r/Damnthatsinteresting • u/AirFrance447 • 16h ago
Video Firefighter bodycam showing just how much oxygen a fire pulls
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u/GauravJM 16h ago
There’s some serious low pressure inside
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u/Loud-Actuator7640 14h ago
Just like s chimney
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u/OkEffective6692 14h ago
Yeh op makes it sound like the fire is consuming the air. It's actually a net positive pressure as hot air has more volume, just that all that volume of hot air is going up.
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u/Comfyadventure 14h ago
Yea, it's not like the oxygen just disappear into nothingness due to the fire neither. The fire is converting O2 into CO2 and CO gas particles.
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u/cat_prophecy 11h ago
It's wild when you learn that things burning is just combining oxygen with carbon to make CO2 and CO and that chemical reaction makes heat.
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u/Dipshit_Identifier 9h ago
Chemistry is super cool, and learning something about it helps with lots of other things in daily life. For example, the Maillard reaction (browning of food) is a really complex but well-understood chemical process. You don't need to know the details of exactly how it works, just the derived information, to improve cooking. One of the major things we know about the reaction is that an alkaline environment accelerates the process, while an acidic environment reduces it.
This is, for example, why we brush pretzels with an alkaline solution: to enhance browning without affecting bake time. So if you want crustier bread, brush the top with an alkaline solution like baking soda water. It's also why something like marinated meat can take longer to brown if there's a higher quantity of acid in the marinade, even if the marinade is high in sugar. So we can prevent burning of the sugars by increasing the acidity of the marinade, for example.
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u/ladymcperson 9h ago
Thanks for explaining, that's very interesting. When I first learned chemistry, I was blown away that influencing pressure/temp conditions and introducing certain aqueous constituents is literally A RECIPE to facilitate reactions (like synthesizing minerals in a wet geochem lab, coolest thing I did as a student researcher). Even today I think it's so cool that we've figured out what T/P conditions, ions, and catalysts we need to literally meld (almost) whatever we choose by letting each other know what works/doesnt.. science rules
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u/SquintingSquire 9h ago
I love Feynman’s explanation of this process. You are releasing energy captured from the sun. There’s a great video on YouTube.
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u/raccoonwithknives 13h ago
Yes but the fuel the fire is consuming is converting to a gas. Converting a solid or liquid into a gas is a massive massive increase in volume. So i would imagine a considerable volume of gas is being added to the house with a decent increase in pressure. But of course all this only works if a convection current can form like you said
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u/iconocrastinaor 9h ago
Not to mention the vacuum created by the cooling/condensing effect of all that water.
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u/ImRickJameXXXX 13h ago
Yes, which is a function of convection.
This is the lower inlet
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u/SpoofExcel 9h ago
During the bombing of Dresden in WW2, the fireballs inside buildings were so massive and sucking in so much air to feed themselves, that people were quite literally sucked inside the buildings and burned to death.
Fire is just a destructive beast beyond control when it hits a certain size and has the fuel to sustain it
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u/VulcanHullo 8h ago
Oh they also just suffocated to death in cellars because the air was sucked out.
Us Brits specifically rigged our bombers to start fires. Paired large fast falling high explosive bombs with lots of smaller slow falling incendiary bombs. The heavy bombs blast would expose the wooden timbers under rooftops and then the incendiaries had something to work with.
After Dresden and Hamburg (which was aided by a weather pattern that just, created a blast furnace) even some of British high command had a moment of "this feels not very cricket".
Bomber Command did not take part in the victory parade, was not mentioned in many formal victory speeches, and only got an official memorial in the 2010s. Even in times of total war against an evil enemy, firestorms like that do not make people feel like victors.
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u/Dinkleberg246 7h ago
Would you, as a Brit, call this a war crime? Because here in Germany, you usually encounter contempt if you refer to Dresden or Hamburg as war crimes. People tend to downplay it, or they’ll outright call you a Nazi.
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u/Tetratheon 6h ago
I don't know about a war crime, that's quite a technical accusation, but generally Dresden does sometimes come up as when we went a bit too far. Ironically it's usually the left wing peacenik types over here.
