**The Best of Creative Computing Volume 1 (published 1976)**

Initially, let's concentrate solely on carbon monoxide pollution. This gas is fairly stable and quite persistent. We will need some concentrations and their effects to use in the exercises. A carbon monoxide concentration of 1000 parts carbon monoxide to one million parts air (abbreviated l000 ppm) is sufficient to produce unconsciousness in l hour and death in 4 hours. The maximum allowable concentration for industrial workers for an eight-hour working day is 50 ppm. Concentrations of from 25 to 50 ppm will be experienced inside an automobile moving in a heavy stream of traffic in a multilane highway or freeway. EXERCISE 2 - A Simple Model Write a BASIC program to compute and print out the number of cubic feet of carbon monoxide in our residential area every hour for a 24-hour period. Assume that at the beginning there is no carbon monoxide in the air. Use the number of cars running which you estimated in Exercise 1. The carbon monoxide production rate per car can be obtained from Table 2. EXERCISE 3 - Computing Concentrations Modify the program in Exercise 2 to print out the carbon monoxide concentration in ppm (parts per million) at the end of every hour. EXERCISE 4 - Lethal Concentrations Using elementary algebra, compute how long it will take to reach the lethal concentration of 1000 ppm in the residential district. Make the same assumptions as for Exercise 2. Taking the fundamental assumptions of our model into account, do you feel there is a carbon monoxide hazard associated with life in a normal residential area? EXERCISE 5 - A Garage Problem Use algebra to compute how long it will take for a single automobile, in a closed garage with the engine running at a speed equivalent to 40 mph, to produce a carbon monoxide concentration of 1000 ppm. State clearly any assumptions you make. Is there a hazard here? EXERCISE 6 - Intersecting Freeways Suppose that two major freeways cut across our residential district and intersect at the center. Use the model given by (1) and compute the carbon monoxide concentration in ppm. State any assumptions which you must make. Do you feel there is a carbon monoxide hazard in this situation? EXERCISE 7 - A Tunnel Problem It is not uncommon to find highway tunnels one mile long carrying two lanes of traffic in each tube. Suppose the ventilation fans went out just as you entered the tunnel. Is there a carbon monoxide hazard? State any assumptions you make. By now you surely have detected serious flaws in our model. We have been handling only carbon monoxide but, according to Table 2, there are other pollutants present. We have assumed that no air moves in or out of our residential district, but usually there is at least some wind, and wind certainly carries away pollutants. Also, we have assumed that once pollutants are created, they are with us forever. However, the pollutants do break down, or are gradually eliminated from the air by mechanisms other than wind. 225