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SAN FRANCISCO — As wildfire season begins in Western landscapes that were covered in smoky haze for weeks at a time last summer, the federal government’s firefighters are exploring the use of small remote-controlled drones with infrared cameras that could map a fire’s size and speed, and identify hot spots, a particular danger.       

With a maximum wingspan of about 52 inches, the drones would supplement and perhaps replace manned surveillance aircraft, potentially reducing the risk to both pilots and firefighters.       

But the effort is being slowed by Federal Aviation Administration regulations.       

The use of drones in open airspace is regulated by the F.A.A., and its safety requirements effectively preclude unmanned aerial systems, or U.A.S.’s, from operating out of sight of a ground-based pilot. If distance or the smoke of a wildfire obscures a drone from observers on the ground, a piloted aircraft must be sent aloft to keep an eye on it.       

“In terms of federal regulations right now, we can’t use U.A.S.’s out there except on a very limited basis,” said Ron Hanks, the aviation safety and training officer at the federal Forest Service.       

Rusty Warbis, the flight operations manager at the Bureau of Land Management, said the process of approving individual trial flights was “cumbersome,” though improving.       

The evaluations by wildfire experts are part of larger questions on how to incorporate these aircraft, originally used for military purposes, into civilian missions. The drones could complicate the main mission of the F.A.A., ensuring the safety of the country’s airspace. And observers in Congress believe that inherent distrust of government and privacy concerns are also slowing the introduction of firefighting drones.       

Their potential usefulness, particularly their ability to pinpoint hot spots and fly in thick smoke that would ground other aircraft, was shown in an Alaskan fire nearly four years ago.       

The fire, which burned over 447,000 acres — roughly half the size of Rhode Island — northeast of Fairbanks, was generating so much smoke that no planes were permitted to fly overhead. But a drone belonging to the University of Alaska Fairbanks was launched and easily identified the extent of the blaze and its varying levels of heat.       

“The smoke was so thick no one was flying — that’s why they came to us,” said Rosanne Bailey, a retired Air Force brigadier general who is the deputy director of the Alaska Center for Unmanned Aircraft Systems Integration at the university. “We could fly and see the borders of the fire using infrared.”       

Kent Slaughter, the acting manager of the Bureau of Land Management’s Alaska Fire Service, said it took four days to get the F.A.A.’s approval for that flight in 2009; the process is now down to about 24 hours.       

But privacy concerns are slowing the integration of unmanned vehicles into the firefighters’ tool kit, said Senator Mark Begich, a freshman Democrat from Alaska. “Firefighting is a great example of how unmanned aircraft” are able “to determine the range of a fire, the intensity of a fire, without jeopardizing lives,” he said. “That’s a unique application, especially in my state, in Colorado, in California.”       

He called the delays in getting approvals for testing the craft “frustrating.” The reason cited most often by firefighting experts is the requirement that the aircraft be followed and monitored by a chase plane if ground observers cannot see them through smoke, or because they are flying into canyons in steep and rugged terrain.       

Les Dorr, an F.A.A. spokesman, said that safety in the air and on the ground is paramount and that the issue of line-of-sight requirements for drone use was being carefully studied.       

The Army has lent the Interior Department 41 small drone aircraft that have been used for environmental monitoring, including tracking migratory wildfowl.       

The Forest Service, part of the Department of Agriculture, has also been studying drone use for years. Mr. Hanks, of the Bureau of Land Management, said one question was how much value drones would bring to existing firefighting methods.       

“We are still developing policies internally, what the cost benefit would be,” he said. The drones, Mr. Hanks added, “would be competing against what we could do aerially against a helicopter or a light fixed-wing airplane.”       

John Gould, the aviation chief at the B.L.M., who along with Mr. Hanks is based at the National Interagency Fire Center in Boise, Idaho, had a similarly cautious perspective. “We’re trying to get them in the mix and put them out in the field to see the potential,” he said.