As an example, PPM implies "areas for each million". If you find out the concentration of NO2textual content NO _2NO2​ is equivalent to one ppm, it implies that if you are taking a "sample" of air and divide it into one million areas, one of them will include NO2text NO https://caidenlqpli.theisblog.com/36984731/top-latest-five-free-ppm-calculator-urban-news