Researchers at the University of Michigan, Ann Arbor, have developed a photoacoustic method for quickly detecting the tiniest of gas leaks--even those that might take a work week to fill a thimble. The technique teams a CO2 laser with two ultra-sensitive microphones and is said to be fast enough to be used on production lines. Examples of possible applications include checking fuel systems, exhaust components, and valve seals, according to researchers David Dowling and Serdar Yonak. In operation, the laser, tuned to the resonating frequency of the escaping gas, creates sound waves that are detected by the microphones. The project was funded by the Ford Motor Co.