006 - EV's, rapid fires and car parks

Welcome to the Fire Science Show. My name is Wojciech Wgrzyski and I will be your host Hello, everyone. Welcome to the session six of the fire science show. My name is Wojciech, and I'm all on my own in here and today. Today we're gonna talk on car park fire safety. In light of the new challenges introduced into the car parks in the form of the electric vehicles and battery powered vehicles. In the last week episode you've heard discussion with Roeland Bisschop from RISE, who has actually burned some of the electric vehicles which is quite a rare thing in fire science and has great experience in battery fires. And with Roeland, we've discussed a lot of aspects on the fire safety of batteries, lithium ion batteries, in particular, also in in relation to the electric vehicles and the challenges posed by these vehicles. So if you've missed episode five, definitely check it out because there's some priceless knowledge shared by Roeland in there and I have definitely learned a lot from that discussion. In today's episode, I'm gonna take a different look on the problem of the fire safety of car parks. So we're gonna discuss what can happen if an electric vehicle burns in the carpark, how the building automation systems can deal with that. And is it truly a new challenge? Is there anything to worry about? So I'm to give you a background how I got into this topic. The electric vehicle fires are something in our industry that you often see in social media, you often see them in in like, television reports. They're just impressive visually and and very, they bring a lot of attention to the problem because there's something new; they're in a way exciting, they look different. They seem very dangerous. You learn about the challenges of firefighters in extinguishing them. So yeah, definitely they make a great new story. This fires certainly get a lot of attention, maybe even more than they deserve. Yeah, up to a point I was not really interested in them even though I'm, I'm a car park guy. If you if you didn't know me, I've studied car park firesafety for like a decade. With my colleague, Dr. Grzegorz Krajewski we have written a book in Polish about designing smoke control in car parks. I'm involved in CEN workgroups, where we build new standards for smoke control and car parks. And I personally do design smoke control in car parks in Poland. I've done a lot of such designs and then... one day, I take a look in the internet. And there everyone is talking about this fire in Shanghai, I popped the video and

there's a vehicle standing, parked in the garage, and nothing happens, nothing happens and then boom, huge cloud of smoke jet fire emerging from the vehicle, quickly obscuring the field of view of the CCTV camera that was placed in the carpark. And I must say when I saw this video, I was truly shocked. It was something that that really struck me. I remember that the same day, I was texting to Professor Rein, I told him this this car park fire was something from not not from this world. Like I don't think our infrastructure is ready for a threat that develops that quickly as this fire and I couldn't let it go. Because I was working on the carpark project, on the same day, for one of the skyscrapers in Warsaw, I stopped the calculations that I was doing. I've quickly written the new heat release rate curve for my CFD in which I've just placed one megawatt of heat release rates to be released immediately after the start of my simulation to simulate very quickly growing fire. Like an immediately growing fire. Just to see what will happen in that in that car park that I was, that I was designing the smoke control systems for. And in the morning I wake up to see the results of the CFD and they are absolutely dreadful. In my evacuation time, in my first three, four minutes of the CFD, where I usually had my car park fairly free of smoke, at least in a way that would allow you to evacuate safely from the carpark...half of the carpark is filled with smoke. Which if using my standard design fire curve, I never seen such a quick filling of over over carpark with smoke. So while that was something that that really struck me, then and the next move was okay, so if this happened in my one simulation, I wonder what would be like a general outcome of such a fire in a gneeric carpark (if you can call any carpark generic.) And yeah, that's how my research in in this in this area started. When I calmed myself a bit and built some distance from this, from this video from this fire in Shanghai, when I started learning to truly understand what's happening, I quickly realized, to understand the problem, we would have to subdivide it into three separate aspects. (1) The first aspect would be the probability of the ignition of a battery inside the vehicle. Because it's the battery pack fires that we are afraid of, it is the battery where the jet flame emerges from, it is the battery that creates the cloud of of toxic gas, not not upholstery, not cables, not tires, it's the battery. So in fact, all the other elements are in classical vehicles, in internal combustion engine vehicles. So if there is something that differentiates