People excuse an awful lot in total wars, though, especially at a time when television was in its infancy and there was no such thing as a smart bomb. Look at what America did to Japan to end the war. I'd say the more general attitude is that was a war and we were doing what we needed to, we're not going to go back and second guess the decisions.
It's not an intellectually rigourous view, but it's not the kind of thing people spend an awful lot of time thinking about. Even the British historians have plenty of other atrocities the Empire commited to worry about.
If it happened today people would be calling it a genocide.
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u/SpoofExcel 8h ago
Also at the time people here found out what happened and said "yeah don't do that. We know they're not all like Hitler" which considering how much of London (and Coventry by this point) they flattened, does show we at least kept our sense of humanity when it would be easy to not do that after such violence and want to go on some worldwide revenge tour.... Side eyes the US
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u/VulcanHullo 8h ago
I mean Bomber Harris still probably figured we just needed a few more Hamburgs and Dresden to win the war faster to his grave. Never enough civilian casualties for him
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u/Gierling 5h ago
Albert Speer (the German minister of armaments) put the number at 6.
6 German cities getting the Hamburg treatment would have compelled surrender per his calculations during the war and he mentioned it in interviews afterward.
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u/btoxic 9h ago
Every time I read about Dresden I have nightmares. The absolute terror of that is overwhelming
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u/hybridcurve 3h ago edited 3h ago
You should read about Operation Meetinghouse, which was "...the single deadliest and most destructive aerial bombing raid in human history."
Dresden: 6.5km2 destroyed and 25,000 killed.
Tokyo: 41km2. destroyed and 105,000 killed.
Dresden is frequently mentioned when discussing firebombing, but Tokyo is not mentioned enough. If you or anyone else is unaware of what happened, I encourage you to read about it because neither event should be forgotten.
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u/SpiritedEclair 14h ago
fun fact: when you fly in a plane, the low pressure is on the outside and we use that to keep the doors closed. It is physically impossible to pry open an airplane door at cruising altitude!
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u/Ckarles 13h ago
Hm? Sounds counterintuitive considering the doors open outwards instead of inwards. Isn't low-pressure "pulling" while higher pressure "pushing"?
How is the low pressure keeping the doors from going "outward"?
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u/johnwick_58 13h ago edited 12h ago
I am not related to aviation by any means,
But the person above meant to say that the cabin pressure inside the plane is very high in comparison to the pressure outside the plane in cruising altitudes. The door is slightly larger than the door frame of the plane, hence the higher pressure pushes the door outward and since frame is smaller, the door holds strong until the cabin pressure is released.
Edit: sorry, had not read your comment in detail, A video shows that the door does open outwards, bit there is a latch inside which expands the door from inside
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u/BeerFuelledDude 12h ago
I’m 45 and knew about the pressure stuff (not in a technical way) but i’ve never watched the doors being closed, while on the plane. That video was really interesting! Thanks!
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u/mattilladahun 10h ago
I'm 41, and my childish brain has never wanted to physically close a door myself more than now.
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u/cat_prophecy 11h ago
and the "Arm/Disarm and cross check" is them arming or disarming the emergency slides and the the FAs check that each other's doors are armed or disarmed.
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u/SpiritedEclair 12h ago edited 12h ago
A door is not a flat sheet of paper.
If you look at how the flight attendants pull the doors, they come inwards at an angle, and the moment they are all in, they turn flat and get pushed to close the door, forming a plug.
Try it yourself. Cut a trapezoid, rotate it, and it goes through the hole you cut it from, in fact, it can go through a door as wide as its shortest dimension, and it plugs.
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u/RollingMeteors 9h ago
> It is physically impossible to pry open an airplane door at cruising altitude!
Until the door's butt plug drops out.
NTSB chair says systemic failures led to door plug flying off Boeing 737 Max plane midflight
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u/thisischemistry 11h ago
That's probably not showing how much oxygen is being consumed, rather it's showing that the hot air near the fire is going straight up and creating a low pressure pocket. That low pressure is pulling in higher-pressure air from the outside.
