Narrative:

The lead flight attendant advised me that we would need a new passenger oxygen bottle. She informed me that the flight attendant working the aft galley said he smelled something during the final part of our descent that made him feel nauseous and gave him a headache. He administered himself oxygen and that made him feel better. The other flight attendant who was working the aft cabin said she had a little headache, but didn't smell anything unusual. We advised maintenance and I discussed what could cause a smell in just the aft galley. The first thing that came to mind was some sort of APU bleed duct malfunction. The APU wasn't on during the descent, but we decided to disconnect the external air-conditioning unit and run the packs off the APU to see if some smell developed. Nothing did. We next decided to ask the people working in the aft cargo compartment if they had noticed any unusual smells when they opened the cargo compartment -- once again nothing noted. With the aft lavs right next to the galley, I though maybe the smell was coming from them. So we ensured the lavs were svced and the trash from the galley emptied. The ovens in the galley were off at the time of incident, so that ruled out any type of electric fumes. The flight attendant said it smelled just like 'this.' both the mechanic and I and the other flight attendants couldn't smell anything but the outside 'humid air' smell. I had noticed how humid it was during the descent as we got lower as the air-conditioning vents started blowing a little water vapor. With only one person out of 157 on board who had smelled this odor, I started wondering if he had food poisoning or a touch of the flu. He said that he didn't feel that it was food poisoning, but was feeling better and could perform his duties going home. I didn't feel comfortable with that, so I told the agent I needed to call crew schedule to get a replacement. A jump seating flight attendant in the gate area said he could work the flight, so it was arranged with the crew coordinator. I talked with all the crew members to see if they felt comfortable with going and they all did. On taxi out I asked the lead to check in the aft galley to see if she smelled anything. She said she just came from there and hadn't smelled anything at all. Once we reached our cruise altitude the recently added flight attendant came to the cockpit and said on taxi out he briefly smelled something like an exhaust smell 'like when you taxi behind another aircraft.' we had passed behind an aircraft entering the ramp area, but it was also about the time the APU would have shut down after the cooling cycle. I told him to write up exactly what he noticed in the flight attendant logbook. I thought maybe we do have some type of APU bleed duct problem, so I wasn't going to use the APU on arrival in dtw. The rest of the flight was uneventful until the top of descent into detroit. When leaving FL370 for FL330, the lead said they could smell something in the cabin. It got stronger a few seconds, then disappeared and was totally gone after a min. My first thought was to declare an emergency and divert into fwa. I decided not to however as: 1) the smell was gone, 2) it didn't seem to make any feel ill, and 3) I wasn't sure how long it would take to deplane in fwa at that time of night and I didn't want to have to use the chutes if I didn't have to. I was wondering what could cause a smell only in the descent. Also I thought of the high pressure bleeds opening at low power settings. Before our next descent, I had the first officer, who was flying the aircraft, go on oxygen just as a precaution. During our next descent to FL240, I watched the bleeds open and just as they did, a smell would materialize in the cabin for a few seconds, then dissipate and be totally gone within 1-2 mins even if the high pressure bleeds remained opened. I checked with the lead to see if anyone was experiencing any adverse effects from the smell and she said that everyone was fine and it seemed to be more of just a nuisance than anything. When we were cleared out of FL240, itold the first officer to try to keep the bleeds closed by keeping the power up. He did this and no smell ever developed. When we were cleared into the low altitude approach phase, we had to bring the thrust back and the high pressure bleeds opened. Once again the smell appeared strong for a few seconds, then disappeared. The high pressure bleeds remained open for the rest of the flight and the smell never occurred again. At the gate the high pressure bleed problem was noted in the aircraft logbook. My thoughts were to declare an emergency if at any time anyone on board developed a headache or had any type of burning sensation in the eyes or throat. I instructed the lead of this but the situation never developed into that scenario. As a precaution, I could have declared an emergency, but at the time it really didn't seem appropriate as the aircraft was working fine, we had no ECAM messages warning us of any faults, and all the passenger were well. Even the flight attendant who was feeling bad before said he was feeling a lot better and the odor wasn't affecting him at all. I'm still not totally sure that the incidents from the first flight X (dtw-mco) and the second flight Y (mco-dtw) are even related. I can't imagine how a high pressure bleed problem would only affect the aft galley on one flight and the whole aircraft on the next flight. Also the odor never caused any discomfort to anyone on the second flight and I only had one person feel ill on the first flight. It just seems a little suspicious, that is why I even mention it at all. Talking with our maintenance control the next day, they said they did several engine run-ups in which the high pressure bleeds were cycled and they could never duplicate any odors.

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Original NASA ASRS Text

Title: AN ACR MLG CAPT RPTS THAT HIS ACFT HAD A STRANGE ODOR ON DSCNT. THIS ODOR WAS NOT CONSTANT AND SEEMED TO BE RELATED TO CYCLING THE HIGH PRESSURE BLEEDS. ONE FLT ATTENDANT WAS INCAPACITATED WITH NAUSEA ON THE FIRST ENCOUNTER OF THE ODOR BUT WAS NOT AFFECTED ON THE SECOND ENCOUNTER.

