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PODCAST: Fire codes are written in blood

Brock Verville shares his unique perspective as a home inspector and a firefighter for the City of Albertville and talks about fire safety and fire codes.

Brock quotes that fire codes are written in blood. He explains that the purpose of codes is to correct something that caused injury or death in the past and they are driven out of tragedies or avoidable things that had occurred. They talk about the importance of smoke alarms, the type of alarms, their battery life, and the failure rate of old alarms. Brock highlights that the number one reason for fire deaths is non-operable or non-existing smoke alarms. Reuben shares about his smoke alarm set up at home, then Brock shares his two cents on it. Brock mentions how sprinkler systems are remarkably effective. 

They also talk about lightweight building materials and composite materials, window ventilation, and how they affect fire progression. According to Brock, most fires start in the kitchen, most also start with electrical fires. He talks about the fire tetrahedron where a sustained chemical chain reaction is required for fire to occur. He discusses the transitional and defensive attacks in putting out a fire and shares how to limit ventilation during a fire and what to do when trapped in rooms. He gives a summary of what happens when the fire department arrives on the scene. He highlights that the number one cause of firefighter death is heart attack and cancer because they’re exposed to so many chemicals that leach to their skin. 

Brock explains that his report as a home inspector during fire inspection is to highlight the intent of the codes. Then he shares examples of the intent of certain codes such as the sprinkler systems in commercial areas. He then shares reminders and best practices to prevent fire and be safe at home. 



The following is a transcription from an audio recording. Although the transcription is largely accurate, in some cases it may be slightly incomplete or contain minor inaccuracies due to inaudible passages or transcription errors.


Bill Oelrich: Welcome everyone. You’re listening to Structure Talk, a Structure Tech presentation. My name is Bill Elrich alongside Tessa Murry and Reuben Saltzman, as always, your three-legged stool coming to you from the Northland talking all things houses, home inspections, and anything else that’s rattling around in our brain.


BO: Well, today we’re just a two-legged stool because Tessa is unavailable, so she’s not on the show, but it’s Reuben and I, and our special guest today is Brock Varvel, and he’s a home inspector here in Minnesota. He’s also a fire inspector for the City of Albertville, and he’s also a paid firefighter for the city of Albertville, and we’re gonna dig into some fire safety topics today, and we’re really excited to have Brock on the show. Thanks Brock for joining us.


BO: We’re gonna get into a fire safety conversation today and talk a little bit about some of the safety features that we see in houses, and why they’re there. Brock, I’m gonna throw it to you right away because you had… When we were prepping for the call, you had a good saying that fire codes are based in what? Why don’t you go ahead and tell everybody this lovely but gory saying.


Brock Varvel: Yeah, so, first day a fire inspector one, a certification course, my instructor said, “Why do we have codes?” And his response to us was, “Codes are written in blood.” Now, what do they mean by that? That means, codes aren’t just derived by somebody saying, “Hey, you know what, let’s restrict the way that people can build or let’s make it harder for somebody to put together this and that.” The purpose of codes is to correct something that caused injury or death in the past, so a lot of these things that oftentimes don’t make a lot of sense to us, really are driven out of tragedies or avoidable things that had occurred, and what we’re trying to do is prevent re-occurrence in the future.


Reuben Saltzman: And he’s on the show today because he’s got a really unique perspective, being both a home inspector and a firefighter, looking at it from both sides, so I think he’s got a really good appreciation for how sometimes people might roll their eyes at some of this stuff, I mean, you’re doing a home inspection and you’re talking about some of the safety stuff and, you know, a lot of times people go, “Yeah, yeah, you’re a home inspector, you’re paranoid.” But it’s like, “No, no, no, no. This really does matter.” So, what are some of the biggest stuff that you come across during home inspections when it comes to fire safety that… It’s a big deal for you? 


BV: Well, obviously go with the number one on the back of everybody’s mind because it is both the most important aspect of fire safety as well as the most annoying for most people, and that’s fire alarms, smoke alarms, you know, and smoke alarms, there’s a lot of information about them, and there’s a lot of information that people just really don’t truly have about smoke alarms. Now, what is the biggest eye-roll? Obviously, it’s coming down to changing batteries, most people aren’t aware of the fact that, look, you’re not supposed to change the batteries when it starts to beep, you’re not supposed to change the batteries once a year, the saying is, “You change your clocks, change your batteries.” And the reason for that isn’t necessarily that the batteries are being drawn down that quickly, the reason is… The number one reason for fire death is non-operable or non-existing smoke alarms, and so it’s that important that you just don’t wanna take the chance that a battery is faulty or a battery has lost power and the smoke alarm isn’t going to operate properly. So as annoying as it is, change your batteries that frequently. Now, the industry has remedied that a bit with these 10-year sealed lithium-ion batteries where now you don’t have to go and change them, and that is a really fantastic ad because it makes it harder for people to disable their smoke alarms, it’s a more intentional act, they can’t really forget to give it the power that it needs.


BV: And then the last thing is is, when the 10-year ones beep at you, they’re beeping at you for one very important reason, and that’s that the smoke alarm is now expired, and that hits a really important point as well. People are oftentimes not aware that these smoke alarms, they don’t last forever, they expire, 10 years, that’s all you get, from date of manufacture, 10 years. And, you know, talk about one of the things I call out on home inspections very frequently is expired smoke alarms. Oftentimes I’ll even get response from some agents where they say, “Well, did you test them, do they work? Well, what are you testing when you press the button? You’re testing the audible alarm, you’re not testing the sensors.


