Aerinah

29th Apr 2022

The Martian (2015)

Question: When Watney causes an explosion while trying to hydrate his plants with hydrogen, he states that it was because he didn't account for the oxygen he'd been exhaling. We exhale carbon dioxide, with only trace amounts of oxygen. Could such tiny amounts of oxygen actually be calculated in his circumstances?

Smokyoak

Chosen answer: It's not about calculating the precise amount of oxygen. What Watney means is he failed to take into account the fact that he would be exhaling some oxygen, so he wasn't careful to make sure his exhaled air didn't get anywhere near the still (by wearing a sealed, airtight helmet/spacesuit). (Also, there's more than just a tiny trace of oxygen in our exhaled air - for example, it's enough to support someone receiving mouth-to-mouth resuscitation - as Watney recalls in the aftermath of the book version of this scene).

Aerinah

I did check the book, then did further research. You were right-we exhale about 16-17 % oxygen. I understand what you were saying about the percentage not being the issue now. Thx for the informed reply.

Smokyoak

I looked it up before asking the question. That's how I found out only trace amounts were being exhaled. I'll recheck the book as you stated.

Smokyoak

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