Aug. 24, 2022

064 - Heat stress in fires - from inside and outside with Denise Smith and Gavin Horn

064 - Heat stress in fires - from inside and outside with Denise Smith and Gavin Horn

This amount of heat flux for this amount of time, routine conditions, check, done. This is how I used to do my engineering and tenability assessment related to heat stress... up till today when prof Denisse Smith and prof Gavin Horn took me on a bumpy journey into the physiology of humans in fire conditions and in personal protective equipment (PPE). It is astonishing, that the stress on the body of the firefighter may be as great from the fire as from their own heat generation due to work being done. If you think about it - it is obvious. PPE protects the heat transfer...both ways! You won't heat up, but you cannot really cool down either. 

This is something that every firefighter knows (feels), but why we - fire engineers should think about that? When we design a building, we design it for firefighter accessibility. We provide them with tools to reach the place of fire and begin efficient extinguishing actions. But what if just getting to the place where the fire is, is so physically exhausting, that efficient actions are unlikely to be carried out? Do we ever think that when we design a risky environment on the 30th floor or 5 floors below the ground? Or when our landscrapers have such vast walking distances, that mistaking an entrance may be an error that costs you dozens of minutes? Boy was I uneducated in this regard, and I am really thankful to Denisse and Gavin for teaching me some really important lessons they have learnt through decades of experiments in this field.

If you would like to learn more, you should check out the websites of their respective institutions, as they are filled with great resources on this subject:


[00:00:00] Wojciech Wegrzynski: Hello, everybody. Welcome to the Fire Science Show. Today, I have an episode in which I have learned so much, so I am excited and I know it's going to be. One that's very useful and popular to all of you. I have invited professor Dennise Smith from Service Institute and Skidmore College. And professor Gavin Horn from UL Fire Safety Research institute, the previous guests on the podcast.

[00:00:24] Wojciech Wegrzynski: And I wanted to talk with them about thermal stresses And how humans deal with. Thermal exposures. I thought it's going to be in easy and nice episodes. Really? Really I feel kind of stupid after the episode, but yeah, I felt it was going to be simple. I'm going to ask him what he'd exposures are safe what are not safe well, how long can firefighters work in a scene of fire?

[00:00:49] Wojciech Wegrzynski: To what extent, we should design buildings, having that in mind, you know, the typical engineer questions that come to my mind in a way that I was trained all my life and the [00:01:00] way how I practiced my engineering. These are the things that I thought that are important. And then in the episode, I learned that it's not the most important thing. I mean, it's important, but it's just one part of the giant equation.

[00:01:14] Wojciech Wegrzynski: Of, thermal equilibrium of a firefighter human physiology. And what a hero can take. It's astounding, the level of complexity related to how long firefighters can perform tasks they need to perform and how different tasks. Put different strain on their bodies. And when we start talking about temperatures,

[00:01:37] Wojciech Wegrzynski: It seems that the internal temperatures are as important or maybe at some point even more important than external temperatures. So we put them into their protective gear. And they heat up. As simple as that, the equipment separates them from environment does not let heat in, but also does not let heat and humidity out. So , we are creating them [00:02:00] personal saunas in which they run marathons with their gear on their back while.

[00:02:04] Wojciech Wegrzynski: It is. Amazing. I highly respect firefighters, but. I mean after this episode. This grown exponentially up, the physical strain you guys and girls are going through to save lives is amazing. Anyway, my journey through these episodes, like going. With a state of mind of an engineer and ending in the discussion with a completely different view on the subject. It's really eye opening. And as we design buildings, very complex building, very large buildings, tall buildings, deep underground cow box.

[00:02:40] Wojciech Wegrzynski: Places with low accessibility, where we consider all the tools that firefighters needs from us to release some of the strain on them. You know, the hydrants standpipes. The elevators, all the access routes. When you start thinking about the [00:03:00] physiological exposure of a human body of the body of firefighter.

[00:03:05] Wojciech Wegrzynski: Well, they have to go through. You really start to appreciate why we are designing these tools. So, yeah, it has been the journey for myself and it's a tough episode. But I think it's a much needed one. I have never learned that in my life of a fire engineer. And I feel I should have. So, yeah, please.

[00:03:26] Wojciech Wegrzynski: Accompany me the journey of, my stupid self learning, this important things from legends of this field. I'm sure you will enjoy it. Let's spin the intro and jump into the episode.

[00:03:42] Wojciech Wegrzynski: And that's it. Whoa. It's even hard to summarize it further. Then what I did in the end of the interview itself, the physiological stresses added into the external thermal stresses that firefighters face. I've never considered that. And. [00:04:00] Now, like it's not that I'm going to use my calculations to include for that, but suddenly when I proved my firefighter access,

[00:04:10] Wojciech Wegrzynski: A few meters further than usually, or when I design a standpipe by or where or where I plays in elevator. Or where I tried to design a high-risk building that is very tall. Or deep that this image of, firefighters stresses and this knowledge on what the firefighter has to go through before they even start extinguishing. This is something that's going to stay with me and.

[00:04:37] Wojciech Wegrzynski: I think I'll, I'll consider that in my design. I have to consider that in my design. Now, as I know that. I hope for many of you, it was as eye-opening as for me. And, yeah, be a good friend. Share, share this episode with your colleagues. I mean, it's not an easy episode. It's not a fun episode.

[00:04:55] Wojciech Wegrzynski: Uh, but, uh, I think it's an important one as it contains [00:05:00] a piece of puzzle. That many of us probably does not know. I'm not sure about what your education has taught you. What, what did you go through as. Your fire safety engineering programs, or what have you learned through the years of experience, but I, if you have not dealt with the fire on your own, if you have not ever been in a.

[00:05:23] Wojciech Wegrzynski: PPE fighting fires. I have never been, I have not experienced this. I had no idea and I'm very humble. Say that and very thankful to Denise and Gavin to. teach me that because I would have not known. And it's, it's important. It's. I feel stupid, you know, it's, this things are super important and I have never known.

[00:05:45] Wojciech Wegrzynski: So, yeah, I'm very thankful For learning this in this episode, and I hope that you also got your lesson and enjoy the time spent with me. Denise and Gavin. Anyway, that's it for today's episode. Thank you very much for [00:06:00] listening. Looking forward to next Wednesday and another good episode. I hope.

[00:06:05] Wojciech Wegrzynski: I have some good interviews coming. So. Let's stay in touch and see you here next Wednesday bye