980-81 26 33 6 3 35

W A 1980-81 197 71 16 6 1 1 W I 1978-81 49 28 3 2 10 W V 1979-80 107 8 6 36 6 3 9 W Y 1979-81 29 6 5 13 1 48

All 1977-81 7,265 45 2,361 1,499 53

1

Including the District of Columbia (DC). States reporting no heavy timber incidents included AR, ID, 

and CA. California uses a different coding that does not permit the selection of heavy timber incidents. 

2

Percentages of heavy timber incidents for either one- and two-family dwellings or agricultural products 

storage. Percentages are based on the sums rather than the yearly data. 

3

Excludes 1977 data for Michigan because type of situation found was coded “fire explosion. 

insufficient information available to classify further” (10) for all incidents. 

Damage extending beyond the area 

of origin in a one-room building is 

recorded as confined to the structure 

of origin. Also, a fire on the roof or 

outside wall of a building is recorded 

as confined to structure of origin 

(National Fire Data Center 1978b). In 

many one- and two-family dwellings, 

there is only one floor and no firerated compartment of origin. Fires in 

these structures are all listed as 

confined to structure of origin once 

the fire extends beyond the room of 

origin. Thus, the high percentage for 

confined to structure of origin (6) does 

not necessarily reflect fires extending 

beyond the floor of origin or even the 

room of origin. Also, the no damage 

of this type (9) for smoke, water, and 

fire control damage is used when the 

structure is burned to the ground. 

Population at Risk 

An evaluation of the safety of heavy 

timber structures or safety of different 

occupancies could not be made using 

the data in this study because there is 

no measure of the population at risk. 

The frequent occurrence of residential 

and agricultural products storage fires 

is quite likely to result from the 

relatively large number of these 

occupancies rather than from any 

inherent fire hazard. In addition, lack 

of information on the number of 

properties at risk makes it difficult to 

use the extent-of-damage data. As 

mentioned previously, a fire in a oneroom building will be recorded as 

confined to the structure of origin 

once the fire extends beyond the area 

of origin. In contrast, a multiroom, 

multifloor structure requires the fire 

penetration of walls and floors before 

a fire in it is recorded as confined to 

the structure of origin. 

Furthermore, it is difficult to 

measure the population at risk when 

the exact types of structure being 

classified as heavy timber are not 

known. As a result of these 

unknowns, it wag not possible to 

achieve the objective of this study. 

Because a large, portion of the data 

was one- and two-family dwellings 

and agricultural products storage 

incidents, some of the findings on 

these incidents are reported in the 

appendix.

5
Conclusions Literature Cited 

Based on the data reported in this 

paper, we reach several conclusions 

regarding the reporting of heavy 

timber fires in the National Fire 

Incident Reporting System. We 

concluded that: 

1. The coding for type of 

construction needs to be clarified and 

improved. In particular, the 

requirements for a structure to be 

coded heavy timber should be more 

clearly specified or modified to 

differentiate between Type IV 

buildings and other structures with 

large wood members. 

2. The coding for the extent of 

damage needs to be improved so the 

frequency of wall and/or floor 

penetration can be obtained from the 

data.

3. Guidelines for users of the data 

should be developed so users have 

an understanding of the limitations 

and peculiarities of the data. 

4. Most NFlRS fires reported as 

involving heavy timber structures 

occur in one- and two-family dwellings 

and agricultural products storage 

structures (barns and stables). These 

structures probably do not meet the 

building code, or NFPA 220, definition 

of heavy timber (Type IV 

construction).

6
Appendix

As discussed in the report, the 

heavy timber incidents reported as 

one- and two-family dwellings and 

agricultural products storage fires 

probably do not involve Type IV heavy 

timber structures. They probably 

represent fires in other types of 

structures with heavy timber 

members, such as pole structures, 

post and beam structures, and log 

cabins. Since the data provide some 

information on fires in one- and twofamily dwellings and agricultural 

products storage buildings, a 

summary of the findings are given in 

this appendix of the report. 

One- and Two-Family 

Dwellings

In the 5-year period, there were 

2,361 incidents reported involving 

one- and two-family dwellings 

(table Al). Of these, 2 percent were 

exposure fires. The injuries were 

about half civilian and half fire service. 

