"We haven't bought one engine or fire truck in five years," Clack said. "We need to free up money to get the fleet newer."
Several studies have raised concerns about longer work hours for firefighters, and extended hours for professionals such as doctors and pilots have been a topic of national debate.
"An individual's physical performance declines after long periods without sleep," states a 2006 paper by the Ontario Association of Fire Chiefs. It adds that people "working 24 hours or more make more mental and technical errors than those working no more than 16 hours."
A 2001 study in the British medical journal The Lancet found that workers who logged back-to-back shifts on their 16th hour displayed the cognitive performance of someone with .05 percent blood-alcohol level.
Still, 24-hour shifts are the norm for many workers. And Clack and other proponents say firefighters' ability to rest and sleep at work makes such shifts a reasonable option.
Howard and Montgomery counties require firefighters to work for 24 hours, followed by 48 hours of rest. Anne Arundel County firefighters work a 24-hour shift, with 72 hours off. Baltimore County uses a similar schedule to Baltimore's current model.
Clack said paramedics' jobs are too demanding to work 24 hours straight, and the Fire Department's 250 paramedics are not included in the proposal.
But 82 percent of calls to the department are for paramedics, while only 18 percent require firefighters to respond, Clack said.
Fires killed fewer people — 12 — in Baltimore last year than in any previous year since such deaths have been tracked, officials said. The chief credited the change to a program that gives out free smoke detectors and an ordinance requiring new construction to include sprinklers.
Several City Council members have expressed concern about the longer hours, but said they wanted to see a formal proposal.
"I know fatigue takes place when you're out there going into these vacant buildings and fighting fires, criss-crossing the city," said Council President Bernard C. "Jack" Young. "I can't make a decision right now because I haven't seen anything. It's something where we're going to have to work with the unions, because I'm quite sure we can get a win-win out of this."