RS: Yeah.


BV: And so, what you’re encountering is is, you get this false sense of security, as I pushed the button, it beeped. “Great, it works.” The reality is is though, once you exceed 10 years of life, the failure rate of a smoke detector can exceed 30%. Now, let’s put that in perspective. A recall would be issued if a smoke alarm on line manufacturing had a failure rate in the neighborhood of 1.5%. 30% is the observed failure rate of smoke alarms older than 10 years, it’s that important to change them out regularly.


RS: And I’ll bet that’s past 10 years, and I’ll bet it continues to get worse and worse as every year goes by. I mean, we see a lot of smoke alarms that are 20, 25, 30 years old. I mean, what we like to say is, once it’s turned yellow, it’s surely more than 10 years old. You don’t even need to take it down. That’s just how you know.


BV: Oh my God. Yep. Yeah, absolutely. Yeah, when I see ’em yellow, I don’t even check the dates, I’m just like, “You know that it’s way too old”


RS: That’s good.


BE: I’ve got a smoke alarm in my second floor that’s been there since the day we moved in, and it’s probably been there at least 10 to 15 years prior to us moving in, and I wanna claim this as a relic, I wanna see how far it goes before it just gives up the ghost, but we have four other smoke alarms within three feet of this thing, so I’m not concerned about it, it’s hard-wired and it looks funny, and it’s gonna stay there until… I don’t know, it quits making noise.


RS: And it’s not being lazy. That… Okay.


BO: Yeah, that’s exactly right.


RS: Alright.


BE: You carry on.


RS: I gotta ask you this and I will open myself up to criticism and condemnation from you… Be honest now, you talk about replacing your batteries when you change your clocks twice a year, and I’ll admit, I do not do that. I have a home where all of my smoke alarms are hard-wired and interconnected, and I’ve got fairly… Well, they’re all new batteries, they’re new smoke alarms, I’ve put in all new alarms when I moved in, and I’ve just got this idea in my head that… Well, because they’re already powered, it’s like, it’s gonna be fine, and, honestly, I don’t do it until they start chirping at me, how bad is that? Be honest.


BV: Well, you know, you’re right that most people don’t, and I would say myself, I’m guilty of that. It’s just not top-of-mind, not to mention too, if you’re talking about nine volt batteries, they’re not cheap, they’re not easy to find, it’s probably the only thing that really truly runs on a nine volt anymore these days, but the reality is is this, so the purpose of the battery is battery back up.


RS: Yep.


BV: Right? So, could it be a non-issue? Sure, if you had a fire ignition while you had power supply to your house, sure, then it’s gonna draw power off the electrical system and you’re not gonna have an issue, but what happens if it’s a lightning strike to the house and you’ve lost power. Now, that backup is a matter of life and death, and this is where the numbers start to get really kind of frightening. You go back 40, 50 years, safe time to evacuate a house fire was 17 minutes, if you were out of your house in 17 minutes, you had a very good chance at surviving that structure fire. Now, that timeline is shrunk down to three to four minutes, that’s it.


BO: Wow! 


RS: That’s wild.


BV: And so, you lose time, and that becomes a big problem.


BO: Why is that? I know it’s partly to do with materials, but is it also to do with the way houses are built now, you’ve got these framing members that oftentimes are webbed and they’re wide open and there’s a lot of oxygen and there’s a lot of air, and that can move through that, does that cause a fire to move much more rapidly than in a house that was built with far less air chases, so to speak, in there? 


BV: Yeah, absolutely. So, it’s again… It’s kind of a multi-faceted thing, so one, you’re right, building materials have changed. Fundamentally, we’ve moved to lightweight construction materials, the reason isn’t that they’re better in all regards, the reason why we’ve moved to lightweight construction materials is that solid wood is basically cost-prohibitive at this point, so all these lightweight construction materials kind of harbor one fatal flaw, either one you’re talking about composite type materials, in which it’s bits of woods that is compressed and glued together, in which that glue is petroleum-based, which means it’s solid fuel, it’s basically, it’s an analogy, it’s not actually gasoline, but think of it as solidified gasoline, so you have a higher fuel load. The second thing is, when you get into trusses, trusses are small runs of lumber that are held together with gusset plates, these gusset plates, when a fire achieves 1,200 degrees temperature, the gusset plates begin to warp, steel begins to warp at about 1,200 degrees. Structure fire inside of a contained room, when it reaches flash over, you’re talking 1,800 degrees, so you’re easily reaching the point at which gusset plates will warp. Well, when they warp and those teeth pull out of the wood, all the little tiny bits fall apart.


RS: Sure.


BV: And so what you really encounter is, one, you have heavier fuel loads, you have a higher propensity for structural collapse, so if you’re talking legacy builds, old, long runs of solid lumber, in a lot of… Basically testing of structural loads under fire impingement, you’re talking about structural collapse achieving… Occurring, I should say, at around an hour, hour and a half of fire impingement. In new construction materials, you’re finding structural collapse in as little as seven and a half minutes, and so… And that’s unprotected floors, and so again, we have codes like firewalls, fire breaks and things like that that are meant to protect those structural members so that you don’t have that. So that’s one end of it.


