Still, the gloves were of little use inside the building. The railings were so hot from the fire they could not hold on, and the marble stairs cracked from the heat. Soon, he said, the cold produced a different effect: The stairways iced over, and firefighters began slipping and falling.

“You can imagine how difficult it was to carry unconscious people down a flight of stairs that was ice-covered,” Lieutenant Conboy said. “It was like ice-skating down a waterfall. That slows us down. Hooking up to the water slows us down, slipping on the water in the street — everything slows down because of the cold.”

The fire commissioner, Daniel A. Nigro, said six firefighters sustained sprains or strains, and an emergency medical technician slipped on ice and broke his ribs. In an interview Friday, Mr. Nigro said the cold weather certainly presented “a struggle,” but insisted that the frozen hydrant had not affected responders’ efforts to fight the blaze.

Mr. Nigro said the city’s fire engines are equipped with 500 gallons of water that can be used while waiting to connect to a hydrant, though it is not enough water to combat a blaze.

After Thursday, 71 people have died in fires in New York City this year, up from 48 last year. Twenty-four of those have come in December alone — the deadliest month in 10 years, Mr. Nigro said.