One example is, PPM signifies "elements for every million". If you find out that the focus of NO2text 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 sections, one of them will encompass NO2text NO _2NO2​. Changing https://online-ppm-calculator64339.oblogation.com/35751793/how-much-you-need-to-expect-you-ll-pay-for-a-good-online-ppm-calculator