The purpose of this research is to identify environmental factors related to the ease of borrowing a cigarette lighter from a stranger in a smoking area. An experiment was carried out in which subjects actually talked to ordinary smokers and borrowed lighters at smoking areas in Yokohama city. As a result, it was found that the ease of talking to a stranger corresponds almost exactly to the ease of entering the smoking area. The distance between the smoking area and the surrounding traffic, and the numbers of surrounding pedestrians were connected with the ease of borrowing behavior. The width of the entrance to the smoking area and the arrangement of benches, etc. were also related to the evaluation. The characteristics of suitable smoking areas for borrowing behavior were summarized into three main factors, that is, people can approach the place without feeling too conspicuous, smokers in the place seem not to have monopolized spaces, and the smoking area has a casual atmosphere which promotes interaction between people.