I do have an engineering background, and I know how to use Google .

The info on the size of air atoms (molecules, really) came from an article discussing why you lose more oxygen than nitrogen from the air in your tires... and the reason why filling your tires with pure nitrogen makes a little bit of sense. It keeps your tires at the original inflation pressure since the N2 leaks through the rubber and around the valve more slowly than air, which has about 20% O2.

Buy your tires from Costco and they inflate them with nitrogen as part of the service.

Also, you can buy a can of compressed Nitrogen and flush the inside of your airtite before closing it. That gets rid of all the nasty air pollution and replaces it with nice safe N2!