Rod Ammon: Welcome to the CFITrainer.net podcast. Today, we're taking a deep dive into fires where the ignition was associated with CSST, that's corrugated stainless steel tubing. There's a lot of confusion and misunderstanding about CSST, and we're hoping to demystify that today with two guests who have special expertise and experience in these types of fires. They'll also have a warning for you. Fires involving CSST are on the rise, and we're going to talk about why and what you need to know as an investigator or other professional who responds to fire scenes. CSST is in almost every new residence constructed today. Before we begin, we'd like to acknowledge that this episode discusses the line of duty deaths of firefighter Nathan Flynn and Captain Josh Laird, in two separate but nearly identical incidents where a lightning induced arcing event caused a small hole to form in the wall of a corrugated stainless steel tubing and created a sustained gas flame that ignited structural members and combustibles in the basement or crawlspace ceiling. Both firefighters were conducting suppression on the first floor and fell through the floor into a burning crawlspace or basement. By discussing these tragic losses, we hoped to spread awareness about fire causes involving CSST and save lives in the future. Our hearts are with Firefighter Flynn and Captain Laird's families, friends, and departments. Special Agent Adam St. John with the Bureau of Alcohol, Tobacco, Firearms, and Explosives is a licensed professional engineer, an IAAI-CFI and an ATF CFI candidate assigned to the Baltimore Field Division. His primary responsibility is fire and explosion origin and cause examinations of incidents affecting interstate commerce or where ATF assistance has been requested. He regularly teaches classes on fire dynamics and fire investigation. Prior to becoming a special agent, he was an ATF Fire Protection Engineer at the Fire Research Laboratory for nine years, performing technical laboratory testing to assist fire investigators in determining origin and cause. He also responded with the National Response Team to provide expertise in engineering, industrial process, and fire protection systems. He's also a former captain and EMTB with the Montgomery County Maryland Fire and Rescue Service. Special Agent St. John has received numerous accommodations, particularly for his work on the Stricker Street Fire where three firefighters were killed in the line of duty. He's with us today to talk about CSST fires and his research into the line of duty death of firefighter Nathan Flynn. Joining Special Agent St. John is Captain Craig Matthews of the Fire Investigation Division of the Howard County Office of the Fire Marshal. He is an IAAI-CFI, IAAI-FIT, IAAI-ECT, ICC Certified Fire Inspector, and a NAFI CFI. He is a lead investigator with over 350 investigations. Captain Matthews is also an ignitable liquids detection canine handler with more than 250 call outs. He has received several departmental awards, including Firefighter of the Year, the Meritorious Service Award, and the Bronze Medal of Valor. Captain Matthews was the local investigator at the fire where Firefighter Nathan Flynn died. Special Agent St. John and Captain Matthews, welcome to the podcast. We appreciate all of your work and your time with us today. I watched the video that was produced about the fires that took the lives of Firefighter Flynn and Captain Laird. They were very well done and difficult to watch. Two firefighters that seemed to be doing their job so well and yet what seems to be a very unique type of fire surprised them with brutal results. All of your research and teamwork that went into that final product will surely make a difference in the future. I hope we can make a difference today by talking about what you've learned.

Captain Craig Matthews: Thanks for having us.

Special Agent Adam St. John: Yeah, thank you, Rod. We appreciate it.

Rod Ammon: So thanks again, gentlemen. I want to talk generally about CSST first, then let's get into the line of duty deaths of Firefighter Flynn and Captain Laird. We'll start basic. What is CSST and how's it used in residential construction?

Captain Craig Matthews: So CSST, it's also known as corrugated stainless steel tubing. It's a thin wall of stainless steel. It's flexible. It bends without kinking. Typically has a thin protective jacket typically of a UV resistant polyethylene material. Most CSST applications we've seen is either a yellow or a black jacket. Typically your yellow jacket is a non arc resistive jacket and typically your black jacket is an arc resistive jacket. There's three different types of CSST that we're seeing, at least in the Maryland area, which is the yellow, the black, and then there's also a multilayer jacket, CSST, which is also black in color. It's on top of the thin wall of the stainless steel, there's that UV resistant polyethylene material, and then there's a layer of aluminum mesh. And then it's topped with another layer of that polyethylene material. The arc resistive jackets are more prevalent these days than the non arc resistive. Just last year we went to the Senate in Maryland and we were able to get the yellow, the non arc resistive essentially banned for new installations in the state of Maryland to where now the only application for CSST in new construction is the arc resistive jacket. The CSST will pretty much survive the fire. And fire investigators should analyze for origin and cause purposes, especially after known lightning events. But even we've seen it to where a common household electrical current has also arced to the CSST. So if fire investigators are seeing this, they should examine the CSST in their area of origin.

