Employees specifically authorized by the Department so to do shall inspect all “Official Testing Stations” at frequent intervals. Such employees shall have access to all records relating to tests and work done or parts sold as a result of such tests, to ascertain whether or not tests are properly, fairly and honestly made, and may examine the owner of the official testing station or any officer or employee thereof under oath. The Department shall conduct periodic nonscheduled inspection on owners premises of vehicles owned and operated by licensed “Independent Official Testing Stations.”