Fire Science Show

Soot is perhaps the most complex product of combustion, and at the same time one of the most profound for our everyday fire safety engineering. The topic of soot is not getting much love in the world of fire science, so I’ve chosen to give you a broad introduction to this subject. In this episode of fire fundamentals we will go through:

·         Soot creation from chemical perspective;

·         Soot creation from practical perspective;

·         Soot effects on radiation, toxicity and obscuration;

·         Extinction coefficient and specific extinction coefficient;

·         Soot yield and surrogate value of soot yield for complex fuels.

If you would like to follow up on this episode with some reading, I highly recommend:

·         Bart Merci and Tarek Beji book „Fluid Mechanics Aspects of Fire and Smoke Dynamics in Enclosures”

·         Jose Torero lecture “Prof. Jose Torero - Fire: A Story of Fascination, Familiarity and Fear” available at https://www.youtube.com/watch?v=cIY0litILRA&t=2082s

·         W. Węgrzyński and G. Vigne, Experimental and numerical evaluation of the influence of the soot yield on the visibility in smoke in CFD analysis – the paper with the source of our surrogate value of soot yield for complex fuels in fire safety engineering https://www.sciencedirect.com/science/article/abs/pii/S0379711217301327?via%3Dihub

·         G. Mulholland, C. Croarkin Specific extinction coefficient of flame generated smoke https://onlinelibrary.wiley.com/doi/epdf/10.1002/1099-1018%28200009/10%2924%3A5%3C227%3A%3AAID-FAM742%3E3.0.CO%3B2-9

·         W. Węgrzyński, P. Antosiewicz, J. Fangrat, Multi-Wavelength Densitometer for Experimental Research on the Optical Characteristics of Smoke Layers, https://link.springer.com/article/10.1007/s10694-021-01139-5

·         K. Börger, A. Belt, T. Schultze, L. Arnold, Remote Sensing of the Light-Obscuring Smoke Properties in Real-Scale Fires Using a Photometric Measurement Method, https://link.springer.com/article/10.1007/s10694-023-01470-z

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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.

In this episode of Experiments that Changed Fire Science we cover T. Jin’s experiments on the visibility in smoke – two experiments carried out in 1970 and 1971 in Japan that truly changed the way how we model fires and how we design fire safety in our buildings.

This episodes presents my recollection of Jin’s experiments, based on the published work – the seminal paper at the IAFSS in 1997 (https://publications.iafss.org/publications/fss/5/3/view/fss_5-3.pdf) and the original material published in Japanese in 1970 and 1971:

• Jin, T. (1970). Visibility through Fire Smoke (I). Bulletin of the Fire Prevention Society of Japan, 19(2).
• Jin, T. (1971). Visibility through Fire Smoke (II). Bulletin of the Fire Prevention Society of Japan, 21(1).

In the episode, I highlight the technical details of the experiments and their potential impact on the findings. I also present the overall model proposed by Jin, indicating the variables that influence it, and my recollection of how this model was implemented in modern fire safety engineering.

Further readings to this would be some of my papers:

• Węgrzyński, W., & Vigne, G. (2017). Experimental and numerical evaluation of the influence of the soot yield on the visibility in smoke in CFD analysis. Fire Safety Journal, 91(SI), 389–398. https://doi.org/10.1016/j.firesaf.2017.03.053
• Węgrzyński, W., Antosiewicz, P., & Fangrat, J. (2021). Multi-Wavelength Densitometer for Experimental Research on the Optical Characteristics of Smoke Layers. Fire Technology, 57(5), 2683–2706. https://doi.org/10.1007/s10694-021-01139-5

And a very recent paper by my collaborators from Wuppertal:

• Gnendiger, C., Schultze, T., Börger, K., Belt, A., & Arnold, L. (2024). Extinction coefficients from aerosol measurements. Fire Safety Journal, 146, 104110. https://doi.org/10.1016/j.firesaf.2024.104110

Please also visit episode https://www.firescienceshow.com/030-visibility-prediction-framework-with-lukas-arnold/ with my friend Lukas Arnold, on how we intend to change the visibility prediction in fire safety engineering!