between internal combustion engine vehicles and electric vehicles, then is the battery back and the powertrain. So if we want to understand if the if the cars, electric vehicles burn more often than classical vehicles, if there is an increase of the risk, and risk is inherently connected to probability, we need to understand the probability of battery fires. And that's something I still don't have a perfect grasp on. I don't want to talk about that too much, because I don't think I'm an expert in, in this field. The great thing is that I have a podcast now. So I will bring proper experts to the subject of, of probabilities of battery fires and the chemistry of battery and how the combustion of the battery the interior of the battery pack goes on. I already have a guest in mind, and actually, they're already invited. So yeah, it's gonna be a great episode in the near future. However, today, the probability is not something I can really give you a big insight on. (2) The second aspect that we have to understand besides the probability is how does fire of battery propagate? How does it develop? What is the course of the battery fire, because if you take a look at the classical vehicle, I always said (and that's based on my analysis of many, many fire experiments on full scale vehicles, in various laboratories in the world) the fire of a vehicle goes through phases. And these phases are related to the say, geometry or the architecture of the vehicle. I mean, you can have a fire in the compartment of engine. And these fires do not tend to be extremely large, because there's more mostly cables, oils, and things like that burning, you can have the fires of the upholstered interior of the vehicle. And these fires can be very big. But to create such a fire, you need ventilation. So you need to get rid of the windows of the vehicle. And if you take a deep look into the fire tests carried in vehicles, you will see that many of these tests had windows a little bit shut down to promote some entrainment in vehicle. Because otherwise, it's difficult to set it on fire if it's completely sealed from from from the outside. And the third thing is the fuel. I mean, the the vehicle carries like 50 - 60 liters, or well, actually based on my podcast demographics, maybe I should say 20 gallons of gasoline or diesel inside, because that's the thing that powers it. So it's all conveniently placed in one space, which we call the fuel tank. And if there is a failure of the fuel tank and this, this fuel is allowed to spill, then you will have a very quickly growing very large fire. So the growth of the fire in a vehicle is not just a function of time, it's not alpha t squared correlation. Maybe it is for some parts of the vehicle, but not for the whole course of the fire. And the way how the fire will grow will depend on these events that happen during the fire, if windows break if you break the fuel tank, if the fire can penetrate from engine compartments into the interior of the of the vehicle, these evenys will will drive the growth of the fire. And now we more or less have this sorted out in the form of the design fires for car parks. Which includes different phases of growth of the fire, which include this, this different events hidden behind the heat release evolution within time. And then you have electric vehicle, which in which the fire of the battery can go through a completely different course than what we know so far about vehicle fires. And that was why I brought Roeland last week, because he's the guy who knows how it looks. And he was kind enough to share a lot of insider knowledge on on how these fires progress, how these fires look, what they produce, and also how they can spread between vehicles and what is the conditions to ignite the next car next battery back, because it's also something that will determine the growth of the fire in the carpark like globally. So the first aspect probability, how often will they ignite? The second aspect? How will the fire develop? And will it be much different from the internal combustion engine vehicles fires. So so that was the aspect number two. (3) And aspect number three, the one I feel I even competent enough to talk about is the consequences of such fires. If we make some assumptions like if the fire in Shanghai happened, it means they can happen. I'm not sure what probability of such a fire to happen is. Or if it's even possible that this fire happens again, because maybe there were some improvements in the battery technology that prevents such a such a cascading failure of the battery anymore. But I don't know that now. So I must assume that if it happened once it can happen again. So for me, I do not really care that much about probability, I assumed that the fire like this will happen again. And I want to solve that. So that's that simple assumption solves my issue of not knowing the probability of such a fire. In terms of development, Roeland said that there are different cases that the fire of a battery can grow. It can be a very rapid development, like you've seen in Shanghai. However, Roeland mentioned it was something like very extraordinary, not, not something they see every every time they burn