A disinfectant kills bacteria, but these bacteria have to be accessible. Most bacteria are namely hidden under a layer of grease and dirt. It is, therefore, necessary to clean and degrease before disinfecting. A bacteria under a dirty layer cannot be reached otherwise. Always use a good cleaning agent to remove the layer of grease, before you go into the hallway with a disinfectant. You just don’t rinse you off a plate of mayonnaise underneath the tap.