I found a idea and it is very good on salt extractors and lava mixers.
You put a wall that allow gases etc.. and put a sign in it and write "Release only: Acid" and then the sign has a color of pink or green saying "Acid". And when acid or that element comes in, it allows it. If you type "Air" after the element, it allows air. This could be for blocking the element too or e-hole.
@rrusciguy(View Post) a wall is a way better idea than a sign... a popup box comes up asking for element ID and then it only allows that... ill try coding it. Anyone know how to add walls???