EWTN Catholic Q&A
in church
Question from JS on 03-02-2013:

Do demons enter the church building or is that one place we are safe from the evil one?

Answer by Richard Geraghty on 03-04-2013:

Dear JS,

The demons to worry about are the ones already in our souls if we are in the state of mortal sin. Otherwise we have now worry.

Dr. Geraghty