109 - Forensic Fire Science with Richard Roby

Hello everybody, welcome to the Fire Science Show. Today I'm having a treat for you and that's an episode on investigations and forensic fire science, something I wanted to do for a very long time. I found a very perfect guest for this episode, that is, dr Richard Robbie, the president and director at combustion science and engineering, a renowned combustion scientist and someone with literally five decades of experience in fire engineering investigations and combustion, and also a person very passionate about spreading the knowledge and teaching. So definitely a very good person to have on the podcast. And with Richard, we're touching the ideas of the use of scientific method in forensic fire science, in fire investigations. It's very relevant for everyone. Fire engineers, please listen to this episode because we can learn a lot from investigators and it's a part of fire science that we also need to learn to appreciate and use in our design. But anyway, enough of me talking. This episode is really good and you won't listen to it, so let's spin the intro and jump into the episode. Welcome to the Fire Size Show. My name is Vojci Wigzynski and I will be your host, and before we jump into the episode, please give me a few seconds to acknowledge the role of my sponsor of this episode and the whole of the podcast in this year. Orphar Consultants, without whom I would not be able to publish this podcast every week for free for all of you to listen. So thank you very much, orphar. Orphar Consultants are a multi-award winning independent consultancy dedicated into addressing fire safety challenges. Orphar is the UK's leading fire risk consultancy. Its globally established team has developed reputation for eminent fire engineering expertise, with colleagues working across the world to help protect people, property and environment. In 2023, orphar it's growing its team and it's always keen to hear from industry professionals who would like to collaborate on fire safety features this year. Get in touch at OrpharConsultantscom. And now back to the episode on fire investigations. Hello everybody, welcome to the Fire Science Show. I'm here today with Dr Richard Robby from Combustion Science and Engineering. Hello Richard, how are you? I'm great. Thank you, i'm about to have a fantastic interview. How?

about you Great, and I thank you for inviting me to your show.

I'm really excited for this interview. I was reading through your scientific bio and I've learned that you have received four Biggestone awards. That is crazy. I have one. I'm super proud of it, but to meet someone who has four, i think we're up to six now. So you're up to six. I was like, oh, that is crazy. Fantastic, which means you are fantastic science communicators, and this is exactly what I need for this podcast. And the subject for today would be the use of scientific method in fire investigations, forensic fire science and how we can actually solve fires with the use of science. So perhaps let's start by defining the scientific method, because this may not be obvious. So how about we start with that?

Sure, so the scientific method actually takes its roots from more than 500 years ago, in the Enlightenment, and the Enlightenment was based on a simple premise that was revolutionary at the time, but we more or less accept today sometimes less but more And that was that nature is governed by certain observable, definable laws that can ultimately be determined through the application of the scientific method, and that the analogy is that you collect data First, you decide what do you want to understand? For Newton it was. You know why does the apple fall from the tree? and then and fall down. So how can I understand that The first thing you do is you collect data And then, based on the data and this is very important based on the data, you formulate one or more hypotheses. Then you use the hypotheses to challenge the laws that we already know of science or of math And you find a conflict between them. Then you have to revise your hypothesis, or you may have multiple hypotheses and only one of those hypotheses actually fits with all the facts and all the evidence. A simple example of that scientific method I like to give is Christopher Columbus. Christopher Columbus used to go down to the docks as a kid And the data that he observed was that as the ships returned from the sea, he could always see the crow's nest and the top of the mass before he could see the bottom of the ship. Now, having been a student mathematical geometry, he basically took that data and formulated a hypothesis that the only way that could be true is if the earth was curved. And at that time, of course, people thought the earth was flat and they would sail off the end of the earth and fall off. And so I like to say he tested that hypothesis to go into the Queen Isabella and say, hey, if you'll find me for a ship, i'll prove to you that the earth is round and I'll sail around it. And that's how he tested his hypothesis and he didn't fall off the edge of the earth. So that's a very simple application of the scientific method.

That's also an awesome example of how, by trying one thing, you can find something else, because he didn't really seem to confront the earth, but he found a nice continent, so that's not a bad outcome either. But yeah, he did not fail.

Yeah, actually I went to Magellan to actually be the first one to circumnavigate the earth.

So in terms of forensic fire science I've never done forensic fire science actually, and I'm kind of fascinated how clues and scars after fire can help you navigate what happened. So first you said you have to define the problem, or define the thing that you are looking for. with the scientific method, when you attempt an investigation, what are you looking for Like? what's your end goal at the beginning, before you even form your hypothesis?

