By way of example, PPM usually means "elements for each million". If you discover out which the focus of NO2text NO _2NO2​ is equivalent to one ppm, it signifies that if you take a "sample" of air and divide it into 1,000,000 components, one of these will include NO2text NO https://johnnyhtcmt.blogdeazar.com/36941958/rumored-buzz-on-free-ppm-calculator