One of the sisters had an interesting insight.  She said that Satan fills vacuums.  If the home isn’t filled with something, Satan will fill it.  She recommended using light and truth as the filler.

Here’s the thing.  My wife and I used to help run our community water system.  We learned there that the best way to avoid contamination was positive pressure or overpressure.  It’s hard for something to sneak in when the water is constantly trying to burst out.  Clean rooms operate on similar principles, I’m told.