Jan. 28, 2026
236 - Fitting an efficient smoke control system in a confined space
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A tight, historic cellar. Arched ceilings. Long corridors. Tiny shafts. We faced a design wall: to keep routes tenable, we needed twice the extraction that the building could carry. At that point, I've failed as an engineer - I've reached my limit and could not find a solution.
Some time later, a solution appeared in my head from nowhere —what if the fan changed with the fire? Not in a crude on-off way, but by tracking temperature, exploiting density changes, and chasing constant mass flow instead of fixed volume.
We unpack the moment this clicked, the fan physics behind it, and why hotter smoke can actually make extraction easier if you use the margin correctly. You’ll hear how we oversized the fan, ran it at a lower frequency in ambient, then ramped as temperatures rose to keep kilograms per second steady. That adaptive control boosted cubic meters per second right when the layer needed support, eased plug-hole entrainment, and stabilised makeup air velocities. We walk through the thermodynamics, the electrical and pressure implications, and how these pieces form a practical control strategy for retrofits and new builds.
To ground the idea, we share two paths to proof. First, CFD with user-defined control that reads gas temperature each time step and updates fan frequency with smoothed delays to prevent oscillations—capturing the real feedback loop between fire and system. Then, full-scale container burns with live control showed the same trends from 20 to over 500 degrees: falling duct pressures, lower fan power at heat, and the headroom to increase volumetric extraction without breaking limits.
Thinking about it now, this idea is a part of many other concepts that I describe together. To show a way how we come from the simple framework—Smoke Control 1.0 (empirical, static), 2.0 (CFD-informed, still static), into a new smoke control 3.0 (adaptive, feedback-driven)—and explore how this thinking can reshape underground venues, car parks, tunnels, pressurisation, and natural ventilation.
If you care about safer evacuation, smaller shafts, lower velocities, and systems that work with physics rather than against it, this story is for you. Subscribe, share with a colleague who designs smoke control, and leave a review with your toughest question so we can tackle it next.
Reading material:
- Can smoke control become smart?
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The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.
00:00 - Tragedy Context And Setup
03:20 - Partnership And Show Milestones
04:40 - The Underground Venue Challenge
08:20 - Why Traditional Smoke Control Fails
12:20 - The Eureka Moment
16:05 - Fan Physics And Thermodynamics
22:00 - Constant Mass Flow Concept
26:20 - CFD Method And Control Logic
31:50 - Case Studies And Conference Roadblocks
36:20 - Full-Scale Tests And Aftermath
41:00 - Defining Smoke Control 1.0 To 3.0
47:20 - Next Steps And Closing
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Hello everybody, welcome to the Fire Science Show.
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The previous week I've been interviewing Lazaros Felippidis on the fires in underground club venues, music clubs, etc.
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Very difficult episode to record because of the recent tragedy in Switzerland.
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And while during the talk, we were talking about various aspects of fire safety in the underground spaces and in such venues.
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And while we were discussing it, I actually remembered that I had a case study like that in the past, and it's actually a very interesting story for myself, perhaps my pinnacle as a smoke control engineer uh doing buildings, that's years 2017-18-ish, pretty much.
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Back then I I phased a project like that to provide uh fire safety in an underground retrofit venue, and I I failed.
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I could not provide a smoke control system in the venue in a way that I would be happy with it, in a way that I would say that my fire safety engineering goals are met what we've ended up.
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We just told the client, well, you need this much air to extract, and there's no way we can get this much of air extracted in this limited space in those circumstances.
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And that was kind of an engineering failure.
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I was not able to engineer a system for that building, but this stick with me.
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And uh sometime later, I've kind of made a discovery.
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It was quite quite funny to make a discovery, but uh I've made a discovery, and with this discovery I realized I could actually make this system work.
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And you know what?
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We've uh we've done a research paper on that and we've shown that we could have had actually made it work with clever use of fire physics, with clever use of measurement systems, with completely changing the paradigm of how smoke control works worldwide.
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Back then I called it the smart smoke control idea.
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Today it's something I would probably coin as smoke control 3-0.
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And perhaps if you like this, I'll I'll record a larger uh podcast episode on the whole smoke control 3-0 idea.
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But today I would love to share with you my personal story, how I felt as an engineer, how I succeeded as a researcher, as a scientist, and how understanding compartment fire dynamics allowed me to uh do something that was impossible, do something that we thought is not possible within the constraints given, and yet we found a way to fit more smoke through the same deck, pretty much.
