Just to add to masalamas post, 100% breath analyzer tests for all flights, and with a tolerance of 0%. If the alco sensor shows any percentage above 0, you are treated as a positive case
I seem to remember, after having read previous threads on here about pilot intoxication, that it is possible to blow over 0%, even after having had no alcohol. Your threshold might need a little adjusting, before you ruin some(innocent)one's career...