LENOX TOWNSHIP, Pa. — Ryan Klemish is a fugitive hunter, pursuing an elusive quarry: natural-gas leaks at Southwestern Energy's Marcellus Shale production facilities.

Klemish roamed the company's Valentine gas compressor station recently in this rural Susquehanna County community, aiming an $85,000 infrared camera at flanges, valves and connectors. "If there's a leak, a big one, you usually know it because you can hear it," said Klemish. But the camera can detect even wisps of invisible and odorless methane, the key component of natural gas, a potent greenhouse gas when it escapes unburned into the atmosphere.

If Klemish finds a leak, a technician can fix it on the spot — often, it requires only a twist of a wrench to tighten a seal. More complex repairs typically are done within 15 days.

Southwestern Energy — the nation's third largest gas producer, operating nearly 500 shale-gas wells in Pennsylvania — launched its leak detection and repair program about five years ago. The aim was to capture a valuable product, but also to address emerging concerns that methane leaks were wiping out the purported greenhouse-gas benefits of the nation's shift from coal to natural gas.

"I like to say my job is running around chasing methane molecules, trying to keep them in our system," said Douglas Jordan, the corporate environmental-program director, based at Southwestern's headquarters in Houston.

Southwestern's efforts were ahead of those by its competitors, not all of whom appreciated the company's acknowledgment that methane leaks were a problem. The Trump administration, acting at the behest of some industry players, attempted to roll back rules adopted last year by the Environmental Protection Agency to restrict methane emissions from new oil and gas wells, including requirements that producers conduct leak-detection work. In July, a federal court slapped down the Trump administration's objections.

Last year, Gov. Wolf proposed new rules aimed at reducing methane emissions in Pennsylvania, which also have encountered resistance. The rules revise air-permit requirements for gas compressor stations and create a new requirement for air permits for shale-gas well sites. The industry says its voluntary efforts are achieving significant reductions without the addition of onerous new state burdens that may not sync with federal mandates.

"We absolutely support strong and workable regulations that foster these advancements. However, we are deeply concerned that many proposals are simply solutions in search of problems that will further impact the commonwealth's competitiveness without creating any meaningful environmental gains," said David Spigelmyer, president of the Marcellus Shale Coalition.

The perils of methane pollution drew the public's attention in late 2015, when more than 100,000 tons of natural gas leaked from an underground gas-storage facility in California, forcing thousands of nearby residents to relocate temporarily.

The oil and gas sector is the leading U.S. source of methane emissions, discharging more than either farming or landfills, according to EPA estimates. As a greenhouse gas, methane is more than 80 times as potent as carbon dioxide over 20 years, until it breaks down.

Though methane alone is not toxic, it is a volatile organic compound that contributes to the creation of ground-level ozone, which is a health risk. Natural gas, as it comes out of the earth, also sometimes contains toxic compounds such as benzene, toluene, ethylbenzene, and xylene. The pollutants are removed in processing plants before the gas is delivered to consumers. But stopping leaks at the wellhead has the added benefit of reducing the release of associated toxics into the atmosphere.

"When you tackle methane, you also get to reduce all these other pollutants," said Matt Watson, an associate vice president of the Environmental Defense Fund's climate and energy program.

Gina McCarthy, Obama's EPA administrator, who oversaw development of the federal methane rules, said in an interview last week that those rules were aimed at producing cost-effective solutions.

"It's really a missed opportunity for the oil and gas sector to be good neighbors, to be good community players and to make money at the same time," she said.

With the most obvious leaks already plugged, and at current low energy prices, the cost of further reducing methane leaks actually costs the company money, said Roy Hartstein, Southwestern's vice president of strategic solutions. But he said the company's commitment to reducing methane goes beyond the immediate bottom line.

"Our driver has been it's the right thing to do because it benefits the environment overall, and it benefits the future value of natural gas as a source of energy for the world," Hartstein said.

EDF's Watson, whose organization has worked with Southwestern to develop more accurate methods of measuring methane leaks, gives the company high marks for the sincerity of its environmental efforts.

"Southwestern for several years now really has been head and shoulders above its industry peers in terms of pursuing responsible development on a whole range of issues," Watson said. He cited the company's efforts to develop regulations to address well-integrity issues, which were linked to groundwater pollution, as well as its "freshwater neutral" policy aimed at reducing water consumption in fracking operations.

Southwestern was a founding member of a coalition called One Future, whose aim is to reduce total methane leaks in the gas supply chain — from production wells to the point of consumption — to less than 1 percent. Some estimates put the current amount at more than twice that level.

"People can rightly debate whether 1 percent is the right number, but the essential idea behind it is an admirable one," said Watson.

The One Future effort highlights a tug-of-war currently taking place in the hearing rooms where regulations are debated and written.

Companies such as Southwestern say they are eager to reduce methane leaks, but they say the goal would be better accomplished through performance standards that set overall targets for producers to meet, rather than regulations that spell out specific technologies or field practices they must follow.

On a tour of Southwestern's Conklin East well pad in New Milford Township, where the company operates six horizontal production wells, the company's Jordan recited a litany of the "administrative" requirements under the Pennsylvania Department of Environmental Protection's proposed methane rules that he said will add time and cost to its leak-detection surveys.

"I know the agency has its reasons for those particular elements, but I come back and say, from a standpoint of a smart program, let's implement things that really achieve reduction." he said. "Let's make sure we're going out and using the right technology to look for leaks."

Not all operators are like Southwestern Energy, said the Environmental Defense Fund's Watson, noting that until cost-effective gas-leak monitoring technology is in place, the rules need to be aimed at the least-compliant operators.

"We have thousands of oil and gas producers in the United States, and if I can point out the leaders to you on one or two hands, then we're not there yet," Watson said. "You have to have strong rules in place to ensure everybody is doing what they need to do to protect communities and the environment."