After learning in class how breathalyzers work, Robert Clain and Miq\guel Salas assembled a fart detector from a sensitive hydrogen sulfide monitor, a thermometer and a microphone and wrote teh 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 ranker, and a voice rates it on a scale of zero to nine," he says. "If it ranks a nine, a fan comes on to blow it away. It even records the noise so you can play it back later." After a few months of construction, they began field tests. "Well, the sample data wasn't the entire school, but we definitely tested it," Salas says.