Something that I am sure lots of #scifi writers and gamemasters have thought about:
How bad is it when you get bullet holes in your space ship?
If you can get to safety before pressure drops to 30 kPa, you will be fine. At that point, you might have a minute or two before you pass out.
I found this equation to calculate how long it takes for pressure to drop that far:
Time(s) = volume(m³) / hole (cm²) * 30
One bullet hole in a 2x2x10m corridor gives you 12 minutes to deal with it.
@Yora And if your atmosphere is oxygen-nitrogen mix for any reason, wearing oxygen mask makes the situation equivalent to the one where your atmosphere was pure oxygen.