Narrative: THE LEAD FLT ATTENDANT ADVISED ME THAT WE WOULD NEED A NEW PAX OXYGEN BOTTLE. SHE INFORMED ME THAT THE FLT ATTENDANT WORKING THE AFT GALLEY SAID HE SMELLED SOMETHING DURING THE FINAL PART OF OUR DSCNT THAT MADE HIM FEEL NAUSEOUS AND GAVE HIM A HEADACHE. HE ADMINISTERED HIMSELF OXYGEN AND THAT MADE HIM FEEL BETTER. THE OTHER FLT ATTENDANT WHO WAS WORKING THE AFT CABIN SAID SHE HAD A LITTLE HEADACHE, BUT DIDN'T SMELL ANYTHING UNUSUAL. WE ADVISED MAINT AND I DISCUSSED WHAT COULD CAUSE A SMELL IN JUST THE AFT GALLEY. THE FIRST THING THAT CAME TO MIND WAS SOME SORT OF APU BLEED DUCT MALFUNCTION. THE APU WASN'T ON DURING THE DSCNT, BUT WE DECIDED TO DISCONNECT THE EXTERNAL AIR-CONDITIONING UNIT AND RUN THE PACKS OFF THE APU TO SEE IF SOME SMELL DEVELOPED. NOTHING DID. WE NEXT DECIDED TO ASK THE PEOPLE WORKING IN THE AFT CARGO COMPARTMENT IF THEY HAD NOTICED ANY UNUSUAL SMELLS WHEN THEY OPENED THE CARGO COMPARTMENT -- ONCE AGAIN NOTHING NOTED. WITH THE AFT LAVS RIGHT NEXT TO THE GALLEY, I THOUGH MAYBE THE SMELL WAS COMING FROM THEM. SO WE ENSURED THE LAVS WERE SVCED AND THE TRASH FROM THE GALLEY EMPTIED. THE OVENS IN THE GALLEY WERE OFF AT THE TIME OF INCIDENT, SO THAT RULED OUT ANY TYPE OF ELECTRIC FUMES. THE FLT ATTENDANT SAID IT SMELLED JUST LIKE 'THIS.' BOTH THE MECH AND I AND THE OTHER FLT ATTENDANTS COULDN'T SMELL ANYTHING BUT THE OUTSIDE 'HUMID AIR' SMELL. I HAD NOTICED HOW HUMID IT WAS DURING THE DSCNT AS WE GOT LOWER AS THE AIR-CONDITIONING VENTS STARTED BLOWING A LITTLE WATER VAPOR. WITH ONLY ONE PERSON OUT OF 157 ON BOARD WHO HAD SMELLED THIS ODOR, I STARTED WONDERING IF HE HAD FOOD POISONING OR A TOUCH OF THE FLU. HE SAID THAT HE DIDN'T FEEL THAT IT WAS FOOD POISONING, BUT WAS FEELING BETTER AND COULD PERFORM HIS DUTIES GOING HOME. I DIDN'T FEEL COMFORTABLE WITH THAT, SO I TOLD THE AGENT I NEEDED TO CALL CREW SCHEDULE TO GET A REPLACEMENT. A JUMP SEATING FLT ATTENDANT IN THE GATE AREA SAID HE COULD WORK THE FLT, SO IT WAS ARRANGED WITH THE CREW COORDINATOR. I TALKED WITH ALL THE CREW MEMBERS TO SEE IF THEY FELT COMFORTABLE WITH GOING AND THEY ALL DID. ON TAXI OUT I ASKED THE LEAD TO CHK IN THE AFT GALLEY TO SEE IF SHE SMELLED ANYTHING. SHE SAID SHE JUST CAME FROM THERE AND HADN'T SMELLED ANYTHING AT ALL. ONCE WE REACHED OUR CRUISE ALT THE RECENTLY ADDED FLT ATTENDANT CAME TO THE COCKPIT AND SAID ON TAXI OUT HE BRIEFLY SMELLED SOMETHING LIKE AN EXHAUST SMELL 'LIKE WHEN YOU TAXI BEHIND ANOTHER ACFT.' WE HAD PASSED BEHIND AN ACFT ENTERING THE RAMP AREA, BUT IT WAS ALSO ABOUT THE TIME THE APU WOULD HAVE SHUT DOWN AFTER THE COOLING CYCLE. I TOLD HIM TO WRITE UP EXACTLY WHAT HE NOTICED IN THE FLT ATTENDANT LOGBOOK. I THOUGHT MAYBE WE DO HAVE SOME TYPE OF APU BLEED DUCT PROB, SO I WASN'T GOING TO USE THE APU ON ARR IN DTW. THE REST OF THE FLT WAS UNEVENTFUL UNTIL THE TOP OF DSCNT INTO DETROIT. WHEN