Imagine that ranchette in the back country. There sits an olderdead car, perhaps a well house with the broken door hanging open and unmanaged vegetation throughout the yard, this could burn and heat conduction would occur upon the home.

RADIATION: Heat close enough to cause if not the structure, but "Stuff" around the structure as well as combustible vegetation to ignite and communicate to the structure. An example of this is a Canyon community in a tight well heated Canyon. Imagine homes close together burning one after another in absence of fire suppression actions. Radiation will occur first followed on by conduction.

SPOTTING: Where embers create "new point source ignitions" creating in effect, new fires that impact the stuff, vegetation and structures. Is this then correctly an ember fire? Or actually an ember caused fire leading to radiation, then conduction? What led to the actual attack of fire upon say, the house.

And EMBERS, Embers are a significant threat to property that is not hardened and without defensible space. Under extreme conditions these embers occur pre-fire front passage, during the front passage and really significant for hours after the fire front passage. These continue an "Ember Attack" from distant and most significantly from nearby burned combustible vegetation (Vector) to the let's say house, combustible ornamental vegetation and stuff, (Receptor). With extremes in Wind, Topography and Fuels driven fires, this ember creation becomes much more prevalent and when combined with single digit humidity's and low fuel moisture’s can become quite challenging.
However, most of our firefighting is on fires, or portions of fires not exhibiting extreme fire behavior. And it is here, that in absence of firefighters or homeowners with defensible space where houses can either stand alone or not, having the necessary separation from fuels, be damaged or destroyed.

Think of holding a stick up out of the campfire and blowing air over it, and seeing the sparks or embers. The further the stick (vector) from the receptor, the fewer chances of a successful ignition.

I am very careful to make a declarative statement about what caused a specific house to burn without approaching it in a forensic fashion. This was done to my satisfaction with a recent report of the Trails in Rancho Bernardo. Where most houses lost, were in direct contact with combustibles. Later Ember Attack from structures and unmanaged combustible vegetation led to further loss. This was not done to my satisfaction in the Witch Creek Fire Report.

Defensible Space allows firefighters when safe, "maneuver room" necessary for their success.

So really, in most fires you are seeing several methods of fire attacking a structure or a group of structures and these are related to available fuel, topography, where the structure is located, structural resistance to heat transfer, adjoining structures, weather=wind, temperature and humidity. Defensible Space maintenance, as well as reducing combustibles including stuff and vegetation.

In County damage assessments, the vast majority of the homes within the perimeter of the mega fires of 2003 and 2007 did not burn even though they represented all kinds of age groups and types of construction. Were there no embers there? Or....was it a combination of factors that weren't present on a site by site basis that did not allow the home to burn. So understand my reluctance to rely only on what I see as an unsophisticated determination of fire cause rather than my full Monte suggestion.

I find it intellectually and scientifically dishonest or at least naïve when any particular advocate group starts to advise homeowners that fuels management is less important than "Hardening Structures". Or, managing combustible fuels will lead to an invasion of non-native invasive species, without admitting this has already happened over a long history of Spanish, Mexican and American agriculture and wildfire history over a period of 240 years. This then I know, that they lack awareness and experience of the whole
(Bigger picture).

You’re wondering as to my qualifications to report on this? I am a wildland fire chief officer, have 38 years of wildland and structural fire experience. Am a Type III Incident Commander (Multiple Resource-Extended Attack). Even though I prefer the line command, as Division Supervisor most often. Am certified as a California Firefighter I&II through Certified Fire Officer. Have an AS in Fire Science, additional Fire Management, Personnel Management, Upper and Lower division credits. Have a Fire Science Teaching Credential. Obviously have passed innumerable NWCG Courses as well as taught them. Additionally have 36 units of Upper division credits in Biological Science and Environmental Studies.

Mitigator