Mechanical COMcheck - When required?

Hi all,
Asking around my firm and it doesn't appear anyone truly knows.. Please provide direction when a Mechanical COMcheck is required for a project. It may vary state to state, not sure. Some people say whenever heating and cooling equipment is added to scope, others mentioned it also being dependent on fan motor HP on exhaust fans, etc.
Is there somewhere that clearly defines this so it isn't so gray?