For instance, PPM usually means "elements for every million". If you find out which the concentration of NO2textual content NO _2NO2​ is equivalent to 1 ppm, it implies that if you are taking a "sample" of air and divide it into 1,000,000 parts, one of them will include NO2text NO https://online-ppm-calculator17835.bloguerosa.com/35625765/5-essential-elements-for-ppm-calculator