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Nanoparticles in air

What is nanoparticle concentration?

Nanoparticles are classified into three categories: natural, “anthropogenic” and manufactured nanoparticles. In ambient atmospheres (office, housing, …), the average concentration of nanoparticles is in the region of 103 to 5x104 part.cm-3 (for particles having a median diameter less than 2x102 nm). But these values vary widely in time and space.

Does concentration fluctuate?

Nanoparticle density depending on the context.

A cube of one millimeter of side contains 10 to 50 natural nanoparticles. In a polluted atmosphere, this rate is weighted by a factor 10 to 50.

Air movements impose very high fluctuations on this density: at the entrance to a "clean room", for example, it varies from 1 to 102 part.cm-3 during an hour. On the landing strip of an airport, there are wide variations around an average value of about 7x105 particles.cm-3.