at 10:43 hrs Lake Carmel Fire Dept. was dispatch for a burning odor in the basement. Upon arrival of Asst. Chief Churchill and Capt. Lowndes it was determined that an Oil Burner "Blowback" had occurred, As a result of this the residence had filled up with CO gas to a level above 200 ppm. (An allowable level is that of under 8 ppm. with a residence that has cigarette smokers or wood burning stoves operating in them) Chief Keher arrived on scene and assumed command. We responded with an engine and our rescue. Patterson Ambulance and EmStar Medic 4 came to the scene and transported the resident to Putnam Hospital for evaluation. We vented the building for 2 hours. Weather conditions hampered our ventilation efforts due to the high humidity and lack of a breeze. Ventilation fans were set up and the air was monitored till a safe level was established.