How often do firefighters enter burning buildings
Fire protectionDangerous high-rise facades
It is the night of June 13-14, 2017, about an hour after midnight. Behailu Kebede is rudely woken up in his apartment in North Kensington, London. The smoke detector gives an alarm. In his kitchen the man sees bright clouds well up. They seem to come from the refrigerator. Bahailu Kebede grabs his cell phone, wakes his roommates, rushes out of the apartment and dials the emergency number, 999.
"Fire Brigade. Yeah, hello, hi. In the fire is flat 16, Grenfell Tower. Sorry, a fire where?"
Behailu Kebede gives his address and the number of his apartment in the high-rise called Grenfell Tower.
"Yeah, but coming quick please. It's the fourth floor. Right, okay. Quick, quick, quick. They're on their way already. It's burning."
It sounds like a routine fire service. And yet this is the prelude to one of the worst fire disasters in the British Isles: in the early morning hours of June 14th, the entire building will be in flames, 24 floors, 120 apartments. 72 people will lose their lives due to the fire.
The first firefighters arrive at Grenfell Tower just a few minutes after the emergency call. From the outside you can see an orange glow behind a window on the fourth floor. Burning or smoldering lumps fall to the ground. And then everything goes very quickly: after half an hour the fire has reached the roof of the high-rise and is now moving along the side of the building. Finally at half past four the whole tower was on fire.
Similar catastrophe in Germany?
After the disaster, the first questions arose: How did the facade fire come about and why was it able to spread so quickly? The building had only recently been renovated. And so the suspicion quickly fell on the materials that had been used. Combustible materials on the facade. So could such a catastrophe happen again at any time? And what is the situation here in Germany? I would now like to pass this question on to Andreas Ruhs from the Frankfurt am Main fire department. Is a fire like the one at Grenfell Tower possible in Germany?
Andreas Ruhs: No. For Germany you have to clearly deny that. We have had regulations for many years, decades. This is regulated differently in the federal states, but it has been the case for many years or decades that no combustible materials may be used on the outer facade of high-rise buildings.
Arndt Reuning: That was apparently the case in London. A review has shown that there are around 600 other houses with similar defects. That means something like that can be ruled out in Germany or what is the situation here?
Ruhs: In Germany it was said that - at least for the federal state of Hesse - because this is a matter for the federal states and is not centrally regulated by the federal government, the Supreme Building Supervision in Wiesbaden instructed all its departments to have these facades checked again or at least at least to check the file situation, and in individual cases it was certainly looked again. There were also individual cases in the media where upgrading measures were carried out. But I can't really imagine such an intense fire spreading like at Grenfell Tower here. It certainly cannot be ruled out entirely. But honestly, I can't imagine it either.
Reuning: How does it look in Frankfurt: How often does the fire brigade have to go to a high-rise fire?
Ruhs: We very, very rarely go out about a high-rise fire. So these typical fires that you might imagine now, maybe also due to the event in London, we've never seen anything like this before. If there is a fire in a high-rise, it is usually in a high-rise apartment building. And then there are house fires, which are comparable to fires in normal or in smaller buildings. We don't go there with an awful lot more fire engine and actually don't have any other tactical approach than we do with normal events.
Reuning: In other words: Are these also sources of danger that occur in every other residential building?
Ruhs: Well, as I said: the typical fire event in this case is actually the apartment fire. The apartment is on fire. It is extremely rare and I cannot even remember that in an office complex - the very large skyscrapers are usually all used for offices - that a fire event occurs there, which goes beyond the actually affected room.
The stairwell as an isolated escape route
Reuning: Nevertheless, certain fire protection regulations must be observed. What do they look like in Germany for high-rise buildings?
Ruhs: Well, that's exactly why, in my opinion, such tragic events don't happen. So on the one hand, sufficient escape routes must be provided. And you can imagine the structural design as follows: At the moment, even if you are on the 20th, 30th, 40th floor: The moment you have reached the stairwell, then you are actually really safe . We always call it a house-in-house solution, i.e. the stairwell, where the staircase is located, is actually so separated from the rest of the building that you are in the safe area when you have reached it. What you still have very often, especially in the high-rise buildings with an office use: You have a so-called fire alarm system in it, so that a fire is detected incredibly early and also automatically calls the fire brigade, possibly even initiating the evacuation of the building. And in addition, you usually have a sprinkler system, i.e. a system that does not necessarily extinguish the fire selectively, but at least contains it so that the fire brigade can finally fight the fire with little effort.
