243 - 20 Informal Settlement Fire Experiments with Sam Stevens

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

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

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

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

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

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The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.

Transcript

Why Informal Settlements Need Fire Data

Wojciech Wegrzynski 0:00

Hello everybody, welcome to the Fire Science Show. Fire physics is complex, beautiful and rich. Perhaps the reason I am still a fire scientist and I don't see any better pathway for myself. We know a lot about fires and we know that because for more than a hundred years there have been experimental research that was unwrapping these complexities of fires. And I would dare to say we know quite a lot about building fires. There's some things that we don't know, there's some big things that we don't know, uh but in general we have a lot of knowledge that comes from generations and generations of experimentalists who were looking for answers in the fire. And there are spaces in the world of fire which do not have this experimental background at this scale, and uh unfortunately one of those spaces is also the one which perhaps needs it the most. That is the informal settlement space and our ability to understand fire behavior at large in those informal or humanitarian settings where people basically build their shelters from whatever they can get, whatever they can source in ways that uh address their current needs and problems and issues. They don't have much choice about uh where on how to build them, and unfortunately they often would put themselves in a position where a fire is a hazard, which not necessarily is a hazard that they recognize or choose to to do something about. This uh is something that you've already heard in the podcast. I had Danielle Antonellis from Kindling twice. I had Professor Richard Wolves. We've been discussing the the issue with informal settlements and how to provide fire safety to uh had probably one billion of people who who may be living in such settlements as we teased some weeks ago with Danielle. This experiments come up because Kinling has completed a very large experimental series burning twenty different informal settlement types of shelters to start and see how does the structure and materials used for the shelter change the overall fire behavior and overall fire outcomes. Such a massive project would obviously not be possible without funding and this uh this funding was uh provided by FSRI and uh thanks to FSRI all of this was possible. So actually on behalf of Fire Science, I'm really thankful for supporting such an important mission. And today in the podcast I have uh a chance to discuss those experiments with Dr. Sam Stevens, who's with Kin Ling, who's been there on the ground in South Africa for all of those burns, who's been designing those experiments and uh who for the last uh eighteen something months has been uh playing with the data from those experiments. Finally we we can share some of the findings, show some of the outputs. We'll discuss how the experiments came to to be and we will discuss where uh this data can go further. So without further ado, let's spin the intro and jump into the episode. Welcome to the Firescience Show. My name is Vojinsky, and I will be your host. The Firescience Show podcast is brought to you in partnership with OFR Consultants. OFR is the UK's leading independent multi-award-winning fire engineering consultancy with a reputation for delivering innovative safety-driven solutions. We've been on this journey together for three years so far, and here it begins the fourth year of collaboration between the Fire Science Show and the OFR. So far, we've brought through more than 150 episodes, which translate into nearly 150 hours of educational content available, free, accessible all over the planet without any paywalls, advertisements, or hidden agendas. This makes me very proud and I am super thankful to OFR for this long-lasting partnership. I'm extremely happy that we've just started the year 4, and I hope there will be many years after that to come. So, big thanks OFR for your support to the Fire Science Show and the support to the fire safety community at large that we can deliver together. And for you, the listener, if you would like to learn more or perhaps even become a part of OFR, they always have opportunities awaiting. Check their website at OFRconsultants.com. And now let's head back to the episode. Hello everybody, I am joined today by Sam Stevens from Kindling. Hey Sam. Hey Voyak, thanks for having me here today. You're very welcome here today. And today we're gonna finally discuss the massive experimental program that that was uh carried out uh a year ago, I believe, in in South Africa.

Sam Stevens 5:25

Yeah, about 18 months, I think.

Wojciech Wegrzynski 5:27

18 months uh flies so fast, it's ridiculous. But anyway, finally, finally, we get to talk about uh the results and finally you can talk about some findings. I know the program quite well. The listeners don't know it uh probably at all. So let's introduce the subject, which is the informal settlements. Maybe you can give me the background, uh how this all started, where did it all start, and and what was the first research idea that you went with?

Sam Stevens 5:55

Yeah, so this this all started back before I joined Kindling. Um so I joined in 2023 after I finished my PhD. Um, Kindling had a very generous funding package from FSRI to do some experimental work to look at um informal and humanitarian style shelters. So historically, and I mean sort of in the past decade or so, there's been a lot of work done on informal settlements in Cape Town and South Africa specifically, just because it's quite accessible from the academic space. There was a very good partnership between Stellenbosch University and Edinburgh. And there's a lot of sort of momentum or interest in uh the idea of sort of improving fire safety in the developing world, but it it remained very restricted to sort of one kind of shelter typology, which is essentially these like metal boxes, these sort of corrugated metal style of shelters that you get in South Africa, in a lot of sub-Saharan Africa, and in other parts of the world. But the focus was very much on Cape Town. But out there in the world, there are people using a huge variety of different materials that we don't really have any data on, sort of shelter designs that we don't really have any data on. And they're building them in sort of fairly dense settlements. In some cases, it's even humanitarian organizations coming along and trying to help in sort of disaster response, providing materials. Um, a lot of the time it's tarpaulin materials. So we wanted to move from just understanding these sort of very simple metal um style shelters to actually exploring the vast array of materials that are used, predominantly around the question of like large fire spread in these settlements. Uh so we're kind of in the space of like large outdoor fires, but we're not exactly woo-e fire, we're not exactly wildfire because we are talking very much short-range structure-to-structure fire spread.

Wojciech Wegrzynski 7:56

I know we previously in uh Edinburgh there was uh Project Iris that was focused on informal settlements. There was a lot of good work in that. I remember uh specifically paper about 20 shelters, yeah, like large outdoor experiment with 20 shelters burned down. That was brilliant. There was amazing touchover stuff. Uh, I think Mohammed Bashir authored that paper. Awesome, awesome, awesome fire physics. Uh, but iris was mostly those corrugated steel uh type shelters, right? And and this is just one topology out of many, right?

Sam Stevens 8:29

Yeah, so I mean the first the first step in the work before we even got to the experiments was asking the question of actually what is out there, and and there's no easy literature to assess to like find that out. We spent a lot of time just trawling through we don't have informal settlement eurocode that dictates it's it's basically yeah, there's the whole point of like people build it as yeah as they can. And we were we were having to go through like report after report uh from the UN or the Red Cross or various different organizations that were like, well, in this year, in this flood response, we provided these materials, and there's a few pictures of what the shelters looked like. So we're coming, we've got a a database now that's sort of got, I think, about 450 different shelter records entered into it that are you know from I think 90 different countries in the world, and anything, you know, mud shelters, that shelters, that is bamboo, um, but all these different materials that you know people harvest locally or find locally, or that's what they have available to them, that's what they build their homes out of.

