Drone aircraft are starting to monitor chemical leaks from the skies above Louisiana.

The state Department of Environmental Quality bought its first unmanned helicopters last year and began sending the equipment skyward in October, once the first five pilots completed training.

The fleet includes three Yuneec H520s, a sturdier DJI Matrice 210, and a handful of smaller training quad copters, officials said.

The agency is still trying to figure out how exactly the drones will be deployed, both in routine monitoring and during emergencies.

"We think that it has a lot of potential for us. ... (A drone) is not going to bleed; it's not going to breathe in hazardous atmospheres," said Jeff Dauzat, administrator of the department's Emergency and Radiological Response Division.

Each unit is equipped with a normal camera and an infrared camera, which senses heat. Dauzat said he would eventually like to outfit the drones with chemical monitoring devices.

So far, the most noteworthy deployment came in April during French Quarter Fest, when a ship struck a pier and leaked about 4,200 gallons of oil into the Mississippi River. Having an eye in the sky gave responders a better perspective and helped them determine how to contain the spill, Dauzat said.

The drones have also monitored releases from fuel tanks and 18-wheeler rollovers, he continued.

The thermal imaging can be used to find fires or leaks of clear gases, said drone pilot Jason Smith, manager of the unmanned aircraft program. He estimated he's flown about two dozen missions so far.

Smith is based in Baton Rouge, but other pilots will be placed in Lake Charles and New Orleans, with eventual plans to expand to Monroe, Pineville and Shreveport.

Right now, the unmanned craft generally respond to emergencies, but the Department of Environmental Quality wants to use the equipment in regular monitoring. Pilots do not currently fly over sites without permission.

The department is still trying to answer legal questions, like whether the drones can fly into the airspace over petrochemical plants, which have special security concerns, press secretary Greg Langley said.

"There's not a lot of precedent in the legal system," Smith said.

Companies sell equipment that measures volatile organic compounds and other chemicals. The drones could take readings similar to the ones human monitors record with handheld units, Dauzat said.

Companies like Marathon already use drones to look for leaks, Langley pointed out.

Dauzat doesn't expect drones will ever fully replace human regulators, but they'll help stretch the agency's capabilities as the department deals with staffing cuts, he continued.

Each H520 costs about $4,500 to buy and equip. M210s can be 10 times more expensive, but they have better cameras and can fly for longer and in rain, and in areas with abundant radio interference, Smith said.

While State Police and the state fire marshal have their own drones, the Department of Environmental Quality could use its equipment to help other law enforcement investigations, Langley said. It remains to be determined how long large photos and video files would be stored and available to the public, he said.

However, officials are excited by the prospects of the new program, especially if the drones can be harnessed for regular monitoring as well as emergency response.

"As a state agency, we're on the cutting edge by having a program. ... It's a brave new world," Dauzat said. "The possibilities are endless. ... The sky's the limit."

Follow Steve Hardy on Twitter, @SteveRHardy.