Rod Ammon: It also sounds like they should make themselves aware of the different types and maybe look at examples of the different types as they learn more about this. Because I think you went through three or four different types that would be visually different, correct?

Captain Craig Matthews: Yeah, the arc resistive and then the multilayer is similar, just the visual inspection of it without cutting through that outer layer protective jacket to see how many layers is there and whether it's the multilayer or just the arc resistive jacket. And the purposes of the arc resistive jacket is essentially to give it some more surface area to disperse that energy from a lightning strike.

Rod Ammon: Well, that sounds like a great improvement. So what's the hazard of CSST? How does it fail and what happens when it fails?

Special Agent Adam St. John: Yeah, Rod, I'll talk about this really quick and just take a step back. Where CSST is used and why it's used. So it's generally, since the early 2000s and even the late 1990s, it's just replaced black iron pipes. So we're talking both about residential structures but also commercial occupancies. And really it is replacing black iron pipe because it's a lot cheaper and easier to install. So you had that big cost savings. It initially was created as a safer alternative due to seismic earthquake activity. It bends with the structure so it doesn't break in the same way. But unfortunately, when we talk about the hazard of CSST, because it's so thin and flexible and cost effective, it's more susceptible to arc energy. So electric arc energy can actually cause an arc hole to form. What I want the fire investigators to understand is it's a relatively new technology. There's over a billion linear feet of this stuff installed across the United States, and it just continues to become more and more popular. So essentially it's just a means of conveying fuel gas throughout a structure, typically a residence, and it can be anywhere from really where it comes out of the ground, feeding the gas meter all the way to the end appliance. So talking specifically, what are the hazards of CSST? Why should fire investigators care? Why should firefighters care? It's both a fire and it can be an explosion hazard too. So this stuff is relatively safe for a lot of applications until you have an electrical arc actually occur, and that can cause the arc hole to form within the CSST. So that electrical arc current can be a function of lightning, and that's probably where we see it most often is as energy associated with lightning is dumped into the structure, whether it's to the CSST or from the structure that then arcs to the CSST. That concentrated arc energy actually, causes a small arc hole to form within that wall. Obviously, we talked about before that the CSST contains pressurized gas. So at that point, the second part of this hazard, of this failure process, is that perforation in the gas line will leak some of that fuel gas. Now, what can happen, and what typically happens is that arc will cause the hold to form, but will also ignite the escaping gas. Alternatively, based on the pressure of the gas, the size of the hole, the presence of obstructions, that actual flame will not sustain in certain circumstances and then you have the potential for an explosion through a fuel air explosion and an accumulation of gas. These gas systems don't have circuit breakers like electrical systems do, so that gas is just going to continue to flow until either the propane supply runs out, which could take days, or in terms of natural gas, it'll flow indefinitely and either have that sustained flame or it'll leak that gas. So when we talk about the potential hazard, this stuff is used more than ever, and then when you have a leak, it's going to continue to leak or sustain flaming or leak the gas until somebody turns that gas off.

Rod Ammon: I want to make sure we're not missing this, and it might be me and my lacking hearing. I remember one of the things that we talked about was the fact that it's hidden as well. The location of the lines, did we discuss that or did you discuss that?

Special Agent Adam St. John: Yeah, it's something that's kind of unique to CSST. We as engineers design your household electrical system to contain failures. We put the connection points in junction boxes or the wire in conduit so if a failure occurs, it doesn't necessarily ignite the structure. Now, when we talk about CSST, it's run pretty much anywhere it'll fit. So we're talking interstitial spaces between floors and walls. And when you have this arching event, like you said, Rod, frequently the first fuel ignited is the structure. And that structure will continue to burn. You'll have the mass loss, the consumption of the structural components as that fire continues to grow. And that's when we start talking about collapse hazards to firefighters and fire investigators as well.