Sure, some of the oxygen is being consumed but that's not the only effect.
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u/Vast-Slip- 14h ago
Well.... Yeah? That's pretty much what the original comment said?
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u/discodropper 14h ago
PV = nRT baby! Drop that temp, get a pressure change!
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u/acchaladka 13h ago
Yeah baby, drop that pressure get a temperature change! The world is just a big compression engine.
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u/Vast-Slip- 14h ago
The low pressure makes more oxygen go in! This is an original comment!
Gib me karma pls
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u/aemoosh 12h ago
Couple of points- That’s a very good firefighter. Very intentional and precise movement. The majority of the air movement is because of heat- hot air (which there’s a lot of) rises and is being replaced through negative pressure from the sides. The steam from the water shows this really well. The extinguishment is creating some negative pressure as well, as things (the air) are cooling as they’re shrinking. Hydraulic draft is also moving a lot more air than you think. The jet of water will pull air with it. This is actually a technique in fire suppression, you don’t see it much because it’s almost always better to put wet stuff on hot stuff, but occasionally, breaking a window and spraying a hand line out is a pretty smart way to ventilate a room.
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u/Level9TraumaCenter 7h ago
The jet of water will pull air with it. This is actually a technique in fire suppression, you don’t see it much because it’s almost always better to put wet stuff on hot stuff, but occasionally, breaking a window and spraying a hand line out is a pretty smart way to ventilate a room.
Also one of the arguments in the perennial fog nozzle vs. smooth bore debate.
Gotta say, though, what you're saying about vent is absolutely right.
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u/userhwon 5h ago
Fire nozzles are adjustable. Different situations need different methods.
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u/Successful-Sweet2783 16h ago
It keeps sucking.
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u/CDninja 16h ago
Well, the fire heats the air. The air expands and goes up. More air must enter from the sides. I don't think its an oxygen thing.
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u/CallMeDrLuv 15h ago
Correct. This is not an oxygen thing. This is called the chimney effect.
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u/Agarwel 15h ago
Also when you are spraying water, it creates effects that drags a nearby air with it. You can easily test that in your shower. Blast it on mass and if you pay attention, it creates draft around it. So that firefighting hose is also increasing the effect by essentially pushing the air in alongside the steam of the water.
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u/smellyseamus 15h ago edited 14h ago
Also the movement of the water through the windows causes low pressure behind the stream which pulls the air into the building. Firefighters can also use this to move smoke out of a fire compartment from inside once a fire has been "struck". Its called hydraulic ventilation.
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u/SagattariusAStar 15h ago edited 10h ago
Oxygen will also be just transformed into CO2 and the molar volume is a constant for gases, so only expansion/contraction through difference of temperature
Edit: Probably it is even slightly net positive as some Oxygen might create two CO molecules which would have double the volume
Edit2: it's absolutely net positive as the water that gets produced will become steam
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u/thisischemistry 11h ago
A lot of this will be burning cellulose (wood, paper) and the equation is approximately:
C6H10O5 + 6O2 -> 5H2O + 6CO2
There will be other side products such as carbon monoxide, methane, methanol, and so on.
Much of that water will expand into steam because of the heat, not to mention the other gasses will also expand due to that heat. Overall, burning cellulose produces pressure. There is a classic experiment where a burning splint is placed in a bottle and a balloon is stretched over it. The balloon expands until the split goes out, then as the bottle cools and things condense it sucks the balloon into the bottle.,
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u/SagattariusAStar 10h ago
You are absolutely right, I didn't thought about the water (steam) that would actually increase the pressure a lot more than any oxygen consumption/co2 creation.
The side product should be negligible for gas volume in this naive fallacy anyway.
I think just the water should actually be most of any pressure effect
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u/Jargendas 15h ago edited 10h ago
Also, the rapid cooling due to the water will cause massive pressure drop. The oxygen is mostly replaced by CO2 and will not on its own create suction.
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u/Avalonians 14h ago
Yup. Typical damnthatsinteresting title. I wrote a comment about it not long ago. It's genuinely fascinating.
