What was found
ODORS IN COCKPIT / CABIN: REPEAT WRITEUP. WE DEPARTED KIAD AND CLIMBED TO 3000FT. AT LEVEL OFF, WE TURNED ON THE ENG AND WING ANTI ICE. AS SOON AS WE TURNED ON THE ANTI ICE, WE NOTICED AN UNUSUAL ODOR, SORT OF LIKE A PLASTIC FUME TYPE OF ODOR. WE ELECTED TO RETURN TO KIAD AND THE SMELL REMAINED UNTIL APPROXIMATELY 2000FT. AT 2000FT, WE HAD TURNED THE ANTI ICE OFF. PERHAPS THE ANTI ICE IS ASSOCIATED, OR PERHAPS IT WAS COINCIDENCE, BUT IT DID SEEM TO COINCIDE WITH THE ANTI ICE. CORRECTIVE ACTION: PERFORMED INSPECTION OF ANTI-ICE TUBE. NO DEFECTS NOTED. OPS CHECK GOOD. IAW EMM 72-30-01.