DES MOINES, IA -- A carbon monoxide leak at A.F. Johnson Millwork, a manufacturer of architectural millwork, sent 11 workers to the hospital Jan. 15, according to The Associated Press.

Hank Evans, owner of the West Des Moines company, says several employees started to feel ill, so the plant manager called 911. Firefighters determined that the level of carbon monoxide in the plant was four times higher than the amount that is considered safe. The problem was a leak in a duct, which allowed furnace exhaust into the plant.