RS: There’s a big one that came out in 2017 for all new construction, and I know that was driven by fire departments, it was protecting our floor structure, any time you got engineered lumber, you can’t just leave it exposed anymore, it’s like, that’s why we see drywall on basements on just about every new build now, which…


BV: Absolutely.


RS: It’s a little bit obnoxious, as a home inspector, I can’t see any of it, and it feels like it’d be obnoxious for somebody who wants to finish their basement someday, it’s like, when you wanna run everything, you gotta take it all down, and then you can run all of your pipes and your wires and ducts, and then put it all back up but it’s like… It’s not there to make your basement look nice.


BV: No, in fact, I actually had a large national builder, and I’m sure you’ve probably encountered this on a few inspections where they really kind of fight you on new construction, they’re like, “Why are you even looking at it?” kind of thing, or “You can’t go there. I’m not gonna let you pop the attic.” That kind of stuff, and… So we are kinda going around what I’m going to be inspecting, and the guy said, “You know what, let me ask you a question, why did they make me put drywall in the crawl space of this structure? Why am I finishing a crawl space area?” And he had no idea, and the reality is is, yes, it’s a fire break, so unprotected, those floors can collapse in seven and a half minutes, you add half-inch drywall, it’s now 20 additional minutes because gypsum is non-combustible, eventually it will spall, but… And fall apart, but it will give you 20 minutes additional life on any unprotected floor.


BO: Brock, where do most fires originate now in 2022? If you could give me the top three.


BV: The number one is kitchen, and it’s funny because if you look at some of the fire codes, like… There’s a room in our house that is built basically like a fire containment box and that’s the garage. Garage has firewall requirements up and down and left and right, it’s basically saying, “Hey, you’re guaranteed to have a fire start in the garage.” And the reality is is that most fires actually start in the kitchen, and most of them are gonna be that. Obviously smoking ranks right up there still, that’s never gonna go away. In fact, fire fatalities as a whole, when you look at fire fatalities of themselves, it’s smoking leads that year after year after year.


BV: And that’s really what it comes down to. What we also see is electrical fires, electrical fires are probably number three in there, but what’s really interesting, when you look at firewall requirements inside of garages and stuff, I have been on a number of structure fires where again, the reality with this lightweight newer construction is is that when we get on scene, it’s not uncommon for the building to be what we call fully involved, so fire has already vented itself outside, there’s nothing stopping it from progressing, it’s what we call a fuel-limited fire, which means that thing’s gonna burn until it runs out of fuel, if we don’t go in there and interrupt, and I guess maybe I should rewind slightly and just give you guys kind of a little fundamental of fire dynamics, so I’ll refer to things in what we now term the fire tetrahedron. So, several years ago, we used to call it the fire triangle, saying, what is required for fire… For self-sustaining fire to occur, and it used to be the fire triangle where it was, you need heat, you need fuel and you need oxygen.


BV: And now we’ve added a fourth, which is you need a sustained chemical chain reaction for that fire to occur, and in order to stop fire, you have to remove one of those, and then fire just… It’s not gonna perpetuate. So you had mentioned it earlier, Bill, where you said, “Hey, these open chases, are we seeing more oxygen delivered to the fire?” And the answer to that is, absolutely we do. So back 40, 50, 60 years ago, most structure fires were ventilation limited, so if a fire started and nobody changed the conditions, they didn’t leave a door open or break a window or something like that, the firewood run out of oxygen and it would actually go into decay phase, and sometimes it would actually put itself out. Now, with all the open concepts, we don’t have ventilation-limited fires anymore, we have fuel-limited fires, which means they’re gonna go. So getting back to my story is, we find that these now fuel-limited fires when we get on scene, they’re ripen. So, the days of fire departments making entry into the front door and putting a fire out inside of a room, you know, some older construction you can still have that.


BV: By and large, you really aren’t finding that’s the kind of fire attack that we’re into, now it’s transitional or defensive, which means, transitional is we’re hitting it from outside, we’re knocking the flames down enough, now we’re making entry and we’re putting the rest of the fire out and going in to overhaul where we’re picking out the last little bits of hot spots, or it’s defensive, which means, we’re hitting it from outside, we’re trying to protect neighbor houses from starting on fire, and that’s about as far as we can go, but I have been on numerous structure fires where the fire burns through the entire house, basically there’s not a whole lot left of the house, and there’s a garage, and you open up the garage door and inside the garage, it looks like nothing had happened inside of there. The firewall, which was designed to stop fire from going from garage to house, did it in reverse and it stopped the structure from transferring into the garage, and it’s really impressive on how well that drywall can actually work at stopping the progression of that fire.


RS: So it sounds like we need to start doing these in kitchens is what I’m hearing.


BV: Well, again with open concept, yeah, it’d be great, but nobody’s gonna go for that because… Yeah.


RS: But then it won’t be open.


BV: Exactly, and then everybody’s gonna hate that tight claustrophobic feel of the kitchen and nobody would do it.


RS: I say it totally tongue-in-cheek, but…


BV: Absolutely. But we had an attempt at a fire code that would have done that, and that was the requirement for sprinklers.


RS: Yeah.


BV: Sprinkler systems are remarkably effective. I have yet in my fire career to be on scene to a structure fire where there was sprinklers there and the fire was still going, it will stop it at incipient phase and it’ll keep it from progressing or it’ll slow it down to the point where we’re basically just wetting down a small little fire, but they are massively effective…


RS: Yeah, yeah, that was in our code for three months, I think, and it didn’t take long for the Builders… Builders Association to really fight that and get rid of it.


