Narrative:

Occurrence 20 NM east of bishop VOR at FL220. Cabin began to climb at 2500 FPM. We first suspected a pack or bleed problem but cabin broke 10000 ft MSL quickly. We had already requested FL200 as soon as the problem manifested itself. After red 'cabin altitude' light illuminated, captain went on oxygen first then, with the exchange of controls to captain, first officer went on oxygen. Communication was established. First officer then called back to flight attendant to tell her of situation. Captain declared emergency to ZOA. A full emergency descent was not commenced due to the vicinity of terrain. Captain descended aircraft to approximately 14000 ft MSL. First officer completed 'cabin altitude' emergency checklist, no change in situation occurred. The decision to continue to fresno at 16000 ft MSL was discussed by flight crew. Captain climbed and stayed at 16000 ft MSL to cross mountainous area for a duration of 18 mins. At that point cloud coverage dissipated and captain advised ATC that separation from terrain could be maintained and aircraft was descended to 10000 ft MSL. At that point crew removed oxygen masks and first officer resumed control of aircraft. Flight continued without incident to the landing at fresno. Emergency equipment was standing by but not used.

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Original NASA ASRS Text

Title: AN ACR FLC FLYING AN EMB120 EXPERIENCED A LOSS OF PRESSURIZATION AT FL220 NEAR BHI AND PERFORMED AN EMER DSCNT.

Narrative: OCCURRENCE 20 NM E OF BISHOP VOR AT FL220. CABIN BEGAN TO CLB AT 2500 FPM. WE FIRST SUSPECTED A PACK OR BLEED PROB BUT CABIN BROKE 10000 FT MSL QUICKLY. WE HAD ALREADY REQUESTED FL200 AS SOON AS THE PROB MANIFESTED ITSELF. AFTER RED 'CABIN ALT' LIGHT ILLUMINATED, CAPT WENT ON OXYGEN FIRST THEN, WITH THE EXCHANGE OF CTLS TO CAPT, FO WENT ON OXYGEN. COM WAS ESTABLISHED. FO THEN CALLED BACK TO FLT ATTENDANT TO TELL HER OF SIT. CAPT DECLARED EMER TO ZOA. A FULL EMER DSCNT WAS NOT COMMENCED DUE TO THE VICINITY OF TERRAIN. CAPT DSNDED ACFT TO APPROX 14000 FT MSL. FO COMPLETED 'CABIN ALT' EMER CHKLIST, NO CHANGE IN SIT OCCURRED. THE DECISION TO CONTINUE TO FRESNO AT 16000 FT MSL WAS DISCUSSED BY FLC. CAPT CLBED AND STAYED AT 16000 FT MSL TO CROSS MOUNTAINOUS AREA FOR A DURATION OF 18 MINS. AT THAT POINT CLOUD COVERAGE DISSIPATED AND CAPT ADVISED ATC THAT SEPARATION FROM TERRAIN COULD BE MAINTAINED AND ACFT WAS DSNDED TO 10000 FT MSL. AT THAT POINT CREW REMOVED OXYGEN MASKS AND FO RESUMED CTL OF ACFT. FLT CONTINUED WITHOUT INCIDENT TO THE LNDG AT FRESNO. EMER EQUIP WAS STANDING BY BUT NOT USED.

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.