What was found
DURING PUSH BACK, MAIN CARGO FIRE WARNING ON FLT DECK AND MX CAME IN TO THE A/C TO INVESTIGATE & NOTICED LOW LINE FOG THROUGH OUT THE MAIN CARGO DECK W/ NO ODOR. PRIOR PUSH BACK, WE WERE DEICED & WAITED ATLEAST 1 MIN BEFORE PACKS WERE TURNED ON. INSPECTED MAIN DECK CARGO COMPARTMENT, VERIFIED NO EVIDENCE OF FIRE ON BOARD. DETERMINED DE-ICE FLUID WAS INGESTED INTO PAC SYSTEM. ACCOMPLISHED AMM 21-00-21-2 AIR CONDITIONING SYSTEM OIL SMOKE/FUME CONTAMINATION (REMOVAL) - MAINTENANCE PRACTICES AS REQUIRED. AIRCRAFT CHECKS GOOD, OK FOR CONTINUED SERVICE.