What was found
EN ROUTE FROM ONT TO ILN, AIRCRAFT EXPERIENCED RAPID DECOMPRESSION AT 33.000 FT. CABIN CLIMED TO 20,000 FT IN APPROX 2 MIN. EXECUTED EMERGENCY DESCENT. PRESSURE WAS REGAINED AT APPROX 10,000 FT. FOUND DUCT CLAMP LOOSE AND DUCT SEPARATED. RECONNECTED DUCT AND RE-CONNECTED CLAMP. OPS CHECKED GOOD IAW DC8 MM.