Rod Ammon: Yeah, watching what you did with the modeling and everything else and to see that and to see how long the firefighters were looking for fire must've been very surprising for a lot of folks. Let's talk about the line of duty death of Firefighter Flynn. It was 7005 Woodscape Drive. Can you briefly summarize the incident including how the fire started?

Captain Craig Matthews: Yeah, I can summarize that. So the fire department was initially called for smoke inside of the house. When the fire department arrived, they had what they initially described as lazy smoke presenting across the front of the house. And what we've come to find out is that this house was 8,400 square feet. So the fire department did not realize at the time that they had a large fire burning inside of the structure. And that's why it was just presenting with lazy smoke because it takes a long time for 8,400 square feet to essentially fill up with that smoke and to start producing turbulent, high velocity smoke, which is your typical indicator that you have a pretty decent working fire inside of the structure. But as far as the investigation goes, the fire was classified as natural by the investigative team, which resulted from a lightning strike to a large tree in the backyard. And then the energy that came down that tree, then went to the ground and essentially unearthed the soil, almost in like a six inch trench from the tree to an underground storage propane tank, which was a couple feet away from the tree. And then from there, the energy then followed the copper supply line of the propane from the underground storage tank to the structure. Once it reached the structure, it then transitioned to CSST. There was a short line of CSST that then went to a manifold. The CSST then branched out off the manifold to each individual appliance that was supplied by the propane gas. What we realized was that that energy from that lightning strike, once it was on the CSST, it was essentially trying to find its path to ground and it resulted in an arcing event to a piece of metallic that was close by in its effort to try and find its path to ground, which then resulted in the arc hole forming in the CSST, releasing fugitive gas, which simultaneously essentially ignited. And it was also within close proximity of the floor joists of the crawlspace within that structure. So as Adam spoke about it, your first fuel that was ignited in this situation was your lumber of your floor joist system, which in return then ignited all of the combustible storage that was within that crawlspace.

Rod Ammon: Thank you, Captain Matthews. It's surprising to me when you say that the dirt trenched from that lightning. The energy just is amazing. And then to go all the way from the tree through the dirt into the tank and then onto the home. It's amazing energy.

Captain Craig Matthews: And the energy just from that lightning strike alone that evening was three times stronger than any other lightning strike within a five mile radius. So it was about 68,000 amps of energy.

Rod Ammon: Wow. So is there anything, here I am going off track already. Is there anything that they think drew that energy strike or is it just random?

Captain Craig Matthews: Yeah, it's just random. As far as myself as a fire investigator, I haven't been able to determine why lightning likes one thing versus another. I don't know if Adam can speak on that or not, but as far as my experience, it appears to be just random.

Rod Ammon: Yeah, I guess from the power perspective, but.

Special Agent Adam St. John: Yeah, Rod, I think you bring up an excellent point, why are we talking about this now more than ever, and part of that is there is data out there that suggests we're getting, like Craig said, Captain Matthews said, more energetic strikes and more lightning strikes in general. And I think that's due to climate instability where you have rapid changes in temperature just create more lightning strikes that typically are stronger. And there's a direct correlation between how strong a strike is and the size of that arc hole. So one of the things I think we'll talk about later is ways of preventing arc hole formation due to lightning. But the truth is sometimes you get these strikes that are just so energetic, it's incredibly hard to channel that energy to ground in an effective way without causing something to arc or catch fire somewhere in that house.

Rod Ammon: Captain Matthews, I'm wondering if you could talk a little bit about how the crews responded when they first showed up at 7005.

Captain Craig Matthews: It was initially dispatched as what Howard Kenny described at that time as a local box, which just sent three engines, a ladder truck, a battalion chief. Once they arrived on the scene and they did have smoke presenting from the structure, they did upgrade it to a full box, which adds additional apparatus, additional chiefs, a safety officer. The first engine was directed by the battalion chief to position in the rear of the structure because there was a large swimming pool in the rear, and this was a non hydrant area. So they positioned in the rear of the structure so that way they can use the hydraulic pump to essentially draft water out of the swimming pool to at least get the initial suppression operations underway until they can establish a larger water supply. So the firefighters initially went into the first floor through what was described as a mud room through the rear of the structure. Once they got inside, they were confused because they had smoke floor to ceiling. Again, it was lazy. They had some heat on the floor, so they backed out thinking that they had a basement fire. There was a geographical change within the grade of the structure to where on the rear of the house, half of it was the first floor was that grade, and then the other half of it stepped down and the basement level was now at grade. So they repositioned their hose lines and went around to the basement entrance. When they got into the basement, again, they had lazy smoke. They used thermal imagers, they weren't seeing that they had any fire within that basement. So they're trying to figure out where this fire is because a portion of the house had a crawlspace, the other portion was a full basement with, I don't remember off the top of my head, but it was about 12 or 14 foot ceilings within that basement area. So they're still trying to figure out where this fire is located. And then about that time, there was a lieutenant that was on the back of the house where that first floor was at grade, and they had called out that they had fire showing through what they believe was a first floor window. So at that point in time, the suppression companies had backed out of the basement and repositioned back up to their original entrance.