BV: Yeah.


RS: I gotta tell you, right around that time, it was when I was still blogging for the Star Tribune, I did an April Fools blog, first and last one I ever did, I said there’s a new requirement in Minnesota where all existing homes are gonna need to be retrofit with sprinkler systems, not only that, in lieu of guard rails on the sides of open stairways, you can actually use ball pits now, like they have at Chuck E. Cheese, and I had all these little tells, but it made me learn, I learned this day that people don’t read, they just read headlines and people read the headline and the state started getting flooded with angry phone calls, and they contacted me like at…


BV: Oh no.


RS: 7:30 in the morning, and they were not very happy with me, and I’m like, “I will fix it right away.” So that was my first and last attempt at April Fools humor.


BV: Yeah, people are definitely sensitive to that.


BO: Brock, a couple of things, you said seven and a half minutes to fully engulfed if there isn’t any limitation on the ventilation, like there isn’t fire stops from one floor to another, that doesn’t give you as a firefighting crew a lot of time to get there, get unloaded, set the trucks up and start spraying water. Second question, do most fires start when people are awake or when they’re asleep? 


BV: Well, I think that it’s… I don’t know if I would really characterize either, it’s so random, it seems like my mandatory months where I have to respond overnight, they’ve happened overnight, and then the rest of the time they happen during the day, but it really is kind of hit and miss. We always say it’s…


BV: When we haven’t had a structure fire in a while, sudden get ready, and they’re gonna come in flurries and we’ll sometimes go six, seven, eight months without a structure fire and then get three in the span of two weeks, and so it’s really a random thing, but your response to a structure fire is very different, night-time or daytime, part of the now asks from our recommendations, I should say, from, say, Fire Marshal office is smoke detectors inside and outside sleeping areas.


BV: Now we’re talking about that obviously as a code. Now, why did they add that into code? Because the recommendation is is you sleep with your bedroom doors closed. Now, why would we want people to sleep with their bedroom doors closed? And having toddlers myself, that oftentimes is very hard to do because you start shutting bedroom doors and they don’t like it, but the reality is is that what you’re trying to do is you’re trying to restrict fires movement. So a fire got started, and let’s say your egress was blocked, having a bedroom door closed can provide a cocoon of survivability for a period of time, and when a fire department arrives on scene, what is paramount… One of the first things that’s gonna happen is the first arriving truck, the person in the front right seat is your officer on the scene, their job, number one, is, they’re going to do a 360 around the house, they’re gonna walk around the house and they’re gonna look at smoke, they’re gonna look at, can they determine where the seat of the fire is, and they’re gonna give the arriving crews and their own crew and they’re gonna tell them, “This is what we need to do to effectively fight this fire.”


BV: What they’re also looking for is people that are trapped, yelling out of windows, things like that, so they want bedroom doors closed so that, you know, hey, if you can’t get out of your bedroom, you keep that door closed and what you’re gonna do is, again, you’re gonna limit ventilation, that fire is not going to be able to easily achieve oxygen, so it will go elsewhere where oxygen is more readily available, which may give you enough time for the fire department to arrive, see you banging, yelling on a window, which… Again, you don’t wanna open that window and necessarily start feeding oxygen into the structure, you wanna yell and bang on the window as loud as you can, and as soon as an officer sees somebody doing that, our job, number one, is get a ladder, get up there, get that person out.


BV: So always life preservation, we always say in a fire department, “We’re gonna risk a lot to save a lot.” Human life, we will risk a lot to save a human life, we’ll risk very little to save very little. We are not sending firefighters inside to save your couch or $90,000 Shelby Mustang that’s in the garage, that’s not what we’re gonna risk people’s lives for, but if we see somebody that is alive inside of a structure that’s job number one, is to get them out. So it’s things like that. So, with your bedroom doors closed, smoke alarms, especially if they’re interconnected, you’re gonna be alerted, you’re gonna wake up, if you can’t make it out, you’re in a safe spot, at least initially.


RS: Now, you talk about windows, and I just wanna hear where… How you report as a home inspector when you come across a house, say 1950s house, and none of the windows there meet today’s standards for egress or emergency escape and rescue openings as we now call it in the building code, what is your comment to clients when you come across that? 


BV: So… Again, there’s a reality in home inspecting of, you know, we could walk in there and say, “Oh my gosh, this is the most dangerous house you’re ever gonna be in, this is not meeting modern egress requirements.” And what’s gonna happen is, you know, somebody’s gonna maybe get freaked out, maybe they don’t buy a house, maybe that’s the right house for them, I feel like our job is to more present material fact. So I report it as, “Hey, this is not meeting egress requirements modern.” I explain that, “Look, you’re grandfathered, so it’s not gonna be required.” But what we look at in fire inspecting is something very important, which is intent of code. So what is the intent of the code? So when you have a minimum opening space on an egress window, what’s the intent of that code? Well, a larger adult human being can make egress out of that window, when we talk about well requirements of having permanently installed well ladders, it’s so that somebody can climb out, when we’re talking about sill height, it’s so that a small child doesn’t have a difficult time climbing out of that window, but you can meet the intent of the code even if the window itself doesn’t meet that egress requirement.


