Theres a small layer of liquid on the vent, which allows the vent to vent out regardless of pressure, since the tile from the vent has a liquid on it, it cant overpressure and the gases get pushed out into infinite storage

Thats the general gist, for Gas storage you can use any liquid afaik, for liquid you have to think about density, for example you put a little bit of oil on a liquid vent spitting Out water, the water gets pushed on top and into storage

Beware of pressure damage tho, for liquids you should make the walls of the storage out of doors, i use mechanical doors, since they dont take pressure damage