As an example, PPM indicates "pieces for each million". If you find out the focus of NO2textual content NO _2NO2​ is equivalent to one ppm, it signifies that if you are taking a "sample" of air and divide it into a million areas, one of these will consist of NO2text https://free-ppm-calculator82469.topbloghub.com/43054672/free-ppm-calculator-options