What was found
ON CLIMBOUT OF KGEG THE LAVATORY SMOKE DETECTOR WENT OFF. F/A "A" INVESTIGATED AND THE LAV WAS UNOCCUPIED, NO SIGNS OF SMOKE, FIRE OR HEAT. NO ONE HAD VISITED THE LAV, NO SIGN OF ANY TAMPERING OR OTHER PRODUCTS LIKE HAIRSPRAY THAT COULD TRIGGER IT. F/A "A" TOUCHED THE SMOKE DETECTOR AND THE ALARM STOPPED. WE RAN THE LAVATORY SMOKE DETECTOR CHECKLIST TO COMPLETION AND MADE THE DECISION AS A CREW TO CONTINUE AFTER TALKING WITH MCC. REMOVED FROM SERVICE. REMOVED LAV SMOKE DETECTOR REF Q400 26-12-11-000-801. INSTALLED LAV SMOKE DETECTOR W/NEW FROM STOCK REF 26-12-11-400-802. OPS CHECK PASS. AIRCRAFT RETURNED TO SERVICE.