Vent/Pipe Opening For Letting Things Move Passively

[AzazelMalfeasan]

for ventilation, if the opening has a heavier gas going into it then it will be a down current only allowing movement down and horizontal, if the opening has a lighter gas going into it then it will only go up or horizontal.

for piping, any liquids that enter an opening will only go down or horizontal.

This would make ALOT of sense, seeing as heavier gases and fluids will go down, so if you have a pocket of fluid above another one but have lots of stuff like electronics in between but you don't want to build an elaborate slide for the fluid to go down.  As for gases, if you want you are keeping alot of gas in one place and want to depressurize it just to the immediate surroundings, you could open a vent and it will slowly flow out, or in, without having to bother with tedious door mechanisms that require dupes to go there at certain times and risk suffocating or walking away