the battery in the lab, that that is kind of reassuring. But it's also possible that the fire grows for a very long time hidden away and concealed somewhere underneath the vehicle, and then just in few seconds grows from very small to very large. And this incubation period can can last 10 minutes, 20 minutes, 30 minutes, we have no idea. And yeah, from my perspective, for me, the absolutely worst scenario is one in which the fire is concealed without being detected by the building for long enough to get into the cascading phase, where it suddenly grows into very large size. And that's what I've called, for my purposes, a rapidly growing fire, a fire that was concealed for a long time. And then from the moment, it starts to give cues outside of the vehicle, from the moment you can spot there's a fire going to the moment when the fire size is a relatively large period of time between these two events is very short. And from our perspective, from the building perspective, because we had no idea that fire wasn't going from the first cue to the moment in time where it's dangerous, it's a very short period of time. And that's what I call the rapid growth. And, yeah, this is something that my opinion would distinguish the electric vehicle fires from internal combustion engine vehicle fires, minus the fires in which you have a very early rupture of the fuel tank. That's also something to consider because if if there is a very early rupture of the fuel tank, like Roeland forced in his experiment, which he explained in in Episode Five, they've placed a pan of fuel underneath the tank, which was made of plastic. So there was a quick failure of of the fuel tank, which led to a spill of the gasoline and created the pool fire underneath the vehicle. So that's a that's also an example of extremely rapid growth of fire that you don't normally see. So here we are. If we would like to understand what would be the consequences of, let's say electric vehicle, fires in car parks. The biggest difference are the ones that will grow rapidly to heat release rate that's immediately dangerous. Now, the big question is, what would be that heat release rate and how can we actually solve this fire dynamics and while that was quite a journey to get into that, I cannot say that we have solved the issue because we don't have a good answer of what is the heat release rate of electric vehicle firing an early phase, when it's going into it through our rapid development. So in order to be able to do see the calculations of carpark fires, including this electric vehicles, we have to assume something. So we've created this six artificial fires, six design fires for our needs, we've assumed they will grow from zero to a certain value of heatrelease rate within 30 seconds linearly, and then remain flat at that value of heat release rate. And the values were from 250 kilowatts to one and a half megawatts, were with 250 kilowatt increments. And this, this gave us six design fires varying with the size. And yet today, I'm not able to tell you which one represents the electric vehicle fire the best. But however, I can go from the other side, if you would take a classical design curve for carparks. Like the one that we commonly using in Europe, which is called the TNO design curve. That's based on experiments in in, in the Netherlands from the 1999. This design curve, I really like working with that one because it has very nice plateau at low heat release rate that simulates the, let's say, medium sized vehicle fire. And it takes like nine minutes for this fire to start growing into very large fire. So I have this part of the curve that for me represents the conditions that I will have while evacuating people from the carpark and then the fire grows through to large size, which in a way simulates the conditions that firefighters would met when they enter the carpark. So for me that's a complete package, because in one simulation with this transient development of the fire, I can I can have both our evacuation response and firefighters entrance. This curve, it goes from zero to 1.4 megawatts within four minutes. It's linear growth. And when we do our our design curves, this six rapidly growing fire curves that I've mentioned, this curves if you take the 750 kilowatt one. And if you calculate the total energy released within the first four minutes of that curve, it actually matches the release from the TNO curve, and it actually quite well matches the release the total release from alpha t squared fire with the fast coefficient. So in a way, the 750 kilowatt hour curve is releasing the same amount of smoke and heat as we would have in a classical design fire. It just does it quicker and with the lower peak value. So I hope you follow me...I'll try to drop a link to my paper in in FPE extra that I've written like a month ago, and there's the curves are illustrated in it. So that's going to be much easier than trying to follow the numbers from coming from my head. Anyway, we've defined this expires and we had this TNO curve, we had the alpha t squared curve. So we decided we want to check what will be the consequences of a fire in a car park in a rapidly growing scenario versus an