For example, PPM suggests "components per million". If you discover out the concentration of NO2textual content NO _2NO2​ is equal to 1 ppm, it means that if you're taking a "sample" of air and divide it into one million areas, one of these will consist of NO2textual content NO _2NO2​. https://free-ppm-calculator60245.ssnblog.com/35673898/how-much-you-need-to-expect-you-ll-pay-for-a-good-free-ppm-calculator