An 11-year-old girl is credited with alerting five people who were exposed to carbon monoxide.
Officials say a faulty furnace in the home's basement is to blame for Tuesday night's incident in Nashua.
Rescue crews say the five people were dizzy and having trouble breathing; all were hospitalized.
There is no word on their conditions at this time.
Authorities say the girl had noticed an unusual odor and called her father.
The family was outside by the time fire officials arrived on the scene.