Narrative:

We were en-route when we noticed a burning type odor in the cabin. I was the pilot not flying in the right seat. We were in icing conditions with the ice detector light illuminated. We had the wing; engine and tail anti/deicing systems turned on. This wasn't the first time we were in icing conditions for the day. We had tested the icing systems before the first flight of the day and also used the icing systems during the previous two flights. To me; the odor smelled a little like burning hair or hot plastic; not like a typical 'fire' smell. The odor wasn't 'visible' in the cabin; but once we noticed the odor it seemed to be getting stronger. I went back to the rear of the cabin to briefly investigate. I felt the sidewalls of the cabin which were not hot; I went to the lavatory and noticed the odor was growing much more intense. I returned to the cockpit; the co-captain transferred the controls to me and then went back to briefly investigate. At this point; we agreed we needed to exit the icing conditions; so we could turn the anti/deice systems off. We declared an emergency with ATC and diverted to an airport 25 miles away. Once we turned the icing systems off; the odor seemed to diminish. However; we weren't sure if this was truly the case; since your body can 'get used' to an odor over a few minutes time. We landed without incident. From the time we noticed the odor to the time we landed; we were on the ground within 12 minutes give or take a few. The emergency vehicles had been dispatched and were waiting for us upon exiting the runway. Upon our request; the trucks did a 360 around the aircraft to determine if there were any visible abnormalities. All appeared normal; so we taxied to the FBO; shutdown and the emergency personal inspected the aircraft with thermal video equipment. During this event; there was never any visible sign of the odor. Upon the thermal inspection; emergency personal did not find any 'hot spots.' however; they did notice a faint odor in the rear blower air inlet located in the lavatory.

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Original NASA ASRS Text

Title: A BE400 crew declared an emergency and diverted to a nearby airport after an overheated equipment smell filled the aircraft. A lavatory fan was suspected.

Narrative: We were en-route when we noticed a burning type odor in the cabin. I was the pilot not flying in the right seat. We were in icing conditions with the ice detector light illuminated. We had the wing; engine and tail anti/deicing systems turned on. This wasn't the first time we were in icing conditions for the day. We had tested the icing systems before the first flight of the day and also used the icing systems during the previous two flights. To me; the odor smelled a little like burning hair or hot plastic; not like a typical 'fire' smell. The odor wasn't 'visible' in the cabin; but once we noticed the odor it seemed to be getting stronger. I went back to the rear of the cabin to briefly investigate. I felt the sidewalls of the cabin which were not hot; I went to the lavatory and noticed the odor was growing much more intense. I returned to the cockpit; the Co-Captain transferred the controls to me and then went back to briefly investigate. At this point; we agreed we needed to exit the icing conditions; so we could turn the anti/deice systems off. We declared an emergency with ATC and diverted to an airport 25 miles away. Once we turned the icing systems off; the odor seemed to diminish. However; we weren't sure if this was truly the case; since your body can 'get used' to an odor over a few minutes time. We landed without incident. From the time we noticed the odor to the time we landed; we were on the ground within 12 minutes give or take a few. The emergency vehicles had been dispatched and were waiting for us upon exiting the runway. Upon our request; the trucks did a 360 around the aircraft to determine if there were any visible abnormalities. All appeared normal; so we taxied to the FBO; shutdown and the Emergency personal inspected the aircraft with thermal video equipment. During this event; there was never any visible sign of the odor. Upon the thermal inspection; Emergency personal did not find any 'hot spots.' However; they did notice a faint odor in the rear blower air inlet located in the lavatory.

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.