An exhaust fan that malfunctioned at the Summerville Filter Plant is being blamed for sending a worker to the hospital yesterday.  According to Plant Superintendent Janice Galloway, the accident was not a leak and was described as a “freak accident.” Galloway said that an exhaust fan that quit working inside the treatment plant in an area that had been closed all night and the fumes had built up inside the area.  The chlorine room at the plant has devices that detect any build up of fumes, but the area where the fumes built up does not have such devices. The worker that was sent to the hospital had difficulty talking and other workers at the plant complained of headaches.  The city worker was treated and released from Floyd Medical Center yesterday afternoon.