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But that that kind of sums up the idea.
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I've shown this in SFP conference in Malaga 2019.
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Uh some time has passed, as I said, it settled down somewhere in the back of my head.
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Lazarus brought it back.
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It's again a fresh idea in my head, it was an important part of my career.
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I would love to share those thoughts with you today.
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So let's spin the intro and jump into the episode.
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Welcome to the Firescience Show.
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My name is Wojciech Wegrzynski, and I will be your host.
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The Fire Science Show podcast is brought to you in partnership with OFR Consultants.
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OFR is the UK's leading independent multi-award-winning fire engineering consultancy with a reputation for delivering innovative safety-driven solutions.
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We've been on this journey together for three years so far, and here it begins the fourth year of collaboration between the Fire Science Show and the OFR.
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So far, we've brought through more than 150 episodes which translate into nearly 150 hours of educational content available, free, accessible all over the planet without any paywalls, advertisement, or hidden agendas.
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This makes me very proud and I am super thankful to OFR for this long-lasting partnership.
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Check their website at OFRConsultants.com.
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And now let's head back to the episode.
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Okay, retrofitting efficient smoke control in historical venues.
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Uh back then I coined this as a smart smoke control solution.
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One of the older professors asked me what's so smart about it, and that's a hell of a difficult question to be answered.
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But in fact, when you discover something new, when you propose something new, there has to be a name for it.
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And back then I thought uh smart smoke control would be very fitting.
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So before I tell you how I discovered something new and how I've succeeded as a scientist, let me tell you how I felt as a fire safety engineer.
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Because uh not being able to deliver fire safety for a project, I consider this a failure of myself.
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Well, uh up to you to judge if I am too harsh or it's justified.
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But uh let's let's talk about the the problem at hand.
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So we were approached by a client who was uh trying to connect two underground cellars in uh in a historical buildings, you know, large cellars that are underneath uh the buildings with quite steep entrances through steep staircases uh inside.
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Uh they consist of multiple smaller rooms uh connected together through some sort of corridors, and some of those rooms that were adjacent to the external facade were actually much deeper than the rest of the buildings.
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They had the ceiling at approximately the same height all over the place, but some of the rooms were significantly taller than other rooms.
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Uh this is because the role of those uh of those spaces.
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Back in the days, you would drop coal from the street level down to those uh rooms.
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Therefore they had some uh little windows that connected to the uh exterior, nothing you could use to smoke control really, but we we could have used them as sources of makeup air.
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We had some limited shafts in the room because there were like literally two small shafts vertical going up all over the building that we could have used.
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Uh we had two staircases, there was a possibility to build a third one, but the investor for them that was a massive, massive problem to uh retrofit the staircase into this layout.
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And in general, it was quite large.
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It was like multiple, I think 20-ish compartments, maybe less, but but quite a lot.
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It was supposed to be a restaurant and a music club.
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Uh, long story short, uh, the law requires smoke control in corridors in Poland.
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The law requires you to provide smoke control when you exceed some evacuation distances, which was the case in here.
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Um, it obviously looked dangerous.
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Like you could take a look at the picture of the layout, the layout is in the paper, and you can tell that this is a very challenging space to uh fire safety engineer around.
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Uh also ah, one more one more interesting caveat was that the compartments they were not rectangular, they the roofs were arched.
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So it was not only just you know limited space, but also the smoke reservoirs were even more uh reduced because of the arch shape of the ceilings.
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In this confined space, it's already difficult to provide smoke control because you don't have smoke reservoir, you need a smoke reservoir to be able to extract the smoke that is produced in the fire.
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If you don't have sufficient smoke reservoir capacity, the layer will descend and it will drop below, let's say, 1.8 meter, which I would consider the minimum value for safe evacuation.
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If it drops, if it drops down below that, there is really little you can provide in terms of smoke control.
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And if the smoke reservoir is not large enough, you you have to compensate with larger smoke extraction capacity.
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But this brings another challenge because if you don't have a big enough layer, you start to have a plug-hole in situation, which means that the smoke control system is extracting not the smoke from the layer, but the clean air from underneath the layer.
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The smoke extraction can be so powerful that it basically sucks the smoke around and starts sucking the cold air from the bottom layer, and that obviously is a systematic failure of the smoke control.
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So you end up with a situation.
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You have a bunch of smaller compartments, they fill with smoke quite quickly, they spill the smoke to neighboring compartments, those neighboring compartments fill up very quickly, they spill the smoke into common corridor, the corridor fills up quickly.
