Abstract: A room 100 in a building has a living etc. space 101 of volume V that is an enclosed space. Ventilation of an air flow F is performed from the outside to the living etc. space 101. Entering/exiting of air as an air current between the inside of the living etc. space 101 and the outside is eliminated, and at least a part of the boundary between the living etc. space 101 and the outside is configured from a gas exchange membrane 310 having a diffusion constant D, a thickness L, and an area A for gas molecules of interest. When air inside the living etc. space 101 is sufficiently agitated and the concentration of gas molecules constituting the air is made spatially uniform, ?(t) is controlled so as to vary according to ? ? ( t ) = ? o - BL AD ? ( 1 - exp ? ( - [ AD ? / ? L ] ? t ? / ? V ) ) ( 9 ) B(m3/s) is the gas consumption amount inside the living etc. space 101, ?1 (t) is the gas concentration inside the living etc.

Abstract: A room 100 in a building has a living etc. space 101 of volume V that is an enclosed space. Ventilation of an air flow F is performed from the outside to the living etc. space 101. Entering/exiting of air as an air current between the inside of the living etc. space 101 and the outside is eliminated, and at least a part of the boundary between the living etc. space 101 and the outside is configured from a gas exchange membrane 310 having a diffusion constant D, a thickness L, and an area A for gas molecules of interest. When air inside the living etc. space 101 is sufficiently agitated and the concentration of gas molecules constituting the air is made spatially uniform, ?(t) is controlled so as to vary according to ? ? ( t ) = ? o - BL AD ? ( 1 - exp ? ( - [ AD ? / ? L ] ? t ? / ? V ) ) ( 9 ) B(m3/s) is the gas consumption amount inside the living etc. space 101, ?1(t) is the gas concentration inside the living etc.