Narrative:

The takeoff and climb out were normal. During the later stages of climb I noticed that the cabin altitude was a little higher than normal (8;000 ft) but differential pressure was still increasing so I didn't think anything of it. As the flight progressed the first officer pointed out the cabin altitude was about 9;000 ft. I then asked ATC for a lower altitude and called the flight attendant and asked her to take her seat and informed her that we were having a pressurization problem and that the passenger O2 masks might have to be deployed. Next I made a PA to the passengers informing them of the problem and that we might have to deploy the O2 masks and that we were in a descent to a safe altitude. Shortly after we started the descent we came to the conclusion that we were not going to keep the cabin below 10;000 ft so I declared an emergency with ATC. We then slowed the aircraft to 250 KIAS and extended the landing gear. Though we had already donned our O2 masks I completed the rapid decompression QRH and the emergency descent checklist. At FL200 with the cabin altitude at 12;100 ft and climbing I instructed the first officer to deploy the passenger O2 masks. About three minutes later we leveled at 10;000 ft; slowed to 200 KTS and retracted the landing gear. I requested and was granted priority handling direct to our planned diversion airport. At this point I sent an ACARS message to dispatch letting them know what happened and advising of our plans to divert. I then made a PA to the passengers letting them know that we had leveled off at a safe altitude; that the O2 masks were no longer required; and that we had everything under control and would be diverting. Then subsequent landing was normal and we taxied to the gate.

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Original NASA ASRS Text

Title: An EMB 145 flight crew declared an emergency and descended below 10;000 MSL in response to a slow but steady increase in cabin altitude; ultimately reaching 12;100 FT at which point the O2 masks were manually deployed for the passengers. Upon leveling at 10;000 MSL the flight diverted to a nearby airport.

Narrative: The takeoff and climb out were normal. During the later stages of climb I noticed that the cabin altitude was a little higher than normal (8;000 FT) but differential pressure was still increasing so I didn't think anything of it. As the flight progressed the First Officer pointed out the cabin altitude was about 9;000 FT. I then asked ATC for a lower altitude and called the Flight Attendant and asked her to take her seat and informed her that we were having a pressurization problem and that the passenger O2 masks might have to be deployed. Next I made a PA to the passengers informing them of the problem and that we might have to deploy the O2 masks and that we were in a descent to a safe altitude. Shortly after we started the descent we came to the conclusion that we were not going to keep the cabin below 10;000 FT so I declared an emergency with ATC. We then slowed the aircraft to 250 KIAS and extended the landing gear. Though we had already donned our O2 masks I completed the rapid decompression QRH and the Emergency Descent checklist. At FL200 with the Cabin Altitude at 12;100 FT and climbing I instructed the First Officer to deploy the Passenger O2 masks. About three minutes later we leveled at 10;000 FT; slowed to 200 KTS and retracted the landing gear. I requested and was granted priority handling direct to our planned diversion airport. At this point I sent an ACARS message to Dispatch letting them know what happened and advising of our plans to divert. I then made a PA to the passengers letting them know that we had leveled off at a safe altitude; that the O2 masks were no longer required; and that we had everything under control and would be diverting. Then subsequent landing was normal and we taxied to the gate.

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.