By way of example, PPM usually means "sections for each million". If you discover out that the focus of NO2text NO _2NO2​ is equivalent to 1 ppm, it ensures that if you're taking a "sample" of air and divide it into a million sections, one of them will encompass NO2text https://beauofugr.getblogs.net/69171169/top-latest-five-online-ppm-calculator-urban-news