PORTLAND — Firefighters are crediting a sprinkler system in a Cumberland Avenue apartment building with putting out a fire in an overstuffed chair.

Firefighters were called to 457 Cumberland Ave., Cumberland Park Place Apartments, at 3:30 a.m. Wednesday where they found water dripping from the second floor and heavy smoke inside an apartment there, said Deputy Chief Robert Wassick.

Firefighters learned that a 74-year-old woman, who was on oxygen but had turned it off, had lit a cigarette and a spark or ash fell into the chair and started the fire. She tried to stamp it out, but couldn’t, Wassick said, and retreated to a neighbor’s apartment.

A single sprinkler head discharged, putting out the fire and setting off an alarm that summoned firefighters, Wassick said. The woman was treated for a burn to the side of her hand, he said.

The apartment will need to be renovated because of smoke and water damage but there was no damage to other units, he said, adding that without the sprinkler system, the fire would have been much worse.