AN CRJ700 DUCT MONITORING WARNING SYSTEM CLOSED ALL BLEEDS CAUSING THE ACFT TO DEPRESSURIZED. ACFT RETURNED TO LAND.

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CLBING THROUGH FL220 FOR FL230 WE RECEIVED BLEED AIR DUCT WARNING. CALLED FOR QRH; AT SAME TIME I SAW THAT WE WERE DEPRESSURIZING BECAUSE ALL BLEED AIR VALVES CLOSED ON US. AS WE DID CHKLIST I ASK FOR DSCNT TO 10000 FT AND DECLARED EMER. AT THE POINT IN CHKLIST TO LAND AT SUITABLE ARPT WE DECIDED ZZZ1 AT FIRST BECAUSE IT WAS 20 MI AWAY. AT THAT INSTANCE THE WARNING WENT AWAY; AND WE WERE ALREADY THROUGH 15000 FT GOING TO 10000 FT. CABIN ALT WAS SHOWING 5500 FT AND CLBING. WE TALKED TO THE FLT ATTENDANTS LET THEM KNOW WHAT WAS GOING ON. WE LEVELED AT 10000 FT AND THE CABIN WAS AT 7500 FT AND CLBING. WE THEN WENT TO 8000 FT AND THE CABIN MET OUR ALT. WE CONTACTED DISPATCH AND MAINT; TOLD THEM WHAT WAS GOING ON AND THAT THE MESSAGE WENT AWAY. WE DECIDED TO GO BACK TO ZZZ UNPRESSURIZED. AS WE DSNDED TO 4000 FT CAS MESSAGE L DUCT MON CAUTION CAME UP. WE RAN THE QRH; BUT AT THIS POINT WE WERE ALREADY UNPRESSURIZED AND CHKLIST WAS OF NO HELP. WE COULD NOT GET ANY OF THE BLEED VALVES TO OPEN. WE MADE A SHALLOW DESCENT TO THE ZZZ ARPT AND SHOT THE VISUAL. THEN WE SAW THAT WE HAD NO MORE WARNINGS AND WE DSNDED TO AND BELOW 10000 FT BEFORE THE CABIN PRESSURE WAS ABOVE 8000 FT. WE CANCELED OUR EMER WITH ATC. DUCT MON WARNING SHUT THE BLEED AIR VALVES DOWN AND WE COULD NOT GET THEM TO RE OPEN.