usual scenario. Of course, you need to define some goals of such analysis analysis because it's it's pointless to just look at temperatures or some other measurements. So we've defined some aspects that we want to learn from this analysis, this numerical analysis that we performed. First, we wanted to quantify if the heat feedback from the upper layer of smoke in this car park can promote a very quick growth of the fire in the carpark that's something you can actually calculate and you can see if what's what's your heat flux radiated from the smoke to the target that goes around the one that's your source. And when you have that you can pretty well guess if the fire would spread very quickly or not. We're actually advancing this this particular part of the research into a separate research item, where we will implement the methods developed by Mohd Tohir with with Mike Spearpoint where they analyzed the total, let's say thermal dose that needs to be applied to a vehicle. They they've call it the flux time product, the amount of energy that needs to be submitted to a vehicle at a critical radiance that will cause an ignition of a bumper trim or tires or any elements of the vehicle that can be quickly ignited. So yeah, that's for the future. But for now, for this preliminary analysis, we wanted to see what will be general consequences of the fire in the carpark in terms of temperatures. We wanted to see if occupants will be able to escape the carpark. So we were looking at the first three to four minutes of the simulations to see what conditions inside the carpark we have, when we put the rapidly growing fires in them and traditional design fires in them. Then we also wanted to see what would be the conditions after let's say 10 to 15 minutes when the firefighters would access the carpark. So that's also part of the investigation because we want not only want to get the occupants out of the building, but we also want the firefighters in the building. So and I think it's quite important when your car park is a part of, let's say a larger residential building, for example, like like we commonly have in Poland. So yeah, this were the goal is to check whether it will be like the total damage by the vehicle to the carpark and will it spread or not? That's this thing number one, will occupants be able to escape? That's the thing number two, and will firefighters be able to access the carpark that's the thing number three, and now the study itself. Now as I mentioned, we had six design fires for the rapidly growing scenarios, we had them do you know design fire, we had an alpha t squared, some design fire, we also played a bit with the car park, we have tested five different heights of the car park. So they've ranged from 2.4 meter up to 3.6 meter with 0.3 m increments. So yeah, height was very important in our analysis, because from our previous studies, we have already understood the impact the height has on the carpark smoke control systems. Talking about smoke control systems, we've also placed a lot of systems inside the car parks that we are modeling. We've used duct systems that there's basically a bunch of ducts distributed underneath the ceiling with exhaust exhaust points on top of them, which are used to remove the smoke from the upper smoke layer. And we have three types of such a system. We have also used jetfan systems, a system that uses impulse ventilators to push the smoke in one direction in the car work to make sure that one side of the carpark is free of smoke and all this smoke is transferred horizontally through the carpark into an exhaust point at one of the walls of the carpark. So we've tested if I'm not wrong five types of such system, we've also had one of the carpark with no installations at all. So yeah, that's the variables related to the smoke control. And overall, it was all something like 480 CFD simulations to be done. So that that's, that's quite a lot of CFD simulations. To be honest, I think for the particular part related to the rapidly growing fires, it was something like 360 that were relevant to this part of the study. Because the project was such huge in terms of the amount of CFD that was performed, it's like literally impossible to run a 480 CFDs on your own and just know, define them by hand. So we've invested quite a lot of time to, to develop some code that would write the model for us. We've used FDS solver, which is fantastic for this type of parametric studies, because you programme the model in lines of code. So we've written a script that created the FDS code. And we just supplied it with the parameters of the car park that we wanted as a result, which were the heights, the type of systems and the type of fire and the horizontal dimensions, which if I'm not wrong, they were like 60 by 40 meters. And then the computer created all the case files necessary to run the cases. The same script did also actually prepare everything we needed for the for the CFD study, it was sending the cases to the supercomputer that we have in the office. It was managing the simulations so when one ended it was starting the next one. It was making sure that the usage of the CPUs is optimal, and stuff like that. In