Reuning: Let's take another look at the materials on the facade. So on the one hand I think there is thermal insulation and there is possibly a facing. Which materials are actually allowed there?
Ruhs: So, in Germany there are very clear rules in high-rise buildings: so-called non-flammable building materials. This can be anything. Stone, concrete, metal. So, metal are mostly the curtain walls with a layer of concrete behind them, but nothing flammable. That is impossible in Germany.
Reuning: Are there additional structural devices to make it more difficult for such a facade fire to spread?
Ruhs: Yes, less of the facade fire than of the so-called flashover. Even in a normal building, if there is a fire on one floor and the flames come out of the window, then there is basically the risk that it will run into the apartment on the floor above. In order to completely rule this out in high-rise buildings, aprons must always be installed - you can usually see them too, they also don't look particularly beautiful architecturally - and, or work with reinforced sprinkler protection, so that you can really prevent flashover. But actually not with regard to facade technology in high-rise buildings. Because, as I said, the default is that the material does not have to be flammable.
Reuning: In Germany, high-rise buildings are higher than 22 meters. What does it look like underneath. There, too, houses have insulation on the facade, for example. Are there similar regulations as for the high-rise buildings.
Ruhs: Flame-retardant building materials may be used on those houses that are not so tall that they fall under the high-rise directive. And then on the one hand there are approval criteria, but above all processing guidelines. So-called fire barriers have to be installed so that the fire does not spread beyond the facade.
Reuning: What is that exactly, a fire bar?
Ruhs: Ultimately, you need the insulation material between every second floor, which is usually polystyrene material, with a non-flammable bar, which is usually a rock wool, so a material that does not take part in fire, you have to insert a circumferential bar out of ten Centimeters high, so that it interrupts the fire transmission.
Reuning: That means polystyrene, which is very probably better known under the brand name Styrofoam, which has to be repeatedly interrupted by non-flammable materials.
Ruhs: Yes exactly.
So much for fire director Andreas Ruhs from the Frankfurt am Main fire department. If you look at the top ten skyscrapers in Germany, you can see that Mainhatten, with its iconic skyline, is right at the front. And so there is also a height rescue group there. These firefighters are trained to rescue people from high-rise buildings. For this they practice several times a year.
And our author Piotr Heller experienced firsthand how such an exercise works.
"In addition to appropriate safety boots, safety trousers and a jacket, our personal protective equipment includes our safety belt. In other words, a complete belt.
Daniel Rademacher is the chief fire chief at the Frankfurt fire brigade, the city with its many high-rise buildings. He is tall and has a beefy stature. You don't immediately see that he is a skilled climber. But it has to be. He works in height rescue and is also an instructor here.
"Then we have our hard hat with protective goggles. We hang in the strap. The ropes are tied in the strap. And that's where we hang."
Main fire chief Daniel Rademacher works for the height rescue of the Frankfurt fire brigade (Piotr Heller / Deutschlandradio)
We climb the stairs of a training building where the firefighters are training for rescue at heights today. It is about 25 feet high. The men tie ropes and practice rescuing a window cleaner. I am also supposed to be abseil today to get a feel for the work of the rescuers.
"This moment over the edge is usually the most exciting one for our guests. When you are ready, we are ready."
"Preferably with your leg so that you don't turn around that often. Yeah, just over it!"
I push myself over the parapet on the roof. "Don't look down!" I think. Two firefighters secure my ropes
"Let go now, you can push your feet a little bit off."
It goes down a few meters, then I come to a window sill
"How does it feel? Not good".
Exactly. One of the attributes of the height rescuers is absolute freedom from vertigo. At that point, that's the feeling that you have to overcome. Slow down! Then just walk down the wall like that.
