Can a fireball (or multiple fireballs) set a forest on fire? Why or why not?
Provided it hasn't rain in several days, yes.
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Only if the forest is particularly dry and vulnerable to fire.
A fireball spell generates a searing explosion of flame that detonates with a low roar and deals 1d6 points of fire damage per caster level (maximum 10d6) to every creature within the area. Unattended objects also take this damage. The explosion creates almost no pressure.
<intermediate stuff left out>
The fireball sets fire to combustibles and damages objects in the area.
Remember that objects take half damage from energy attacks.
That said, it's up to the GM. Since the fireball creates almost no pressure, it doesn't throw things around, so the fuel might be limited. It's actually hard to get a forest fire started unless conditions are right. Not enough undergrowth and the fire dies before it dries out the standing trees enough to sustain itself. Too much wind and the fire tends to blow out. Not enough and it doesn't spread very fast and smoulders or runs out of fuel.
Can a fireball (or multiple fireballs) set a forest on fire? Why or why not?
Fireball: "The fireball sets fire to combustibles and damages objects in the area."
Not in glossary, so Mirriam-Webster says combustible: "1: capable of combustion"
combustion: "1: an act or instance of burning"
Forest Fires: "Most campfire sparks ignite nothing, but if conditions are dry, winds are strong, or the forest floor is dried out and flammable, a forest fire can result. Lightning strikes often set trees ablaze and start forest fires in this way."
So it sounds like it's certainly possible for a fireball to start a forest fire, though it's probably not going to happen every time.
What about other instantaneous fire spells?
Do you mean like Scorching Ray or Lightning Bolt ?
Lightning Bolt has a similar line to Fireball.
"The lightning bolt sets fire to combustibles and damages objects in its path."
Natural Lightning can start forest fires, but again, only when conditions are right or every thunderstorm would result in the forest burning down.
Scorching Ray has no such line.
Do you mean like Scorching Ray or Lightning Bolt ?
Lightning bolt is not a fire spell, but yes, I suppose.
Also, burning hands, flaming sphere (whose damage appears instantaneous even though the spell is not), fire snake, and others like them.
Burning Hands states "Flammable materials burn if the flames touch them. A character can extinguish burning items as a full-round action."
The question will always come back to the GM. How flammable is the forest ? It's not a binary question.
We're back to the FWI (Forest Fire Weather Index).
If it's Low or Medium, the fire will either self-extinguish or smolder or be a "gentle surface fire". When the FWI is high, you get a "moderately vigorous" fire. When very high or extreme that you get hollywood "Smokejumper" movie forest fires.
My source for descriptions
(edit: If I could spell, I'd be dangerous)
EDIT2: If I had to adjudicate on the fly, I'd give the forest a saving throw. On a 1, then I'd worry about it. Otherwise, things smolder a bit and go out.
EDIT3: When you intentionally start a campfire using flint and steel, the spark you get is basically instantaneous. You can only really start tinder. You use the burning tinder and some carefully applied blown breath to start kindling and use that to start larger and larger fuel until you have a self-sustaining fire.
yes
(unless the trees/ground/leaves are saturated with moisture)
yes
(unless the trees/ground/leaves are saturated with moisture)
Let me explain.....
I dont know from a physics POV how you could have a wavefront of fire, that somehow instantaneously kill someone, not have enough energy to set combustable materials on fire.
No physics, it's magic. Maybe it's superheated steam that scorches. It does what the spell description says it does.
yes
(unless the trees/ground/leaves are saturated with moisture)
Let me explain.....
I dont know from a physics POV how you could have a wavefront of fire, that somehow instantaneously kill someone, not have enough energy to set combustable materials on fire.
Becouse of "instantaneously".
In order to a combustible be set on fire, you need to increase the combustible temperature over it's combustion point. This is so, becouse solids and liquids can't combust. Only gas can combust. Solids and liquids that came near to it's combustion point, start to liberate combustible vapors, which is what burns when mixed with oxygen.
So a heavy wavefront of fire can be high enough to kill someone (breathing fire is instantanously dangerous for human being , without being high enough to make combustable material set on fire. This depends, essentially, on the amount of oxigen in the air (higher altitude, lower oxigen), and the combustable material flash point. Dry leaves have a low flash point (ie: they set on fire easy), but wet wood have higher flash points.
yes
(unless the trees/ground/leaves are saturated with moisture)
Let me explain.....
I dont know from a physics POV how you could have a wavefront of fire, that somehow instantaneously kill someone, not have enough energy to set combustable materials on fire.
Becouse of "instantaneously".
In order to a combustible be set on fire, you need to increase the combustible temperature over it's combustion point. This is so, becouse solids and liquids can't combust. Only gas can combust. Solids and liquids that came near to it's combustion point, start to liberate combustible vapors, which is what burns when mixed with oxygen.
So a heavy wavefront of fire can be high enough to kill someone (breathing fire is instantanously dangerous for human being , without being high enough to make combustable material set on fire. This depends, essentially, on the amount of oxigen in the air (higher altitude, lower oxigen), and the combustable material flash point. Dry leaves have a low flash point (ie: they set on fire easy), but wet wood have higher flash points.
Regardless of that, the spell descriptions for several instantaneous spells indicate they DO in fact set combustable objects on fire. If the forest could be set ablaze (relatively dry) fireball, burning hands, lightning bolt all should set it on fire.
yes
(unless the trees/ground/leaves are saturated with moisture)
Let me explain.....
I dont know from a physics POV how you could have a wavefront of fire, that somehow instantaneously kill someone, not have enough energy to set combustable materials on fire.
Becouse of "instantaneously".
