What happens when the flames die down? It's a question rarely addressed in fire engineering, yet the decay and cooling phases of fires can be more dangerous than peak fire conditions. In this deep-dive conversation with Dr. Andrea Lucherini from Frisbee at ZAG in Slovenia, we uncover why these overlooked phases matter profoundly for structural safety.

Most engineers focus on protecting structures during the fully developed fire phase, but as Dr. Lucherini reveals, catastrophic failures can actually occur during cooling. We discuss a tragic case where seven firefighters died when a concrete structure collapsed, not during the fire's peak, but while they were extinguishing what appeared to be a dying fire. This sobering reality highlights how current testing methods fail to capture real-world risks—standard fire curves never decrease, creating a dangerous blind spot in our understanding.

The physics of cooling creates unique challenges for different building materials. Reinforced concrete might reach maximum temperatures in the steel reinforcement during decay rather than during peak fire. Steel structures face destructive tensile forces during contraction that can exceed the compressive forces experienced during heating. Mass timber presents particularly complex behaviour that may never truly enter a cooling phase without proper design considerations.

Perhaps most fascinating is how thermal boundary conditions transform as fires decay. When dense smoke thins, radiation patterns change dramatically, creating heat transfer scenarios that standard models fail to capture. These insights aren't just academic—they're essential for performance-based engineering approaches that prioritise realistic structural behaviour throughout a fire's entire timeline.

Andrea was kind enough to share these papers with me:

- Defining the fire decay and the cooling phase of post-flashover compartment fires: https://doi.org/10.1016/j.firesaf.2023.103965
- ⁠Thermal characterisation of the cooling phase of post-flashover compartment fires: https://doi.org/10.1016/j.ijthermalsci.2024.108933
- ⁠More information about FRISSBE project and team: https://www.frissbe.eu/ 

And I can shamelessly plug one of our own: https://onlinelibrary.wiley.com/doi/abs/10.1002/fam.2735

Cover image from experiments with Danny Hopkin that we have discussed here: https://www.firescienceshow.com/172-lessons-from-mass-timber-experiments-with-danny-hopkin/

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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 my personal view, an alarming truth about building fire safety lies in the gap between what's designed and what actually works in a building. After conducting 1000+ hot smoke tests in 200+ buildings, my experience is that most (maybe even 90%) of buildings had deficiencies in their smoke control systems, with 30% experiencing issues significant enough to potentially endanger occupants during a real fire. But it's not just about the problems. Good news - we have solutions.

Hot smoke testing stands as a powerful, yet underappreciated methodology that reveals what standard commissioning simply cannot. By creating controlled fires using methylated spirits and specialized smoke machines, we can observe how an entire building's safety ecosystem responds under fire conditions. The results are often eye-opening: systems operating in the wrong sequence, air flows disrupting smoke layers, pressurization fighting extraction, and critical components failing to activate when needed.

The most dangerous issue we encounter involves systems that don't "lock" to the first activated detector. This programming error causes safety systems to operate in areas far from the actual fire while leaving the fire location unprotected – a potentially life-threatening situation that's surprisingly common but easily fixable. Other frequent problems include excessive air velocity disrupting smoke buoyancy, extraction systems operating out of sequence, and auxiliary systems working against each other rather than in harmony.

What makes hot smoke testing so valuable is that it bridges the gap between aspirational safety (what designers intended) and actual safety (what the building delivers). Almost all identified issues can be corrected during commissioning, making this one of the most cost-effective safety investments possible. While the process may be disruptive and demanding, the alternative – discovering these failures during an actual emergency – is unthinkable.

Connect with me on LinkedIn to discuss implementing this approach in your projects and ensure your buildings aren't just designed for safety on paper, but truly deliver it when it matters most.

Recommended complimentary podcast episodes:

• https://www.firescienceshow.com/136-fire-fundamentals-pt-6-the-fire-automation-in-a-building/
• https://www.firescienceshow.com/033-science-theatre-or-engineering-polish-take-on-hot-smoke-test-with-piotr-smardz-and-janusz-paliszek/

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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 happens when we stick a thermocouple into a fire? The answer is surprisingly complex and has profound implications for fire safety engineering. In this deep-dive episode, Dr. David Morrisset from Queensland University joins Wojciech to unravel the science of fire measurements that underpins every experiment, test report, and dataset in our field.

