One example is, PPM implies "parts for every million". If you find out the focus of NO2textual content NO _2NO2​ is equivalent to 1 ppm, it signifies 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://joshu599tla0.dekaronwiki.com/user