High personnel density incurs suffocation
With a high population, if members are not equally spread around a large station O2 is not provided quickly enough. This occurs even if O2 capacity is over twice what is needed.
In one instance, there were five O2 recyclers close to a bar with 8 people; after a small while all 8 began panicking about O2. The O2 overview shows that most of the station is below around 50 percent whilst production rooms are nice 'n green. They just can't distribute enough O2 fast enough I guess.
I don't remember if I had this problem in 1.7.1, but might be because I was using upgraded O2 recyclers during that playthrough (I used nearly the exact same station design).