In 2017, a California homeowner refused to leave as the Creek Fire closed in; he and his son kept flames from reaching their house, which was left standing

Within minutes, a wildfire can alter the surroundings of a house. Strong winds and exceptionally dry conditions drove the Creek Fire through the foothills north of Los Angeles on December 5, 2017. Burning embers were carried ahead of the main fire and ignited secondary fires around buildings, endangering homes in and around Kagel Canyon.A neighbour warned Wood Grigsby, who had lived in upper Kagel Canyon for about 12 years, about the fire while he was asleep. When he got outdoors, he discovered that surrounding properties were already in danger and that flames were spreading throughout the canyon. In contrast to nearby properties, his house was somewhat protected. Grigsby had cleared brush around the house and replaced some vegetation with gravel, reducing the fuel immediately surrounding the property.As the fire advanced, Grigsby and his son started to move furniture off the porch and look for embers and spot fires. As surrounding homes burnt, they spent hours fighting tiny fires around the property. One house was demolished about 180 feet up the hill from Grigsby’s dwelling. The Creek Fire burnt 15,619 acres in Los Angeles County and destroyed 123 structures, including 60 homes, according to CAL FIRE figures reported the week it burned.How the fire came to the neighbourhoodThe blaze began at about 3:44 a.m. near Kagel Canyon, in the Angeles National Forest area, and grew during a time of extreme wildfire weather. in Southern California, when high winds may quickly spread fires through dry vegetation and carry burning material over the region. But for those who lived in the canyon, the threat wasn't only the main wall of fire. As foliage and structures were burnt, it generated embers that might be blown through the air and land on properties some distance distant. These embers can then spark fires in grass, leaves, landscaping material, fences or other combustibles.Those small fires matter because wildfire researchers have found that homes can catch fire through several different channels. A dwelling need not be located in the primary fire front. Research by the National Institute of Standards and Technology found that firebrands, or smouldering embers, can ignite mulch near a structure, depending on their size and number, airflow, and the moisture of the material. Researchers looked at firebrands, or smouldering embers, and how they can ignite fires in mulch near structures. Their investigations demonstrated that igniting depended on the size and number of firebrands, airflow and the moisture level of the material. Once the spark ignites a tiny fire close to a house, the risk might rise quickly. A burning piece of landscaping material could send flames to siding, decks or other combustible portions of a building.Why some homes did not burnOne big benefit Grigsby had before the fire came was that there was less flammable foliage just around the house. He'd cut the undergrowth surrounding the place and put in gravel instead of letting the plants grow right up against the building. So when embers landed, they had fewer fuels to catch fire with and travel to the structure. This form of planning is frequently referred to as constructing defensible space. The underlying principle is to eliminate as many flammable items around the house as possible, reducing the likelihood of the fire and embers coming into contact with the structure.A 2019 study by Alexandra Syphard and USGS scientist Jon Keeley, published in the journal Fire, offers wider context. The researchers analysed building inspectors' reports for more than 40,000 wildfire-exposed structures across California between 2013 and 2018, comparing homes that survived with those destroyed. Statewide, structural characteristics explained more of the difference than defensible-space distance did, though destroyed homes were over-represented in the dataThe most consistently important features were enclosed eaves, vent screens and multi-pane windows. These elements may reduce the chance of wind-borne embers entering a building. Multi-pane windows can also provide added protection from radiant heat. The authors also noted a limitation: many homes with more than 30 metres of defensible space or fire-resistant materials were still destroyed. That means no single preparedness step will ensure a house survives a big wildfire.Embers can convert a little fire into a house fire.Controlled wildfire studies further highlight the importance of material right adjacent to a home. In a separate NIST investigation, scientists tested several types of mulch beside realistic-scale building corners and exposed the area to showers of firebrands. The experiments found that firebrands could first create smouldering ignition in mulch, which could then transition to flaming. Under the tested wind conditions, flames from the burning mulch eventually ignited the adjacent building assembly.The results help explain why the few feet around a house can be so important in a wildfire. A fire doesn’t have to look like a single big flame front. An ember can fall on a flammable item, ignite it and then offer the following step towards the building. Grigsby and his son weren't trying to stop the fire; they were guarding against exactly this kind of ember ignition. But Grigsby's story is not to suggest that homeowners should stay and fight an advancing wildfire. Conditions near a fire can change rapidly, and skilled firefighters risk a lot even with training, protective equipment and communication systems.The greater lesson from his house’s survivalWhat made Grigsby’s experience remarkable was that his house survived as homes around him burnt. But the fact of one house cannot be reduced to one deed. The state of the property before the fire was significant. The house's structure was important. The wind direction and the severity of the fire also played a part, as did the behaviour of embers and the presence or absence of flammable material surrounding the structure.A USGS study supports that point. In their analysis, structural traits were a crucial factor in explaining which California homes survived. But the researchers also observed that the criteria they analysed could not account for all structural loss. Thus, Grigsby’s efforts during the fire represented only one part of the story. Vegetation clearance ahead of time to reduce fuel and gravel made a less flammable surface. Moving furniture away from the house removed another probable ignition source. The Creek Fire demonstrated how a neighbourhood can swiftly become a series of distinct fire environments. One property burns, while another adjacent one survives. An ember falling harmlessly on gravel can ignite a hazardous fire on dry grass or combustible landscaping.Their home remained standingThe bigger lesson is not that householders can safely fight a wildfire on their own. The wildfire survival starts before the flames arrive. Building design, ember resistance, vegetation management and removal of flammable debris can influence what happens when a wind-driven fire hits a town. Grigsby's house was one of those that survived, a reminder that a wildfire's effect on a home depends on more than whether flames reach the building.You use AI every day. Now get your AI Quotient. Take the AIQ test.