Narrative:

This problem was caused by spilled hydraulic fluid draining from a small vent just in front of the APU intake. The copilot or I could not smell or see anything in the cockpit. After the flight attendant called and told me there was an odor and haze in the cabin, I looked back from the cockpit and could see a slight haze in the cabin. We had just started the APU and turned on the air conditioning packs. I shut the packs off and the flight attendant informed me the smoke detectors in the aft lavatory had sounded. I called for maintenance and the copilot told me of previous write-ups concerning air conditioning packs causing smoke. I saw no need to evacuate/evacuation, as there was a let up in the haze after shutdown of the packs. I told the flight attendant to open the rear doors to vent aircraft. The mechanic found hydraulic fluid dripping from a drain and being ingested into the APU. It was then shut down. Smoke/haze cleared and aircraft was dispatched APU inoperative. An extensive inspection was done to find source of hydraulic fluid, but no leaks found. Fluid probably spilled during previous maintenance on aircraft. Just after takeoff, the flight attendant informed me that the aft lavatory smoke detectors had sounded again, but no odor or haze or smoke was seen. This lasted only a min or so and stopped. I judged this to be only a small amount of hydraulic fluid residual in air conditioning system, and with no further problem, we proceeded to cvg. A single passenger was upset and wished to return to stl and land. The flight attendant explained the nature of the problem and that there was no danger.

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Original NASA ASRS Text

Title: AN ACR MLG HAD AIR CONDITIONING SMOKE IN THE CABIN ON THE GND.

Narrative: THIS PROB WAS CAUSED BY SPILLED HYD FLUID DRAINING FROM A SMALL VENT JUST IN FRONT OF THE APU INTAKE. THE COPLT OR I COULD NOT SMELL OR SEE ANYTHING IN THE COCKPIT. AFTER THE FLT ATTENDANT CALLED AND TOLD ME THERE WAS AN ODOR AND HAZE IN THE CABIN, I LOOKED BACK FROM THE COCKPIT AND COULD SEE A SLIGHT HAZE IN THE CABIN. WE HAD JUST STARTED THE APU AND TURNED ON THE AIR CONDITIONING PACKS. I SHUT THE PACKS OFF AND THE FLT ATTENDANT INFORMED ME THE SMOKE DETECTORS IN THE AFT LAVATORY HAD SOUNDED. I CALLED FOR MAINT AND THE COPLT TOLD ME OF PREVIOUS WRITE-UPS CONCERNING AIR CONDITIONING PACKS CAUSING SMOKE. I SAW NO NEED TO EVAC, AS THERE WAS A LET UP IN THE HAZE AFTER SHUTDOWN OF THE PACKS. I TOLD THE FLT ATTENDANT TO OPEN THE REAR DOORS TO VENT ACFT. THE MECH FOUND HYD FLUID DRIPPING FROM A DRAIN AND BEING INGESTED INTO THE APU. IT WAS THEN SHUT DOWN. SMOKE/HAZE CLRED AND ACFT WAS DISPATCHED APU INOP. AN EXTENSIVE INSPECTION WAS DONE TO FIND SOURCE OF HYD FLUID, BUT NO LEAKS FOUND. FLUID PROBABLY SPILLED DURING PREVIOUS MAINT ON ACFT. JUST AFTER TKOF, THE FLT ATTENDANT INFORMED ME THAT THE AFT LAVATORY SMOKE DETECTORS HAD SOUNDED AGAIN, BUT NO ODOR OR HAZE OR SMOKE WAS SEEN. THIS LASTED ONLY A MIN OR SO AND STOPPED. I JUDGED THIS TO BE ONLY A SMALL AMOUNT OF HYD FLUID RESIDUAL IN AIR CONDITIONING SYS, AND WITH NO FURTHER PROB, WE PROCEEDED TO CVG. A SINGLE PAX WAS UPSET AND WISHED TO RETURN TO STL AND LAND. THE FLT ATTENDANT EXPLAINED THE NATURE OF THE PROB AND THAT THERE WAS NO DANGER.

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.