Correction Appended

LIKE many people, Mark Bridger, a math professor in Newton, Mass., has relied on a laptop computer to help him keep up with his work when he travels. So he took his Dell Inspiron 3800 along on a trip to his Maine vacation home last fall.

But one morning, while Mr. Bridger and his wife were in the garden, they noticed that smoke had started to fill their living room, where he had left his computer, and that a bookcase in the corner had caught fire.

Firefighters arrived in time to save the house. But while the fire seemed a freak accident at first, investigations by representatives from Mr. Bridger's insurance company, the Consumer Product Safety Commission and Dell Computer found that it had originated in Mr. Bridger's computer. The investigators concluded that the computer had been left too close to a wood-burning stove and that its lithium-ion battery had overheated and caught fire.

These days, lithium-ion batteries are used in virtually all high-end laptops, most camcorders and many of the newer wireless phones. They have built-in circuitry to monitor heat buildup, as well as voltage, charge and other indicators, meant to shut the batteries down if problems are detected.

Manufacturers and safety experts say it is rare for the batteries to overheat, smoke or cause a fire. But several PC makers have recalled portable computers because of potential hazards associated with such batteries.

In October, Dell recalled 27,000 Latitude and Inspiron laptops after receiving a report of a computer fire. The problem was linked to pieces of metal found in the laptops' lithium-ion batteries (made by Sanyo) that could have caused the batteries to short-circuit and start a fire.

The same month, Compaq recalled 55,000 Armada laptops after a customer complained that the Sony lithium-ion battery in an Armada had short-circuited and emitted smoke. In 1995, Apple recalled its PowerBook 5300 models after the electrolytes in the lithium-ion battery caught fire.

Lithium-ion batteries can produce four volts, or four times the power of nickel metal hydride batteries, which were used in most laptops until a few years ago. While producing more energy, lithium-ion batteries are also smaller and lighter than nickel metal hydride batteries and therefore produce more heat and are more sensitive to it.

Lithium-ion batteries are also different from other types of rechargeable batteries in that their electrolytes, the medium through which the lithium ion moves from one electrode to the other during the charging process, are not water soluble. This makes them more susceptible to short-circuiting if exposed to moisture than nickel metal hydride batteries.

Since the fire, Mr. Bridger said, he has expressed concern to Dell that its user manuals are not explicit enough about the hazards of leaving laptop computers too close to a heat source. ''They should have a warning in the manuals against leaving laptops fewer than three feet away from radiators, stoves or fires,'' he said.

Tom Kehoe, a spokesman for Dell Computer, said consumers who follow the guidance in its user manuals should not have overheating problems with lithium-ion batteries. ''There is a recommended temperature range that you're supposed to operate them between, which is minus-14 degrees Fahrenheit and 140 degrees Fahrenheit,'' he said. ''Those numbers are clearly spelled out in the manuals.''

Norm England, president of the Portable Rechargeable Battery Association, a trade group, warned consumers away from using lithium-ion batteries made by generic battery-pack assemblers rather than name-brand manufacturers like Sony, Panasonic and Sanyo. Although some name-brand lithium-ion batteries have been involved in product recalls, Mr. England said the number of incidents prompting the recalls was relatively small compared with the millions of lithium-ion batteries produced each year.

The generic batteries, he said, may not have built-in safety features or certification by Underwriters Laboratories. But because most lithium batteries in the United States come from major manufacturers, he said, ''I don't see any cause for concern.''

Still, Jim Jester, a computer consultant and owner of Professional Computer Services, in The Woodlands, Tex., said manufacturers could do more to warn consumers to take precautions. ''Modern lithium-ions do get warm, and people have bad habits like leaving their laptops on beds and under piles of paper while the batteries are charging,'' he said.

He said his Motorola StarTac wireless phone, which uses a lithium-ion battery, tended to overheat when he left it charging in its polyurethane case. ''Sometimes it's enough that I worry it's going to melt the inside of the case,'' he said.

Mr. Jester advises against charging wireless phones or laptops in cars when it is warm. ''Safety switches can fail, and charging in a warm room, or with heat in a car, is dangerous,'' he said. ''Manufacturers could mention more about not getting these things too hot.''