As an example, PPM suggests "areas for each million". If you discover out which the focus of NO2text NO _2NO2​ is equivalent to one ppm, it means that if you're taking a "sample" of air and divide it into 1,000,000 parts, one of these will encompass NO2textual content NO _2NO2​. https://josephr987fpy8.wikiusnews.com/user