Dorchester, MA – By Mac Daniel, Globe Staff|

Three adults and three children, including a 5-month-old, were treated for carbon monoxide poisoning yesterday after the potentially deadly odorless gas filled a Dorchester house.

Deborah Barboza, 26, said she and her 7-year-old daughter, Deja Cheeks, had been suffering from headaches and sleeplessness off an on for week. Yesterday morning, her daughter awoke at 6 a.m. complaining of dizziness, she said.

”If I’d fallen back asleep, there was a chance I wouldn’t have woken up,” Barboza said.

Boston Emergency Medical Service and fire officials were dispatched to the home at 52 Nelson St. at about 8:30 a.m. Carbon monoxide testers reported an unacceptable level of gas when firefighters arrived, said a Boston EMS spokesman, Christopher Stratton. All natural gas appliances were then shut off, and the windows were opened to allow the gas to escape. Fire officials said they did not know what had caused the gas to fill the home.

Calls to the city’s Inspectional Services Department, which also responded to the scene, were not returned yesterday.

Cheeks was treated in a hyperbaric chamber at Massachusetts Eye and Ear Infirmary and was released. Barboza and four other family members were also treated and released.

Carbon monoxide poisoning kills about 300 people annually in the United States. An Ashland family almost succumbed to the gas this month because of a faulty furnace.

Under a law passed after a 7-year-old Plymouth girl died of carbon monoxide poisoning in January, the state requires most homes to have carbon monoxide detectors by March 31. But as fuel costs rise this winter, fire officials say the problem probably will grow as residents turn to alternative heat sources to save money.

Exposure to carbon monoxide can cause flu-like symptoms and can be fatal. Massachusetts fire departments responded to 2,844 carbon monoxide calls in 2004, according to the state Department of Fire Services.