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You end up in a situation that within three to five minutes for a reasonable design fire, your evacuation routes are untenable.
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This is how bad it is.
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You could perhaps do this if you increase the smoke extraction capacity.
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So I think we've started at 10 cubic meters per second, um, as what you could perhaps maximally fit in this space.
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We've ended up uh seeing that at 20 something ish cubic meters per second, you would actually get a performance that that would work with this smoke reservoir.
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But uh this number, me as a fire safety engineer, I come up with a number how much air I want.
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I give this number to the MEP engineer, and then the MEP engineer has a heart attack because there is absolutely no way they can provide me with that.
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Why?
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Because they are limited with space.
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They are limited with space on new projects, because the space is money.
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Every square meter of uh extraction shaft is one less meter you can sell of a building and that stucks up very quickly.
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In historical buildings, they simply don't have space.
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They don't have duct space to to put more ducts in.
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It's it's impossible to fit more ducts in.
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Another challenge is with uh the makeup air.
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We are talking about underground venue.
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So again, I said that there were little windows uh connecting to outside.
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We thought about you know combining those little windows with um uh some ducts to bring the air down to the ground and uh allow for some makeup air situation with them.
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However, the amount of those windows is also limited, and uh as you increase the extraction velocities uh in your ducks, you also increase the inlet velocities and your inlet points.
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And too high inlet velocity is also a big problem in any smoke control design because it will cost mixing of uh smoke, air.
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Basically, you end up with uh a little colder mixture of smoke that is still untenable, still prevents any safe evacuation.
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Nothing you can do about it.
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Also, I probably should have mentioned that uh this venue obviously had no sprinklers in it, and the investor had no intention to bring sprinklers in the venue.
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That was even worse than making additional staircase from the perspective.
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So we end up with those bunch of problems with being unable to fit uh horizontal vertical ducks, being unable to fit a reasonable makeup air strategy for the space.
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In general, a situation in which we know that if we want this venue to be safe, we need twice the amount of air extracted from the venue, then we can realistically maximally provide with the circumstances given.
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That was the limiting factor.
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And also, one more thing which is important later.
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Um, we ended up with ventilators uh for class F600 because the smoke temperature was also extremely, extremely um hot.
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This is how I failed.
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We were not able to engineer a system for this space.
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So that was it for this project.
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We delivered it.
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We're not sure what the client did with it.
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I have no idea what's the follow-up on the project.
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Did they build a venue or not?
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Did they get more air or not?
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No clue.
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I have not done a follow-up on that.
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But from our perspective, this was it.
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This was the end of the project.
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Uh simply unfeasible.
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Uh I've continued my life as an engineer for months or years, and eventually, uh one day, in a very random uh moment, a solution uh came to my head.
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So that day, my colleague from the office, uh Pshamek, he was working on a smooth control project.
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I think it was for a car park.
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I'm pretty sure it was for a car park.
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And Pshamek was uh having the same struggles as I did back then uh in the in the underground venue.
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He needed to extract more air than he could uh extract through the ducts.
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Basically, he found a number at which he was pleased with the smoke control system in the car park, uh, but he only could fit maybe 60% of that number into the ductworks of the building.
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And the investor was very rigid, there was absolutely no way they would allow to increase the size of the vertical shafts in the building.
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Like simply impossible.
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And and and Shemak was really struggling because he would not sign off a project with lower value of smoke extraction because uh this obviously has not met the goals of the analysis.
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Uh and he knew that there is a solution, it just requires more air.
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And he I was his supervisor back then.
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He will I and I was I remember I was sitting at the desk, I was super busy with another project, and he's there nagging me, I cannot fit the air, I need a way to fit more air.
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I uh w what I'm supposed to do with the project.
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And I was in a flow mode uh on another project and I just simply replied to him, Jesus Psemek, just put a larger fan on that duct, and uh when the temperature rises, perhaps you could increase the extraction on it because the losses will will drop.
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So technically, you in the end you could extract your 100% through the duct, which only allows you 60% in ambient.
00:14:45.279 --> 00:14:48.879
And the moment I said that, I don't even know why I said that.
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It it's kind of this Eureka moment, I guess, when people refer to Eureka, uh, you know.
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I I think that that's kind of the feeling.
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I mean when I said that, everything clicked in my head, and I was like, whoa, wait.
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And uh the first thing I did is to call my another colleague, uh Xegosh, who is an expert on smoke control.
