ACFT EQUIP PROB. LOST PRESSURIZATION DURING CLBOUT FROM ARPT. DECLARED EMER AND RETURNED TO DEP ARPT. CAPT WAS STILL ON HIGH MINIMUMS AND ARPT WX WAS BELOW HIS MINIMUMS.

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PASSING 12000 FT MSL; AUTO PRESSURIZATION FAILED CAUSING OUTFLOW VALVE TO DRIVE TO FULL OPEN POS CAUSING A RAPID DECOMPRESSION. MASTER WARNING ILLUMINATED ALONG WITH CABIN ALT ANNUNCIATOR. DONNED OXYGEN MASKS; PERFORMED EMER CHKLIST; RETURNED TO DSM. MADE UNEVENTFUL NORMAL LNDG AFTER DECLARING EMER DUE TO CAPT'S HIGH MINIMUMS OF 300 - 1 MI (LESS THAN 100 HRS IN TYPE). THIS WAS A MECHANICAL FAILURE. THERE IS NO WAY TO PREVENT THIS BECAUSE EVERY NOW AND THEN THINGS DO FAIL. BUT LOOKING BACK IN RETROSPECT IT'S INTERESTING TO NOTE MY MENTAL BEHAVIOR. AT FIRST; YOU SEE MASTER WARNING LIGHTS AND THE PRESSURE CHANGE IN THE COCKPIT. THE FIRST THING THAT CROSSES YOUR MIND FOR A SPLIT SECOND IS THE AIR OF CONFUSION UNTIL YOU FIGURE OUT EXACTLY WHAT'S GOING ON. THE MOST DIFFICULT PART OF THE FLT WAS TRYING TO SLOW MYSELF DOWN AND NOT TO RUSH. IN THAT SIT YOUR BRAIN IS THINKING SO FAST ON THINGS YOU NEED TO DO; WHO TO TALK TO; WHERE TO LAND; MAKE SURE THE COPLT IS DOING WHAT HE'S SUPPOSED TO; ETC. IT'S PHYSICALLY IMPOSSIBLE TO PERFORM THESE TASKS THAT FAST. SO WHAT I GUESS I SHOULD SAY IS THAT I RE-LEARNED THE IMPORTANCE OF NOT BEING RUSHED; TRY TO SLOW DOWN; ESPECIALLY IN AN EMER OR ABNORMAL SIT. BUT THEN AGAIN; EASIER SAID THAN DONE.