Michael Gollner

New paper out in Fire Technology: Wind-Driven Building-to-Building Fire Spread: Experimental Results and Probabilistic Modeling. 23 metal and wooden sheds were ignited and exposed a full-scale structure in the large wind tunnel at IBHS, defining exposure for the first time: rdcu.be/e1fNM

Specifically, these figures are intended to show how destroyed versus survived structures are distributed across standardized flame and ember values. They are not intended to represent mitigation effects, nor to infer causal impacts of Zone 0 clearing or home hardening.

The kernel density estimates were applied solely for visualization purposes, to illustrate the empirical distributions of flame and ember exposure associated with the number of destroyed structures.

The standardized flame length and ember variables shown in the PDFs were not used as inputs to the machine learning models in the form of KDEs.

If homeowners let dead plant material accumulate in Zone Zero, "then it makes sense that there shouldn't be any plants in Zone Zero," Max Moritz @ucanr.edu told @lsommer.bsky.social
"Having a well-watered plant is less of a risk, but it's not no risk," says @gollnerfire.bsky.social

It’s an important reminder of just how quickly fires can grow into a destructive force when given the opportunity, and why the sometimes onerous fire safety codes and standards exist.

It’s too early to know what confluence of factors occurred here; however, hopefully we can again learn from this tragedy to prevent another.

Initial reports highlight several potential (but unconfirmed) issues that could have played a role, such as the use of open flames (sparklers), flammable wall/ceiling coverings (especially foam), inadequate evacuation plans/exits, etc.

There is a tragic history of nightclub/bar fires that have shaped our codes and standards (e.g. Cocoanut Grove, Station Nightclub, etc) and if codes are followed tragedies are often preventable.

Switzerland ski fire latest: Around 40 people confirmed dead and 115 injured Many young people are believed to be among the victims; one student tells the BBC he arrived at the bar expecting to celebrate, only to find a scene of chaos.

Tragedy in Switzerland with over 40 dead and over 100 injured in a fire in a bar. We don’t yet know the official cause, however these tragedies occur due to a chain of failures rather than just one spark.

www.bbc.com/news/live/c8...

It’s an important reminder of just how quickly fires can grow into a destructive force when given the opportunity, and why the sometimes onerous fire safety codes and standards exist.

It’s too early to know what confluence of factors occurred here; however, hopefully we can again learn from this tragedy to prevent another.

Initial reports highlight several potential (but unconfirmed) issues that could have played a role, such as the use of open flames (sparklers), flammable wall/ceiling coverings (especially foam), inadequate evacuation plans/exits, etc.

There is a tragic history of nightclub/bar fires that have shaped our codes and standards (e.g. Cocoanut Grove, Station Nightclub, etc) and if codes are followed tragedies are often preventable.

Switzerland ski fire latest: Around 40 people confirmed dead and 115 injured Many young people are believed to be among the victims; one student tells the BBC he arrived at the bar expecting to celebrate, only to find a scene of chaos.

Tragedy in Switzerland with over 40 dead and over 100 injured in a fire in a bar. We don’t yet know the official cause, however these tragedies occur due to a chain of failures rather than just one spark.
www.bbc.com/news/live/c8...

Maintaining “defensible space” around a home is an effective way to prevent embers from sparking a structure during a wildfire, said @gollnerfire.bsky.social

“This is one of the cheapest and easiest things that you can do that has any immediate and measurable impact,” Gollner said.

2025 Los Angeles County Wildfires

Important new report from @ibhs.org on the LA Wildfires. Continuing to provide evidence on the importance of mitigation within the entire community. What helps homes avoid damage?structure separation, reduced connective fuels, and the use of resilient building materials. ibhs.org/lawildfires/

We’ve created an entirely open source model for WUI within ELMFIRE. www.sciencedirect.com:5037/science/arti.... It’s Fortran, not ready for easy use but documented and free

Three fuel models for predicting urban fire spread – a stopgap for emergency management in the US Predicting wildfire spread in cities and towns is limited by models that define urban as unburnable. Here, fuel characteristics are identified to best matc

connectsci.au/wf/article/3...

Only in the 1-3% of times that actually matter ;-). Hard to know what parts of the model are right or wrong when so much tuning takes place to match limited validation data. Still, very useful tools when used appropriately

Urban models are more point source (though not always modeled that way) in that houses burn a long time and spew embers far and slowly burn along blocks and often spot across blocks.

Hard to answer. If you use Behave plus you can see for different fuel types where the spread rate levels off, that’s essentially a limit for Rothermel data. But spotting really starts to dominate, and isn’t well modeled.

A paper recently came out on this, but fundamentally homes burn by different physics and requires a different model for urban areas

Dec 3 at 4pm PST I'll be giving a talk to the Contra Costa Resource Conservation District entitled "Exploring Effective Mitigation Measures and Drivers of Structure Loss in California’s WUI." We will cover mitigation measures and evidence to reduce structure losses.
ccrcd.org/events#:~:te...

Yeah even wet plants burn. We did a test with berkeley fire to show it and presented to the board of forestry. They’re better, for sure. Catching embers might be bad if they do…. Pile of embers at base of plants is hazardous

This even more so! 34c031f8-c9fd-4018-8c5a-4159cdff6b0d-cdn-endpoint.azureedge.net/-/media/bof-...

Yes! We didn’t separate zone zero until the review process when it was asked, so it’s not a major highlight in the main body. But it is in my talks!

A strong background in heat transfer, fluid mechanics, and experimental or numerical techniques is expected. Full details on how to apply is here.
firelab.berkeley.edu/available-po.... Email Prof. Gollner with your interest before the deadline. Note very limited international funding is available

I will be recruiting 1-2 new PhD students next year. Areas of interest include experimental fire research focused on flame spread, ignition, flammability or emissions of wildland or urban fuels and modeling the spread of fires through the wildland-urban interface.

California’s fire safety push clashes with an L.A. icon: Bougainvillea State officials are preparing rules that would bar planting flowers like bougainvillea within five feet of buildings in some areas to reduce wildfire spread.

www.washingtonpost.com/nation/2025/...