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We work together, and I called Xegosh, if we put a larger fan on an extraction duct, and when the smoke increases in temperature, we increase the volumetric capacity of that fan, that's gonna work, right?
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And he's like, Yeah, I think it's gonna work.
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And I was like, wow, this is like a confirmation.
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I went from not having an idea in my head into into a really clever solution within like m two, three minutes.
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That was like really interesting feeling, uh, you know, when when things click in your head.
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If you don't get why I uh say this is uh a wow moment, uh I'll explain to you in the details because there is a bunch of uh thermodynamics that go into that and and a bunch of history of uh how smoke extraction systems are being designed and then tested that go into that.
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But uh that moment I knew that the world of smoke control has uh has changed of me like with a click of a button.
00:16:09.519 --> 00:16:25.120
So to explain why this works, uh why this changes everything, I have to take you through um kind of a history of a fire in a compartment uh from the perspective of thermodynamics and and uh fluids and heat transfer.
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Uh, what happens in a compartment where you have mechanical ventilation in it to various characteristics of a fire?
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In my paper from 2017, I uh present this as a nice uh matrix of nine plots of various properties uh of compartment physics that change with with time as the fire grows.
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I'll try to explain this in uh spoken content, but wow, this is this is a challenge.
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Um anyway.
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Imagine you have a fairly small compartment, let's say it's 10 by 5 meters, 3 meters tall.
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Maybe not the smallest compartment, but it's it's a small compartment in which you can have a mechanical extraction from with a duct and a set of extraction grills.
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Uh those ducts obviously connect to some extraction fan somewhere further in the building to that space.
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You provide some makeup air through mechanical or natural means.
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So there is, let's say, a fan that pushes some air back to the room, there is an open door to that room through which you can suck air from outside.
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Now imagine a fire starts in that compartment.
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So you you have a fire growth uh which we are used to.
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We would usually define it with some quadratic uh function, you can have linear functions of fire growth, uh whatever you choose to define your heat release rate as a function of time.
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Usually the presumption is that the fire will develop, it will grow to some certain stage, limited by ventilation, by fuel, by other things, uh, and eventually it's gonna start decaying.
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As the fire is growing, what's happening in your smoke layer is that the hot air and smoke produced by the fire is entraining a cold air from surroundings, basically creating a large amount of smoke, which is basically your air with some fire products in it.
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And this smoke starts to feel the uh reservoir underneath the ceiling.
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Uh, the amount of smoke produced will follow the growth of the fire.
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So, of course, the higher the heat release rate, the more smoke you're gonna produce.
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It's not a linear relationship, there's a power low.
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We call those power lows the axisymmetric smoke plume models, and I had a whole podcast episode about them, uh, I think.
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Uh, as your fire grows, as you have more smoke produced in the plume, also the temperature of the smoke in the room changes.
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So this changes also in a power law, it goes a little different than increase of mass of smoke produced, but basically you get a very rapid early growth of the temperatures of the smoke, and then the temperature stabilizes at some point.
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If you reach a steady state where you have a certain amount of megawatts produced in your room, those uh properties will technically stabilize.
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So for a certain amount of megawatts at a certain layer height, you will produce the same amount of smoke, and the temperature will eventually reach some sort of state of equilibrium in the compartment.
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So basically, as fire grows, you get more smoke and it becomes hotter.
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That's very easy.
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Now, as I mentioned, you have an extraction in that room.
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You have your traditional mechanical smoke extraction system fit in that room, which means that the fire is detected.
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The building knows that it has to start the extraction, so dumpers open promote the flow of smoke.
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From that particular compartment that we try to extract the smoke from, a fan starts to operate and it starts sucking the hot gases from the compartment.
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Now, the fan is a machine which basically rotates the impeller of its own following the changes of alternating current that flows through coils which are in the engine.
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Depending on how many coils you have and how you set them up, you will reach a different kind of rotational velocity RPMs based on the frequency of the alternative current that you supply with it.
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In Poland we would use 50 Hz alternating current, which translates into rotational speeds of 960, 1500 or 3000 RPMs.
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I think those are the default values for 50 Hz that we usually get in here.
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Regardless, you supply power to the fan, so the fan turns around.
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It spins at the same velocity all the time because the velocity of the spinning of the fan is dictated not by the contents of what's transferring through the fan, but it depends on the frequency of the alternating current that you supply to the fan.
00:21:14.319 --> 00:21:16.960
So it spins all the time the same thing.
