Available Chlorine

Available chlorine is the measure of oxidising chlorine species (primarily hypochlorous acid and hypochlorite ion) in a disinfectant solution that can participate in antimicrobial action. It is usually expressed in parts per million (ppm) or as a percentage, and is the key metric used to compare chlorine-based disinfectants at their in-use dilution.

Two products can contain very different total chlorine content yet deliver the same available chlorine once diluted. Specifying disinfection protocols by available chlorine (e.g., 1,000 ppm) ensures that outcomes are comparable regardless of the source chemistry.

Referenced in infection control guidelines, food safety standards and manufacturer dilution charts to specify the strength of chlorine solutions required for different cleaning and disinfection tasks.