So typical goals in an investigation are to determine the origin, to determine the cause and to determine the responsibility. Now, there can be sometimes, in specific cases, a little broader than that, but those are usually the three main things we're trying to do. And the origin is where exactly in this universe of charred remains. Did the fire actually start? The cause? we literally want to understand what brought the first ignited substance, together with what we would call competent ignition source, to actually start a fire that was in some way unwanted. The responsibility goes in the legal realm. It goes to who may be responsible for pain, for the damage, or was there a crime involved? but there's a really important aspect, the responsibility that sometimes in our litigious society gets lost, and that is future fire safety. By understanding what caused the fire, where it occurred and ultimately what the responsibility for that is, we can change future fire safety. And an example I give is you have a hotel lobby with nice, beautiful couches that are overstuffed and everything and somebody smoking in one of the couches, and then it inadvertently drops a cigarette into the couch and leaves, and in the middle of the night that transitions to flaming and you get this roaring fire in the lobby of the hotel. Now there are multiple outcomes we can have based on the situation. So origin I go in and I ultimately determine the origin was between a cushion and the edge of the couch, cause I can ultimately determine it was somebody inadvertently dropped a lit cigarette And that's what started the fire. But responsibility I can have two outcomes. One is there's a mass of fire in the hotel. It spreads up through the hotel, kills a lot of people and that sort of thing because there was no sprinkler system. Another outcome is that lobbies fully sprinkled. As the fire starts to rage, the sprinklers come on, they douse the fire, there's a wet mess, but everybody goes home safe. So the ultimate responsibility for that fire has an enormous impact on public policy, because you might now want to go after the first fire where there was no sprinkler and say we're not only requiring sprinklers in all new hotels, but maybe this was so bad that we need to go and require them retroactive. So an important aspect of forensic fire determination besides who's guilty of something, either a tort or a crime is where the codes adequate. You know, was the public policy adequate, were the situations adequate? And do we use that to inform our code making process so that we can make a safer world from a fire safety point of view going forward.

Are those investigations always so ignition oriented Like? for me as a fire engineer who designs buildings, I don't really care that much about the ignition source. I just assume a fire has happened in my building that I'm designing And so for me it's irrelevant what caused the ignition. And if I look at a building which has sustained like severe damage, it's hard for me to put the blame on the fact that the fire has happened because there was an ignition source. For me, perhaps is wrong engineering of the building. But when I look at the forensic fire science, always I had the electrical socket was the source of ignition, or someone set it on fire, or it was negligence by even you know, looking at, for example, Grenfell inquiry with this horrible fire that happened in UK, So many people have focused on the faulty fridge or whatever was the appliance that started the fire. But it's hard for me to blame Grenfell on the appliance manufacturer And I don't think that that was the final outcome of the inquiry either. So how do you do that?

You raise a very important question. That again goes back to what is the ultimate goal of your inquiry, and one of the ways we can talk about that is it may be to identify failures in the fire shape design of the building, and that could be based on failure of somebody to bring existing knowledge there in the design and building of the building. But in some cases it's like, okay, something happened, we didn't anticipate before and we need to change it. And one of the ones I think about is the King's Cross subway fire in London many years ago, where we didn't understand how fires could spread up a inclined trench And so we weren't worried about the fact that we had these wooden moving stairs and that they were combined and that they were angled, because we simply didn't understand the fire science of that. So in doing that investigation we ultimately did, and now we force people to design those systems differently, and that's one of the in my opinion, one of the greatest long lasting outcomes of fire investigation is not just somebody has somebody else's insurance company, pays instead of my insurance company or somebody goes to jail That process. Fire designers, fire safety designers can design better or whatever the ignition sources. But ignition sources matter too. And if you go back to my hotel lobby case, it might have been good enough in that case to simply have smoke alarms in the lobby, right? Because if it starts as a smoldering fire, then you get alerted to the fire when there's still time for the fire department or host crew to come in and stop it from spreading throughout the building. You don't necessarily have to have break core systems, which can do a lot more damage, especially if they inadvertently go. So in those cases the specific ignition source does matter And also the first material. That matters because it goes to the issue, right. We always talk about heat release rate in fire. Engineering is ultimately about the rate at which things happen, and so if you know what the ignition source is and you know what the first fuel is, then you get the heat release rate. And that can be very important because, as a designer, you design based on certain assumptions about the fire growth rate, the fire location, what kinds of other fuels it can it and that sort of thing, and so being able to understand the specific origin and the specific ignition source does become important in a different way in the fire safety design.

My God. Now I would love to make an episode about liability of the design fire choice.

And that's exactly an issue. So when we do performance-based modeling, right, somebody's got to pick the design fire. Yeah, and pick that piece. We usually, in my case, and now I'm scared. And so the question is how representative is your design fire of the actual fire that could occur And we go back to these issues of origin If that sofa is in the middle of the lobby as opposed to up against a wall where there are big drapes and everything, and that it can rapidly spread? we have two different fire scenarios, although the same basic fire scenario is the same Cigarette inadvertently dropped into counts smolders for a while and then transitions to flaming Matters, what the surrounding materials are and the size of the fire and whether you can radiantly spread that fire to adjacent materials, based on the location of the initial fire.

OK, so I'll leave that episode idea for the future, but we'll do it one day. But let's go back to forensic fire science, so applying scientific methods into fire investigations. I am not completely sure if everyone in the world of fire science is familiar with really particular path of the scientific method, so maybe let's try to do a step by step. How does one apply scientific method in a way that they can claim I have applied science to solve this properly? Great, question.

So we talk in forensic fire science, we talk about data and evidence. Ok, what's the difference? Yeah, the difference is very important. So my fire happens and it happens late at night and I determined that that night there was a full moon. That is data, it's object data. I can determine it and it's reliable. We've known the phases of the moon for centuries now. But is it relevant to the fire? So we take data and we analyze data to say one, is it reliable? And two, is it relevant? Because only data that is relevant and reliable now becomes evidence with which to formulate a hypothesis. Ok, So the phase of the moon doesn't tell you anything about the origin or cause of the fire.

So once the data is confirmed to be reliable and relevant, it can become an evidence in your investigation Right.

And then, when you've collected sufficient evidence, you now start formulating hypotheses.

