ONT-3 discusses chemical disinfectants and their uses. It provides 3 types of disinfection: prophylactic disinfection which includes sterilization methods like chlorination; therapeutic disinfection to treat infected tissues; and terminal disinfection during and after patient care to disinfect surfaces. Common chemical disinfectants discussed include chlorine, iodine, phenol, heavy metals like mercury and copper, and alcohols. Physical methods like heat and radiation are also mentioned.