[jacurtis]

Yes there were oxygen scrubbers on-board that had an estimated endurance to provide clean air for about 5 days for 5 people.

It has come out that it is wildly untested and optimistic estimate. The longest mission they had conducted onboard was 12 hours. So the theoretical limit may not be realistic. If there was panic onboard, that would increase oxygen usage dramatically, which could cut as much as 25% off the estimate (which is nearly a day in this case).

In other words... it is grim.

[dikei]

Nitpick: it's CO2 scrubbers, not O2. A scrubber primary mission is to absorb CO2, not generate O2.

[datameta]

So they will peacefully fall into sleep due to hypoxia instead of a slowly rising sense of impending doom as would result from rising C02 levels.