AIG is not alone in offering premium service for higher premiums. Several companies, including Chubb and Fireman’s Fund, will help prepare homes in advance of wildfires by creating plans for clearing the kind of brush and branches that become fire fuel and, for a fee, sometimes hiring contractors to do the work. Insurers provide similarly specialized service to limit damage from hurricanes, such as specifying what kind of shutters a house should have and which valuable furnishings should be moved where in the event of flooding and quickly coming out to cover damaged roofs.

But out West, AIG is taking special treatment to a new level. It has a contract with Firebreak Spray Systems to deploy crews to apply retardant wherever policy holders are threatened by wildfire. This year, the fire season has been so busy and widespread that Firebreak has had to subcontract work in Idaho to Mr. Futral, a distributor of Phos-Chek, the fertilizer-like retardant Firebreak uses. Firebreak and Mr. Futral also install permanent sprinkler systems that can be activated remotely, even by cellphone, to spray retardant on homes when their owners are away.

The Phos-Chek used by the companies is clear, but Firebreak says it is chemically similar to the red-dyed retardant wildfire crews have been dropping on parts of Bald Mountain and the Sawtooth National Forest since the fire, known as the Castle Rock fire, broke out last week. The fire has expanded to about 25,000 acres, though part of the increase is because of “burn-back” efforts to keep fire from reaching populated areas. So far no structures have been lost.

Jeanne Pincha-Tulley, the incident commander with the United States Forest Service who was overseeing the crew of 1,300 that was fighting the fire over the weekend, is based in fire-prone California and said that in three decades of firefighting she had never heard of an insurance company showing up to spray retardant on homes while a fire is threatening.

“That’s a first, I have to admit,” Ms. Pincha-Tulley said. “But that’s the kind of affluence there is here.”

Mr. Futral said he and an employee expected to treat 40 or more of the approximately 200 houses that AIG Private Client Group insures in the area, and that his list was growing rapidly as people had heard about the service or simply seen neighbors being given the treatment.