Such as, PPM suggests "parts for every million". If you discover out that the concentration of NO2textual content NO _2NO2​ is equal to 1 ppm, it means that if you're taking a "sample" of air and divide it into a million areas, one of these will encompass NO2textual content NO https://kylerolcsh.win-blog.com/17467447/top-ppm-calculator-secrets