This research was funded in part by National Science Centre, Poland in the grant OPUS 2020/39/I/ST8/03159.

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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.

Is evacuation of a community during a wildfire largely different from evacuation of a building? How much of the knowledge from the building fires is directly useful in planning and managing such an event, and what stuff is completely different? These are the lead questions for my today's interview with prof. Enrico Ronchi from Lund University and dr Max Kinateder from  National Research Council Canada. 

Both guests currently research the evacuation layer of the WUI problem – starting with the response of the endangered people, through choice of the mode of the transport, to solving the transportation models of such evacuations. A multilayered, multifaceted and interdisciplinary challenge, but one we need to have a good understanding of if we want to deliver good risk based, knowledge informed guidance for communities at risk.

In this episode, we got through their research pinpointing the difference between the building and a community evacuation. We touch the methods of research that are currently in used, and what kind of models they can inform. Finally, we get to talk about their recent experimental study during a fire drill in Roxborough Park, Colorado. This has literally happened a few days ago, and we can already discuss the challenges, and the first ‘anecdotal’ findings of the study.

Becoming open to the WUI problem and learning the challenges that are in front of us in this regard is critical to fire safety engineering, especially at the time when we observe Wildfire Safety Engineering becoming more of a real thing! I foresee that in future, a lot of us will work in the wildfire  prevention / mitigation/contingency space, and I hope you will appreciate the fact you’ve learned it first from the Fire Science Show! 

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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.

In the episode 10 of fire fundamentals together with David Morrisset, a nearly graduated PhD student from the University of Edinburgh, we explore the intricate dynamics of flame spread and its crucial role in fire safety engineering. David helps us differentiate between the two primary modes of flame spread, concurrent (imagine upward spread) and opposed (imagine downward spread), and explains how understanding these mechanisms can significantly enhance building safety and fire risk mitigation.

In this episode, we take a closer look at various materials like PMMA and timber and their unique fire behaviors. We also examine the complexities of flame spread on charring solids such as timber, discussing how pyrolysis and the resulting char layer influence heat transfer and flame behavior.

Lastly, we dissect the heat transfer mechanisms in various materials, from foams to solid slabs, and how factors like orientation and material properties affect flame spread rates. David highlights the balance between gas phase and solid phase heat transfer and the importance of precise modeling to predict flame behaviors accurately. 

Phemonena discussed here:

• flame spread definition
• concurrent vs opposed flame spread
• regimes of flame spread
• driving mechanisms of flame spread

Further reading: 

• Quantifying the controlling mechanisms of opposed flow flame spread: Influence of orientation, material, and external heating 
• Characterization of Flame Spread Over PMMA Using a Temperature Reconstruction Method
• The relative position of pyrolysis onset and flame front location for downward flame spread

And even though we did not have time to discuss diagnostics in the episode, you can check this crazy paper of David:

• Assessment and application of phosphor thermometry for spatially resolved surface temperature measurements during downward flame spread

Cover image: edited from Figure 1 in https://doi.org/10.1016/j.firesaf.2023.104048

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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.

With two Directors at NFPA - Michele Steinberg and Birgitte Messerschmidt, I'm trying to find an answer to a burning question - "what really is the WUI problem?" The WUI is not just a line on a map with an X distance from the forest... In this episode we try to define what it is, and who is in danger. Instead of our usual conversations looking into characteristics of burning forests, or seeking the impact of detailing in construction, in this episode we try to take a birds eye view and identify the problem across the scales and frameworks. From seeking out good definitions and their impact on policymaking, through technical solutions up to creating new testing and certification systems. 

So where are the answers? Actions across the scales at homeowner - community - regional levels, in which they are interconnected and optimal. A fireproof house in the middle of wrongfully managed area will not be of great difference… As well as a dangerous premise at the edge of the forest… The outcome of a WUI fire incoming will be an outcome of propper actions taken at every level.

We need new solutions. Scallable ones. We need better testing and standardization, new listings. We need to find ways to involve the private sector and create interesting pathways for fire safety engineers to work with people at risk, at whatever scale. The future looks promising, let's make sure we are a part of it. 

