Downtown High Rise Evacuated Due to Carbon Monoxide Incident

An apartment building was evacuated overnight out of concern for the safety of residents when a carbon monoxide leak was found but its source could not be identified.

Engine Co. 1 responded to 510 W. Washington Avenue at 11:44 p.m. Thursday to investigate a carbon monoxide alarm. Only one alarm was sounding, on the sixth floor; however, when firefighters entered the building, their air monitors immediately detected the presence of carbon monoxide in the main-level lobby. With initial readings at 18 parts per million (ppm), the crew continued into the structure, and CO levels climbed to upwards of 60 ppm. Firefighters pulled the building’s fire alarm to begin an evacuation.

MFD notified MGE of the situation and also called for the property manager. Meanwhile, Engine 1 continued to search for the source of carbon monoxide, and they summoned the assistance of Ladder Co. 1 to aid the investigation.

Crews initially believed the source was the underground parking garage, where exhaust fumes may have accumulated and spread through the common hallways as a result of the underground ventilation system not working. However, they could not definitively prove that this was the source. Once the garage and hallways were thoroughly ventilated, firefighters still found carbon monoxide levels around 20-35 ppm in individual apartment units of the high-rise structure.

It was at this time firefighters determined it wouldn’t be possible to ensure the safety of the residents if they were to return to the building. Crews called for the complete evacuation of the building until the source of the carbon monoxide could be identified and resolved.

A repair technician did respond to address the parking garage ventilation system while firefighters were on site. Property management indicated they would assist with hotel costs for the displaced residents. MFD crews cleared from the call at 3:01 a.m., turning the property back over to property management and the HVAC repair technician.

No illnesses resulting from carbon monoxide exposure were reported.