U.S. Fire Administration/National Fire Data Center

Investigation of 

Confined Structure Fires

Topical Fire Research Series, Volume 5 – Issue 8

February 2006
T O P I C A L F I R E R E S E A R C H S E R I E S


Investigation of Confined Structure Fires 

February 2006 Volume 5, Issue 8 

Findings 

■ Confined structure fires account for 37% of all reported structure fires and 38% of 

residential structure fires. 

■ Per fire, confined fire losses are far lower than the average structure fires. Less than 

14% of confined structure fires reported losses. 

■ More than half (57%) of all confined structure fires are confined cooking fires. 

■ Inattentive behavior is the most common human factor that results in confined fires. 

Confi ned structure fi res are small fire incidents that are limited in scope, are confined to noncombustible 

containers, rarely result in serious injury or large content losses, and are expected to have no accompanying property 

losses due to fl ame damage.

1 This topical report is a summary of a detailed analysis of the characteristics of small 

fires that occur in structures that are contained or confi ned as recorded in the U.S. Fire Administration’s (USFA’s) 

National Fire Incident Reporting System (NFIRS).2 

CONFINED FIRES AND UNREPORTED FIRES 

Information on small confi ned structure fi res has been available in the past via the NFIRS data, but analysts 

have been aware of data collection issues that may have precluded full reporting of all these small fi re incidents. In 

response to these concerns, NFIRS 5.0 includes new incident types and abbreviated reporting that are specifi cally 

designed to identify these small fi res and facilitate data collection. 

Studies of the unreported fire problem indicate that unreported fires tend to be small, low-loss confi ned or 

contained fi res.This investigation into similar fi res—confi ned structure fi res—may shed light on the characteristics 

of unreported fires as well. Even the largest fire starts small; hence, all fi res, regardless of size, merit prevention 

attention and analytic investigation. 

The 2002 NFIRS 5.0 data contain abbreviated reporting for slightly over 52,000 confi ned structure fi re 

incidents—37% of structure fi res.These incidents accounted for $26 million in combined losses, 3 deaths, and 

nearly 500 injuries. Per fi re, these losses are far lower than the average structure fire in 2002 (Figure 1). 

FIGURE 1. 2002 LOSS MEASURES FOR CONFINED


STRUCTURE FIRES 

Loss Measure All Structure 

Fires 

Confined 

Structure Fires 

$ Loss/Fire $14,252 $498

Injuries/1,000 Fires 30.5 9.1

Fatalities/1,000 Fires 5.1 <0.1

Source: NFIRS 5.0 data only

U.S. Department of Homeland Security 

United States Fire Administration • National Fire Data Center 

Emmitsburg, Maryland 21727 

http://www.usfa.fema.gov/inside-usfa/nfdc/pubs/tfrs.shtm 

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DISTRIBUTION OF FIRES 

More than half of all confi ned fi res are confined cooking fires. Of the 52,006 confi ned fi res reported through 

NFIRS in 2002, 57% were cooking fires, 19% were trash or rubbish fi res, and 17% were chimney fi res.When 

heating-related confi ned fi res (chimney and fuel burners) are grouped together, these types of confi ned fi res 

become the second leading group of fi res at 23% (Figure 2). Most confi ned structure fi res (77.5%) occurred on 

residential properties. 

As a result of this distribution, the cause profiles for reported structure fires, especially residential structure fi res, 

have undergone an important change.

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 Confi ned structure fi res account for 38% of all reported residential structure 

fires in the NFIRS 5.0 data. Confi ned fi res account for over half (53%) of those residential fires where cause 

information is available. 

FIGURE 2. CONFINED STRUCTURE FIRES BY


INCIDENT TYPE (2002)


Incident Type Fires Percent 

113 Cooking 

114 Chimney Fires 

115 Incinerator 

116 Fuel Burner 

117 Commercial Compactor 

118 Trash/Rubbish 

29,706 

8,638 

284 

3,226 

246 

9,906 

57.1 

16.6 

0.5 

6.2 

0.5 

19.0

 Total 52,006 100.0 

Source: NFIRS 5.0 data only 

LOSS 

By defi nition, losses associated with confi ned fi res are limited to the contents of the container, and such losses 

are expected to be minimal. Likewise, a fi re confi ned to its container of origin is not expected to generate much, if 

any, property loss. 

