Fire Commissioner Nicholas Scoppetta, who took the helm of a wounded department in the aftermath of the Sept. 11 attacks, has decided to leave the job at the end of the year.
In an interview on Thursday, Mr. Scoppetta, 76, who has held several high-ranking jobs in five decades of public life, said he was exploring teaching possibilities at various city universities, just as he had been doing when Mayor Michael R. Bloomberg tapped him to lead the Fire Department in January 2002.
"The reason I am leaving now is I have decided, after 47 years, that if I am ever going to get to those other things, like teaching and writing, and some traveling," said Mr. Scoppetta, "I better get to it now." His departure is effective Dec. 31.
Mr. Scoppetta said he and the mayor had had no specific discussions about a successor. He declined to name candidates.
Reacting to the news, Stephen J. Cassidy, the president of the Uniformed Firefighters Association, a firefighters' union, issued an e-mail statement through a spokesman that said, "The Scoppetta years were not kind to the Fire Department of the City of New York."
John J. McDonnell, the past president of another union, the Uniformed Fire Officers Association, said he and Mr. Scoppetta had "agreed to disagree" on some occasions. "We sort of had some rocky roads, but we maintained an open-door policy, which, as a union official, was one of the most important things you can ask for," Mr. McDonnell said.
In a statement praising Mr. Scoppetta, Mr. Bloomberg noted his service as the first commissioner of children's services; as an assistant United States attorney; as a member of the Knapp Commission on police corruption; and as the city's commissioner of investigation.
Under Mr. Scoppetta's leadership, the statement said, "the city has experienced the fewest fire deaths on record, and our firefighters and E.M.S. personnel are getting to fires and medical emergencies faster than ever."
But Mr. Scoppetta's tenure was also marked by a fire in August 2007 at the former Deutsche Bank building that killed two firefighters and exposed serious lapses in the department's building inspection procedures.
Prosecutors considered charging New York City criminally in the firefighters' deaths but did not, citing legal obstacles. However, the Bloomberg administration admitted the city's complicity in the deaths.