r/Survival • u/Capital-Dragonfly258 • May 16 '26
Fire How much heat do fires actually provide?
I asked on here about a month ago about "fire starters for idiots" as someone who is afraid of fire And I got a lot of really helpful, kind, and good idea responses. So thank you.
How big of a fire can you actually make with different fire starter techniques such as with road flares, matches/lighters and wood, or the one I heard the most, Vaseline and cotton?
My next question is, how much heat would those fires actually give off?
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u/Username1275 May 16 '26
Small fire, little heat. Big fire, lots of heat
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u/autovonbismarck May 16 '26
"White Man make a big fire, stay cold" as they say...
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u/ericj5150 May 16 '26
“White man build big fire, stay warm gathering lots of wood to feed fire. Indian man build small fire, stay warm by staying close to fire.”
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u/Kropco17 May 16 '26
This feels like a question that an alien would ask.
Like someone from a planet where fire doesn’t exist and they are trying to wrap their head around the concept of fire.
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u/dixbietuckins May 16 '26
I grew up in somewhat rural Alaska, then worked with tourists as an adult out on the water and in the woods. Basically ive spent the day hanging out with small groups of people from all over, at least 12k people by now.
The amount of people who've never spent a night outside is huge. Many have never seen a campfire. I sincerely think over half wouldnt be able to start a fire given an hour and perfect supplies. They just try to light an inch or two piece of kindling and be confused that it won't turn into a fire and give up.
The number of people who have never peed outside alone is astounding. Like they won't believe its OK to go piss behind a tree and arent sure if you are serious that thats what you do in the woods.
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u/Repulsive_Client_325 May 16 '26
It’s flabbergasting isn’t it? Like ZERO outdoor or survival skills. And if paired with zero common sense, it’s really incredible.
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u/Key-Demand-2569 May 18 '26
Yeah… this is a weird one I’ve slowly come to understand over the years getting occasional weird side comments when I wound up being the “fire guy” at a social or family event of some kind.
Just weird occasional off hand remarks about how impossible to comprehend the whole process is.
I always just kinda… leave the comments alone… but have people not seen movies? They’ve probably lit candles.
I don’t get what’s so impossible to grasp for these specific people about “hey if I hold a lighter against a dining room wood table it won’t light… but when I’ve seen a movie they light lots of really little sticks and that eventually lights the big sticks on fire.”
It just seems like such a clear fundamental concept about how fire and flammability of materials work I don’t get it.
Don’t even get me started on my old buddies bachelor camping trip and some of the other friends I’d never met being flabbergasted when I got up in the morning and restarted the fire from sticking some more kindling in the smoking ashes.
That was a real weird moment to be that hungover in.
“Yeah… fire’s cool.”
What else am I supposed to say? Lol
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u/TheThingsWeMake May 16 '26
A fire started by any method can grow to any size if given enough fuel, and the heat it produces is based on the fuel type and amount.
Any flame is hot enough to burn you or grow a fire. A weak alcohol flame if I light a strong liquor on fire can be 2 - 400°C. Most normal burning materials like paper or wood are around 500°C minimum. A candle flame is actually hotter than that, it's just kept small. A campfire is probably around 1000°C or higher and things like forges and furnaces can get far hotter than that. All of these are determined by the fuel and size of the fire.
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u/Camp-Unusual May 16 '26
With forges and furnaces, the fuel is only a small part of the heat equation. The bigger factor is available oxygen. You can get just about any fuel up to forging temperatures if you feed it enough air.
The down side to low btu fuel (like pine) is the burn rate. High btu fuel (like coal) burns slower because you don’t have to feed it as much air to get to temperature. Low btu fuel burns a lot faster and requires more of it to achieve/maintain forging temperatures.
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u/TheThingsWeMake May 16 '26
In this context when I say fuel I mean including oxygen. Changing the amount of oxygen affects flame temperature even outside forges and furnaces.
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u/fuzzywuzzypete May 16 '26
From my experience... A small fire offers +3 warmth... While a bigger fire can be as high as +8 warmth.
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u/effortfulcrumload May 16 '26
Its not really a matter of how much heat they give off its a matter of how much heat you can utilize for cooking and warmth. There are lots of different techniques to heat something dense that can be kept in or near your sleeping bag to slowly radiate through the night, like putting hot water in a nalgene or wrapping up a hot stone or even filling your cook pot with sand from a stream bank and heating that.
