The first purpose of this paper is to analyze the changes of effective opening area of automatically operated entrance doors according to the number of people passing through the doors and establish an simplified estimation method of these average area depend on door specifications and the number of people passing through the doors. And the second purpose is to quantify changes of outdoor air flow rate coming into the entrance hall of a tall office building on a winter day, by using observed data associated with crack size of various doors in the whole building and changes of the number of people coming into or out through entrances.
