Fire Science Show

Jumping straight to CFD has become the default move in fire safety engineering, but that habit can quietly weaken our work: more inputs, more assumptions, more ways to be wrong, and often no clearer link to the actual design question. We sit down with Craig Hofmeister and Brian Klein to unpack a practical, defensible way to choose the right fire model for the job using the SFPE guideline “Substantiating a Fire Model for a Given Application.”

The broad framework of this work is to define the phenomena of interest and questions at hand, then choose the candidate models and evaluate them through set of core qualities, then address the verification and validation of the models, consider uncertainties and user impact, and finally document the whole process.

We walk through the framework step by step, starting where good performance-based design always starts: the questions the model must answer. From sprinkler and detector activation to atrium smoke control, pressurization, visibility and tenability, we talk about translating objectives into key physics and required outputs. That sets up a grounded comparison across hand calculations and algebraic correlations, zone models like CFAST, node network tools like CONTAM and Ventus, and field models like FDS built in PyroSim.

From there, we get into the part many projects rush past: verification versus validation, how to use published V&V evidence (and when you are outside the validated scope), and how uncertainty and user effects should shape your confidence. We also address real-world constraints like AHJ expectations and contract requirements, plus practical tools like sensitivity studies, bounding analysis, and grid sensitivity checks to keep complexity from turning into false precision.

If you want a cleaner way to defend your modeling decisions to reviewers and stakeholders, this conversation gives you a repeatable process you can build into your own practice.

----
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.

“Two people per parking space” is one of those default fire engineering inputs that we are very used to place into a model without really thinking much of it. But it is one of those defaults that show a huge richness once you dig deeper. Are all parking spaces taken? Are people in their cars? What are they doing? How long have they been there concurrently... We take that simple rule and pull on the thread until it turns into a full conversation about evidence, uncertainty, and what “credible maximum” should mean when you are designing for real-world risk.

Dr Mike Spearpoint from the OFR joins me to explain how occupant load values end up in codes, why they are so hard to interpret, and why “maximum possible” can push designs into unrealistic corners. Then we get practical: we build a static, risk-based method for car park occupant load using distributions for car park utilisation and people per vehicle, run it through Monte Carlo simulation, and talk about selecting percentiles like the 95th or 99th for design. If you work with evacuation analysis, performance-based fire engineering, or fire safety assessment, this is the kind of reasoning you can reuse anywhere.

In his consideration, Mike reaches something he calls the dynamic model: people are only briefly “in the car park” as they park, unload, walk to the destination, and leave. Because published data on “around-the-car” activity time is scarce, Mike measures it directly using public CCTV observations and turns it into a usable distribution. 

Why did he do this? This is a part of a larger project on adequate fire resistance periods in car parks. We also connect utilisation to vehicle-to-vehicle fire spread and why those assumptions can ripple into design fires and structural fire resistance decisions for open-sided car parks.

If you are looking for the report itself with all the details, look here: https://www.gov.uk/government/publications/fire-safety-open-sided-car-parks

I'll make it easy for you, it starts at page 218 ;)

----
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 fire strategy can be technically correct, but if the team building the building never truly understands it - goals and objectives may be missed. For the 250th Fire Science Show, we slow down and talk about the craft of communicating fire science to construction professionals so that the intent survives real projects, real deadlines, and real handovers. 

This episode is an extended version of my talk I gave recently at the IAFSS Research Sub-Committee Workshop, which we have organised with Felix Wiesner, and I had a chance to talk along my friends - prof. Guillermo Rein, Birgitte Messerschmidt and dr Steve Kerber.

In this episode, we share why the biggest failures are rarely tiny compliance misses. The scary failures come from misread strategy, missing execution on site, and teams optimizing for the wrong target because we explained the “what” but not the “why.” From smoke zoning misunderstandings to the way product labels and ratings get interpreted, we unpack how simple miscommunication can create life-threatening conditions even when everyone is working hard.

