Boston Emergency Medical Services reports taking seven people to the hospital Wednesday afternoon after an apparent problem with a heating repair job sent high levels of carbon monoxide into the air.

Ambulances responded to 14 Woolson St., around 4:30 p.m., Boston EMS says.

The Boston Fire Department reports the seven people included one man working on the three decker's oil-fed heating system and said the gas may have gotten inside due to "possible separation of the duct work that carried the furnace gases outside.:

Boston EMS adds, "CO illness symptoms include dizziness, nausea, headache and can come on quickly."

The Boston Fire Department reports crews shut the heating systems all all three floors of the three decker. After tests showed no further signs of carbon monoxide, the department says it's likely residents will be allowed back in.