For example, PPM implies "elements for every million". If you find out the focus of NO2textual content NO _2NO2​ is equal to 1 ppm, it ensures that if you're taking a "sample" of air and divide it into one million elements, one of these will consist of NO2text NO _2NO2​. https://arthursrjfl.fare-blog.com/36934064/a-secret-weapon-for-free-ppm-calculator