For instance, PPM indicates "elements per million". If you discover out that the focus of NO2textual content NO _2NO2​ is equal to 1 ppm, it implies that if you take a "sample" of air and divide it into a million areas, one of them will consist of NO2text NO _2NO2​. https://ppmcalculator93603.full-design.com/examine-this-report-on-online-ppm-calculator-79078300