Question 4- A building, 20 m wide 25 m long 5 m high is ventilated at a rate of 200 m/h. The inflow air contains CO2 at a concentration of 0.6 g/m?. There is an internal source of CO, in the building of 500 g/h. What is the mass of COz in the building and the exit CO2 concentration?

6. If the concentration of C02 in Question 4 has reached steady state of 3.1 g/m3, and then the internal source is reduced to 100 gfh, deduce the equation expressing the time course of C02 concentration decay and the new steadystate value. --ln(a+bx) Given dx 1 [a + bx _ b