What was found
RETURN TO DEPARTURE. UNKNOW VAPOR EMINATED FROM SIDEWALLS OF CABIN. VOLUME OF VAPOR WAS MUCH MORE THAN NORMALLY ASSOCIATED WITH HIGH HUMIDITY DAY. BOTH IN FLIGHT, CREW MEMBERS REPORTED NO ODOR OF BURNING. NO INDICATIONS OF SMOKE IN COCKPIT. NO EICAS MESSAGES, NO ODOR; PERFORMED SMOKE AND ABNORMAL ODOR INSPECTION AS A PRECAUTION IAW E-190 FIM TASK 21-20-00-810-801-A. NO DEFECTS FOUND AT THIS TIME. VAPOR SUSPECTED TO BE FROM CONDENSATION. ACFT IS OK FOR SERVICE.