263 - Developments in modelling WUI fires with Arnaud Trouvé

266 - Compartment fire framework with Vinny Gupta

A compartment fire is more than just “a fire in a room.” The moment flames, smoke, and heat are trapped by walls and fed through openings, the physics changes and so do the hazards we design for. We sit down with Dr. Vinny Gupta (University of Waterloo) to rebuild compartment fire thinking from the ground up, from what the enclosure does to airflow and smoke layers to why those effects still anchor modern structural fire safety. We trace the roots of today’s design tools through post World War II research and the foundational work of Kunio Kawagoe and Philip Thomas. That takes us straight into the ventilation factor, opening factor, and energy balance logic that underpins so much of compartment fire modeling, including parametric fires and many “golden number” rules engineers carry from project to project. Then we get honest about the fine print: the assumptions, the limits, and what gets lost when we remember the solution but forget the context it came from. From there, the conversation shifts to modern buildings that refuse to behave like classic small rooms: open-plan compartments, changing ventilation conditions, nonuniform smoke layers, and traveling fires that move across a floor plate instead of involving everything at once. We also dig into why fuel type can matter even when theory says it should not, especially once mass timber and CLT linings enter the compartment and amplify sensitivity to radiation, flow, and ventilation. If you would like to dig further, my recommendations are: * Kawagoe's summary of compartment fire research [https://publications.iafss.org/publications/fss/2/1/view/fss_2-1.pdf] * Jose Torero's revisiting compartment fire  [https://publications.iafss.org/publications/fss/11/28/view/fss_11-28.pdf] * Vinny's paper on mechanisms of flame spread in large compartments [https://www.scopus.com/pages/publications/85091887389?origin=resultslist] * Vinny's paper on different fuels and compartment fires [https://www.scopus.com/pages/publications/105033599024?origin=resultslist] ---- The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.

265 - How fires can lead to a nuclear winter? with Stephen Welch

As a kid of 80s and 90s, a lot of the pop culture was around the post-apocalyptic scenarios following a nuclear exchange. I always thought a nuclear winter is a consequence of atomic bombs falling down, but now as a fire researcher I've learnt it is mostly about fires, after all. Today I sit down with Dr Stephen Welch (University of Edinburgh) to trace the fire-engineering-heavy pathway from mass urban ignitions to firestorms, through soot production and its injection into the stratosphere, up to global climate impacts. The uncomfortable twist is that the energy release from the fires can dominate the scenario, and the climate outcome depends on whether a fraction of that smoke gets high enough and stays there long enough to matter. We dig into what makes a firestorm different from a big fire: the burned-area thresholds, the requirement for many structures burning at once, and the extreme winds a firestorm can generate on its own. Then we connect urban firestorms to what we’ve learned from megafires and satellite observations, including measured, non-zero global cooling effects, tracing reference datapoints that allow us to approximate the scale needed for a considerable climate impacts. That modern data from wildfires or volcanic eruptions becomes a rare validation anchor for a problem that historically relied on older assumptions and is inherently limited in terms of potential validation. From there, we go straight into the messy details fire engineers care about: fuel load density, modern plastics, under-ventilated compartment fires, glazing failure, and why soot yields taken from small, well-ventilated tests can be misleading when soot mass is the whole point. All of those, but considering large city fire at once. We also talk modeling options, from CFD to coupled atmosphere simulations, and why “consistent engineering crudeness” is sometimes the only honest starting point. In fact, we dive pretty deep into soot formation and modelling, as the classic "yield" approach we use for everyday fire engineering breaks down at scale of fires discussed here. At the same time, the exact amount of carbon injected into stratosphere is the number deciding of the final impact, therefore it requires a better justification. I am sure you will enjoy this conversation, as it ties multiple important aspects of fire engineering, tied all into a challenging and interesting research question. How do fires lead to a nuclear winter? ---- The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.