the end, it took something like 78,000 computer hours, or CPU hours to calculate all of it. We've also forced the computer to analyze the results for us, in terms of create the plots of visibility, create animations, create all the data necessary to understand the results of our CFD, because if I wanted to, like take a look at every single simulation out of the 480 of them, and if I spent like 10 minutes on each of them, it would be more than like 80 hours of analyzing the results, which is like something like two weeks of work, which I really don't want to do. So yeah, we got, we went easy. More than that. We got the data pre processed for us, which is very convenient. And then we we've jumped into analyzing learning and making conclusions. So yeah, finally, we're here. So what's the conclusions of our rapidly growing fire study? The first thing we have noticed, and it was really obvious and powerful at the same time, was that the single most impactful variable determining the safety of the car parks in our study was the height of the carpark. And I will be honest with you, for the lowest high carparks like 2.4 meter, we have not observed tenable outcomes within the evacuation time. It means that within the evacuation times, which we have assumed, is between three and four minutes for this car park, we did not have a case in which conditions would be completely tenable in the whole of the car park and in that simulation, and after three, after four minutes, we usually ended up with literally more than a half of the carpark filled with smoke. So that's a very, very bad outcome. If you have more than 1000 square meters filled with smoke that's beyond your tenability limits. And if you want to learn more than the network limits, you should jump into episode number three with Gabriella Vigne, where we've discussed them in quite detail.. So if you have a very low height car park, and in our outcomes, I mean in all the cases, including the ones where we had these powerful smoke control systems in them, because we've also we're testing some really powerful smoke control systems in the carpark. And even for these cases, the results were very unfavorable. And if you start thinking about it, it may be connected to the way how we assess the tenability in this case, because we determine it at the height of 1.8 meter about above the floor. Probably if you move these heights like one and a half meter, maybe one meter, you will get to a different conclusion. But we wanted to keep this as we do in everyday engineering work. And in that work, we usually assess these conditions at 1.8 meter. So there was no point to change that just because of the of the project we're doing. So for very low height carparks, which was 2.4 meter, we really have had horrible outcomes, even for the for the smallest fires that we have tested. For ptaller carparks. Starting with 2.7 meter, we've started to observe differences between the different types of ventilation systems. So in the most powerful duct system, which had the cubic capacity of 50 cubic meters per second, that's a lot actually if you if you if you talk about smoke control systems, the outcomes were okay'ish. Because of this increased height, we really observe the differences between the smoke control systems in there. The systems that had lower capacity ranked worse, the system that had increased capacity ranked better. So it seems that once you supply sufficient height of your car park you start observing improvements when you include new safety systems in it. Because in the lowest ones, no matter what type of system we've brought, no matter what type of capacity the system had, we never found a good, good outcome. So that's that's lesson learned. In the very tall car parks, let's say starting with three meters and above the introduction of any ventilation system that we've used in our study pretty much solved the case. And we have stopped observing significant differences between the rapidly growing scenarios and the classical design fires. So once the carpark was tall enough, we have not observed significantly worst smoke obscuration in the carpark we have not seen significantly higher temperatures in the early phase of the fire anymore. So yeah, I think in a way, you could say that the car park handled this very early release of large amount of smoke. And once you start thinking about why this height is such a profound variable for for this, I mean, if you want to keep this smoke above the heads of people who are inside the car park, having the car park taller just allows you to have more smoke gathered above their heads pretty much. And yeah, that makes sense. Once you have big enough smoke reservoir, you can manage the smoke for a longer time. And maybe that's just enough to have enough time for people to evacuate, actually in the in the tallest carparks 3.6 meter, even without any system we have had very favorable outcomes for the, for the rapidly growing fires and for the classical design fires. So the height is really impactful in terms of limiting the the heat transferred from the smoke layer to the to the surroundings, because of the increase in entrainment with the increased height of the