Caroline Paul's ''Fighting Fire'' -? ''Baywatch'' star Alexandra Paul's twin sister authored a new book about her experience as a firefighter

Caroline Paul is not the woman most people assume she is. That would be her identical twin sister, Alexandra, whom suburbanites and satellite-dish-toting tribesmen alike recognize as Lieut. Stephanie Holden, David Hasselhoff’s former boss on the planet’s most popular television show, Baywatch.

Caroline doesn’t even own a bright red bathing suit. She’s more likely to be snapped and Velcroed into her 25-pound firefighter’s coat, steel ax dangling at her side. But that doesn’t stop the mistaken-identity routine. ”I could be coming off a fire truck,” says Caroline, an eight-year veteran of the San Francisco Fire Department who has authored a new book about her experiences called Fighting Fire, ”and someone will say, ‘Hey, you’re that girl from that Baywatch show. The one with the real breasts.”’

TV is a powerful force, especially when worldwide syndication is involved, but it’s got nothing on fire. And Caroline Paul is crazy for fire. Her behind-the-flames account, just published by St. Martin’s, is a rare glimpse through female eyes into the testosterone-laden world of the firehouse. (Paul, 34, was one of just 16 women in the 1,400-person SFFD when she joined in 1989; there are now 134.) Fighting Fire offers perhaps the most compelling explanation yet as to why some people actually enjoy the window-shattering, blood-boiling, bone-melting heat of a roaring blaze. ”Fire taps something ancient and vital in each of us, something both snarling and reverential,” Paul writes. The book’s fine prose and unsparing details (let’s just say the human body does not grill especially well) could make it the next nonfiction adventure book to scale the best-seller list: Think of it as Into Thick Air or The Perfect Firestorm.

She speaks with near-religious fervor about ”fast burners” and ”total combustion” and about the primeval interplay of smoke, flame, steam, and ash. ”If there’s a fire, I want to be there,” she says. ”Maybe because in being so close to death, I think I understand what it means to be truly alive.” Paul knows she doesn’t fit the firefighter mold. ”I wasn’t raised to do a blue-collar job,” she admits, referring to her Stanford communications degree and her privileged upbringing in West Cornwall, Conn., where her parents, Sarah and Mark Paul, a social worker and investment banker, reared their twin daughters and son Jonathan. (In 1993, he was jailed for contempt in a well-publicized animal-rights case.) The only portent of Caroline’s future came when Jonathan started a fire behind the family’s country house. ”I stared, fascinated, at the deep black bruise that the flames left on the field,” she writes.

Paul took the fire-department entrance exam in 1988 for a radio story she wanted to write. Her initial curiosity turned into fascination and then a career. ”Most people go to the office and sit at a desk,” she says. ”When firefighters go to the office, we might birth a baby in the morning, save a drowning surfer in the afternoon, and run into a fire at night. What could be more interesting than that?” Her family supported her choice, though her father concedes, ”It was initially a surprise. And I still worry about the dangers of the job.”