Is breathing in someone else’s exhalation for an extended amount of time harmful?

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Suppose you slept face to face with another person, and would therefore be breathing in nearly everything they are breathing out. Would breathing in so much CO2 (as well as the countless other chemicals we exhale) have any short or long term effects?

Edit: There was a CPR mouth-to-mouth in the past, but that didn’t cover the effects after an extended amount of time.

In: Biology

Cut and paste for your viewing pleasure…. The atmosphere is about 20 percent oxygen. People breathe this in, and breathe 15 percent oxygen out, making the air that’s left lower in Good Ol’ Oh Two, but still quite breathable.

Doubt it. For one, you wouldn’t both necessarily inhale and exhale in alternating patterns perfectly for an extended period of time, so you might both exhale at the same time which would force a significant amount of air away from your mouths.
Second, when you breathe out you force air away, which allows other “fresher” air to fill the void. Air moves just like a fluid and will allow most, if not all of the air in the room to mix, diluting the amount of CO2 you breathe in.

If you were however to go mouth to mouth with someone and just continually breathe in and out each others exhaled air you’d quickly lose sufficient oxygen and could pass out, suffer from brain damage, or potentially suffocate and die.