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Fire Science Show
Fire Science Show
229 - Learning from 900 fires with Björn Maiworm
What can you learn after processing observations across 900 severe fires? A lot. Actually, I will send you to the paper straight away:
And now let's dissect this. We sit down with Björn Maiworm of the Munich Fire Department to unpack a decade of structured observations from more than 2,000 significant incidents (900 in the paper but the database already grew!) across Germany—and the results may challenge the assumptions of Fire Safety Engineers. Smoke spread shows up as way more common, despite that legislation should prevent it, and is often seen breaching beyond the apartment of origin when doors are left open, self-closers are defeated, or vertical shafts pull hot gases to the top floor. Meanwhile, true flame spread between units is relatively rare, suggesting that basic compartmentation and detailing are quiet success stories.
We also talk about people. Injuries appear in roughly a third of these consequential fires and fatalities in 6 to 7 percent, with risk concentrated in prisons, elder care, and dense low-income housing. Building age isn’t the driver; height and social factors are. Where self-closing doors are mandated and maintained, smoke infiltration to stairs drops—just not as far as theory predicts, thanks to behavior and upkeep realities. That gap between paper and practice is where small, targeted fixes make the biggest difference.
On emerging risks, the data draws sharp lines. Mass timber’s challenge isn’t fire resistance; it’s the speed and multi-floor spread when exposed surfaces meet window plumes. The result can outpace practical firefighting capacity. By contrast, shifting a typical household to an EV, PV, and home battery can reduce overall fire probability; the true hazards arise from poor products, DIY installs, and dense storage arrangements. The smart response is segmentation and simple physical breaks that buy time, not blanket bans or panic.
We close by reframing fire safety as a complex system problem. Instead of chasing perfect proofs, we can use continuous field feedback to find the leverage points: doors that stay shut, shafts treated as priority risks, vulnerable occupancies protected with tailored measures, and dispatch data that points crews to the right entrance first.
If this resonates, subscribe, share the episode with a colleague, and leave a review telling us which finding surprised you most. Your feedback helps more engineers, firefighters, and policymakers turn real-world lessons into safer buildings.
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Hello everybody, welcome to the Fire Science Show. If you want to do a good work, you have to do the work and then you have to figure it out if it works or not. That's how you find out the job has been done well. Now as a fire safety engineer, the second part finding out if stuff that we've done worked or has not worked is actually quite difficult and to some extent stressful. Because when stuff works we don't really know or we rarely find out, and when they don't work it's usually with a big media attention that we do not necessarily want. However, there are fires happening, hundreds of fires happening every day. And through those fires we could learn a lot about what was done in a building and did it work or not. The only issue is that someone would have to capture those statistics and process that data. And as you may figure out, this is exactly what we're talking about in this podcast episode. I have invited Björn Maiworm from the Munich Fabricate, who has run an exercise like this for years in Munich and other fire stations across Germany, and it actually still continues. And a year ago, Bjorn published a paper in fire technology where he summarized 900 potentially harming fires in Germany. Today he told me he has 2,000 in his database, and his database is something we will discuss in deep. How is he gathering the statistics from the fires? What is he looking for? And most important, what are the lessons from those those fires? We will talk about some general problems with uh gathering statistics. We'll we'll talk about collective experience on code writing and law and prescriptions. We'll discuss smoke spread, fire spread, and in the end of the podcast we actually this have a very interesting discussion about time to uh start uh firefighting in a building, which is a very, very interesting discussion. So I think it's a very nice one. I had the chance to record this live because Bjorn was visiting Warsaw for a risk conference that I have attended. So let's spin the intro and jump into the episode. Welcome to the Firescience Show. My name is Wojciech Wegrzynski, and I will be your host. The Firescience Show is into its third year of continued support from its sponsor OFR consultants, who are an independent multi-award-winning fire engineering consultancy with a reputation for delivering innovative safety-driven solutions. As the UK leading independent fire consultancy, OFR's globally established team have developed a reputation for preeminent fire engineering expertise with colleagues working across the world to help protect people, property, and the planet. Established in the UK in 2016 as a startup business by two highly experienced fire engineering consultants, the business continues to grow at a phenomenal rate with offices across the country in eight locations, from Edinburgh to Bath, and plans for future expansions. If you're keen to find out more or join OFR consultants during this exciting period of growth, visit their website at OFRConsultants.com. And now back to the episode. Hello everybody. I am joined today by Björn Maiworm from Munich Phi Department. High level officer. Hey Bjorn, uh good to good to have you in Warsaw. Welcome. Yeah, thank you very much for having me. It's uh it's been a long time. I've seen your talk, I think it was at SFP Copenhagen, I think. In Copenhagen, yes, yeah. That's when we agreed to do an interview. We're a few SFP events later, but I'm glad you found your way to Warsaw. It's not the greatest weather, so we can at least do a podcast episode. So I remember back then you've shown a very impressive study studying the statistics of fires from the perspective of firefighters and trying to make sense out of it of how the measures are effective. Do I remember correctly?
Björn Maiworm:In the end, the idea is well, if you draw a fire safety design of a building, it's a theoretical idea, it's a planning idea, but we don't have any data about the outcome. We don't know that what you designed actually worked out. So the core question is not how did the firewall fighters work, how was the planning or design, something like that, but did the building and its design work out in real life? It's like buying a car, and some fancy engineer told you it's a very safe car. We put this and that in. We said, Well, how was a crash test? We didn't do any crash test. So this is actually the summary of many crash tests where the people were to introduce a fire test.
Wojciech Wegrzynski:I mean, it's a very rare perspective when I talk with uh firefighter colleagues. It's a common thing, actually, the the issue with data. I I had uh Eurostat project people in the podcast. Uh I'm due to do one with uh FSRI where they revamped the statistics in North America. But it's quite challenging to get meaningful engineering related data out of uh fire statistics. What was it the trouble for you before?