264 - Engineering Firebrand Showers with Samuel L. Manzello

A wind-driven ember shower is a key wildfire exposures a building can face, but we have not yet fully understood or accounted for them in making our communities wildfire resilient. Today we sit down with Samuel L. Manzello of Tohoku University and Reax Engineering to unpack how in the last 20 years the firebrand science went from not being able to characterize the features of them well to being able to procur controlled experiments and standardized generators that can actually shape building codes and product design.  We dig into what firebrands really are, why vegetation embers and structure-generated embers behave differently, and why lab tests with single particles often fail to explain the ignitions seen after major WUI disasters. From there, we follow the chain reaction that led to the Dragon firebrand generator: the need for wind, the lack of suitable facilities, and the breakthrough of creating a continuously feedable device that can produce repeatable firebrand showers. Samuel explains how airflow settings can shift firebrands from glowing to flaming, and why that control is essential for meaningful wildfire exposure testing.  The second half moves into standardization and real-world impact. Samuel breaks down ISO TC 92 and the work of the IAFSS LOFBE group on large outdoor fires in the built environment, including why the "Baby Dragon" became an ISO methodology and what it unlocks next: better roof tests, vent penetration tests, facade and opening vulnerabilities, and more consistent ways to compare hazards across regions and vegetation types. If you care about wildfire resilience, WUI fire safety, ember intrusion, and the future of practical standards, this conversation maps the path forward.  As promised, here are some links: * The world is burning: What exactly are firebrands and why should anyone care? [https://www.scopus.com/pages/publications/85146392511?origin=resultslist] * Progress in creating international standards [https://onlinelibrary.wiley.com/doi/10.1002/fam.3258] * Experimentally producing various firebrands [https://www.scopus.com/pages/publications/105017803607?origin=resultslist] * NIST - Dragon firebrand generator [https://www.nist.gov/blogs/taking-measure/fighting-fire-fire-breathing-dragons] (2014) * Samuel's classic paper from 2006 - on ignition of mulch with firebrands [https://www.scopus.com/pages/publications/32544455296?origin=resultslist] But there is much, much more in the literature on the firebrands! I recommend going to Scopus or Google Scholar and looking for Samuel's record there: https://scholar.google.com/citations?user=4oAvxXMAAAAJ&hl=pl&oi=ao ---- The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.

263 - Developments in modelling WUI fires with Arnaud Trouvé

Wildland-Urban Interface fires are a class of fires that deserves own models, own studies and a lot of research focus. This is what I discuss today with prof. Arnaud Trouvé from the University of Maryland, shortly before he has given his plenary talk at the recent Combustion Symposium in Kyoto. In this interview, Arnaud explains what makes wildland urban interface (WUI) fires and urban conflagrations so hard to predict, also with a focus on the combustion phenomena.  Arnaud is interested in how the fires spread from the wildlife into the urban areas, and how to model this spread. The state of the art models for fire spread are lacking in here, due to how they perceive a fire front as a "line", whereas in cities we are looking at collection of compartment-household fires that may last for hours, and create a burning area kilometre wide. Therefore, we need new modelling approaches, and we need them at three scales - the scale of vulnerabilities of a parcel, a parcel-to-parcel setups and whole community scales. To improve the state of the art, he breaks the problem into the scales that matter: indoor fire dynamics (where CFD can estimate structure burning), parcel-level exposure (where fire penetration is the missing link), and community-scale fire spread (where reduced order models dominate because fuel and building maps are often coarse). We dig into the practical modeling mechanics behind WUI simulators: 2D spread on gridded maps, simplified radiation and flame shape models, probabilistic firebrand transport, and the limits of one-way coupling where wind is prescribed but not influenced by the fire. We also discuss an important bottleneck: the data. Satellite observations often arrive with poor temporal resolution, and controlled full-scale experiments are rare, which makes validation and scenario selection painfully uncertain. We also discuss why windows and near-structure fuels can be a universal pathway for loss, and why the field needs stronger shared infrastructure and collaboration to move faster.  Congratulations on your plenary talk and thank you Arnaud for representing the fire community at the Combustion Symposium. Once Arnaud's plenary paper is published, I will update the show notes with a link! ---- The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.

262 - Fire Fundamentals pt. 22 - Optical diagnostics in fire with Elizabeth Weckman

In todays episode of fire fundamentals we talk with Professor Elizabeth Weckman from University of Waterloo about advanced optical diagnostics that let fire researchers read temperature, chemistry, soot, and velocity from light without relying only on probes. We break down what cameras, infrared imaging, spectroscopy, lasers, and PIV can reveal, plus the calibration and interpretation pitfalls that can quietly ruin your data.  Things covered in this episode: • why optical diagnostics are “non-intrusive” in practice and where they still perturb the flow  • limits of probe-based measurements in fire including spatial resolution and radiation errors  • using basic photography and video as a first diagnostic and as a planning tool  • calibration habits for cameras and why cheap, robust cameras are often a better choice for a fire laboratory  • infrared thermography for surface heating plus emissivity problems and practical coatings  • Schlieren imaging for density and temperature gradients and what it can and cannot imply  • point vs planar vs line-of-sight vs tomographic measurements and how “smearing” happens  • FTIR and absorption spectroscopy for pyrolysis gases, emissions, and toxic species  • chemiluminescence and laser-induced fluorescence to mark combustion and flame fronts  • Raman and CARS for temperature and concentration and why they are technically demanding  • soot diagnostics from light extinction to laser-induced incandescence and aging effects  • PIV basics, seeding challenges in fire, and what velocity fields unlock for validation  The episode is best enjoyed along Beth's paper from the IAFSS: Unravelling the mysteries of fire [https://www.sciencedirect.com/science/article/pii/S0379711226000640] ---- The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.