WASHINGTON , D.C. — Fire Chief Dennis L. Rubin says it’s a “99 percent certainty” that the fire that heavily damaged a branch of the Georgetown public library recently was started by a worker using a heat gun to remove old paint. That’s a good reason to consider the risks of a tool that blows air as hot as 1,000 degrees to soften paint for quicker removal.

Fire Department spokesman Alan Etter said turning to a heat gun is tempting. “I have used one,” he said, noting that it’s faster than paint-stripping chemicals. But there are hazards.

“Any time you have an open heat source, an open flame source, there is a danger for this kind of thing to happen,” he says.

Todd Lumpkin, housewares manager of Logan Hardware, in Washington, sells the $21.99 Ace Dual Temperature Heat Gun. It looks like a hair dryer and blows air over heated coils at 750 and 1,000 degrees.

“Honestly, I would never recommend this to you myself,” Etter said. In many old homes, he said, “the wood is like matchsticks. It’s old, it’s dry, it’s brittle.”

And fire is not the only hazard. Lead was a key ingredient in paint until its use was outlawed in 1978. When heated above 1,000 degrees, lead paint vaporizes and releases toxic fumes. Experts advise consumers to assume any home built before 1978 contains lead-based paint.

So what’s the best way to remove paint and varnish from doors, windows, mantels and moldings? Very carefully, says Gordon Bock, editor in chief of Old-House Journal magazine.

“Any methodology that can lift paint can do damage to the building and do damage to yourself, your children and your pets. People think it’s an innocuous process because it’s relatively low-tech. Do your homework.”

Here are some alternatives:

• Infrared paint strippers. Tools using infrared heating elements can remove paint and varnish at lower temperatures than many heat guns. The rectangular devices, which can be bulky to maneuver, radiate heat between 380 and 750 degrees. (Some wood ignites at 745 degrees.) These tools also have drawbacks.

Doug Rosner, owner of DHR Construction, near Frederick, Md., uses the Speedheater. It can scorch wood “if you leave it on an excessive amount of time,” he said. Those dark marks remain visible under a clear finish. The devices cost about $400, he said. (For details, go to www.speedheatersystem.com.)

• Chemical strippers. These usually come in paste or liquid form and are applied by brush, roller or sprayer. They can work in as little as 10 minutes or as slowly as 8 hours. Once the paint gets soft or blistered, it can be scraped off with a putty knife or specialty tool. Some chemical strippers are highly flammable; others contain carcinogens and can cause breathing problems or burns.

Strippers “are a way to prevent putting lead particles in the air,” said Bill Thornton, owner of Potomac Paint, in Virginia. But they are “not for the faint of heart.” He cautions users to maximize ventilation and wear “long sleeves, chemical-resistant gloves and something to protect your eyes.” Taking paint-layered doors, window frames or mantelpieces outside for stripping can minimize risk.

Products containing methylene chloride, the most commonly used paint-removal chemical, are called solvent or marine strippers. They work the fastest and may require more than one application. Those made with sodium hydroxide (lye) are called caustic strippers and take longer to work.

“Ecological” strippers claim not to contain methylene chloride or caustics. Thornton said they are not as effective as those with “killer chemicals.” The Consumer Product Safety Commission warns that some self-described eco-friendly strippers “may be hazardous despite the [citrus] smell and environmental claims.”

• Sanding. Old-fashioned elbow grease and sandpaper also has drawbacks: Sanding by hand or machine creates dust that can trigger allergies. Sanding lead paint can release dust containing hazardous lead particles.

If lead is present, said Bock, “you want to seal off the room, wear a protective, disposable suit and disposable respirator.” Or call a pro. Rosner quotes $600 to $800 per window, which includes room-sealing, outdoor venting, HEPA-filter vacuuming and licensed disposal of all dust and debris. At those prices, some may decide just to paint right over the previous 15 coats.