For example, PPM suggests "pieces for each million". If you find out the concentration of NO2textual content NO _2NO2​ is equal to one ppm, it implies that if you're taking a "sample" of air and divide it into 1,000,000 parts, one of these will encompass NO2textual content NO _2NO2​. PPT https://knoxjzisc.blogars.com/35504538/a-secret-weapon-for-free-ppm-calculator