BV: So, let’s use the sill height, you get into Minneapolis and there’s a lot of houses that the sill height is above that minimum 44 inches. So what’s the intent of the code? It’s to make it easily climbable, so what I tell people is, “Hey, be aware that if you’re gonna have a small child in this room, you maybe wanna have a desk, a bed, something right up here against this window so that they’re not climbing that full 45, 46 inches, they can climb on to something and then out the window, and the intent of the code is met. Now, the best example I can give of this intent of code is the code that says that commercial structures over certain square footage have to be fully sprinkled. Well, we have a very large commercial structure in St. Paul that is not fully sprinkled, that’s Xcel Energy Center. It’s not fully sprinkled. Now, why? Well, over the bowl, where the ice is, if you had sprinklers and there was a fire at ice level, that water would never reach that fire, it would evaporate before it ever got anywhere near it. So the sprinklers would be ineffective, so the intent of the code on sprinklers is to buy time for people to evacuate the structure, so what they’ve installed instead is a smoke removal system that they can actually ventilate smoke out of the arena, which gives enough safe time for people to evacuate because the smoke would be ultimately the most dangerous thing if there was a fire at ice level.


RS: Fascinating.


BV: And so, did they meet the code? No, they met the intent of the code, and therefore it’s allowed.


RS: Sure.


BO: I have a question as it pertains to commercial buildings, a lot of them are still drywall, other things that don’t really burn, and I imagine the Xcel Energy Center, what could really burn in there? 


BO: I guess it’s a lot of things, but it seems like a fire wouldn’t spend a lot of time in there, it would die itself up pretty quickly, is that fair to say or not really? 


BV: Yes and no. So… What you’re talking about construction type is type one construction is your concrete, the type you’re talking about with dry wall and steel is like your storefronts kind of thing, that’s type three construction, so you’re right, the structure itself doesn’t burn readily. A lot of that stuff is non-combustible, and the idea behind is, is you don’t want structural collapse, but your interior fire load is very different, so if you had a type one construction which is non-combustible construction material, but it was full of wood pallets, oh, that thing is gonna get ripen, and that’s gonna be a dangerous fire to fight because the fuel load inside the building would… Actually probably classify as what we term a special hazard, so when you’re into Xcel Energy Center, something like that…


BV: Well, you have plastic seats, you have all kinds of things that can burn inside of a non-combustible overall structure, and what you’d really run into is the toxicity of the fires that come off of those type of materials. So when we’re talking about fires being so dangerous nowadays and type of smoke that are in fires, a modern fire, there’s somewhere in the neighborhood of 8,000 known carcinogens inside of structure fires these days. In fact, now rapidly… So it always used to be that the number one cause of firefighter death nationwide was heart attacks, and cancer is really quickly passing it. Cancer is the number one concern we have because we’re exposed to so many chemicals that leach into our skin, that we’re far more likely to develop terminal cancer than the general public.


RS: Interesting.


BV: And so, if you’re thinking about a fire like inside of Xcel Energy Center, and you’re thinking about people evacuating, what you’re more worried about is the Phosgene gas, these Hydrogen Cyanides, these things that are given off from the fire that could cause people to die, even if the fire was nowhere near them, and so the idea there is your interior fire load still provides a very dangerous environment.


BV: That’s why that smoke removal is what they use to provide a tenable atmosphere for people to get out.


BO: As somebody who’s in this field, is there a reasonable amount of time you can work as a firefighter where you’re not significantly putting yourself at risk? 


BV: Depends on the fire, it really does. So, at the end of the day, what you’re ultimately looking at is, yeah, there’s limitations to our gear, and the biggest thing is we need to be on air, our air bottles are for the most part rated in the 20 to 30 minute range, the reality is is when you’re working as a firefighter, you’re probably 10, 12 minutes off air before… Not out of air, but at the point at which you’re not gonna make a dangerous situation that’s already dangerous more dangerous by running out of air and making your co-firefighters come in and rescue you. And so, when you start getting low on air… So you’re really in and out kind of thing, if we were talking commercial structure, again, collapse would be the biggest concern I would have, and so that’s gonna be really read on, what is the fire condition…


BV: What is the building doing? That kind of thing. And what are we saving? So that’s ultimately what it comes down to. In a residential home fire, there’s a guy that was on the department with us for years, and he ended up taking a job up in Bemidji, and I talked to him like a year after he went on to that fire department, and he said it’s incredible how many room and contents fires we put out, where you’re actually making entry and putting out a single room. Now, why? Construction up there is different, it’s older construction. You get into our area where it’s a lot of new construction, and the fires are really, by and large, fully involved when we’re getting there, which is why you go out to suburbs and you see people always comment on how much space is between houses… That’s defensible space, that’s a fire code, the idea there is, you pack houses in as tightly as they did back in the day in Minneapolis, St. Paul, fire is gonna jump from one structure to the next, to the next to the next, and it’s gonna be a big problem when you have a single structure fire.


BO: That’s interesting, I wonder, there’s a lot of teardowns and rebuilds in the city, and I wonder how they’re addressing that because the set-backs aren’t changing, are they? 


BV: No, they’re not. So a lot of it comes into grandfather provisioning, so if they’re able to maintain whatever the city has as their grandfather provisioning, they can achieve it that way, but cities might also, so that they’re not losing that buildable space, they may throw up requirements. So the bigger concern that I have a lot of times is less about the knockdown rebuilds, ’cause then the city can really kinda dictate, “Hey, this is how we want you to construct it.” A lot of times they’re actually gonna put in requirements for non-combustible siding, you go to these old neighborhoods, what do you see a lot of? Stucco, brick, the old asbestos tile type siding, why? It’s non-combustible, protects the house from starting if their neighbor did, and then you have a guy that rips that siding off and throws vinyl on, and his house is four and a half feet from the next house, that’s gonna be a problem if one structure starts.


