What was found
PHL FLT 1024 EN ROUTE SJU TO PHL. ON CLIMBOUT FROM SJU, ABOUT 20,000 FEET, TURNED ON ENGINE ANTI-ICE AND NOTICED A BURNT RUBBER SMELL. SMELL LASTED FOR ABOUT FIVE MINUTES AFTER THE ANTI-ICE WAS TURNED OFF, IT WAS NOTICED THROUGHOUT THE CABIN. REPLACED ALL EIGHT RECIRCULATION FILTERS, FORWARD AND AFT, LEFT AND RIGHT POSITIONS. NO SMELL NOTICED ON GROUND RUN. A SATISFACTORY TEST FLIGHT WAS ACCOMPLISHED, WITH THE ANTI-ICE OPERATED ABOVE FL 200 FOR ABOUT 30 MINUTES. NO ODORS NOTED.