Rod Ammon: So what were the parallels between Woodscape Drive and the line of duty death of Captain Laird three years later?

Captain Craig Matthews: So I'll let Adam speak on that because ATF led the investigation with Captain Laird. I was their assistant, but I'd like to let Adam speak on that one.

Special Agent Adam St. John: Yeah, right off the bat, Rod, I think the parallels were undeniable. You have large structures, relatively new single family homes, open floor plans. So Captain Matthews mentioned the amount of air available and light smoke showing. But in both of these incidents, you had very well-developed fires. So we had the same ignition sequence. We have lightning induced failure of CSST located between the basement and the first floor. In both of these cases, the flames first presented on the first floor, which is where these firefighters went with charged hose lines, with root crews in place to put out the fire. And in both cases, you had that sudden structural collapse between where the flames are evident on the first floor with the firefighters falling through the floor into the basement and immediately transmitting maydays. So these guys were calling for help. We had personnel on the scene, we had personnel standing by, and these conditions were so bad these rescues just couldn't be made in time. One of the things that became very evident are these flow paths that develop when after the collapse occurs. So you have the floor is a good barrier between the seat of the fire in the basement or the crawl space and where these guys are the first floor. And when that barrier goes away because of that collapse, we realize very quickly with the computer modeling that that first floor becomes completely untenable. So we talk about the similarities, it's the same ignition sequence, it's the same collapse, it's the call of the mayday, but it's also the rescue of these firefighters just wasn't viable from where crews were on the first floor. They had to get a crew around to the basement. I think we realized very quickly that we have two incidents that are very similar. That 7005 Woodscape Drive was not an isolated incident. You had two structural line of duty deaths in the same state, with the same cause of the fire within three years of each other. Maybe we should collect some more data and look into this.

Rod Ammon: So I'm guessing this had a lot to do with your candidate research. Can you talk about why you picked the Flynn LODD as a subject for your candidate research?

Special Agent Adam St. John: Yeah, sure thing. So with ATF one of our jobs, and one of the things that we really strive to do is to provide investigators, and sometimes firefighters, with research and the stuff that just hasn't been looked at and we want to gain a better understanding of. I think the ignition from lithium ion batteries is being researched and electricity is being researched. But really the whole process of what CSST fires, of how they ignite, how they present, how flame spread, and in this case, how the structure is consumed, became something that we wanted to look into. So because there was no data and we realized this wasn't an isolated incident, we wanted to look into it. And frankly, the job that Howard County Fire Department, the state investigators did collecting data, we knew that we had a lot to work with at both of these cases, and we could really process that data to generate a work product to show what happened and then expand upon that data to try to figure out what we can do differently in the future.

Rod Ammon: And it seems like you did a real good job. Can you describe the research methodology and the work you did with these? You had quite a few collaborators.

