The insurance plans provide teams made up of former firefighters with Cal Fire, the U.S. Forest Service and local fire departments to work with homeowners on ways to prevent wildfires from damaging or destroying their properties. The units suggest changes to landscaping and reduce brush near houses "so the home has the best possible chance to withstand the encroachment of a wildfire," Poux said.

Those teams also rush into neighborhoods as wildfires are beginning to threaten homes of customers with the wildfire coverage. The private crews move wood piles and barbecues away from homes, take out foam cushions from patio furniture, remove leaves from gutters and trim branches from nearby trees. They also set up sprinklers and apply fire retardant chemicals directly to the buildings.

But just because a home is covered by the wildfire coverage doesn't necessarily mean it's saved.

Chubb's wildfire teams visited the homes of more than 250 policyholders in the recent Northern California wildfires, according to company spokesman Jeffrey Zack. The group worked to protect more than half of those properties, Zack said in an email. At least nine of those properties were saved, but Zack did not disclose how many homes were damaged or lost.

"That means but for the actions taken by Chubb, the homes would have been lost," Zack said.

PURE's wildfire risk team "took action" on more than 100 properties owned by its Northern California customers during last month's blazes, Scott Spencer, a senior vice president of risk management at the company, said in an emailed statement Tuesday.

The team applied fire retardant to 30 percent of those properties that were in the direct path of fire, Spencer said.

"While a handful of homes were structurally compromised, the majority of the homes PURE served were saved due to the efforts of these crews," said Spencer.

AIG had multiple teams in the area that visited several hundred homes, but the company would not release specific data on how many were saved.

At least one insurance company, USAA, offers the service to policyholders, regardless of the value of their property.

The industry emphasizes that its insurance wildfire units are not firefighters. "We do not respond to structure fires. That's the job of the fire departments," Poux said.

Cal Fire says the presence of wildfire insurance units in big wildfire situations is increasing.

"We're seeing more during these major events, and more so within Napa and Sonoma counties," Cal Fire spokesman Scott McLean said.

The wildfire insurance teams are required to get permission from state fire officials to enter areas threatened by blazes, according to McLean, who added that the groups have to wear protective equipment and provide documents associated with their companies and the homes they plan to check on.

"They can come when there's an evacuation advisory or warning. However, when that turns into an evacuation order to leave, they must leave," McLean said.

In general, Cal Fire wants the insurance company fire crews to stay in their lane.

"If they're doing their job and taking fuel away from that fire, sure, that's a help," McLean said. "But ... they need to stay on that property and take care of what they're supposed to do. If they leave ... and start going around the fire area, then no, they cannot do that."

State regulators are aware that some insurance companies offer extra wildfire protection but they do not have a full grasp of how prevalent the fire risk units are, according to Nancy Kincaid, press secretary for Insurance Commissioner Dave Jones.

"While it is part of a company's rate/form filing, we do not track them or keep data on how many companies offer this type of coverage," Kincaid said in an email.

One consumer advocacy group wants the industry to spread the service around to more consumers.

"Insurance companies have the knowledge, they have access to the technology and they have access to resources to make homes more resistant to damage," said Amy Bach, executive director of United Policyholders.

"We want them to use that knowledge to benefit their policy holders, not just the few, but the many," Bach said.

Editor's Note: A PURE representative had told KQED previously that the company's wildfire risk team visited 81 homes in Northern California during last month's blazes and three of those houses were destroyed. But, the company issued a revised statement on Tuesday.