What are?

hypotheses. They're what some people call theories, scenarios, whatever term you want to use for how the fire occurred. Again, maybe the first thing you're trying to identify is the origin. So you gather a lot of data, and that data may be burn marks, it may be materials that are burned. The distance, how far was a material that was burned from a material that didn't burn? That tells you something about the size of the fire. Was only one side of the adjacent material burned? That tells you something about the direction the fire was spreading. So you gather this data and you use the data to follow back to and say OK, in my opinion, based on reliable evidence, the fire started in the left corner of this conference room And even though ultimately it spread to the whole conference room, by following all this evidence I can put it back in corner. Well, my first hypothesis may have actually been that while smoke and hot gases got out of the conference room, all the burn damages in the conference room. So my first origin hypothesis might be the origin was in the conference room. So I've got sufficient reliable evidence to narrow down from the building. Some people say I start with the universe, i move to the solar system, then to the earth, then to the earth And then it's easy. But your origin, your goal is to keep shrinking the origin as much as you possibly can store reliable evidence. So I get it now to the conference room And hopefully I can get it to the corner of the conference room, because once I can do that now I can start doing a cause analysis. Because I know that if in fact that is my area of origin, it has to have two things It has to have a reliable ignition source And it has to have a fuel that can be ignited to be the first fuel ignited by that ignition source. So I now have to challenge my origin hypothesis And this is where the scientific method becomes an ignorant process. I now go in and I say, oh, the only material that was in that corner was a metal lounge chair that had metal slats and wasn't capable of burning. So I have to take that evidence, once I've confirmed it, and say, yes, in fact it was made entirely of not combustible material. It didn't even have plastic armrests I might have first thought there were And say, ok, now I've got to reformulate my origin hypothesis. I'm still in the room, but that particular evidence is not consistent with the area of origin that I have hypothesized. And so does that mean I can't find an area of origin? No, that's why it's an iterative process. So now I start looking at other areas nearby, because I got there by saying I think a lot of the burn pattern evidence and maybe eyewitness testimony directed me there. And what I ultimately find is, say, the poster behind me that somebody quickly looked in the door and saw what was a reflection of the fire And what they thought they were seeing was the fire. And so where my eyewitness testimony originally took me, to one corner, now I find out, oh, they may have been seeing a reflection. That's new data. Can I reliably determine that that could have reflected the light of the fire? And if I do, then I say, ah, now I have a new hypothesis that it was actually the opposite corner.

I was about to ask about the testimony of eyewitness or firefighters on the scene. First of all, to what extent do you consider this as a reliable source of data And how much trust you can put in that, and to what extent does this guide your investigations?

Well, my own opinion and my experience is, most eyewitnesses are not lying. Ok, yeah, people say are you saying that eyewitness was lying? I'm saying no, he or she was mistaken. Because most people, as I like to say, have never in their life experienced what I call a fire in anger. Right, they've seen a fire in a fireplace or a campfire or a fire room stove or something, but you and I have seen a fire in anger, an uncontrolled fire, and that's an entirely different circumstance. And we find that even firefighters sometimes don't fully understand what they're seeing And so what the scientific method obligates. I always say, if I have to choose between a law of physics and an eyewitness, i go with the law of physics every time, because what makes it a law is it, to date that is not yet improved to be false, whereas we know that eyewitnesses have been proved to be wrong. So part of the process is and 921 talks about this is you have to take eyewitness testimony and compare it with objectively verifiable scientific evidence and see if they're consistent. And if they aren't consistent, then you have to discount the eyewitness testimony. So again, like in the case I gave you the eyewitness said that it was in that corner And I went in and said no, there's nothing combustible in that corner. So, although that may be what they thought they saw, it can't be what they saw. So can I explain in another way? And all of a sudden I realized, oh, there was a poster board there that early in the fire, before it got burned, would have acted like a mirror. And now I can understand what they saw. They didn't understand what they saw. They were being honest, but they were just wrong. And now I can use the laws of physics, understanding how lights reflect. And I go to a different corner And now I find that there's material there that's readily ignitable. I find an ignition source, i find an outlet that shows that has undergone runaway thermal heating, and now I have a new hypothesis that the fire started in the opposite corner, and I can now say that that's consistent with all the available data, including the eyewitness testimony. Once I understand that they were seeing a reflection, You've mentioned 9 to 1.

So to the listeners, you're most likely referring to an FBA 9 to 1, fire and explosion investigations. That covers much of it And actually the use of scientific method is a part of this standard. I have it in front of my eyes And it looks very impressive the standards to the whole committee. Congratulations on putting together such a well-crafted handbook. That certainly helps investigators.

The consistent with the scientific method. Nfpa 921 is always going through revisions Because we get new information, We get new data, We get new evidence, We get better understandings And we find out that sometimes what we used to believe was wrong. I can give you a very simple example. We used to believe that crazed glass wasn't an indicator that a flammable liquid had been used And it was considered a key indicator of an arson fire. Through scientific testing and analysis and everything, we found that what causes crazed glass is the glass gets real hot and then you hit it with a hose stream And that rapid cooling, just like when you drop an ice cube in a warm drink, is actually what caused the crazed glass And it's not dependent on what the actual fuel that was burning to heat up the glass was Misunderstanding. When I took my first fire investigation course in the late 70s from the New York State Fire Academy, I was taught the crazed glass was an arson indicator. We now know that's not true, So we have to revise 9.21, just like the scientific method causes you to do this iterable process.

