The Residual Chlorine test strip is for use in ensuring free chlorine levels in drinking water are sufficient to inactivate the bacteria and viruses that cause diarrhea disease, as well as ensuring the water is protected from re-contamination during storage. The strip can also be used to ensure systems have no residual free chlorine after chemical sanitation by testing for very low levels of free chlorine in solution from 0.0 ppm – 5.0 ppm. The residual chlorine test strip is accurate within 5-10% of reading the color scale. The vial can be sold with an illustrative color chart, which is helpful when testing drinking water from chlorine kits in developing countries. A standard color chart is also available for checking residual chlorine after sanitation. Please specify your use when ordering.