The Gap In Humanitarian Fire Guidance

Wojciech Wegrzynski 9:36

I I think the listeners already uh had a good experience in the fire science show uh hearing about that. We we had Danielle Twise, we had Richard Walls uh talking about the background. So we I think we the common understanding is that there is potentially large fire hazard related to those informal settlements, and uh unfortunately solving those issues is not the top priority for the people who are under the hazard, they have uh other things they they worry about. Anyway, um, in terms of defining those shelters or managing the landscape, do we even have before the project starts, do we even have some sort of like guidance recommendations on how to safely build them? Like what does the landscape look like? And then hopefully at the end of the podcast episode, we can discuss how the landscape looks after we we finished this.

Sam Stevens 10:25

Yeah, that's a great question. And I guess that sort of frames the research really well. Um, there isn't really fire safety guidance for, I'd say we call it the the humanitarian sector. Obviously, there are informal settlements existing in countries with regulatory frameworks, it's just the regulation isn't necessarily applied in those spaces. But then there is this sort of humanitarian response space where there's lots of organizations working. Um, and that can be anything, as I say, from oh, this small disaster has happened, and we just need to supply a few materials to help people recover their homes to massive displacements of people and organizations from the ground up building camps as quick as they can. Now, there is in existence or various guidance documents. One of them, as far as I'm aware, one of the most commonly used is called the Sphere Handbook. It's this massive document, it's like 450 odd pages long, uh, that is supposed to advise camp practitioners on sort of all aspects of how you should build a refugee camp, basically. And for you know, all kinds of drivers, like prevent against flooding, to provide adequate lighting, to provide adequate toilets, like literally everything. Yep. And within this, you know, hundreds and hundreds of pages, there's a total of nine lines of text committed to the subject of fire safety. And it's kind of as you say, right? So it's it's not that people don't necessarily care, it's that people have potentially 101 other things that they perceive to be, or maybe even are, more important than fire safety. So that fire safety kind of is a little add-on at the end where you try and you know do what you can, but it's it's not really the driving factor. Um, and with that in mind, the guidance for fire safety ends up kind of being, I would say, pretty rudimental and not very data driven. And it's just kind of loose rules of thumb that have been passed into these guidance documents without any kind of data to support their use. Can you give ex examples? Yeah, I can give a couple of examples. Um, the the most obvious is probably like shelter separation distance. Because this there's this thing of, well, if you put two shelters X meters apart, then you know that improves fire safety. Doesn't say it will stop fire spread, it doesn't say it will slow fire spread, it doesn't say what those two shelters have to be made of. It's just for any two shelters, if you have them and the in the shelter guidances, if you have them two meters apart, you're doing well. Even better, you should have them at least double the height of the shelters apart. And now that's getting, you know, for any reasonably sized shelter for people to live in, that's probably you're looking at four or five meters as your minimum separation distance there.

Wojciech Wegrzynski 13:16

Which doesn't really fit to the image I have in my mind of these uh neighborhoods.

Sam Stevens 13:21

Yeah, so space is at a premium, you're giving people this very high target of what fire safety is by saying you need all your shelters to be four or five meters apart. But if you can't do that, then actually you can cut it to two meters. But it doesn't then contextualize that with well, actually, if I have a shelter, you know, that we can build out of concrete bricks, uh, that two meters, you know, fine, we don't really care. They can be half a meter apart, maybe. And you know, as non-combustible material, you're probably okay, versus, oh, actually you're building everything out of timber and thatch and bamboo. Yeah, whatever. So, like, you know, there's no contextual shift in the guidance for what materials are um or so what materials are being used. And you know, that's even kind of summarized in this other line that says use fire-resistant materials where possible, like if you can. It doesn't provide any further context as to what a fire-resistant material actually is. Like, is there some qualifying factor that makes a material fire resistant? No, just use a fire-resistant material if you have one to hand. And I think it's reasonable to some extent because you can imagine you know, people working on the ground have some innate concept of like what burns versus what doesn't burn. But that's very different to than to having you know a nice bank of experimental data to kind of compare and contrast different materials and say, um, well, if you have bamboo mat, then this is going to be your common fire spread outcome. Um, or if you're using thatch, then this is going to be your common fire spread outcome. So we've been approaching the analysis of the experimental data from is like, well, what how do people want to approach what fire safety practice looks like on the ground? And then how do we speak to each of those, you know, in rules that people are sort of using already?

Wojciech Wegrzynski 15:14

I would say, you know, Sam, if I look at that, I also feel like those guidances have to be very simple. Those guidances probably cannot relate to a specific testing standard because if people are obtaining materials in whatever way they can, the standardization is not gonna really solve. Like you cannot put a E C E marking on anything, on everything for this context. So I I think there's general guidance, those are actually not the worst guidances I've heard. Like make a two-meter separation, make a use fire resistance. But uh, as you said, like they're probably insufficient in terms of what they mean, and and and what you've brought before the lack of experimental or just lack of proof that it actually provides you specific uh result in terms of safety.

Choosing Twenty Shelter Types

Sam Stevens 16:06

I completely agree, and that's I mean, we can maybe circle back to that in the end because that's been a real challenge in how we've then used the data that we've analyzed. We've gone into all this complexity and we want to you know share that complexity, but at the same time, the people we want to share it with and the end users, they don't have time for the complexity. So then how do we reframe our analysis to be communicated in simple terms that is better than what exists already but isn't so complex that nobody has the time for it?

Wojciech Wegrzynski 16:36

Um so the data you said 450 different shelter topologies uh from what uh Danielle's Paul's here uh last time she's been on the podcast, is it was, I believe, 20 different settlements. So, uh, how did you narrow down the 450 down to 20 and what they are broadly representative of?

Sam Stevens 16:55

There was no fancy statistical methods, and I will say that it wasn't like 450 unique shelter types. So it was across the shelter database were then well, what's the most common? Okay, and particularly across the way we kind of broke it down was across different countries and then different uh climate regions as well. So out of that, I mean you do have the odd wacky shelter of really unorthodox materials that appears once in one report, yeah, um, that you don't then see again. But there are materials that are obviously very common uh across lots of different places. So we ended up kind of 12 to 15, maybe most common, and we wanted to sort them into categories as well. I guess going back to the idea of like how do you make guidance simple is if if we could through experiments show that you can like loosely categorize different materials or different shelters within the same car in the same categories and say, well, there's the sort of a risk level inherent with each of the different categories, then that would potentially simplify things. It turns out it has to be a little bit more complex than that, but the initial intention was to group shelters by categories as well. So uh the the categories we went for were combust, or so it was grouped by the combustibility of walls um and roofs. Okay. By combustibility, I just mean does it burn or does it not, uh, in simple terms. So the first category being non-combustible walls, non-combustible roofs, things like sheet metal walls, sheet metal roof, um, or we had mud walls and a sheet metal roof and cement block and a sheet metal roof.

Wojciech Wegrzynski 18:33

Okay.