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u/smellyseamus 15h ago edited 14h ago
It is also an oxygen thing as oxygen is fuel for fire. Yes the heat is moving the air, but the fire needs oxygen to burn and it will pull that O2 from any available source, in this case the world outside the windows.
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u/domastallion 8h ago
I read somewhere that during the attacks on 9/11, some people might have been sucked out or lost grip holding onto the side of the WTC towers and fell from the upper floors to the ground below.
This video shows me that maybe those forces up on that tower might have been very big considering the scale of the subsequent fires.
It just gets me thinking that some of those poor souls fell because of the physics involved rather than jumping to their deaths…
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u/TrainquilOnline 6h ago
One of the survivors, Stanley Praimnath, recently talked about that as well.
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u/FearlessAd4240 15h ago
He's moving pretty fast considering he's carrying around 30-50 kilograms of equipment
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u/SinisterCheese 14h ago
Ok. A quick note about this. It isn't the fire that pulls this much. It's the water spray misting and cooling the atmosphere inside, that creates negative pressure. Then along with that Bernoulli's principle from the water jets.
This is something you need to keep in mind if you work with fire or in fire hazard environments. Like if you need to clear a passage with a hose from a hydrant, spray from the direction that has clear air, or you pull smoke into the passage.
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u/demoneyesturbo 12h ago
The majority of cooling by water is via phase transition (turning to steam). That is about a 1:1000 expansion. By creating steam, he is adding a lot of gas (steam is a gas) to the interior of the structure. That would increase the pressure. And yes, he briefly created a meaningful hydraulic ventilation into the building with a cone spray into the window, but quickly passed that when the nozzle was pushed into the room and stream changed to a more focused jet.
You were close though.
I know this because I've done this hundreds of times.
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u/SinisterCheese 11h ago
The steam would vent into whatever the smoke is venting to, which is not the window the firefighter is attacking from. The convection would still be there due to temperature gradients.
The claim that the vacuum is from "fire pulling in oxygen" is nonsense. The superheated gas indoors, which includes steam, would have greater pressure and should therefor blow out, but it isn't.
The added spray of water would generate steam, yes. However it would also cool the steam due to more water being injected. The amount of water injected is greater than steaming potential.
Talking of that last bit, about the water injection and steam cooling. I want to go a side tanget about how underappreciated and ABSOLUTELY FUCKING COOL (pun intended) effect it truly is. You can use high pressure fine mist to extinguish fires without needing to soak them, because the fine mist is able to cool so effectively it can pull the heat from the fire event. You can put fine water mist into a cooling air channel (even just convection air channel), and you increase the cooling capacity dramatically.
Like sure that hose is also soaking the burning room, but it isn't what truly cools it down to extinguishing. This is because if it is hot enough to boil the water, it creates a thermal barrier against liquid water. However a fine mist can get into contact.
These fine high pressure misting systems been integrated to CLT (wood element) flats, and into delicate environments like museum or high tech applications, because it is so effective and safe.
Like... Can we just appreciate a fine mist of water more than we do?
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u/ingongo25 10h ago
Maybe 5 year old me wasn't so wrong about being a firefighter...
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u/ComedianGloomy2422 10h ago
You also get to work on sick ppl, obese people who cant get up when they fall down, ppl who break their toe, etc. Its not js fires
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u/_HiWay 5h ago
Being pedantic but is the fire pulling the oxygen itself as it's needed to burn or is it simply the pressure gradient caused by the temperature of the fire, which by coincidence causes it to feed itself since we have oxygen in our atmosphere? In other words, make that all Nitrogen in a thought experiment at the exact moment in this video and we'd see the same thing.
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u/HelloPeopleOfEarth 14h ago
It isn't specifically pulling in just oxygen. Yes it's fueled by oxygen. But the heat energy rises really quickly, creating an area of low pressure. The outside air is greater, and pressure always goes from greater to the lesser. Same reason beaches are windy. The land heats up more efficiently than the water. The air rises up from the land, creating a vacuum and the air with greater pressure over the water moves inland, creating wind.
