While using corner water locks to isolate areas and create vacuums between biomes, I kept finding that over time, gasses were being exchanged and my vacuums were disappearing. I setup notifications in several water lock areas, and found that occasionally, when a duplicant is crossing the water lock, there is an exchange of atmosphere. This does not always happen, and I have not determined any factors why sometimes crossing the lock leaks atmosphere, but usually it does not. I have tried with a variety of liquids, such as super coolant and viscogel, but have run into the same behavior.
1. Build a water lock, preferably with a vacuum to make it easier to identify atmosphere leaks
2. Have duplicants in full suits (to prevent breathing contamination) repeatedly cross the lock