As an example, PPM implies "areas per million". If you discover out the focus of NO2textual content NO _2NO2​ is equivalent to one ppm, it implies that if you are taking a "sample" of air and divide it into 1,000,000 pieces, one of them will consist of NO2text NO _2NO2​. https://saddamw467uun4.boyblogguide.com/profile