One example is, PPM usually means "pieces for each million". If you discover out the focus of NO2text NO _2NO2​ is equal to one ppm, it signifies that if you take a "sample" of air and divide it into 1,000,000 parts, one of them will encompass NO2textual content NO _2NO2​. https://landenbigdy.blogdon.net/ppm-calculator-secrets-52751338