SenSafe® Free Chlorine Water Check test strips are the ONLY EPA APPROVED (Published in the 2007 Federal Register (vol 72, no 47, Monday, March 12, 2007 p. 11204, ITS method D99-003)) test strips used for drinking water compliance monitoring. They combine a wide range of water quality detection with our patented Free Chlorine indicator. Designed to resist interference from monochloramines, Free Chlorine Water Check is the ideal product when testing drinking water quality. the SenSafe® Free Chlorine Water Check is perfect for determining whether or not you have the correct amount of sanitizer present. Furthermore, no external chemicals are needed to perform the water quality test so testing is quick, easy, and affordable.