U.S. Fire Administration

TOPICAL FIRE RESEARCH SERIES

Volume 2, Issue 5

July 2001 (Rev. March 2002) 

Residential Air Conditioner Fires

FINDINGS

S Residential A/C fires result in less injury (60/year) and death (about

5/year) than other residential fires.

S 75% of A/C fires occur in one- and two-family dwellings.

S 35% of installed A/C units are either portable or fixed local units, yet

these account for 55% of all A/C fires.

S 86% of A/C fires are caused by mechanical failure or malfunction; half

of these are from short circuits.

S A/C fires are highest from 2 to 8 p.m., the period when the demand for

air conditioning is at its peak.

Sources: NFPA and NFIRS

Each year in the United States, an average of 2,300 air conditioning fires occur in

residential structures. These fires are responsible for approximately 60 civilian injuries,

less than 5 civilian deaths, and $23.8 million in property loss.

1 As of 1997, nearly threequarters (72 percent) of all American households had air conditioners or air conditioning

systems. Forty-seven percent of all households have central air conditioning systems and

25 percent have window/wall air conditioning units.

2

This topical report examines some of the major characteristics of residential air conditioning fires.
-

LOSS MEASURES

Data from the National Fire Incident Reporting System (NFIRS) (1996 -1998) (Figure 1) show that dollar loss from residential air conditioning fires is slightly lower than

that averaged across all residential structure fires. Residential air conditioning fires tend

to result in significantly less injury and death than other residential fires.

Figure 1. Loss Measures for Air Conditioning Fires

(3-year average, NFIRS data 1996–98)

MEASURE

Dollar Loss/Fire

Injuries/1,000 Fires

Fatalities/1,000 Fires

Source: NFIRS only

ALL RESIDENTIAL

STRUCTURE FIRES

$11,271

48.0

7.7

AIR CONDITIONING

FIRES*

$10,558

27.8

0.5

EQUIPMENT INVOLVED IN A/C FIRES

The term air conditioning fires applies to those fires in which central air conditioning units, fixed local air conditioning units (usually wall units), or portable local air conditioning units (usually window units) were identified as the equipment involved in the

ignition of the fire. Figure 2 illustrates the proportions of the air conditioner systems

involved in these fires.

0 10 0 0 0 0

Percent

Figure 2. Leading Equipment Involved in

Air Conditioning Fires

(3-year average, NFIRS data 1996–98)

Central Air

Conditioning Equipment

Fixed, Stationary Local

Air Conditioning Unit

Portable Air

Conditioning Unit

Source: NFIRS only

2 3 4 5

Central air conditioning equipment fires are more common in apartments (58%);

portable air conditioner and fixed local air conditioner equipment (window and wall

units) fires are more common in one- and two-family dwellings (also 58%).
Although window and wall air conditioning units account for 35% of the air conditioning equipment in residences, they cause 55% of air conditioning equipment fires.

This may be due to smaller, undersized wiring that was not designed to carry the power

load required by air conditioning equipment. Homes with central air conditioners generally have dedicated circuits appropriately sized for this equipment.

WHERE A/C FIRES START

The majority of residential air conditioning fires occur in one- and two-family

dwellings (75%) (Figure 3). Another 20% occur in apartments, with the remaining 5%

occurring in other residential occupancies such as dormitories and boarding houses.

0 10 0 0 0 0 0 0 80

One-/Two-Family Dwellings

Apartments

Other Residences

Percent

Figure 3. Air Conditioning Fires by Residential Type

(3-year average, NFIRS data 1996–98)

Source: NFIRS only

2 3 4 5 6 7

Overall, the bedroom (23%) and the lounge area (14%) are the leading areas where

these fires originate in residential structures. These are the areas where window or wall

units are most commonly found.
TIME OF DAY

Figure 4 illustrates the 24-hour distribution of residential air conditioner fires.

Thirty-five percent of residential air conditioning fires occur between 2 and 8 p.m. It is

not unusual for air conditioning units to be at full power during this period. Air conditioning fires coincide with the sustained level of air conditioning usage during this time

period.

0

1

2

3

4

5

6

7

Figure 4. Air Conditioning Fires by Time of Day

(residential structures, 3-year average, NFIRS data 1996–98)

Percent

2400-01000100-02000200-03000300-04000400-05000500-06000600-07000700-08000800-09000900-10001000-11001100-12001200-13001300-14001400-15001500-16001600-17001700-18001800-19001900-20002000-21002100-22002200-23002300-2400

Source: NFIRS only

Air temperatures are usually at their highest between 2 and 3 p.m. Air conditioning

fires reach their highest peak between 7 and 8 p.m. This difference may be because

working families set their thermostats at a high temperature while they are at work to

save energy, and turn them down when they return home. The air conditioning units must

then work at full power to cool the warm house to the lower temperature.

Air conditioning fires decrease during the late evening and overnight hours. The

lowest incidence of air conditioning fires occurs before dawn when the air temperature is

generally at its lowest.

IGNITION FACTORS

Eighty-six percent of residential air conditioning fires are ignited as a result of some

type of mechanical failure or malfunction. The leading factors contributing to these

mechanical failures and malfunctions is a short circuit (51%) or other electrical failure

(22%) in the air conditioning unit. In many cases, air conditioner units run at full capacity during the hottest summer months and are not always routinely inspected or maintained, often causing the mechanical failures or malfunctions that result in fire.
EXAMPLES

S Firefighters fought a blaze in New Jersey late April, 2000 but were unable to save

three residents. The fire was began when an undersized air conditioner overheated.

The fire had been smoldering for hours before the firefighters arrived on the scene.3

S In June 2000, a fire broke out in Augusta, Maine, in the early morning. The residents of the home escaped. The cause of the fire was determined to be an air conditioner that overheated, setting the carpet and furniture on fire.

4

S An air conditioner overheated in a Brooklyn, New York, apartment July 23, 2001,

igniting a sofa and ultimately killing two adults. Their 3-year-old son was spared

because his father put him in a water-filled bathtub.5

CONCLUSION

Product maintenance, routine inspection, and the installation of smoke alarms can

aid in the prevention or reduction of air conditioning fires. For further information on air

conditioning fires, contact your local fire department or the USFA.

NOTES:

1. National estimates are based on National Fire Incident Reporting System (NFIRS) data (1996–1998)

and the National Fire Protection Association’s (NFPA) annual survey, Fire Loss in the United States.

2. “1997 Residential Energy Consumption Survey,” Energy Information Administration. See also

http://www.ela.doe.gov/emeu/consumptionbriefs/recs/aircond_use.html.

3. Firehouse Magazine, April 24, 2001.

4. Augusta Chronicle, June 14, 2000.

5. New York Post, July 24, 2001.

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