Special Agent Adam St. John: Yeah, we really did. So Howard County was excellent. Frederick County was excellent. Frankly, the wives of both line of duty deaths, so we're talking about Celeste Flynn and Sarah Laird have been incredibly involved in all aspects of the investigation. So we had a great team behind us. And we talk about the scientific method to determine any origin and cause of a fire, that same scientific method applies to research. So the first step is that data collection, and that's where the scene was so important. We had a good understanding of fire dynamics, lots of witness statements. In both cases, the electronic data was critical. So Captain Matthews talked about the lightning strike data, the 911 calls. We had the forensic Apple watch, the biometric data, the movement data from that, the SCBA, portable radio, actual movement data and channel data. So compiling all that, that developed an excellent timeline. From a testing standpoint, anytime we do testing in a laboratory environment, we want to have a good understanding of what those variables are. So working with Captain Matthews, we actually restored gas to the gas system inside of Woodscape drive to figure out exactly how tall that flame would be with the same pressure loss from the tank through the exact same hole. We were able to characterize the length of that flame in different orientations. So when we went to the lab, we could have a good understanding of how to recreate that flame in a laboratory environment. One of the things that their fire chief asked for, and Captain Matthews early on was a computer fire model. And a lot of that is we had to have good data, junk in, junk out. But if we have good data in, we know we can create a good computer fire model. So we built a large portion of the flooring system in the lab because we really wanted to characterize ignition, flame spread, heat release rate. In this case, mass loss was really important, when that structure actually collapsed. So we couldn't build the entire house in our lab, but if we build the stuff that matters, how this fire started and spread, moved and eventually collapsed, we can use that really good quality full scale fire data to create a computer model to hopefully, tell the whole story of what happened. So it's really following the scientific method from the scene, to the lab, to the actual computer model in the end to tell the story of what happened.

Rod Ammon: Yeah. I noticed you even had a load on the floor when you were doing some of that testing, which I thought was interesting. Like you said, getting all the data as close as possible to recreate and capture so you can learn from it. What were the main things you learned from the field and full scale fire testing?

Special Agent Adam St. John: Yeah, so we really tried to come up with good tangible takeaways for our fire investigators out in the field. What do we look for for CSST fires, but also what we learned here is that fires in large houses burn quite differently. So the biggest, the hottest topic in fire investigation, rightfully so for the past 10 years has been ventilation. The flame front propagation to areas of ventilation and how our fire patterns are driven by ventilation is so important. And what we realized is that that also applies to large structures. So we realize our fuels release so much energy a lot quicker than they used to. And usually what stops that energy from being released is when that fire runs out of air. So a smaller structure is going to have less air available, so you have a rapid heat release rate, a rapid consumption of the air inside of that structure. But when you put that same fire and those same fuels in a large house, it takes a lot longer to consume that air. So when we talk about what that means to fire investigators, but also firefighters is you have a lot more energy being released before they arrive at the scene because you have a lot more air available to these fires. So the first part was, we can't apply our understanding of fire dynamics from a smaller 1,200, 2,000 square foot house to an 8,000 square foot house. We need to think about these fires differently and really understand that the amount of air available to these fires is different. So these fires are going to develop differently, and frankly, you can have rapid changes within the structure as you try to fight these fires. So the first finding was the extremely large volume of both residences and the fact that these fires started on a basement level where that smoke was available to fill the whole house and you had fresh air available to feed this fire, not only increased the heat release rate, but the increased heat release rate means you increase the mass loss, so the available fuel burning, which in this case the fuel is that structure. So not only do you have more energy being released, but more of that structure is consumed. So you have to start thinking about structural collapse issues, which we clearly had at both fires. The second thing we talked about was the fact that elevated fires are different. So we as fire investigators, typically, have a good understanding of fire dynamics, but we don't convey a lot of these points to the firefighters in the field. So Captain Matthews was saying when these guys entered the mudroom, they identified that this fire was below them, and then they went to the basement and they identified the fire was above them. How is this possible? And in reality, they were absolutely right because it was an elevated fire. So you have a fire in a crawlspace that was allowed to basically grow until it ran out of air. But the height of that smoke layer is elevated, so it doesn't appear to be a basement fire because the smoke isn't down to the floor, but it certainly isn't a first floor fire because it's located in between. So one of the things we realized is, hey, we need to do a better job training our fire investigators and also our firefighters about elevated fires and what that means. And a lot of these CSST fires occur in elevated spaces. So you take a peek in the basement and it appears clear because that fire is in the interstitial space, consuming the floor system. And then as soon as you're under the first floor, you're talking about collapse problems. So a better understanding of elevated fires is warranted because a lot of these CSST fires are elevated. The last two things I'll touch on very quickly, the ventilation flow path existed once that collapse occurred. So you have the firefighter falling through the floor and that changes everything. We said that ventilation is key, and now you have a large opening above the seat of the fire and it's dumping all of those gases up through that opening. And unless you do something to absorb the energy from that fire in the basement or the crawl space, it just isn't viable at either location to rescue that firefighter through the floor. And the last thing was the fact that CSST in particular, is a fire that inherently because it's running in the interstitial spaces, will attack that structure. So it's something that we need to consider and we need to start thinking about taking a peak in that interstitial space as we start to do our size up of these fires, especially if a storm just rolled through and we think these fires could be CSST related.