RS: Yeah.


BV: And so that’s kind of what you run into is is, the city can require certain things, they can say, “Hey, if we’re gonna let you build here and we’re not gonna make you adhere to the side yard setbacks, then you’re gonna build it this way.”


BO: How much space do you need between two structures before like… 1,200 degrees, let’s just say, is that a good… Is that an average fire heat, or is it much hotter than that? 


BV: Inside… Interior it can be. Absolutely. Outside it’s gonna be less because obviously the heat’s gonna go up, it’s gonna dissipate, you’re gonna get more radiant heat, that’s going to affect nearby structures. Now, that being said… So every municipality can set their own setbacks, that is city-by city basis.


BV: But I’ll tell you that, out here we have a lot of space and pretty common that you’ll see melted siding, like, the neighbor house didn’t start, but the vinyl siding was definitely affected by it, so it’s a concern, but that being a concern, that’s also one of the things as a fire department we pay attention to. If we have a structure on fire and it’s fully involved, well, our focus can somewhat, not shift off of that structure obviously, we’re doing what we can to put that out, but we will also probably pull attack lines to cool neighbor houses so that we’re not raising the risk that those houses will ignite.


RS: Sure, yeah, I’ve got a buddy who lives in Otsego, and one of his neighbor’s house had started on fire, and he sent me pictures of the neighboring house, I mean, this is a newer development, they had big setbacks between the properties, but still all the vinyl siding was gone. I mean, it had all melted off the house just from the heat from the one house, crazy how much it affects it.


BV: The source of the fire in a situation like that, a brand new house…


RS: I don’t know.


BV: Occupant behavior? 


RS: Don’t know.


BV: You can oftentimes find that information with the State Fire Marshal, if it’s determined, and that’s… When you get into fire investigation is kind of the joke of, you know, every fire is undetermined until they can pinpoint an actual cause. So you always hear a fire investigator being interviewed in some sort of high-profile fire, and they’ll say, “What’s the cause?” And they’ll say, “It’s undetermined.” Undetermined doesn’t mean arson, it doesn’t mean anything other than, “We just can’t pinpoint it yet.” Some of these structures burn so completely that there really is no way to determine, and so it will remain undetermined, but then there are some where they can kind of go back, and it’s a really fascinating subject, fire investigation, of how you can tell… So you get into like smoke alarms, did the smoke alarms go off? You can actually tell in a fire investigation if the smoke alarms are preserved, you can actually tell whether or not it was sounding when the fire was going on, and the way you tell that is, is that the vents for the audible alarm, you’ll actually see this kind of starburst pattern of soot depositing if it was sounding from the vibration of the alarm sounding, whereas if it didn’t, you don’t get that pattern, and so they can tell if a smoke alarm has been sounding or not. It actually… That’s a great tangent into the discussion of types of smoke detectors, because this is…


BV: It’s a really contentious debate, there’s a lot of information out there, and there’s a lot of information that can really kinda heavily go in the direction of scary and feel like it’s a dangerous over-simplification. So, there’s two types of smoke detectors that exist, there’s photoelectric and there’s ionization, an ionization detector detects the ionized particles that come off of the actual flux, the actual plasma of the flame. A photoelectric detector is detecting that visible black smoke from a smoldering fire. Now, there’s a lot of data out there that says, “Well, hey, photoelectrics are far and away better than ionization.” And yes, they are depending on the lens you’re looking at it, so ionization detectors detect quick-flaming fires, photoelectrics detect smoldering fires. There are two different types of fires, both can occur in a house, so a misnomer is, “Hey, we just don’t see fast-flaming fires anymore.” Not true. They can still happen. A ionization detector will detect a quick-flaming fire on average 52 seconds faster than a photoelectric will, but a photoelectric will detect a smoldering fire on average 26 minutes faster than an ionization. So you look at that and you’re like, “Well, I’ll take 26 minutes over 52 seconds.”


BV: But the correct answer is is, you don’t have to give up time for either, it’s important for you to have both present in the house, we shouldn’t be going away from ionization detectors, we should require both to be present. Ionization detectors to save you 52 seconds, let’s go back to that evacuation discussion, what was the safe time to evacuate a house fire in a modern structure? Three to four minutes.


BO: Three minutes. Yeah.


BV: Let’s go to the scary number, three minutes, you lose 52 seconds with only photoelectric detectors, you just lost a third of your evacuation time. You don’t wanna do that. Now, on the flip end, there’s a lot of the discussion of, well, ionization detectors just never even went off. Well, why didn’t they go off? If it’s a smoldering fire, and let’s say it’s 26 minutes before they’re gonna detect the ionized particle off of the plasma, well, probably that structure is burned to the ground in that amount of time, so… It never went off, it didn’t get a chance to. And there’s studies out there where they replicated this and they said, “Look, these ionization detectors don’t even work.” Well, they do, just not in that type of smoke environment, and so having both is really key and give yourself the maximum amount of time to get out.


BO: Yeah, that actually makes sense. And ionization alarms are not expensive, they’re just a few dollars and you can leave them laying around, I mean, it’s not a burdensome thing. Do most fires start because of occupant behavior or is it because of a failure of some sort of device or electrical or… Is there any statistics behind that? 


