Change control is a formal system to review proposed and actual changes that could affect a product's validated status. It aims to determine if actions are needed to maintain validation. Changes are classified as minor, major, or critical based on their potential safety/efficacy impact. Approval levels 1-3 require sign-off from different departments. The change control procedure involves documenting changes using a form, assessing the need and approving/rejecting changes, planning implementation, verifying the implementation, and closing the change request once complete.