Excerpt of news article:

"The detector, built by Picarro, a manufacturer of scientific instruments that has recently moved into the field of portable methane detection, is able to determine whether the gas originated from wells or was produced by the bacteria in swamps, landfills and sewers. Distinguishing between the two can prevent industrial polluters from plausibly denying that they have leaks.

The system was demonstrated in 2011, when researchers bolted it in the trunk of a car that drove through the streets of Boston, a city with a labyrinth of aging underground gas pipelines. In a peer-reviewed scientific journal last year, the researchers said they had found 3,356 leaks of methane, and some with concentrations 15 times normal methane levels in the atmosphere. ...

The Picarro detector works like this: An inlet tube takes in air samples, which are sent to a chamber in the trunk of the car. The chamber, about the size of a drum major’s baton with mirrors at either end, bounces a laser back and forth between the two mirrors thousands of times, like a fold-up yardstick. The laser’s path is ultimately several miles long and so is able to precisely measure concentrations of methane in the range of parts per billion.

An anemometer, an instrument for measuring wind speed and direction, is mounted on top of the car, as is a GPS device. In some models, an inlet pipe samples air from various elevations. The system uses an onboard computer to turn the readings into a three-dimensional model of a gas plume — a funnel-shaped flow of contamination — and calculates the location and size of the origin. Methane molecules incorporate a carbon atom of two different types, one more commonly found in gas from wells and the other in gas from landfills and sewers. Studying the ratio, the instrument can say where the gas came from.

Michael R. Woelk, president and chief executive of Picarro, said the advantage of the detector was that it could be used on public roads to locate leaks on private property."

http://www.nytimes.com/2013/08/07/business/energy-environment/new-t...