For example, PPM suggests "pieces for each million". If you find out that the concentration of NO2textual content NO _2NO2​ is equal to 1 ppm, it means that if you take a "sample" of air and divide it into one million components, one of these will consist of NO2text NO https://free-ppm-calculator58901.uzblog.net/the-best-side-of-free-ppm-calculator-50336451