As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
YUL - FLT 4005 - AIR RETURNED DUE TO SMOKE FILLING CABIN AND COCKPIT. MAINTENANCE OPERATIONALLY CHECKED AIRCONDITIONING IN REF TO EMB145 MM 21-00-00. OPS CHECKED GOOD. SUBMITTER STATES, SUSPECT DE-ICING FLUID ON T/O RAN INTO APU INLET CAUSING SMOKE. (M)