A faulty furnace is the probable cause of the carbon monoxide symptoms that affected three men working on a remodeling project at a building located at 216 South Third Avenue in Sturgeon Bay Wednesday. The three crew members said they were not feeling well, had experienced dizzy spells and may have passed out. The Sturgeon Bay Fire Department used a gas meter to determine that the carbon monoxide level was at an extremely high 554 parts per million at the front door. The furnace was shut down, the building vented, and the workers were taken to Door County Medical Center where they exhibited extremely high carbon monoxide levels. The building’s owner alerted the fire department to the possible problems with the furnace. The fire department indicated that the environment in the building was dangerous given the high level of carbon monoxide. Six firefighters and four vehicles responded to the call at 11:45AM. They cleared the scene at 12:57PM.