There were an average 42 civilian 

injuries per 1,000 incidents. For all 

reported NFIRS dwelling fires (FEMA 

n.d. a, n.d. b), there were 38 injuries 

per 1,000 incidents. Only one of the 

27 deaths in incidents coded as 

“heavy timber” was a fire service 

death. On average, there were 

11 civilian deaths per 1,000 incidents 

coded as “heavy timber.” For all 

reported NFIRS dwelling fires (FEMA 

n.d. a, n.d. b), there were 8 civilian 

deaths per 1,000 incidents. On the 

average, the dollar loss reported was 

$8,800 per incident coded as “heavy 

timber.” For all reported NFIRS 

dwelling fires (FEMA n.d. a, n.d. b), 

the average dollar loss was $4,960 

per incident. These values for injury, 

death, and dollar loss are for reported 

fires. Generally, lower numbers per 

incident are reported when estimates 

for the unreported fires are included 

in the calculations. 

Heating was the major cause of fire 

in the one- and two-family dwellings 

(table A2). In addition, heating caused 

most dollar loss, most injuries, and 

most fatalities. Our determination of 

the cause of the fire is based on the 

NFIRS coding for equipment involved 

in ignition, form of heat of ignition, 

type of material ignited, ignition factor, 

and exposure number (Kraft and 

Collins 1980). 

In a common scenario of fire 

involving a heating system, the cause 

was a mechanical failure or 

malfunction, or a deficiency of design, 

construction, or installation, as a 

result of which the heat from the fuelfired, fuel-powered object ignited the 

wood structural component or finish. 

Apart from heating-system fires, a 

common scenario was mechanical 

failure or malfunction resulting in heat 

from electrical equipment arcing or 

overloaded electrical equipment

igniting wood structural component or 

finish. Incendiary or suspicious fires, 

electrical distribution fires, and 

cooking fires were the other leading 

types of fire. Based on these data, 

smoking was only the fifth leading 

cause of fire in the one- and twofamily dwellings. 

Residential fires are the number 

one fire problem in the United States. 

In 1978, residential fires were 

responsible for about 88 percent of all 

structure fires and 88 percent of the 

civilian deaths in structure fires 

(FEMA 1982). Based on the data for 

all residential fires, smoking is the 

leading cause of civilian fire deaths 

and heating is second (National Fire 

Data Center 1978a). As with one- and 

two-family dwellings coded as “heavy 

timber,” heating is the dominant 

cause of fires in all residential fires. 

Fire caused by heating equipment 

was also the main cause of injuries 

and fatalities in the one- and twofamily dwelling fires coded as “heavy 

timber.” Given that these “heavy 

timber” structures are probably log 

cabins, pole structures, and other 

similar types of building, there is 

probably a greater proportion of 

alternative or auxiliary heating devices 

in these structures than in wood 

frame one- and two-family dwellings. 

Although the point was not 

investigated, it is at least possible that 

the one- and two-family dwellings 

coded as “heavy timber” occur 

predominantly in rural areas. Evidence 

indicates a higher fire death rate in 

rural areas than in nonrural areas. 

Klem (1984) considers that the higher 

death rate from heating equipment 

than from other fires largely explains 

the higher rural death rate from fire. 

The rural heating fire fatalities are 

associated predominantly with solidfueled heating equipment (Gomberg 

and Clark 1982). The death rates due 

to smoking or open flame are only 

slightly higher in rural than nonrural 

areas.

In 51 percent of the incidents, the 

method of extinguishment was with 

preconnected hose line(s) with water 

carried in apparatus tanks (5), as 

would be required in rural areas. In 

only 16 percent of the incidents, the 

water for the preconnected hose 

line(s) was from hydrant, draft, or 

standpipe (6). The possibly greaterthan-average proportion of rural 

incidents offers one explanation for 

the higher death and injury rates, and 

average dollar loss, for the incidents 

coded as “heavy timber” compared 

with the average for all dwelling 

incidents.

Because the incidents coded as 

“heavy timber” come predominantly 

from certain States, we must consider 

differences in the geographical 

distribution of the incidents among the 

reporting States. We do not know 

whether the States reporting incidents 

coded as “heavy timber” are 

representative of States that reported 

dwelling fires. Any differences in the 

distribution of the reported causes of 

fire affect the averages because rates 

of death, injury, and dollar loss are 

correlated with the cause of fire. 

In a study of a limited sample of 

fires involving alternative- or auxiliaryheating equipment, the fires most 

commonly involved solid- fuel heaters 

(Jones and Heck 1983). These 

heaters included fireplaces, fireplace 

inserts, wood-burning and coalburning stoves. In most of these fires, 

improper inspection and/or lack of 

cleaning of the stove pipe and 

chimney led to an accumulation of 

creosote which ignited. Peacock 

(1979) reviewed reported fire incidents 

involving wood-burning appliances 

and concluded that the major risks 

associated with the equipment were 

attributable to improper installation of 

woodburning appliances and 

insufficient care in their use. Heating 

fires in one- and two-family dwellings 

are steadily increasing in number and 

are responsible for a percentage of 

the fires in these dwellings that has 

increased from 22 percent in 1977 to 

31 percent in 1981 (Jones 1982). 