Björn Maiworm:The system the statistics we have from the fire department's perspective is how many fire alarms were there, how many false alarms, how long did it take to go there, maybe if they collected that data, how many hoses did we use, how many engines and trucks? How many little little stuff? How many so what i if if they even guessed it somehow, but usually they don't have any accurate data. But in the end, with that data, you can't do anything concerning building safety and building design. So we you must connect the systems because from our point of view, as German fire departments, the building regulations and the building design resembles the ability of the fire department's work. So they're interconnected. If you don't have a fire department, having a system with, for example, a second escape route wire ladder is helpless. You can see that, for example, I was in New Zealand, every smaller hotel has an escape ladder on the outside. On the outside. In Germany, it's standardized to have a second escape route via the ladders we bring as fire departments. But that means you need to have a very powerful fire department everywhere. Okay, so this resembles in all the metrics we have in our German building law, resemble the abilities of the fire department.
Wojciech Wegrzynski:I wonder to what extent the technical regulations in Germany were driven by the capabilities of our brigade. I I think all safety regulations are written by blood.
Björn Maiworm:Yes.
Wojciech Wegrzynski:And with blood.
Björn Maiworm:Due to the experience of loss. Middle ages fire, huge city fires, we invented firewalls, non-flammable materials, and all this stuff that's taken for granted now. In the time when fire departments developed, like in the late 1890s, 1900s, something, where was the time when the building code was developed. So these two systems interacted, and of course, fire safety or fire offices, high-level offices were part of the regulations group.
Wojciech Wegrzynski:In Poland, it's kind of like as you say, it it had to be there had to be a tragic event or something that uh issued a big revamp in the system, and basically the system would adjust itself to respond to whatever happened, or perhaps there was a broad big event that happened and we just imported some knowledge, that's arguably the better way. But um, I'm not sure to what extent they reflect the capability of the fire brigade, you know. If we had an event where we had a big uh spillover of an oil tank in a refinery, Czechovice Jijitse fire, they've implemented a special uh you know industrial fire protection around tanks, etc. It had a lot involved. I you you told me the story of a firehouse. Maybe it's worth it to uh repeat it, how firefighters implement influenced the regulations themselves.
Björn Maiworm:First, let me call it on your tank fire. Yeah, this is a very unique thing from a societal point of view. Yes. So, first of all, in a building regulation, you want to regulate a standard building. What is a standard building? It's an apartment, it's an apartment building. It's where people live. This is the majority of buildings we need. Then you maybe need an assembly hall, you need a hotel, you need a shopping center. And this is how the regulations are focused on. And in in the end, as we we talked about before, let's talk about the escape route length. You can do some fancy calculations. What's the visibility and the FED model something we heard on the uh conference today, and and and all these aspects. But in the end, from our point of view, in as far as what I could find in any historical document, the 35 meters distance between the very end of an apartment towards the door to the stairwell, and doesn't necessarily have to be the door of the apartment, the maximum travel distance is 35 meters. Okay. Because in the stairwell you can retreat to the next floor below if there's a huge fire as a firefighter. So you need to enter. And every firefighter, Second World War Time and after and up to today, the length is 15 meters for one hose. So there are two guys going up there, every one of them has a hose, and you connect your hose there from this door, and then you enter, crawling under the fire, plus a five-meter distance of spraying the water. So the 35 meters in the end resemble the depth of attacking the fire. And if you did you ever extinguish a fire, or did you do the training? Okay, you did. So you know that a hose is quite heavy to pull. And if you connect them endlessly, it won't be possible to move. So from a practical point of view, craftsmanship, it makes sense. And then if you have some guy calculating that you can install an early smoke alarm detection system and everyone runs. It takes you 27 seconds to move 35 meters. Something like that, so we can extend the length towards to 100 meters. No one would ever expect a firefighter to enter a room 100 meters with a house without the possibility of retreat. It's far too dangerous. And this is what the safety or rescue teams must be taken into consideration.
Wojciech Wegrzynski:Don't quote me on this, dear listeners, but uh I I once was very um intrigued by the concept. I'm not sure if you have it in Germany, but if you have a wall that separates rooms in an office building in Poland, let's say you would have an one-hour rated wall, the doors would be 30 minutes, like half the fire resistance of the wall. And it was quite funny in Poland because people started installing sliding walls and they were basically just giant doors without any wall component, and suddenly they were like 30 minutes all of them, you know. That has obvious business implications, right? And I was I was desperate to find where the hell did it come that we do half of fire resistance of the door versus the wall. And I found one thing from the 70s, I believe that was in Sweden. Like I cannot recall the name or any details, but it basically said that on a door opening, it's so much easier to stop the fire than on a firewall. That if you have just half the fire resistance of the wall, you'll be good because a firefighter uh standing like a few meters away from the door with a spray hose and a spray pattern can hold the fire on there. And I was like, oh my god, this is like not how we use it today.
Björn Maiworm:This may be one aspect. In the end, you could have a practical explanation, like on top of the room it's hotter, and then why don't you impact that long and all this stuff? But in the end, the cop compartmentation of a system, of a unit, and introducing a door allows us to defend as a tactical term, to defend the neighboring rooms and to defend it from spreading. And it's ensures our safety. Because if you can retreat behind a wall, you can attack out of coverage, out of colour. And then we have the same discussion with large office buildings in Germany. Well, you need 30 minutes of fire resistance and all this stuff. Yeah, we do know that it can burn through, but we can defend it. And in the timeline where we actually can do work, it works out. It makes sense. Of course, from an engineering or scientific point of view, we don't have any proof. It's just a very good gut feeling, a very good engineering judgment, how we call it. But in the end, we must trust that.
Wojciech Wegrzynski:Now that that brought us, that segued us beautifully to the subject of this interview because it's about replacing gut gut feeling with data. And while a fire engineer, you can spend all the time doing your CFD analysis, doing your finite element model analysis of a wall, how well it will behave in a fire, in what kind of fire, in what circumstances. In the end, life kind of verifies this by a real-world fire experiment. If a fire happens in that place, and this is an opportunity to figure out how it actually worked.
Björn Maiworm:Yeah, actually, it just started that for decades. It was totally accepted when the fire department's representative said, well, this works and this won't.
