Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Flight Crew Diverted; General Declared Emergency
Aircraft
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.
[No substantive additional information was provided in the secondary narrative.]
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.