As an example, PPM usually means "components per million". If you find out which the focus of NO2textual content NO _2NO2​ is equivalent to 1 ppm, it implies that if you're taking a "sample" of air and divide it into 1,000,000 areas, one of these will encompass NO2text NO _2NO2​. https://online-ppm-calculator14579.is-blog.com/43375263/the-single-best-strategy-to-use-for-online-ppm-calculator