What was found
(CAN) DURING CLIMB OUT, FLIGHT CREW OBSERVED THE SMOKE ANNUNCIATOR LIGHT ILLUMINATE SEVERAL TIMES. THEY ACTIONED THE QRH, DECLARED A PAN PAN IN THE INTEREST OF FLIGHT SAFETY, AND REQUESTED A RETURN. THE F/A CHECKED THE REAR BULKHEAD WHICH WAS NOT HOT, THERE WAS NO ACTUAL SMOKE OBSERVED. CARGO AREA INSPECTED POST SHUTDOWN WITH NO DAMAGE OR SMOKE ODOR PRESENT. BOTH SMOKE DETECTORS TESTED USING TEST FUNCTION AND ACTUAL SMOKE WITH NO FAULT, FOUND NR 2 SMOKE DETECTOR FULL OF DUST PARTICLES, REPLACED NR 2 SMOKE DETECTOR AND FUNCTION TESTED.