Sam Stevens 18:34

Um, as an example. So non-combustible or non-combustible, more or less. And then and then you kind of get the idea the next category is combustible walls with non-combustible roof, so that would be like a timber walled shelter with a sheet metal roof. Then we had uh non-combustible wall but combustible roof. So an example being uh mud walled with a thatch roof, and then both combustible walls and roofs. Uh, how many categories is that for we're at? And then the fifth category we ended up with was tents because we didn't really know how where they were gonna sit. So tarpaulin tents, there's a lot of interest in the sector, obviously, with tarpaulins, because that's a a huge amount of what the humanitarian sector distributes is basic tarpaulins to you know either repair homes or to build tents completely out of tarpaulin. Um, sometimes they provide full tent kits. Uh, so we weren't really sure whether they were gonna sit in a combustible category. Um, and tarpaulins are very complex and a whole different story that we can maybe come on to later. But that was the sort of the loose categories and materials. It was actually quite a narrow set of materials in the end. We narrowed it down to like timber, sheet metal, bamboo mat, split bamboo. So if you like take the bamboo column and split it down the middle, thatch and and then tar pollen. So like the common shelter types that exist across the world they are relying on a fairly narrow set of materials, like whatever's naturally occurring. You have various different species of bamboo, fine, you have tons of different species of timber, yes, yeah, fine, but as a as a material, timber versus split bamboo versus like these sort of woven bamboo style mats are quite easy distinctions to make. But you didn't use any kind of like insulative material like sandwich panels or no, so that that was a typology that that did come up in the database quite a bit. Is there are styles of humanitarian humanitarian shelter, pre pre-built kind of container style uh shelters that often the walls and and roof are made out of these insulated sandwich panels, but we didn't really want to go down that route because I don't think we had confidence we could necessarily build one of those ourselves from just sourcing material, and then it was a case of approaching the organizations that build these things and be like, hey, can we have one and burn it? And then of course they're reluctant because they don't want their thing to be shown up as potentially dangerous, and that's not to say they necessarily would be compared to other styles of shelter.

Wojciech Wegrzynski 21:09

I mean in this particular research problem, I I don't think it's fair calling any of those materials dangerous. Well, perhaps some are, but we we'll get back to that later. But uh, you know, it's more about none of them are really like fully safe in the ways how how it's built, because like if you would like to have like a fully safe building, you'd build it to a building code, uh, uh and then it would stop being the informal settlement. And in here, instead of like pretending like you should do everything according to a code, we'll like I I like what when Danielle said that we um don't really have much to offer to those who don't meet the minimum requirements of the code, like that there's not much you know below. Well, in reality, there's a whole spectrum of solutions that can be there. Okay, we got the materials, we got the kind of topologies or combinations of those materials. So we were testing.

Building The Outdoor Test Setup

Sam Stevens 22:00

A single uh settlement or again multiple uh just single, right? Yeah, so every experiment was just a single shelter. Um we use the the ISO room dimensions, so very similar to how the the Iris fire project set out their experiments. So there's what 2.4 by 3.6? Yes, 2.4 by 3.6, and then 2.4 high as well. Um wood cribs, two wood cribs in. And then I sort of I alluded to it at the beginning, but that this is really a a problem of short-range fire spread between shelters. So what we're primarily interested in is heat transfer to the immediate surroundings in all directions, which meant uh a huge amount of external instrumentation, particularly to measure the heat fluxes. The important, or you know, we wanted to assess the relevance of we had sort of a door and window in every shelter. Okay. Um so traditionally, compartment fire, you're expecting external frame from the opening. So we focused in there, we we had some heat flux gauges or a heat flux gauge at each one.

Wojciech Wegrzynski 23:06

On the same facades? The door on the window?

Sam Stevens 23:08

No, so they were on opposite facades. Okay. Yeah, so we they they were both in the so if you've got a 3.6.2.4 uh floor plan, the door and window were in opposite corners on the 3.6 meter long walls.

Wojciech Wegrzynski 23:22

Okay.

Sam Stevens 23:22

Yeah, so then a huge number of uh thin skin calorimeters. I think we had 60 thin skin calorimeters around the shelter in kind of these spokes coming away from the shelter at various positions, with the TSEs being at one, two, and three meters away. So we're assessing heat transfer, I guess, at a variety of distances away from the shelter and at all locations to kind of assess well, what's the difference between heat transfer from an opening and heat transfer from an end wall and heat transfer like along the diagonal looking at the shelter? Because there just really isn't the data out there to kind of differentiate between different styles of shelter. And going back again, I'll reference the Irish fire projects. Again, they have these sheet metal shelters. The most common place to be measuring heat flunks is from the opening because that's where your external flames are going to be. But a real question around the experiments we did was well, beyond just external flames from the openings, are there particular hazards associated with different materials and different styles of shelter? And can we get fire spread from in different locations, not just at the openings? I think the very obvious answer to that question when we talk about the results is yes, because if you have a combustible wall that's completely uh in flames, then there's going to be a huge amount of heat transfer from that wall. Same with a roof, if you have a roof opening up. Yeah. And I guess uh again, I'll talk about this more in the results, but there's a question of like to what extent can you stick to conventional compartment fire dynamics as your understanding of how a shelter burns. But to come back to uh what we're measuring, I should expand a little bit and say these are um these experiments are all happening in a field on a farm in the middle of rural South Africa. So we had to come up with some reasonably innovative ways of measuring things that you know might be a lot easier under a calorimetry hood in a lab. So the entire shelter was built on a very large platform scale. So I think it was sort of slightly larger than the floor plan of the shelter itself. I think it was about three by four meters. Um so we but we were measuring mass loss to I would say do a robust measurement of heat release rate. Of course, it's not going to be robust if you have parts of the shelter falling off and various different things like this, and no calorimetry. But it was it was very useful when we look at the data sort of on the back end. It was very useful in gauging the different orders of magnitude of fire size between different shelters and different uh materials.

Wojciech Wegrzynski 26:04

What's the relevancy of the crib? You mentioned you put two cribs inside as your source. What was it based on? Just to get the threshold, or is it was it representative of some specific fuels in the in the in those types of settlings?

Sam Stevens 26:19

It is, I think, going in what we use as a kind of a standard experimental fuel load, right? So they were sized and designed to be an approximate fuel load of uh like an informal home. There is some fairly limited data describing fuel loads in informal homes. I think we were sort of on the slightly higher end of that range to generate worst-case scenario. I remember conversations we had before, because because I mean ITB were very much involved in the some of the planning of these experiments. I remember conversations we had where you were theorizing about having gas burners, and I think the particular decision around cribs over gas burners that was that we wanted the fuel load to be able to interact with the shelter as it's burning. That's what you can do. Yeah. So it wasn't just a constant controlled heat release rate from the cribs, but that the feedback between the fuel load and the the shelter was significant. We could potentially have maybe gone a bit further down the route of more realistic fuel loads, but at the end of the day, cribs are just more repeatable in a sense than putting you know whatever realistic looking furniture. And there was, I mean, there was a conversation within Kindling about making experiments relatable to the people that we want them to affect, because people that live in these environments they won't they won't necessarily look at an experiment and see something that looks like their home. So if you fill it with you know a sofa and a bed and some furniture instead of cribs, then it's more relatable to the average human that isn't a fire scientist. Whereas, you know, for for us and maybe for listeners, it's kind of intuitive that you look at an experiment and there's a wood crib there, you're like, yeah, that makes sense to me. That's making sense. So there was there was everything discussed on the spectrum from like concentrate gas burners to wood cribs to maybe we actually do put real fuels in, but I think cribs was the sort of natural selling point for us.

