Safebreath Pro advertises using nanotechnology to filter out air contaminants that are larger than PM 2.5. But what does that mean?PM 2.5 is basically a size rating for Particulate Matter that is less than 2.5 micrometers – around 3% the diameter of a human hair. As you can imagine, this is really small, in fact, it is so small that it can’t be seen without the help of an electron microscope.Click Here