Narrative:

I was the first officer and the pilot flying. After takeoff both the captain and I noticed an unusual smell. We discussed the possibility of the smell coming from the extremely high pollen count in the area and hoped that the smell would lessen soon. As we climbed through about 10;000 feet; the flight attendants called and said there was a strong burning smell in the cabin. The captain asked them to walk through the cabin to try to identify the source and report back to him. As we made a left turn toward the east and started a climb to 14;000 ft. On the SID; a flight attendant called back and said that the smell was very strong and smelled like burning propane; nothing like she had ever smelled in an airplane before. The captain told the flight attendants to prepare to land immediately; that we were going to return. The captain declared an emergency to ATC and told them we had fumes in the airplane and were returning. We donned our oxygen masks; as I took the radios and the captain did the QRH. We got vectors for the return visual approach. The captain was making pas and talking to the flight attendants while I was working with ATC to get a lower altitude and left turn back to the final approach course. We completed the descent; approach and landing checklists; and landed. During the approach; the fumes had almost completely dissipated. After landing; the captain told me to make a PA telling the passengers to remain in their seats so there would hopefully be no uncommanded evacuation. We taxied to the gate. I remember that during this time of the year there used to be bulletins to pilots telling of emergency returns due to a burning smell from the air conditioning system. If I remember correctly; we anticipated this and maybe even made pre-take off pas telling people that during this time of year it was common to get a strange smell in the cabin due to extremely high amounts of pollen getting heated up in the AC system. I don't know if the reason for our emergency was pollen in the AC system or not; but I do know that I have never smelled this strong a smell on the 757. If; through investigation; it turns out that our problem was most likely due to burning/heated pollen; then I would recommend those same old bulletins get distributed to the 757 group. I felt that ATC could have done a little better job communicating with us and getting us turned into the airport sooner. There was a NOTAM that the old departure/approach frequency was changed to a new permanent one (I forgot what we used); but when we were trying to come back to the airport; ATC assigned me the old frequency which I tried to no avail. There was no response after a couple of tries. There is already enough task saturation during an emergency to have to be doing multiple frequency changes trying to find someone to talk to. Apparently this particular controller was unaware that that frequency was no longer being used when he/she assigned it. So as I was trying to expedite the descent and approach; I feel there was an unnecessary delay in communication.

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Original NASA ASRS Text

Title: A B757 Flight Crew and Flight Attendants noticed unusual fumes and odor; declared an emergency; and returned to departure airport. Burning pollen was mentioned as a possible cause.

Narrative: I was the First Officer and the Pilot Flying. After takeoff both the Captain and I noticed an unusual smell. We discussed the possibility of the smell coming from the extremely high pollen count in the area and hoped that the smell would lessen soon. As we climbed through about 10;000 feet; the Flight Attendants called and said there was a strong burning smell in the cabin. The Captain asked them to walk through the cabin to try to identify the source and report back to him. As we made a left turn toward the East and started a climb to 14;000 ft. on the SID; a Flight Attendant called back and said that the smell was very strong and smelled like burning propane; nothing like she had ever smelled in an airplane before. The Captain told the Flight Attendants to prepare to land immediately; that we were going to return. The Captain declared an emergency to ATC and told them we had fumes in the airplane and were returning. We donned our oxygen masks; as I took the radios and the Captain did the QRH. We got vectors for the return visual approach. The Captain was making PAs and talking to the Flight Attendants while I was working with ATC to get a lower altitude and left turn back to the final approach course. We completed the descent; approach and landing checklists; and landed. During the approach; the fumes had almost completely dissipated. After landing; the Captain told me to make a PA telling the passengers to remain in their seats so there would hopefully be no uncommanded evacuation. We taxied to the gate. I remember that during this time of the year there used to be bulletins to pilots telling of emergency returns due to a burning smell from the Air Conditioning system. If I remember correctly; we anticipated this and maybe even made pre-take off PAs telling people that during this time of year it was common to get a strange smell in the cabin due to extremely high amounts of pollen getting heated up in the AC system. I don't know if the reason for our emergency was pollen in the AC system or not; but I do know that I have never smelled this strong a smell on the 757. If; through investigation; it turns out that our problem was most likely due to burning/heated pollen; then I would recommend those same old bulletins get distributed to the 757 group. I felt that ATC could have done a little better job communicating with us and getting us turned into the airport sooner. There was a NOTAM that the old departure/approach frequency was changed to a new permanent one (I forgot what we used); but when we were trying to come back to the airport; ATC assigned me the old frequency which I tried to no avail. There was no response after a couple of tries. There is already enough task saturation during an emergency to have to be doing multiple frequency changes trying to find someone to talk to. Apparently this particular Controller was unaware that that frequency was no longer being used when he/she assigned it. So as I was trying to expedite the descent and approach; I feel there was an unnecessary delay in communication.

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.