I have my experience with NFPA standards And I'm also a part of European standardization And I certainly appreciate the way how NFPA approaches updating the standards. And I've said it here many, many times, i know many people in US don't like it and are disappointed with it. But, guys, your organization is really good. So congratulations to the FPA for keeping their standards true to the science and up with the scientific method. So, richard, you have your data, you have evidence, you have burns, scars that are proven to be useful in your study, that they came from the fire. How does one read that to find the origin? Is looking at the fire seen enough, or it's just the beginning of the process?

It's the beginning of the process. Sometimes you have to go back and do laboratory analysis. One of the ways we test hypotheses is through computer fire modeling, because typically one of the hypotheses ultimately we say, if you want to determine the origin and cause of the fire, one of the things you need to be able to do is explain how the fire spread from the first item ignited. So you do your origin and cause analysis and you're proud of yourself. You identified the first fuel ignited, you identified a component, ignition source, but now can you explain how the fire spread? And that how can be in two ways can be both geometrically held it spread. But as we know, as one of my partners, professors at WPI, famously said, time is the yardstick by which we measure fire. And so the other question is will your origin and cause or the rate at which the fire spread, not just geographically how it spread? And that's one of the ways that fire models can help us, because they can help us without having to go and build and actually burn to test the scenarios, which we have done and still has done from time to time. The models allow us to test that physics and do multiple iterations and say, okay, let's assume that it's this way And that leads to one hypothesis, or this way we run the model and what we find out is one way causes the smoke detector to go off in a minute. The other one causes the smoke detector to go off in five minutes, and we know that somebody was there because they heard the smoke detector about two minutes into the fire. So now the model says okay, i can eliminate the scenario that results in the alarm not going off till five minutes, but I now can still. It doesn't prove the one in one minute, but it's not eliminated And the scientific method is constantly trying to eliminate it. And when you can't eliminate everything, what you're left with. If it's reliable and you have sufficient confidence in it, then that becomes, at least for the time until you get better data, your ultimate conclusion. Now, sometimes we don't get enough data to make that certain. For example, what if my modeling shows that either the one minute or the five minute scenario could be possible under the origin and cause I've determined? I have two competing hypotheses. I haven't been able to distinguish between them And therefore I don't have a reliable ultimate origin and cause, because I have two different scenarios, either of which can be reasonably valid.

So for fire modeling you need reliable input data. So I wonder, how do you find the data in the destroyed scene? I mean modeling compartment fires by placing objects with their physical properties and a modeling pyrolysis or some very complicated interactions between small fire sources is very difficult. Most of us in engineering would rely on design fires and prescribed heat release rates And I guess for testing multiple hypothesis probably you would also like put a 1 megawatt, 5 megawatt, 10 megawatt fire and see which is closer to the reality. How do you cope with that, because I believe this would bring also a lot of uncertainty to your simulations.

Absolutely, and you have to do that again under the sci-fi cook method. You're testing different hypotheses by those scenarios. But sometimes people say, oh, there's so much damage here You can't possibly model this fire. And an example we had is we had building fire where the thing was so destroyed nobody knew for sure whether the ceiling was 8, 9 feet or 10 feet. Okay, okay, so what we can do is go in with a model and model the 8 foot scenario and model the 10 foot scenario initially, and if we find that they lead to virtually indistinguishable outcomes, then we can say that the exact height of the ceiling between 8 and 10 feet is not this positive in determining the outcome of the fire. If we get a very different scenario, when we do 8 feet versus the 10 feet, we say we can't reach a conclusion because we simply don't have enough of that data turned evidence in order to ultimately, and so our cause has to be undetermined.

And the course of the fire, like when did Windows shatter, for example? I would say that's fundamental to the growth of the fire and development.

Yeah, that's one of the things that we look at And if you've looked at my resume, you might know that I was one of the early people that published work in when I was at Virginia Tech, in window breakage and fires and a couple of the papers that we have you made reference to in that way, and we've now been able to incorporate that window breakage into models And so that does become an important piece of evidence if it's reliable in the determination. Have I properly assigned the right size fire, the right fire growth rate, sort of stuff. And we were involved in a fire that was thought to be an arson fire and in fact a man was arrested, or the fire that killed both of his parents, and what became a critical piece of evidence in that case to get the arrest rejected was that a deputy police officer showed up at the scene and ran around to the back to try and rescue one of the parents and actually saw the time at which the window in the room where the fire started in the living room broke out, and we were able to show from our modeling that that window broke out as a result of a polyurethane couch burning, not somebody pouring massive amounts of gasoline into the room, it would have broken out before the deputy could have ever gotten there If in fact, it had been an accelerated fire, the key thing being accelerants accelerate the rate of fire growth. They don't change the temperature. That was one of the misunderstandings people had, that you hear people saying you know gasoline fires burn hotter. No, they burn faster, they don't burn hotter. Virtually all hydrocarbons, whether it's wood, plastics, gasoline, diesel fuel, all have a similar flame temperature. But an accelerant is used because it burns faster and it spreads the fire effect. And so that window breakage, without even modeling, just using research from the literature, we were able to show no, this was not an accelerated fire, or else the deputy couldn't have arrived on the 911 call and been around to see that window actually break.

I often have this problem discussing fire with non-fire professionals. Like temperature it's going to have, Well, that's like 1400 degrees Celsius. That's probably the max you can get, And that's chemistry and you're not. It's not going to differ that much Interesting comment on that.

