B737-300 SUFFERS PRESSURIZATION FAILURE AT FL360. PERFORMANCE OF EMERGENCY DESCENT PROCEDURE IS FLAWED WHEN CAPT TURNS PACKS OFF VICE HIGH AS DIRECTED BY QRH. SUBSEQUENTLY OVER PRESSURIZE THE CABIN AND; AFTER LNDG; MUST PARK AND BLEED OFF PRESSURE PRIOR TO OPENING DOORS.

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LEVEL AT FL360 DURING CRUISE AND SOME 40-50 MINS OF FLT; THE INTERMITTENT WARNING HORN FOR CABIN ABOVE 10000 FT WENT OFF. MY FO THOUGHT WE MIGHT HAVE A GEAR HORN; BUT HE NOTICED ME PERFORMING EMER ACTION ITEMS FOR LOSS OF PRESSURE AND DURING WHICH I SHOWED HIM THE CABIN ALT; HE THEN QUICKLY FOLLOWED SUIT. QRH PROCS WERE STARTED; ATC WAS INFORMED THAT WE NEEDED EMER DSCNT FOR A PRESSURIZATION PROB. I'M DOING THE QRH AND TAKING THE PACKS TO HIGH; I SHOWED AND PHYSICALLY TOUCHED MY FO TO LOOK AT MY ACTIONS. QRH TO THE LINE WE NOTED THE CABIN COMING BACK AND BELOW 10000 FT THEN 9000 FT. I SUGGESTED TO THE FO TO STOW SPD BRAKES SO AS NOT TO ALARM PAX AND SHOWED HIM THE CABIN OK. DURING THE CONTINUED DSCNT; A MASTER CAUTION FOR OVERHEAD WENT OFF. LOOKING UP; WE NOTICED PAX OXYGEN DEPLOYED. PRIOR TO THE MASTER CAUTION AND DURING DSCNT; I WAS RE-DOING MY QRH STEPS AND NOTICED I HAD PUT THE PACKS TO OFF AND NOT HIGH. FINDING THIS PROB; THEY WERE PUT TO THE CORRECT POS AS PER QRH. IT WAS BOTH OUR RECOLLECTIONS THAT WE CAUGHT THE ERROR PRIOR TO PAX OXYGEN MASKS DEPLOYING. WE THEN RE-COMMENCED OUR FULL EMER DSCNT. ATC DID NOT MOVE TFC FOR US; WE WERE GIVEN UP TO 3 HDG CHANGES; AND SMALL ALT CHANGES UNTIL AREA WAS CLR FOR OUR DSCNT. AROUND 12000-10000 FT; MASSIVE CABIN PRESSURE BUMPS AND EARS POPPING; I NOTICED CABIN AT 24 AND DIFFERENTIAL AT 8.65. I STATED TO THE FO 'WE GOT TO GET THIS ACFT LOWER' AND I TOOK MY ATTN TO ACFT AND QRH. MY FO TOOK THIS LITERALLY AND GOT US 6000 FT THEN 5000 FT APPROVED BY ATC. LEVEL AT 5000 FT; EARS AND PRESSURE NORMAL. WE DECIDED MEA; MOCA ALL OK; ACFT WORKING GOOD; LET'S STAY HERE (DON'T CHANGE WHAT WORKS). PROBS GETTING COMPANY AND MAINT; THEN SOLVED; RETURNED TO ZZZ. AFTER LNDG; ACFT STILL PRESSURIZED FOR SAFETY; WENT TO AN AREA WELL CLR OF TERMINAL. BRIEFED FLT ATTENDANT NOT TO TOUCH DOORS TO KEEP ALL SAFE; PARKED; USED MAINT AND DEPRESSURIZED ACFT. ALL OK. TOOK PAX TO GATE.