Narrative:

On climb out from bwi, we noticed a burning smell along with smoke in the cockpit. Also at that time, the lavatory smoke detector sounded. I told the flight attendant to check the lavatory. When he opened the door, the alarm stopped. After he closed the door the alarm sounded again. We proceeded with the emergency checklist, declared an emergency, and returned to bwi. The passenger were evacuate/evacuationed and no fire or damage was found.

Google
 

Original NASA ASRS Text

Title: SMOKE IN COCKPIT WITH ASSOCIATED LAVATORY SMOKE DETECTOR SOUNDING. EMER DECLARED, ACFT LANDED WITH PAX EVAC.

Narrative: ON CLBOUT FROM BWI, WE NOTICED A BURNING SMELL ALONG WITH SMOKE IN THE COCKPIT. ALSO AT THAT TIME, THE LAVATORY SMOKE DETECTOR SOUNDED. I TOLD THE FLT ATTENDANT TO CHK THE LAVATORY. WHEN HE OPENED THE DOOR, THE ALARM STOPPED. AFTER HE CLOSED THE DOOR THE ALARM SOUNDED AGAIN. WE PROCEEDED WITH THE EMER CHKLIST, DECLARED AN EMER, AND RETURNED TO BWI. THE PAX WERE EVACED AND NO FIRE OR DAMAGE WAS FOUND.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.