In an update to a story from last weekend, officials say firefighters found deadly levels of carbon monoxide inside a Waterloo event complex that was hosting a monster truck rally where dozens of people were sickened. The Courier reports that levels of more than 300 parts per million were detected Saturday inside the National Cattle Congress Hippodrome. Waterloo Fire Rescue Battalion Chief Bill Beck said levels higher that 50 ppm would warrant an evacuation. The federal Consumer Product Safety Commission says sustained exposure to levels over 200 ppm could cause death. Television station KWWL reports that local hospitals reported that 77 people from the event were treated in their emergency rooms. Another battalion chief, Ben Petersen, said he assumed exhaust from the trucks was the cause of the high levels.
