Inspection kit is a single use item. When someone uses the Inspection Kit on another Innocent(or Infected) They can see if it's infected or not. Only the user will see the result. no one else.
-When someone Uses the inspection kit NEVER trust it in the first sight. it might be the infected who used it. -You can use the inspection kit as an Infected to make others trust the other Infected too. -When someone wants to use the Inspection Kit on you, you should stay and don't run. Run gives away that you are surely infected, while staying still can make others think that you aren't infected, and don't belive the other guy. even if what he says is true. -Use the inspection kit anyway, even if you don't suspect someone is infected.