MDFR officials cannot point to a single instance in which county firefighters have detected or prevented a fire at a building under fire watch. "The purpose of firewatch is prevention of hazardous situations, " Lorenzo wrote. "By definition, that means we are taking actions to intercept possible threats to life safety before they occur."

One fire watcher directed a lost engine to a burning house from the roof of Quayside, said MDFR Capt. William Van Meter, who runs the fire-watch program.

DECLARING A WATCH A fire watch is required by law when a building's fire alarm or sprinkler system is broken and cannot be fixed within four hours. In Miami-Dade, a fire inspector not only declares the fire watch, but also decides how many MDFR firefighters are needed. The watch ends when the inspector approves the repairs.

Some business owners say they feel squeezed.

"It was as bad as the Mafia up North, " said Robert Birke, a former construction supervisor for the Turner Austin Airport Team, which until last summer was the prime contractor on the massive North Terminal expansion at Miami International Airport.

When consultants for the Miami-Dade Aviation Department questioned a $54,000 fire-watch bill last fall, MDFR Chief Financial Officer Scott Mendelsberg and Chief Lorenzo threatened to end fire watch at MIA and shut down a concourse.

"Mendelsberg's attempt to extort money from MDAD is unacceptable, " airport project director John Cosper wrote to his bosses on Oct. 19.

Closing the concourse "would have just caused chaos in the terminal. It would have been a disaster, " Cosper said later. Ultimately, the airport paid up.

"We did not want to resort to such an extreme measure, " Lorenzo wrote to The Miami Herald, "we felt that MIA had created a climate that required assertiveness." He said the fire department had previously "made extensive attempts" to collect.

PAYING FOR FIRE WATCH

In several interviews, Capt. Van Meter explained the department's practices this way: "You either pay us or you shut down. . . . Usually, it's cheaper to pay us."

Who pays? Often, it's business owners or condo associations whose buildings have failed inspections. They are charged under a schedule of per-hour costs set by the County Commission in 2004. But in cases of public buildings, such as MIA or the library, taxpayers cover the costs and it's all overtime, no matter how long the shifts.

National standards for fire watch require that the person on duty stays awake, patrols the building and has some way to contact the fire department in case of trouble. A cellphone will do.

Many South Florida jurisdictions, including the cities of Miami and Miami Beach, allow the use of private guards for the patrols.

"I don't see a need to pay a firefighter $45 an hour to walk up and down a hall, " said Key Biscayne Fire Chief Franklin Barron.

Fire departments in New York City, Philadelphia, Washington, San Francisco and Los Angeles also rely on private citizens for fire watch.

"It could be anybody, " said Ron Cabrera, a battalion chief with the fire prevention unit of the Los Angeles County Fire Department.

Lorenzo said his department's policy is mandated by a local fire code that requires firefighters to patrol any "performance, exhibition, display, contest or activity" that might pose a safety risk. The code says nothing about fire watches at buildings with inoperable alarms - but Fire Marshal Mena said it applies to them, too.