7
fires.

Data on sprinklers and smoke

detectors were limited because of the

large number of fires in which no

Table A-1.—Overall summary for one- end two-family dwelling incidents 

Yearly totals Total incidents

Number per 1,000 

1977 1978 1979 1980 1981 number Mean Standard

error

Incidents

Exposures

Fire service injuries

Other injuries

Fire service deaths

Other deaths

Dollar loss

252 426 471 600 612 2,361

3 6 9 20 14 52

—

20.3 —

3.8

18 18 10 30 31 107 47.1 8.1

15 22 17 17 20 91 41.7 5.9

1 0 0 0 0 1 0.8 0.8

3 5 2 12 4 2 6 10.9 2.7

1,888,688 3,065,379 4,193,938 5807,738 6,560,911 21,516,656 8,799,000 661,000

Table A-2.—Causes of fires in one- and two-family dwellings 

Rank Cause

Number

o f

incidents

Percentage of 

incidents1

Mean Standard

error

Total

dollar

loss

Number

of

injuries

Number

of

fatalities

$1,000

1 Heating 773 44.8 1.9 4,960 53 8

2 Incendiary, suspicious 256 15.7 1.2 3,764 2 6 7

3 Electrical distribution 196 11.5 0.9 1,984 1 5 0

4 Cooking 181 10.9 1.1 633 17 3

5 Smoking

6 Children playing 

86

71

5.6 1.1

4.4 0.8

512

388

1 4

8

3

0

7 Natural 57 3.3 0.4 716 6 0

8 Exposure 52 2.8 0.5 462 0 0

9 Appliances, air conditioning 14 0.9 0.3 84 1 0

10 Other heat, flame, spark 2 0.09 0.06 20 0 0

11 Open flame, ember, torch 0 0 0 0 0 0

12 Other equipment 0 0 0 0 0 0

Unknown 673 28.5 1.3 $7,992 178 6

1

Values for ranked items are percentages of all incidents whose cause was determined and reported; and for those of unknown cause are percentages of all 

incidents. Mean and standard error values are based on the data for each of the 5 years. 

Solid-fuel heating equipment was the sprinkler equipment limits the extent Agricultural Products 

Storage

There were 1,499 incidents of fire in 

agricultural products storage reported 

in the 5-year period (table A3). Of 

these, 4 percent were exposure fires. 

Of the 169 injuries, 67 percent were 

suffered by firefighters. Three of the 

four deaths were civilian. On the 

average, there was a $22,300 loss for 

each incident. 

Barns and stables (815) accounted 

for 88 percent of the-agricultural 

products storage structures. The 

remaining 12 percent consisted mainly 

of bulk storage of seeds, beans, nuts, 

and silage (811), and storage of 

materials for agricultural purchase 

(818).

main factor also in the 1977 to 1981 

increase in the number of heating 

fires. In the one- and two-family 

dwelling fires coded as “heavy 

timber” discussed here, the 

percentage of fires in which heating 

was the cause increased from 

38 percent in 1977 to about 

48 percent in 1979, 1980, and 1981. 

Active fire prevention education 

regarding wood-burning equipment 

operation and enforcement of code 

requirements for their installation will 

help to reduce the number of heating 

fires.

Data on sprinklers and smoke 

detectors were limited because of the 

large number of fires in which no 

detector or sprinkler equipment was 

present. The available data were 

consistent with the hypothesis that 

the presence of smoke detectors and 

of damage when there is a fire. An 

assessment of the impact of using 

detectors and sprinklers in residential 

occupancies (Budnick 1984) 

concluded that their use is of 

significant benefit in terms of life and 

safety. In a 1977 survey, 20 percent 

of households had smoke detectors 

(Hall 1982). In a 1982 survey, more 

than two-thirds of the nation’s 

households had smoke detectors 

(Jones 1982). With increased use of 

smoke detectors and the introduction 

of sprinkler technology to residential 

occupancies, the actual benefits of 

sprinklers and detectors should 

become more apparent in future fire 

incident data. However, increased use 

of detectors may be increasing the 

number of unreported incidents 

(FEMA n.d. b). 

8
The cause was deemed incendiary/ 

suspicious in 41 percent of the fires in 

agricultural products storage 

structures coded as “heavy timber” 

(table A4). Fires started by electrical 

distribution were responsible for the 

highest total dollar loss while those 

started by electrical distribution and 

natural causes resulted in most 

injuries. Commonly, ignition of 

structural wood component or finish 

occurred either in suspicious 

circumstances, or by misuse of heat 

of ignition, or by natural causes 

(lightning or spontaneous ignition). 