plume. And because you have bigger reservoir to carry it to have the smoke accumulated in it in a way that it does not endanger the people below it, it also in a way helps to solve the case for the tenability in the carpark So, yeah, that that was quite powerful to see the height being sooo... such an important variable. And at the same time, it's uncomfortable for me as a, as someone who tries to help designers design better car parks, because you know, height relates to the cost of the carpark very much and it it will quickly increase the overall investment costs. You must look at the height of the carpark if we were for example talking about underground carpark. The height means you have to dig deeper, you probably have to use more concrete, more steel to build the carpark so actually that's, that increases the costs a lot, especially if you if the water level in your soil is pretty high, there's probably a depth that you don't want to go into. And sometimes it's just impossible maybe to increase the car park height. So from a designer point of view, from architect point of view, I perfectly understand the issues why we want to seek a compromise height of the car park that would be easy to build, fairly cheap to build, and yet sufficient to just have all the installations fit underneath the ceiling. And just enough for the for the proper operation of the smoke control. And I perfectly understand that we need to build this this, this car parks in optimal height, we don't want to just build a four meter high car parks because we like it, we have to have a good reason for that. And then again, on the second hand, I see the results of my of my CFD study and I see how big impact this this variable has. So it's like really difficult time, you know, because I'm going to have a lot of very, very difficult discussions in the next years of my career with architects trying to convince them that we should build at least 2.70 - 3 meter or more carparks through to just provide some basic level of safety. From the other things that we've looked in our studies, when we were looking into the firefighter operations firefighter access, because these rapidly growing fires eventually reached the same amount of heat as we have in standard design fires. And because at some point the standard design fires would, would grow bigger than then the rapidly ones that we've designed. You can you could clearly see that the let's say classic design fire was much more difficult for the design of the systems for the firefighter entrance. So from that, it's fairly easy to see that with a classical approach, if you use TNO curve to design your car park, or if you use some reasonable value of steady state, heat release rate for the design of the smoke control in carpark. For example, if you follow the British Standards, and you use four or eight megawatts, or maybe you go with with something even larger based on maybe research of Daniel Jouyex, or some guidelines from from New Zealand, you probably go to do even higher, steady state heat release rates to design your systems. If you do that today, I don't think the electric vehicle would make a huge difference to your approach, because the differences are not really once the fire develops, the whole vehicle. Once the fire takes over the whole vehicle as we've discussed it with Roeland last week the differences between internal combustion engine vehicles and electric vehicles are not that profound. Actually, the bigger difference would make if you live in window open, most likely than what the powertrain of the vehicle was. So it seems from the aspect of firefighter response. Obviously, these electric vehicle fires bringing new challenges that we are not able to quantify yet, definitely, definitely very difficult to put out, you have to put a lot of additional effort to localize the fire. By localize I mean, to make it not spread to have it in one spot and not affecting surroundings not growing into adjacent vehicles to isolate it from the rest of the carpark. Definitely that amount of work and water and efforts from the firefighters is increasing in there. But me as a smoke control designer, I believe that my duty is to allow them enter and try to remove as much of the smoke during their operation as I can. And I leave it to the professionals how to how they handle the fire and how long it takes. So from that point, it seems the differences were not big actually, the we've definitely seen that the traditional design fires who gave worse results in terms of spread of the fire from vehicle to vehicle. As I mentioned before, it depends on the heat feedback received by the target vehicle. So in our simulations, we didn't really consider that jet fire behavior of the of the battery fires, because it's very difficult to quantify, because it definitely changes the the physics of the other smoke and it can promote the spread of the fire to adjacent vehicles because suddenly your your adjacent vehicle is exposed to a stream of hot gases behind like like a burner. But here, we did not simulate it directly. But it from my experience in handling the car park fires in designing car parks, it is kind of obvious, you either need physical