Carbon monoxide readings in the bathrooms serviced by this heating unit reached over 60 parts per million. People exposed to this level of carbon monoxide typically show symptoms after 4-5 hours of continued exposure.
Firefighters turned off the thermostat to stop the generation of more carbon monoxide, and MGE was called to their location. Meanwhile, Engine 8 and the property owner proceeded to the roof to check the heating unit. Upon returning indoors, they found someone had already turned the thermostat back on. New readings from the bathroom were now over 90 ppm. CO levels as high as 2000 ppm were detected directly from the exhaust of the heating unit, confirming this appliance was the source of the problem.
MGE shut down power to the heating unit and isolated the gas line servicing it. MFD and MGE advised that the unit must not be used again until seen and repaired by a certified technician.
MFD confirmed all air quality readings returned to normal before clearing from the call.
The EMS call that originally summoned Engine 8 to this location was not related to carbon monoxide exposure.