The oil mist or kitchen exhaust diffuses into various parts of a house as well as the kitchen itself, the mist is responsible for the formation of oil stains on the surface of respective rooms, i.e. , the surface of the ceiling and walls. With an open type kitchen, a range of the oil mist diffusion tends to expand, and the authors believe that the condition of the living-cum-dining room might be deteriorated as a result. Twelve residences in Niigata City were chosen to clarify the extent of the oil stain accumulation. In the first place, four to five Teflon sample plates (20×40 mm) were installed at four corners of the ceiling of the kitchen and living-cum-dining room. Three months after the installation, a process of removing the plates that had been installed in the corners of the ceiling started: the plates were removed one at a time in an interval of one month in order to measure the color difference ( E ∗ab reading) by chroma meter. Furthermore, in some of the houses chosen, the sample plates were installed in the other rooms as well. It was confirmed that E ∗ab reading in all residences had increased in accordance with the passage of time. It was noted that the oil stain had a high tendency to accumulate at points where the ventilation stayed, and that the sagarikabe wall was effective for preventing the diffusion of the oil mist. It is also to be noted that the kitchen layout as well as the cooking performance at respective homes had much to do with the accumulation as well as the condition of the oil stains.