Then you have to be able to use your inspection and testing equipment, collection of relevant standard documents. To know the data detected based on what documents.
The above to check, will be on-site inspection of the inspection instrument to see whether the inspection instrument in the validity period, the management of the inspection instrument area is standardized, the inspection of the use of records in detail, whether there is a person to maintain, maintenance and so on.
Won't ask particularly specialized questions, you must know how to operate, but also will let you operate to them to see, talk about the principle.