SOUTH ST. PAUL, Minn. — Chuck McGinley, a chemical engineer, stepped out of his car, eyed the smokestack of an animal processing plant rising above the treetops, and inhaled deeply. At first he smelled nothing except the faint, sweet fragrance of the nearby trees.
Suddenly, the wind picked up. “We have an oh-my-God smell!” Mr. McGinley exclaimed.
Immediately one of his colleagues pressed a Nasal Ranger to his nose. The 14-inch-long smell-measuring device, which looks like a cross between a radar gun and a bugle, is one of Mr. McGinley’s most significant inventions.
Using terms from one of Mr. McGinley’s other standard tools, an odor wheel, a chart akin to an artist’s color wheel that he has been fine-tuning for decades, the team described the stink. “Sour,” one person said. “Decay, with possibly some petroleum,” said another.
Then, as quickly as it had arrived, the smell disappeared. “The wind decided it was going to