For instance, PPM signifies "pieces for every million". If you discover out that the concentration of NO2text NO _2NO2​ is equal to one ppm, it implies that if you are taking a "sample" of air and divide it into a million parts, one of these will include NO2text NO _2NO2​. https://free-ppm-calculator97395.sharebyblog.com/36504629/rumored-buzz-on-free-ppm-calculator