Narrative:

The lead flight attendant told me that all the flight attendants were smelling something. I then came out and investigated the smell. It was an electrical smell similar to hot plastic and seemed to be coming from the large overhead vent directly outside the cockpit. I then smelled the air from each of several galley eyeballs. They did not have a smell to them. This doesn't really make sense because all the vents get air from the same source. But the bad smell was clearly coming from the large vent. The smell was noticeable; but not very strong.after some difficulty with radios; I called dispatch and maintenance control. They decided they wanted the plane in ZZZ. I changed our destination to ZZZ. Initially; I told ATC we were diverting for a maintenance item; but did not have an emergency. About 10 minutes later the flight attendant called and said the smell was worse and seemed to be throughout the cabin. We were below 10;000 ft. I declared an emergency and told ATC we would be exceeding 250 KTS below 10;000 ft.the remainder of the flight was uneventful. We were joined at the gate by a few maintenance people and the fire trucks. The passengers deplaned. While in flight; I had kept the reason for the diversion vague and explained more completely to them before they exited.

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Original NASA ASRS Text

Title: A B717-200 flight crew declared an emergency and diverted when the Captain confirmed flight attendants' reports of a burning odor in the cabin while en route.

Narrative: The Lead Flight Attendant told me that all the flight attendants were smelling something. I then came out and investigated the smell. It was an electrical smell similar to hot plastic and seemed to be coming from the large overhead vent directly outside the cockpit. I then smelled the air from each of several galley eyeballs. They did not have a smell to them. This doesn't really make sense because all the vents get air from the same source. But the bad smell was clearly coming from the large vent. The smell was noticeable; but not very strong.After some difficulty with radios; I called Dispatch and Maintenance Control. They decided they wanted the plane in ZZZ. I changed our destination to ZZZ. Initially; I told ATC we were diverting for a maintenance item; but did not have an emergency. About 10 minutes later the Flight Attendant called and said the smell was worse and seemed to be throughout the cabin. We were below 10;000 FT. I declared an emergency and told ATC we would be exceeding 250 KTS below 10;000 FT.The remainder of the flight was uneventful. We were joined at the gate by a few Maintenance people and the fire trucks. The passengers deplaned. While in flight; I had kept the reason for the diversion vague and explained more completely to them before they exited.

Data retrieved from NASA's ASRS site as of April 2012 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.