By way of example, PPM implies "pieces for every million". If you find out that the focus of NO2textual content NO _2NO2​ is equal to 1 ppm, it implies that if you're taking a "sample" of air and divide it into 1,000,000 components, one of them will include NO2textual content https://onlineppmcalculator65062.kylieblog.com/37335283/the-smart-trick-of-online-ppm-calculator-that-nobody-is-discussing