Once at the bottom, Daniel Radermacher frees me from the seatbelt.
"The trembling of the knees will stop soon."
The height rescue was set up in Frankfurt in the 90s. At that time there was a fire in a skyscraper in Frankfurt Höchst. Various escape routes were blocked. So they came up with new ways to save people from great heights - and not just in fires.
Anyone who wants to work in height rescue must have a head for heights (Piotr Heller)
"If the apartment were on fire now, you can see that the ropes run right by the window, that wouldn't work that way. Keyword melting point, that doesn't fit."
The height rescuers are more likely to be busy rescuing crane operators or window cleaners in the event of an accident. But they could also be an option in the event of a fire.
"There was a fire somewhere, there is a great spread of smoke, escape routes are cut off, in the end we would have to get onto the object in some form, and then we can with our materials from above, we get fixed points, and rope ourselves down to the person and bring them them to the ground. "
First, however, the firefighters try to get to the people in the traditional way. In Frankfurt's skyscrapers this is the fire department elevator.
"It's tucked into a shaft that is specially ventilated, we can control it with a special fire brigade lock. Safety devices are switched off. This is also the light barrier. We can't break the light barrier because smoke is smoke particles. And the light barrier reacts to particles and so that would be bad. "
Back on top of the training building, one of the firefighters rappels down. The height rescuers have 72 such training hours on their program every year.
"You see, the colleague is now climbing over the parapet. We are used to working at such heights, there are 25 meters, I'll say now, no challenge. So from 200 upwards, hanging freely on the rope, that's a different house number then . "
Piotr Heller let himself be abseiled by the higher rescue group of the Frankfurt fire brigade.
Fire spread rapidly
The Grenfell Tower on the night of June 13th to 14th: the first fire engine arrives there just a few minutes after the emergency call. Nevertheless, the flames manage to spread to the roof of the twenty-four-story building in around thirty minutes. Only one hour later does the fire brigade classify the fire as a "major incident". Forty fire engines are on site or on the way at this point. Question to Andreas Ruhs from the Frankfurt Fire Brigade: What options do you have to fight a high-rise fire of such a magnitude?
Andreas Ruhs: In my opinion, honestly, none at all. A fire that spreads so rapidly over all floors, in my personal conviction the fire brigade is simply powerless; also a highly professional fire brigade like the London fire brigade, which is certainly one of the most powerful in the world. But in my personal estimation you cannot get such fire incidents under control.
Arndt Reuning: What are the biggest problems with it? Smoke, heat or completely different factors?
Ruhs: In my opinion, the most likely to happen is this rapid spread of the fire. If the fire is limited to one or two apartments, the fire departments can handle it. That is what they are trained for. We have the necessary know-how and technical support for this. But if you imagine that it really burns from top to bottom in such a high-rise building. And we also have the need for safe attack routes, so that we can actually enter the area with some certainty, if this is possible at all, and secure our way back again. You simply have to be afraid that your hoses will burn away, that you won't be able to give off any more water at the front because of this great intensity.
Evacuated too late?
Reuning: The question of evacuation arises, of course: when do you get people out of the house? Is there a hard and fast rule?
Ruhs: No, there is actually no hard and fast rule. There are also various different tactical approaches. So, to be honest, we usually do it in such a way that we actually deliberately refrain from evacuating everyone, at least in the initial phase, because due to the really intensive requirements in structural fire protection, one can actually rule out an event like in London in this dimension. And we usually focus on the fire floor, the floor below and two floors above and of course otherwise observe what is happening and, as soon as we had the impression that the scenario is spreading further, we would initiate the entire evacuation.
Reuning: That was, I think, a bit of the problem in London that the residents were instructed to stay in the apartment. And then, the allegation is that they started too late to get them out of the apartments.
Ruhs: I honestly can't tell you much about London. I actually only know the newspaper articles. But what I believe must be recorded in its entirety: this situation, how the escape routes were designed there, how the apartments were connected to the stairwell without any fire protection separation - at least that's what the articles say - that actually exists in Germany not like that. As I said at the beginning: as soon as you have entered the stairwell in Germany, even if you are on the twentieth floor, you are actually sufficiently safe from fire and smoke.
