Those living in Harvard’s undergraduate Houses for the summer may be sweating through the July heat—but when the mercury plummets this fall, students won’t be able to resort to dorm room fireplaces for warmth, former Dean of the College Harry R. Lewis ’68 announced in one of his final acts as dean.

Citing safety concerns, Lewis issued a memo last month prohibiting any use of the roughly 1,700 fireplaces in the Houses, except those in the suites of House masters and senior tutors. Fireplaces in Yard dorms have been covered up since the early 1990s, according to Zachary M. Gingo, manager of administrative operations for Harvard Yard.

“The risk is sufficiently high and the consequences of a failure so catastrophic that it is simply imprudent to continue as we have been and to hope for the best,” Lewis wrote in the memo.

Gingo said he was unsure whether the ban would be enforced by physically blocking chimneys and fireplaces or simply by threat of disciplinary action. Lewis declined to comment.

Associate Dean of the College Thomas A. Dingman said that the ban was not provoked by any particular fire caused by fireplaces in the Houses.

“We’ve banned smoking and candles,” he said. “It began to feel odd to us that there was still the provision for making fires in the fireplaces.”

But Dingman said there have been a number of near-misses involving fireplaces with closed dampers—incidents which did not ultimately lead to disaster but might have.

“It’s not a huge number,” he said. “But all you need is one.”

Gingo said that the fire that badly damaged the Eliot House Grille in November 2001 made College officials “more sensitive to the risks of fire.”

“We are fortunate not to have had a more serious incident,” Lewis wrote in his memo.

Still, some students were not swayed by administrators’ arguments.

Matthew W. Mahan ’05, who is chair of the Undergraduate Council’s Student Affairs Committee, said that concerns could be addressed without a ban on fireplaces.

“The reality is that the two real safety concerns stem first, from the University’s refusal to implement a fireplace safety training program and second, from a lack of funding for proper fireplace equipment, such as screens and pokers,” he wrote in an e-mail, adding that he thought the administrators’ position “defies logic.”

But Lewis shrugged off the idea of fire-safety education as ultimately unhelpful in the memo.

“Training in the use of fireplaces could not lower our risks sufficiently to make their continued utilization wise,” he wrote.