Then we offer a practical framework built around three ideas: context, timeliness, and the way we speak. Context means understanding the building ecosystem: code and local planning, sustainability and energy efficiency, LEED or BREEAM certification pressures, business model realities, and aesthetics. Timeliness means matching our message to the building lifecycle, keeping high-level objectives clear early on, translating them into technical concepts during design, and only then driving into the technical detailing that makes compartmentation, egress, smoke control, and structural fire safety real. Finally, we get honest about what works: simple anchors like ASAT versus RSAT, consequence-focused language, and respectful collaboration, plus what breaks trust fast: jargon, paper-style writing, megawatt talk, and false certainty around “60 minutes” ratings.

Some other podcast recommendations after this one:

• https://www.firescienceshow.com/136-fire-fundamentals-pt-6-the-fire-automation-in-a-building/ what happens in a building during a fire?
• https://www.firescienceshow.com/246-fire-fundamentals-pt-20-fire-resistance-criteria-with-piotr-turkowski/ a wider view on the fire resistance
• https://www.firescienceshow.com/199-commercial-timber-guidebook-with-danny-hopkin-and-luis-gonzalez-avila/ commercial timber guidebook which is an example of excellent communication of fire safety concepts.

----
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.

From the SFPE Performance Based Design Conference in Singapore, we sit down with Jonathan Hodges and Mark McKinnon (UL Research Institutes) and Christian Rippe (Jensen Hughes) moments after their case study presentation to break down a modern parking garage fire engineering workflow with a huge does of performance based and probabilistic approaches.

We talk about what changes when today’s vehicle fleet makes multi-vehicle fire spread more plausible, and why picking a single car fire curve can quietly bake bias into an entire performance-based design. The team shares how they use real incident data, vehicle size distributions, ignition location categories, and percentile-based heat release rate curves to build design fires that are transparent and defensible. We also dig into EV charging as an initiating mode, what the data can and cannot support, and how a “gap analysis” mindset helps practitioners avoid false precision.

Then we get into the risk machinery: scenario binning, frequencies, sprinkler reliability assumptions, and how CFD (FDS) fits when you cannot simulate 100,000 possibilities. Finally, we go structural with concrete spalling, thermal finite element modeling in Abaqus, and a scripted workflow that iteratively removes damaged concrete to understand how exposure evolves during long-duration multi-vehicle fires.

For this episode, there is a ton of resources. From Jonathan:

1. Reference for first design fire paper: https://doi.org/10.1016/j.firesaf.2024.104145
2. Reference for second design fire paper: https://doi.org/10.1016/j.firesaf.2026.104721
3. Reference for database paper: https://doi.org/10.1007/s10694-025-01701-5
4. Reference for number of parking garages: https://doi.org/10.1016/j.firesaf.2022.103565
5. Reference for ULRI vehicle fire data: https://doi.org/10.1016/j.dib.2026.112471
6. Reference for ULRI material database: https://materials.fsri.org/
7. Reference for NERIS: http://neris.fsri.org/
8. Reference for NFPA Vehicles data: https://www.nfpa.org/education-and-research/research/nfpa-research/fire-statistical-reports/vehicle-fires

And two from myself:

1. Outcomes of the massive fire with spalling in Warsaw https://doi.org/10.1016/j.firesaf.2025.104352
2. Open sided car park report by OFR https://www.gov.uk/government/publications/fire-safety-open-sided-car-parks/real-fires-open-sided-car-park-fire-resistance-introduction-and-conclusion  

----
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.

Fire safety in Europe is shaped in a challenging ecosystem - each member country owns its fire safety rules, yet the construction market, standards, and technical language are increasingly shared. I’m joined by Francesca Sciarretta, Scientific Project Officer at the European Commission’s Joint Research Centre (JRC), to explain how the JRC supports EU decision-making with independent research and why that “science behind the policy” matters for every practicing fire safety engineer.

We unpack what the latest JRC work says about performance-based fire safety engineering in Europe and why prescriptive design still dominates. Francesca walks through how the same country can look “performance-based” to engineers but “not allowed” to regulators, depending on how approval pathways, deviation procedures, and legal wording work. We also talk about where performance-based methods show up most often, from smoke control and structural fire engineering to compartmentation, and why complex assets like high-rise buildings, airport terminals, and underground infrastructure frequently demand engineering judgment.