When we find things melted can't be melted at 1400 degrees, it takes higher temperature. And the first question is what was the actual fuel burning and what was the oxidized? What it suggests is we had something different than normal materials burning in air. So, for example, you know, rocket fuel burns significantly hotter than that, but it carries its own oxidizer with it And you actually have to look at the chemistry And I know that's a sore subject for some people, and one of the things we teach in our classes on fire science is how to calculate what's called the adiabatic flame temperature. We've got a lot of getting in a lot of detail. It's basically the hottest temperature you can get from a particular fuel oxidizer mix, and anybody who's used an oxy-osybilene torch knows that you can't cut steel with a sevillene air, and the sevillene compressed air mixture doesn't do it. When you add the oxygen, you now change the chemistry and now you can get a significantly hotter flame, and so we can. That's another case where we can use that data And look at it. Is it reliable evidence? Do I have things that are melted that couldn't have been melted by ordinary combustibles burning in air? Does that mean I have to look for a different fuel source or a different oxidizer source? Fantastic, we had cases, for example, where somebody had medical oxygen. Right, it was a patient who had medical oxygen And it turned out that the fire in the immediate area where it started was being oxidized not by the air but by the oxygen source, so it was hotter and it was able to melt steel literally liquefy steel, that's brilliant.

And tell me how much you can read from a burn mark, like, how much does it tell you? I find it, as you know, i find this as this fascinating thing, that an expert comes into a place where everyone else just sees a burned room and they can see a story in what's written by the flames on the walls. So what does an artist see in those scars?

Well, hopefully it doesn't become like modern art, where a colleague of mine, whose first degree was in fine art and sculpture, took me to a museum of modern art And I said I guess I just don't. I'm not very artistic because I don't see some of these things. She said, no, what's good, modern art is whatever you like, there is no edge. So we don't do modern art, but what we do is, over time you build up experience And you know that gypsum board calcifies in a certain way and it takes a certain amount of fire exposure before it starts to crumble and collapse. So I go in the room and I see that the gypsum board in one area has has calcified and crumpled and collapsed, but not in another area, even though there's smoke staining everywhere, and I say, ah, that tells me that this gypsum board was exposed to higher fire for a longer time than the gypsum board over here. And that allows me to look at those fire marks and look at different conclusions. We can look at wood members And there's a lot of research that tells you how long it takes, with a certain fire exposure, to chore a two by four or a two by eight, you know, or rafter or something like that. Or how long does it take to burn through plywood? So we can go in and look at those kind of burn scars and where the you know, the person off the street just sees a whole bunch of certain burn and everything, we say, oh no, it's much heavier charred here than it is over here, which means either had to have more fire exposure or fire exposure for a longer time. So that is the ways that we do, but ultimately have to come back to the science and say I've done this analysis. Now I go to literature and I say is this consistent with the literature on burn time for this kind of wood in this kind of circumstance, with this kind of fire?

I love how you brought it, that it can be either a longer fire or a bigger fire, and I guess that distinction probably is sometimes perhaps challenging.

But again, if you go back, i like to use common sense examples for the average person because I said to Teresa a lot go to your fireplace. When you have a wimpy little fire, it takes forever for the big logs to burn. When you have a wick boring fire, they burn a lot faster. But even the wimpy fire, if you let it go long enough, will burn the big pieces of wood. So you come to realize that there's a certain aspect of it, that it's a time versus intensity to get the amount of char that I see There are some limits to that because there's a fire that's small enough that it simply just can't penetrate deep enough into a large wood member And so the smaller fire is not capable, even even a very long time, where the large fire can do it in a reasonably short time And how can you, for example, going on the timber, how can you tell the damage that was during the fire versus post-fire smoldering damage, for example?

That's a great point.

One of the issues that the scientific method demands you use and we talk about this all the time is what we call victim versus cause. And this comes up all the time in electrical fire, where somebody says, oh, i found that this electrical fire is shorted, it's heating on it. It obviously had arcing. Okay, that may be reliable evidence, but it supports two hypotheses. One hypothesis is that it was the cause of the fire. The other hypothesis is it was the victim of the fire, and sometimes we simply don't have enough other evidence, reliable evidence, to determine which one. In some cases we can look at it and say, since we can reliably put the origin of the fire over here, the only way that that damage that wiring could have occurred is if it was still energized when the fire got to it And therefore we can now say that that makes it the victim.

By the same token, if we say this is right in the middle of where our reliable fuel source is that can be readily ignited by a brief electrical spark, now, because hypothesis is in play, When you are facing a post-flash-overed fire, to what extent you can still see the facial difference in fire damage, because I would assume that as soon as you transition into flash-over, most of your compartment would be a victim to a very similar heat fluxes.