Wojciech Wegrzynski:Just by the power of authority?
Björn Maiworm:No, no, by the power of summarized experience. Okay. And by trusting in the expert you have there. Not just by his own experience, but by the summarized experience of the organization. It's not just me. I'm representing German fire departments in a lot of committees. It's not me talking there, it's a summarized experience and now based on data. And then in the last like 10 to 15 years, more 15 years, we had scientists that said, Well, you don't have any scientific proof for that, so we don't need that requirement. And this is when my boss and I we said, Well, we we need to collect data, we need to collect the knowledge. How do we do that? So we developed a questionnaire for the fire departments, and after a fire, with the allowance of the landlords and with the allowance of the police, we go there and we collect the data. What kind of building is it? Is this a special construction, like a hospital or things like that? And then we go through the safety objectives by law, like people's safety, um firefighter safety, and all these aspects.
Wojciech Wegrzynski:By design objectives, you mean you go through what was designed in the building? How was it built?
Björn Maiworm:No, what is the general requirement by law? By building it construction products regulation, heritage protection, environmental protection, which are the objectives we have as a fire department by law. Our job is to rescue you, get you out, survive the attack and not lose any firefighters there, minimize the damage, take care of the environment and cultural heritage. That's in the end.
Wojciech Wegrzynski:I I I like a lot of places do save statistics, but it's it would be very rare to like have a detailed description of what was the building status, like what technical systems did it had, what were they in operation?
Björn Maiworm:We don't look at the fire def design or the the the building permit. It's what's really interesting in this research program, it's non-scientific. There are not any scientists going on scene. Asking you what was the heat release rate and how do you define what is a significant fire, something like that? Because we use the German phrase for significant fire. It's a fire that is at least so developed that it can ask the question toward the objectives. So a small bin fire is too small to ask a firewall, are you strong enough? Or a fire door, 30 minutes resistance. So it needs to be at least bigger than a small burned food kitchen fire, which is done a thing at noon you go there. And then we spread the news 10 years ago, it's now our anniversary. 10 years, thank you. It's a long, long last long journey. Yeah, long, long journey. And now we cover with the participating fire departments more than a third of the population in Germany. Wow. So with the area where they are responsible, of course, their data set grew in the last four years, five years enormously. Because it's about trust too. Because the fire departments need to trust us as the association of the fire departments, that we don't have a look at the fire department's work. Yeah. That we only focus on the building. So when my colleagues go on a scene, for example, in Munich, where the majority of the data set is coming from, like 30 something percent, I always tell them never ever, never say anything about the fire department's work. Don't. That's not the point. It's not the point. Focus on the building. And it even led to a situation where the police officers ask us, what happened here? And then we explained to him, well, the building's design was poor. The landlord's efforts to keep it going were very poor. So, from our point of view, the three people died because of the landlord's failure. And in the end, he was convicted. So this is another focus that can be an outcome. But now we have more than 2,000 data sets. Okay, that's a lot. That's that really a lot. He can do a lot of things with it.
Wojciech Wegrzynski:By data sets, you mean you're like real-world fire accidents from which you have the questionnaire filled out by the fire becomes fully full.
Björn Maiworm:Uh I just drew a missingness map. So where's data missing? Something that it's really cool. It's more than 97% of all the questionnaire parts for the listeners.
Wojciech Wegrzynski:The earlier version of the database, which I'm looking at it right now, it had 900 uh data sets, uh, was published in fire technology. So I assume it's it's an ongoing, we'll probably discuss about if this evolves and and how. So, can you give me like an example? Like people going into let's say warehouse fire. What kind of data are they supposed to leave you? What are you looking into? Like maybe you can maybe have some examples of how a questionnaire looks like a model one.
Björn Maiworm:A model one would be an apartment, a fully developed apartment file in a residential building. Okay. In an urban area. Okay. It's a very urban data set because the smaller rural departments are not that big represented. But I will come to that later. But you have this apartment fire and then it's um did you see any or did we have any injured fatalities? Um what were the means of rescue? So did they escape on their own? Were they rescued by the fire department? Did we see any smoke spreading? Because by law it must be pre prevented that smoke spreads. Did we see fire spreading? Did we see fire spreading towards the neighboring building? Firewall? Middle-aged knowledge? Uh yes, don't laugh, that's it. Did we have any injured firefighters? Were there was there a smoke alarm installed? Were then automatic fire some sprinter system all? But it's not in an apartment building, you don't have any sprinter systems in Germany. So this is more in the special construction branch. But you still save the data. We saved the data. And did you did we have any environmental impact and all this stuff? And from the very beginning, like we had 150 to 200 data sets. The numbers kept being the same. And I was very surprised that they didn't change anymore. And even if I have a look at sub-datasets from other states in Germany, maybe from Bavaria, from Northern Westphalia, and everywhere. I see the same numbers. I see the same numbers and the same percentages if the data is coming from Berlin or from a small rural fire department who sent me like 10 questionnaires. That's really an interesting aspect. How stable the data set is.
Wojciech Wegrzynski:By stable you mean in terms of uh the likelihood of the fires, like how many times they happened in different times, or no, no, I don't have a look at the likelihood.
Björn Maiworm:Okay. Because the questionnaire focus if there is a fire, what happened? And it's kind of biased because I don't look at the small fires. So the likeliness, I don't I don't care for the probability about the probability because from a fire department's point of view, I only come to your home, to your apartment, if this probability is summarized in a fire.
Wojciech Wegrzynski:So then you but by similarities you mean the outcomes, the numbers of injured per residential would it's always the same pattern.
Björn Maiworm:So the the likelihood that we see a spreading of smoke is always the same. Okay. About 60% of the cases, two-thirds. I see a smoke. Well, so we we can see a smoke spreading that violates the objective by building law.
Wojciech Wegrzynski:Are you capable of distinguishing this by the age of the building or oh yes, we did that.
