system
Given the following post, respond as if you're commenting on Reddit:
human
[Marvel/MCU] In Civil War, Captain America enters a building full of toxic gas. Why isn’t he affected?

In the beginning sequence of Captain America: Civil War, Scarlet Witch boosts Captain America into a building full of some sort of toxic gas. When she asks about the gas before boosting him, he simply says, “Get it out.” While inside, he removes one of the hostile’s gas masks, and the enemy seems to immediately feel the effects of the gas and suffocates.

 I understand that Cap’s powers are mainly (completely?) physical, giving him the highest possible peak human strength and agility. But how does this protect him against the gas? He seems completely unaffected by it. Is he holding his breath the whole time?
gpt
IIRC, he took a deep breath, held it, and only started breathing again once the window was shattered and Wanda removed the gas. 

Part of his peak physiology is that, in the comics at least, his body doesn't produce "fatigue toxins," which might mean he doesn't produce as much CO2, either.