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What is air made of?
The air we inhale is composed of nitrogen (78 %), oxygen (21 %) and traces of rare gases (1 %). Four nitrogen molecules for one of oxygen occupy an air cube about 5 nm per side. They move about 5x102 m/sec on an average circuit of about 70 nm. If the air is warmer, the occupied volume and speed are more significant. A one millimeter side cube contains a very high number of molecules but it is mainly empty.
Size, movement and density of air molecules.
The air also contains nanoparticles 102 to 103 times larger than the molecules. What is the density of nanoparticles? Is this number stable? Can we distinguish the origin of nanoparticles? What can we say about their behavior? How can we specifically detect them?