CARJ FLT CREW MAKE AN EMER DSCNT FROM FL380 WHEN PRESSURIZATION SAFETY VALVES FAIL IN THE OPEN POS.

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WE WERE PROCEEDING WESTWARD AT FL380. APPROX 100 MI E OF THE ZZZ1 VOR; THE EVENT OCCURRED. AT THIS TIME THE CREW EXPERIENCED A PRESSURE BUMP; AND NOTICED A RAPID RISE IN CABIN PRESSURE; FOLLOWED BY A 'CABIN PRESSURE' CAUTION; AND FINALLY A RED 'CABIN ALT' WARNING. AN EMER WAS DECLARED AND A LOWER ALT OF X FT WAS REQUESTED AND GRANTED. EMER DSCNT MEMORY ITEMS AND CHKLISTS WERE PERFORMED WHILE IN THE DSCNT. AFTER THESE TASKS WERE COMPLETED THE FLT DECK CREW NOTIFIED THE FLT ATTENDANTS ABOUT THE PRESSURIZATION PROB AND ASKED ABOUT THEIR CONDITION AND THE CONDITION OF THE PAX. THE CABIN CREW INDICATED THAT ALL WAS WELL UNDER THE CIRCUMSTANCES. THE FLT LEVELED OUT AT X FT APPROX 50 MI E OF THE ZZZ1 VOR. AT THAT TIME; ATC ASKED IF ANY ASSISTANCE WAS REQUIRED. WE THEN CALLED THE CABIN CREW AND REQUESTED A 'WALK-THROUGH' TO DETERMINE IF ANY MEDICAL ASSISTANCE WOULD BE REQUIRED UPON ARR AT ZZZ2. THE CABIN CREW CALLED AND STATED THAT NO MEDICAL ATTN WAS NEEDED. WITH THIS INFO; ATC WAS NOTIFIED THAT FURTHER ASSISTANCE WOULD NOT BE NEEDED. AT THIS TIME THE CAPT MADE A PA ANNOUNCEMENT EXPLAINING WHAT HAD HAPPENED AND WHY PROCS WERE FOLLOWED DURING THE EVENT. WE REMINDED THE PAX ONCE AGAIN THAT MEDICAL ASSISTANCE WAS AVAILABLE AT ZZZ2 IF NEEDED. ALSO; DURING THIS TIME THE FO WAS CONTACTING DISPATCH/MAINT AND INFORMING THEM OF OUR CONDITION AND TO UPDATE THE X STATION OF OUR STATUS AND HAVE A PAX SVC REPRESENTATIVE THERE TO MEET US. THE FLT CONTINUED ON TO ZZZ2 AND LANDED WITHOUT INCIDENT. SUPPLEMENTAL INFO FROM ACN 696488: AT THE GATE AT ZZZ2 WE CALLED MAINT. SAFETY VALVE #1 AND VALVE #2 HAD FLAGS SHOWING FAILED OPEN. LCL MAINT DEFERRED THE PRESSURIZATION SYS. WE RETURNED TO ZZZ1 UNPRESSURIZED WITH PACKS AT 9000 FT.