Narrative:

On climb out in the mid-teen altitudes, a horn went off in the cockpit. I was the PF and was concentrating on the departure, hand flying the aircraft at the time. I did not equate the horn sound with a cabin pressure problem. In fact, my immediate thought was that there was a landing gear malfunction. We scanned the cockpit, did not see any lights or obvious malfunction and I continued flying while the captain continued searching for the problem. At some point, the master caution illuminated, the overhead light illuminated and we saw the passenger oxygen mask light on. We saw that the cabin altitude was too high and I went to packs high and manual pressurization. Cabin altitude came down and we decided after referencing the procedures to try alternate controller and selected it. It seemed to hold fine. Due to the few passenger with plenty of spare oxygen masks, and after calculating fuel for a lower altitude, we elected to continue to ZZZ1. I am a 'touch' kind of person when it comes to checklists, and I was sure at the time I had reset the packs to on after starting the engines. I don't recall and distrs during the checklist. I did not notice them out of the on position prior to takeoff. As the PF, I also did not look up at the cabin altitude gauge or the flow gauge to doublechk it. I personally did not notice the cabin altitude climbing (ears popping) and did not equate the horn when it went off to a pressurization problem.

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Original NASA ASRS Text

Title: A B737-300 IN CLB EXCEEDED CABIN PRESSURE ALT AND PAX OXYGEN MASKS WERE DEPLOYED. CAUSED BY AIR CONDITIONING PACKS NOT SWITCHED ON.

Narrative: ON CLBOUT IN THE MID-TEEN ALTS, A HORN WENT OFF IN THE COCKPIT. I WAS THE PF AND WAS CONCENTRATING ON THE DEP, HAND FLYING THE ACFT AT THE TIME. I DID NOT EQUATE THE HORN SOUND WITH A CABIN PRESSURE PROB. IN FACT, MY IMMEDIATE THOUGHT WAS THAT THERE WAS A LNDG GEAR MALFUNCTION. WE SCANNED THE COCKPIT, DID NOT SEE ANY LIGHTS OR OBVIOUS MALFUNCTION AND I CONTINUED FLYING WHILE THE CAPT CONTINUED SEARCHING FOR THE PROB. AT SOME POINT, THE MASTER CAUTION ILLUMINATED, THE OVERHEAD LIGHT ILLUMINATED AND WE SAW THE PAX OXYGEN MASK LIGHT ON. WE SAW THAT THE CABIN ALT WAS TOO HIGH AND I WENT TO PACKS HIGH AND MANUAL PRESSURIZATION. CABIN ALT CAME DOWN AND WE DECIDED AFTER REFING THE PROCS TO TRY ALTERNATE CONTROLLER AND SELECTED IT. IT SEEMED TO HOLD FINE. DUE TO THE FEW PAX WITH PLENTY OF SPARE OXYGEN MASKS, AND AFTER CALCULATING FUEL FOR A LOWER ALT, WE ELECTED TO CONTINUE TO ZZZ1. I AM A 'TOUCH' KIND OF PERSON WHEN IT COMES TO CHKLISTS, AND I WAS SURE AT THE TIME I HAD RESET THE PACKS TO ON AFTER STARTING THE ENGS. I DON'T RECALL AND DISTRS DURING THE CHKLIST. I DID NOT NOTICE THEM OUT OF THE ON POS PRIOR TO TKOF. AS THE PF, I ALSO DID NOT LOOK UP AT THE CABIN ALT GAUGE OR THE FLOW GAUGE TO DOUBLECHK IT. I PERSONALLY DID NOT NOTICE THE CABIN ALT CLBING (EARS POPPING) AND DID NOT EQUATE THE HORN WHEN IT WENT OFF TO A PRESSURIZATION PROB.

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.