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Question 2 (25 Marks) Consider the use of tracer gas to determine the air exchange rate, AER (per hour) in a room. This is achieved by injecting a stable gas into the room and then monitoring the decay in concentration with time. The governing equation is, C- Ce-. The information gathered is seen in Table 1. Table 1 Time Concentration Series for Tracer Gas Concentration (ppm) 10.0 8.0 6.0 5.0 3.3 Time (hr) 0 0.5 1.0 1.5 2.0 Joer with Google Locs (A) Estimate the AER of the room. (6 marks) (b) What other material could be used to estimate the age of air or the AER? (2 marks) (c) Another "tight" 300 m² home has an AER which is one-fifth of the value estimated in Question 2, part (a). The only source of CO in the home is a gas stove and the ambient concentration of CO is always zero. Suppose there is CO in the home at 6 pm, but then the oven and two burners are on for one hour. Assume that the air is well mixed in the house. Estimate the concentration of CO in the house at 7 pm and again at 10 pm. Assume the following values for S, CO, Oven - 1900 mg/hr, CO, Single top burner 1840 mg/hr) (8 marks) (d) On a clear summer afternoon with a wind speed of 3.20 m/s, the ambient particulate concentration was 1600 µg/m3 at a point 3 km downwind and 0.5 km perpendicular to the plume 2