What Non-Combustible Shelters Reveal

Wojciech Wegrzynski 28:26

In the end, you already have 20 different you know experiments to run. And if you add variability of fuel into the mix, that makes uh the design of experiments very challenging. I asked this follow-up question, you know, because uh not that many people do large-scale fire experiments, and but a lot of fire, awfully lot of fire engineers, every fire engineer is dependent on the results of those experiments because that's what what we get to design stuff later on. So I really love uh you know to pull uh fire researchers on their logic behind those seemingly like basic choices for the experimental design, but uh they have they sometimes have a very long-lasting ripple effect in the in the community where they are later used. So it's very interesting to to understand where where did those kick came from. Um let's perhaps discuss some uh findings. I I wonder if I I think we've covered the measurements, so you said a lot of thin skin colorometers plus some diagnostics around the along the openings. I know you had a lot of cameras because you've said like a terabyte of videos, yeah, which I appreciate. I'm not sure you do appreciate it, but uh no, I I am I am but but there there was a video recording system so we could also figure out some stuff regarding the flame lengths and and and flame exposures. I know from those videos that those cases were very different, so let's jump into the data. So, uh, what did you actually find? Maybe let's start with the simplest one, the non-combustible ones, and perhaps let's relate them against what was already known about those types and and then build up on the flammability.

Sam Stevens 29:58

Yeah, so uh and the non-combustible ones are a very nice base case because we had the data from Iris. The first shelter we burned is uh a sheet metal shelter, and then our our next two were sort of mud walled, so we had this sort of wattle and daub style construction where we have a you know wattle wood frame, but then big thick mud layer plastered over it, and then these sort of cement blocks as well as our non-combustible walls, in every case, a sheet metal roof. And the I guess the nice and easy finding from these is they behave as you would expect a compartment fire to behave. So you have a bit of growth in the cribs, and then you get flash over, fully involved compartment fire, and your dominant fire spread hazard is flames from the openings. The slight caveat to that is with these corrugated sheet metals, the corrugation you've obviously got. I think in the past we've called them sort of flutes, where it's it's not a perfectly sealed compartment. There is a little bit of flame leakage, especially with the sheet metal walls, as they're sort of heating, they can warp a bit, and you can get gaps elsewhere where there is some flame leakage. So if we're theorizing about a real settlement and when you have shelters very, very close together, it is possible that some of that flame leakage might impact upon neighboring shelters. We were measuring heat fluxes at one meter away as a as sort of the minimum distance that we were measuring, and we didn't really pick up the effects of flame leakages at that distance. But we did have a we were using perfectly brand new, nice, you know, good quality corrugated metal. I appreciate in real settlements, these sheets get weathered over time, or they'll reuse old ones, and the the quality of construction might be uh less than ideal, so you might get a lot more of this flame leakage. But that aside, we're talking fairly conventional compartment fire dynamics.

Wojciech Wegrzynski 31:53

But you still pick up quite significant fluxes from the door and window plumes, right?

Sam Stevens 31:57

Uh the opening, yes. And this is also, you mentioned the the cameras and the video we took. We're also looking at flame extension from shelters. So across what distance are we projecting flames, um, that we might get flame impingement from one shelter to the next. And we're also picking up heat fluxes within the flame if that the flame is impinging on our instrumentation, which it was in a number of cases. But generally it's about characterizing yes, what is that kind of field of heat flux around the openings.

Wojciech Wegrzynski 32:28

As a comment, perhaps we didn't mention that, but those uh flux gouges were not just like lying on the ground, they were also like elevated.

Sam Stevens 32:36

So we had them uh two meters above the ground level at the floor level of the shelter and 2.4 meters. So that was equivalent to the the height of the top of the openings and the height of the roof, and we're measuring at those heights at one, two, and three meters away from the shelter.

How Light Wind Changes Flame Paths

Wojciech Wegrzynski 32:55

Uh okay, so if they behave like a normal far compartment would, and you have this uh complexity of window and the door at the same time, was there anyone any experiment in which you would have a wind-influenced flow? Like it would turn into like one-directional flow or something?

Sam Stevens 33:12

Yep, that's a great question. And I mean, we aimed to test in as low wind conditions as possible, but you know, large outdoor testing, it's it's not unavoidable. And actually, some of our more interesting findings is that it really, really doesn't take much wind at all. We're talking sort of sub one meter per second to be able to notice the influence of wind, particularly the case when you start adding combustible materials into the mix. For our sheet metal shelter, certainly there was more pronounced flame from the door than the window, just the direction of wind that day. Well, it wasn't particularly high. I think it was about 1.5 meters per second on average, which we didn't regard high. That's not much at all. And you know, it was enough to kind of kill the flames on the window side, but then push the flames to kind of two or three meters from the door on the door side. The other two were at lower wind speed and were more balanced, but you know, even in the course of a what 10-minute experiment or 10-minute fully developed phase, we've got slightly blustery wind outside. We'll have you know moments where it's more pronounced at the window, then more pronounced at the door. And so if you look into the the heat flux data, you can kind of see that where you have periods of slightly elevated heat flux. So, um, yes, wind is a factor, quite an important factor. And we did do a couple of experiments with in higher wind speeds as well, one of those being a repeat of our sheet metal shelter. We basically had uh a few days of uh bad weather during the experiments, and there were days where we were like, we have to do something, and there was days where we had really high winds to the point we couldn't set our instrumentation out safely. Okay, like it was just falling over, and it was you know, it was all kinds of carnage on site. But um, we're like, well, we'll just get some wind data, even if it's just visual. So we settled the we set up the sheet metal shelter again in what were we at? I think we were sort of five meters per second on average. So when I was doing going back over all the over the or all the data, I was trying to convert my wind speeds to what it what is it on the Beaufort scale. Okay. And it's still something like, oh, it's a it's a light breeze. Yeah, when you're there, it really felt like you know, you're properly nice gusty winds, but it still wasn't significant. We were sort of five meters per second on average. I think it we had gusts up to 12 meters per second. And when the days we had stronger winds, it was also very heavily unidirectional. So we would I think when we did the sheet metal, we had just this sort of jet of flame out of the windows, probably three to four meters in length.

Wojciech Wegrzynski 35:56

So the practicality of this those findings for non-combustible one is is that the location of those openings would highly matter.

