What was found
CLIMBING THROUGH 13000', THE CAPTAIN NOTICED THE CAB ALT READ 9900', IT HAD TURNED AMBER. HE SLOWED THE ASCENT AND CHECKED THE CONFIGURATION OF THE PRESSURIZATION SYSTEM AND THE BLEEDS AND PACKS. FOUND THE CONFIGURATION OF THE AIRCRAFT TO BE SET PROPERLY FOR AUTO PRESSURIZATION WITH THE BLEEDS AND PACKS SET FOR FLIGHT. THERE WERE NO CAS MESSAGES PRESENT. ATC WAS ASKED FOR AN IMMEDIATE DESCENT DUE TO A PRESSURIZATION ISSUE. THE CAB ALT WAS NOW AT 13500'. THE CREW DECLARED AN EMERGENCY AND BEGAN AN IMMEDIATE DESCENT TO 10000'. THEY LANDED WITHOUT INCIDENT. MAINTENANCE COMPLIED WITH ALL CHECKS THAT RECOMMENDED (INCLUDING OUTFLOW CHECKS AND AIRCRAFT PRESSURIZATION LEAK RATE CHECK). ALL OPS CHECKS WERE OK.