As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SFO - FLT 682 - AFTER TAKEOFF SFO, EN ROUTE TO ORD SMOKE AND FUMES NOTED IN THE CABIN. RETURNED TO SFO AND LANDED WITHOUT INCIDENT. REPLACED 8TH STAGE CHECK VALVE AND DUCTING TO PRE-COOLER DUE TO LINE BEING PLUGGED. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)