A CRJ200 ON CLBOUT AT 6000 FT. WHEN THE PNEUMATIC BLEEDS WERE SWITCHED FROM AUX POWER UNIT TO ENGS; A STRONG ODOR AND HAZE FILLED THE CABIN AND COCKPIT. DIVERTED TO DEP ARPT.

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ON CLBOUT WE TRANSFERRED THE BLEEDS PER THE CLB CHKLIST. UPON TRANSFER; AN UNFAMILIAR ODOR; ACRID IN NATURE; BEGAN AND QUICKLY INTENSIFIED. UPON CALLING THE FLT ATTENDANT IN THE BACK; IT WAS DISCOVERED THAT THE ODOR WAS VERY STRONG AS WELL AND A HAZE HAD DEVELOPED. THE DECISION WAS MADE TO RETURN TO ZZZ. AN EMER WAS NOT DECLARED ALTHOUGH A PRECAUTIONARY LNDG WAS PERFORMED AND THE CFR TRUCKS ACTIVATED. UPON LNDG; WE TAXIED OFF THE RWY AND STOPPED ON THE TXWY. CFR PERSONNEL BOARDED THE ACFT TO SEARCH FOR POSSIBLE FIRE. ODOR WAS STILL VERY STRONG AND THE CFR PEOPLE ALL SMELLED IT; TOO. NO FIRE WAS DETECTED AND THE PAX WERE DEPLANED ON THE TXWY. MANY WERE CHKED OUT BY MEDICAL PERSONNEL. THE PAX WERE THEN BUSSED TO THE TERMINAL AND THE CREW STAYED WITH THE ACFT WHILE IT WAS TOWED TO THE REMOTE PARKING AREA. THE ACFT WAS PUT BACK IN SVC JUST BEFORE WE TOOK IT OVER FOR THIS FLT. IT HAD COME FROM MAINT WHERE HYDRAULIC PROBS HAD BEEN FIXED. THE MAINT PERSONNEL THAT INSPECTED THE ACFT AFTER OUR LNDG SAW THAT IT WAS WET UNDER THE HYDRAULIC RESERVOIR #1. IT IS BELIEVED; AT THIS POINT; THAT WE ALL INHALED AND HAVE BEEN AFFECTED BY SKYDROL HYDRAULIC FLUID. THE FLT ATTENDANT IS COUGHING AND LOST HER VOICE. THE CAPT AND MYSELF WILL GET CHKED OUT FOR EXPOSURE TO SKYDROL.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: A VERY ACRID ODOR WAS EXPERIENCED AFTER SWITCHING PNEUMATIC BLEED FROM THE AUX POWER UNIT TO THE ENG BLEED SYSTEM. CABIN ATTENDANT REPORTED ODOR VERY STRONG AND A HAZE HAD FILLED THE CABIN. THE FLT WAS DIVERTED TO THE DEP STATION AND MET BY CFR. ON THE GND; THE ODOR WAS STILL PRESENT.