Think about the worst case scenario: you have sex, maybe date for awhile, then it ends really badly and you continue to work for the same company and it is terribly painful whenever you see him. Is that worth the possible upside of acting on your crush?
If you decide it is, then is the “talk” you want to have something like—I really like you and I don’t want to have sex just to have sex, I would like to explore the possibility of an actual relationship? Then say that.