Narrative:

Climbing through 12000 ft on our way to FL200, the cabin altitude warning horn went off. Informed ord departure that we had a problem. Departure frequency asked us if we needed any help. I stated no, that we had a pressurization problem and we wanted to return to ord. We descended to 9000 ft and turned northeast. I then went to the abnormal procedures to troubleshoot problem. Both air conditioning packs were off. I turned them back on. Aircraft started to pressurize. I told the ATC controller that we had pressurization system under control and that we were continuing to sjc. I asked the flight attendant if any passenger were apprehensive with the situation. Flight attendant said 1 passenger smelled smoke. I figured it was when we turned packs back on. Reason the packs were off in the first place was, we were stuck in the left/K alley behind a B767 and were breathing their exhaust. First officer only had 65 hours in the aircraft and only 8 months in the company. I shall make a note that any time we turn a system off after the normal checklist is completed to doublechk system is set to normal before takeoff. Additional comment would be to put packs/bleeds on mechanical checklist.

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Original NASA ASRS Text

Title: ACR CREW NEGLECTS TO TURN ON PACKS AND FINDS ACFT UNPRESSURIZED CLBING THROUGH 12000 FT.

Narrative: CLBING THROUGH 12000 FT ON OUR WAY TO FL200, THE CABIN ALT WARNING HORN WENT OFF. INFORMED ORD DEP THAT WE HAD A PROB. DEP FREQ ASKED US IF WE NEEDED ANY HELP. I STATED NO, THAT WE HAD A PRESSURIZATION PROB AND WE WANTED TO RETURN TO ORD. WE DSNDED TO 9000 FT AND TURNED NE. I THEN WENT TO THE ABNORMAL PROCS TO TROUBLESHOOT PROB. BOTH AIR CONDITIONING PACKS WERE OFF. I TURNED THEM BACK ON. ACFT STARTED TO PRESSURIZE. I TOLD THE ATC CTLR THAT WE HAD PRESSURIZATION SYS UNDER CTL AND THAT WE WERE CONTINUING TO SJC. I ASKED THE FLT ATTENDANT IF ANY PAX WERE APPREHENSIVE WITH THE SIT. FLT ATTENDANT SAID 1 PAX SMELLED SMOKE. I FIGURED IT WAS WHEN WE TURNED PACKS BACK ON. REASON THE PACKS WERE OFF IN THE FIRST PLACE WAS, WE WERE STUCK IN THE L/K ALLEY BEHIND A B767 AND WERE BREATHING THEIR EXHAUST. FO ONLY HAD 65 HRS IN THE ACFT AND ONLY 8 MONTHS IN THE COMPANY. I SHALL MAKE A NOTE THAT ANY TIME WE TURN A SYS OFF AFTER THE NORMAL CHKLIST IS COMPLETED TO DOUBLECHK SYS IS SET TO NORMAL BEFORE TKOF. ADDITIONAL COMMENT WOULD BE TO PUT PACKS/BLEEDS ON MECHANICAL CHKLIST.

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.