[Calculation of carbon monoxide concentration based on a ventilation model for two rooms]

We have estimated the gas concentration in an upstairs room following leakage of gas from a ground-floor room. The method used to calculate the gas concentration in the upstairs room was based on a ventilation model for two rooms. The assumptions on which the calculation was based were: 1) Uniform diffusion of gas. 2) Presence of slight openings in the room wall. 3) Reported data on the volume of the openings between the downstairs ceiling and the upstairs floor. 4) Calculation of the ventilation rate based on buoyant force. The upstairs gas concentration became steady within 4-7 h after the leakage. The ventilation rates for the 1st and 2nd floors at a steady state were 0.86 and 0.63 (room volume/h), respectively. The volume of the room did not affect the gas concentration at the steady state.