The Residual Chlorine Dioxide Test Strip detects levels from 0-10ppm in increments of 0.25, 0.5, 1, 3, 5, and 10. The color chart ranges from a light to dark pink. Chlorine dioxide has a higher oxidation capacity than chlorine or ozone, which means lower concentrations of chlorine dioxide can be used to achieve effective disinfection. It can also be used when large amounts of organic matter are present.