Narrative:

During cruise the baggage door seal cas message illuminated. Followed checklist and situation was normal per message. (Cabin altitude maintained, ok.) we were experiencing some turbulence and asked ATC for lower to FL370. It was reported as smooth. We were approximately 100 mi from top of descent. Anyways, as soon as I reduced power for descent, the cabin began to climb at a rate of approximately 2000 FPM. Soon followed the baggage, altitude cas message. We isolated the baggage compartment immediately per checklist. However, the cabin continued to climb and we continued to descend, asking for lower. I believe ATC cleared us to FL330. Shortly, the cabin altitude 'amber cas' message illuminated. We both put on our oxygen masks. We let ATC know of our pressurization problem and asked for lower. ATC cleared us FL240. Since the cabin continued to climb, I had the first officer brief the passenger on our situation and to keep them calm. It wasn't long and the cabin altitude 'red cas' message illuminated. We were approximately around FL310. I initiated a more aggressive descent per emergency descent profile. ATC was not accommodating our lower altitude request (due to military airspace). So we immediately declared an emergency. We briefly paused our descent at FL240 and then were cleared to 13000 ft. As I flew the descent profile, the first officer kept the passenger informed and ran the appropriate checklists. Once we got to approximately 14500 ft (cabin maximum altitude) the cabin altitude descended as we descended. Since we were cleared to 13000 ft we leveled off there momentarily and then stepped down slowly to 10000 ft. We informed ATC that things were under control and could continue to our destination of ZZZ. Please note: the aircraft sat outside in ZZZ1 the evening before in extremely heavy rain.

Related reports:

Google
 

Original NASA ASRS Text

Title: EMER DECLARED AND REQUEST MADE FOR EMER DSCNT WHEN THE CABIN PRESSURE SYS FAILS ON A CPR C750 AFTER START OF DSCNT ON FREQ WITH ZZZ CTR.

Narrative: DURING CRUISE THE BAGGAGE DOOR SEAL CAS MESSAGE ILLUMINATED. FOLLOWED CHKLIST AND SIT WAS NORMAL PER MESSAGE. (CABIN ALT MAINTAINED, OK.) WE WERE EXPERIENCING SOME TURB AND ASKED ATC FOR LOWER TO FL370. IT WAS RPTED AS SMOOTH. WE WERE APPROX 100 MI FROM TOP OF DSCNT. ANYWAYS, AS SOON AS I REDUCED PWR FOR DSCNT, THE CABIN BEGAN TO CLB AT A RATE OF APPROX 2000 FPM. SOON FOLLOWED THE BAGGAGE, ALT CAS MESSAGE. WE ISOLATED THE BAGGAGE COMPARTMENT IMMEDIATELY PER CHKLIST. HOWEVER, THE CABIN CONTINUED TO CLB AND WE CONTINUED TO DSND, ASKING FOR LOWER. I BELIEVE ATC CLRED US TO FL330. SHORTLY, THE CABIN ALT 'AMBER CAS' MESSAGE ILLUMINATED. WE BOTH PUT ON OUR OXYGEN MASKS. WE LET ATC KNOW OF OUR PRESSURIZATION PROB AND ASKED FOR LOWER. ATC CLRED US FL240. SINCE THE CABIN CONTINUED TO CLB, I HAD THE FO BRIEF THE PAX ON OUR SIT AND TO KEEP THEM CALM. IT WASN'T LONG AND THE CABIN ALT 'RED CAS' MESSAGE ILLUMINATED. WE WERE APPROX AROUND FL310. I INITIATED A MORE AGGRESSIVE DSCNT PER EMER DSCNT PROFILE. ATC WAS NOT ACCOMMODATING OUR LOWER ALT REQUEST (DUE TO MIL AIRSPACE). SO WE IMMEDIATELY DECLARED AN EMER. WE BRIEFLY PAUSED OUR DSCNT AT FL240 AND THEN WERE CLRED TO 13000 FT. AS I FLEW THE DSCNT PROFILE, THE FO KEPT THE PAX INFORMED AND RAN THE APPROPRIATE CHKLISTS. ONCE WE GOT TO APPROX 14500 FT (CABIN MAX ALT) THE CABIN ALT DSNDED AS WE DSNDED. SINCE WE WERE CLRED TO 13000 FT WE LEVELED OFF THERE MOMENTARILY AND THEN STEPPED DOWN SLOWLY TO 10000 FT. WE INFORMED ATC THAT THINGS WERE UNDER CTL AND COULD CONTINUE TO OUR DEST OF ZZZ. PLEASE NOTE: THE ACFT SAT OUTSIDE IN ZZZ1 THE EVENING BEFORE IN EXTREMELY HVY RAIN.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.