Maybe I'm wrong in here, but Close flash-over fires add significant challenges to the fire investigator And I'll give you an example. One of the things that we ultimately determine over the years of doing 921 through some testing and stuff is we used to think that low burns again were indicative of an arson fire, where somebody poured something on the floor and it caused fire, so you had a scar on the floor, for example, right. So you see that the rug has been charred and everything is said. It's an arson. Okay, that may be a reasonable hypothesis, but it's not the only hypothesis. And one of the questions you have to ask is did the room flash-over? What the compartment would flash-over? because we now know that the radiant energy from the hot upper layer can burn the carpet post-fire. So we now are in a scenario where we have two potentially different, conflicting hypotheses and we have to use other evidence to reliably determine what We had an arson fire that we determined was an arson fire that ultimately wasn't prosecuted, where we were able to show that this was in a business. There was burns down the aisles of carpet. The issue of flash-over was raised and what we showed we used modeling to do this is the fire, because it was a big space never got a deep enough layer in the ceiling further away from the fire to have caused the carpet damage. Closer to the fire, where the layer was deeper as it started to become a ceiling layer, as it went from being a plume to a ceiling layer. Close in, it had enough radiant heat to be able to burn the carpet, but we showed that further away, there was no way to get carpet spread, And you had to look at two aspects, because the radiant heat doesn't have to be enough to burn the carpet. It may be enough to warm it up sufficiently that you can still get spread along the carpet. And we had to look at both aspects and what we ultimately determined was these burns were far enough away that there was insufficient heat from the upper layer to have allowed the fire to spread that way naturally.

To close on the use of scientific method, you said that it ends up with a verdict when you have a final test hypothesis, how confident or how much proof you have to have for your hypothesis to say it's a verdict, or how does the hypothesis change from being a hypothesis to being a verdict?

Again, that is ultimately a question of how much have you tested it, how much have you used reliable evidence, how much have you used the laws of math and physics to challenge it And have you been able to eliminate all other reasonable hypotheses? And again, one of the things I like to point out is people this idea that a hypothesis is any way. I think it can happen. I said no, the scientific method requires a hypothesis to be falsifiable, and by that we mean I have this piece of reliable evidence. I can say that hypothesis can't be correct. And the example I like to give so people can understand this is how do I ever rule out the scenario that my fire was started by invisible little green men from Mars? It's not a falsifiable hypothesis. There's no amount of evidence I could ever collect that would allow me to falsify that hypothesis, because they're invisible. And, by the way, if they're invisible, how the heck do we know they're green? And so I always challenge people with the well, wait a minute, you're going to say that that's your hypothesis. How are you going to refute my hypothesis that this was started by invisible little green men from Mars? It's key. The concept of a hypothesis is has to be falsifiable. There has to be a reliable piece of data that, if I have it, we'll say that can't be the hypothesis. And so you constantly have to challenge your hypothesis and you modify it if it fails a partial challenge, like the scenario we talked about. The room hypothesis wasn't wrong, but the first corner hypothesis was we challenged that. We found out that that didn't hold up. So with additional data that becomes reliable evidence, we're now able to come up with another hypothesis. Do we stop there? No, we have to say okay, is there a third hypothesis? And if I can think of one, can I falsify that compared to the second hypothesis that I want to hang my hat on? And so it's a constant process, never ends, and that's frustrating for people And it's frustrating for the courts, because courts want finality And the answer is I can only give you the best answer based on the reliable evidence I have today.

But in the end it's better to leave the case undetermined rather than go into false hypothesis, right, absolutely? What about biases? Do NFPA even lists expectation bias, confirmation bias? The investigator might have their presumptions or their favorite cause of fire, perhaps even. I guess scientific method is also something that defends us against that right.

Yes, And so one of the examples we used to see a lot in Orson Fires an investigator shows up to the scene of a house that's for sale And his first photo is of the for sale sign in the front yard before he's even looked at the fire. Okay, we go back to again. That's data, but is it reliable or relevant? And the point is there are houses for sale, millions of houses for sale every day in countries all around the world that don't have fire, and there are millions of houses around the world every day that have fires in order for sale. So a for sale sign is in no way indicative of whether this was an Orson Fire or not. And yet before 921, literally, we would have investigators going in to testify in a criminal trial and the first photo they would show to the jury was the for sale sign. It's like no, that's not relevant and reliable. And you've now biased your investigation because by taking that picture in your mind, you've set the idea oh, this must be an Orson Fire because the house is for sale. And that is a great example of expectation bias. One of the other places that we see both expectation confirmation bias is investigator goes out in the field, makes certain field determinations, collects evidence and brings it to a lab. You tell the lab hey, i'm pretty sure that this was an arson fire and that somebody poured gasoline in the carpet samples. Can you analyze these carpet samples and tell me whether they got gasoline in them or not? Well, you've now already fixed in that person's mind, either consciously or unconsciously, what the answer is. You want And all human beings kind of want to please their friends and their superiors, and so there's a tendency to find the answer that somebody expects you to find, rather than the objective answer, and that's one of the ways that bias comes in. And so what does the scientific method say? to get past those biases, you have to do things like do double blinds, you know. So send it, send the samples out to two different men and don't tell them the scenario. Simply say can you analyze the samples and tell me what the molecules are in there and then get the data back and determine where that leads.

I keep thinking about one question to what extent the firefighting operations damage your data and perhaps evidence in the scene, And can you account for that? Do you interrogate or do you do interviews with firefighters about how they did the operation? to count it in Absolutely?

And firefighters are important in a couple of different ways. One they're much more trained observers of fire and understand what they're seeing better than a layperson. So their observations are important And oftentimes these days, because of radio communications, those observations oftentimes are time stamp.

So they are record the times.