BV: By and large you’re gonna be talking about occupant behavior, you’re gonna be talking about people just not following… And it doesn’t necessarily mean the homeowner, sometimes it’s contractors as well, where they’ll put something together and, I mean, Reuben you may even have stories on this too of… I have so many times that I’ve had electricians, older electricians call me and say, “You called the double log out in the panel. Well, I’ve been doing that my entire career and I’ve never had an issue.” “Well, okay, yeah, you might not have had an issue, one, it doesn’t meet code, so… End of discussion there, but all you need is one, and it’s not worth the risk.”


RS: Yeah.


BV: Right? So, you have the situation where things can be either assembled or… Just done in a way that is not a 100% as safe as it could be, and then you have occupant behavior where you have things like people smoking, people plugging space heaters into power strips, things like that, people are using extension cords as permanent wiring…


RS: Sure.


BV: Where the cord drop across that run is gonna generate heat and you have stuff like that, so occupant behavior or human behavior, I think, is gonna be far and away your biggest thing.


RS: No, I get it. You talk about electrical, I gotta ask, what’s your take on arc-fault circuit interrupters? 


BV: They are very useful. So what the arc-faults will do is, yeah, they’re gonna sense that arc which… Any time you’re gonna have a fire, typically you’re talking about arcing in the electrical system, things like that, so it’s gonna basically catch it at its earliest phase and it’s gonna cut the power to the circuit, which is invaluable when you’re talking about, “Hey, let’s stop a fire before it ever begins. Great.” Now, at the end of the day, you get into mechanical things and if they’re not, there’s potentials for failures in them, if people don’t exercise the breakers, if they’re not sure that the arc-faults work, I mean, there’s maintenance to anything, and that just adds another aspect of that. I’ve talked to some firefighters that said, “Hey, we’ve had all these fires in which the arc-faults never tripped.” Granted, there was definitely a first generation of arc-faults and things have steadily improved, I think some of those Cutler-Hammer, the CH type breakers, the earliest generation of arc-faults around 2000, 2001, they were massively sensitive, ran really hot, like you put a thermal camera on them, and they’re in the neighborhood of 70-ish degrees hotter than a standard breaker, which an arc-fault will run hotter than a standard breaker, but they were definitely beyond that.


BV: And what did Cutler-Hammer end up doing? They ended up redesigning the breaker and they’ve got the newer version, which is… Doesn’t have the issues. So… But yeah, as a whole… Again, the reason why it’s there is it’s prevented fires for sure.


RS: Sure.


BO: Do you see secondary fires happening from melted electrical lines or something like that, or a gas line that has been damaged in a primary fire causing a bigger issue later on, or even during a fire, do you get secondary explosions and things like that when continuously running gas all set in a line will melt, or…


BV: Yep, yep. So we can definitely run into that, so controlling utilities is one of our earliest jobs on a structure fire, as long as it’s safe to reach the gas line, we’ll shut the gas off and we’ll lock it out so that somebody can’t turn it on. So yeah, there is definitely controlling utilities, things like that, it’s just one of the hazards that we have to pay attention to, it’s interesting that you bring up gas lines because, I mean, it’s so ad nauseam, I have to hit it with CSST and the bonding requirements for it, I’ve seen fires that didn’t get fully going, but there was scorch siding and a smell of gas, smell of natural gas after a lightning strike, and it was from unbounded CSST where it arced out of the line.


BV: And so there’s things where, yeah, these requirements, again, really come into play to avoid a lot of this stuff, and back to the human behavior, if not done properly, you can create issues and so… But yeah, secondary fires, for sure, you can have that. We’ve had a number of garage fires where people were storing propane tanks and things like that, and man, when those things bloody, they definitely get your attention.


BO: Do those things blow up when they get super hot? 


BV: They do, they do. Yeah, they’ll BLEVE, so it’s liquefied petroleum, so heat it, it’ll eventually boil. When liquids boil, you’re talking about massive expansion ratio, so expansion of that generally in the 1,700 to one volume increase, so now you’ve hyper-pressurized this vessel, and the point at which that steel fails from fire impingement, it’s gonna rupture and all that gas that’s now hyper-pressurized is gonna expand to that 1,700 to one volume increase, and what ends up happening as soon as it exits the container, well, there’s immediately a flame that ignites it as it expands to 1,700 and one and you get a very energetic explosion. Now, fortunately with those smaller propane tanks is is limited amount of fuel, limited amount of explosion, if we were talking about large LP tanks, they have pressure relief valves that they’re trying to prevent that from occurring, but if one of those things actually BLEVE, that would be a really dangerous event, really dangerous.


BV: That’s funniest thing you’ve… Want a really impressive training to go watch a fire department? Come out our way and watch us when we do our LP tank training, or well, actually simulate an LP where the pressure relief valve has triggered and it’s like a 60-foot flame spewing out of a tank and you set your water streams to a fog, which basically is just this big fan of water, think of it like spray on your hose, and we overlap them and walk in and the fog actually pushes the flame back to the point at which we can expose the tank and the person in the middle reaches in and shut the gas off, and then you retreat back with it in fog.


RS: I would very much like to see that.




BV: It’s really cool, it’s really cool. The next time, I’ll send you an email. The next time we do it, you’re more than welcome to come out and watch it.