separation between the parking spots. And in that case, you stop the jet fire at the physical barrier, like a wall between some of the vehicle parking spots. Or you can use sprinklers to pretty much get the same effect of preventing the fire spread from vehicle to vehicle. And I assume in many parts of the world, you will just do that naturally. And probably that's the best thing you can you can do for the car park. So yeah. These are the outcomes of our research study on on what happens if the fires grow very quickly in the car park which in a way reflects the scenario that we envisage for a rapidly growing fire of electric vehicle caused by some sort of failure in the battery and thermal runaway and the cascading failure of the cells that leads to this very sudden the very large very rapid growth of your of your fire. some final thoughts from that? Because definitely the case is not solved yet. I think we're a few steps closer to providing safety in car parks. And I would be far away from stating that we have solved the problem of electric vehicle fires in car parks. But we certainly do know a bit more how to design the car parks in a way that does not really matter that much if the fire development was very quick. So that that's I think a very good thing for engineering For now, and I'm sure that at some point, the science will folks. catch up. And we will receive much more evidence based scenarios to use in our car park simulations. And I'm really, really looking forward to the day where we would have like, evidence based heat release rate curves are evidence based designs fires to be used in car park fire safety. And I would be the first to drop the the ad hoc scenarios that we've determined, I would truly love to have this type of of data to use in my simulations, I didn't have it now. So now you have to do what you have to do, you have to handle the problem. In light of missing knowledge, we cannot just say we we didn't know when we didn't care, and we cannot help design safe car parks, because electric vehicles are the future. For the last 20-30 years, we have been designing car parks that will host electric vehicles we were just not aware of they will. And that's an inevitable future with all the targets set by by the countries, at least in the European Union. But I think it's very similar in many parts of the world, that electric vehicles should be come a major part of the traffic and the civilian traffic in your roads. So if the majority of the car fleet is electric vehicles, you can't ban them in car parks. I mean you cannot ban a majority of the vehicles to be used in in facilities designed to host vehicles. So yeah, if we don't want troubles in 10 or 15 years, with having to design new systems in our car parks to magically turn them into electric vehicle friendly spaces. I think designing tall car parks, and maybe equipping them with sprinklers and some good smoke control systems, I think there's a fairly good solution. And I think from these three items, you can find the very cost effective combination that would meet the demand of your particular project, and would let you design a very safe, very safe space for occupants for firefighters, basically, for everyone. In Poland, where I live, we have automated fire alarm systems almost in every car park in every larger carpark that you would have. So I would say they're very, very common. And one thing is that it takes time to process a signal of an alarm in the carpark. It's not an immediate information that an event has happened in the carpark it's not that the battery will release the cloud of smoke and immediately you will have an alarm notification in your control panel. No. It it takes time. First because the smoke has to reach the sensor. And if the smoke is very heavy, Roeland also mentioned something like that in the last week that they see the smoke sometimes before the flaming ignition starts when the battery just produces a lot of smoke. The smoke is heavy, it doesn't does not have buoyancy doesn't go upwards where your smoke smoke sensors are. So if it does not reach the smoke sensor, the smoke sensor has no idea what's happening underneath it. Even if the smoke reaches your smoke sensor, it takes time for the sensor to trigger the alarm. And once it does, if it is just a single smoke sensor, it will go into pre alarm phase unless it's some very fancy multi detector smoke detection system where you may go into stage two already at that point but usually it will go into pre alarm which means the people maintaining the building will be informed about an events is ongoing but it will be not classified as a confirmed fire yet. This is because we don't want to have every single activation of a sensor start all the fire safety systems in the building because it takes time and sometimes money to bring them back to the original state. So you have the sensor that feels there's a smoke around And then it goes into alarm. And then it might take even minutes to go into into the fire alarm state, it may need a decision of the operator, you may need a second detector to pick up the same smoke. And when you have like two sensors picking up, smoke gets pretty evident there's