West Hartford, CT – A carbon monoxide scare at an apartment building has left some families without heat in the cold.

Carbon monoxide alarms went off inside the apartments at 549 Prospect Ave. Resident Mike MacBeth said he was told to get outside immediately, and fire crews knocked down doors to make sure no one was sleeping inside.

Within minutes, the heat was turned off in the building, on a night that’s been one of the coldest in recent weeks.

By 10 p.m., heat maintenance workers arrived to find the building’s boiler was clogged and had backfired.

Fire crews said the residents were lucky that someone noticed that there was a problem. Carbon monoxide gas is colorless, odorless — and can also be deadly.