Narrative:

Shortly after takeoff; unusual smoke and odor came through wemac vents with the APU off. Notified ATC of problem and elected to return to our departure airport. Leveled off aircraft and smoke seemed to stop. Pilot not flying had time to run part of checklist; shut off left bleed source which seemed to stop odor. [We] landed without further event.

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Original NASA ASRS Text

Title: A Citation flight crew returned to their departure airport after unusual smoke and odors were detected emanating from the air conditioning vents.

Narrative: Shortly after takeoff; unusual smoke and odor came through WEMAC vents with the APU off. Notified ATC of problem and elected to return to our departure airport. Leveled off aircraft and smoke seemed to stop. Pilot not flying had time to run part of checklist; shut off left bleed source which seemed to stop odor. [We] landed without further event.

Data retrieved from NASA's ASRS site as of July 2013 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.