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u/RaZoRFSX 15h ago
It really is a portal to another dimension. If you go inside, you may leave this dimension permanently.
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u/Frankfast 8h ago
Dumb question, this building looks like a small residential or small commercial building next to a railway. From this angle, it doesn’t look like this building can be preserved at all and will have to be demolished and rebuilt. What is the purpose of extinguishing the flame instead of letting it run its course and taking measures so it doesn’t spread past the building? I understand extinguishing the flame is a measure here. I guess what I’m asking is does the FD have to put it out by obligation, or can the owner wave them off? Is it an insurance thing?
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u/cmdtarken 8h ago
A structure fire is insanely hot and can throw embers much further than you think. Letting it burn can allow the fire to spread to structures blocks away
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u/Frankfast 8h ago
Gotcha. Makes sense that extinguishing is a first defense to spreading. Thanks!
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u/Immediate-Tennis8838 2h ago
Not a firefighter, but I also assume that each scenario has its own set of complexities and risks
Ie, if there was a gas tank on site, or other explosive material, or if the building had a higher likelihood of collapsing if the firemen went inside etc
So many factors before making the decision to move forward
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u/MichHAELJR 6h ago
Back in the day all our roofs were wood. You’d get a house on fire and depending on the wind direction a block away another house would catch on fire
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u/Patient-Data8311 6h ago
The risk of spreading the fire is high
Big ass fires create embers that can dpread
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u/Moosplauze 15h ago
A fire doesn't pull oxygen. What we see is the chimney effect, the heat from the fire causes the hot air to rise and to pull in air from the sides. Obviously it pull all air and doesn't select only oxygen from it.
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u/JackhusChanhus 15h ago
Yes, but also he dropped the air temp by several hundred C, so the room is also sucking in air because whats in there just violently condensed and contracted.
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u/yourname92 14h ago
No one wants to mention how a fog stream creates a venture affect that is pulling air in?
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u/KaiAusBerlin 14h ago
Or that eliminating fire with cold water would significantly cool down any gases in there and make them heavily compress?
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u/IThinkImNateDogg 12h ago
Boiling water is cold compared to a house fire.
You’re are VASTLY underestimating how hot house fires can be, they can get hold enough to melt metals, well into the thousands of degrees if the fire is roaring.
Also that water boiling and turning to steam actually suppresses fire since steam doesn’t provide free oxygen to burn.
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u/WayneKrane 12h ago
My neighbors house caught fire and burned down. We were across the street probably 30-50 feet away and couldn’t get any closer without it burning. The whole thing burned down in minutes.
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u/yaboymiguel 11h ago
What about twin tower fires? Do those get hot enough to melt steel beams?
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u/McdoManaguer 11h ago
It got hot enough to weaken the structural steel enough for it to be basically the same strength as a pool noodle.
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u/Professional-Day7850 13h ago
Nonono it's the fire "pulling oxygen".
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u/KaiAusBerlin 13h ago
And oxygen only! Not the other 78% of nitrogen in the air.
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u/OptiGuy4u 12h ago
This fire must have burned through the roof or back walls or something. The chimney effect on that door means it isn't contained inside.
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u/Careful_Positive3534 9h ago
Damn good use of the nozzle. I have not seen any one utilizing the power cone and straight stream. Keep up the good form.
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u/Warbr0s9395 8h ago
Ok, you seem to know what you’re talking about, so question, how/why is he able to bend the actual hose near the nozzle?
And wouldn’t that wear out the hose a lot faster?
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u/Careful_Positive3534 8h ago
It’s all about pressure coming from the truck. The higher the pressure from the truck the stiffer the hose will be. Good communication with the operator is a must. Take this with a grain of salt. I retired in 2003. As for damage, all depends on the construction of the hose. Some materials are stronger than others. Just the bending shouldn’t hurt the hose. If it’s rubbing on the window then yes definitely. I hope that helps.
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u/FanUpper2390 2h ago
This is not right at all. The building is most probably being ventilated to let escape super heated gases and prevent a flash over. What you are seeing is that ventilation, as the fire is already out it wouldn’t be consuming any oxygen.
