Liquid concentrate for professional users (product types PT2, PT4). It can be used in catering, private and public health care, the food industry, and other industrial areas where the aim is to clean grease-contaminated, calcified surfaces, remove milk stone, metal oxides, etc., and at the same time disinfect the surface. First, prepare a working solution with the desired concentration (50-100 ml of chemical per 1 liter of water) and temperature (20-50°C, raising the temperature enhances the effect) by diluting the product appropriately, and then perform the operation with this solution. The working solution can be applied to the surface by spraying, brushing, dipping, or other means.