In the movie Sunshine, the explosive package is in a vast chamber attached to the shield, presumably filled with air. Why was oxygen deprivation an issue earlier in the film? A football team could have been practicing in there for a week and not run out of air.
It's a movie with plenty of opportunity for explaining this away. There was a fire which burned a lot of oxygen, There's the icarus I and II, one with and one without a functioning oxygen garden and at least one damaged airlock, so one should not assume that the chamber was or always were filled with oxygen.
That said, this is a movie where a space ship travels to the sun. With the intention of blowing up a supernova bomb which will fix everything. A football team could have practiced inside the logical holes of the plot.