Madison, WI – A furnace malfunction that caused a carbon monoxide leak was discovered thanks to a working carbon monoxide detector located in the apartment next door. No working detectors were found inside the primary unit, however.

Ladder Co. 6 responded to the 2400 block of Parker Place for a report of a fire alarm. Upon arrival, an occupant opened their door and waited outside in their vehicle while firefighters investigated the alarm. The crew determined it was a carbon monoxide alarm that was sounding, and they also noted the odor of furnace exhaust.

Firefighters used a handheld air monitor to check for carbon monoxide, finding readings of 35 parts per million (ppm) on the first floor of that apartment unit. In the basement, readings climbed to 100 ppm. The crew confirmed the exterior furnace exhaust pipe was clear of snow, so that was not the cause of the CO buildup. As they continued to investigate the CO source, they set up fans to ventilate the home and clear the air.

Meanwhile, the crew visited an adjacent apartment unit to make sure it was not also impacted by carbon monoxide. The smell of furnace exhaust was also noted there, with CO levels even higher than in the previous apartment unit. Firefighters immediately began clearing the air, and they found there were no working carbon monoxide alarms in the home.

MGE arrived to assist, and MGE confirmed the source of the CO was a furnace malfunction. The occupant of that unit had just arrived home, did not experience any adverse side effects of the carbon monoxide exposure, and did not require EMS.