Björn Maiworm:Very interesting. This was one of the few results where we were surprised. So you usually you have a very good gut feeling. Well, let's have a look at the numbers, for example, for injured people of fatalities. Injured people, if there is really a developed fire and you regularly see smoke spreading, as we learned, you will see injured people. And injured means coughing. You inhale smoke, and they were injured, they were transported to the hospital. It's not a very sophisticated ICD 10 something medical evaluation, but they were injured. 30% in the cases. If there is a fire, the number of fatalities is from my experience comparatively high at approximately six to seven percent. I think six or seven percent of events. If there are 100 fires with six or seven fires, you will see a fatality. Okay. That's very high compared to the low fatality numbers we have. Because we have a lot of small fires that will never ever be big enough to ask the question toward the building. So they are not in our data set. Yeah, you're guys, yeah, of course. So and we see a lot of rescue efforts by the fire departments.
Wojciech Wegrzynski:As in the fire department has to rescue people.
Björn Maiworm:We have to rescue they are in the apartment, maybe standing at the windows, and then they can't escape on their own. So in 40% of the cases. That's quite high. And then we did just the last master thesis. We work closely together with the Technical University of Munich, and we now have 30 thesis, 13 evaluating the data set. And that that's it. And then, of course, what we always see is smoke spreading, rarely fire spreading towards another unit.
Wojciech Wegrzynski:Okay, but the the the statistics you said, like six percent fatalities, 30% injured. This is for the entire dataset. How about when you look by occupation? It's all residential.
Björn Maiworm:What's really interesting is that we only see three types of buildings where where we have an elevated level of injured and fatalities. And by gut feeling we knew that, but we couldn't prove it. Okay. It's jail. Okay. Of course, they have that's a challenging evacuation system. Yeah, they don't have an escape plan, actually. Some of them have, but obviously, yeah, some of them have, but not in that case. So jail has higher values, not a hospital, what you would expect. I would expect retirement house. It is. Yeah, it exactly is. And what we see in the data, and we try to prove that with the next thesis, it's a social aspect. Okay. Because if you put a lot of people, poor people, regularly, call the poorer, in. And what we can see in the data set with another PhD thesis, if you are married, the likeness that you die from a fire is half even less likely than if you're a widow. So widows rise. Okay. And that's very interesting because it gives us a perspective of a social aspect and a residential building like student apartments and all this where a lot of people pull people up put together. We see more likeness of being injured or four fatalities.
Wojciech Wegrzynski:Well, this is well, this is challenging that I I keeps popping out, and by common sense, I think it's it's reasonable that you're most likely to be injured in a fire in your own house or or in general in a residential building.
Björn Maiworm:But on a scale where you see that many fires, yeah. What I think it's what is really reasonable as a system of explanation is that if you don't pay that much rent, your landlord can't put that much money in the building. And if you're rich, you have a very thick door towards the stable, for example, because you don't want the noise from the neighbor, don't you? Yeah, yeah. You have modern windows. Okay, so our So in an old building you have the thin doors and the thin windows.
Wojciech Wegrzynski:Okay, so you want to say that within the residential subset, you have also full subsets that are socially linked.
Björn Maiworm:Okay. Okay, to the risk. So this is one one of the explanations. And what was really interesting, now I'm coming back to the surprise. We thought the older the building, the more likely it will be that you see smoke spreading. That's what I would say as well. None really, absolutely no correlation. Lock it, regression. So we really did some math on it, some statistical doings, and in the end, we saw it connect with the how many floors are there. Okay. And the bigger buildings in urban areas. Usually poorer people live there. Okay. And what we saw is in in in the last thesis, if there's a fire in your kitchen or your uh bedroom and all this, 40 to 50 percent likeliness that we see smoke in the stairwell. If there is a fire in the cellar, more than 80%. But guess what? By German building law, you need a self-closing 30 minutes fire resistor towards the cellar. But usually, what is it? Kept open because it's annoying. Yes, yes. If you go down the center. Mine is all also open. And we see that in the data. Uh we see this common sense.
Wojciech Wegrzynski:We're moving to smoke spreading. Uh, could you define what does the firefighter who's doing your inquiry, your your uh questionnaire, when do they say it's the smoke is any proof of smoke outside of the compartment of origin is it's very obvious.
Björn Maiworm:Yeah, it's very it's not about some well now it smells in the neighboring unit. Usually if we say it's smoke spreading, it's dark. Okay, so you can see it. So this is one of the things when I say it's not very scientific, and we're doing science with it.
Wojciech Wegrzynski:Yeah.
Björn Maiworm:Because it just what is obvious.
Wojciech Wegrzynski:So you found smoke spread in um more than half of all your cases. You said you're it's it's a contradiction of the German code which explicitly gives you measure to prevent. Do you know what failed? Like was it mostly the doors kept open manually?
Björn Maiworm:No, it's not keeping the doors open. It's it's generally the apartment door. If you don't have a self, if you don't have a self-closing mechanism applied to your door, and you try to get out, you leave the door. What we regularly see is if someone's trying to flee and and and he comes to the border between hot and cold, his system, his body collapses and he's lying right in the door, even though it's, for example, self-clothing. And what we saw in a subset very new data is like almost 20 years ago, they introduced self-closing doors. No, 30 years ago in Bavaria. And what we now see to compare to the state that don't have that, that the preding likeness reduced to the stairwell, but not down to the level what would be expected from a technical point of view. Like a self-closing mechanism fails in 1% of the case, something like that. Why is that? Multitude of explanations. But one could be they disengage the self-closing mechanism because it's annoying. Yeah. You have your baby on your arm, you shoot in your in the back, and you try to get in, and the door is self-closing, all this crap. So it doesn't work. And it needs maintenance, of course. And it's not checked like any other fire-resistant door at another place in the building.
Wojciech Wegrzynski:What about the pathways like the building ventilation system? Like I'm a smoke control engineer. A lot of my work is towards smoke control, which is obviously a ventilation system. But the the first step of successful smoke control is to shut down the HVC in the building, which means I have to turn everything off and close in the big building a thousand fire dampers. Have you seen any uh signs of that system?
