One example is, PPM signifies "areas for every million". If you find out the focus of NO2text NO _2NO2​ is equivalent to one ppm, it signifies that if you take a "sample" of air and divide it into 1,000,000 components, one of these will include NO2textual content NO _2NO2​. Rijk https://landenlrqmg.blogzet.com/free-ppm-calculator-no-further-a-mystery-51469513