# Thread: Human air consumption (partly a math problem)

1. Okay, so I'm trapped in a box that measures 20 feet in length, 20 feet in width, and 10 in height. That's 4,000 cubic feet, correct?

I read that the average human consumes around 20 cubic feet of oxygen a day and even that part I'm not sure about.

So, if my box is airtight and I only breathe 20 cubic feet a day... I can survive for 200 days? (4,000 divided by 20.)

I don't think this is right. What am I missing? I'm guessing it has something to do with the carbon dioxide that's exhaled into the air, but I'm pretty sure a human can't breathe for 200 days in 4,000 cubic feet.

2.

3. Whoa. I think I just realized part of my mistake.

A human consumes about 20 cubic feet of OXYGEN a day, which I was confusing with air. So, if oxygen makes up 20% of air (which I read at howstuffworks.com), that would mean that there's only 800 cubic feet of oxygen in a 4,000 cubic foot room, right? I'm really bad at math so I have doubts that this is right.

Anyhow, assuming I know what I'm talking about (which I don't), that means a person could survive 40 days in an airtight box? That still doesn't seem right.

4. Part of the problem is the buildup of CO2, as you mentioned. Another problem is that you cannot use up all the oxygen in the room because you will die when the concentration reaches somewhere around 10 percent, certainly by 6 percent.

http://www.cdc.gov/niosh/90-103.html

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