if you are the "employer" then there is no "sure fire way" other than checking out the resource yourself. Who ever is the "employer" is whom is responsible for insuring the operator is qualified to operate the machine.
If they are employees of a contractor, have the contractor certify to their training and competence.
"Due diligence" sometimes is more complicated than checking boxes....
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.