For instance, PPM implies "areas per million". If you discover out the focus of NO2textual content NO _2NO2​ is equivalent to one ppm, it implies that if you take a "sample" of air and divide it into a million elements, one of these will consist of NO2textual content NO _2NO2​. https://online-ppm-calculator10874.theisblog.com/36983188/ppm-calculator-secrets