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MADISON, Wis. — The second time was the charm for first responders searching for the cause of elevated carbon monoxide readings at a multi-unit home in Madison early Monday morning.
Firefighters responded to a report of a carbon monoxide alarm sounding at the home in the 900 block of East Johnson Street around 2 a.m. A resident told firefighters the alarm had been sounding for roughly two hours; another resident reported mild symptoms possibly indicating carbon monoxide exposure, according to a Madison Fire Department incident report.
Firefighters traced the highest concentration of carbon monoxide to a rear living area but were unable to identify a source after ruling out nearby vehicles, appliances and a fire pit.
After ventilating the building, firefighters told the residents to call 911 if the alarm sounded again — which it did around an hour and 45 minutes after the first call. One of the occupants reported a wall near the elevated carbon monoxide levels was warm to the touch.
When firefighters returned, they used a thermal imaging camera to identify heat signatures on the wall, the report said. After removing the siding from the outside of the wall, they found smoldering insulation and charred studs near degraded electrical conduits.
