Last week's fire on Bonsal Street in Southeast Baltimore was typical — a one-alarm blaze in the middle of the night in a brick rowhouse. It was under control in about 45 minutes.

As firefighters poured water on the last of the burning embers, the five occupants huddled under white blankets in the back of an ambulance, one holding a small black dog named Amy. They spoke only Spanish, and with a relative translating, the owner said only that he heard "pee-pee-pee" from the alarm. He said, "I woke everybody," including the two renters living in the basement.

Danner, the fire investigator, traced burn patterns on the walls to the small basement bathroom, which was filled with 3 inches of thick, black water. There he found what appeared to a makeshift switch with wires outside the wall, "instead of inside where they're supposed to be."

But Danner said he believes the fire started in the wiring above the ceiling fan, which might have overheated. Other wiring, he said, "appeared to be hooked up the way it was supposed to be."

While the number of fire fatalities has decreased, the number of patients treated at hospitals may be increasing. City fire officials had no statistics on the numbers of people who survive, but the burn center at Johns Hopkins Bayview Medical Center is reporting a surge of patients from fires.

"We have never been so busy," said the director, Dr. Stephen Milner, saying he's adding staff to the unit, which serves as a regional trauma center for Maryland and five other states. He said the number of people treated has doubled from 250 to 500 over the past five years.

"It seems like we've seen quite a lot of patients from house fires," he said. Most patients burned over half their bodies go on to lead a "good quality life," whereas a few decades ago those same people had "little chance of surviving," he said.

Busiest in the nation

The number of fire deaths in Baltimore has varied significantly over the years. For example, 47 people died in 1965, a number that jumped to 84 in 1966 and then dropped to 33 the following year. In 1984, the city's deadliest year for fires, 19 people died in four fires, two of which occurred in less than 24 hours. Nine of the victims were children, and six died in an arson fire above a strip club on The Block.

While deaths have decreased, Baltimore firefighters remain among the busiest in the nation — the Steadman station near Camden Yards had more runs in 2010 than any other station in country, rolling out emergency vehicles 60 times a day. The department had 270,000 runs last year, about 100,000 more than Boston, Detroit and Washington.

Baltimore fire officials say the city is challenging because of its aging, 19th-century housing stock, with connected rowhouses and common spaces running underneath the flat roofs. Such areas, called cocklofts, can allow a fire to quickly spread across an entire city block.

Other troublesome factors are the high crime rate, thousands of vacant shells and vast swaths of poverty.

Clack and other firefighters point to the city's impoverished neighborhoods as a prime reason the city has so many fires — 3,544 last year, down from 4,695 in 2006.

Boston, by comparison, had 4,111 fires last year but only one death, and zero deaths in 2010.

Boston, said Baltimore's fire chief, "is a different social dynamic." It has fewer people living in poverty and spends more per capita on fire services than Baltimore. Firefighters in Baltimore encounter people living in squalid rental homes without electricity, with space heaters plugged in to their neighbors' outlets using extension cords draped out of windows.

"Poverty makes you focus on different things," Clack said. "You're focused on where you're going to get food to eat, having a place to live where you don't get rained on, how to keep warm. If you're not sure where you're going to get your next meal, the fact that your smoke alarm doesn't have a battery is not high on your list."

Baltimore Fire Marshal Raymond C. O'Brocki said causes of fire include frayed extension cords — people forget they have a limited life span — and overloaded power strips, especially in older houses that haven't been renovated.

"Who in the 1800s anticipated a flat-screen TV in every room, and a phone charger in every outlet?" O'Brocki said.

The city's stock of vacant housing also contributes to fatalities. A study last year by the Bloomberg School of Public Health found that the risk of fire increases 10 percent for people living next to a vacant rowhouse. "We lose a lot of people in vacant buildings or near vacant buildings," Clack said.

Budget problems may also play a part. Fire companies are closed on a rotating basis every day, prompting the firefighters union to issue nearly daily warnings that residents are in peril. Mayor Stephanie Rawlings-Blake has cut the closures from three to two a day.