What is internal auditing?
ISO 9001 versus ISO/CEI 17025

The laboratory must periodically carry out internal audits of its activities in accordance with a predefined procedure and schedule, in order to verify that its operations continue to comply with the requirements of the management system... These audits must be carried out by trained and qualified personnel who will be, whenever resources permit, independent of the activity to be audited.

The organization shall conduct internal audits...