Heat resulting from mechanical failure 

of electrical distribution equipment 

caused the ignition of agricultural 

products in a number of fires. 

In 64 percent of the incidents for 

which method of extinguishment was 

reported, the fires were extinguished 

with water carried in apparatus tanks 

using preconnected hose line(s) (5) 

and in 12 percent of the incidents with 

water from hydrant, draft, or 

standpipe (6). 

For all nonresidential structures, 

more fires, deaths, injuries, and 

property loss were attributed to 

incendiary/suspicious than to any 

other cause (FEMA 1982). Storage 

fires represent only 2.5 percent of all 

structure fires (FEMA 1982). The 

major causes of storage fires are 

incendiary/suspicious (29 pct), open 

flame, heat (14 pct), and electrical 

distribution (10 pct). 

While the use of detectors and 

sprinklers has increased in one- and 

two-family dwellings, there has been 

no increase in the very small number 

of incidents involving detectors or 

sprinkler equipment in agricultural 

products storage structures. Based 

on 1978 data, the average reported 

loss per fire for all storage property 

with spinklers was one-half of the 

loss for storage property without 

sprinklers (FEMA 1982). 

The data suggest possible ways to 

reduce fire losses in agriculturalproducts storage structures (barns 

and stables). The potential benefit of 

sprinklers and/or detectors should be 

investigated. Greater emphasis should 

be given to inspecting equipment for 

mechanical and electrical failures in 

agricultural storage facilities, as in 

storage facilities in general (FEMA 

1982). Lightning protection also needs 

to be properly maintained in 

agricultural storage structures to 

reduce lightning-caused fires.

Thorough investigations of incendiary/ 

suspicious fires are necessary to 

reduce their number. 

Table A-3.—Overall summary for agricultural products storage incidents 

Yearly totals Number per 1,000 

Total incidents

1977 1978 1979 1980 1981 number

Mean Standard

error

Incidents

Exposures

Fire service injuries

Other injuries

Fire service deaths

Other deaths

Dollar loss

261 309 274 350 305 1,499 — —

5 10 9 8 23 5 5 36.5 10.1

27 21 1 6 28 22 114 76.4 7.6

4

1

0

2

0

0

2

0

7 1

0

1 6

1

3

10.5 3.1

0 0.8 0.8

0 3 0 1.7 1.7

4,065,974 5,567,714 4,898,462 9,294,313 10,214,964 34,041,428 22,304,000 3,365,000

Table A-4.—Causes of fires in agricultural products storage structures 

Percentage of Number incidents1 Total Number Number

Rank Cause of dollar of of

incidents Mean Standard loss injuries fatalities

error

$1,000 1 Incendiary, suspicious 339 40.6 1.4 4,578 1 3 0

2 Electrical distribution 156 18.7 0.5 7,364 1 9 0

3 Natural 153 18.2 2.3 4,693 1 9 1

4 Exposure 55 6.4 1.6 679 4 0

5 Heating 51 6.2 0.6 1,472 1 0

6 Children playing 46 5.7 1.0 544 2 0

7 Smoking 24 2.9 0.5 161 1

8 Other heat, flame, spark 0.9 0.3 1 9 0

0

7 0

9 Appliances, air conditioning 3 0.4 0.3 32 0

0

0

10 Cooking 0 0

0

0

0

0 0

11 Open flame, ember, torch 0 0 0

0

0

0 12 Other equipment 0 0 0 0

Unknown 665 44.4 1.0 14,498 71 3

1

Values for the different ranked items are percentages of all incidents whose cause was determined and reported; and for those of unknown cause are 

percentages of all incidents. Mean and standard error values are based on the data for each of the 5 years. 

3.5-12/85 9
The Forest Products Early research at the 

Laboratory (USDA Forest Laboratory helped establish 

Service) has served as the U.S. industries that produce 

national center for wood pulp and paper, lumber, 

utilization research since structural beams, plywood, 

1910. The Laboratory, on the particleboard and wood 

University of Wisconsin- furniture, and other wood 

Madison campus, has products. Studies now in 

achieved worldwide progress provide a basis for 

recognition for its more effective management 

contribution to the knowledge and use of our timber 

and better use of wood. resource by answering critical 

questions on its basic 

characteristics and on its 

conversion for use in a variety 

of consumer applications. 

Unanswered questions remain 

and new ones will arise 

because of changes in the 

timber resource and 

increased use of wood 

products. As we approach the 

21st Century, scientists at the 

Forest Products Laboratory 

will continue to meet the 

challenge posed by these 

questions.