One person was hospitalized due to carbon monoxide poisoning following a 911 call at a Concord home Monday.

Nashua Fire and Rescue responded at about 5:15 a.m. Monday to a single-family home at 3 Unicorn Way when a 911 call reporting “an unusual odor in the building and at least one resident suffering from a medical emergency,” according to a press release..

Engine 5 responding from the Pine Hill Road Fire Station arrived and found the 911 caller waiting for them outside of the residence. Inside the home crews located an additional occupant, unconscious on the floor. A third occupant was also found in a lower level bedroom and removed.

Air monitoring equipment by Fire Rescue personnel indicated elevated readings of carbon monoxide. CO is a  colorless, odorless gas released when fuel burns. A common source of CO poisoning are malfunctioning furnaces or space heaters.

All three of the people were transported to Southern New Hampshire Medical Center for treatment. One of the occupants was later transferred to Massachusetts General Hospital. His condition is unknown at the time of this release.