Air conditioners are meant to keep your home cool, but they can have quite the opposite effect if malfunctions occur. No joke: Between 2005 and 2009, A/C equipment caused an annual average of 2,346 home fires, according to the National Fire Protection Association (NFPA). The blazes resulted in an average of 2 deaths, 99 injuries, and $53 million in property damage.

The NFPA data doesn’t distinguish between room A/Cs and central air conditioning. But the data does indicate that 27 percent of fires start in the bedroom, while just 11 percent start in a duct. That suggests that room A/Cs are the bigger culprit. An earlier report by the U.S. Fire Administration confirms this, showing that room units account for 55 percent of all home fires, even though they’re just 35 percent of installations.

Electrical and mechanical failures, such as a short circuit, are the leading cause of A/C-related fires. Routine inspection is the best defense against electrical mishaps, especially if your home has antiquated wiring. And make sure smoke alarms are installed throughout your home and that they're in good working order.

You also need to maintain your A/C equipment, which will minimize the risk of fire while also improving its efficiency. With room A/Cs, that means cleaning the filters once a month during the cooling season, and replacing filters that are damaged. Also, regularly vacuum coils and fins with an upholstery-brush attachment. And avoid “short cycling” by waiting 5 minutes after shutting off the unit before restarting it. That will allow pressure in the refrigeration system to equalize, avoiding stress on the compressor.

Ready for a new A/C? Check our Ratings of several dozen models, as well as buying advice on sizing the unit to your space.

If you have central air conditioning, have a licensed professional change all filters; clean and flush the coils, drain pan, and drainage system; vacuum the blower compartments; and check the refrigerant and mechanical components.