But there is a constant problem with I used to say when I was in the fire department we have a terrible PR problem, because if the fire doesn't destroy the building, firefighters generally do more damage to the building than the fire does in order to save it. We cut a hole in your roof and break out your windows and that sort of. So there is the issue of accounting for in what ways the firefighters change the fire scene, and there's been some increasing research in recent years to look at, say, how does a whole stream affect certain evidence during firefighting operations? How does the change in ventilation that firefighters create by cutting a hole in the roof, by opening certain windows, how does that change the progress of the fire? And can we now go backwards and account for that in our hypothesis? And if we can't, then we have to question whether our hypothesis is valid or not. Another way that sometimes modeling can help, and I'm involved in a fire right now where we just massive measurement of the building effort was reconstructed So that we can model it and look at the time that the roof was breached how did the fire flows change and is that consistent with what the firefighters observe? And if not, then we've got to look at another scenario, because the firefighters clearly ordered this fire, because they did a good job of saving the building, and so it's important to understand to what extent they're altering the scene through their firefighting activities, both ventilation and putting water on it. How does that have to be taken into account in my ultimate hypothesis on origin, cause and responsibility?

Given that you have such an amazing experience over many decades in doing this, do you see the fire since changing? You said that one of the things that comes from investigations is to learn and do better. So I wonder, how do you see like seeing fires since the 1990s and today? are they very different from each other or it's the same thing?

That's a great question, i'm sorry to say. In February of this year I celebrated my 50th year of joining the IFCA fire department while I was a student at Cornell, so congratulations, too long a time. In those days, plastics were really just coming on the scene, if you remember the old movie The Graduate, where the guy says one word for you plastics, plastics, that's the future. It was just coming into being in the 70s, and over many decades we saw a change in furnishings, we saw a change in insulation, we saw a change in building materials, and one of the things we saw was rooms much more prone to flash over, because it turns out, as we learned, that flash over is not dictated by fire load but by heat release rate. And so when we had all these cotton batting couches, they may have had more fire load than a polyurethane couch just because of their density in terms of the total heat release, if you burned them completely up. But what we found was that the heat release rate was much slower, and so that they were much less prone to flash over. And so some of the rules of thumb of the investigation business that were valid before we had a lot of these post-flash over fire investigations now were so valid And we had to go back and reassess things. One of the examples was with the batting couch. You didn't often get the windows break, because windows again break by a fairly rapid change in the temperature of the glass, while it's confined, like the ice cube being dropped in the warm soda where it tries to expand rapidly, and it's confined because of the fray, and that's what causes the window to break. Well, with the slower growing fires we didn't get this, and so that was one of the things where we had to change our thinking as the materials changed, and for many decades. I can tell you it was very confounding because we had a mixture of these different types of materials and still, in a lot of places in Europe and other places around the world, you don't have all of the modern materials that we have in a lot of first world countries, and so the fire investigation and the fire investigator has to remind themselves about the specific material properties at the fire they're investigating. And that's again going back to the scientific method that says don't go in with a bias, don't think you know already what this is like when you walk in the door, because the materials may not be what you first thought they were.

The world is changing. The materials are changing, probably faster than ever before. How do investigators keep up with that?

Most fire investigators are not also fire researchers so they have to rely on other people to do the research And there are national labs in a number of places around the world in the Scandinavian countries, there are a number of very good labs in Britain and Canada and the United States and a number of other European countries. Some of them are collective and also academia companies like combustion science and engineering, where we do some of this research and do it not just as part of litigation we're involved in, but sometimes just in trying to better understand circumstances that we've seen. That's part of what brought about the window breakage. Research is trying to understand that. That's part of what brought about the work that we did on these loose connections that can generate these glowing connections electrically that are capable of starting a fire. We saw these fires and outlets in other places and why is this happening? It doesn't seem to make sense. So we got the University of Maryland to agree to give a student a master's degree if they could research that, and we funded the project and that was actually Dr McAllister's master's degree was in looking at electrical cars, and then she went on to the toxicology. We've done a lot of work looking at both the generation of toxic gases and the effects of them. Unfortunately, we can't really do human subject testing there, but in Jamie's doctorate she did rat testing that we could understand the uptake of hydrogen cyanide and what the post-mortem levels of hydrogen cyanide can tell you about the fire. One of the things that we've learned over the years about fire investigation where there are human victims or even sometimes animal victims, whether they survive or whether they perish is they are literally data collectors. The human body is an amazing data collector and so you can go and interrogate those bodies for additional evidence that can help you understand things and we can look at, for example, carbon monoxide levels in somebody who died, hydrogen cyanide levels. I'm sure that Dr Persher talked about some of these things and the modeling that we can do for four hours. Yes, i was involved with a number of other people when I was at university in the national there's technology funded projects on understanding the development of carbon monoxide in fires, so we now understand that a lot better and we can take that and put it together with the kind of models that Dr Persher has and say, okay, if this person has this certain level of carbon monoxide afterwards can tell us something about the fire they were exposed to And it's a way to test our hypothesis, because if they have a high COHB level and our initial hypothesis was a fire that wouldn't generate much carbon monoxide it says we've got a wrong fire scenario. If they've got a low carboxy-hemoglobin and that's consistent with our fire scenario, then that's one more check that says that our hypothesis survives.

Another challenge And to close up on the sources. I really love this toxicology and discussion because indeed victims can be very certain source of information about the atmosphere in which they perish to survive. You can tell what was in the air and by that, as David explained in his podcast episodes, you can figure out the equivalency factors what was burning, what was the composition of it. It's fascinating that you actually can do that. To what extent the building automation is a source of information for you, like fire detection systems. You probably also want to have that information right Absolutely, and just to finish up on the human factor.

The other thing is that burns can provide important information.

Society of Fire.

