As an example, PPM means "areas for each million". If you discover out the concentration of NO2text NO _2NO2​ is equivalent to one ppm, it ensures that if you are taking a "sample" of air and divide it into 1,000,000 elements, one of these will include NO2textual content NO _2NO2​. https://freeppmcalculator08417.total-blog.com/rumored-buzz-on-free-ppm-calculator-61994731