.. CO2 tracer gas decay method is employed to measure the ventilation rate in a naturally ventilated room. The outdoor CO2 level is a constant at 506.7 ppm. The indoor CO2 level as a function of time is listed below. The volume of the room is 180 m. The air density is 1.225 kg/m. (1) Derive the indoor CO2 level as a function of time, outdoor CO2 level, ventilation rate, air density, and room volume based on mass balance. (2) Calculate the ventilation rate in m/h. Time (h) 0.00 0.02 0.03 0.05 0.07 0.08 0.10 0.12 0.13 0.15 0.17 0.18 0.20 0.22 0.23 0.25 0.27 0.28 0.30 0.32 0.33 0.35 0.37 0.38 0.40 0.42 0.43 0.45 0.47 0.48 0.50 Indoor CO2 (ppm) 990 994 989 986 981 975 971 958 952 950 936 938 933 932 931 918 909 903 904 901 897 875 876 872 872 870 868 862 864 858 859