Answer: Google Street View cars
It’s hard to miss the brightly painted car with a giant 360-degree camera mounted on its roof driving through bustling urban centers and down quiet rural roads. But while Google Street View cars are taking amazingly detailed photos of everything they pass, they’re now also monitoring air quality to detect natural gas leaks.
Starting in 2013 and funded by the Environmental Defense Fund, a fleet of Google Street View cars was fitted with high-precision methane analyzers. The cars map the locations of natural gas leaks, and measures their severity by taking in air through the front bumper and pumping it to a tube in the trunk, where its methane content is measured by a laser-based sensor. The system is continually taking air samples as the Google cars drive through neighborhoods, generating 2,000 data points per minute. By keeping track of where gas leaks are occurring, cities can better protect both citizens and air quality.