Narrative:

As we were leveling off at cruise FL340 I noticed a smell somewhat like fuel/oil mixture coming from the flight deck gasper on my side; and I also sensed a slight burning in my nostrils. We had increased the heat due to the cold of the altitude. I donned my O2 mask and went on 100% for about 3-5 min. My first officer did not notice the smell. When I removed the O2 mask I was able to smell the fumes very clearly and told my first officer to put on his mask. After a few minutes he removed his mask and could then definitely smell the fumes. The flight attendant said that he did not notice fumes in the cabin. We asked the flight attendant to have the commuting captain come up to the intercom so that we could ask him about what he sensed in the cabin. He had been sitting in the rear of the aircraft and said that he did not smell anything in the back but that as he came forward the smell became very apparent. This suggested that the smell could possibly be associated with the left pack. We asked and received an ATC decent to FL250. When we were at FL250 we turned off the left pack and waited to see if the smell subsided. After a few minutes the smell had not detectably diminished. The first officer performed the QRH which ended with 'land at the nearest suitable airport'. We contacted dispatch and were looking at the time two options; which were about 30 minutes. Then dispatch suggested we appeared close to ZZZ which was now just about 20NM in front of us. I had not noticed ZZZ and agreed that this was the closest airport in time. We decided to divert to ZZZ. We declared an emergency and landed in about 10 minutes. Arff equipment met the aircraft upon landing and did not visually observe anything unusual so we taxied off the runway to the parking and deplaned normally.the next morning we met maintenance to perform an engine run-up to check the packs for fumes. Maintenance had discovered fuel puddled in the APU collection pan and had cleaned it out. How ever there was still a presence of fumes in the aft equipment bay. The first run-up still revealed the presence of fumes emanating from the gaspers in the flight deck. Maintenance decided to check and clean the pack filter socks. When he did this he told me he discovered that the left pack sock canister unit was not properly closed and had an opening where air would be sucked into the pack system from the air in the aft equipment bay where the fuel had puddled in the APU pan. After cleaning the sock and properly closing the canister so that it was sealed we did another engine run. This time the presence of fumes was not present.

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Original NASA ASRS Text

Title: CL65 flight crew experienced fuel fumes in the cockpit during cruise at FL340. After attempts to locate and mitigate the cause crew elected to divert to the nearest suitable airport.

Narrative: As we were leveling off at cruise FL340 I noticed a smell somewhat like fuel/oil mixture coming from the flight deck gasper on my side; and I also sensed a slight burning in my nostrils. We had increased the heat due to the cold of the altitude. I donned my O2 mask and went on 100% for about 3-5 min. My First Officer did not notice the smell. When I removed the O2 mask I was able to smell the fumes very clearly and told my First Officer to put on his mask. After a few minutes he removed his mask and could then definitely smell the fumes. The Flight Attendant said that he did not notice fumes in the cabin. We asked the Flight Attendant to have the commuting Captain come up to the intercom so that we could ask him about what he sensed in the cabin. He had been sitting in the rear of the aircraft and said that he did not smell anything in the back but that as he came forward the smell became very apparent. This suggested that the smell could possibly be associated with the Left Pack. We asked and received an ATC decent to FL250. When we were at FL250 we turned off the Left Pack and waited to see if the smell subsided. After a few minutes the smell had not detectably diminished. The First Officer performed the QRH which ended with 'land at the nearest suitable airport'. We contacted Dispatch and were looking at the time two options; which were about 30 minutes. Then Dispatch suggested we appeared close to ZZZ which was now just about 20NM in front of us. I had not noticed ZZZ and agreed that this was the closest airport in time. We decided to divert to ZZZ. We declared an emergency and landed in about 10 minutes. ARFF equipment met the aircraft upon landing and did not visually observe anything unusual so we taxied off the runway to the parking and deplaned normally.The next morning we met maintenance to perform an engine run-up to check the packs for fumes. Maintenance had discovered fuel puddled in the APU collection pan and had cleaned it out. How ever there was still a presence of fumes in the aft equipment bay. The first run-up still revealed the presence of fumes emanating from the gaspers in the flight deck. Maintenance decided to check and clean the pack filter socks. When he did this he told me he discovered that the left pack sock canister unit was not properly closed and had an opening where air would be sucked into the pack system from the air in the aft equipment bay where the fuel had puddled in the APU pan. After cleaning the sock and properly closing the canister so that it was sealed we did another engine run. This time the presence of fumes was not present.

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.