For instance, PPM usually means "parts for every million". If you discover out the concentration of NO2text NO _2NO2​ is equivalent to one ppm, it ensures that if you're taking a "sample" of air and divide it into a million sections, one of them will consist of NO2text NO _2NO2​. https://josueiddbh.bloguetechno.com/new-step-by-step-map-for-free-ppm-calculator-71989096