Sam Stevens 36:04

Yep. Super, super important if you've got non-combustible materials. If you've got, you know, as we'll come on to, if you've got combustible materials, you can't necessarily trust that your highest hazard location is going to be your near your openings. But you know, that's an immediate, immediate, easy finding for us, is that yes, we can show you the data that says opening placement is extremely important and is something that is not considered in any sort of humanitarian guidance yet. For reference, for those non-combustible ones, how how long did it take the the experiment? After ignition, we were usually about three to four minutes to flash over, and then probably 10 to 15 minutes in fully developed, inevitably things would start collapsing, roofs would fall in, the the mud shelter going down was interesting. We had mud walls pancaking in all kinds of directions, which was was fun to clean up. I can imagine, but but yeah, I guess there's a there's a question there of does collapse affect fire spread hazard? And from these experiments, I would say no, not particularly, is the the highest hazard conditions that are most likely to affect spread are you know immediately post-flashover. And you know, if your fire is gonna spread, it's gonna spread significantly sooner than it would usually take for one of these shelters to collapse. They were you know fairly robust for 10, 10, 15 minutes, as I say.

Wojciech Wegrzynski 37:35

Let's move to to some more complex. So I uh you said you had non-combustible walls and combustible roof, you had combustible walls, non-combustible roofs. How how these combinations of of partial combustibility look like and what changed?

Sam Stevens 37:50

So I'll start with combustible walls. The significant variable, which is fairly intuitive, really, is the thickness of whatever the combustible material is. So we did all with sheet metal roofs, we did timber, split bamboo, and bamboo mat walls. Um, and the fire develop into the early stages look very much like a compartment fire transitioning through flashover, except as you're going through flashover, all your walls will ignite and burn externally. But the key difference is the duration for which they remain burning or remain sort of structurally sound. So I think that the timber walls lasted the longest. It wasn't particularly thick. We had like 12 mil thick planks, so I think you know, even it's likely that thicker planks are used in reality as well. But they lasted probably like four to five minutes, where we have this our shelters burning as I would say as a post-flash over compartment fire, with the additional impact of the external walls all being a light and burning away as well. So the openings are still important in those cases. We find that the heat fluxes were still significantly higher at the openings because you have a lot of the fuel gas which is you know being released internally, still venting out and burning as it's mixing with the oxygen at the door and window, but with the addition of all the external walls also burning.

Wojciech Wegrzynski 39:21

And and the light wood materials like the bamboo mats, I would assume they would be gone fairly quickly.

Sam Stevens 39:26

Yeah, and so that's that's the important thing is the bamboo mat was something like 20 to 30 seconds. Seconds. Yeah, yeah, it was gone. Like ignited very, very easily, uh burned away very easily. And the the the kind of you end at the same place with all these experiments was quite a nice thing. You end with your this sort of freestanding sheet metal roof over a couple of wood crypts that are burning because the walls are are gone. And it was just the the rate at which those materials burned away was sort of the decisive factor in the hazard of the shelter. Now, this becomes a more interesting question when we start to think about modeling the ignition of a hypothetical neighboring shelter because the thickness of your burning material or your your sheltered material not only influences how long it burns, but if it was on an exposed neighboring shelter, how quickly that material can ignite. And so at the same time we were doing these shelter scale experiments, all the materials that we were using, we had there was sort of a commercial uh fire lab in Cape Town that was doing cone calorimetry on all our materials for us so we could get some ignition data. Now, if I look at something like uh the timber, if I pair my experimental like heat flux exposures that we got from all our RTSEs with the sort of ignition data and try and model the ignition time of the timber at those exposures, you end up with you know, at varying distance, it's fairly fairly rapid fire spread. But say across the region from one to three meters away from the shelter, I have like a steadily decreasing predicted ignition time. But you compare that to, I think, so like the bamboo mat is a very good example of you have this very short, sharp hazard of the shelter burning. So it's maybe 20 or 30 seconds long, but that's all that it takes for a neighboring bamboo mat shelter to ignite, but only if it's within like a meter, a meter and a half. So for two different materialities of shelter, if you if we're looking at separation distance as a as sort of an isolated problem, is that for timber, say, we have this nice gradient of as you increase separation distance, you are steadily increasing ignition time to a point where the separation distance is sufficient that no fire spread can happen. But that distance is like three, maybe more meters. But with bamboo mat, you have this very sort of binary problem of either it's within this sort of one meter perimeter and it's gonna ignite very, very all its neighbors super quickly, or it's gonna be just outside that zone and it's not gonna ignite at all. And so it's not just that materiality changes the required separation distance, it's that materiality changes the whole context of the way you have to think about separation distance. So is it a binary yes, no, fire can spread or fire can't spread, or is it a sort of a whole spectrum of risk that you have to be thinking about across a large range of separation distances?

Wojciech Wegrzynski 42:30

Yeah, well, this is a brilliant uh topic for a follow-up, I guess, to see how what would happen if you actually had a row of those, you know. Like I could imagine like Project Iris 20 settlement thing bad with different types of those. Well, that probably would we would most likely prefer to do it with uh with CFD, not uh with a full-scale experiment that would be awfully expensive. But yeah, this is a very interesting, like almost like what was better to to have like a longer steady fire but less ignitable material, or a short-lived one, but very prone to any source of ignition.

Sam Stevens 43:08

And that's a I mean, that's a great point to raise because I was just about to go on to talking about combustible roofs but non-combustible walls. Okay. And it's another it's another perfect example of one of these trade-offs. So anytime we had a combustible roof, even if it was thatch, which burned like absolute crazy, we could completely eliminated external flames pretty much every time. Because very early on, you're creating a pathway for all your hot gases to vent upwards rather than outwards. Oh, so no more window plume, no more door bloom. Yep. Everything becomes a very sort of vertical wind wind knot sort of included in this analysis. But you get this lovely vertical plume, your roof catches fire, nice established burning on your roof, and you get this big tall plume above the shelter. But of course, this is a very lateral fire spread problem. We're thinking about shelters next to each other spreading fire to one another. Not a shelter spreading fire up somewhere, right? So we go from having these very intensely concentrated hazards at the openings that are spitting fire like right in the direction of where our neighboring shelter could be, to all our heat is actually being released above the shelter, but then radiating back to the shelters below it. Now, which is a more desirable or less so that's bad language, but which which which do you prefer in a settlement context? Do you want roofs that are venting flames upwards, or do you want roofs that are non-combustible and make sure that your openings are spitting flames sideways? And again, the only way you can really evaluate an answer to that question is if you know what hypothetical material you're igniting. And you can add the fact that to have to prevent your flames of venting out through the openings, you need a combustible material on your roof, which might be otherwise replacing a non-combustible material. You know, you've got a whole other layer of, well, then that combustible material could become an ignition pathway for that shelter. So there's trade-offs like this everywhere. There's trade-offs of do you want a material that burns fast or slow? Do you want a roof that burns through and vents everything upwards? And because the data for those combustible roof experiments showed us that exactly that, that you get lower on average, you're getting lower heat fluxes. So lower peak heat fluxes, but you're getting them everywhere around the shelter. Okay, versus the doors where you're getting much higher peak heat fluxes, but you're getting them in very specific locations.

