Our industry currently has one standard for shower filtration: NSF/ANSI Standard 177, which measures the reduction of free available chlorine. (Free available chlorine is the concentration of residual chlorine present as dissolved gas, hypochlorous acid, or hypochlorite ion, not combined with ammonia or other compounds that are less readily available for disinfection). While ThermalGuard catalytic carbon can reduce more than just free available chlorine, as a matter of company policy, we only publish reduction claims that have been based upon testing our products against established industry standards that have been conducted by a widely recognized, third-party laboratory such as the IAPMO and WQA. We recognize this may appear to put WaterChef shower filters at a disadvantage because of unvalidated performance claims made by competitive products. However, we are not comfortable with making claims that do not fit the strict NSF/ANSI certification criteria.