By way of example, PPM signifies "areas for each million". If you discover out that the concentration of NO2textual content NO _2NO2​ is equal to one ppm, it means that if you're taking a "sample" of air and divide it into one million components, one of them will include NO2textual https://manuelngugr.blogolize.com/ppm-calculator-things-to-know-before-you-buy-75708634