Björn Maiworm:Yeah, what we see is apartment door, most likely, then the window, obviously. You mean true exterior, so the smoke exits and enters towards another unit. Okay. So if I talk about smoke spreading, I mean violating the border of the very apartment or the so-called unit. So you're fine with the fire being in one unit and if it goes to another unit. If you have a fire in your kitchen, we expect there to be smoke in your bedroom. Yeah. I don't care. Questionnaire we say smoke spreading, no. But if your neighbor so building law is mainly protecting you from your neighbor. So there we see the window, and what we see are shafts inside the apartment building. And what we see is the very experience we have. For example, you have a fire on the first floor, and then at the top floor, you regularly see smoke spreading by the shaft. This is very common sense. You have a kitchen shaft, for example, or from the bathroom, and then it tries to leave the building. It draws back. So it's double. The likeliness for the top floor. So, from a firefighting perspective, that's interesting too. Because usually you would check the next floor. And I myself, knowing the data, I regularly send someone to look at the top floor in the bathroom, in the kitchen, if there's smoke. And I even have a fatality once. An ordinary kitchen fire on the first floor led to a fatality in the top floor.
Wojciech Wegrzynski:It was not me, but my colleague from office, Jagosh. Uh, he was once investigating a case where there was a fatality in a building, and allegedly the wind conditions in that day were so that CO produced by someone else's heater was released through the chimney, and the wind pushed that CO into the chimney.
Björn Maiworm:Yeah, CO is bad.
Wojciech Wegrzynski:Yeah, we and we we have investigated this case uh through wind engineering for that particular day building to judge if it was scientifically possible or not. It was possible. It was very likely actually. So we were just discussing about the smoke spread, the doors, the shafts, the windows. And what about the ways of fire spread? What have you seen?
Björn Maiworm:Well, as as I said, fire spread doesn't occur that often. 15%. Yeah. And then I thought, well, maybe we can see a focus as we saw with the smoke spreading. We don't see any focus. It's like common sense, flat distribution of the categorized ways of fire spreading. That, from my point of view, leads to the assumption that all the civil engineers do a good job connecting walls and floors and ceilings. That's mainly it. And designing fire resistance in any capacity. So no task to talk about. It's kind of boring.
Wojciech Wegrzynski:So you just got you just have the statistics, but it's well, still I I find quite a large number, 177.
Björn Maiworm:Was the it was is it again a majority in the residential buildings or I have a majority of data sets from the residential buildings. And I don't see, and I have looked in the sub data sets, I don't see any focus. I see nothing concerning anything where we'd say, well, oh, there we have something that could be better.
Wojciech Wegrzynski:Well, just stop it. I I mean if if there's a statistic that's boring, that's good. Yeah, if there's a fire statistic.
Björn Maiworm:It just shows that we know what we are doing. But we didn't talk about the elephant in the room. Do we need to get better? Yeah? Do we need to change anything? And from our point of view, with the lowest numbers in fraternities in Germany ever. No. So as a society, if one person dies in a very unlikely event of a fire, lying in his bed, maybe an elderly person and couldn't escape. That's very dramatic for the person, a tragedy, isn't it? But for us as a society, it's just a small news in the newspaper. If we have a multitude of fatalities, like ten people dying in an elderly home fire, as we had in the last years in Germany regularly, then it makes nationwide news. And if you have a catastrophic fire like Düsseldorf Fairport or uh Grenfell Tower, it makes worldwide news and has an impact. If we go down to the number of like 100 fatalities in the magnitude of that, this is where we have look at so we don't need any better fire propagation measures, down to 15%, that's nothing. And smoke, we just observe. But our conclusion is maybe we need don't just need a regulation for hospitals, maybe we could, it would be respectful toward the elderly to introduce a building regulation for the home for the elderly. But from a cost perspective, they decided no, we won't do that.
Wojciech Wegrzynski:Well, technically you see that. I find it interesting in this data set that you can see, like for the Bavarian case and the fire doors, there is a measurable improvement in those statistics at this number of Was there anything else like that so obvious in the statistics that made a big difference?
Björn Maiworm:Were you able to track any other cases of uh modifications in the No We didn't have a look at the modifications yet because the last modifications in the building code were introduced by us?
Wojciech Wegrzynski:Okay.
Björn Maiworm:So with the RD, and you need at least two decades to see that in the data set.
Wojciech Wegrzynski:But okay, but you must have a differences between lands, like different approaches to do, for example, an assembly hall. Or it's not unified in general Germany, right, as far as I know.
Björn Maiworm:Because we do have these model building regulations, and I'm part of several of these groups that write these um regulations. The deviation between the model and the actual one in the very of the 16 states, it's just a very small deviation. They are mainly the same. And we don't see fatalities in assembly halls and all this. And why is that? Because in assembly halls, for example, in a football stadium, 60,000 fans yelling in a circus stadium. If there anything fails, it fails bad. So this is why we don't see anything there. And it's like you you could say we have the fewest car crash fatalities ever in Germany. Well, we don't need a seatbelt anymore. No one would say that. Yes, yes, yes. But this is a problem in from my point of view in the building regulations, because you have a social technical system, and any change needs a long time to really show what will happen in the system. It takes decades. This is from my point of view very difficult to decide. Well, let's get off rid, for example, of stairwell surfaces must be non-flammable. For every engineer, it was absolutely clear if they have a wooden stairwell, it's like a chimney. A wooden chimney. So a very rapid fire spread. But I've seen proof engineers stating, well, we install a fire alarm, a smoke alarm, and alarm the fire department early, they will cover that problem. And what we've seen now with wooden constructions, another paper, is that that doesn't work. The fire is that fast that even if you alarm the fire department earlier with a very rapid fire growth, that's great. We you have no chance.
Wojciech Wegrzynski:You have kind of led me to another question I wanted to ask because the world is changing so fast. I see three technologies right now that could tremendously change all of this. One is the timber, the return of timber to construction. You must see this in statistics. I I I would assume you would see. Well, we did, we published a paper on that too. In a second, we'll we'll talk about that. The second would be the energy storage in your buildings. In in terms of power, maybe we don't have power walls uh large enough. And and three would be immobility, something that FSRI shows. No, you haven't seen that in your statistics. Yeah, we did. You did.
