Two men using gasoline-powered chainsaws in the basement of a Storm Lake residence were overcome by fumes Saturday evening. The Storm Lake Fire and Police Departments responded to the scene at approximately 7:57 p.m. on a carbon monoxide complaint. Upon arrival, authorities found one male nearly unconscious, who was transported to Buena Vista Regional Medical Center for treatment, and another who had escaped to the outside of the home uninjured. Firefighters entered the residence with gas monitoring equipment and found elevated levels of carbon monoxide in the basement and first floor of the house. Windows and doors were opened for ventilation.