Gases being displaced when reaches max gas pressure

So i have my desinfectation chamber in my home asteroid in the dlc, then i deconstructed a liquid reservoir (and rebuilded it) so all the pH2O dropped to the floor and started off-gassing, a few cycles after (2, maybe 3) i noticed there was chlorine gas near to my chamber, and when i checked for gases, my chamber was full of pO2, it looks like all the chlorine got displaced and moved, it crossed the tiles

Things to consider: In the photo my gas pump isnt powered yet, the door you see there is an airlock door from a mod, so its impossible for gasses to pass from one side to another, then the pO2 from the chamber is around 1800-2500g of pressure 

Mod link if needed: https://steamcommunity.com/sharedfiles/filedetails/?id=2093302246