Narrative:

Before takeoff; pressurization was set at FL360. We only climbed to FL220; turbulence related. I reset mode control to FL220; then descended to FL200 because of turbulence. After a smooth ride; higher was reported smooth. I reset mode control to FL360 and climbed. We were cleared to FL340. Going through FL300 we got the altitude warning horn. We proceeded with oxygen masks on and 100% and crew communications. I was able to talk to ATC but not with the captain. My own error; but we still descended down to FL200 and the cabin pressure stabilized nicely descending through FL240. We came to the conclusion the cabin couldn't keep up with all the flight level changes and decided cautiously to try to climb again. Unfortunately; the cabin started to climb at a non-standard rate so we stopped our climb without event and diverted. When the cabin altitude horn sounded; the cabin altitude was 10;500'. Although the captain and I had our masks on; the passenger cabin masks never dropped and no one was alarmed at any time in back. We both agreed later the new briefing about the warning horn sounding in the air was a positive factor; and thus we recognized and reacted in a more timely matter. I think there should be a note under crew communications. Use flight intercom to establish communications. From talking to other pilots; I'm not the first first officer to miss that in the heat of battle. The captains are used to talking on the flight intercom all the time. The first officer rarely uses the intercom. Afterwards; you say of course you would; but it's not instinct.

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Original NASA ASRS Text

Title: B737 flight crew experiences cabin altitude warning horn climbing through FL300. Cabin altitude stabilizes nicely descending through FL240 for FL200 although a diversion is deemed necessary for fuel considerations. The First Officer experienced difficulty using the interphone and the Captain had difficulties with glasses and the headset.

Narrative: Before takeoff; pressurization was set at FL360. We only climbed to FL220; turbulence related. I reset mode control to FL220; then descended to FL200 because of turbulence. After a smooth ride; higher was reported smooth. I reset mode control to FL360 and climbed. We were cleared to FL340. Going through FL300 we got the altitude warning horn. We proceeded with oxygen masks on and 100% and Crew communications. I was able to talk to ATC but not with the Captain. My own error; but we still descended down to FL200 and the cabin pressure stabilized nicely descending through FL240. We came to the conclusion the cabin couldn't keep up with all the flight level changes and decided cautiously to try to climb again. Unfortunately; the cabin started to climb at a non-standard rate so we stopped our climb without event and diverted. When the cabin altitude horn sounded; the cabin altitude was 10;500'. Although the Captain and I had our masks on; the Passenger cabin masks never dropped and no one was alarmed at any time in back. We both agreed later the new briefing about the warning horn sounding in the air was a positive factor; and thus we recognized and reacted in a more timely matter. I think there should be a note under Crew communications. Use flight intercom to establish communications. From talking to other Pilots; I'm not the first First Officer to miss that in the heat of battle. The Captains are used to talking on the flight intercom all the time. The First Officer rarely uses the intercom. Afterwards; you say of course you would; but it's not instinct.

Data retrieved from NASA's ASRS site as of April 2012 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.