Protection Engineers a number of years ago and it's now in the handbooks undertook a really great analysis of looking at what levels of fire exposure lead to what levels of burn injuries, and so for victims to survive and even ones who perish, oftentimes the burn injuries provide us information in addition to the toxicology. Now for building fire systems, whether they are passive or active, detection or suppression system can also provide important evidence If they're reliable. we talked about when a smoke alarm goes off, compared to when somebody sees a fire, can provide important information. The activation of sprayer systems, activation of heat detectors Oftentimes in larger building fires that information goes out to remote stations and we can see sequencing Right and sometimes that allows us to actually follow the initial fire growth by saying, oh, they smoke. alarm in the left side of the room debated first and 30 seconds later the smoke detector in the right side of the room activated and Generally that tells you the fire probably started left side. But also modeling can help you verify that and say, okay, what choir do I need to have and how fast does it have to grow? so there's a 30 second time difference between when these two smoke alarms go off or between when the first and second sprinkler activate or Heat detector. so those alarm systems can provide very valuable data Which it be shown to be reliable which oftentimes it is can provide evidence for not only Formulating hypotheses but for challenging and the evidence is critical both for formulating and for challenge and what about the Accidental footage?

like people tend to record the fires today? Probably you wouldn't have that 30 years ago because no one had camera in their pocket and now everyone does so you must have a lot of Accidental snippets of videos. No one's recording a video for the whole duration and time step It's perfectly, but you have snippets of that. I know there's a group in London forensic architecture could do amazing reconstructions of fires from accidental footage. But in normal investigations is this a source of knowledge for you?

Absolutely. And again, one of the first biggest things it can do is provide you with ways to challenge your Hypothesis. Because if your hypothesis says the fire ought to be bursting out the side window 10 minutes into this and somebody's got a camera and it's time-stamped and it shows that It didn't bust out the window until 17 minutes into the fire, you got to challenge your hypothesis and so, even though they might not have captured the whole fire, they may have captured a snippet that you can now use to challenge your hypothesis. But one of the things you got to be very careful about and this goes to alarm systems too Is you got to make sure that you're all on the same clock and that the clock is accurate. We oftentimes find that there's a difference between the clock for an alarm system and the real time, and they can often be by a couple of minutes, and you have to be able to account for that. And Times shift the data by testing and seeing. Is there a difference? and, if so, if I can measure it Now, i can account for that, and that's one of the ways that I can use the laws of physics that time is immutable To be able to challenge my hypothesis and revise.

Richard, it was fantastic talking to you for the first time. I had a fire investigator in the podcast and I appreciate it a lot and I certainly need to do more of those because Actually this is also very helpful to engineers to understand. Like, if we understand how buildings burn and how fires happen, we perhaps can do better engineering to protect against those, and for my engineering audience, that's that's probably the thing they want to do. Any final words to maybe young Investigators coming to this industry Well, first to follow up on what you just said.

I think that's absolutely important to fire protection engineers Who who aren't fire investigator, that good, accurate fire investigations be done So that they can understand when and if they need to modify their design philosophy. So that is critically important. Oftentimes the the investigations get driven by more near-term issues of who pays, or does somebody go to jail or not. But the longer term issues are what are more important to the, to the fire Protection community. Does that mean I need to change materials I use when I do a certain thing? Do I have to design my compartments a different way So they last longer? You know all of those kind of issues. To the new fire investigators, here's the advice I always get yeah, understand the science as best you can, because the science is well proven and largely immutable. The one thing a young investigator can never best an old investigator like me on is years of experience. The fact in the matter is, whether you're you're 80 or 20, f equals ma. So if you understand that equals ma and you're a 20 year old investigator, you're on the same firm footing than an 80 year old investigator. So go to the literature, understand the science. Make sure you're well grounded in the science, because that's something that can put you on as close to possible, and even footing, with somebody who has 30 more years of experience That you can only get in 30 years fantastic.

Thank you so much, richard. This was a pleasure.

I really appreciate it. I'm honored to be on your show and Maybe we can do this again sometime and that's it.

Thank you, richard. There will definitely be a follow-up to this episode. There is so many things we need to further cover. It was very interesting to die with you to the subject of fire investigations, i must say for a long time in the podcast I distinguished two worlds of fire science one, the world that fire engineers live in, and One being the world of firefighters, where these worlds do not always cross and there's so much in common But also so many differences between them. Now, after talking to you and then reading up on an FPA 91, i see there's actually a third world. It's if we're living in fire metaverse. It seems there's a world of fire Investigations where different things are considered. There's a different view on fire science, which is interesting because we're all in the same fire physics and fire mathematics. But certainly Investigators see the world of fire different than the researchers do and, as Richard mentioned, this will overlap a lot because the investigators We relate to our science on having good hypothesis or challenging hypothesis. This is the basics of their work. They need our science to do that And we also need fire investigations to understand what are we doing in the world of engineering, how the choices that we do in designing buildings impact the real fires and Actually to understand what's the scale of the of the hazard out there. We often exaggerate the hazards of fires for some reasons and Yeah having investigated statistics, let's us catch up with reality and see where we really are with the fire problem. So thank you for listening. I hope this was interesting to you and I'm simply ashamed it took over 100 episodes of fire science show to finally have Investigations covered in it. But that's not the last episode on fire investigations in the show, so look forward to the future and next week, another episode, this time not investigations, but also something very, very interesting and useful fire for fire engineers. So see you here again next Wednesday. Thank you, bye. This was the fire science show. Thank you for listening and see you soon.