From there, we connect fire safety to the sustainable construction ecosystem: the Construction Products Regulation (CPR), the recast Energy Performance of Buildings Directive (EPBD), major renovations, and the reality that low-carbon innovation must not introduce hidden fire risk. The conversation then turns to the real engine of progress: education, training, qualification frameworks, and liability. If we expect engineers to define scenarios, design fires, safety criteria, and take responsibility, we need credible pathways to competence and continuous professional development across borders.

You can find the new JRC report here.

Information about the FIEP platform: https://efectis.com/en/fire-information-exchange-platform-fiep-2/

----
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.

You don’t always need a furnace to end up with a fire resistance rating, but you do need to understand what kind of “proof” you’re actually creating. I’m joined again by Dr. Piotr Turkowski from ITB to unpack calculation methods for fire resistance and the real-world chain from engineering assumptions to a Declaration of Performance. We talk about when standards and European Assessment Documents (EADs) explicitly allow Eurocode-based assessment, and how different methods will lead you to your resulting class in a different way.

We spend a lot of time on the practical heart of structural fire engineering: concrete and steel. For reinforced concrete (Eurocode 2, EN 1992-1-2), we compare tabulated data, simplified calculation approaches like the zone method, and advanced global modeling that starts to look more like performance-based fire safety engineering than classification. For steel (Eurocode 3, EN 1993-1-2), we break down critical temperature, utilization, section factor, and what you can realistically expect from unprotected members under the standard fire curve.

Then we get into the more challenging  part that tables or  simplified  methods can’t completely capture: fire protection materials. Sprayed mortars, boards, and intumescent coatings change properties with temperature, moisture, and expansion, and their performance can hinge on stickability, cracking, and detachment during large deflections. Finally, Piotr shares a strong caution on masonry, where tabulated data can be dangerously optimistic for some concrete hollow blocks, and we close with a look at what machine learning might someday add to fire resistance prediction.

Here is a link to the paper about Masonry: https://www.sciencedirect.com/science/article/abs/pii/S0379711226000512

ITB and Piotr have international courses on fire resistance and fire testing - keep an eye out on them!

----
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 fire fundamentals with the ITB fire resistance expert Piotr Turkowski we break down what a fire resistance rating criteria, and what the letters behind ratings like “REI 60” exactly stand for. We use lab experience to explain where the standards are clear, where they are oddly traditional, and where comparisons between products can mislead. 

• ISO definition of fire resistance as an ability over time 
• What R E I W and M mean in fire resistance classification 
• Load bearing capacity as deformation and collapse criteria 
• How test loads are applied and why load choice matters 
• Integrity E as flames and openings rather than smoke tightness 
• Cotton pad test and why it blurs integrity versus insulation 
• Insulation I temperature rise limits and prescribed thermocouple points 
• Radiation W as a heat flux limit and when it matters 
• Mechanical impact M and the wrecking ball style verification 
• Why fire resistance time does not add up across layers 
• Furnace minutes, strict thresholds, and unknown test uncertainty 

If you liked this podcast episode, you will definietely enjoy:

• https://www.firescienceshow.com/070-fire-resistance-is-whatever-you-want-it-to-be-with-piotr-turkowski/ our previous conversation with Piotr about general fire resistance paradigm
• https://www.firescienceshow.com/010-seeking-the-origins-of-standardized-fire-testing-and-ancient-fire-protection-materials-with-john-gales/ another take on the origins of fire resistance

----
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.

plume_rise_1.fds from the FDS Validation Guide (by NIST)

&HEAD CHID='plume_rise_1',  TITLE='Test plume rise height in stable atmosphere' /

&MESH IJK=50,52,50, XB=-50.,50.,-52.,52.,0.,100., MULT_ID='mesh1' /
&MULT ID='mesh1', DZ=100., K_UPPER=1 /
&MESH IJK=50,52,50, XB= 50.,250.,-104.,104.,0.,200., MULT_ID='mesh2' /
&MULT ID='mesh2', DZ=200., K_UPPER=1 /
&MESH IJK=50,50,50, XB=250.,650.,-200.,200.,0.,400., MULT_ID='mesh3' /
&MULT ID='mesh3', DX=400., DZ=400., I_UPPER=3, K_UPPER=1 /