Some recommended resources I received from my eminent Guests:

• Impact of smoke in WUI fires: https://www.nfpa.org/en/news-blogs-and-articles/nfpa-journal/2024/02/13/research-column-spring-24
• Defining the WUI: https://www.nfpa.org/news-blogs-and-articles/nfpa-journal/2024/04/30/defining-the-wui
• Preparing homes for wildfire (home ignition zone): https://www.nfpa.org/en/education-and-research/wildfire/preparing-homes-for-wildfire
• The Firewise USA Recognition program: https://www.nfpa.org/en/education-and-research/wildfire/firewise-usa/become-a-firewise-usa-site
• Outthink Wildfire policy initiative: https://www.nfpa.org/en/Education-and-Research/Policy-and-Action/Outthink-Wildfire

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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.

• pressure inlets/outlets [open];
• velocity boundary conditions [vents];
• mass flow inlets;
• fans and HVAC models.

• heat transfer at walls;
• shear at walls.

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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.

A critical velocity episode... who would have thought? Even though I'm not an enthusiast of this approach, I have to admire the new science and researchers striving to improve it.

This week I welcome Conrad Stacey and Michael Beyer from Stacey Agnew to talk about their recent developments. We'll take you through the historical development of this concept since its inception in 1958, examining key variables like tunnel height and heat release rate along the way. We go into the Memorial Tunnel experimental project, and we discuss the context and the economic implications of recent updates to the NFPA 502 standards, exploring how changes in required ventilation speeds have impacted tunnel design costs and stirred controversy.

Conrad and Michael provide fresh insights into the complexities of tunnel smoke control, the distinction between critical and confinement velocities, and the significance of fire intensity in tunnel environments. Focusing on the historical Memorial Tunnel study, they explain the experiments that have been the source of our current models and how revisiting this data with modern CFD techniques allowed them to analyze this even further. With their newly proposed model for assessing critical velocity, the HRR of the fire is not considered as an important variable anymore, and replaced with the fire intensity (HRR Per-Unit-Area). This follows an observation that it is just the front of the fire that interacts with the incoming air, and thus making fire larger by making it 'longer' does not influence the outcomes - a new feature consistent with their newly defined model and Memorial Tunnel data.

You can read their study here: https://www.researchsquare.com/article/rs-4278205/latest

Some previous takes on the critical velocity by the team:

•  CRITICAL OF CRITICAL VELOCITY – AN INDUSTRY PRACTITIONER’S PERSPECTIVE 
• Critical velocity and the significance of the imminent retraction of 2020 NFPA 502’s Annex D critical velocity equations Part One
• Critical velocity and tunnel smoke control Part 2 - Filling the NFPA 502 void

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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.

What if you could predict the last possible time to evacuate your community before a wildfire wreaks havoc? What if you had that knowledge years before the wildfires happened and built up your preparedness based on this knowledge? What if you knew how this boundary changes with wind, dry weather and direction?  I think you get a knowledge-based decision model, and that is exactly what my guests today have been looking for.

Join us as we explore this cutting-edge approach with Imperial Hazelab Dr. Harry Mitchell and Nick Kalogeropoulos, who reveal the trigger boundary methodology developed within the WUI-NITY project. Their innovative work determines optimal evacuation timings by calculating an imaginary line where the time needed to evacuate aligns perfectly with the available time, thus ensuring safer exits. This episode promises to equip you with new insights into fire safety engineering that go beyond wildfires.

We take a sobering look at the dire consequences of delayed evacuations, spotlighting real-life tragedies like the 2018 Mati fire in Greece. Our discussion underscores the crucial importance of recognising imminent danger, addressing architectural hindrances, and improving inadequate road networks. 

In the episode, we discuss the first iteration - the Population Evacuation Trigger Algorithm (PERIL), a tool designed to establish robust trigger boundaries for more effective and timely evacuations. This was later developed into a probabilistic tool, with a significantly higher capabilities.

