The control of ever-increasing air pollution has become one of the most urgent problems of today. Man, through some of his machines, has created an astonishing health problem: he is increasingly fouling his most precious commodity, the air he breathes.Even though machines have been put to shocking and tragic use, man's greatest and proudest triumphs have been produced through the machine. Harnessed power greatly extends the productivity of man and has become necessary to his very existence. Our density is unalterably bound to the machine. We must learn to live with it.