So much for fire director Andreas Ruhs.
Weak points: combustible facade elements
The materials used in the facade played a fatal role in the fire in Grenfell Tower. For thermal insulation, this was a foam made from the plastic polyisocyanurate, which is similar to polyurethane. Fire protection expert Luke Bisby, professor at the University of Edinburgh, however, turns his gaze to the panels that had been hung in front of the insulation layer to cover and protect against rain. They were made of polyethylene and thin sheets of aluminum were glued to both sides.The composite material was cut and bent so that the plastic was exposed towards the house wall, Luke Bisby said during the public investigation into the incident.
"Polyethylene is a highly flammable synthetic thermoplastic polymer. Under the influence of heat it melts and drips. And if it drips or flows down it will probably burn."
The flammability of facade materials therefore plays an important role in fire protection. It can be influenced by additives, by flame retardants. My colleague Piotr Heller took a look at what these substances can do.
"The foam, which hangs vertically, is exposed to a flame from below. We will apply a flame to the sample for about 15 seconds."
Benedikt Sperlich is handling a piece of solid polystyrene foam in the laboratory of the Fraunhofer Institute for Structural Durability and System Reliability in Darmstadt.
Michael Ciesielski and Benedikt Sperlich (Piotr Heller / Deutschlandradio)
It's white and about the size of a paperback book. The young scientist hangs it in a test chamber. Such foams were used for insulation in some places. Polymer foam was also built into the facade of the Grenfell Tower.
"At the time of that terrible high-rise fire, it wasn't polystyrene foam, it was a different material, but the principle is comparable."
Explains Michael Ciesielski, who here at the institute develops flame-retardant plastics for house facades, but also for electronic parts. The foam in the test chamber does not contain any flame retardants.
"We'll try to burn it at the bottom and lightly on the front edge, then you can get an idea for yourself without flame protection."
The foam immediately catches fire over the small flame and begins to melt. Burning drops fall down.
"If you imagine it big, you can imagine what it was like with the facade fire, very similar. The material burns off completely, with a huge amount of heat, generates a lot of dark smoke, has no stability whatsoever, there would be on the facade It's actually solid fuel that actually burns like diesel oil. "
Next, Benedikt Sperlich hangs a foam in the test chamber that contains two percent of a bromine-based fire retardant.
"You can see something about the flame protection mechanism. The material retreats, the flame goes out very quickly."
A hole the size of a thumb remains in the white material.
Polystyrene foam with and without flame retardants (Piotr Heller / Deutschlandradio)
Among other things, the flame retardant prevented the formation of highly reactive particles that would have heated the flame. The last step is a test with an in-house development by the institute.
"This is a material that consists of polystyrene, foam particles, it consists of a thermoset resin, there are also large amounts of an inorganic fire retardant and other things in it. It could also be used for higher facades, in the roof area. That would be there wide applicability. "
The flame cannot harm this foam. Only a small, charred layer is created. There are several reasons for this:
"The thermosetting plastic as such is quite flame-retardant. Then there are considerable amounts of aluminum hydroxide in it and that has a considerable flame retardant effect. When aluminum hydroxide changes into aluminum oxide, large amounts of water are released, which removes the energy from the fire process."
In the test, you can see at first glance that this material can withstand a fire much more than the others. In fact, the researchers use this chamber to test new developments for the first time. If they do well here, they will be investigated further. For example, how much heat they release from the combustion and which toxic gases are created.
So much for the insight into the laboratory of the Darmstadt Fraunhofer Institute for Structural Durability and System Reliability.
Significantly reduce the risk of fire
The materials on the facade of Grenfell Tower were apparently burning like tinder. Panels for cladding made of aluminum and polyethylene. I wanted to know from Prof. Manfred Döring, who heads the polymer synthesis department at Fraunhofer LBF, what he thinks of this combination.