00:21:16.960 --> 00:21:20.319
The characteristic of the blades of the fan, they do not change.
00:21:20.319 --> 00:21:26.240
Technically, there are fans which can change them, but normally they do not change as the fire progresses.
00:21:26.240 --> 00:21:47.440
So basically, from the moment you start your fan till the end of the fire, this the fan is supposed to spin the same way with the same velocity each time the blade sweeps the same amount of air and uh as it works, it extracts the same volume of air with every spin.
00:21:47.440 --> 00:21:58.799
This is important, this is the most important thing in it in this design, that every time uh an impeller rotates, the same amount of air is transferred through the fan.
00:21:58.799 --> 00:22:03.200
Therefore, the fan operates at constant volumetric capacity.
00:22:03.200 --> 00:22:14.000
The volumetric capacity of the fan is not changing with the changes of temperature of the smoke or any other uh measures that happen beyond the fan.
00:22:14.000 --> 00:22:18.400
The fan is dictated only by the power supply and it always provides the same.
00:22:18.400 --> 00:22:28.720
And I know that I I knew that that's the thing why this Eureka moment happened to me in particular, because I am also someone responsible for testing those fans.
00:22:28.720 --> 00:22:34.000
I run fire tests, I'm personally responsible in my laboratory.
00:22:34.000 --> 00:22:36.000
I am the person who tests the fans.
00:22:36.000 --> 00:22:37.359
This is my responsibility.
00:22:37.359 --> 00:22:56.640
And I I've tested like I don't know 40 of them in high temperatures on that on the furnace, and you even have a feature in EN12101 Part 3 standard that tells you you can measure this volumetric capacity and you should prove that the volumetric capacity has not fallen less than 10%.
00:22:56.640 --> 00:23:03.519
So it this fact that the van is a volumetric machine, always has a volumetric capacity which is steady.
00:23:03.519 --> 00:23:09.440
You you even have to there's even a point in the standard that says that that because you have to check it.
00:23:09.440 --> 00:23:15.359
So that's how I know that they work like this, and that's why I was so sure that they work like this.
00:23:15.359 --> 00:23:17.920
Now, this is the volumetric capacity.
00:23:17.920 --> 00:23:20.079
But what about the mass flow?
00:23:20.079 --> 00:23:24.559
The the kilograms per second, not cubic meters per second, but kilograms per second.
00:23:24.559 --> 00:23:30.160
Because the temperature is increasing in your compartment, the air density is dropping.
00:23:30.160 --> 00:23:42.559
So, you know, the air at uh ambient will have something around 1.2 kilogram per cubic meter density, but when you hit it up to let's say 300 degrees, this density falls by by a half.
00:23:42.559 --> 00:23:47.599
If I'm not wrong, it's 0.6 kilograms per cubic meter of air at 300 degrees.
00:23:47.599 --> 00:23:50.799
So the density of the air sharply decreases.
00:23:50.799 --> 00:24:00.319
You are extracting the same volumetric capacity, therefore, what's happening is that the mass flow through that fan decreases.
00:24:00.319 --> 00:24:11.440
You are extracting the same amount of cubic meters per second, but you're extracting less and less kilograms per second through a system because of the changes in density of the hot smoke.
00:24:11.440 --> 00:24:18.160
Now let's look at the um properties inside the ductwork and what happens to the fan.
00:24:18.160 --> 00:24:29.839
Because you are extracting less dense air, the air is lighter than in ambient because it's hot, it has less density, the pressures in your shafts fall down.
00:24:29.839 --> 00:24:33.359
You observe that in the in the fire testing of fans as well.
00:24:33.359 --> 00:24:42.559
You very quickly observe a sharp drop in pressure in all the ductworks in the test as soon as you start the furnace and increase the temperature of the smoke.
00:24:42.559 --> 00:24:45.599
Uh, that's a consequence of the change in density of air.
00:24:45.599 --> 00:24:53.039
And again, the standard tells you how to adjust that to the ambient density and how to measure that during an experiment.
00:24:53.039 --> 00:25:00.400
I've observed this countless times that if you if you increase the temperatures, the the pressures in the shafts decline.
00:25:00.400 --> 00:25:03.200
And uh what happens to the to the fan?
00:25:03.200 --> 00:25:20.720
As I said, the the rotational speed of the fan is dictated by the frequency of your electricity, alternating current, not by the uh circumstances in which the fan operates, but those circumstances make it easier for the fan to work.