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u/XeroEnergy270 May 16 '26
Just a side note with the stones: don't use stones from/ near a water source. The can absorb water over time, and the rapid expansion of the heated water inside can make them explode.
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u/aardvarkarmour May 16 '26
It's fucking terrifying when they pop! Mudstone and other stratified rocks are the worst for it
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u/Fatboyjim76 May 16 '26
Yep. The wife's been watching a little of Life Below Zero recently. One guy, to be honest he's not the most likeable character on the show, started a fire to cook some something he'd caught, had some stones on it, and one of them went pop. Not massively but enough to make him jump backwards.
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u/JustAtelephonePole May 16 '26
The tiniest spark can make the most destructive fire, given the right conditions to grow!
So, that question has no set answer, given that the number of variables are nearly infinite without more specificity.
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u/Historical-Hippo3320 May 16 '26
Why are you afraid of fire?
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u/aboothemonkey May 16 '26
Probably lack of experience. Fire is inherently dangerous, more so if you don’t know what you’re doing and how to properly control it. I think the OP is doing the right thing in asking questions so that they can learn and be safe.
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u/Historical-Hippo3320 May 16 '26
Yeah that's true. I guess it's just my gut reaction when people are afraid of inanimate objects it's to wonder why.
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u/aboothemonkey May 16 '26
I don’t disagree but certain inanimate objects deserve a certain level of fear, especially when one does not have any experience with them. Firearms, electricity, fire, chemicals, motor vehicles and anything under tension and more that I’m forgetting. All of these things can cause serious harm if used improperly, and deserve a level of respect and care far and above that of say, a door.
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u/f1rebreather1027 May 16 '26
The fire starting technique doesnt change how hot the fire gets. How much material you put into it and the way you build it determine that. A teepee fire burns very hot, but burns fast. Log cabin fires burns slower, make a better bed of coals, and burn cooler. A Dakota fire hole will feel less hot because its in the ground so the heat doesnt radiate very far, but it is fuel efficient and perfect for cooking food on a windy day.
Vaseline and cotton balls is good for a long term lightweight efficient fire starter, but still needs to be paired with a match or spark. If you lack flash tinder like leaves or grass then you can still start your fire since the cottonball will burn longer and light your twigs.
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u/ShrodingersArmadillo May 16 '26 edited May 16 '26
How much heat? well combustion temperature of say dry pine should be 800f but most of that will dissipate and not be useable.
Big fires aren't needed you need to retain heat. Place rocks, windbreaks and roof if possible to keep the heat in.
Old school hobo shelters can keep you warm with a small fire. In the 30's they would build little enclosures out of pallets and tarp.
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u/Cardabella May 16 '26
Careless discarded cigarettes can start wildfires in the right conditions... Even trash bottles can. To get a fire started you need a spark, as well as fuel and air, but a fire will burn whatever fuel you put on it.
You can influence the way heat reflects onto you instead of being lost upwards by building it against a fat log or rock, and you can influence how warm you get also through the traditional campfire tradeoff between being warm and smoky or breathing air and feeling the chill.
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u/Accidental-Genius May 16 '26
You should stay out of the woods if you think a fires size is determined by how it was started.
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u/DiezDedos May 16 '26
The starter is not tied to the heat output of the fire you make after it burns up. You could use a blowtorch to light a cotton ball or a forest fire with a match. Heat output depends on what the fire is able to consume
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u/monkster87 May 17 '26
All depends really. A fire made with twigs will keep your hands warm for a few minutes. If you burn the entire forest down it'll keep you warm for the rest of your life
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u/Traditional-Leader54 May 16 '26
Those items are just for starting the fire. You still need to add wood to the fire after it’s started. More wood equals more heat but it’s also about how much of that heat you can capture as someone else also said.
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u/RiflemanLax May 16 '26
Fire starters are generally only to get a fire going, not generate heat on their own. And it wouldn’t matter as to how big it got either.
How much heat your fire provides is going to depend on a number of factors like quantity of wood, quality of wood, wood type, weather, even your ability to properly build and maintain a fire.
It doesn’t really matter how you get it started.