LEAVING FL370 FOR FL330, THE LEAD SAID THEY COULD SMELL SOMETHING IN THE CABIN. IT GOT STRONGER A FEW SECONDS, THEN DISAPPEARED AND WAS TOTALLY GONE AFTER A MIN. MY FIRST THOUGHT WAS TO DECLARE AN EMER AND DIVERT INTO FWA. I DECIDED NOT TO HOWEVER AS: 1) THE SMELL WAS GONE, 2) IT DIDN'T SEEM TO MAKE ANY FEEL ILL, AND 3) I WASN'T SURE HOW LONG IT WOULD TAKE TO DEPLANE IN FWA AT THAT TIME OF NIGHT AND I DIDN'T WANT TO HAVE TO USE THE CHUTES IF I DIDN'T HAVE TO. I WAS WONDERING WHAT COULD CAUSE A SMELL ONLY IN THE DSCNT. ALSO I THOUGHT OF THE HIGH PRESSURE BLEEDS OPENING AT LOW PWR SETTINGS. BEFORE OUR NEXT DSCNT, I HAD THE FO, WHO WAS FLYING THE ACFT, GO ON OXYGEN JUST AS A PRECAUTION. DURING OUR NEXT DSCNT TO FL240, I WATCHED THE BLEEDS OPEN AND JUST AS THEY DID, A SMELL WOULD MATERIALIZE IN THE CABIN FOR A FEW SECONDS, THEN DISSIPATE AND BE TOTALLY GONE WITHIN 1-2 MINS EVEN IF THE HIGH PRESSURE BLEEDS REMAINED OPENED. I CHKED WITH THE LEAD TO SEE IF ANYONE WAS EXPERIENCING ANY ADVERSE EFFECTS FROM THE SMELL AND SHE SAID THAT EVERYONE WAS FINE AND IT SEEMED TO BE MORE OF JUST A NUISANCE THAN ANYTHING. WHEN WE WERE CLRED OUT OF FL240, ITOLD THE FO TO TRY TO KEEP THE BLEEDS CLOSED BY KEEPING THE PWR UP. HE DID THIS AND NO SMELL EVER DEVELOPED. WHEN WE WERE CLRED INTO THE LOW ALT APCH PHASE, WE HAD TO BRING THE THRUST BACK AND THE HIGH PRESSURE BLEEDS OPENED. ONCE AGAIN THE SMELL APPEARED STRONG FOR A FEW SECONDS, THEN DISAPPEARED. THE HIGH PRESSURE BLEEDS REMAINED OPEN FOR THE REST OF THE FLT AND THE SMELL NEVER OCCURRED AGAIN. AT THE GATE THE HIGH PRESSURE BLEED PROB WAS NOTED IN THE ACFT LOGBOOK. MY THOUGHTS WERE TO DECLARE AN EMER IF AT ANY TIME ANYONE ON BOARD DEVELOPED A HEADACHE OR HAD ANY TYPE OF BURNING SENSATION IN THE EYES OR THROAT. I INSTRUCTED THE LEAD OF THIS BUT THE SIT NEVER DEVELOPED INTO THAT SCENARIO. AS A PRECAUTION, I COULD HAVE DECLARED AN EMER, BUT AT THE TIME IT REALLY DIDN'T SEEM APPROPRIATE AS THE ACFT WAS WORKING FINE, WE HAD NO ECAM MESSAGES WARNING US OF ANY FAULTS, AND ALL THE PAX WERE WELL. EVEN THE FLT ATTENDANT WHO WAS FEELING BAD BEFORE SAID HE WAS FEELING A LOT BETTER AND THE ODOR WASN'T AFFECTING HIM AT ALL. I'M STILL NOT TOTALLY SURE THAT THE INCIDENTS FROM THE FIRST FLT X (DTW-MCO) AND THE SECOND FLT Y (MCO-DTW) ARE EVEN RELATED. I CAN'T IMAGINE HOW A HIGH PRESSURE BLEED PROB WOULD ONLY AFFECT THE AFT GALLEY ON ONE FLT AND THE WHOLE ACFT ON THE NEXT FLT. ALSO THE ODOR NEVER CAUSED ANY DISCOMFORT TO ANYONE ON THE SECOND FLT AND I ONLY HAD ONE PERSON FEEL ILL ON THE FIRST FLT. IT JUST SEEMS A LITTLE SUSPICIOUS, THAT IS WHY I EVEN MENTION IT AT ALL. TALKING WITH OUR MAINT CTL THE NEXT DAY, THEY SAID THEY DID SEVERAL ENG RUN-UPS IN WHICH THE HIGH PRESSURE BLEEDS WERE CYCLED AND THEY COULD NEVER DUPLICATE ANY ODORS.

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.