Rod Ammon: Yeah. I remember that In both situations, the chief or whoever was incident commander did do a 360. Besides the fact that that crawlspace was sort of hidden and you didn't know it was there if you were a firefighter, was it the firefighter Laird's location where the chief couldn't even see the staircase going down? They couldn't even caught on to what was going on from doing a 360.

Special Agent Adam St. John: Yeah, you're exactly right. That structure, the staircase was hidden on the side that you couldn't access because of a fence. So we don't believe that Captain Laird was aware that there was a basement stairway there. And where he entered was from a concrete patio to a tiled floor where there was no indication whatsoever of a basement there. So you're going from a solid concrete patio to a floor, a tiled floor that appears to be solid and feels solid, and then all of a sudden that tiled floor lets go. And ironically, both Captain Laird and Firefighter Flynn fell through a floor that was tiled with a non-combustible top surface. So essentially the combustible part burned away completely below, the floor joists and the OSB. But that left, basically, an unsupported tile floor that went collapsed, goes from appearing to be nothing in terms of heat, no flame extension, to all of a sudden a giant hole on the floor with both firefighters in the basement or the crawlspace at that point.

Rod Ammon: Which probably looks perfect if you're able to see it until it breaks and yeah, that's rough. I'm sorry, you were going to say something?

Special Agent Adam St. John: Yeah, and you make a great point. And what's another tool that these guys in the field use is a thermal imager. And these floors are so thermally thick that even on the thermal imager from our testing, there was no indication of a well developed fire below. So we're trying to give these guys indications and stuff they can look for. So even if they could see through that smoke and use that imager, that imager showed that the floor was relatively cool and there was no indication of this well-developed fire below that, non-combustible material or the multiple layers of non-combustible material of that time.

Rod Ammon: Yeah, you're using a material that people would put around a fireplace except it's on the floor. Let's step back to the fire investigator side of this a little bit more. Can you take us through the development in the crawlspace and relate it to what was observable by fire investigators afterwards? Cathy had told me she wanted a particular eye toward indicators of elevated fire, forensic indicators of CSST arcing, and how you trace the lightning event path using physical indicators and data.

Special Agent Adam St. John: Yeah, so we talked briefly before about really putting eyes on that interstitial space, whether you have to poke a hole in that ceiling or not. And one of the indicators in this case was the fact that, Captain Matthews mentioned, these ceilings are 12 to 14 feet high. So you had an elevated smoke layer, but it was relatively faint, and that was because this fire located seven feet off the floor in the crawlspace, just didn't have smoke that banked down that low. So you have, what we call a cyclic heat release rate process, where the fire grows, it starts to run out of air without that smoke layer ever reaching the bottom. So understanding how elevated fires burn differently and become ventilation limited differently is something that we need to really focus on. Craig, do you want to talk at all about how we traced out that CSST line or actually looking at how these are arc holes formed?

Captain Craig Matthews: Yeah. So the origin and cause investigation was about eight days long. The entire contents of the first floor, living room, and dining room had collapsed into that crawlspace area. So it took us a couple days just to kind of start excavating all of the debris within our area of origin and try and start identifying ignition sources that were in the area. So once we got through most of the excavation, we left a lot of the copper electrical wires in place. We left the CSST in place. We're looking for any arc damage that could be there. We have some knowledge that CSST is prone to lightning induced failure causing these fires. So initially, the engineers from ATF had put water to the CSST line in an effort to try and locate the arc hole. Because the arc hole is so small and sometimes it's very difficult to find, especially with all the soot and the damage to it. So we're trying to identify these arc holes as well as we have to identify what's just mechanical damage from the collapse to the CSST. So once engineers had put the water to the CSST, we were able to quickly identify holes that we didn't initially see by the naked eye. So then we would mark those holes. And there were several holes in the line, but then we had to go back and look at each one of the holes to identify whether it was arc induced failure or whether it was, again, mechanical, the CSST being stretched because of the collapsed floor above on top of it. So that's how we traced it out and we identified the arc holes. And then, like Adam spoke about already, we then put propane at the same pressure back to the line and put an open flame to it to try and identify what kind of a flame height we were getting. We did vertical, we did lateral and we did downward because at the end of the day, we truly don't know what the orientation was of that arc hole in its place prior to the collapse. But we can suspect that it was probably most likely either lateral or facing upward, and it was diffusing off of the flooring system. So that's how we traced it out, and we identified the arc hole within that CSST line.

