All of us have the experience of having breathed chlorine gas at some point when we visit a pool with chlorinated water or when we use a commercial sodium hypochlorite solution. The irritating effect that we experience on the mucous membranes when we breathe chlorine in higher concentrations is mainly due to hydrochloric acid, which is corrosive and toxic, and not to hypochlorous acid, which has a disinfecting effect on our mucous membranes.