Wojciech Wegrzynski 45:32

I mean, it is very challenging to also make some like final conclusion out of this data set, because obviously, if you would have strong wind and open the roof, then you have no idea how bad it would be. Yeah, potentially it could be very bad. Yeah. And two, firebrand production and how firebrands spread. Because I would also imagine that if you have like just a vertical plume emerging from a house, I've created a lot of firebrands in my life by accident in fire experiments. I know every little piece of foam, a fabric in your compartment, a little uh splinters of timber that's gonna separate from anything. There's a lot of things that can be captured by the plume and carried out of the building and they become a firebrand. Not necessarily just your no timber firebrands that we're used to in multifires. So so basically, every compartment is a generator of firebrands. And I think that this hazard could be amplified if it's just you know vertical, because it's easier to carry stuff out, whether rather when you have you know plumes projecting to some extent horizontally from your opening. It's a hypothesis, it's not that it's not that I know that, but I would hypothesize that this could be a potential factor, especially if you consider it in the as a part of a dense neighborhood where you know that those things can land, right?

Sam Stevens 46:52

Yeah, and that's really that kind of takes us to the uh limitation of of the work we've done so far. And I like one of the questions I'm really interested in is that we burn all these individual shelters, but what does a fire really look like when it's multiple? And you've you've you've referenced uh Iris's 20 shelter experiment. I think it's maybe with the closest we've got, but what does what's what's the difference between some shelters on fire and a conflagration where the the behavior of the fire is independent of the individual behavior of any single shelter, and you just have a mass of fuel burning because the thing's so big. Um, and I think firebrands might be an important part of that question. Certainly, you see that I think with wildfire where you get firebrand deposition uh or the the combination of firebrand deposition and radiation from the firefront sort of combining to progress that firefront. It's a it's a tricky one. In it there's there's very few sort of known instances of like spot fires occurring in these kind of settlements. I'm not saying that's because they they don't happen, I think they do, but it's very specific to which materials are in involved. Okay, and certainly we weren't we weren't doing anything to measure firebrand production in our experiments, but you could see which like for instance the thatch and the bamboo mat, you know, produce huge numbers of firebrands. I can't be more quantitative than that, but like visually you could see it.

When Shelters Burn Completely

Wojciech Wegrzynski 48:15

Yeah, but also your choice of using the crib as your fuel source. Like, I would be convinced that the firebrands are not just products of you know your construction materials, but literally anything in your room could potentially yield firebrands, you know, paper, clothes, any any type of foam material, etc. But uh anyway, I'm I'm taking you away from from the important things that we've we've observed in this project. How about the the the fully combustible structures, the the the ones you've mentioned touch on thatch?

Sam Stevens 48:48

Again, very interesting. I think it's the best example of where I talked earlier about the idea of categorizing shelters to make it simple for everyone, is where categorization really falls apart, is because this is where the the most diverse behavior sort of occurred. So we had three in this category that were bamboo mat with a thatch roof, bamboo mat with a split bamboo roof, and thatch walls with a thatch roof. So with both the bamboo mat walled ones, obviously, as I've mentioned before, the bamboo mat ignited very quickly, burned away very quickly. But but then you're you're left with this freestanding roof that's burning. Um, how long that lasts, I guess, in reality is going to depend on how strong the structural frame is. For ours, it was the sort of same timber frame for everything. So they all lasted about the same amount of time. The difference being the fire established very readily on the thatched roof, it continued to burn quite easily, even though it's probably a good two meters above the top of the cribs. You know, once it's ignited, it burns very easily in its own capacity. Not so much the case with the split bamboo roof, where you go through this big spike in the heat, the the heat release rate early on, as the walls are burning, as the roof is burning as part of that. But once those walls are gone, it's a split bamboo roof. It didn't, the fire didn't establish on it, and it was kind of very intermittent. Sometimes it was you know burning a little bit, sometimes it didn't appear to be burning at all. Then we have the thatch, uh the fully thatched shelter, which it was mental. Um it was yeah. As I I described the sort of vertical plume that you get with a combustible roof where everything's just going upwards. Uh, in terms of flame heights, we were looking, you know, that not that we've accurately measured, but maybe like five to six meters above the shelter. I think it went beyond the camera that you send me. Yeah, we didn't capture it in the cameras because we like we weren't prepared for such uh tall flames. And then in terms of I don't want to say I don't want to call it heat release rate, I'll call it mass loss rate and because that's what what we measured. We're looking at uh four times four times larger than the the compartment fires and then about two times larger than any of the other fully combustible fires. Okay. And not only was it very high hazard, so high burning rate, it lasted. Like the the thatch takes a while to burn through. It was about a centimeter, 10 centimeter thick layer of thatch. So we're talking, I think we're talking about like a four-minute period where we were picking up heat fluxes at two meters away, sort of in excess of 60 kilowatts per meter square. Okay, well. So closer we're talking, you know, we'll be over 100 and purely from radiation. This was not again, I'm talking about a vertical flame plume. This is not a lateral flame, no impingement on any of our devices. This is pure radiation. This is where I think we it was again. If we could we would have sort of thought about it more preemptively, we should have measured heat fluxes at distances further away than three meters. And if we do a sort of cautious extrapolation of our heat flux data to I think we can predict ignition from just the radius of heat fluxes at like five meters away from the shelter. Plus, all the potential things that we've already discussed. Yeah, plus fire brands. Potential for firebrands. Plus, it's gonna be worse in winds. So, I mean, don't build a house made entirely of thatch is one easy finding. But the the sad reality is like we selected that as a shelter because it came up a number of times in the database. We can go and look at uh reports out there that have these, it's not necessarily gonna be the exact same style of thatch that we used, but any sort of reeds, leaves, any sort of bundled material, it's quite common in in many parts of the world to use that as your primary building material.

Wojciech Wegrzynski 52:37

So so if we okay, we went through the the test through the materials, if we now flip it back to the the simple rules like uh non-combustible materials to meter separation, where do those land in the findings of your experiments?