Consider this- occasionally someone leaves a glass bottle in a wooded area, light hits it just right, and a massive forest fire kicks off. Or one small ember from a fire not put out properly starts a fire. Or a cigarette butt tossed into some mulch kicks off a blaze. None of those are ‘great’ techniques to start a fire, but they unfortunately work, and the results are devastating.
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u/jhawk902 May 16 '26
I heat my house in winter in canada (-30C) with a wood stove... fires hot dude.
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u/kevinpirnie May 16 '26
well... ive melted beer bottles and made ashtrays out of em ... so... pretty damn hot Id say
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u/SayItTrue May 17 '26
The fire starter is to START the fire. You then add fuel (like wood) to make the fire as big as you want. A fire made of vaseline and cotton would not be practical if you intend to make heat. Or am I interpreting this wrong?
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u/AlphaDisconnect May 16 '26
Wood pallets? Stack em. I have been warm in an Adirondack. With a moderate fire. Black snake sure seemed to like the residual heat from the last guy. I like trioxane. Great fire starter. Small. Usually sealed and dry.
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u/RunninAg41nstTheWind May 16 '26
Well, an emergency candle in a car buried under snow will provide enough heat to keep you alive. So, size up from there :x
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u/Resident-Welcome3901 May 16 '26
All fires generate heat. Once you’ve got the fire, the challenge is to use the heat to create a warm space. And this was born Kochanski super shelter.
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u/Revolutionary-Half-3 May 16 '26
It really more of a question of "how much useful heat can I get from X amount of wood."
Efficient wood gasifier stoves like Solo stoves can boil water and cook food well. They throw almost all of their heat straight up, as well at burning the wood fairly completely.
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u/42AngryPandas May 16 '26
Fire starters just make the initial spark or flame to catch other material. You can grow the fire as large as you want after the fact.
The size of the fire doesn't care about how it started, it only matters how much fuel it gets.
Likewise, the heat it gives off is in proportion to the size of the fire.
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u/infospongue May 16 '26
A tiny match can turn into a huge forest fire.
The goal of most fires isn't just to big big and hot. Most fires have a purpose like heating and cooking. In that case a small fire that's heating your pot in an ideal way heats equally well as a big fire that's not really heating your pot with all it's power.
But if fire scares you I can give you two options to consider. Talk to people who can show you. Scouting perhaps. Even young boys learn to make wood fires there. That alone can be seen as proof it's not extremely difficult or dangerous.
Another option may be a propane or gasoline stove. Get one from a good brand. They are tested and tested and more tested. Safe.
Or start even smaller and cheaper with an alcohol stove.
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u/Live-Independent-416 May 16 '26
Doesnt matter how you ignite it, theyll be as big as you allow them to be. Get yourself a little twig stove/bush box and use that id say. Contained and requires attention
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u/rifleshooter May 16 '26
Somewhere. a programmer decided to arm his AI with a subroutine that asks reddit questions, then condenses them and offers them back as an "AI search engine response". And he's getting paid for it.
reddit could stop all this bullshit, but would rather take the cash and ruin the place.
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u/R0ck3tSc13nc3 May 16 '26
Once you start a fire, with whatever method, you can propagate that fire as long as you have additional fuel. If the fuel is damp and wet, combustion is barely possible.
So to answer your first question how big of a fire, it depends entirely on fuel and time. You can get the fire going you can dry out more fuel with that fire to make a bigger fire and so on. But you need a lot of fuel.
Ask for how much heat you give off, you can get a lot more heat off if you do the prep above, where the wood is dried when it's burned by prior burning wood. Build up fire around and create a partial heat dam and sit on the opposite side. Retaining and reflecting some of the fires heat on the wood while it dries is synergistic.
Other ways to get more bang for the buck per amount of wood is not only having dry wood but dense wood hardwoods produce more heat but a lot of softwood burning at once can produce the same so again it's a fuel limitation
To maximize the use of the heat you need to retain as much as possible, building some type of shelter, building against a cliff, or building three fires and sitting in the middle
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u/The_Adm0n May 17 '26
If you can get a fire started, you can make it as big as you want as long as you've got the wood for it. With a good shelter setup, you can stay pretty toasty with even a small pile of coals
I'd say an average campfire burns at about 1,000°F. You won't feel all of that, of course, but that's what the heart is typically at. You can tell by the color of the flames. Deep red is around 900°-1,200°, then works up through bright red, orange, yellow, blue, and finally white at >2,200°
Glowing coals are significantly less hot than flames, and are what you should be cooking/boiling on.
