"Extension cords are one of the most abused electrical accessories in the house," says Allen Gallant, a master electrician in the Boston area. They are also one of the most dangerous: The U.S. Consumer Product Safety Commission attributes some 3,000 residential fires and a couple of thousand injuries each year to extension cords.

Safety Do's

Compare labels to avoid overloading cords: The wattage of an appliance should never exceed the wattage capacity of the cord. Illogically, extension-cord packaging makes no mention of wattage; it specifies the maximum number of amps, or amount of current, the cord can handle. A 16-gauge cord — labeled "16AWG" — is good for small-load appliances, such as lamps and clock radios. Use a 10- or 12-gauge cord for power tools and portable heaters. In general, the thicker the cord, the more wattage it can handle.

Fully extend the cord before plugging it in. A looped or kinked cord can accumulate heat.

Use only cords labeled for exterior use when powering outdoor holiday lights, spotlights, lawn mowers, and other lawn tools.

Safety Don'ts

Don't plug extension cords together. Use one cord long enough to do the job on its own.

Never run cords across a wet floor or wet ground, and never run them under rugs. Cords retain heat when covered, which can result in fire.

If a cord is hot to the touch, unplug and discard it.