What total volume of air does a person breathe in a lifetime?

Question

a person breathes about 500cm^3 of air with each breath.

Answer 1

To find out, we need to calculate the fraction of the atmosphere a person breathes in a lifetime, and then compare that fraction to the number of atoms in a breath. For example, if Isaac breathed one in every thousand atoms in the atmosphere, and there were a million atoms in each breath, you and Ike would have a good chance of sharing more than a passing interest in physics.

Each time you breathe you inhale about one liter of air (a liter is 1000 cm3, or 10-3 m3). The average person takes ~10 breaths/ minute, which over a lifetime corresponds to 300 million breaths. At 10-3 m3/ breath, this is 300,000 m3 of air. The atmosphere, of course, is much larger. You can estimate its volume from the thickness of the atmosphere (about 10 miles before the density has dropped precipitously) and the earth's diameter (8000 miles). Working out the numbers, the earth is covered by about 1019 m3, so a person in a lifetime consumes 1 part in 1013 of all the available air. That doesn't sound like much, but there are a lot of atoms in a breath of air. In fact, there are about 1025 atoms in 1 m3, so you are probably recycling billions of atoms from Sir Newton (or indeed, simultaneously billions with anyone and everyone you can think of).

Similarly, a car "breathes" air as well. A car's engine is often rated in liters, but unlike a person, it breathes with every r.p.m, about 1000/minute. So even though a car is off most of the day, it breathes about as much as a person. Consequently, your lungs have as much in common with a V-8 as they do with Sir Isaac Newton. Fortunately, there are mechanisms in place in the environment to cleanse and recycle the atmosphere, but we do breathe the sins of our past.

Answer 2

Yes, assuming they are at rest.

They breathe about 10 times per minute, average lifespan, say, 80 years.

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