You’re in luck. For their senior project, two Cornell University computer-engineering whizzes recently built a machine that does just that. After learning in class how breathalyzers work, Robert Clain and Miguel Salas assembled a fart detector from a sensitive hydrogen sulfide monitor, a thermometer and a microphone and wrote the software that would rate the emission. A “slight perturbance in the air” near the detector sets it to work measuring the three pillars of fart quality: stench, temperature and sound. Temperature, Clain explains, is critical. The hotter a fart, the faster it spreads. “It beeps faster if it’s a high...