00:25:20.720 --> 00:25:38.319
The fan has to push less kilograms per second through its body, which means it has to do less work with uh extracting that, which means that the power supply required by the fan also sharply drops following the increase of temperature and decrease in density.
00:25:38.319 --> 00:25:42.319
And again, it's something we see in fire testing of fans.
00:25:42.319 --> 00:25:47.759
It's very, very normal that you observe this when you test fans in high temperatures.
00:25:47.759 --> 00:25:49.200
Now, where's the discovery?
00:25:49.200 --> 00:25:50.079
What does it mean?
00:25:50.079 --> 00:25:59.680
As you see, the volumetric flow of your extraction fan, this remains constant over the operation of the system.
00:25:59.680 --> 00:26:06.960
The mass flow falls down, the pressures fall down, the power required by the fan falls down.
00:26:06.960 --> 00:26:20.319
To me, those drops in pressure and that drop in electrical power needed by the fan is my margin of operation that I could actually put to work.
00:26:20.319 --> 00:26:28.720
Because you see, my ductwork was, let's say, designed to handle 500 Pascal uh under pressure.
00:26:28.720 --> 00:26:38.480
I could provide 30 kilowatts to the fan, and suddenly my pressures is like 300 Pascal in high temperature, and my fan only takes 15 kilowatts.
00:26:38.480 --> 00:26:42.079
This means I could actually deliver more to the fan.
00:26:42.079 --> 00:26:45.119
And that was the basis of my discovery.
00:26:45.119 --> 00:27:02.319
That basically, if I have started not with my fan that that operates to the point in ambient temperature, so let's say I need 10 cubic meters per second, I put therefore a 10 cubic per meters per second uh fan in in my system.
00:27:02.319 --> 00:27:12.319
If instead of that, instead of that 10 cubic meter per second fan, I've placed a 20 cubic meter per second fan on the same DACTWork, interesting things happen.
00:27:12.319 --> 00:27:33.759
Obviously, I cannot start a 20 cubic meter per second fan on the DACTWork that's uh meant to carry 10 cubic meters per second because I'm gonna create two huge underpressures, I'm I'm probably gonna destroy some things, the electrical um needs for that fan will be tremendous, and I'm not gonna be able to supply this fan with electricity.
00:27:33.759 --> 00:27:44.480
But in normal conditions, I could operate that fan at lower frequency because the frequency of alternating current is what defines the capacity of the fan.
00:27:44.480 --> 00:27:51.119
You know, the frequency defines how fast the blades spin and that defines how much air I extract.
00:27:51.119 --> 00:28:01.119
So I can put a frequency inverter that changes the frequency, and instead of operating the fan at 50 Hz, I can operate it at 30 Hz, for example, in my normal conditions.
00:28:01.119 --> 00:28:12.400
So my fan now is a fan that theoretically could have uh the capacity of 20 cubic meters per second, but works at 10, and that is ambient mode of operation.
00:28:12.400 --> 00:28:41.119
When the fire happens and the temperatures increase, I can use some sort of device like a thermocouple, or there are other devices that you could use to track that, but you can use a device to track the change in of the temperature of the smoke that you extract, and you see that the temperature is increasing, therefore the density is decreasing, therefore I can safely increase the frequency of the fan to extract more volume.
00:28:41.119 --> 00:28:59.119
And what you end up, what is the dream state of operation, is that instead of extracting the constant amount of meters per second, instead of constant volumetric capacity, you start to work at constant mass flow rates on the fan.
00:28:59.119 --> 00:29:23.920
You try to increase or decrease the momentary performance of the fan in such a way that every single second you remove the same amount of kilograms of hot gases, regardless of their density, which in the end means you start to extract different amounts of uh volume of smoke from your compartment, and this is the profound change.
00:29:23.920 --> 00:29:36.400
Because suddenly, instead of extracting 10 cubic meters per second in the compartment of the fire where I am worried with the smoke filling up my room, I start to extract 20.
00:29:36.400 --> 00:29:51.599
And this 20 means that suddenly my inefficient smoke reservoir, my not working solution for an underground cellar in a retrofit building, suddenly I have the amount of extraction air that I wanted.
00:29:51.599 --> 00:29:59.359
And the best part, if you think about the makeup error, the makeup error is applied in an ambient condition.
00:29:59.359 --> 00:30:08.000
So basically, you're always uh submitting the same amount of kilograms per second and the same amount of cubic meters per second into the room.
00:30:08.000 --> 00:30:14.000
However, the balance within the compartment is based on mass flow rates.
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