Incident Type: 
Carbon Monoxide
Monday, September 18, 2023 - 1:53am
Monday, September 18, 2023 - 2:00am
900 block East Johnson Street
Madison, WI
An occupant of a multi-residential building dialed 911 early Monday morning to report their carbon monoxide alarm had been going off for the past two hours or so. Engine Co. 3 arrived at 2:00 a.m. and were met by a separate occupant who reported feeling mild symptoms that could indicate carbon monoxide (CO) exposure.
E3 surveyed the entire building with an air monitor to determine the presence of CO. Very low levels were found in a first-floor kitchen. CO level readings in a rear living area jumped to 116 parts per million (ppm). Prolonged exposure to this level of CO can result in headaches, fatigue, dizziness, and nausea.
Firefighters worked with occupants to try to determine what was causing the elevated CO. Nearby parked cars, a backyard fire pit, and gas appliances inside the building were ruled out as sources. No abnormal CO readings were found in any of the other residential units besides the first floor.
The affected room was aired out and ventilated, bringing CO levels back down to 0 ppm. As a precaution, natural gas service to all appliances was shut down. Occupants planned to notify their landlord of the issue in the morning. Meanwhile, Engine 3 advised occupants to call 911 if their CO alarms activate again.
About two hours later, at 3:49 a.m., Engine 3 received a second call to the address for an active CO alarm. This time, an occupant noticed that a wall located near the elevated CO levels was "warm." Firefighters used a thermal imaging camera to confirm there were heat signatures on both the interior and exterior sides of the wall, clocking in at about 110-120 degrees Fahrenheit. The vinyl siding and other materials were removed, exposing smoldering insulation and charred studs near electrical conduits that had degraded. The smoldering insulation was removed and the area began to cool down.
MGE arrived on scene and shut down electrical power to the building. Property management was notified of the situation immediately. No additional instances of CO-related illness were reported, and EMS response was not required.
Posted 09/18/2023 - 11:51am

Cynthia Schuster (Public Information Officer)