Figure 1. Contributing factors - urban conflagration
One of the most important new elements introduced in Wildfire Risk Extreme is urban conflagration modeling. An urban conflagration occurs when a fire, started most commonly by wildfire, but sometimes caused by structure fire, burns primarily from structure to structure without being propagated by the combustion of wildland fuel.
The Urban Conflagration composite group is comprised of Structure Threat and House to House Threat.
Figure 2. Urban conflagration modeling
Bluish-green areas in the image above are urban conflagration-only areas. Areas in purple are subject to urban conflagration and ember/flame impingement. These two zones make up the interface zone.