Sam Stevens 52:52

Well, to me, the answer is they're not adequate, but that's an easy answer for me to say, and the challenge is really for me to say, well, how would I reframe that in a simple way? And it's one of the things we're working on is is a is a guidance document, say. I guess to convey what the findings of the the experiments are, but in a useful way. And it it it I really struggled with like how do I actually tell this story to people that don't have the the technical background or who don't quite frankly just don't have the time to spend learning about our experiments and reading about what a thin skin calorimeter is and what it measures and all this. So for me, it's about like flipping the idea of guidance on its head a little bit, and instead of saying this is what you should do, it's about saying in the situation that you may find yourself, what is the expected fire outcome? And frame that within a like, well, what's your direction of travel? What could you do? Like, if if you're stuck with the fact that you have to build with thatch because that's the only building material you have, really, how much benefit are you gonna get if you manage to space your buildings even like 20 centimeters, 30 centimeters apart? And so it's I've kind of I kind of ended up with two tables. One of like if you have this material and this separation distance, what's the primary fire spread hazard gonna be? And then if given that primary fire spread hazard, and then you incorporate what's your what's the sort of secondary shelter made of, if it's the same material or if it's a different material, what's the likely fire spread time? Uh, we're also trying to develop this idea visually as well in showing sort of like bands of like predicted ignition time around shelters. But yeah, I mean it's not it's not fully baked yet. I think it's it's still a challenge we're working on because it is that you can't you people don't have time for the complexity, but it is a really complex problem. Um, if the minimum we did was say, hey look, you've you've said in your guidance, use fire resistant materials, we can actually give you a list of what we consider to be, you know, quote unquote fire resistant versus not fire resistant. Um or we give them a sort of a framework of separation distance that's not just it should be two meters with no context, just if it's this distance, then your expected fire spread rate is however many minutes versus you know if it's if it's one meter further away, then you might reduce your fire spread time. Um, because I the the guidance at the moment gives me the feeling that if you know people might follow the rules expecting that protects them fully. Whereas we need to be giving them the context and kind of the spectrum of risk, not necessarily saying do this or do that, but here's the variety of possible outcomes you could have for the variety of possible inputs you have. And it's not it's not easy to do, it's really really, really not easy to do.

Wojciech Wegrzynski 55:54

It also goes both ways, like how how much the structure of your house influences the others, but also how ignitable your building is, and then both those factors will matter when you have this large-scale event, in which case, um, well, the individual fuel packages being your informal shelters perhaps are lesser important rather than the the general you know dynamics of the of the whole landscape that you you have the your fire in. So that's also another like interesting thing. How does those individual choices uh you know translate into let's say global risk for the whole community? Yeah, and and that's definitely another like layer of interplay, which probably is very, very complex and difficult to solve.

Sam Stevens 56:43

I think in addition, the beautiful thing about working with fire is that people like watching it on the whole. I don't mean to sound morbid, but like it's not it's not necessarily hard to demonstrate the difference in hazard between two shelters if we can put that on film. And I that's one of the things we have done is we released a bunch of videos that were kind of aimed, not necessarily a completely non-technical audience, but for people that are interested in the problem and want to build it into their work. We kind of did this series of like, here's what we did in the experiments, here's what instrumentation is and what it measures, and taking through the whole story of look at this shelter burning versus this shelter burning. They're very different, they do very different things. So even if a guidance document isn't there to support someone in every single decision they're making, at least the information's out there in quite a visual and understandable way. Uh, I think that's one additional side to it beyond words on a page. Because I mean that that's what I struggle with, is I'm putting stuff in tables and on a page. I'm like, but this, I don't really have a sense. It doesn't give me a good sense of what a real fire could behave like. Whereas if you just show someone a video of that Thatch one burning, it's like, okay, don't do that. Like, really, don't do that, because that's that's bad for everyone in the world.

Wojciech Wegrzynski 58:02

I mean, it's I I think which framed now is common for fire science in general and trying like being in the business of fire testing for 17 years. I've seen a lot of bad fires which were okay by the means of the standard, and uh because you know the the context is is not really there because uh the perception. I mean a lot of those tools are just market ladder, you know. You want to have your product on a specific place in your market ladder. This product is better than that, our product. Unfortunately, a lot of the fire safety uh comes down to that. In the end, we still get a fairly safe systems uh most time most of the time out of this this market ladder. But I I assume in the in the world of humanitarian and and shelters it's different. Ah, humanitarian. We've missed one thing, uh the tents. You didn't we wouldn't discuss the tents. Yeah, let's probably catch up on the tents.

Sam Stevens 58:54

Okay, it's a lot to like 20 experiments, it's a lot to talk about. The tents. So the tents they come with an additional little side piece of work. Okay. Um in the sector, there's a lot of manufacturers will provide tarpaulins, provide tent products, and then the major players like the UN or the Red Cross or whatever, will kind of have their standardized tent that they'll supply with people. In the documentation, they'll often reference how the the tarpaulin material has been tested, and it's often been fire tested. So most common is the SBI test, they'll perform the SBI test and give the tarpaulin a rating, which is usually quite a good rating. I'll come on to why that might be in a moment. Um, like Euro class B, Euroclass C. Yeah, Euro class B, no smoke, no droplets. And I mean, I'll tell you why they get that because we tested some and we got that classification. But there's a there's a bit of a catch to it. Um, the second is uh a test called CPAI84, which is exclusively used by the textiles industry, particularly for uh tent materials, but in the sense of like commercial camping tents. So the little things you go out and hike in the mountains and pitch your tent. It's uh not it's not for construction, it's not for long-term, you know, it's that it's for like gazebo's camping. I think its origins are actually from like circus tents back in the 60s or 70s or something. But sometimes humanitarian sector uh organizations will have that test performed on their um on their products, and you know, overwhelmingly, if it's it's a product that's being used, it will have passed this test. Now I'll come on to it in a moment. But so with SBI, there's a couple of things. In the literature, it won't say whether that product was tested in a substrate-backed or airbacked condition. But the the sort of the wording of the SBI test is fairly clear, and you should test the product in a manner that best matches its end use. So really they should they should all be being tested airbacked because you know you're not gonna have a tarpaulin pushed up against the wall. It's a kind of doesn't make sense, right? So we don't know how they're actually being tested in reality. Um, the second thing is it's just the nature of of the materials. So we had two tarpaulins, we had one UN tarpaulin with that we know for sure had fire retardant in it, and we had we went to like a local supplier and just got some off-the-shelf tarpaulin, which I think because they performed extremely similarly, I think it was virtually the same thing. And so it's a polyethylene material with fire retardants in. If you expose them to heat, they are hyper-mobile. I'll say that. I don't know if there's a specific term for it, but if you expose these things to you know, not even that particularly high level of heating, they will warp, they will shrivel, they'll kind of tear if there's enough sort of tension in them. Um, so they will move away from whatever the heat source is. In the shelter experiments, we saw this that you know, our gas temperatures at the roof were I think getting to about 200 degrees. So our cribs are barely going at this point. They're still sort of starting to establish, but a bit of hot air is collecting at the top, and the roofs are just ripping apart. Okay. And then the walls are tearing. And so by the time the cribs are even like near like fully going, you don't have any walls left. And they've not burned, they're not on fire, they've just driveled and shrunken and given way, and maybe bits of the roof drop onto the crib cribs, and so maybe they're burning and melting, but it's kind of hard to tell. So now in the SBI test, you see exactly the same thing where you turn on your you flick on your burner, and immediately in the you know, in that sort of corner join, if for people that are familiar with the SBI test, where you've got your your long long panel and your short panel, the material just tears apart at that point. And then you've got sort of two loose-hanging bits of tarpaulin material away from the heat source. So they're not in contact with the flames from the burner, they're just kind of sitting hanging there. And but by the letter of the law of the test, they're not they're not producing smoke, so they don't they don't score highly in the smoke category. They're not producing any droplets because they're not burning, so they score highly in the droplets category. And the fire, you know, smoke smoke graph figure they don't exist because they don't burn. Yeah, right. So the the so you can get these things, like they score quite highly. They look good, right? And maybe, but maybe maybe the the reason is like they actually are good. It's good to have a material that doesn't ignite particularly easily because it moves away from the heat source. I mean, certainly there's videos on online, there's no no we wanted to get some non-fire retardant tarp. It's very hard to do because nobody's just gonna give you that if you go asking for it. We really wanted to sort of see the difference between non-fire retardant and fire retardant and see if there would be any difference. We had one instance of our fire retardant tarp not doing so well in the SBI test, and that was because a tiny little flame lit managed to establish on the sort of leading edge of the tarpaulin as it was sort of tearing away from the heat source, and then slowly over a period of several minutes, that flame lit was enough to you progressively burn away the rest of that panel. So I can't remember what the exact metric is, but there's there shouldn't be flame spread across the panel by the end of the test. But we did lose that panel, so then that particular single test, because of one little flame lit on the edge of the tarp, did not get a good rating. I think it was like D or E or something, I can't quite remember.

