One example is, PPM means "elements per million". If you find out that the concentration of NO2textual content NO _2NO2​ is equal to one ppm, it signifies that if you are taking a "sample" of air and divide it into 1,000,000 pieces, one of these will include NO2text NO _2NO2​. https://talibj765cqb0.answerblogs.com/profile