What is Mould-X? MOULD-X is a mould exterminator for killing mould and mildew. It removes mould stains and dirt from hard surfaces. MOULD-X can be used for both indoor and outdoor areas. Key Benefits - MOULD-X destroys mould and mildew. MOULD-X removes mould stains, dirt, fats, oils, soap build-up and other soilage. How Does It Work? MOULD-X contains available chlorine which is present in solution in the form of sodium hypochlorite and hypochlorous acid. Hypochlorous acid is a powerful germ-killing agent which kills mould and mildew. MOULD-X also contains caustic alkali and detergents to provide an excellent cleaning action.