The conversation reveals a critical truth often overlooked by practitioners: measurements don't capture reality directly - they capture the interaction between our instruments and fire phenomena. When a thermocouple reports a temperature, it's actually measuring its own thermal equilibrium, not necessarily the gas temperature we assume it represents. This distinction becomes crucial when using experimental data to validate models or make engineering decisions.

The hosts explore various measurement techniques - from temperature and flow measurements to heat flux gauges and oxygen consumption calorimetry - detailing their underlying principles, practical challenges, and hidden assumptions. David shares fascinating insights from his research, including innovative approaches to extracting meaningful data from noisy mass loss measurements and using high-resolution temperature fields to calculate heat fluxes without traditional gauges.

This episode offers essential context for anyone who reads research papers, interprets test reports, or uses experimental data in their practice. By understanding the nuances of how we measure fire phenomena, engineers can better evaluate the quality and applicability of experimental results, recognise their limitations, and ultimately make more informed safety decisions. Whether you're conducting experiments or applying their results, this conversation will transform how you think about the data that drives our field.

I've received a bunch of papers from David to share with you, here we go:

1. Data smoothing - particularly around things like the MLR. This is covered in many papers, and you can start with: https://linkinghub.elsevier.com/retrieve/pii/S0379711222000893
2. The "blue light method" was discussed in the podcast with Matt Hoehler from NIST - I came up with the same kind of effect but with PMMA (using black light instead of blue light) - https://doi.org/10.1016/j.firesaf.2025.104425
3. We did some work on characterising the thermal boundary layer generated by gas-fired radiant panels. https://doi.org/10.1016/j.firesaf.2023.104013 
4. In the flame spread work, I did use temperature data to approximate the heat flux acting at the surface 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.

The devastating 2018 Camp Fire in Paradise, California serves as a haunting reminder of how rapidly wildfires can overwhelm communities. We have not known anything like it - the flames raced through Paradise at four miles per hour, 30,000 residents had mere minutes to evacuate, and many couldn't escape in time. What happens when the fire goes worse than worst case scenario, but still people need to escape? How do we protect lives when escape routes are blocked by fire or gridlocked traffic?

Dr. Eric D. Link, NIST's researcher in the groundbreaking ESCAPE Project, takes us deep into these critical questions. The project's findings reveal how temporary refuge areas saved over 1,200 lives during the Camp Fire when people couldn't outrun the flames. These ad-hoc safe zones – parking lots, road intersections, and open spaces with reduced fuel loads – provided crucial protection when primary evacuation plans collapsed.

The conversation explores how communities can prepare for these worst-case scenarios by pre-identifying Temporary Fire Refuge Areas (TFRAs) throughout their neighbourhoods. Unlike traditional wildfire safety zones that require enormous clearance, TFRAs offer practical, achievable alternatives that acknowledge the realities of wildland-urban interface communities. The key insight? Even perfect evacuation plans can fail when fires move too quickly, so communities need backup options.

We also delve into the concept of "decision zones" for evacuation planning, the challenges of "no-notice fire events," and the potential for developing dedicated fire shelters that could protect large groups during extreme fire conditions. With climate change intensifying wildfire behavior and more communities at risk, these lessons from Paradise provide crucial guidance for protecting lives when evacuation isn't possible.

Read further on the ESCAPE project findings at the amazing NIST repository (in general, reading the NIST repository is a good life advice :)): https://www.nist.gov/publications/wui-fire-evacuation-and-sheltering-considerations-assessment-planning-and-execution-0

NIST dedicated webpage with more resources, especially for community managers: https://www.nist.gov/publications/wui-fire-evacuation-and-sheltering-considerations-assessment-planning-and-execution-0

Trigger boundaries podcast episode: https://www.firescienceshow.com/156-trigger-boundaries-with-harry-mitchell-and-nick-kalogeropoulos/

Cover image credit: On the morning of November 8, 2018, the Camp Fire erupted 90 miles (140 kilometers) north of Sacramento, California. By evening, the fast-moving fire had charred around 18,000 acres and remained zero percent contained, according to news reports. The Operational Land Imager on Landsat 8 acquired this image on November 8, 2018, around 10:45 a.m. local time (06:45 Universal Time). The natural-color image was created using bands 4-3-2, along with shortwave infrared light to highlight the active fire. Officials evacuated several towns, including Paradise. They also closed several major highways.
NASA, Joshua Stevens - https://earthobservatory.nasa.gov/images/144225/camp-fire-rages-in-california 

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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.

