“Diethylphenylene diamine (DPD)” means a chemical testing reagent that measures bromine or free available chlorine and total chlorine, wherein the color changes from pale pink to dark red as the concentration of bromine or chlorine increases.

Source. (See Revision Note #1 at chapter heading for Env-Wq 1100) #8468, eff 11-1-05; ss by #10577, eff 5-1-14 (See Revision Note #2 at chapter heading for Env-Wq 1100); ss by #13198, eff 5-1-21 (formerly Env-Wq 1102.20) (see Revision Note #3 at chapter heading for Env-Wq 1100)