What was found
CABIN PRESSURE ALERT LEVEL 3 ILLUMINATED WITH AURAL ALERT. OXYGEN MASK ON AND CABIN ALTITUDE STILL CLIMBING, STARTED AN EMERGENCY DECENT. AT ABOUT FL 190, CABIN ALTITUDE WENT BELOW 10,000 FT, CONTINUED DECENT TO 12,000 FT. CABIN ALTITUDE STABILIZED ARROUND 4000 FT CONTINUED. FOUND CAC DOOR NOT CLOSED PROPERLY. DOOR WAS COCKED TO THE LEFT SIDE WITH RIGHT SIDE SEAL OUTSIDE OF FUSELAGE AND GAP LARGE ENOUGH TO INSERT HAND. PERFORMED GVI OF DOOR AND LATCH. NO DEFECTS FOUND. TROUBLESHOT IAW FIM 21-33-01. RAN RTS ON ACC-1, 2, 3 IAW AMM 21-62-01. ALL TESTS PASSED. RAN RTS ON CPC-1 & 2 IAW AMM 21-31-04. ALL TESTS PASSED. RAN RTS ON ESC IAW AMM 21-08-01. ALL TESTS PASSED. ACFT OK FOR SERVICE.