Ford F-150 Owner's Manual page 231

For proper care of soiled safety belts, refer to Interior in the Cleaning
chapter.
WARNING: Failure to inspect and if necessary replace the
safety belt assembly or child restraint system under the above
conditions could result in severe personal injuries in the event of a
collision.
2011 F-150 (f12)
Owners Guide, 3rd Printing
USA (fus)
Seating and Safety Restraints
231