a fire, it made need to pass a certain amount of time without responsible operator to activate the alarm, which we call the delay time of the system. And this can add up to minutes. If you imagine the the timeline of the fire in your car park, and imagine how quickly it can grow from a very small state into a fairly large state. And then it takes let's say, one minute for your detector to pick up the smoke, then it may take one to two minutes for the signal been transferred to the control panel and actions be taken to start the whole sequence of events in your building in response to the fire. Then, if we're talking about smoke control systems, it's not that you have a signal and it magically starts and there's suddenly flow in your car park. No. No, you would have to close the HVAC systems dampers, you would have to open the fire dampers on your smoke control ducts or in your exhaust point, it takes time to open and close them, then you need to spin off the fans, which also is not usually it's not an immediate action, it takes like 30 seconds to ramp them up to a full capacity. And this seconds add up very quickly. And suddenly your systems become fully operational in the fourth minute of the fire in the fifth minute of the fire. And if you remember from my long talk about our findings? in our safety study, in three or four minutes, we already had untenable conditions. So if there are long delays introduced by your systems in the building, the systems really didn't matter in that very early phase of the fire. And this was the exact thing why I was so scared of this Shanghai fire when I saw the fire develops rapidly in the vehicle. And this brings me again to my first conclusion and the final conclusion of the study, the height matters, because it's always there, you don't have to activate the height of the carpark it's just there is a physical parameter of your space that provides safety. And that's one more argument to vouch for taller carparks. Okay, so that was a lot on on the topic of the making kovorix safer in the rapidly growing fires that we could associate in way with electric vehicle fires, we could also associate them with fires of internal combustion engine vehicles in which the rupture of the fuel tank is very quick. It's pretty much the same story very quickly growing fire to large heat release rate posing threat very early in the building before your systems can react before your occupants. Notice that there's something ongoing, you already may be creating untenable conditions or your evacuation routes. And that's definitely something you don't want to have in your carpark. So I hope you've enjoyed this talk on this subject. If you have not listened to the episode five with Roeland Bisschop on battery fires, and you've just finished this episode, I think it's still worth it to jump into episode five and listen to what Roeland had to say, on the topic of burning vehicles and batteries. I found that really interesting. And I've learned so much from him. And I'm truly grateful that he took my invite on kind of short notice, actually. And we've got that that episode in place. And it made me very, very happy because I have learned a lot. And I know that if I have learned something from the interview, I know you will be able to pick up something for yourself from that as well. So yeah, my goal here is to deliver knowledge in the most convenient way for you to digest it. And I hope that's what you found in Episode Five and all the episodes of the of the fire science show. I will be doing this solo episodes every now and then. Because there's so many research subjects that my group is touching. And I find them all interesting. If they were not interesting, we would not be researching them. So because now I have the podcast, I'm the one to choose the guests. Every now and then I'm going to steal the mic and I hope you will not you will not have anything against that. I hope you have enjoyed this solo episode. In the next weeks. We're coming back to the interviews and I've already interviewed two guests this week. Both were great. I have two more scheduled for for ongoing days. So I'm building up a month ahead of content so you can be sure thatepisode will be waiting for you every Wednesday. And for last thing, I would really appreciate if if you like this podcast, if you like the way how knowledge is being passed in here that that some interesting viewpoints opinions are being shared in here. If you enjoy this, and if you think it's beneficial for you to keep listening to the podcast and you're learning something new in here, please pass this knowledge to your colleague in your office, maybe your coworker, your local firefighter, all the people that that could benefit from that, because I would love to reach as many people as possible. It's free, it's online, it's easily accessible. So it would be great if anyone who can benefit from listening to this show could at least try and see if this is a format that works for them. And yeah, for today. That's, that's it. Thank you very much for tuning into this episode. And yeah, see you next Wednesday. Thanks. This was the Fire Science Show. Thank you for listening and see you soon.