As an example, PPM suggests "components for every million". If you discover out which the concentration of NO2textual content NO _2NO2​ is equal to 1 ppm, it implies that if you're taking a "sample" of air and divide it into a million components, one of these will include NO2textual content https://ppmcalculator70246.targetblogs.com/37146599/the-basic-principles-of-free-ppm-calculator