RS: Sounds like being on the set of MythBusters.


BV: Kinda, yeah. And the reality is is this is… My guess is, if that that was an actual scenario, we wouldn’t go anywhere near the tank because, again, what are we saving? Now, we would do it, sure, if there were people trapped, but if people had evacuated… Yeah, we’re not walking up to a hyper-pressurized LP tank, we’re gonna basically cool the tank and if it ruptures we are far enough away that we’re not gonna get hit.


BO: These things don’t rupture and blow apart to pieces, they’ll just seam or something we’ll develop and then a large quantity of the gas will escape and things will settle back down, is that usually the case? 


BV: No, well, if they truly BLEVE, there can be shrapnel. There’s…


BV: There are some cases where some fire departments lost firefighters because of it, where LP tanks have BLEVED and they were hit, and there’s one where there’s photos of it and like half the tank was, A, it was flattened, but B, it was like several hundred yards from where the LP tank was and it flew a long distance, so it’s a particular hazard for our firefighters, for sure.


BO: This word you’ve used it several times, can you spell it? 




BO: Yeah.


BV: It’s B-L-E-V-E. So it’s an acronym, it stands for Boiling, Liquid, Expanding, Vapor, Explosion.


BO: Got you.


BV: So you boil the liquid, the vapor expands, If it exits the contained structure, it explodes and so…


BO: Got you.


BV: And you wanna see some of the best? Yes, MythBuster-esque videos, just Google BLEVE and… They’re frightening.


RS: Nice.


BO: Well, I think we should begin to put a close on this, but Brock, I wanna ask, more fires start in a house or in a garage? 


BV: In a house.


BO: Okay, what percentage of the time do garages go versus a house going? 


BV: It’s a tougher thing to answer in terms of percentage, one, I don’t have an actual percentage on it, but number two, it more has to do with fuel load. A detached garage is probably more likely to go up than an unattached garage, because people are working in detached garages sometimes differently, and so it’s more on what are you storing in it? Are you storing fuel? Let’s say somebody has a wood shop in a detached garage, well, that’s gonna be more of a hazard because you’ve got saw dust, which is highly, highly flammable, potentially they’re varnishing, and if you have polyunsaturated oils and you store the rugs on top of one another, they’ll spontaneously combust.


BV: And so you can have oily rug fires that there was no ignition point, they actually spontaneously combusted from the oils that were on it, and so it’s all over the board as to terms of what type of hazard you’re ultimately looking at. Now, at the end of the day, it really comes down to the biggest thing that you can do is not necessarily focus on how the… You obviously do wanna focus on how fires start, but there are fires that’ll start that you really didn’t have any ability to prevent, an electrical fire, something like that, where you just couldn’t determine it, the freak type of fires. And the number one thing that homeowners should just be aware of is, is all those things that just get annoying to hear in terms of fire safety, make sure you have smoke alarms on every level of the house, inside and outside sleeping areas, have carbon monoxide outside sleeping areas within 10 feet. And notice, I’m not saying bedrooms, I’m saying sleeping areas, if you have a basement where somebody is sleeping, it should be treated like it’s a bedroom in terms of code requirement, so sleeping areas is the way that now the fire marshall terms it.


BV: Have an evacuation plan, make sure that everybody knows if smoke alarms go off, where to go, how to get out, if their primary egress is blocked, what is their secondary form of egress. Know that… Look, with the timeline shrunk down as much as it is, as much as people don’t like to inconvenience fire departments, with three to four minutes being your evacuation, don’t lose time trying to determine whether or not it’s a false alarm on your smoke alarm. Leave the house. Let the fire department come. I promise you, there is not a firefighter alive that does not fully enjoy riding lights and sirens, fully geared up, even if it’s for nothing, we enjoy it every time. I become a six-year-old me every time I do it, and so, just rely on that fire department. Let us come, we’ll figure it out, and if it’s not anything, we’ll tell you it’s not anything, and then we’ll give you the peace of mind, but just treat it really, really seriously, because a lot of these deaths that occur are preventable, they really, truly are.


BV: And it just takes the information being out there. One of the biggest things I had said to you, Reuben, at the onset of the discussion of having this, the topic was, we’re in a really unique position as home inspectors that we get to be inside these houses on these walk-throughs with these brand new homeowners and this really should be a discussion point in these home inspections where we can say, “Hey, this is how fire may behave in your house, this is what you can do to be safe, these are the things to kinda keep in the back of your mind.” Because we have an audience that, one, it’s pertinent, and two, we’re able to hit basically everybody after your… Everybody’s gonna be buying and selling houses.


BV: Everybody’s having this discussion, we’re gonna be able to get this information to everybody, and it may save lives, and you know what, the fire inspectors always say, they’ll save more lives as a fire inspector than they would as a firefighter. But nobody will ever know that he did it.


BO: Thank you, Brock. I think we’ll wrap on that, and thanks for all the information. That voice was Brock Varvel, home inspector, Brock, fire inspector, Brock and… Brock, you are on the department in Albertville, correct? 


BV: Yes.


BO: Yep. Okay, awesome. Well, that’s great information. I think every house needs a number, they need their number the time you have to get out of that particular dwelling, maybe stamp it on the wall somewhere. Thank you, everyone. You’ve been listening to Structure Talk, a Structure Tech presentation. My name is Bill Elrich, alongside Tessa Murry and Reuben Saltzman. Thank you for listening and we’ll catch you next time.