Manfred Döring: Yes, it's a little more complicated than that. In the end, as with almost all houses, this is called a thermal insulation composite system. That means that you have an insulating layer - which, by the way, also burned - made of polyurethane foam directly on the wall to the outside. And in front of it a so-called aluminum system was hung. That means it hangs freely on the facade. And, as you rightly said, consists of two panels, which can be called a shell, and a core made of polyethylene. And that's very clumsy because the polyethylene is of course very flammable. That wasn't flame retardant either. And because it is exactly between these aluminum plates, it also works like a chimney. That means that we then have a strongly developed facade fire.
Arndt Reuning: You already mentioned the insulation, which also burned because it was made of polyurethane foam. Should one assume that such foams made of polymers, made of plastics, actually always catch fire?
Döring: That is a difficult question. You can set them so that they hardly burn. Of course, they must be flame-proof in accordance with the relevant regulations. There are guidelines. There are laws as to how this fire behavior of facades should be. And you have to pass that.
Reuning: They apply to high-rise buildings. There is also a difference in Germany: depending on how high the house is, whether it is higher or lower than 22 meters. In any case, below 22 meters you have to deal more clearly with this flammability of polymer foams. I think a very common material is polystyrene, better known under the brand names Styrofoam or Styrofoam. Are there any ways to really build this on houses without the risk of fire?
Döring: Basically, there are the differences: 22 meters high, you can turn polystyrene underneath. It is actually forbidden in Germany. It is installed in Germany today and meets the standards currently in force. That means, if you want to change something, you should primarily change the norms.
Burden on the environment
Reuning: Which flame retardants are there actually? Can you divide them into different classes, for example according to their effect?
Döring: Yes, there are basically three broad classes of flame retardants. One is inorganic hydroxides such as aluminum hydroxide or magnesium hydroxide. These are inherently non-flammable, and if they are exposed to a heat source, they also split off water and extract energy from the flame. Then there are bromine-containing flame retardants. It was very popular, I would say, after World War II until the turn of the millennium. However, it turned out that many of these - not all, but some - were toxicologically questionable and were ultimately withdrawn from the market or replaced by non-toxic ones. Then there is a whole range of phosphorus-containing flame retardants and nitrogen-containing flame rubble, which have very different effects. They can both suffocate the fire in the gas phase, but can also do a kind of surface sealing through carbon infection, known as charing, so that the heat cannot get to the corresponding flame-sensitive materials.
Reuning: You already mentioned the environmental aspects. So, if a building is torn down again at some point, then the insulation material must also be disposed of. And if that is now, so to speak, impregnated with flame retardants, then that should also pose a challenge for disposal or processing. How do you see it
Döring: Well, if someone owns a single-family house and wants to remove the old foam or tear off the house, then he has serious problems with it. Because the old polystyrene foams were contaminated with the so-called HBCD, a brominated flame retardant, which is toxicological according to current knowledge and has also been classified accordingly by the EU, i.e. a chemical substance with high toxicological potential. Logically, these foams or this polystyrene material with this flame retardant are hazardous waste. This means that you should then inquire that these materials are packed in extra sacks that are available from the relevant offices and then disposed of as hazardous waste or that an appropriate company is involved.
Reuning: Are environmentally friendly alternatives currently being developed?
Döring: Yes, the polystyrene foam that is now on the market is firstly provided with a flame retardant, which is toxicologically harmless, so that recycling of this material is also possible without any problems. In addition, halogen-free or bromine-free flame retardants are being developed, but these are used in larger quantities from the start. Also of an inorganic nature in order to achieve higher fire protection classes that are targeted.
Says Prof. Manfred Döring from the Fraunhofer Institute for Structural Durability and System Reliability in Darmstadt. - The fire disaster at Grenfell Tower could have been avoided without any problems. The owner company just had to use non-combustible material on the facade. That is a technical aspect. The roots of the misfortune are likely to go deeper. It is also about the political, economic and social dimensions of the case. Why was social housing in the wealthy part of London neglected, why were warnings from residents not taken seriously? These aspects are therefore also an issue in the public investigation, which is currently ongoing. A first interim report is expected for the end of October.
Statements by our interlocutors reflect their own views. Deutschlandfunk does not adopt statements made by its interlocutors in interviews and discussions as its own.
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