&TIME T_END=900. /

&MISC TMPA=20.36 /

&WIND SPEED=5., LAPSE_RATE=-0.0048 /

&SPEC ID='SULFUR DIOXIDE' /

&VENT MB='XMIN', SURF_ID='OPEN' /
&VENT MB='XMAX', SURF_ID='OPEN' /
&VENT MB='YMIN', SURF_ID='OPEN' /
&VENT MB='YMAX', SURF_ID='OPEN' /
&VENT MB='ZMAX', SURF_ID='OPEN' /

&PART ID='TRACERS', MASSLESS=.TRUE., SAMPLING_FACTOR=1 /

&SURF ID='TOP', TMP_FRONT=200., MASS_FLUX(1)=0.01563, SPEC_ID(1)='SULFUR DIOXIDE', MASS_FLUX(2)=18.85, SPEC_ID(2)='AIR', COLOR='BLACK', PART_ID='TRACERS' /

&OBST XB=-2.0,2.0,-2.0,2.0, 0,75, SURF_IDS='TOP','INERT','INERT' /

&SLCF PBY=0, QUANTITY='VELOCITY', VECTOR=.TRUE. /
&SLCF PBY=0, QUANTITY='TEMPERATURE' /
&SLCF PBY=0, QUANTITY='DENSITY' /
&SLCF PBY=0, QUANTITY='MASS FRACTION', SPEC_ID='SULFUR DIOXIDE' /

&DEVC ID='z_CL', QUANTITY='MASS FRACTION', SPEC_ID='SULFUR DIOXIDE', XB=1800,1850,-200,200,0,800, SPATIAL_STATISTIC='MAXLOC Z' /

&TAIL /

Thank you NIST for providing an endless source of ASMR scripts on your github here: https://github.com/firemodels/fds/tree/master/Validation

I recommend everyone to go through this rich resource.

----
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 one takes a decision to evacuate and starts moving, this is not the end of their decision-making process. 

Which route to take? Who to contact? How to arrange a place of shelter? Where to go first? Have I forgotten anything? 

I previously discussed the decision-making with Erica Kuligowski from RMIT, and today we're meeting again to follow up on decision-making for large-scale evacuations. We focus on choices and uncertainties that make many of the evacuees take additional trips, and those trips become background traffic that interferes with your escape. In this episode, we dive deep into the decision making in this stage, the sources of data, and hypothesise how this knowledge could be used in practice.

And of course, Erica being one of the leaders of the Human Behaviour in Fire community gives us a high level overview how this part of science looks like, and what is currently being researched.

The HBiF conference we mentioned in the episode can be found here: https://humanbehaviourinfires.se/

----
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 fire in an informal settlement is not just another small building fire. It can be the first domino in a fast-moving neighborhood event, and the little details like the wall material, roof material, door location, even a light breeze, can decide what happens next. I’m joined by Dr. Sam Stevens from Kindling to unpack a massive FSRI funded experimental program carried out in South Africa that burned twenty different informal and humanitarian shelter types to measure real heat flux, flame extension, and fire spread potential. 

We start repeating the uncomfortable gap: humanitarian guidance often relies on rules of thumb like a universal separation distance and vague advice to “use fire-resistant materials,” with little experimental evidence behind it. Sam explains how Kindling built a global database of shelter designs and materials, then narrowed it down to common typologies spanning sheet metal, mud, timber, bamboo mats, split bamboo, thatch, and tarpaulin tents. We dig into the field-scale test setup, why wood cribs were chosen, and how external instrumentation like thin skin calorimeters helps quantify the heat transfer that drives structure-to-structure ignition. 

Then we get into what the burns actually show. Non-combustible shelters often behave like classic compartment fires where openings dominate, but even modest wind can push flames meters outward. Add combustible walls or roofs and the hazard shifts dramatically: some materials produce short, intense exposure windows while others sustain burning long enough to threaten neighbors at greater distances. The fully thatched shelter stands out for extreme radiant heat and duration, and our discussion on tarpaulin tents reveals why common fire test methods can produce reassuring ratings that still miss real-world behavior. 

If you care about informal settlement fire safety, humanitarian shelter design, fire engineering guidance, or modeling large outdoor fires in dense communities, this conversation gives you a data-driven foundation and a clear sense of what questions still need answering. 

Learn more about the project and watch their educational videos here: https://kindlingsafety.org/projects/large-scale-fire-experiments-for-humanitarian-shelters/

----
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.