still design question, a little clarification

[NCshineR]

Hey everyone, i been researching and researching, and maybe im missing it, i probably am but on the reflux, the boka specifically it seems like the head where the coil is located is uncapped.. and leading directly down the column, is that right?? wouldnt you lose potential alcohol vapour like that? not to mention make a serious fire hazard? or would it be that steam is the only thing escaping from the top because the alcohol is condensed and runs back down the column? i could just be missing it and if its been posted my apologies, but i am thinking about building one but putting a cap on it with it vented as that would be the only vent other than the 1/4 distillate drain.. or should i just leave it open.. im a bit confused on this part any help would be great...