Björn Maiworm:We did a lot of research on that. Yeah, we had the largest fire test worldwide concerning Lypium iron batteries. Okay. Together with the Technical University of Porschweig, Professor Tsifus. We had eighty tons of batteries. Eighty tons. 80 tons.
Wojciech Wegrzynski:That's a little bit about it.
Björn Maiworm:So just to go through all your three aspects. Yeah. First of all, wooden constructions. It's not about the fire resistance. If you have a large thank you for saying that. I'm uh looking for that. Large piece of timber you can calculate by Euro code five the fire resistance. So it can be endlessly from that point of view.
Wojciech Wegrzynski:It's just a number.
Björn Maiworm:It's just a number. But I don't care. I care from a topological point of view, from a system point of view, how often do we see a full loss of a building? So once a year in Germany, no one cares. But if there's a small fire in an apartment, a kitchen fire, yeah, and you regularly lose the whole building with a lot of fatalities because of the enormous speed, because you don't put plaster on the wall, the visibility of surfaces, wooden surfaces changes the game totally. And I don't know any fire department in the world that could cope with a fire on three floors at the same time. Because you have that many flammable fumes on the outside of a window. We don't see a fire spread just into the next floor through a window. But the heat is so it goes to the third, second or third floor above. And I don't know any firewind that could cope with that. So it's more about speed and less about fire resistance, it's more about flammability than the problem if a wall burns to okay, Mr. Firefighter. But do you have a proof for that? I have. In the paper we just published in German in Bautechnik, regularly we see uh fire spread in approximately 15%, mainly through a window. Uh in wooden construction, it's a very small data set, of course, because we don't have that many buildings yet. More than 50%. And firewalls, for example, are really good middle-aged knowledge. We usually see like 2% of the cases, and regularly only in row in terraced houses. So the small ones. In the bigger buildings, we don't see any fire spread crossing a firewall between buildings. But with timber construction regularly, like going up to 15%, 20%. We we don't know that. Yeah. If there's a firewall, you can rely on it as from a tactical point of view. But now we have proof. It's a small data set, but we have the first not proof, but maybe indicators proving our gut feeling.
Wojciech Wegrzynski:It's a a small data set, but uh unfortunately growing. Uh so uh fast. Just got some pictures yesterday from a colleague of mine. How about uh the batteries and uh how about okay about batteries?
Björn Maiworm:Um tell you you have a canister of fuel at home. You would sell okay, this is flammable and no problem at all. You have a car, ordinary car with fuel in your garage that could be on fire, couldn't it be? But we learned as a society that's so unlikely with the ordinary garage, this works out. Now coming to data. Let's do a mind trick. Yeah, you sell your fueled car, you buy an electrical car, you buy a home storage battery system in your cellar, and a PV system, a photovoltaic system. And I asked the question towards the underwriters of all German insurance companies. They had an a meeting. Said, what do you think will happen with the likeliness, the probability of a fire? And they all wrote their hands, but plus 50%, plus 200%. Um, there was a paper from the uh University of Aachen. The actual data, a huge data set, shows minus minus 17%. Minus. Minus. So if you sell your car in your single family home and buy an e-cor, a battery, and a PV system, you lower your risk. The probability for a fire of the PV system or your battery storing the PV energy is as low as your tumble dryer or your washing machine. Only the fridge is safer. Which allegedly was the case of Grandfall, by the way. Yeah, yeah, I know, I know. But in in the end, as a society, it's okay. And what we see in Germany, if there's a fire, a house fire, it's not a technological problem, it's a product problem. Yeah, too many factor manufacturers had problems with their batteries, they had a huge recall. And what we see a lot are some guys that believe they could put their batteries themselves together by some fancy YouTube video. And if I would tell you, well, I engineered at home my own gas heating. Yeah, and gas is so dangerous, now my house exploded. You would never say, Oh, gas is uh the issue, the problem isn't the problem. You're an idiot.
Wojciech Wegrzynski:Yes.
Björn Maiworm:Buy a heater from a company and it won't be a problem. But okay, but but coming to other aspects, what we see in the data, and we changed our model building code towards uh steel garages, is that the fires are more intense, but not due to batteries. What we see is the cars got bigger, yeah SUVs and all that. A lot of papers going in the community around, it's about if we keep the parking spaces with the same size, so the cars are closer together, it takes not 50 minutes but seven minutes for fire spreading toward the next car, and we see these huge fires. And the only thing we need to learn as a fire department is how to cope with the venting causes. If there's a problem with the venting and the batteries because of the thermal cause.
Wojciech Wegrzynski:But didn't don't you see in statistics the okay, we'll we just uh briefly touch the electric vehicles in terms of of scooters, etc. Don't you scooters is another story. Yeah, but but don't you see those uh batteries be participants, not necessarily sources of the fire and making the outcomes measurably worse?
Björn Maiworm:Like all we know is, and we did I do a lot of research with batteries, and we got a lot of uh fire tests going on with about storing, and we will just publish next week a recommendation for storing batteries and production facilities. And this is like comparing it again to fuel if you have a huge tank of gasoline stored. Everyone will say, Well, there we need special regulations for storing this huge amount of fuel. And this is the same with batteries. So we will introduce a recommendation that states if you're above the level of five tons, was this a suggestion just to start somewhere, separate these areas approximately 150 square meters, but not separating with firewalls or resistance, but even stacked uh concrete stones, like playing that I don't know, I don't I'm not in the blocks, not let don't let's use the product name, these blocks. Like, and then you don't prevent the fire from spreading totally, but you give the fire department time to attack at a point at which they can well they still can act because if you have the model building regulation for industrial buildings in Germany, you would be allowed to put a storage facility 1200 square meters, a distance of three meters, another one thousand two hundred square meters. That would be too big. Okay, Bjorn, and and the scooters? Well, I think we need more common sense. Are you well but oh well let's put it another way. If I told you I put my old cheap moped with fuel in the stairwell, now it's on fire, everyone was injured. Or I put it in my apartment. You're an idiot. You're an idiot. And what are we doing is we're putting these materials in our apartment, and usually a car battery doesn't fall down. It's one of the mechanisms to start a fire in a battery, in a failure in a fire. And then we have these batteries, we let them fall down, it gets knocked down, we don't handle it carefully, and then we are surprised. Well, oh, the bad battery night in my apartment. Yes, why did it do so? Because if you buy the cheap product and you don't take care of it, don't be surprised if it's on fire. Of course, we see that in the data that there are more fires of this kind. But we as a society learned don't take your fueled car, bike, motorbike in your apartment. And they take their fuel, their battery, back in the apartment. And this is what we will learn. By blood.