Wojciech Wegrzynski 1:04:55

But but but in the in the large-scale experiments, you said they like would not depend on a single flame lamp because you have a massive crib burning next to it.

Sam Stevens 1:05:04

So they most likely all repetitively were gone. So yeah, in both in both the tents we did at full scale, the tarp was like a non-existent factor.

Wojciech Wegrzynski 1:05:13

What does it mean then for fire spread, like in terms of external heat flux and also in terms of ignitability of it?

Sam Stevens 1:05:21

Well, this is kind of where the the shelter test break down a bit because we assumed a a repeatable wood crib fuel load, but that's non-representative of what you have in reality. So if if we now have a shelter material that is basically a non-factor in your fire from a fire spread perspective, then you have to look at what the fuel load is within shelters. Because then that you could apply the logic to the exposed shelter as well, that if it's being exposed to heat, whatever wall that's being exposed is gonna just melt away and warp away, and then it's the fuel load inside the shelter that's the importance. Thing. So it's a tricky question to grapple with. And the the the last thing that kind of makes it even more difficult is that when we tested the tarps with the CPAI test, which is it's virtually the same as there's an ISO small flame test where it's just sort of a foot-long strip held vertically and with a little sort of boonsen flame at the bottom. It's supposed to, when you remove the flame, it's supposed to flame out after like two seconds or something. Every single sample we tested, when we exposed it to that little small flame, the entire sample burned away in like 30 seconds. It was gone. So we have this problem of like if I am at the full shelter scale, it looks like the tarpaulin is not a problem. I have an SBI test that the product technically is doing well in, but I can see with my own two eyes why it's doing well, and that's because it's not really being exposed to heat at all during the test. But either way, I'm giving it a good rating. And but then I if I pick another test method, it failed every single time. And so it looks like a horrible material. So I think the problem, really the problem with the tarpaulins is that there isn't there isn't a regulatory framework or appropriate tests to capture how a tarpaulin might be involved in a shelter fire in reality, and capturing that from both the like how does it burn and what hazard does it pose, and how might it be a vulnerability on an exposed shelter? Like, can it ignite on an exposed shelter? So there's a lot of questions with tarpaulins that like once we started scraping the surface of it, we're like, I just don't think we can we can answer these in in this kind of round of experiments and this well, welcome to the bit of work.

Wojciech Wegrzynski 1:07:43

Welcome to the world of fire science where the complexity is every time you uh solve a problem, you create uh five new ones to study. Um that's I think a common thing, and uh probably one of the reasons we all love uh being fire scientists. Uh I think this was a very huge attempt on quantifying a lot of these problems in terms of fire behavior of those shelters, but also fire spread between the shelters. Even if you build just a single one, I think the data from these experiments will allow for a new generation of modeling approaches that will perhaps answer some interesting questions at a large scale. Therefore, I I find it extremely, extremely valuable and interesting that that this has been done. Um and my huge congratulations to the team with Kin Link. Uh, huge congratulations to FSRI for investing in in this important uh important field of of knowledge that uh is like as potentially one of the biggest fire challenges we have out there. So definitely it it it needs more and more efforts like that. And uh I hope this this will lead to good, useful guidance and uh a lot of new knowledge built on for years.

Sam Stevens 1:08:58

Yeah, and on that note, we will have a big report coming out soon. I'm not sure exact dates, but um, that will contain all of this. And you mentioned about uh modeling approaches, we will, I believe, be releasing the data completely open source once stuff has been you know, once the report's out, um the data is also going to be released for anyone to have a look at or use if they're interested in.

Wojciech Wegrzynski 1:09:23

Fantastic, fantastic. I will be sure to to to uh bring it up here again. And if if eventually we have some results of modeling that are shareable with uh with the general audience and we know a little bit more to get a uh one step further than we are today, I will be sure to report that. On that notice, uh Sam, thank you so much for for coming to the Fire Science Show and sharing all of this and uh all the best, mate.

Sam Stevens 1:09:48

Yeah, thank you for having me. I appreciate it.

Wojciech Wegrzynski 1:09:51

And that's it. So thank you, Sam, for going through this massive experimental effort. Uh, to the listeners' explanation, I know some more about this project because we were quite involved in the early days of this project. We were bidding to do those experiments in our lab. Um, unfortunately, we're not able to get those to Poland, but I'm kind of happy that they went to South Africa. Perhaps that's where uh they belong. And afterwards, uh we I had a chance to to assist Kindling Tim with some visual imaging uh analysis of the footage recorder during the experiments. We are using cameras and computer vision to figure out what the flame extensions are where the flames are in particular experiments and conditions, and try to timeline it with the fire timeline. Uh, not an easy task, but uh quite quite an interesting one. And uh a lot of those things that Sam was describing based on temperatures, hit fluxes, etc., I also were able to see on the videos themselves, which he sent me literally a hard drive with one terabyte of videos. That's not the easiest thing to process. Uh regardless, that has been a lot of new information covered in this podcast episode. The resources from this project are popping and popping. So all the time Kindling is releasing new things related to those uh burns. So please keep an eye on the Kindling webpage. The links are in the show notes to whatever is released. And I hope this will guide new opening for modeling informal settlement fires in the future. And this modeling may be able to answer some really important questions about the behavior of uh whole you know neighborhoods rather than a single dwelling. That that's where I think this should and will be going. Anyway, thank you very much for joining me in this fire science show episode. And the next week you can expect a little more of fire science, as always, on every Wednesday. See you there. Bye.