Rod Ammon: So the reason you couldn't tell is because the CSST had all this stuff collapse on it, and it's sitting down here probably in twisted wreckage.

Captain Craig Matthews: Yeah, honestly, it was in a better shape than I would've expected with how much had it collapsed on top of it. It held actually very well. Like I said, there was a couple of spots where it had stretched the corrugation of the CSST and formed some additional mechanical holes, more or less, from that collapse. But overall, the CSST was in relatively good shape. And essentially that was on the floor level on top of some of the remaining non-combustible that were of storage that was still in that crawlspace. But we had an entire floor system where the floor hadn't been consumed. We had furniture from the first floor, all that had collapsed down on top of it.

Rod Ammon: Well, it makes me think about some of the things that we've done in the past with arc mapping for electrical, but it's nice to be able to-

Captain Craig Matthews: It's kind of similar.

Rod Ammon: But it's nice to be able to have the trick of what you guys did, was bringing the water through the line. I bet a lot of electrical guys would like to be able to do that.

Special Agent Adam St. John: Yeah, Rod, one thing I'll add to that real quick, if you don't mind. With a high melting temperature of CSST, those arc holes should survive. We haven't been to a fire yet where the CSST had melted. The melting temperature is in excess of 2000 degrees. So as engineers and investigators that arc hole is there or it should be there if this was something that you think or you suspect happened, so it's worth going out there and looking for it. We talked about putting air to it or in this case water, but I think a lot of investigators, once we think it could be lightning related, we stop there with a good strike net report, which is one of the reasons we're lacking some data on CSST failure. But if we're able to take a look for those holes, and a lot of times it's in the area of heaviest damage because that's where the fire burned the longest, there's a good chance you can find them and really get a well-established origin and cause for that fire, because the CSST just isn't going to melt. So it's worthwhile to take a look.

Rod Ammon: What can you do to render these places safe faster?

Special Agent Adam St. John: So I think from a safety standpoint, there's two different things. So from a firefighting standpoint, after these incidents occur, we want to prioritize shutting down the utilities. We talked about that once this gas starts to flow, there's no circuit breaker for a natural gas system. So it's going to flow continuously until the source of that gas is shut down. So if you're doing your 360, you think it could be a utility fire, turning off that gas is critical. As engineers in the past 30 years since the 1990s when CSST first was introduced into houses and we realized that these lightning induced failures occur, they've been spending a lot of time and effort and money to figure out how do we stop this lightning induced failure, the arc induced failure of CSST. And the first thing that NFPA recommended and the codes recommended was to bond the CSST. So it gives it an efficient path to ground if you have a lightning strike. And as a fire investigator, we want to document the system. So if we have a system that that's bonded and grounded either at the main manifold or at the meter location, it makes these arching events due to lightning less likely. So it's a layer of protection. We've certainly investigated plenty of fires where the system has been grounded and bonded, and these fires still occur. From a safety standpoint, the second thing that engineers do is put in a lightning protection system. So we will put in lightning rods on top of the house trying to give a nice efficient path to ground for this energy so it doesn't ever energize the CSST system in that house. The problem is, if you have an indirect strike, like we had actually a second fire in Howard County recently and energize the CSST system, and we still had multiple holes form in a CSST line within the house between the first floor and the basement, even though this house had a robust lightning protection system. So the biggest takeaway is CSST is used now more than ever. There's over a billion linear feet of this stuff in American structures, primarily houses and we don't have a way to protect these systems absolutely from the effects of lightning or even a household current. If you have a branch line feeding the receptacle that comes into contact with CSST and a breakdown of that installation, we've had fires that occurred in interstitial spaces completely independent of lightning.

Rod Ammon: What do either of you want to say to this audience? And again, this audience may be a little broader than fire investigators this time. So I know we're talking to fire officers, firefighters, claim adjusters, attorneys, are there some things that we missed that you'd like us to cover?

