CL65 CREW HAD A CABIN DECOMPRESSION AT FL280.

Narrative

ACFT WAS AT FL280 WHEN WE RECEIVED A CABIN ALT CAUTION MESSAGE. THE FO AND I DONNED OUR OXYGEN MASKS AND REQUESTED A LOWER ALT FROM ZDC. CTR TOLD US TO SWITCH TO ZID. WE DID THIS AND GOT A CLRNC TO FL180. WE NOW RECEIVED A CABIN ALT WARNING MESSAGE. THE ACFT WAS ON A FERRY PERMIT TO RETURN TO MAINT BASE; THEREFORE; WE ONLY HAD THE 2 PLTS AND 1 FLT ATTENDANT ON BOARD. SHE DONNED HER OXYGEN SEEING/HEARING US DO THE SAME. WE WERE FURTHER CLRED TO 10000 FT BY ZID. WE COULD DETECT NO STRUCTURAL DAMAGE AND AFTER CONSULTING OUR MAINT AND DISPATCH OFFICES; ELECTED TO CONTINUE TO OUR MAINT BASE. ALL CREW AND OFFICE/MAINT PERSONNEL BEING IN AGREEMENT THAT IT WAS SAFE TO DO SO; WE LANDED WITHOUT FURTHER COMPLICATIONS. MAINT FOUND A CRACK/RUPTURE IN DUCT WORK OF AN ACM. CONTRIBUTING FACTORS ARE CREW FERRYING ACFT AFTER CHIEF PLT CONVERSATION; ADDING STRESS TO THE SIT. COMPANY NOT CERTAIN THAT CREW SHOULD HAVE WRITTEN ACFT UP AT AN OUTSTATION. IT WAS OUR FIRST LEG OF DAY 2 ON A 4 DAY TRIP; SO WE HAD OUR FIRST PREFLT AT THE OUTSTATION. SOME STRESS ADDED DUE TO THE FACT OF POSSIBLE DISCIPLINARY ACTION UPON OUR RETURN. CREW FOUND A DISCREPANCY DURING PREFLT AND COMMUNICATED THIS TO MAINT CTL. THEY DECIDED THAT IT WAS NOT GOOD FOR REVENUE SVC; AND CHKED TO HAVE CREW FERRY ACFT HOME.