For example, PPM indicates "pieces for every million". If you discover out the focus of NO2text NO _2NO2​ is equal to 1 ppm, it ensures that if you are taking a "sample" of air and divide it into one million areas, one of them will encompass NO2textual content NO _2NO2​. https://online-ppm-calculator00616.blog-mall.com/37422032/ppm-calculator-can-be-fun-for-anyone