"I'd like to spend all my time with my husband, if I could," she says. "We never argue. We do almost everything together."

Including working in the same building.

By sheer coincidence, chief and deputy chief are both based at Engine 47 in Grays Ferry. He was assigned there in late 2005. About a year later, her unit relocated from Fire Administration Headquarters at Third and Spring Garden Streets.

Even with similar four days on/four days off shifts, the two are so busy on the job they rarely interact.

A homebody at heart, Schweizer femme eschews brews with the boys to retreat to her Burholme twin, where her pride and passion is a landscaped 5,000-gallon fish pond.

Stocked with 64 exotic fish, including 20 koi, it's designated as a national wildlife preserve. She decorates it for all seasons, complete with ornaments and figurines.

"The little pond grew into a big pond - and a big hobby," Schweizer says. "It's like my getaway. I can forget about everything. Some people watch TV or sew. I like to take care of my pond."

Especially the five koi she raised from small fry to 30 inches in length. Named them, too - Redhead. Yellow. Popsicle. "If I ever move, my fish are coming with me," she says.

Two dogs, one cat, and a pair of lovebirds (yes, really) complete the menagerie. No partridges or pear trees.

Along with animals and the outdoors, Schweizer has a thing for numbers. A human speed-dial, she keeps hundreds of digits in her head. She can read something once and commit it to memory.

"Diane can do anything, whether it's writing computer programs, riding Jet Skis, or doing mathematical equations," according to her father, Bill Kuehner, a retired engineer.

Accomplishment runs in the family. Brother Bill, 41, is a physician; sister Karen, 35, a physical therapist; and sister Nancy, 29, an elementary school teacher. Their mother, Marilyn, taught high school physics and math.

"We're kind of a vanilla family," says Dr. Bill, an internist in Allentown. "We don't skydive. We're just kind of plain guys and girls."

Nothing plain about Chief Schweizer's love of water-skiing. She can do it all day long. More than once, she and Nancy have run out of gas and have had to paddle to shore.

Schweizer graduated from the University of Scranton in 1990 with a degree in math. During her junior year, she studied at the London School of Economics. In '92, she earned a master's in emergency medical services from Hahnemann University.

When Schweizer joined the department in '95, there were fewer than a dozen women. Firehouses had no separate facilities. Bathroom stalls had no doors; bathroom doors had no locks. Women used the officers' bathroom.

There are now 113 women among a total of 2,111, according to department figures. Sixty-seven women make up almost 32 percent of the paramedics. Among firefighters, women are only 2.5 percent of the 1,551-person force.

As a woman, Schweizer swears she's never had a bad experience at work.

"You have to be a certain kind of woman to be in this job," she says. "You have to be secure, believe in yourself, and be strong-willed. Whether you realize it or not, you're a minority.