The world looks entirely different through a thermal camera lens, especially in a fire scenario. These devices reveal harsh temperature gradients between hot and cold surfaces, adding another dimension to how fire safety professionals understand and navigate dangerous environments.

Thermal cameras have transformed firefighting operations with astonishing effectiveness. Studies show that in smoke-filled buildings, thermal cameras have significantly improved the changes to identify victims. This technology dramatically reduces search times and increases survival chances, making it an essential tool for modern fire services around the world.

Martin Veit, who recently completed research for the Fire Protection Research Foundation, takes us deep into the science behind these life-saving devices. He explains how thermal cameras detect long-wave infrared radiation (7-14 micrometres) emitted by objects based on their temperature, creating images that reveal what smoke would otherwise conceal. The technology works because many combustion gases are relatively transparent in this part of the spectrum, giving firefighters a crucial advantage in zero-visibility conditions.

We explore the fascinating distinction between "measuring" precise temperatures (which requires understanding factors like surface emissivity and a bit of physics) and simply "observing" temperature differences (which can be sufficient for navigation and victim location). This distinction proves crucial when evaluating how thermal cameras should be tested and certified for firefighting applications.

The conversation delves into the challenges of current testing methods under NFPA standards, which sometimes yield inconsistent results that don't align with human perception of image quality. Martin's research investigates alternative approaches from the field of image processing that could provide more reliable and relevant evaluations, potentially improving both camera certification and opening doors to AI-assisted applications in firefighting.

Read the Martin's report here: https://www.nfpa.org/education-and-research/research/fire-protection-research-foundation/projects-and-reports/measuring-thermal-image-quality-for-fire-service-applications

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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.

The AI revolution has arrived, but fire safety engineers face a critical dilemma: how to leverage powerful AI tools while protecting confidential project data. 

Professor Ruggiero Rino Lovreglio from Massey University and Dr. Amir Rafe from Utah State University join us to explore the world of local Large Language Models (LLMs) - AI systems you can run privately on your own computer without sending sensitive information to the cloud. While cloud-based AI like ChatGPT raises serious privacy concerns (as Sam Altman recently admitted, user prompts could be surrendered to courts if requested), local models offer a secure alternative that doesn't compromise confidentiality.

We break down things you should know about setting up your own AI assistant: from hardware requirements and model selection to fine-tuning for fire engineering tasks. Our guests explain how even models with "just" a few billion parameters can transform your workflow while keeping your data completely private. They share their groundbreaking work developing specialized fire engineering datasets and testing these tools on real-world evacuation problems.

The conversation demystifies technical concepts like parameters, temperature settings, RAG (Retrieval-Augmented Generation), and fine-tuning - making them accessible to engineers without computer science backgrounds. Most importantly, we address why fire engineering remains resilient to AI takeover (with only a 19% risk of automation) while exploring how these tools can enhance rather than replace human expertise.

Whether you're AI-curious or AI-skeptical, this episode provides practical insights for integrating these powerful tools into your engineering practice without compromising the confidentiality that defines professional work. Download Ollama today and take your first steps toward a more efficient, AI-augmented engineering workflow that keeps your data where it belongs - on your computer.

Further reading: https://ascelibrary.org/doi/abs/10.1061/9780784486191.034

Ollama: https://ollama.com/

Hugging face: https://huggingface.co/

Rino's Youtube with guide videos: https://www.youtube.com/@rinoandcaroline

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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.

When experts from different disciplines attempt to collaborate on complex problems, such as evacuation modelling, we often discover that we're not speaking the same language. Even seemingly simple terms like "density," "velocity," and "distance" carry dramatically different meanings across physics, psychology, engineering, and computer science.

In this episode, we present the "Glossary for Research on Human Crowd Dynamics," a remarkable community effort that brought together over 60 researchers to create a shared vocabulary for those studying human movement in crowds. In this episode, I speak with two key contributors to this project: Professor Enrico Ronchi from Lund University, who helped organise the original workshop that spawned the first edition, and Ezel Üsten from Jülich Forschungszentrum, the corresponding author of the newly released second edition.

