What was found
WHILE LOADING BAGS CARGO SMOKE ALARM AFT COMPARTMENT WENT OFF. OFF LOADED BAGS COMPARTMENT VERIFIED CLEAR OF SMOKE. NO SMOKE OR FIRE DETECTED DURING VISUAL INSPECTION.ACTION TAKEN:SWAPPED FIRE DET. UNITS 2, 3, & 4 WITH FORWARD UNITS 2, 3, & 4 FOR MEL PURPOSES. MEL'D FWD CARGO COMPARTMENT FIRE DETECTION SYSTEM INOP.