What was found
FOLLOWING TAKEOFF, GRAY SMOKE WITH AN OILY SMELL WAS OBSERVED IN THE COCKPIT AND CABIN. CREW PERFORMED THE AIR CONDITIONING SMOKE PROCEDURE PER COCKPIT OPERATING MANUAL AND DECLARED AN EMERGENCY, RETURNED TO DTW, AND LANDED WITHOUT INCIDENT. NR 1 PACK WAS PLACED ON DEFERRAL PER MEL 21-52-01A. SUBSEQUENT MAINTENANCE TROUBLESHOOTING REVEALED NO DISCREPANCIES. NR 1 PACK OPERATIONALLY CHECKED OK.