What was found
SMELL OF SMOKE IN FWD CABIN, SMOKE ALARM WENT OFF IN FWD LAV FOR 60 SECONDS, RECEIVED SMOKE LAV WARNING MESSAGE. FLIGHT 6355. ON ARRIVAL, INSPECTED FWD LAV FOR ANY SIGNS OF BURNED WIRING, LIGHT BULBS OR ELECT ISSUES, NONE FOUND. OPERATED PACKS AND RAN BOTH ENGINES IN REFERENCE TO CRJ 900 AMM 71-00-00 AND AMM 21-51-00, NO SMOKE FOUND AND FWD LAV SMOKE DETECTOR DID NOT TRIGGER PERFORMED FURTHER TROUBLESHOOTING IN REFERENCE TO CRJ 900 FIM 26-16-00, ALL OPS CHECKS OF SMOKE DETECTORS GOOD. CREW MENTIONED SERVICE DOOR WAS OPEN AT TIME EVENT, FURTHER INVESTIGATION NOTED PLACEMENT OF GPU EXHAUST TO BE VERY CLOSE IN PROXIMITY TO SERVICE DOOR & WHEN STARTED, PRODUCED SUBSTANTIAL SMOKE, WHICH MOVED TOWARDS SERVICE DOOR, AT THE TIME OF DISCREPANCY EVENT, GPU WAS BEING STARTED & SOON AFTER, EVENT OCCURRED ALONG WITH STRONG SMOKE ODOR ON EXTERIOR OF ACFT BUT CONFIRMED NOT TO BE AIRCRAFT ITSELF, BELIEVE CAUSE FOR EVENT WAS GPU SMOKE MIGRATING INTO FWD CABIN TRIGGERING SMOKE DETECTOR EVENT, NO 30 DAY HISTORY NOTED, ALL OPS CHECKS GOOD, AC OK FOR SERVICE