The collected data, however, show exceptions to this defi nition. Of the 52,006 confi ned fi res in the 2002 data, 

13.6% reported losses.These losses averaged $3,657 with the average property loss ($2,058) exceeding the average 

content loss ($1,599). Property losses were reported in 4,711 confi ned fi re incidents, representing 9.1% of all 

confi ned fi res in the NFIRS data that year. Content losses were reported for 4,520 incidents, slightly less than 9% of 

confi ned fi res. Details are shown in Figure 3. 

FIGURE 3. DOLLAR LOSS SUMMARY, CONFINED STRUCTURE FIRES (2002) 

Loss Category Fires % Overall Loss % Loss/ 

Fire Contents Loss/ Fire Property Loss/ Fire 

Contents Only 2,368 4.6 $2,743,893 10.6 $1,159 $2,743,893 $1,159 — — 

Property Only 2,559 4.9 4,973,152 19.2 1,943 — — $4,973152 $1,943 

Contents and Property 2,152 4.1 18,169,987 70.2 8,443 8,572,802 3,984 9,597,185 4,460 

Any Content Loss 4,520 8.7 20,913,880 80.8 4,627 11,316,695 2,504 9,597,185 2,123 

Any Property Loss 4,711 9.1 23,143,139 89.4 4,913 8,572,802 1,820 14,570,337 3,093 

Any Loss 7,079 13.6 25,887,032 100.0 3,657 11,316,695 1,599 14,570,337 2,058 

No Losses 44,927 86.4 — 

Overall 52,006 $25,887,032 $498 $11,316,695 $218 $14,570,337 $280 

Source: NFIRS 5.0 data only 

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FIRES WITH CONTENT LOSS ONLY 

For those fi res that are more closely associated with the original intent of the confi ned fi re concept—those with 

only content losses and minor injuries—only 11.7% have content losses in excess of $1,000.When the group of 

fires with content loss includes all fi res with content losses (that is, those fi res above with only content losses and 

fires that have both content and property losses), the average total losses increase substantially. Not surprisingly, the 

fires with the greatest total loss also tend to have more fi re spread. 

INJURIES 

While confi ned fi res were designed to capture no-loss fires, as with contents loss, it is reasonable to expect 

some injury associated with these fi res. It is conceivable, for example in a confi ned cooking fire, that an individual 

sustained a burn either in the ignition of the fi re or in reaction to the fi re (e.g., placing a lid on the container). 

Confi ned fi res reported to NFIRS in 2002 resulted in 471 injuries, 82.2% of which occurred in residential 

properties. Confi ned cooking fires resulted in the largest number of injuries. 

FIRE SPREAD 

As expected, virtually all confi ned fi res are restricted to the object of origin (99.1%). Only 3.3% of confi ned 

fires with content or property loss move beyond their containers, and these obviously have the highest losses per 

fire, as noted above. 

HUMAN FACTORS 

Human intervention, neglect, or inappropriate behavior can all result in fi re incidents. Based on the NFIRS 

fire reports that included fi re module data, unattended heat use or unsupervised activities are the most common 

human factors (65.5%) that result in confi ned fi res, and 85.2% of these cases are from unattended cooking. Sleeping 

occupants (11.8%) and the age of residents (8.4%) are the next most important human factors contributing to 

confi ned structure fi res. 

MONTH OF YEAR 

As can be seen in Figure 4, it is the pattern of heating-related incidents (confi ned chimney and confi ned fuel 

burner fi res) that explain the overall pattern in monthly trends of confined structure fi res.The majority of confi ned 

fires occur between October and March with peaks in the winter (December–January). Confi ned structure cooking 

fires are relatively steady throughout the year with slightly fewer confi ned cooking fires occurring in the summer 

months. Although cooking is the predominant reason for a confi ned fi re, the overall trends are little affected by the 

number of these fi res each month. 

