Just before 1pm Monday afternoon fire department received a call for smoke at 300 Chestnut Street apartment complex.  Upon arrival they did not find smoke but residents complained of feeling ill.  Firefighters metered and found readings of 70 to 80 parts per million, anything above 10 is considered hazardous.  This affected 5 apartments, 3 of the families were home and checked out by American Medical Response EMTs and did not require and additional treatment.  The flue on the furnace had worked itself loose so each time the furnace ran it released carbon monoxide into the apartments.    The gas company arrived on scene and the furnace was repaired.  Fire officials remained on the scene until 3:00pm ventilating the apartments.