About This File
While I have nothing against the Sanity rules of Call of Cthulhu, I don't think they are necessarily suitable for all horror settings when simulating Fear. Another horror RPG that I believe does it just as well, if not better for my uses, is Pacesetter's Chill.
Years ago, I translated the Fear Check rules to BRP for a yearly Halloween BRP Chill game that I ran for more then a decade. Here are those rules, along with the rules for Sensing the Unknown. These rules are written by Michael Williams and only converted by myself.