MADISON, Wis. — An apartment building in downtown Madison had to be evacuated overnight due to a carbon monoxide leak, fire officials said Friday morning.
The Madison Fire Department says it was called to the Avenir building at 510 W. Washington Ave. at 11:44 p.m. Thursday to investigate a carbon monoxide alarm. The department says only one of the carbon monoxide alarms in the building was sounding — one installed on the 6th floor — but their air monitors immediately detected carbon monoxide in the main-level lobby.
The firefighters’ initial readings found carbon monoxide levels at 18 parts per million (ppm), but those levels escalated to nearly 60 ppm as they continued into the building, leading them to pull the building’s fire alarm to try to get everyone out.
Firefighters from Engine 1 and Ladder Co. 1 continued to look for the source of the carbon monoxide while the department notified MG&E and the property manager. At first, they thought the source may have been the underground parking garage, with exhaust fumes accumulating there and spreading through the building due to the underground ventilation system now working — but they were ultimately unable to definitively prove the garage was the source of the carbon monoxide.
Crews worked to ventilate the garage and hallways, but even after a thorough ventilation process, CO levels in individual units were still around 20 to 35 parts per million. Firefighters made the decision to call for a complete evacuation of the building due to the unsafe levels of carbon monoxide until the issue was resolved.
A repair technician arrived to fix the parking garage ventilation system while firefighters were still on the scene, as property management said they would help pay for hotel costs for the residents who were displaced. Firefighters left the scene just after 3 a.m., with the department saying no illnesses were reported from the carbon monoxide exposure.
The Avenir building opened in 2022 at the corner of W. Washington Ave. and Bassett St., replacing a number of houses that were previously in that space.
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