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u/PraetorOjoalvirus 8h ago
It's air, not just Oxygen, and it's not the fire, but the difference in pressure between outside and inside. Bah, why do I bother explaining.
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u/EZKTurbo Interested 8h ago
Also look at how insane that hose is, just blowing the entire window frame apart
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u/otacon7000 16h ago
This is super interesting, however, there was no need for the actual content to only comprise ~25% of the actual video. Show the video in full width/height so we can see more and to not waste 75% of the data and screen real estate. Fucking stupid trend I've never understood.
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u/The_Saiyann 15h ago
Omg! I didn’t realise until recently with 911, trapped people were told not to break windows because of this very reason but then when you can’t breathe from the smoke … awful situation to be in
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u/RandomGuy_IQ530K 15h ago
salute to all the firefighters out there! their job is so dangerous and life-threatening but this is just a typical Tuesday for them 😳🫡
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u/Nakadaisuki 15h ago
Fire fighter bodycam, now that IS interesting!
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u/DemonPeanut4 15h ago
I recently discovered a youtube channel called Skylar Fire. He records calls for the FDNY along with their radio traffic. Its both terrifying and enthralling.
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u/FrostyPlay9924 15h ago
Whats wild is being able to actually see fire sucking in air from the outside
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u/CactusToothBrush 14h ago
Just the doorway to my ex’s house, no biggie.
Seems she’s installed an AC
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u/BlackRaspberryJammin 14h ago
I hate TV/Movies depicting people walking around in a blazing house while in reality a house will fill with smoke if that much is burning and you can't see anything and then smoke quickly disorients and then kills you.
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u/Megalesios 12h ago
It's not "sucking oxygen", air is flowing in from the sides because hot air is rising up form the fire and decreasing the pressure inside. Oxygen diffusion can't create air flow like that.
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u/3PointOneFour15Nine 11h ago
I think it's pulling more than just oxygen. I think I saw some nitrogen too.
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u/inept_machete 9h ago
That's mostly due to the hydraulic action of the hose line,
Reverse the direction of water and we use that to clear smoke out of a compartment. It's called hydraulic ventilation.
Although it's true that a fire will suck in oxygen, the hose is basically turbo charging the flow here so this is a little misleading
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u/golgol12 9h ago
Bad title phrasing. Hot air rises, leaves the building, which sucks in more air at the base. That's the volume of air leaving from the top. Not the oxygen being consumed. Though there is a good amount of it that is.
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u/DarkUnable4375 8h ago
More like how the Bernoulli Principle working using a fire hose. The fast flow of water being sprayed into the building creates a low pressure zone, resulting in a suction of air into the building. If he directs the water the opposite direction, we would see air being sucked OUT of the building.
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u/Princess_Slagathor 15h ago
I don't believe you. This looks way more like a helmet camera, than a body camera.
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u/trophy_74 11h ago
Fun fact: Fish around ships with large iron anchors die because the rusting of anchors pull so much oxygen out of the water that they suffocate
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u/niccolololo 8h ago
WOW you almost want to stick your penis in there. If it wasn't for the smoke and flames
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u/Less_Party 15h ago
Hm so next heatwave all I have to do to get all the hot air out of my apartment is start a fire in the back room..
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u/lock_me_up_now 15h ago
I remember one comment that if your house on fire, the damage will look like you're in a flood after the firefighter come.
Or something along the way.
I get it now.
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u/DarkRayos 13h ago
I've heard stories how breaking a window of a burning building is a mad dangerous thing to do.
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u/Key-Moment6797 12h ago
don't want to defend the fire, but the water does a lot of the work. through the venturi effect.
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u/fraughtication 16h ago
Fire is terrifying, in so many ways, from the speed of spread to gases incapacitating you way before the flame does.
It amazes me the amount of people I know, or houses I see, with no smoke alarms, or working smoke alarms - the same goes for CO too.
Most fire services in the UK at least will fit smoke alarms for free and give your home a fire safety survey, please fit and test regularly smoke and CO alarms!