Captain Craig Matthews: I'd just like to reinforce to the fire investigator community that, especially after a weather event has come through, and if they're out to conduct an origin and cause investigation, can't stress enough to make sure that they evaluate the CSST system if there is one located within the structure. We're seeing CSST in single family structures, we're seeing it in multifamily structures, we're seeing it in commercial businesses now. Just one apartment building that comes to mind in Howard County has probably a million miles of CSST run through it. Because again, it's routed to each individual appliance off of one line. So again, just take the time to analyze and evaluate the CSST that may be in the structure. Obviously, if there's no CSST, then they have to look for other ignition sources or means that could have started this fire. But from a firefighter standpoint, I tell all the firefighters in Maryland all the time that after a weather event, they have to do a 360 and get around and get a visual picture of all four sides of that structure. And if they can start at the lowest level possible when they're making entry. Because as Adam kind of spoke about, we're seeing a lot of these structural floor systems get consumed, and these firefighters can go walking on a floor thinking that it's a stable floor and the entire structural components underneath them have been consumed by the fire. We ask them to start at the lowest level possible and work up from there. But I really appreciate you having us today. So thank you very much for having both Adam and I.

Rod Ammon: We're so grateful for your time and for all the thought and work that you have both put into this. Adam, is there anything else you'd like to add?

Special Agent Adam St. John: Yeah, Rod, I think the last thing I'll say is we were really hoping that Woodscape Drive was an isolated incident. And you brought up the similarities between Ball Road and Woodscape, and we realized that we really had to get the word out there. So we appreciate you guys allowing us to do this podcast. And the last thing I'll leave you with is why are we talking about this now more than ever? And with the increased usage of CSST, within every structure that has CSST, you have more of it than you do black pipe because you have a single run going to every appliance. We have more lightning strikes than ever. These lightning strikes are more energetic, so we have more of a chance of having these arc induced failures. The houses are about 70% bigger than they were 20 years ago. So you put all of these variables together and it's just a perfect storm to have more fires and more severe fires and I think we're seeing that. So everything that Craig said about making sure we rule out that interstitial space, but also just having an awareness of this. Frequently during the CFI program we're in now, we have to go to 100 fires. We're all set aside anytime there's a thunderstorm because I know I'm going to go to a lightning fire. And it's something that has, without fail, occur where I'll go to two or three lightning fires somewhere within Maryland every time there's a summer storm. And it's something that we haven't talked a lot about, about firefighters or fire investigators. So please, for firefighters out there, just keep an eye on the weather. If you think it could be a lightning fire, which are pretty predictable at this point, it's something we just want to absolutely rule out. And as fire investigators, if you think it could be a lightning strike and there is CSST, maybe try to take a look for those holes. It is an additional level of work, but it just allows us to track how many of these fires are out there, how and why they're occurring, and really just get better data that's out there. So again, thank you so much for having us here. We look forward to participating in that lightning module for CFITrainer.net. And thank you for your time.

Rod Ammon: This discussion's been eye-opening in so many ways, and I really appreciate you guys bringing the CSST Fire Safety and Investigation lessons learned to our audience. We have some links on this podcast page to more in-depth discussion of CSST and these cases, and we encourage our listeners to review those. Also, our guests today are teaching this material in various venues. So if you're interested in a more extensive look at these CSST issues, check that out.

This podcast and CFITrainer.net are made possible by funding from a fire prevention and safety grant from the Assistance to Firefighters Grant Program administered by FEMA and the US Department of Homeland Security. There's also support from the Bureau of Alcohol, Tobacco, Firearms, and Explosives, and voluntary online donations from CFITrainer.net users and podcast listeners.

Thanks for joining us today on the podcast. Stay safe. We'll see you next month for the IAAI and CFITrainer, I'm Rod Ammon.

Firefighter Dies after Falling Through a Floor at a Large Area Residential Structure Fire – Maryland. Fire Fighter Fatality Investigation and Prevention Program. Centers for Disease Control and Prevention.

ATF Video Timeline LODD Analysis of Firefighter Nathan Flynn | 7005 Woodscape Drive, MD (CSST Fire). Howard County Department of Fire & Rescue.

St. John, Adam. Analysis of the Line of Duty Death of Firefighter Nathan Flynn Utilizing Fire Dynamics Simulator, Fire Testing and Electronic Data Sources. 7005 Woodscape Drive, Howard County, MD. Incident Date: July 23, 2018. Bureau of Alcohol, Tobacco, Firearms and Explosives. U.S. Department of Justice.