Wojciech Wegrzynski:I mean, it's a challenging topic because I I also as you said a lot of that is connected to social status. And if you are rich enough to have a separate space to keep your mouth somewhere, it's safer. But if you're just renting one bedroom for half of your wage and you have to keep it somewhere, it's not that you have much choice. It's very challenging. So but it's interesting that you can see things like that in statistics later.
Björn Maiworm:We can see it, and what I think what is important to note is that from a regulator's point of view, from the elected representative's point of view, when will the problem be big enough that we need to introduce a regulation? Yeah, and yeah, very interesting. From not from the point of view how to make it better, safer. I I don't like these phrases. I I mean, is it really necessary to change anything? Or is it just common sense in the society developing? And we are really fast in getting better concerning this technology. For example, the Chinese market will introduce a regulation in I think two years that the propagation in the battery is prohibited. Is prohibited. So I've seen the engineering in Germany, and you know I'm from Munich, and we have some smaller companies there. Some companies. And they showed me how they engineered a solution. I was really impressed.
Wojciech Wegrzynski:I was just on a conference on batteries in China, and you know, seeing hundreds and hundreds of researchers and each group working on some sort of a solution at the battery level, at the cell level. I mean, I'm not saying that I've seen the final greatest solution already there, but I just seen you, you know, those hundreds and hundreds of people working towards one and their accumulated effort will yield a good solution.
Björn Maiworm:And we are that fast, almost in less than a decade, we find solutions. Because if you compare to the ordinary car, when I became a voluntary firefighter in 1999, a few years ago, the elder, so the old firefighters told me, Well, if there's a car crash, you need to be prepared for a car on fire. I've never seen that. Because in the 1990s, we've seen an improvement in the technology itself. Airbags were invented, all the passive systems, the active systems. So the car knew, oh well, there's an impact. Now I need to stop the pump from pumping fuel. Yeah. And we don't see any coal fires.
Wojciech Wegrzynski:Just putting the the the fuel tank underneath the vehicle has seemed a Yes.
Björn Maiworm:So and this took like 30, 40, 50 years. Now we see it in just one decade. So please do stop arguing about we need to make it safer. I mean, yeah, you didn't from a building regulations perspective.
Wojciech Wegrzynski:Well, uh you have to appreciate it's also politics, you know, and and of course. And and if it's a political decision, but if in here in this podcast we talk science and engineering, we don't do politics. Uh, but I appreciate the fact that politics exists.
Björn Maiworm:But the ALAP principle is the common sense too.
Wojciech Wegrzynski:Yeah.
Björn Maiworm:Is it safe enough from that point of view? Where do we start? What and our idea is to put the finger in the wound where it is necessary, and to even introduce a deregulation where possible. For example, what was really interesting, the German regulations about fire extinguishers at work. The necessity. Well, they designed the amount of fire extinguishers by the fire load that is there. I don't know if you've seen the video from the climate where they not very successful. Didn't use these very what we see in the data is if they use multiple fire extinguishers at one time, the likeliness, or what we assert, that someone will be injured doubles from 30 to 60 percent. And 23 years ago, my former boss, and he was also the chairman of this expert group for fire prevention of the fire departments, we published a recommendation stating put there one standardized fire extinguisher every half escape route length, so approximately 17 to 18 meters. And if this one fire extinguisher's extinguisher is empty, run, leave the building. Do you know why that was never introduced in our regulations? Because we are not part of that group, because the manufacturers for fire extinguishers argued the fire departments don't know how to work and to fight a fire with a fire extinguisher. So we as the experts, as the producers, we want, of course, more fire extinguishers. So by getting rid of fire extinguishers, we would enhance fire safety. Because you don't give a this promise of safety. Yeah, never ever put three or four fire extinguishers side by side at one place, because in the event of a fire, it will lead people to stay too long.
Wojciech Wegrzynski:That's a very intriguing uh finding. Well, it reminds me of a YouTube video where someone guy was talking about like he was an expert in industrial electrical uh power plants, and he was responding to a comment like, What uh steps would you take when there's a fire in a power plant? And he said those would be quite big ones and very fast ones. That's the types of steps I would be taking. Very good. Um Bjorn, we're we're moving towards the end. Uh, there's one more interest because it's it's like we we sidestepped into very interesting philosophical discussion, which I think was very, very needed. One last final item for engineers because you also shown the time of intervention from your statistics. I find this very, very interesting because it's a usable data point that fire engineers can actually argue with in their fire strategies. Oh, like when people discuss the safety of timber buildings, I have another colleague in the office who is an advocate for timber buildings. I'm also kind of an advocate for timber buildings, just to do them reasonably. And uh people all sometimes confront us. Oh, he says that it's not a problem. You say it's potentially a problem. How how can you speak so differently? And I'm like, yeah, but he is dealing with like two-story tall residential buildings, and I am contemplating uh a hundred-meter-tall skyscraper out of timber as a completely different problem. And the one of the main differences is how soon the fire brigade can start their operations because that's a timeline that competes with the fire growth timeline.
