Such as, PPM means "pieces for every million". If you discover out that the focus of NO2text NO _2NO2​ is equivalent to 1 ppm, it signifies that if you're taking a "sample" of air and divide it into 1,000,000 elements, one of them will include NO2textual content NO _2NO2​. Rijk https://ellena580bax1.muzwiki.com/user