Not sure of the scene you're discussing. They weren't in body armor right? Because we can safely assume whenever they're in body armor, they have oxygen (thus the fight scene in the airport).
Seriously, I do intend to carefully look for oxygen mistakes on my rewatch because I do think you're right.
- "The same idiots whining about cancel culture are the people who tried to cancel pretty much every video game, book genre, and RPG when I was a kid." - James S. A. Corey