What was found
PILOT REPORTED TO MX AFTER LANDING, THAT A BURNING PLASTIC/RUBBER SMELL IN CABIN WITH BLEEDS ON, CABIN TEMP SET TO COLD. MX TROUBLESHOT ACFT AND FOUND RUBBISH UNDER PILOT SEAT AIR VENT. REMOVED RUBBISH AND CLEANED AIR VENT IAW MM 12-20-00. MX OPS CHECKS PERFORMED WITH BLEED SYSTEM ON, NO SMELL OR ANY ODORS NOTED.