In order to a combustible be set on fire, you need to increase the combustible temperature over it's combustion point. This is so, becouse solids and liquids can't combust. Only gas can combust. Solids and liquids that came near to it's combustion point, start to liberate combustible vapors, which is what burns when mixed with oxygen.
So a heavy wavefront of fire can be high enough to kill someone (breathing fire is instantanously dangerous for human being , without being high enough to make combustable material set on fire. This depends, essentially, on the amount of oxigen in the air (higher altitude, lower oxigen), and the combustable material flash point. Dry leaves have a low flash point (ie: they set on fire easy), but wet wood have higher flash points.
So how does an instantaneous pulse of energy (fireball) kill? Then explain how it does not do that to something that has less water content?
[not that it matters to much, just debating a point]
So how does an instantaneous pulse of energy (fireball) kill? Then explain how it does not do that to something that has less water content?
[not that it matters to much, just debating a point]
Breathing fire is mortal. The tissue in the lungs get damaged fairly easy if you breath fire or heated air. Also, in regular, real world waves of fire, the pressure from the explosion can be mortal as well (does not work for fireballs, as the spell says there is no pressure with the fireball). Lastly, the flash point (the temperature where a combustible ignites from a external ignition source) and the fire point (the temperature where a combustible is able to mantain combustion without external ignition source) aren't the same.
Plus, having more or less water content is not directly related to the flashpoint, the fire point, or the autoignition point. Granite rock has less water content that paper, and a much much much much higher flash point.
So how does an instantaneous pulse of energy (fireball) kill? Then explain how it does not do that to something that has less water content?
[not that it matters to much, just debating a point]
Breathing fire is mortal. The tissue in the lungs get damaged fairly easy if you breath fire or heated air. Also, in regular, real world waves of fire, the pressure from the explosion can be mortal as well (does not work for fireballs, as the spell says there is no pressure with the fireball). Lastly, the flash point (the temperature where a combustible ignites from a external ignition source) and the fire point (the temperature where a combustible is able to mantain combustion without external ignition source) aren't the same.
Plus, having more or less water content is not directly related to the flashpoint, the fire point, or the autoignition point. Granite rock has less water content that paper, and a much much much much higher flash point.
real world.....
I once was doing a chemistry magic show that went wrong. I got a flash burn that did 2nd degree burns, mostly the left side of the face and ear.....
if i had inhaled the "flash" or whatever you would call that, i could have been seriously hurt.
But
My hair was smoking, my clothes had burn holes, my leather shoes were scorched.....
I dont see how that would not start a fire in a forest.... especually with a lot of lief liter....
(kids wanted me to do it again...)
:)
In the dry seasons out west all it takes is a cigarette. In many cases. I think that almost any fire spell constitutes more fire than a lit cigarette. So I think that a larger hotter more sustained spell is likely to have a larger spot of origin. The level of mosture is going to effect how fast it spreads or even if there is enough water in the plants and such the fire will gradually decrease in heat and energy and thus weaker and start to die out. I would suggest that a fireball is very likely to start a forrest fire if it happens to be in the dry season that is going to be very bad.
Other sources of forest fires include lightening strikes so lightening bolt has a great chance of doing this (hence it is in the rules).
real world.....
I once was doing a chemistry magic show that went wrong. I got a flash burn that did 2nd degree burns, mostly the left side of the face and ear.....
if i had inhaled the "flash" or whatever you would call that, i could have been seriously hurt.
But
My hair was smoking, my clothes had burn holes, my leather shoes were scorched.....I dont see how that would not start a fire in a forest.... especually with a lot of lief liter....
(kids wanted me to do it again...)
:)
That wouldn't start a fire in a forest, for the same reason it didn't start a fire in your clothes or your hair ;)
Because achieving the flash point (where your clothes get burn holes and your hair smokes) is not the same that achieving the fire point (were your clothes burn, and keep burning, and your hair is set on flames, and keep flaming). Flash point is when you get to the point an ignition is made, through an external ignition source, and fire point is when you get to the point when a *sustained* combustion can be kept without further use of an external ignition source.
Dry leaves have a lower ingnition point than clothes, but fresh leaves do not. This is an easy experiment (less dangerous than your own :P). Take a T-shirt. Take a bunch of fresh leaves. Take a lighter, and put a flame near one of them. Count the time until you see *flames*, so when you pull the lighter off, the item keeps burning. You'll see the cloth will probably burn faster.
In the dry seasons out west all it takes is a cigarette. In many cases. I think that almost any fire spell constitutes more fire than a lit cigarette. So I think that a larger hotter more sustained spell is likely to have a larger spot of origin.
The key word is sustained. What makes things burn, is *temperature*. A sustained flame, even a cigarrette, can slowly increase the temperature of an item (such as leaves). A fast, exploding wave of fire might not have the same effect.
Again, an easy experiment. Take a bunch of paper. take a lighter, like a Zippo. Now, quickly pass the flame of the zippo near the paper, in conctact with it. It won't burn. Now take a cigarrette. Pass it near the paper, in contact with it, quickly. Nothing happens either. Now, *leave* the cigarrette in contact with the paper. Wait a minute or two. See what happens?
You don't even need a flame. A Magnifying glass is enough to make paper, or dry leaves, to burn, given time. An instant explosion, however, is not the same. It's perfectly possible to detonate dynamite in a forest, and not get a forest fire, while a magnifying glass can. And dynamite explosions have much higher tempereature and fire than a magnifying glass...
About lightning bolts, a lightning temperature is higher than the surface of the Sun!!!. Even then, not always a lightning strikes a tree, it starts a fire. Same principle: very high heat, but very small amount of time (fractions of miliseconds). If the tree is dry enough, it'll burn. In spring... probably won't. How many forest fires have you seen produced by a storm in march?