Washington, DC – A defective furnace is to blame for a carbon monoxide scare in a Northwest D.C. neighborhood that forced 11 people to evacuate their homes and left one family without a place to live on Christmas Eve.

Firefighters were called to a row house on Gallatin Place Northwest near 2nd Street Northwest, in the Brightwood Park neighborhood, just after midnight, for an activated carbon monoxide detector.

They discovered a high concentration of carbon monoxide in the house but quickly realized that the poisonous gas was coming from a house next door.

“We eventually traced the source to the adjacent home and found that there were very high CO levels both in that home and a third home,” D.C. Fire and EMS Spokesman Vito Maggiolo told WTOP.

Firefighters shut down the defective furnace in the neighboring home and ventilated all three homes before CO levels returned to normal.

What made matters worse was that there were no working carbon monoxide detectors in the house with the defective furnace.

“If it wasn’t for the adjacent home having one and the Carbon Monoxide traveling into the adjacent home activating their carbon monoxide detector, the results could’ve been tragic,” Maggiolo said.

All three row homes were evacuated. Eight adults and three children were treated for exposure to carbon monoxide. One child was transported to a hospital for evaluation but is expected to recover.

The Red Cross is helping the family that lives in the house with the defective furnace find a temporary place to stay.

Maggiolo said the incident is a reminder of why every house should have a working carbon monoxide detector.

“We call carbon monoxide the silent killer,” Maggiolo said. “You can’t see it. It’s odorless, it’s colorless, and in high concentrations, it will kill you.”