Cell phone fires called extremely rare

Cause most likely to be an overheated aftermarket battery
Carl T. Hall, Chronicle Science Writer

Those portable electronic devices in our pockets and purses can do a lot more than make phone calls these days. They can browse the Internet. They can send and receive e-mail. They can play songs and music.

And they can spontaneously combust.

Luis Picaso, 59, of Vallejo was in critical condition Tuesday at UC Davis Medical Center in Sacramento after a cell phone caught fire in his pants pocket late Saturday night while he was asleep. The accident set Picaso's fast-burning nylon clothing ablaze and left him with second- and third-degree burns over at least half his body, authorities said.

Bill Tweedy, spokesman for the Vallejo Fire Department, called it a freak accident.

That judgment drew little argument from cell phone safety experts, who noted that only about 100 cell phones have caught fire, based on one government report covering 2002 to 2004, and there are now more than 200 million phones in use.

A fire from a cell phone is very rare, and the industry has adopted manufacturing standards aimed at reducing the risk even more, said Joe Farren, spokesman for the CTIA-The Wireless Association, a trade group of cell phone providers and manufacturers.

No fatalities seem to have been reported. Fiery cell phones seem to be less of a risk than, say, being struck by lightning, which kills about 75 people and injures 300 each year in the United States.

Officials haven't released details or brand names in the case of the Vallejo tragedy. That makes it difficult to assess whether anyone else might be at special risk. Even if it is a one-of-a-kind type incident, the Vallejo incident underscored the inherent danger of any portable power source, including the ubiquitous lithium-ion battery packs in cell phones and other pocket-size consumer products.

"You have to pack more and more energy into a small package, and when you're doing that you're really creating a little bomb, especially when the battery is fully charged," said Carl Hilliard, president of the Wireless Consumers Alliance, a nonprofit organization that has tallied several incidents involving people injured by "exploding cell phones." Cell phone manufacturers and engineers have other words for it, such as "venting with flame" or "thermal runaway" events. Whatever the euphemism, a suddenly malfunctioning battery can generate a lot of heat in very little time.

There have been media reports of cell phones catching fire in someone's pocket, in a person's hands, and, in at least one case in December 2003, during a phone call. In that instance, a man's ear was singed as he talked with his girlfriend.

The Consumer Product Safety Commission has announced at least three product recalls, including a voluntary recall in January 2004 of batteries used in Kyocera Wireless Corp. cell phones. The agency cited four reports of battery failure and one minor burn injury. Nokia, another manufacturer, has issued warnings about counterfeit batteries that have the potential to explode.

The Wireless Consumers Alliance used to keep a tally of such incidents on its Web site, http://www.wirelessconsumers.org/, but has since gone on to other hazards, such as overly aggressive cell phone marketing and deceptive advertising.

For consumers, the biggest danger occurs from overcharging when using poor-quality counterfeit batteries.

Protection circuits are built into rechargeable lithium-ion batteries to prevent excessive charge voltages during use. Recharging devices also are designed to cut off when safety limits are reached.

These safety features rarely fail, but cheap aftermarket batteries and some portable car chargers may lack adequate safeguards, Hilliard said. He pointed out that damage may occur when a phone or battery is dropped.

"The public should be warned to handle these instruments with care," he said. "They're not like your car keys. You can't just toss them in the corner."

Lithium offers advantages to battery-makers because of its high-energy density and low weight, but the metal proved unstable during recharging. That led to the current popularity of lithium-ion batteries, which feature lithium in a nonmetallic form.

They are undeniably safe, but they are still portable power plants that convert chemical energy into electrical current.

The membranes used to separate internal battery components are getting thinner and thinner to improve performance and reduce size. That puts a premium on quality manufacturing methods, said Isidor Buchmann, chief executive of Cadex Electronics Inc., a Vancouver, British Columbia, company that makes battery testers and other devices.

"The energy density has doubled, by making the separation membranes thinner," he said. "So now they are very, very thin, so they can be rolled up very small."