What was found
ON CLIMBOUT, HOT BURNED AIR SMELL CAME IN COCKPIT AND CABIN W/ ENG ANTI-ICE IN USE. F/A REPORTED THIN MIST/SMOKE INAFT CABIN AND SMOKE ALARM ACTIVATION IN AFT LAV. SMELL DISIPATED, SMOKE CLEARED AND SMOKE ALARM STOPPED WHEN ENG ANTI-ICE SECURED. FOUND LEFT THRUST REV ISOLATION VLV RETURN LINE LEAKING TIGHTENED B-NUT, LK CK GOOD. CLEANED TAIL COMP, RAN ENG TO T/O PWR WITH PACKS ON. NO FUMES OR SMOKE NOTED WITH ENG ANTI-ICE ON.