What was found
DURING DESCENT, BOTH AFT LAVATORY SMOKE DETECTORS SOUNDED AND THEN STOPPED BY THE TIME THE ACFT WAS ON THE RUNWAY. NO SMOKE OR HAZE WAS SEEN, ENGINE ANTI-ICE WAS IN USE DURING THE DESCENT AND TURNED OFF ON SHORT APPROACH. IAW AMDS CARD 2120-2367 RAN THE LT & RT ENGINES, NO SMOKE IN CABIN, BUT OIL ODOR WAS PRESENT. INSPECTED THE LT & RT COALESCER BAGS, NO OIL PRESENT, BUT HAD AN OIL ODOR. REPLACED THE COALESCER BAGS IAW AMM 21-20. FOUND SLIGHT RESIDUE ON RT ACM OUTLET DUCT. VERIFIED NO ELECTRICAL ODOR PRESENT IN ACFT.. ACFT OK FOR SERVICE.