So everytime one of my dupes need to breath they will go and breath in some oxygen, but after that if the environment they need to work in afterwards has no oxygen they somehow just seem to stop breathing entirely. This fixes itself after they go back to a normal oxygenated area but happens again shortly after they go somewhere else, need to breath and then they stop breathing after catching some air.
Attached is the picture showing them using no air etc and my save file
Let the dupes continue building or investigating the chlorine geyser and it happens. I had been playing for about 2 hours but this is the only time I noticed it.