0

1000

2000

3000

4000

5000

6000

Jan Feb March April May June July Aug Sept Oct Nov Dec

Fires

FIGURE 4. MONTHLY INCIDENCE OF CONFINED STRUCTURE FIRES 

BY GENERAL TYPE OF INCIDENT (2002) 

5380

4856

5160

4037 4091

3769

3531

3261 3312

4385

4735

5489

Cooking Heating-Related Trash Special Equipment

Based on 52,006 incidents or cases reported to NFIRS.

Source: NFIRS 5.0 data only

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Trash and rubbish fi res are more numerous during the late spring and early summer months, perhaps a byproduct of increased outdoor activity in these months. In the 2002 data, there were more confined trash fi res 

(9,906) than chimney fi res (8,638). Confi ned incinerator and commercial compactor fi res (combined as “special 

equipment” in Figure 4) averaged 44 per month in the NFIRS data, with a slight increase in the summer months. 

Their influence on the overall monthly trends in confi ned fi res is extremely limited. 

TIME OF DAY 

Confi ned fi res typically occur during waking hours.The hourly distribution of these fi res are dominated by that 

of cooking fires and tend to peak with the lunch and dinner hours. 

SMOKE ALARMS 

Smoke alarms play a vital role in the early detection of confi ned structure fi res. In the more than half of confi ned 

fires (53%) where alarm alert information was provided, alarms alerted occupants 63% of the time.

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 Where more 

detailed information is provided in the fi re module, smoke alarms operated in 71% of the incidents. But some 

confi ned fi res were just too small to cause the alarm to operate, and in a very limited number of cases the alarm 

failed to operate altogether. 

CONCLUSION 

Confi ned structure fi res are predominately the result of cooking fires and, where additional information was 

given, inattentive behavior. 

To ensure the robustness of the data collected under the new abbreviated reporting option of NFIRS 5.0, several 

data collection concerns need to be addressed.Two issues are noteworthy: the defi nition of confi ned fi res and loss 

thresholds. Structures other than buildings are included as are fires that incur damage beyond the containers. As well, 

often enough the container itself is damaged and casualties may result from even the smallest fi res.These and other 

considerations should be pursued more thoroughly to improve both NFIRS data quality overall and the usefulness of 

the data collected on confi ned fi re incidents.

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In addition, this preliminary analysis of confi ned fi re incidents has led to a new understanding of the analyses 

involved in determining the presence and effectiveness of smoke alarms in all structure fires as well as in these 

confi ned fi res. Further investigations into the appropriate methodologies for smoke alarm analyses would be useful 

to the fi re community at large. 

To request additional information or comment on this report, visit 

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

Notes: 

1.	 NFIRS distinguishes between “content” and “property” loss. Content loss includes loss to the contents of a structure due to

 damage by fi re, smoke, water, and overhaul. Property loss includes losses to the structure itself or to the property itself.Total loss 

is the sum of the content loss and the property loss. For confi ned fi res, the expectation is that the fi re did not spread beyond the 

container (or rubbish for incident type 118) and hence, there was no property damage (damage to the structure itself) from the

 flames.There could be, however, property damage as a result of smoke, water, and overhaul. 

2.	 The analyses presented here are based on the analytic report, Confined Structure Fires, USFA, February 2006. 

3.	 It is important to note that it is the cause profile of the reported data that has changed.This change may not necessarily indicate 

a change in the fi re situation, only in the understanding of the fi re situation. 

4.	 The percentage of occupants alerted varies slightly (from 63% to 65%) depending on the methodology used to analyze the data. 

That separate methodologies yield similar results gives support to the results. 

5.	 These and other recommendations are discussed in Confined Structure Fires (see footnote 2 above). 

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