Edwardsville, IL — Crews from the Edwardsville Fire Department and Ameren Illinois responded to a carbon monoxide (CO) alarm around 11 a.m. Tuesday at a residence in the 100 block of North Fillmore Street.

“The CO was apparently caused by a blocked or clogged flue pipe,” said Fire Chief Richard Welle. “Ameren turned off the gas to the house to prevent further CO buildup until the flue could be cleared/repaired.”

Welle said a CO detector is usually set to alarm at 35 parts per million (ppm) of CO in the air, well below any critical buildup. He added that 35 ppm is more than one should find on a day-to-day basis in a home.

Welle confirmed that the homeowner’s CO detector registered 296 ppm. While he said that sounds like a lot, another factor to consider is the time-weighted average. He estimates that many people could spend between 15 and 30 minutes in a 300 ppm CO indoor environment before feeling any ill effects.

He said that experts will differ on exact numbers but somewhere around 100 ppm — depending on how long the exposure occurs — one can start feeling nauseous and/or have headaches