In the episode, we discuss the complexities of wildfire evacuation modelling, discussing how transitioning from single scenario studies to probabilistic models offers a more nuanced understanding of various parameters such as wind and fuel moisture. Operational fire models like Farsight are pivotal in predicting fire spread and smoke, balancing detailed physical models with actionable results. We wrap up by emphasising the necessity of integrating community resilience, fuel conditioning, and improved planning to mitigate wildfire tragedies, highlighting the collaborative efforts that make these advancements possible.

Further reading for this episode includes:

• Integrating wildfire spread and evacuation times to design safe triggers: Application to two rural communities using PERIL model
• Design of stochastic trigger boundaries for rural communities evacuating from a wildfire
• The simulation of wildland-urban interface fire evacuation: The WUI-NITY platform
• WUI-NITY Reports

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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.

Misconceptions in fire science are a strange thing. You present countless proof, publish research papers, and carry conversations, and yet… they live their own lives—spreading with no control and cluttering communication. One space is full of them—the fire safety of photovoltaic installations on flat roofs. In the Fire Science Show, we already had two very powerful episodes on PV—one with Jens Kristensen and one more recently with Reidar Stølen.

 In today's episode, we highlight a new guideline document published by the team at FRISSBE led by Prof. Grunde Jomaas. I invited Grunde to walk me through their document, and I took this opportunity to learn the origins, sources and inspirations for all the aspects they covered. The guideline takes you through ignition, fire spread, building roof construction and firefighting, giving a unique holistic overhaul of the topic. Most importantly, it is short, concise, and written in the most approachable way. This is a really good example of how communication in fire science should look. 

You can access the guideline directly here: https://www.frissbe.eu/upload/files/FRISSBE-ZAG%20BAPV%20Fire%20Safety%20Guideline%20May%202024%20v3.pdf

To complement this piece, you may also read this article on the background: Rus, N., Jomaas, G. (2024) PV guidelines – are the recommendations sufficiently evidence-based?

 As my personal recommendation, Grunde is a top communicator on LinkedIn, and you should follow him. He also runs a weekly newsletter, Burning Matters. I highly recommend this resource! 

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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.

Happy birthday, Fire Science Show! 

On the 3rd Anniversary of the podcast launch, I'm thrilled to deliver an episode on one of the most fascinating aspects of fire science - the compartment fire. Instead of going through the usual curriculum of the phases of fire, transitioning into flashover and flashover itself, I instead focus on the methodology's practical aspects. Which parts of the building have the largest impact on the fire? What is the impact of the opening? How much fuel matters? What happens in a large compartment, and how does it differ from a small one? Those are the sorts of questions I've asked myself while preparing for this episode, and the answers are hopefully in the episode.

In the episode, I highlight the essential contributions of key figures like Quintiere, Drysdale,  Kawagoe, Haramathy and Torero, whose pioneering work has shaped our understanding of fire dynamics. Listen as we dissect the impact of openings on fire behaviour, the role of materials, and the challenges of modelling complex fire scenarios, offering practical insights for fire engineers.

Reflecting on historical milestones and recent advancements, we also examine the travelling fire framework and its application in the structural analysis of large buildings. This episode emphasizes the significance of parametric fire curves and the need for an integrated approach to fire physics in engineering. 

If you would like to dive deeper, read:

• D.Drysdale, Introduction to Fire Dynamics (book)
• B. Karlsson and J. Quintiere, Enclosure fire dynamics (book)
• J. Torero et al., (2014) Revisiting the Compartment Fire

And two classics:

• T.Z. Haramathy, A new look at Compartment Fires Part I and Part II (1972)
• K. Kawagoe, Fire Behaviour in Rooms, Report of the Building Research Institute No. 27 (1958) - this one I do not have the direct link, so I will take a bit of a search.

Thank you for being with the Fire Science Show for 3 years! As we celebrate our commitment to delivering high-quality content every Wednesday, I look ahead with excitement and gratitude, dedicated to continuing our shared journey of learning and discovery in the fascinating world of fire science. Thank you for being part of our community, and here's to many more enlightening episodes!

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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.