They reveal the fascinating process behind creating consensus among diverse scientific perspectives – from the intensive week-long workshop at the Lorentz Centre where the first edition was born, to the year-long online collaboration that produced the expanded second edition. We explore how the glossary handles controversial terms like "panic" (often misused in media and research alike), unpack the nuances of seemingly straightforward concepts like "fundamental diagrams," and discuss why the absence of citations was a deliberate choice to prevent territorial disputes.

What emerges is not just a practical resource for evacuation research but a blueprint for how scientific communities can build collective understanding across disciplinary boundaries. As we face increasingly complex challenges in fire safety engineering, this kind of "community wisdom" becomes invaluable. Whether you're a researcher, practitioner, or simply curious about how experts bridge communication gaps, this conversation offers rich insights into the power of shared language in advancing our understanding of human behaviour during emergencies.

And here is the link to the glossary: https://collective-dynamics.eu/index.php/cod/article/view/A189

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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 episode 17 of the Fire Fundamentals, we delve into the fire detection technology. Fire detection forms the critical foundation of all active fire protection measures, serving as the prerequisite for any fire safety engineering solution to work effectively. Following key points are discussed:

• Detection systems must balance sensitivity with reliability to avoid false alarms that disrupt building operations
• False alarms lead to serious business continuity issues and may eventually cause systems to be disabled
• Test fires methodology to assess sensor viability is discussed
• Optical smoke detectors use light scattering principles to detect smoke particles in their detection chamber
• Ionisation detectors utilise a small radioactive source creating an ionised environment in which an electrical current can be present, and gets disrupted by smoke
• Heat detectors operate based on absolute temperature thresholds or rate-of-rise measurements
• CO sensors complement other detection technologies to improve reliability and reduce false alarms
• Line detectors (both optical and heat-based) provide coverage for large areas like atria and tunnels
• Aspirating detection systems offer extremely early warning by continuously sampling air through pipes
• Future technologies include camera-based detection with AI processing and thermal imaging
• Strategies to reduce false alarms include multi-sensor devices, coincidence detection, and verification delays

Without detection, we're blind, and no automated systems may act—making fire detection critical for whatever application of fire safety engineering we implement.

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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 16th part of the Fire Fundamentals series, we invite Randy McDermott from NIST to join us for a deep dive into turbulence and its critical role in fire dynamics modelling. We explore the physics behind turbulent combustion and how it fundamentally shapes fire behaviour, plume dynamics, and simulation accuracy.

In this episode we cover:

• Defining turbulence as the enhancement of mixing and heat transfer through the creation of eddies and instabilities
• Understanding length scales in turbulence from the integral scale to the Kolmogorov scale
• Practical considerations when choosing grid resolutions for different fire engineering applications
• How turbulence models work in Large Eddy Simulation (LES) and what they represent
• Limitations of the D* criterion for mesh sizing and why higher resolution may be needed
• Differences between pre-mixed and diffusion flames in turbulent combustion
• Time scales in fire and the concept of Damköhler number in determining combustion behaviour
• Entrainment physics at the base of fire plumes requires centimetre-scale resolution
• Why turbulence modelling ultimately determines the accuracy of fire simulations

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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 podcast episode, I invited Chris Jelenewicz, the CEO of SFPE, to bring me up to date on the society. The SFPE Handbook on Fire Protection Engineering is undergoing a major revision with the sixth edition expected by summer's end, expanding to five volumes with significant new content on emerging topics like wildland fires and lithium-ion batteries. In this episode, we cover how the handbook is written, edited and when it will be released to the public.

Some highlights from the episode include:
• The new handbook will feature 11 sections, 104 chapters, and contributions from over 200 authors
• New innovative "living document" approach allowing updates without waiting for full revision cycles
• First-ever introductory chapter on the history and evolution of fire protection engineering
• Expanded content on wildland-urban interface fires, growing from one chapter to seven
• New chapters addressing lithium-ion batteries, fire safety during construction, and fire extinguishment fundamentals
• Multiple access options: print volumes, online subscription, and individual chapter purchases
• Available through university libraries via SpringerLink
• More global perspective with international contributions 

We have also discussed the incoming SFPE events, including the Annual Conference in Vancouver (October 2025), celebrating SFPE's 75th anniversary, a Storage Symposium at UL in Chicago (August 2025), and a Battery Symposium in Lisbon (November 2025).

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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.