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At the start of the year, local fire officials received a message notifying them of smoke in Woodside. But the alert didn’t come from a person who had seen a fire. Rather, a sensor powered by artificial intelligence sent it after detecting smoke from a road flare used by law enforcement during a traffic accident on Highway 280.
The sensor, also called an N5 sensor, had done its job: to detect a potential wildfire before it became visible to a person or a camera.
“You got the N5 sensor that is sensing with its nose basically,” said Woodside Fire Protection District Fire Marshal Kimberly Giuliacci. “So if we were to use our senses, our nose is working now.”
Fifty of these sensors were installed throughout Portola Valley, Woodside, unincorporated San Mateo County, Palo Alto and Stanford property last September to advance early wildfire detection on the Peninsula. The project is a partnership between the Santa Clara County FireSafe Council, the Department of Homeland Security Science and Technology Directorate, the Woodside Fire Protection District, Palo Alto Fire Department and Stanford University.
California’s fire season used to be considered from May to October. But the recent devastating Palisades and Eaton fires in Los Angeles, which killed 29 people and burned over 16,000 structures, exposed the severity of the state’s year-round hot and dry conditions due to climate change. Local authorities are educating residents and examining how prepared the Peninsula is for potential wildfires in every season.
Just this week, CalFire released newly updated fire hazard severity maps that show areas at risk of wildfire across the Bay Area. Parts of Woodside, Portola Valley, Redwood City and Palo Alto fall in zones considered high to moderate risk.
“We’re not in fire season …” said Giuliacci. “But it just goes to prove that these can happen any time, any day, any time of the year. Doesn’t matter if it’s hot or cold, raining, it doesn’t matter. And we have to start taking precautions and start doing what we can to increase the survivability of our neighborhoods and our communities as best as we can.”
How do the sensors work?
The N5 sensors are essentially smart gas monitors. They detect and evaluate smoke particles and send out an alert to local fire departments if the source of the smoke should be investigated further.
“The algorithms have become more sophisticated,” said Santa Clara County FireSafe Council CEO Seth Schalet. “So they can tell with a high degree of accuracy, you know, is it a wildfire or is it somebody’s barbecue or is it a chimney?”
Giuliacci said the Woodside fire district and N5 are considering training the sensors with controlled live fires “to build up its AI library, because we want to try to expose it to different types of scenarios so that it starts to learn more.”
Since their installation, the devices have detected smoke from a road flare and another from a prescribed burn, said Giuliacci.
The same sensors have been installed in Oakland as part of a two-year pilot program that started in 2023.
Where are the sensors located?
Experts note that nearly 90% of fires are caused by humans. Fires can spark from vehicles, unattended fireworks or discarded cigarette butts, for example. So the risk of wildfire is particularly elevated in communities where the natural environment and human development meet, according to Schalet. These areas are often referred to as the wildland-urban interface or WUIs.
The 2017 Santa Rosa Tubbs Fire, which killed at least 22 people and destroyed over 5,600 homes, as well as the January Los Angeles fires and the local 2020 CZU Lightning Complex Fires, all occurred in wildfire-urban interface areas.
“We consider right now anything west of 280 to be wildland-urban interface,” said Palo Alto Fire Department Fire Marshal Tamara Jasso. Giuliacci and Jasso said that the 12 N5 sensors in Palo Alto and 13 on Woodside Fire territory are in WUIs. They’re placed about one to two miles apart in each of the districts.
Jasso said the district placed sensors in areas that would benefit from early wildfire detection. She pointed out that Palo Alto land reaches all the way up to Skyline Boulevard. From July through October, a fire station at Foothills Park responds to incidents in the area. But the rest of the year, the closest fire station is at Hanover Street and Page Mill Road. The distance delays response times, so early detection is critical.
“Some of these sensors are in areas where we do not have homes,” said Jasso. “But if a fire were to start up there, we rely on people calling 911. And so what this sensor does for us is it possibly alerts us to a fire well before residents may become aware of it. And that way we can get that early alert and send resources.”
Giuliacci said locations were also determined based on factors like fuel vegetation and whether there are structures or residents in the area. One sensor was placed near the retirement community The Sequoias Portola Valley.
“That’s a big target hazard,” said Giuliacci. “We strategically placed one nearby so that we would get plenty of notice if something was happening to have time to evacuate that facility or handle how we did.”
While not all of the sensors have been placed in the WUI, those that are could be critical. Schalet pointed out that roads in WUIs tend to be narrow and there can be issues with residents evacuating while fire engines are trying to reach a fire and early detection can help. During the Palisades Fire, for example, Los Angeles County deployed bulldozers to clear roads of abandoned gridlocked vehicles to make way for fire fighting teams.
What comes next?
For the first year of operation, the sensors will be maintained by the Santa Clara County FireSafe Council. Afterward, the Woodside fire district and Palo Alto department will take over.
“As long as the sensors continue to work, I think it’s a valuable asset to this community and provides another layer of safety for the residents up there,” said Jasso, adding that for now, the Palo Alto Fire Department plans to continue using the sensors past the one-year mark, but that newer technology could one day replace them.
“I can foresee us using, if not this, you know, something in this realm of technology, because that’s really the direction of the future,” she said.
Giuliacci said she’s interested in how the sensors can be paired with other technology, like drones, to advance early wildfire detection.
“We’re just really grateful to be able to have this opportunity to try out something new,” said Giuliacci. “I mean, if it doesn’t work, it doesn’t work, but if it does, that’s just that much more amazing and beneficial.”
Joan Lane, trailblazing volunteer and Stanford’s go-to for ‘sticky problems,' dies at 97March 25, 2026 3:23 pm
Glad to read this article – very good idea to strategically place sensors to detect wildfire early. I hope the system proves to be reliable and accurate.
Important story. Thanks for keeping us informed, Magali!