Björn Maiworm:Oh, oh, oh. That that data is heavily discussed between the chiefs of the fire departments. Yeah, they like it because they like it and they dislike it at once. Because let me let me help you. We don't have data, but I I now have, but I didn't publish it yet because I must show the chiefs. How long was the time frame between when the fire started and when you when it was discovered? So when did they call in how how much it was in the hidden phase, let's say. Yeah, so how long do we did it take? Approximately. So, and because if you design a fire department, where to put the stations? In Germany, we have an isochronical model. So somewhere between eight and ten minutes, we need to be on scene starting from the call. Okay. So it's like circles around the fire station.
Wojciech Wegrzynski:It's not that the call is not zero.
Björn Maiworm:Timestamp, you call. Yeah, and we arrive on scene. Eight to ten minutes. We have millions of data sets. But what we didn't have was how long does it take after arriving, after pushing the status button, I arrived on my radio until we start rescuing and firefighting. This is this very data. Yeah. And what's interesting, and I have a bet with my fire chief going because he introduced a new scientific project called Flash Blitzendurm, where he changed tactics, single attacking, like specialized, like special forces working on this to become faster in this aspect. Okay because it was annoyed that it took us like eight minutes average in the fifth floor. And I have a bet running that with my ideas, I can gain more time than he will do with his tactical technical approach, just but not because in this data they have two aspects. We arrive on scene, and then you must look where to enter the building. Where's the entrance door? And the second phase is ordering your attack trip to climb up the stairs and to enter the fire. And if you arrive, for example, again at your single family home, well, it's a single family home, there's a door to walk the street, you enter, and on the left side there's a kitchen fire. So in average, three minutes. If you go in an urban area, like here in Warsaw, in Munich, and Hamburg and Berling, wherever, you have these buildings where what where's the house? What's the house then? Bay in the street. Well, where's the entry? 52. Oh no, it's 55 to B. B. Oh yeah. And then you're looking around and all this. And by experience, and a third of my job is being chief officer in charge. So I have still have possibility to have the practical unit. Usually it's like, oh damn, in midnight, maybe two o'clock in the morning. Where's the damn entrance? And there we lose a lot of time. So the fire prevention department of the Munich Fire Department will introduce data in a fire app on a tablet for all trucks going there. Not pointing the place of the fire in the middle of the building, the dot on the map, but to point the dot where the entrance is. So I don't lose that time. And the bet is, my very cheap thing to do will be more effective than his project. Okay. And this is what I really do like about him. He's innovative. And he says, Well, um Bjorn, you are an expensive firefighter, of course, as an officer I level. But for us as a city, it's very important to have someone there looking around, getting the knowledge back to Munich and bringing it in the system. This is why my job was invented, actually. So because the Munich taxpayer could argue why is he in Warsaw at a conference and listening to really cool guys what they are doing? Because in the end, I'm not just doing the work for the John Fire Department, but for the city of Munich.
Wojciech Wegrzynski:Fantastic, Bjorn. And uh thank you for doing this important job for the city of Munich, and I'm really grateful that we can learn along with you. And uh big thanks for sharing those insights with the listeners of the fire science show. Any uh final words, how would you like to give your final uh call of wisdom to the listeners after this? So I I'll I'll rephrase. You you are continuing this. What lessons do you hope to learn through this exercise? Continuing it.
Björn Maiworm:I hope to learn what are the most important toppings to deal with that have the highest impact. But in other words, from my point of view, and scientifically speaking, fire safety is not a complicated system like statics. It's a complex system. And scientifically speaking, it's an probe sense response system, like we do as firefighting officers. I don't have a standardized IKEA design plan how to fight a fire. We learn as we walk. This is I want to encourage engineers to think out of the complicated box and to allow themselves to enter the complex branch.
Wojciech Wegrzynski:I think one thing that that that is that you're doing this exercise continuously. You said those data points converge. What would be very interesting, and you have to call me if that happens, when something goes out of convergence, when you see something has changed, you know? Wooden constructions. Yeah, right enormously. Yeah. But this is like by doing this exercise, you're also passively monitoring how how what's what's happening right now for for which it will take decades. Yeah. But if you if you don't do it, if we don't have the questionnaires and we don't model that in decades we still will not know. Thank you, Bjorn.
Björn Maiworm:Thank you very much.
Wojciech Wegrzynski:And that's it, thank you for listening. We went through 900 uh fires in Germany, but Bjorn has uh almost 2000 in the database, so many of the things he has said goes even beyond the fire technology paper, which I actually highly recommend to anyone. The link to the paper is in the show notes. So if you would like to look at the source material, look into the tables, look into more detailed description of the failures of fire safety systems and regimes, please uh go and do that. I think Bjorn presented a quite an interesting viewpoint, philosophical viewpoint on on where the fire safety should go and how much should change. And it it's it's kind of interesting. You know, we we are able to narrow down the areas where the problems are, though I'm not so sure if the solutions are with us, if you know what I mean. If the problems are in residential housing and they come from social status, you're not gonna solve them through fire detection. If the issues are with the retirement houses and you are incapable to get political will to issue new legislation and increase the safety there, it's it's not a fire safety engineering problem. Like we know the solution, it's just not embedded in the law. And and contrary, if we know that something doesn't work, it's very difficult to remove it from the system to know to to to create some sort of fresh space where different measures could be installed instead of the the existing ones. And and finally, some of the considerations of Bjorn about uh mass timber are very, very discouraging to be honest, if they increase the likelihood for floor to floor fire spread or compartment to compartment fire spread. So tremendously that this really looks like a potential problem, and we know that it could work like that because of the additional fuel load. I I really appreciate how he said that it's not about fire resistance. Anyway, this task is ongoing, the German collision. Are still collecting their statistics. I know there is a follow-up to the Eurostat project, so I hope we will get even better statistics in whole Europe already. I know there's a big project revamping the statistics in the US. I will get in touch with people who are doing that because I also think it's interesting. And I hope we will continue this collective learning exercise from the data we can achieve because the best we can do for people who were harmed in those tragedies is to at least learn something from it to perhaps prevent them in the future. That's what I would like. Anyway, that would be it for today. I hope you have a great day, a great week, and I hope to see you here next Wednesday. Thank you, bye.