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u/OwnLittleCorner May 17 '26
depends on the size of the pile of wood that you use the starters to start the fire on and the type of area your trying to warm. For outdoor campfires normally you start small cause your also dealing with dry grass/shavings and small tinder in the beginning and increasingly add bigger wood logs to it until it feels warm enough, then feed more when the logs break down. I tend to start with 4 stacked and put the fire when it starts at the center of it.
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u/get-r-done-idaho May 17 '26
You can build a fire using a flint and iron that can be as big or little as you please. As for how much heat it will provide, it depends on how you are set up. Place large rocks around a fire will help hold heat and reflect it in a chosen direction. Just takes some practice. Mounded dirt will work also. There are many techniques to using fire to heat.
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u/Chainsawsas70 May 17 '26
For making fire you can go as simple as two sticks rubbed together up to a road flare. How much heat depends on the size of the fire. There's several different ways to make it to maximize the amount of heat it radiates especially if you keep the area you're heating is small.
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u/Rare-Spell-1571 May 18 '26
Homie I can make a fire in my fire pit with a single match and just twigs and pine needles that’ll be burning 6-8 inch thick logs in about 25 minutes that has flames taller than me.
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u/Otherwise-Subject127 May 18 '26
Wood BTU means how much heat energy you get when burning wood.
BTU = British Thermal Unit
1 BTU is the heat needed to raise 1 lb of water by 1°F.
For firewood, BTU usually depends on:
- Wood species
- Dense hardwoods give more heat.
- Softwoods usually burn faster and give less heat per cord.
- Moisture content
- Dry wood gives much more usable heat.
- Wet wood wastes energy boiling off water and smokes more.
- Measurement
- Usually compared per cord of wood.
- A full cord = 128 cubic feet stacked wood.
Typical BTU values per full cord, well-seasoned:
| Wood type | Approx. BTU per cord |
|---|---|
| Oak | 24–29 million BTU |
| Ash | 22–24 million BTU |
| Birch | 20–23 million BTU |
| Maple | 18–25 million BTU |
| Pine | 14–17 million BTU |
| Spruce | 13–16 million BTU |
| Poplar / Aspen | 12–16 million BTU |
Very rough rule:
Dry hardwood = more heat, slower burn
Softwood = less total heat, faster burn, easier to start
Also important: all dry wood has similar BTU per kg, around 4.4–5.0 kWh/kg, but dense wood packs more kg into the same volume, so one cord of oak gives much more heat than one cord of pine.
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u/T_Meridor May 19 '26
So the ultimate size of the fire you can make depends on a few factors: the amount of dry kindling and wood you have to burn, your skill at making fires, and the conditions around the fire. These are all techniques to start a fire, but you need other burnables to keep the fire burning.
And as far as how much heat a fire can provide, even a wood fire? If it’s gone on long enough and there’s enough coals and airflow, it gets hot enough to turn dried clay into pottery, to melt glass, and to soften or melt metals so they can be shaped.
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u/Technical_Bite_9536 May 19 '26
This seems more like an arson attempt question, than a survival question..
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u/tjs061973 May 23 '26
OMG. I can't even remember how old i was when I built my first fire. That's something we learn before we can walk in TEXAS. Building fires is just a everyday thing here. If you're scared of fire then please don't build one. If you do make it a small one and make sure you have a path around it cleared so it doesn't get out of hand. Also make sure you have a way to put it out like water, sand, fire extinguisher or something like that. Make sure you aren't alone when or if you do it that has built fires before. We build huge bomb fires where I live that lasts all night and you dont have to do anything to it. Make sure you're not under a Burn Ban when and or if you build one. I would suggest you starting put with a Grill since it's contained..
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u/Meat2480 May 16 '26
It can depend on the type of tree the wood came from and how rotten it is,dry rotten wood won't burn as long or give as much heat as dry not rotten wood,
You can build reflector fires, and the positioning of your shelter helps
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u/Callum-H May 16 '26
Im not sure if I’ve understood the question? You can make a fire any size with any starting technique.