Reference no: EM132416457

Problem 1. Using a combination of illustrative mass balance solutions and words (1-2sentences is enough):

a. Explain the relationship between CADR and the air exchange rate and their effects on the indoorpollutant concentration.

b. Explain the relationship between irreversible surface reactions and time to steady-state.

Problem 2. Five people get into a car with an air exchange rate of 4 h-1 and an interiorvolume of 4 m3. Assume each person emits 35 g CO2/h. The five people drive for 2 hours total.

a. Calculate the CO2 concentration in the car after 15 minutes of driving.

b. Calculate the steady-state CO2 concentration.

c. How long to get to 95% of steady-state?

d. How long to get to 99% of steady-state?

Assume that one person smokes a cigarette for the last 10 minutes of the trip. The cigarette steadily emitsa total of 5 mg of PM2.5 (total mass of particulate matter less than 2.5 µm in diameter) (ignore deposition).

e. What is the final concentration of PM2.5 (in mg/m3) at the end of this trip?

f. Calculate the intake fraction for PM2.5 associated with the cigarette smoke for the non-smokersover the 10-minute period.

Problem 3. a. Explain why carbon dioxide (CO2) is used as an indicator of appropriate ventilation in buildings(a few sentences is enough).

b. The minimum acceptable ventilation rate for public spaces is often taken to be 8 liters per secondper occupant (8 L/s-person). This ventilation rate is based on the idea that the indoor CO2concentration should be less than the outdoor concentration plus 700 ppm (C ≤ Cout + 700 ppm)(ASHRAE Standard 62.2001). Using a mathematical calculation (start with the relevantdifferential equation and do a steady-state analysis), justify this occupant-number-basedventilation rate. Assume a person emits 35 g CO2/h.

Problem 4.  This problem involves a home that has an air exchange rate of 0.5 h-1 and avolume of 250 m3. Assume ozone penetrates across the building envelope of a home with a penetrationfactor (p) of 0.8 (i.e., 80% of the outdoor ozone makes it into the home with the infiltration air). Insidethe home, ozone is consumed on surfaces at a rate of β = Σvd·A/V = 2.8 h-1, and it is emitted by an iongenerator at a rate of 4 mg/h. Answer the following questions:

a. What increase in the outdoor ozone concentration (in ppb) would be needed to yield an exposureto ozone equivalent to that caused by the ion generator?

b. Assume that the ion generator runs continuously. What is the intake fraction associated with theemission of the ion generator at steady-state for someone living in the home? (Hint: make sureyou take air exchange and surface reactions into account. The IF ≠ Qb/Q in this case.)

c. Assume that the ion generator is turned on each night before the occupant goes to sleep and isturned off when he/she wakes up eight hours later. What is the intake fraction for ozoneassociated with the ion generator (ozone source) over these eight hours? (Same hint as in (b).

Problem 5. This problem relates to a room with an outside air intake and norecirculation airflows. This room is 50 m3 in volume with a ventilation flow rate of 60 m3/h. This roomalso has a back-drafting space heater that emits carbon monoxide. At time zero, a person enters the roomand turns on the space heater.

a. After 2 hours, the person has a blood carboxyhemoglobin level of 10%. What is the actual COconcentration in the room at t = 2 hours? Consider the ratio of COHb/O2Hb at equilibrium in thebody at all times. Provide your answer in ppm.

b. Assume that there is an air purifier that converts CO to CO2 indoors. Calculate the clean airdelivery rate (CADR) for the air purifier necessary in order to reduce the blood saturationcarboxyhemoglobin level to less than 2%. Provide your answer in cubic feet per minute (CFM).

Problem 6. This problem asks you to derive the mass emission rate of water vapordue to the exhalation one building occupant, using mass balances and your knowledge of air principlesfrom the class. Assume exhaled human breath is at 37 °C with relative humidity (RH) at 100%, and thebreathing rate is 18 m3/day. Assume that the room air is at 23 °C with RH at 50%.

a. Calculate the concentration of water vapor in exhaled breath (in g/m3).

b. Calculate the concentration of water vapor in the room (in g/m3).c. Determine the mass emission rate of water vapor for an occupant (in kg/day).