B737-300 flight crew reports a cabin altitude warning horn descending through FL220. Masks are donne...

Narrative:

While descending through 22;000 feet; we got the cabin altitude warning horn. Captain called to don our masks. We complied with the emergency action items. Looking at the cabin altitude; it showed below 10;000 ft (9;500 ft). I had looked at it just as we started the descent out of 24;000 ft and it was at 5;400 ft; which seemed where it should be for the landing altitude. I asked for an immediate descent and re-clarified an emergency descent. After about 30-60 seconds; the horn was out and the cabin was below 8;000 ft. The whole time the cabin was descending. We told the controller we had a pressurization issue but it was under control. We were now at 13;000 ft MSL. Communication was difficult at first as I had not gone to the mask position [on the comm panel] and the captain wasn't hitting the interphone button to talk. We thought it odd that we felt no pressure spike in our ears. I think after a long day and 12 years at another carrier with the full masks that go to mask [mic] automatically; I forgot to go to mask at first (5 seconds).

Original NASA ASRS Text

Title: B737-300 Flight Crew reports a cabin altitude warning horn descending through FL220. Masks are donned and communications established; with difficulty. The cabin is quickly below 10;000 feet and the flight continues to destination. The aircraft had been dispatched with a single pack.

Narrative: While descending through 22;000 feet; we got the Cabin Altitude Warning horn. Captain called to don our masks. We complied with the emergency action Items. Looking at the cabin altitude; it showed below 10;000 FT (9;500 FT). I had looked at it just as we started the descent out of 24;000 FT and it was at 5;400 FT; which seemed where it should be for the landing altitude. I asked for an immediate descent and re-clarified an emergency descent. After about 30-60 seconds; the horn was out and the cabin was below 8;000 FT. The whole time the cabin was descending. We told the Controller we had a pressurization issue but it was under control. We were now at 13;000 FT MSL. Communication was difficult at first as I had not gone to the mask position [on the comm panel] and the Captain wasn't hitting the interphone button to talk. We thought it odd that we felt no pressure spike in our ears. I think after a long day and 12 years at another carrier with the full masks that go to mask [mic] automatically; I forgot to go to mask at first (5 seconds).

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.

Attributes
ACN	1053088
Time
Date	201212
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Component
Aircraft Component	Pressurization System
Person 1
Function	First Officer
Experience	Flight Crew Last 90 Days 167
Person 2
Function	Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 163 Flight Crew Type 15000
Events
Anomaly	Aircraft Equipment Problem Critical

B737-300 flight crew reports a cabin altitude warning horn descending through FL220. Masks are donned and communications established; with difficulty. The cabin is quickly below 10;000 feet and the flight continues to destination. The aircraft had been dispatched with a single pack.