APCHING THE RWY IN ZZZ FOR DEP A BAE146 IS EVACED BECAUSE OF SMOKE AND FUMES IN THE CABIN DUE TO A HYD FAILURE.

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WE WERE TAXIING OUT FOR DEP FOR RWY 12L AND WERE #2 FOR DEP WITH OUR BEFORE TKOF CHKS COMPLETED; WHEN AS I CAME TO A STOP; OR HAD JUST STOPPED (I'M NOT SURE) THE FO AND I HEARD A 'PHOOSH' SOUND VERY LOUD IN THE CABIN. WE THEN LOOKED UP AT THE HYDS GAUGES AND NOTED THAT THE PRESSURE ON THE GREEN SIDE; AS WELL AS THE QUANTITY; WERE RAPIDLY DECREASING TO ZERO VALUES. SIMULTANEOUSLY; THE ASSOCIATED LOW PRESSURE; LOW QUANTITY AND AIR LOW PRESSURE LIGHTS AND 'PTU' KICKED IN AND WE HEARD A MAJORITY OF THE PAX SCREAMING 'SMOKE; FIRE' AND THE SOUND OF PEOPLE AND THE FLT ATTENDANTS MOVING AROUND AND SCURRYING. I KNEW THAT THIS MUST BE RELATED TO THE PREVIOUSLY MENTIONED 'PHOOSH' SOUND AND OUR HYD PROBS. I KNEW THAT 'SKYDROL' HYD FLUID IS CAUSTIC AND FLAMMABLE; THEREFORE I OPENED THE COCKPIT DOOR TO BETTER ASCERTAIN THE CIRCUMSTANCES AFTER I WAS UNABLE TO RAISE THE FORWARD FLT ATTENDANT ON THE INTERCOM. AMID THE PAX SCREAMS I HEARD THE FORWARD FLT ATTENDANT TELL ME THAT SMOKE AND FUMES WERE FILLING THE CABIN. BASED ON MY ASSESSMENT OF ALL THE CIRCUMSTANCES; I IMMEDIATELY CALLED AN EVAC OVER THE PA TELLING THE FLT ATTENDANTS TO EVAC THE PAX USING ALL DOORS. THE FLT ATTENDANTS IMMEDIATELY DEPLOYED THE SLIDES AND EVACED THE PAX. I THEN CALLED ATC TO ADVISE THEM OF THE EVAC AND WHERE. THE FLT ATTENDANTS BOTH DID AN EXCELLENT JOB WITH THEIR VERBAL COMMANDS AND THEIR CALMING AND SAFE EXIT OF THE PAX. THE FO COMPLETED HIS MEMORY ITEMS DUTIES QUICKLY; PERFECTLY AND WITHOUT ANY COACHING FROM ME. HE THEN DID AN EXEMPLARY JOB; ESPECIALLY FOR ONLY HAVING 2 DAYS OF LINE EXPERIENCE; OF GETTING OUT OF THE ACFT (ABOUT THE THIRD PERSON OUT) AND THEN ASSISTING ALL THE PAX DOWN THE SLIDE AND AWAY FROM THE ACFT TO THE DEICE PAD. AFTER ALL THE PEOPLE WERE OFF THE ACFT I NOTED NO SMOKE OR FIRE AND FINISHED THE QRH FOR THE EVAC. BY THIS TIME THE FIRE DEPT HAD SURROUNDED THE ACFT AND I HAD THEN EXITED THE ACFT USING SLIDE 1L. UPON EXITING THE ACFT I NOTED THAT ALL THE PAX HAD BEEN SAFELY SECURED AND GATHERED IN A LOCATION 1000 FT FROM THE ACFT SO I WALKED AROUND THE ACFT WITH THE CAPT OF THE FIRE DEPT AND NOTED HYD POOLS UNDER THE AFT CARGO BAY AND LNDG GEAR WELLS. SUPPLEMENTAL INFO FROM ACN 629810: I KNEW WE BLEW A HYD LINE AND IT SPRAYED THE FLUID IN THE CABIN. IF I HAD TO DO IT AGAIN I WOULD HAVE ASKED THE CAPT IF HE WANTED ME TO GO BACK AND CHK IT OUT. SINCE WE WERE ON THE GND; I DON'T THINK THERE WAS MUCH OF A SECURITY ISSUE AND WE COULD HAVE SENT ONE OF US BACK TO CHK IT OUT. THE CAPT BEING PIC HAS EVERY RIGHT TO EVAC IF HE FEELS IT'S NECESSARY. CALLBACK CONVERSATION WITH RPTR ON ACN 630125 REVEALED THE FOLLOWING INFO: THE HYD LINE THAT FAILED WAS UNDER 3000 LBS PRESSURE. IT SPLIT ABOUT 2-3