PEABODY - Dozens of senior citizens were forced out of their public housing complex last night after firefighters detected carbon monoxide at concentrations 15 times higher than the level considered safe.

Seniors are particularly prone to the deadly gas, which prevents the human body from collecting oxygen, according to fire Chief Steven Pasdon.

Pasdon said 17 residents were evacuated from the Peabody Housing Authority's Farnsworth complex at 103 Central St. after boilers malfunctioned. Paramedics checked each resident at the nearby senior center, where one man breathed oxygen from a green bottle in a duffel bag.

At 5 p.m., an hour and a half after firefighters were called to the scene, Pasdon declared the residents would not be able to return home for the night.

Many residents went home with relatives, while others took rooms at the Days Inn paid for by the Housing Authority.

"Everybody's taken care of," fire Capt. Hank Hogan said.

Pasdon praised a new law, which took effect last March, requiring carbon monoxide alarms in homes.

"Thank God for the law, because one of the alarms tripped," he said.

Carbon monoxide is a colorless, odorless gas often created when heating systems burn poorly.

Farnsworth has 35 units, three of which were vacant. Residents returning home later last night were directed by a firefighter keeping watch on the building.

The building was left vacant, with its fire sprinkler system disabled so the water pipes wouldn't freeze. At 7 p.m., crews were still evaluating whether the building's boilers would need to be replaced.

The problem was reported when a resident of Apartment 110 found a carbon-monoxide detector going off and called for help at 3:29 p.m. Pasdon said that while a level of 35 parts per million is considered unsafe, levels of 250 ppm were detected in a common area and 550 ppm in the boiler room.

The carbon monoxide threat didn't particularly worry Virginia Leo, a 17-year resident who had her feet up on a chair at the senior center. Instead, she focused instead on the health threat posed by one of two packages of Lorna Doone cookies given to her.

"140 calories and 60 fat calories," she said. "That'll kill you, clog your arteries, for crying out loud."