What was found
THE PILOT DEPARTED THE BASE EN ROUTE FOR A PATIENT. OUTSIDE AIR TEMP WAS 3 3DEG F. THE HEATING & DEMISTING SYS WAS SWITCHED ON. AS THE AIRCRAFT STARTED TO HEAT UP WE NOTICED A STRONG ODOR, IT WAS NOT THE NORMAL SMELL OF THE HEATING SYS WARMING UP BUT A STRONGER SMELL. THE PILOT TURNED THE HEATING & DEMISTING SYS OFF, OPENED THE PILOTS WINDOW & ABORTED THE FLIGHT & RETURNED TO BASE. THEY LANDED WITHOUT INCIDENT & THE AIRCRAFT WAS SHUT DOWN & THE MECHANIC NOTIFIED. THE MECHANIC INSPECTED THE SYS & FOUND NO DEFECTS. A GND RUN & FLIGHT CHECK WERE COMPLETED WITH NO NOTICEABLE SMELLS OR DEFECTS NOTED. THE AIRCRAFT WAS THEN RETURNED TO SERVICE.