Airlock (untested)

Airlock used to prevent over pressure in fermentation containers for beer & wine or to prevent contamination from air exposure for certain biology experiments.

Water is slowly added to the outer chamber and flows into the inner chamber thus preventing ambient air from entering the container through the center pipe.

Gas build up in the fermentation container flows up the center pipe causing the water level in the inner chamber to lower until the gas can escape through the holes at its base