A306 CREW EXPERIENCED LOSS OF CABIN PRESSURE AT FL350.

Narrative

ORD-SMF. APPROX XA15Z; 130 NM SE OF BIS AT FL350. FO WAS OUT OF SEAT USING FACILITIES. CAPT HAD MASK ON. CABIN ALT WARNING HORN STARTED BEEPING. CABIN ALT WAS ABOVE 10000 FT AND CLBING. ASKED FOR AND RECEIVED CLRNC FOR DSCNT. FO CAME TO COCKPIT IMMEDIATELY AND DONNED MASK. RAN QRC CHKLIST IN DSCNT. COULD NOT CTL CABIN ALT. CABIN CLBED PAST 12000 FT WITH PACKS ON HIGH AND OUTFLOW VALVE FULLY CLOSED. AT APPROX 13000 FT ACFT ALT; CABIN ALT STARTED TO RESPOND. LEVELED OFF 12000 FT ACFT ALT WITH CABIN BELOW 10000 FT. (DURING DSCNT; COORDINATED WITH ATC NUMEROUS TIMES FOR TERRAIN AVOIDANCE.) ONCE CABIN UNDER CTL; CALLED MAINT AND DISPATCH THROUGH COMMERCIAL RADIO (CONFERENCE CALL). ELECTED TO DIVERT TO GFK. WX; RWY AND MONITORED ILS MAJOR REASON FOR GFK. UNEVENTFUL LNDG. NO INJURIES; NO MASKS DEPLOYED AND NO OVERWT LNDG. DISCOVERED SILVER CLOTH JAMMED AND EXITING THE ACFT FROM THE OUTFLOW VALVE DURING POSTFLT INSPECTION. DEPRESSURIZATION VERY GRADUAL -- HORN WAS FIRST INDICATION. NOTHING FELT IN EARS.